Also called myocyte myodynia myofibril myofibrosis myogenic myoglobin myoglobinuria myogram myograph myography myokymia myology myoma myomectomy myometritis myometrium / maI mi trim/ noun the muscular tissue in the uterus myoneural / maI njrl/ adjective relating to or involving both the muscles and the nerves myoneural junction / maInjrl d kn/ noun same as neuromuscular myometrium myoneural myoneural junction metritis myositis / maI saItIs/ noun inflammation and degeneration of a muscle myotatic / maI t tIk/ adjective referring to the sense of touch in a muscle myotatic reflex / maIt tIk ri fleks/ noun a reflex action in a muscle which contracts after being stretched myotic /maI tIk/ noun a drug which causes the pupil of the eye to contract myotomy /maI tmi/ noun a surgical operation to cut a muscle myotonia / maI tni/ noun difficulty in relaxing a muscle after exercise myotonic / maI tnIk/ adjective referring to tone in a muscle myotonic dystrophy / maItnIk dIstrfi/ noun a hereditary disease with muscle stiffness leading to atrophy of the muscles of the face and neck myotonus /maI tns/ noun a muscle tone myringa /mI rI / noun same as eardrum myringitis / mIrIn d aItIs/ noun inflammation of the eardrum myringoplasty /mI rI pl sti/ noun the surgical repair of a perforated eardrum arteria ileocolica discount torsemide 20 mg with amex. Also called tympanoplasty myringotome /mI rI tm/ noun a sharp knife used in myringotomy myringotomy / mIrI tmi/ noun a surgical operation to make an opening in the eardrum to allow fluid to escape myx- /mIks/ pre hypertension vs hypertension purchase torsemide 10mg free shipping, myxo- /mIks/ prefix referring to mucus myxoedema / mIks di m/ noun a condition caused when the thyroid gland does not produce enough thyroid hormone zytiga arrhythmia generic 20mg torsemide fast delivery. The person blood pressure 7030 generic 10 mg torsemide fast delivery, often a middle-aged woman blood pressure chart adolescent buy torsemide 20mg lowest price, becomes overweight best blood pressure medication kidney disease cheap torsemide 20mg line, moves slowly and develops coarse skin. Opposite longmyopathy myopia junction objects clearly, but not objects which are further away. Also called shortsighted myoplasm / maIpl zm/ noun same as myoplasm sightedness myopic /maI pIk/ adjective able to see close myopic sarcoplasm which develops at the base of a fingernail or toenail myxoma /mIk sm/ noun a benign tumour of mucous tissue, usually found in subcutaneous tissue of the limbs and neck myxosarcoma / mIkss km/ noun a malignant tumour of mucous tissue myxovirus / mIks vaIrs/ noun any virus which has an affinity for the mucoprotein receptors in red blood cells. Symbol n nanometre / n nmit/ noun a unit of measurement of length equal to one thousand millionth of a metre. Symbol nm nanomole / n nml/ noun a unit of measurement of the amount of a substance equal to one thousand millionth of a mole. Symbol nmol nanosecond / n n seknd/ noun a unit of measurement of time equal to one thousand millionth of a second. Naseptin /n septIn/ a trade name for a mixture containing chlorhexidine and neomycin, used to treat nasal infection by organisms such as staphylococci nasion / neIzin/ noun the place at which the bridge of the nose meets the forehead naso- /neIz/ prefix referring to the nose nasogastric / neIz strIk/ adjective referring to the nose and stomach nasogastrically / neIz strIkli/ adverb referring to a method of feeding someone via a tube passed through the nose into the stomach nascent Naseptin nasion nasonasogastric nasogastrically narcoleptic / n k leptIk/ adjective 1. The main narcotics are barbiturates, cocaine and opium, and drugs derived from opium, such as morphine, codeine and heroin. Addictive narcotics are widely used for the relief of pain in terminally ill patients. Also called turbinate bones nasal congestion / neIzl kn d estn/ noun the blocking of the nose by inflammation as a response to a cold or other infection nasal drops / neIzl drps/ plural noun drops of liquid inserted into the nose nasal septum / neIzl septm/ noun a wall of cartilage between the two nostrils and the two parts of the nasal cavity nasal spray / neIzl spreI/ noun a spray of liquid into the nose nasal bone nasal cartilage nasal cavity nasal conchae nasal congestion nasal drops nasal septum nasal spray noun a tube passed through the nose into the stomach nasolacrimal / neIz l krIml/ adjective referring to the nose and the tear glands nasolacrimal duct / neIz l krIml d kt/ noun a duct which drains tears from the lacrimal sac into the nose nasopharyngeal / neIz f rIn d i l/ adjective referring to the nasopharynx nasopharyngitis / neIz f rIn d aItIs/ noun inflammation of the mucous membrane of the nasal part of the pharynx nasopharynx / neIz f rIks/ noun the top part of the pharynx which connects with the nose nasosinusitis / neIz saIn saItIs/ noun a condition in which the nose and sinuses swell up nasty / n sti/ adjective unpleasant this medicine has a nasty taste. Other causes include stomach disorders, such as gastritis, ulcers and liver infections. Nausea is commonly experienced by women in the early stages of pregnancy, and is called morning sickness. Opposite positive negative feedback / ne tIv fi db k/ noun a situation in which the result of a process represses the process which caused it negativism / ne tIvIzm/ noun the attitude of a person who opposes advice or instructions needling needs assessment needs deprivation negative negative feedback negativism collar to support the head of a person with neck injuries or a condition such as cervical spondylosis necro- /nekr/ prefix referring to death necrobiosis / nekrbaI sIs/ noun 1. Many organs pass through the neck, including the oesophagus, the larynx and the arteries and veins which connect the brain to the bloodstream. Motor nerves or efferent nerves take messages between the central nervous system and muscles, making the muscles move. Sensory nerves or afferent nerves transmit impulses such as sight or pain from the sense organs to the brain. Also called myoneural junction neuromyelitis optica / njrmaIlaItIs ptIk/ noun a condition, similar to multiple sclerosis, in which a person has acute myelitis and the optic nerve is also affected. Also called nerve cell neuropathic bladder / njrp ik bl d/ noun a condition in which the bladder neuron neuropathic bladder neurotically /nj rtIkli/ adverb in a neurotic way She is neurotically obsessed with keeping herself clean. Other neurotransmitters such as gamma aminobutyric acid, glutamine and substance P are less common. Also called polyneurotrophic neurotropic neuter neutral neutralise neutropenia neutrophil morph newborn / nju b n/ adjective born recently. Symbol N newton nipple or persons who are most closely related to someone the hospital has notified the next of kin of the death of the accident victim. Also called nicotinism nicotine receptor / nIkti n rI sept/ noun a cholinergic receptor found at the neuromuscular junction on skeletal muscle and in the autonomic ganglia, which responds to nicotine and nicotine-like drugs. Also called implantation nicotine poisoning nictation /nIk teIn/, nictitation /nIktI teIn/ noun the act of winking nidation /naI deIn/ noun 1. Signs in babies include feeding difficulties, a large abdomen within 3 to 6 months, and progressive loss of early motor skills. Nightingale ward noun an old-fashioned type of long ward with a row of beds along each wall and a centrally placed point for the nurse in charge to work from nightmare / naItme/ noun a dream which frightens the dreamer the child had a nightmare and woke up screaming. Opposite noctnoctambulation nocte Nissl granule / nIsl r nju l/, Nissl body / nIsl bdi/ noun one of the coarse granules surrounding the nucleus in the cytoplasm of nerve cells. When the intake of nitrogen and the excretion rate are equal, the body is in nitrogen balance or protein balance. Also called bedwetting nodal / ndl/ adjective referring to nodes nodal tachycardia / ndl t ki k di/ noun a sudden attack of rapid heartbeats. Also called non-urgent surgery non-granular leucocyte / nn r njl lu ksaIt/ noun a leucocyte which has no granules. Also called epistaxis noso- /ns/ prefix disease nosocomial / ns kmil/ adjective referring to hospitals nosocomial infection / ns kmil In fekn/ noun an infection which is passed on to a person being treated in a hospital nosology /n sld i/ noun the classification of diseases nostril / nstrIl/ noun one of the two passages in the nose through which air is breathed in or out His right nostril is blocked. It leads into two passages, the nostrils, which in turn lead to the nasal cavity, divided in two by the septum. The nasal passages connect with the sinuses, with the ears through the Eustachian tubes, and with the pharynx. Compare subjective obligate / blI eIt/ adjective referring to an organism which exists and develops in only one way. It is sometimes due to glandular disorders, but it is usually caused by eating or drinking too much. The oesophagus olecranon / lekrnn/, olecranon process / lekrnn prss/ noun a curved projecting part at the end of the ulna at the elbow, which gives rise to a painful tingling sensation if hit by accident. Full form omni mane -oma /m/ suffix tumour oligo-ovulation oligospermia oliguria olive -ology -olol o. The symptoms are high fever, inflammation of the lymph nodes and excruciating pains in the joints. Also called chronic glaucoma open fracture / pn fr kt/ noun same as compound fracture open-heart surgery / pn h t s d ri/ noun surgery to repair part of the heart or one of the coronary arteries performed while the heart has been bypassed and the blood is circulated by a pump opening / pnI/ noun a place where something opens open visiting / pn vIzItI/ noun an arrangement in a hospital by which visitors can enter the wards at any time operable / prbl/ adjective referring to a condition which can be treated by a surgical operation the cancer is still operable. The doctor asked the consultant for his opinion as to the best method of treatment. Also called -opia opiate opinion opioid opisthoopisthotonos opium opponens opportunist opposition opsonic index opsonin optic optical optical fibre optical illusion optic chiasma optic disc cranial nerve which transmits the sensation of sight from the eye to the brain. Also called spiorganism organoorgan of Corti cal operation to place an undescended testis in the scrotum. It is used in the testing of electronic equipment and in measuring electrical impulses of the heart or the brain. The three bones are articulated together; the stapes is attached to the membrane of the oval window, the malleus to 281 the eardrum, and the incus lies between the other two. Also called osteogenesis ossium / sim/ fragilitas ossium ost- /st/ prefix same as osteo- (used before vowels) ostectomy / stektmi/ noun a surgical opossification ossium ostostectomy osteitis osteoplasty fracture or refracture bone to correct a deformity osteoclast / stikl st/ noun 1. Also called brittle bone disease osteogenic / sti d enIk/ adjective made of or originating in bone tissue osteology / sti ld i/ noun the study of bones and their structure osteolysis / sti lsIs/ noun 1. Also called marble bone disease osteophony / sti fni/ noun the conduction of sound by bone, as occurs in the ear. Also called bone conduction osteophyte / stifaIt/ noun a bony growth osteoplastic necrotomy / stipl stIk nek rtmi/ noun a surgical operation to remove a piece of dead bone tissue osteoplasty / stipl sti/ noun plastic surgery on bones osteophony osteophyte osteoplastic necrotomy osteoplasty plural is osteopathies. Hormone replacement therapy is the most effective method of preventing osteoporosis though there are other risks to health from long-term use. Also called labyotitis otitis externa otitis interna over-the-counter drug otic / tIk/ adjective referring to the ear otic ganglion / tIk lin/ noun a otic otic ganglion rinthitis otitis media / taItIs mi di/ noun an infection of the middle ear, usually accompanied by headaches and fever. Also called middle otitis media ear infection, tympanitis oto- /t/ prefix ear otolaryngologist / tl rI ld Ist/ noun a doctor who specialises in treatment of diseases of the ear and throat otolaryngology / tl rI ld i/ noun the study of diseases of the ear and throat otootolaryngologist otolaryngology otospongiosis / t sp nd i sIs/ noun the formation of spongy bone in the labyrinth of the ear which occurs in otosclerosis Otosporin / tsprIn/ a trade name for ear drops containing hydrocortisone, neomycin and polymyxin ototoxic / t tksIk/ adjective referring to a drug or an effect which is damaging to organs or nerves involved in hearing or balance outbreak / atbreIk/ noun a series of cases of a disease which starts suddenly There was an outbreak of typhoid fever or a typhoid outbreak. Also ovary overproduction / vpr d kn/ noun the act of producing too much of something the condition is caused by overproduction of thyroxine by the thyroid gland. It is essential to healthy metabolism and given to patients with breathing difficulties. Also called turoximeter oxybutynin oxycephalic oxycephaly Carbon compounds form oxides when metabolised with oxygen in the body, producing carbon dioxide. Even in lower concentrations it irritates the throat, makes people cough and gives headaches and asthma attacks similar to hay fever. Also called haematocrit packing / p kI/ noun absorbent material put into a wound or part of the body to absorb fluids pack up / p k p/ verb to stop working (informal) His heart simply packed up under the strain. From the site it travels up the spinal column to the medulla and through a series of neurones which use Substance P as the neurotransmitter to the sensory cortex. Pain is the method by which a person knows that part of the body is damaged or infected, though the pain is not always felt in the affected part. Also called staphylorrhaphy, uraniscorpalatopharyngeal arch palatoplasty palatoplegia palatorrhaphy rhaphy pale /peIl/ adjective light coloured or white pale After her illness she looked pale and tired. For example, a painkiller can reduce the pain in a tooth, but will not cure the caries which causes the pain. This hormone is secreted into the bloodstream by the islets of Langerhans which are in the pancreas. Also called Pap test [Described panproctocolectomy pant pantpantopantothenic acid pantotropic Papanicolaou test papulopustular paraguard stretcher papulopustular / p pjl p stjl/ adjective referring to a rash with both papules and pustules papulosquamous / p pjl skweIms/ adjective referring to a rash with papules and a scaly skin para- /p r/ prefix 1. Also called endemic haemoptysis paragraphia / p r r fi/ noun the writing of different words or letters from the ones intended, as a result of a stroke or disease paraguard stretcher / p r d stret/ noun a type of strong stretcher to which the injured person is attached securely, so that he or she can be carried upright. It is used for rescuparageusia paragonimiasis paragraphia paraguard stretcher para-influenza virus 290 parametritis / p rmI traItIs/ noun inflammation of the parametrium parametrium / p r mi trim/ noun the connective tissue around the uterus paramnesia / p r m ni zi/ noun a disorder of the memory in which someone remembers events which have not happened paramyxovirus / p rmIks vaIrs/ noun one of a group of viruses, which cause mumps, measles and other infectious diseases paranasal / p r neIzl/ adjective by the side of the nose paranasal sinus / p rneIzl saIns/, paranasal air sinus / p rneIzl e saIns/ noun one of the four pairs of sinuses in the skull near the nose, which open into the nasal cavity and are lined with sticky mucus parametritis parametrium paramnesia paramyxovirus paranasal paranasal sinus ing people from mountains or from tall buildings. Its messages reach the organs of the body through the cranial and sacral nerves to the eyes, the gastrointestinal system and other organs. Many diseases such as malaria and amoebic dysentery are caused by infestation with parasites. The main symptoms are tremparietal lobe parietal pericardium parietal peritoneum parietal pleura -parin Paris parity parkinsonian Parkinsonism tion near the nail which forms pus, caused by an infection in the fleshy part of the tip of a finger. Some cases can be improved by treatment with levodopa, which is the precursor of the missing neurotransmitter dopamine, or by drugs which inhibit the breakdown of dopamine. Also called superpartial amnesia partial deafness partial denture partial gastrectomy partially partially sighted register partial mastectomy partial pancreatectomy partial thickness burn pass pasteurise ficial thickness burn partial vision / p l vI n/ noun the ability to see only a part of the total field of vision, or not being able to see anything very clearly particle / p tIkl/ noun a very small piece of matter particulate /p tIkjlt/ adjective 1. Also called kneecap patellar /p tel/ adjective referring to the kneecap patellar reflex /p tel ri fleks/ noun the jerk made as a reflex action by the knee, when the legs are crossed and the patellar tendon is tapped sharply. Also called knee jerk patellar tendon /p tel tendn/ noun a tendon just below the kneecap patellectomy / p t lektmi/ noun a surgical operation to remove the kneecap patency / peItnsi/ noun the condition of being wide open A salpingostomy was performed to restore the patency of the Fallopian tube. They are also used for treating nicotine addiction and can be bought without a prescription. Also called morbid anatomy pathology report /p ld i rI p t/ noun a report on tests carried out to find the cause of a disease pathophysiology / p fIzi ld i/ noun the study of unusual or diseased organs pathway / p weI/ noun a series of linked neurones along which nerve impulses travel -pathy /pi/ suffix 1. Also called shoulder girdle pectoralis / pekt reIlIs/ noun a chest muscle pectoralis major /pekt reIlIs meId / noun a large chest muscle which pulls the arm forward or rotates it pectoralis minor /pekt reIlIs maIn/ noun a small chest muscle which allows the shoulder to be depressed pectoral muscle / pektrl m sl/ noun one of two muscles which lie across the chest and control movements of the shoulder and arm. Also called chest muscle pectus / pekts/ noun the anterior part of the chest pectus carinatum / pekts k rI n tm/ noun a condition in which the sternum is unusually prominent. Also called pigeon breast pectus excavatum / pekts eksk veItm/ noun a congenital condition, in which the chest is depressed in the centre because the lower part of the breastbone is curved backwards. After Augusto Pelli- shaped pill of steroid hormone, usually either oestrogen or testosterone, that is implanted under the skin for slow absorption 2. The pelvic girdle is shaped in a different way in men and women, the internal space being wider in women. Seventy-five per cent (75%) of hospital cases remain in hospital for less than four days. Also called balloon angioplasty pepsin pepsinogen peptic peptic ulcer peptidase peptide peptone peptonuria per per cent percentage perception perceptive deafness percussion percutaneous percutaneous absorption percutaneous angioplasty per diem per diem 298 periarthritis / peri raItIs/ noun inflammation of the tissue round a joint pericard- /perik d/ prefix referring to the pericardium pericardectomy / perik dektmi/ noun the surgical removal of the pericardium pericardial / peri k dil/ adjective referring to the pericardium pericardial effusion / perik dil I fju n/ noun an excess of fluid which forms in the pericardial sac pericardial friction / perik dil frIkn/ noun the rubbing together of the two parts of the pericardium in pericarditis pericardial sac / perik dil s k/ noun the inner part of the pericardium forming a baglike structure or sac which contains fluid to prevent the two parts of the pericardium rubbing together pericardiectomy /perik di ektmi/ noun same as pericardectomy pericardiocentesis / peri k disen ti sIs/ noun the puncture of the pericardium to remove fluid pericardiorrhaphy / perik di rfi/ noun a surgical operation to repair a wound in the pericardium pericardiostomy / perik di stmi/ noun a surgical operation to open the pericardium through the thoracic wall to drain off fluid pericardiotomy / perik di tmi/ noun same as pericardotomy pericarditis / perik daItIs/ noun inflammation of the pericardium acute pericarditis a sudden attack of fever and pains in the chest, caused by the two parts of the pericardium rubbing together pericardium / peri k dim/ noun a membrane which surrounds and supports the heart pericardotomy / perik dtmi/ noun a surgical operation to open the pericardium perichondritis / perikn draItIs/ noun inflammation of cartilage, especially in the outer ear perichondrium / peri kndrim/ noun the fibrous connective tissue which covers cartilage pericolpitis / perikl paItIs/ noun inflammation of the connective tissue round the vagina. Also called paracolpitis pericranium / peri kreInim/ noun connective tissue which covers the surface of the skull pericystitis / perisi staItIs/ noun inflammation of the structures round the bladder, usually caused by infection in the uterus perifolliculitis / peri flIkju laItIs/ noun inflammation of the skin round hair follicles perihepatitis / perihep taItIs/ noun inflammation of the membrane round the liver perilymph / perilImf/ noun a fluid found in the labyrinth of the inner ear periarthritis pericardpericardectomy pericardial pericardial effusion pericardial friction pericardial sac pericardiectomy pericardiocentesis pericardiorrhaphy pericardiostomy pericardiotomy pericarditis pericardium pericardotomy perichondritis perichondrium pericolpitis pericranium pericystitis perifolliculitis perihepatitis perilymph percutaneous epididymal sperm aspiration / p kju teInis epIdIdIml sp m spIreIn/ noun the removal of sperm from the epididymis by withdrawing it through the skin, usually as part of fertility treatment. One of its effects is to stop the peristalsis of the intestine so making it impossible for a person to eat and digest. Also called permeable membrane pernicious pernicious anaemia members of staff can consult the personal records of the patients. Sweat contains salt, and in hot countries it may be necessary to take salt tablets to replace the salt lost through perspiration. Compare grand mal Petri dish / pi tri dI/ noun a small glass or plastic dish with a lid, in which a culture is grown petrissage / petrI s / noun an action used in massaging the muscles petrosal /p trsl/ adjective referring to the petrous part of the temporal bone petrositis / petr saItIs/ noun inflammation of the petrous part of the temporal bone petrous / petrs/ adjective 1. Also called carbolic phenazopyridine phenobarbitone phenol becomes the oesophagus when it reaches the sixth cervical vertebra. The pharynx is the channel both for air and food; the trachea (or windpipe) leads off it before it joins the oesophagus. The upper part of the pharynx (the nasopharynx) connects with the middle ear through the Eustachian tubes. When air pressure in the middle ear is not equal to that outside, as when going up or down in an aeroplane, the tube becomes blocked and pressure can be reduced by swallowing. Compare genphenomenon phenotype sential amino acid phenylketonuria / fi naIl ki t njri/ noun a hereditary condition which affects the way in which the body breaks down phenylalanine, which in turn concentrates toxic metabolites in the nervous system causing brain damage phenylketonuria otype `. An oncogene is a gene that encodes a protein that contributes to the malignant phenotype of the cell. The condition can be treated by giving the child a special diet but early diagnosis is essential to avoid brain damage. Also called venogram phlebography /flI b rfi/ noun an X-ray examination of a vein using a radio-opaque dye so that the vein will show up on the film. Also called sun blindness photosensitive / ft sensItIv/ adjective sensitive to light, or stimulated by light photosensitivity /ftsens tIvti/ noun the fact of being sensitive to light phototherapy /ft erpi/ noun a treatment for jaundice and vitamin D deficiency, which involves exposing the person to ultraviolet rays phototoxic / ft tksIk/ adjective making the skin unusually sensitive to damage by light, as in sunburn phototoxicity / fttk sIsIti/ noun a cause of damage to the retina of the eye due to exposure to too much ultraviolet light or radiphotopsia photoreceptor neurone photoretinitis photosensitive photosensitivity phototherapy phototoxic phototoxicity photuria 306 person. Symbol p picomole / pi kml/ noun a unit of measurement of the amount of substance equal to one million millionth of a mole. Placebos are also used on control groups in tests of new drugs (a placebo-controlled study). The placenta allows an exchange of oxygen and nutrients to be passed from the mother to the fetus to which she is linked by the umbilical cord.
Impacts to aquatic vegetation subsequently decrease food and habitat availability for other aquatic organisms heart attack 42 year old buy torsemide 10mg low cost. Excessive nutrients in shallow hypertension essential torsemide 10mg lowest price, wadeable streams can lead to dense mats of algal growth blood pressure medication that doesn't cause ed 10 mg torsemide free shipping, particularly filamentous algae (e arteria zygomatica generic torsemide 10mg otc. Such growths alter the habitat quality of the substrate and lead to predictable changes in aquatic macroinvertebrate populations hypertension portal torsemide 20mg sale. Proportions and abundances of various feeding guilds shift blood pressure psi generic 20mg torsemide with mastercard, changing food quality and availability for fish and other organisms. Elevated nutrient levels, in combination with elevated levels of fine-grained sedimentation, can foster the growth of aquatic macrophyte beds, particularly in stream pools (King and Ball 1964; Taylor and Roff 1986). Decomposition of excessive algal biomass reduces dissolved oxygen levels in surface waters, lessening the amount available to other aquatic organisms. In surface waters stratified by temperature and/or salinity gradients, the settling of large amounts of organic matter can create low oxygen or anoxic conditions in bottom waters and allow only a few pollution-tolerant species to persist in the benthic community. Large diurnal swings in surface water oxygen content have also been observed in some waters. Supersaturation of dissolved oxygen takes place during daylight hours when photosynthesis takes place. Eutrophication can also lead to shifts in fish community composition due to modifications of trophic feeding relationships. For example, the proportion of large, piscivorous fish species that rely on sight to catch their prey may decline in a surface water as water clarity falls. If eutrophication conditions are extreme, a fish community can be reduced to pollution-tolerant bottom feeders (e. Eutrophic conditions can also foster the growth of certain types of algal blooms with toxic effects on aquatic organisms and human beings. Brown or red tides are intense algal growths that can release neurotoxins into the water column, harming some forms of aquatic life. Toxic effects on aquatic organisms can cause population declines and localized extinctions (Burkholder 1998). These types of blooms usually require beach closings and temporary bans on seafood harvesting because consuming shellfish from affected waters can cause shellfish poisoning in humans (Burkholder 1998). Human exposure to marine algal neurotoxins has been associated with a range of neurobehavioral abnormalities and is an emerging area of study (Friedman and Levin 2005). Illnesses most frequently linked to neurophysiological disturbance are Amnesic Shellfish Poisoning, Ciguatera Fish Poisoning, and Possible Estuarine Associated Syndrome, which is associated with exposure to substances from the dinoflagellate Pfiesteria piscicida through the food chain. November 2009 3-9 Environmental Impact and Benefits Assessment for the C&D Category In freshwater systems, toxins from blue-green algal (Cyanophyta) species (e. Blue-green algae toxins are classified according to mode of action and include hepatotoxins (e. Increased levels of organic material from algal blooms can also increase concentrations of chlorination disinfection by-products, including haloacetic acids and trihalomethanes, in treated drinking water. Microcystins, in particular, have been associated with acute liver damage and possibly liver cancer in laboratory animals. Some algal blooms may not be directly harmful to humans but may still impair human use of aquatic resources. Increased levels of organic material associated with algal blooms can clog drinking water intakes and cause unpleasant tastes and odors in drinking water (Boyd 1990) (see Chapter 9). Excessive algae growths can reduce the attractiveness and viability of surface waters for a variety of recreational activities including swimming, boating, fishing, wildlife viewing, and other outings. Excessive growths can also clog screens on water intakes for irrigation, industrial use, and drinking water. Sedimentation levels also increase over the long term in eutrophic waterbodies, particularly lakes, reservoirs, and other impoundments with quieter flow conditions. Sediment cores obtained from studies of former lake environments have documented large increases in annual sediment deposits after the onset of eutrophication (Goldman and Horne 1994). These elevated sedimentation levels, acting in concert with sediment deposition from construction activities and streambed erosion due to land use change, can decrease depth and volume of surface waters over time. Algal growth also increases surface water turbidity, the various aquatic life and human resource impacts of which are discussed in Sections 2. The nitrogen compound ammonia can function as a nutrient, the impacts of which are discussed above. Ammonia is also toxic to many aquatic organisms at relatively low levels under certain water conditions. Ammonia toxicity typically increases with pH such that above pH levels of 9, the most toxic form (unionized ammonia) is the predominant fraction. Low dissolved oxygen levels found in the bottom waters of eutrophic waterbodies can increase the potential for ammonia toxicity, particularly when a surface water is stratified. The low redox conditions found in these waters favor the anaerobic microbial conversion of nitrite or nitrate to ammonia. Excessive nutrients (phosphorus, nitrogen) and its associated biological response. Nutrient levels associated with eutrophication vary among regions with the country due to differences in geology, climate, and soil types. This information reflects only the status of those waters that have been assessed. Appendix A provides information on the state water report year for which data were available for populating the table below as of September 17, 2009. It should be noted that individual waters may be impaired by more than one pollutant. Although states tend to target their monitoring efforts to those surface waters they believe to be impaired, the total area of impaired surface waters due to nutrients is probably underestimated due to the low percentage of surface waters that were assessed. Water quality in the United States has also been assessed through a series of national, probability-based surveys known as the National Aquatic Resource Surveys. According to the survey, 32 percent of streams have "poor" nitrogen conditions, and 21 percent have "fair" conditions relative to reference streams. Also, 31 percent have "poor" phosphorus conditions, and 16 percent have "fair" conditions relative to reference streams. The survey also examined the association between stressors and biological condition and found that high levels of nitrogen or phosphorus more than double the risk for poor biological condition (see Figure 3-1). Several threatened and endangered (T&E) species are vulnerable to eutrophication from nutrient pollution. One study postulated that 25 percent of all current freshwater T&E species are adversely impacted by eutrophication (Richter et al. Threatened fish species include the Waccamaw silverside (Menida extensa), paleback darter (Etheostoma pallididorsum), and an arctic grayling subspecies (Thymallus arcticus montanus) found in Montana and Wyoming (NatureServe Explorer 2009). Organic compounds are present on construction sites as natural soil constituents, components of a variety of building and equipment materials, and historic soil contamination. Given the proprietary nature of the composition of many commercially available products and the enormous variety of possible compounds in these materials, research in this area can be challenging. Pavement materials such as asphalt and petroleum-based asphalt pavement rejuvenators contain a variety of organic compounds. There are many concrete additives whose environmental effects have not been thoroughly characterized (e. Benzothiazole has been detected in leachate from shredded scrap tires commonly used as pavement additives and is a likely toxin (Eldin 2002). Because they were widely used historically and are very stable in the environment, their residues are frequently found in soils of areas where they have been manufactured or used, including many industrial and urban sites. Organic compounds can have toxic effects on aquatic organisms and/or influence surface water oxygen levels when present at sufficient levels. Discharges of organic compounds and materials of all types show a strong correlation to suspended sediment discharges (Barrett et al. As sediments accumulate in receiving waters, concentrations of associated organic pollutants can increase to levels above those found in the adjacent water column. Over time these sediment levels can become high enough to cause adverse impacts to organisms living in, interacting with, or connected through the food chain to those sediments. A common construction site practice is to stockpile topsoil, roots, and other vegetative debris from site clearing on-site for use in final site landscaping. If not protected from erosion, these stockpiles can contribute organic matter, sediment, turbidity, and adsorbed pollutants to surface waters. Taylor and Roff (1986) documented extensive erosion of straw mulch from a construction site, sufficient to clog culverts downstream of the site. Elevated loadings of organic material can increase levels of oxygen-demanding substances (e. These blooms can deplete oxygen levels diurnally and elevate organic matter content in water discharged from these basins. Some studies have documented a decline in the organic matter content of surface water sediment due to construction activity (Barton 1977; Young and Mackie 1991). This effect is derived from the erosion of largely inorganic soil particles from construction sites and the high levels of those sediments entering the surface water. Some aquatic organisms depend on organic matter in surface water sediments as a food source. Elevated levels of sediment containing low levels of organic matter can reduce the food value of this material for these organisms. November 2009 3-13 Environmental Impact and Benefits Assessment for the C&D Category 3. These products contain a diverse array of organic compounds, many poorly characterized in terms of environmental behavior and impact. Petroleum hydrocarbons are often monitored in water as a group, either as total petroleum hydrocarbons or as oil and grease. Petroleum-derived aliphatic hydrocarbons on construction sites typically derive from human activity, either current or historic. Many historic industrial sites have some level of petroleum hydrocarbon contamination in site soils and, at some sites, groundwater as well. Improper operation, fueling, and maintenance of construction equipment, and poor housekeeping practices (e. Petroleum hydrocarbons tend to adsorb to soil and sediment particles and travel with them as they erode and settle in surface waters. Petroleum hydrocarbons discharged directly to water spread quickly to cover water surfaces. Microbial activity in surface waters eventually degrades the more structurally simple components of petroleum materials (e. Petroleum hydrocarbons can affect aquatic organisms through direct toxicity, smothering, and changes in water quality. Water quality impacts can include light reduction, pH alteration, dissolved oxygen reduction, and dissolution of some product components in the water column. Oil, grease, fuel, and other petroleum hydrocarbons typically contain toxic and carcinogenic constituents. Fish can be exposed to petroleum hydrocarbons through contact with dissolved fractions in the water column, particulate fractions and contaminated sediments and ingestion of contaminated food and water. Floating egg masses can come into contact with surface hydrocarbon layers (Malins and Hodgins 1981). Garton (1977) documented a diesel spill at a construction site that resulted in a fish kill. Waterfowl can be affected by external oiling, ingestion, egg oiling, and habitat changes. Anthropogenic sources include thermal combustion by industrial, municipal, power plant, vehicular, and household entities. They can accumulate in soils, particularly in urbanized areas, and subsequently erode after ground disturbance. Their adsorption to sediment increases with increasing organic content of the sediment. At higher concentrations, however, they interfere with cell division and photosynthesis (Eisler 1987). Effects on aquatic invertebrates include inhibited reproduction, delayed emergence, sediment avoidance, and mortality. Effects on amphibians and reptiles include impaired reproduction, reduced growth and development, tumors, and cancer. Effects on fish include fin erosion, liver abnormalities, cataracts, and immune system impairments (Eisler 1987; Van Veld et al. Organic pesticides have been and continue to be used extensively on both agricultural and urban lands (e. Some pesticides, including many organochlorine pesticides used historically but since banned in the United States, create residues that are able to persist in soils for long periods of time. Pesticide residues on construction sites can derive both from activities associated with construction (e. Chlorpyrifos and diazinon have been detected in construction site stormwaters in California (Kayhanian et al. Except for endosulfan, use of these pesticides was generally banned in the United States because of their toxicity, persistence in the environment, and/or potential to bioaccumulate. Persistence, bioaccumulation, and toxicity properties vary among organic pesticides. Some organic pesticides in current use are generally believed to degrade more quickly once applied in the environment and have fewer toxic effects. Due to their hydrophobic nature, pesticides tend to adsorb to sediments and organic materials and, therefore, tend to erode, travel, and settle with sediment particles in surface waters.
Flotation technology was also developed using a cyanamid collector for concentration of weathered coal blood pressure chart for 19 year old cheap torsemide 10 mg line, giving germanium recoveries of 75 per cent prehypertension to treat or not to treat buy cheap torsemide 10 mg online. An innovative blood pressure chart pregnant order torsemide 20mg with amex, economic and environmentally friendly germanium recovery process from waste products of optical fibres has been developed by Bell Labs (Global Industry Analysts blood pressure chart gov generic torsemide 10 mg free shipping, 2010) heart attack 51 purchase torsemide 10 mg without prescription. Specifications Germanium is used and traded in a variety of forms heart attack manhattan clique remix buy discount torsemide 10mg, including zone-refined crystalline germanium, germanium tetrachloride, high-purity oxides, first-reduction ingots, single-crystal bars and castings. Germanium tetrachloride, GeCl4 GeCl4 is recovered from germanium-bearing concentrates by dissolution in hydrochloric acid and purification through a series of fractional distillations. GeCl4 is used to profile the refractive index of optical fibres for telecommunication. It is produced in two qualities, fibre-optic grade and ultrahigh-purity grade with less than five parts per billion metal impurities, used as a dopant for fibre optical products. Germanium melting zone moves from a monocrystalline seed along a polycrystalline rod. The point-contact diodes for radar pulse detection had already been used during the war. From 1948 until the 1970s, germanium transistors played a vital role in solid-state electronics, but then were replaced by high-purity silicon that has superior electrical properties. New applications arose in the late 1950s with the boom in nuclear physics and the need to develop nuclear radiation spectrometers with good energy resolution. Global sales volumes of germanium at manufacturer level, which basically represent the germanium content in end-use sectors, were about 115 tonnes germanium in 2010. Relative proportions of these three applications have continuously changed over the years without showing a major trend. The regional end-use distribution pattern of infrared optics is almost identical to the regional end-use pattern for fibre optics (Global Industry Analysts, 2010). Compared to the dominant three end-use sectors, various applications in the electronic/solar industry consume about 15 per cent of the germanium produced. Although in small amounts only, other uses of germanium include gamma ray detectors, X-ray monochromators, thermo-photovoltaics, medical applications such as chemotherapy, and metallurgy (alloys with tin to increase hardness or silver to prevent tarnishing (Angerer et al. Most of the scrap is sent to germanium processors for recycling which are able to recycle material containing a minimum of 190 frank melcher and peter buchholz Table 8. Al, aluminium; As, arsenic; B, boron; Ga, gallium; GeO2, germanium dioxide; In, indium; Nb, niobium; P, phosphorus; Sb, antimony; Si, silicon. Infrared optics: about 30 per cent of the germanium consumed for this end use is produced from recycled materials that accumulate during the manufacture of optical devices such as broken Germanium 191 1990 13% 19% 8% 25% 5% 2000 5% 50% 60% 15% 2007 10% 12% 24% 15% 2010 5% 30% 25% 31% 23% 25% Fibre-optic systems Infrared optics Polymerisation catalysts Electronics and solar electric applications Phosphors, metallurgy, medicine Figure 8. Old computers which are dismantled or shredded contain only minute amounts of germanium in their electronic parts. The major challenge is the effective collection of old devices and cost-effective separation of metals. Polymerisation catalysts: estimated world polyester production in 2009 was about 50 million tonnes per year (Chemsystems, 2011). In 2006, about 350,000 tonnes per year was produced by using germanium catalyst as a substitute for antimony catalyst, mainly in Japan. Applying germanium instead of antimony results in very low levels of antimony contamination in bottled drinking water. This compares favourably with the five per cent to ten per cent of broken lenses and glass from nightvision devices that were recycled as old scrap in the past (Jorgenson, 2006). Fibre optics: fibre-optic cables for telecommunication contain up to 60 per cent of recycled material and the recovery rate of germanium from fibres is up to 80 per cent (Jorgenson, 2006). Fibre-optic cables also have a long residence time in their applications, thus recycling volumes for old scrap are rather low. However, in the future, they may have considerable post-consumer recycling potential. Electronics and solar electrical applications: during solar-cell production, about 50 per cent of Substitution Since the beginning of the industrial use of germanium, attempts have been made to substitute this expensive and rare metal. The use of germanium in fibre-optical systems is challenged by the invention of photonic crystal fibres consisting of an array of glass capillaries and solid rods stacked together. More than 80 per cent of the germanium reserves and resources are located in Guangdong, Yunnan, Jilin, Sichuan and Shanxi. In the Russian Federation, about 4000 tonnes germanium reserves have been calculated for 21 deposits (Kats et al. The remaining reserves are hosted in sulfide deposits in the Urals, Altai and Caucasus regions. They also estimate that at least a few thousand tonnes of germanium are present in the coal ash and ue dust produced annually at coal-fired power stations. However, extraction of germanium from these waste products is not generally economic under present conditions. Data on germanium resources in volcano-sedimentary magnetite-hematite deposits are not available. A compilation of published and estimated reserves for active and semi-active mines and advanced exploration projects by Elsner et al. The amount of germanium potentially recoverable from coal ash is unlimited, but the commercial recovery is currently not viable except for germanium-rich coals from Russia and China. The same holds for the extraction of with its low-cost products, replacement of expensive GeO2 is possible using titanium-, antimonyand aluminium-based catalysts. Environmental aspects of the life cycle of germanium and its products Germanium has little or no effect upon the environment because it usually occurs as a trace element in rocks, ores and most products. Of the materials consumed or produced as a by-product during processing of germanium-bearing materials, arsenic and cadmium may present potential problems. However, these metals are separated out at the smelter stage and are readily controlled in the refineries. Acids and bases used in processing are neutralised and held in tailings ponds (Roskill, 1988). Germanium compounds also have a low order of toxicity, except for germanium tetrahydride, which is considered toxic (Roskill, 1988). Resources and reserves Global resource and reserve data for germanium are difficult to obtain, because details relating to trace-metal concentrations in many sulfide and coal deposits are not readily available, or are of poor quality. The combined germanium reserves and resources in China are estimated to be about 3782 tonnes (Xun, 2002), distributed in 33 germanium ore districts in 11 provinces or autonomous Table 8. Annual germanium production capacity is the installed capacity, except where the value is in parentheses when it is potential capacity. Annual Ge production (maximum capacity) in tonnes per year 10 (30) 10 15 Deposit Huize Country China Mining Company1 Yunnan Huize Lead and Zinc Mine2 Sichuan Hongda Co. Returned residues from Zn production at the Clarksville, Tennessee, smelter were expected to contain up to 45 tonnes per year Ga and 35 tonnes per year Ge (Guberman, 2008). Production As with data for reserves and resources, data for global germanium mine and refinery production are not readily available or are of poor quality. It is also extracted from coal ash in China, Russia, Ukraine and possibly Uzbekistan (see Tables 8. Estimated global germanium mine production in 2010 was probably more than double the reported refined germanium production (Mikolajczak, 2011; more than 300 tonnes in residues), which means that major amounts of germanium are not being extracted from residues. The currently installed global extraction and refining capacity is estimated at about 180 tonnes per year (Mikolajczak, 2011). Since 2001, China has continuously taken the lead in global refinery production (Figure 8. In China, five smelters/refineries account for the estimated 70 to 100 tonnes of germanium and germanium compounds produced (Guberman, 2009; Mikolajczak, 2011; Tse, 2010): Yunnan Lincang (ca. The total Chinese production capacity is thus estimated to be 130 to 200 tonnes germanium. In Russia, only the Spetzugli lignite deposit in the Pavlovsk area is currently in production. About 100 zinc exploration projects are in the conceptual stage with little information about germanium grades. Another 50 exploration projects are in the prefeasibility and in the feasibility stage which are being studied in greater detail (Raw Materials Group, 2011). Although most of these zinc deposits have low germanium contents, it is possible that germanium could be extracted from residues of the smelting and refining stages. Another project of similar scale is the Tres Marias zinc mine in Mexico which grades 20% Zn and 150 ppm Ge (in some sections up to 245 ppm Ge). They also have special expertise in manufacturing and offer a wide range of germanium-based products for various applications. Future germanium supplies will, therefore, continue to depend upon the availability of germanium-bearing residues from the processing of zinc ores, from germanium-bearing coal ash and from recycling. However, about 300 potential germanium-bearing sites have been reported for Africa alone, excluding coal (Deschamps et al. For example, if appropriate production capacities were developed, germanium could be extracted from the residues of electrolytic zinc production. Germanium-bearing coal and ue dusts constitute the most important germanium resource by volume (Seredin et al. In addition, large germanium reserves are related to coking coals in the Kemerovo region, Siberia, that carry 1. However, production from this source will depend on the development of germanium prices and technological improvements, especially in western countries. Selective mining, processing, transport and thermal use of coal from such zones would lead to increased germanium grade in ashes. To install this selective production route would be a major challenge and selective mining of germaniumrich zones would not be practical in most coal deposits. In addition, recycling of germanium will remain a major source of supply in future. The traded volumes and transport costs per unit are low, thus refined germanium and manufactured germanium compounds are easily shipped around the globe. Between 2000 and 2006, the volumes of global annual sales did not vary significantly; they ranged between 88 tonnes (2003) germanium to 125 tonnes germanium (2006) (Global Industry Analysts, 2010). These data indicate that the market and trade have been relatively stable in the past. Prices Since the 1950s, germanium prices were mainly in uenced by its usage in high-tech applications. Before the 1970s, germanium was essential for the production of diodes, rectifiers and transistors, but subsequently substituted by electronicgrade silicon. This trend was offset by the massive demand of fibre optics in the telecommunications sector, in infrared night-vision devices and as a polymerisation catalyst. Due to these trends and tight supply, the first drastic price increase occurred at the beginning of 1979 when germanium prices tripled (Brown, 1998). For recycled material, the dominant markets are North America, Europe and Asia-Pacific. Following strong downward price movement up to 2003, prices for germanium dioxide climbed and dropped due to the boom and bust movement of the global economy. The most recent price peak in 2011 is a function of global economic growth combined with a strong demand of germanium dioxide for fibre optics and supply shortages. The supply shortages are caused by the closure of the Chinese Shaoguan dioxide plant due to political clampdown on pollution- and power-intensive industries and strong demand from the Chinese defence sector. This can be explained by the interplay of several factors, namely Chinese export taxes, shutdown of three Chinese germanium dioxide plants and speculation of increased demand for germanium used in polymerisation catalyst following the 2011 earthquake and tsunami in Japan (Guberman, 2013). The future price of germanium will depend on the Chinese market, breakthrough technologies (see below) and various substitution possibilities already developed. Outlook Supply challenges Major germanium supply will be driven by primary zinc mine production and subsequent refining, and by extraction from coal ashes recovvered from burning of germanium-rich coal. Processing costs versus germanium price will determine the production of germanium as a by-product. New demand could probably be met through the expansion of existing capacities and the installation of new processing capacities. Recycling of old scrap will not be a significant contribution to world supply in the near future. However, post-consumer scrap may increase slightly when solar fibre-optic cables or military devices are being replaced or if germanium-based solar cells are widely adopted and are recycled at the end of their lifetime after 15 to 25 years. Advances in recovering germanium from coal ash at coal-fired power plants, which is already an important source in China and Russia, could make a difference to future supply. Commercial recovery of the metal appears not to be economically viable for many plants burning germanium-poor coal (Bleiwas, 2010), but it appears that few samples of ash from power plants and of coal deposits have been studied in detail for germanium. A weak acid solution recovered up to 83 per cent of the germanium from f1y ash samples over a two-hour leach period. Other potential primary sources include germanium-rich magnetite from magnetite-hematite volcanic-sedimentary deposits in Ukraine, Kazakhstan and Russia 199 (Smirnov, 1977, Kats et al.
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It is also capable of being recycled from secondary sources when it appears as an alloy with aluminium hypertension 4 mg buy torsemide 10 mg low cost. By careful handling prehypertension risks torsemide 20mg low cost, most of the magnesium is recovered in the recycled aluminium blood pressure chart easy to read cheap torsemide 20mg line. This classification was developed in the 1980s to ensure the purity of magnesium metal and alloy derived from secondary sources and thereby to reduce problems associated with corrosion arrhythmia cardiac order 20 mg torsemide with amex. This material consists of gates and runners from die casting hypertension nclex questions discount 20mg torsemide mastercard, together with scrap castings and used parts that have been isolated from other scrap hypertension used in a sentence 20mg torsemide. Class 1 magnesium scrap recovery is mostly carried out by special smelters and refiners who take the scrap from the die casters and return Magnesium clean ingot with closely specified alloy chemistry. It is estimated by the author that the total magnesium recycling capacity in the world is about 200,000 tonnes per year with actual recycling of about half that amount in 2010. In addition, it has been estimated that 30,000 tonnes per year could be recycled internally by the die casting companies. Class 1 scrap recycling capacity in Europe has been estimated to be 75,000 tonnes per year (Fechner et al. Asia, particularly China, has many primary plants and many of these utilise scrap returned by their clients. There are two basic methods of recycling magnesium: ux-free recycling and recycling with ux. The uxes used are chloride-based salts which have been used for many years to separate oxide and other solid inclusions from the molten magnesium. In recent years, specially designed furnaces have been developed to enable melting to be done without ux. Instead they use inert atmospheres to prevent the molten magnesium from oxidising during melting and refining. The quality and characteristics of scrap may vary widely, even from one producer of magnesium die castings to another. Even Class 1 scrap can vary and, consequently, recycling contracts are typically based on a preliminary evaluation of representative material. This is followed by a detailed quality plan produced in collaboration with the generator of the scrap to ensure continuing conformance to the agreed specification. The value and cost to the die caster are highly dependent on the quality of the metal recovered. The industry recycling programmes for magnesium are applied to clean and compact 271 scrap of known composition. This material is remelted, refined and re-used for manufacturing magnesium components. The metal from the other scrap classes can be recovered, but it is mainly used for the production of iron desulfurisation reagents or as an alloy element in an aluminium alloy production process. The processing of scrap with a low metal content and of sludges from the melting and recycling process still poses major problems. As the utilisation of magnesium alloys in the automobile industry grows, and more attention is directed to the management of scrap from end-oflife vehicles, more technical developments will be required to cover the treatment of all magnesium scrap classes. Several large European, North American and Asian research organisations are working on these problems. Substitution Magnesium alloys are used in many applications including the aerospace, automotive and the 3-C industries. The properties of magnesium, such as its strength-to-weight ratio, its low fabrication costs and other special properties, such as electromagnetic shielding, thermal and electrical conductivity, and damping characteristics, combine to make it difficult to find a direct substitute for magnesium. From time to time, some plastics or composites have been proposed as potential replacements for magnesium especially for applications with short product lives. Some potential problems when magnesium components are being joined can be addressed by choosing fasteners with similar thermal expansion coefficients, such as aluminium or magnesium fasteners. Neelameggham (2013) notes that the use of fasteners made of aluminium or magnesium would also overcome the problems caused by the inappropriate use of steel fasteners 272 neale r. When a steel fastener is used, its lower thermal expansion against the increased expansion of magnesium causes stresses when the temperature of the part increases, and when the part cools the bolt tension gets reduced, which is termed creep. When a steel fastener is used for holding magnesium alloy base and top part, whenever an aqueous solution gets between the steel and magnesium a galvanic cell is created causing magnesium to corrode more rapidly However, if an aluminium or magnesium fastener is used these problems are avoided and the longevity of the parts increased. The Porsgrunn plant in Norway used sea water and dolomite as raw material which was converted to magnesium oxide and then to magnesium chloride which was used to feed the electrolytic cells. At times, the Porsgrunn plant also utilised magnesium chloride brine from Germany as a source of magnesium. In Becancour the magnesium chloride was produced by treating magnesite with hydrochloric acid. This required Hydro Magnesium to modify the electrolytic process in Porsgrunn to develop the use of hydrogen to convert the anode gas chlorine into hydrogen chloride and hydrochloric acid. This process was selected for the plant built in Becancour which operated from 1991 until 2006. The published estimates for the production capacities of each of these plants were about 40,000 metric tonnes per annum (Burstow, 1999). Albright and Haagensen (1997) also discussed some of the global warming issues which came to prominence Environmental aspects As the lightest available structural metal, the use of magnesium provides the benefit of reducing the weight of automobiles and thereby reduces gasoline consumption. This results in substantial reduction in the carbon dioxide emissions from an automobile during its lifetime. The cover gas provides an inhibitive and tenacious film of uoride and/or sulfur compound to prevent reaction of the molten alloy with oxygen. Although the construction of electrolytic plants continues to be slow, the research and development of the new equipment and methods should be encouraged on a global basis. In addition, they had to address disposal of solid wastes comprising mostly reduction furnace residues and casting sludges containing uxes. Recent thermal processes tend to make by-products for sale from the solid residue from retorts in an effort to provide added revenues. Separate calculations were made for both pure magnesium production and for magnesium alloy production (Table 11. This waste is disposed of at authorized sites and does not cause any negative environmental impact. This process, using magnesite feed material, was tested in a 1500 tonne per year pilot operation, but the commercial plant was not constructed. In 1997 when Noranda was permitting its Magnola magnesium project, utilising an asbestos waste (serpentine) as raw material, the company was required to meet strict controls on emissions of chlorinated hydrocarbons, dioxins and chlorine. Similar concerns must be addressed in the design and operation of electrolytic magnesium reduction plants today (Brown, 2003b). Improved scrubbing technology, together with various process modifications, has made great progress in Greenhouse-gas emission studies Casting cover-gas issues For most of the twentieth century magnesium production, both electrolytic and thermal, used either sulfur or sulfur dioxide as a cover gas while casting magnesium to prevent oxidation. When this was done in an uncontrolled fashion sulfur dioxide was released into the work area. Accordingly from the 1970s onwards magnesium companies worldwide started switching to using sulfur hexa uoride. Some of the work was conducted as part of investigations into the advantage of lighter weight magnesium cars in regard to Life-Cycle emissions. The initial calculations were part of a study to assess the environmental impact of a magnesium engine block supply chain. The majority of the plants built in China during the 1990s used very simple melting and casting operations with sulfur powder directly dusted on the cast ingots to prevent oxidation during solidification. When the plants increased in size, most of the operations retained the sulfur dusting for convenience and simplicity. Most of the small Chinese Pidgeon process plants that used coal as the main energy source and large quantities of hand labour are now disappearing. Larger, more efficient plants, with advanced technology and equipment, are being built. The Chinese are approaching the problem of addressing the global warming potential by improving the production plants and working hard in downstream processing to produce lightweight magnesium products for use in bicycles, motorcycles, cars, trains and airplanes. China has been carrying out industrial restructuring for the cover gases were developed as a result, but most of the companies started reverting back to using sulfur or sulfur dioxide in a controlled fashion. Life-cycle analysis When comparing the use of various structural metals in automobiles, it has become customary to normalise the advantages and disadvantages by carrying out Life-Cycle Analyses of the material usage with respect to reduction in fuel usage. There have been several life-cycle analyses of magnesium production along with downstream fabrication of parts for use in automobiles. Further sub-division assessed the preparation of the magnesium-containing feed materials and the actual processing of this material to produce magnesium metal. All of these areas are impacted by secondary and upstream processes which impact on the magnesium production. For example, the method of onsite electricity generation for the production of the input materials may be responsible for significant emissions. Environmental concerns related to magnesium production and magnesium processing first appeared in the early 1990s when Life-Cycle Analysis articles started to be published. Subsequently various studies have compared the environmental impacts of the two main magnesium production processes. As the measurement technology improves and the information is better understood so the environmental challenges can be more clearly identified. The pressures from the climate control aspects might impact on the status of the differing processes used for magnesium production. Academic studies on the global warming impacts of present-day magnesium production processes have been published (Ramakrishnan and Koltun, 2004a, 2004b and Cherubini et al. Magnesium purpose of optimising its magnesium industry and upgrading its competitiveness. Some of these measures have been announced in the Chinese 5-year plans, as noted in China Magnesium Industry and Market Bulletin (Sunlight Metal Consulting (Beijing) Co. The Chinese government has announced new regulations requiring existing smelters to consume a maximum of 5. Much of the fuel-based pollution in China is currently being addressed and, wherever it is available, natural gas is being designed into many of the newer plants. Magnesium is produced by a highly modified vertical furnace process by Rima Metallurgical in Brazil. This is a silico-thermic process which uses an electrical resistance furnace for reducing the briquettes of calcined dolomite with ferrosilicon, instead of the fuel-fired retorts of the Pidgeon process. He concluded that magnesium is the preferred metal in terms of its overall carbon dioxide emissions. It is also important to note that the raw materials used in making magnesium, such as dolomite and magnesium chloride, are not toxic. All plants have magnesium in the centre of the chlorophyll molecule essential for photosynthesis through the green pigment in the leaves. Magnesium is also important to all living cells where it plays a major role in the functioning of numerous enzymes. World resources and production Global resources of magnesium, on land and in the sea, are huge compared to current production and usage. There have been a number of closures of formerly important magnesium producers in the West in the last two decades. These include Pechiney in France, which stopped producing magnesium in 2001 from its thermal magnesium plant. Dow initially used brine in Michigan as the source of magnesium and latterly sea water in Freeport, Texas. At its peak Dow produced about 100,000 tonnes per year, utilising partly hydrated magnesium chloride cell feed in its electrolytic process. In Japan, Ube Industries stopped its thermal magnesium production at the end of 1994. Other countries which formerly produced magnesium include Canada, Italy, Norway and Yugoslavia (Serbia). The magnesium plant in Becancour, Quebec, Canada, which operated between 1991 and 2006, produced 40,000 to 50,000 tonnes per year magnesium. The Magnola Metallurgie, Noranda magnesium plant, also in Canada, operated for a short time between 1999 and 2001. Rima Metallurgical, Brazil, which has been in production since the late 1970s and currently produces about 20,000 tonnes per year of thermal magnesium. Dead Sea Magnesium, Israel, which has been producing about 30,000 tonnes per year by electrolysis of carnallite since 1995. Total world magnesium production was estimated at 775,000 tonnes in 2010, up from 619,000 tonnes in 2009. The global economic downturn has led to a worldwide decrease in the die-casting market, which now accounts for between 28 and 35 per cent of total usage. It has an initial design capacity of 15,000 tonnes per year and was developed with the assistance of a Chinese company. South Korea has recently started primary magnesium production from dolomite by the thermal method. Posco, the South Korean steel producer, will be the main producer, with a projected output of 10,000 tonnes per year and a plant start-up in 2012. They have demonstrated the production of a 16-tonne coil of wrought magnesium alloy sheet using the twin roll casting machinery originally developed by Fata Hunter. Since 2006 the Ural Asbestos Company has been studying the construction of a magnesium plant using asbestos waste converted to magnesium chloride for an electrolytic process. The parent company is interested in this project and has been involved in raising capital for the project since 2009 but there were no major announcements in 2011. World trade Global import and export data for magnesium are illustrated in Figures 11.
