Lakes continued

East Asia is the only part of the world where P.R.58 2, a calcium lake, continues to be used. The pigment affords bluish red shades, somewhere between those of P.R.53 1 and 57 1. Its main field of application is in printing inks, where its lightfastness equals that of P.R.57 1 the two pigments also exhibit similar tinctorial strength. 

Several classes of (3-lactamases, often encoded in transmissible plasmids, have spread worldwide rapidly among bacteria, seriously decreasing the effectivenss of penicillins and other (3-lactam anti-biotics.t y Most (3-lactamases (classes A and C) contain an active site serine and are thought to have evolved from the dd transpeptidases, but the B typey has a catalytic Zn2+. The latter, as well as a recently discovered type A enzyme,2 hydrolyze imipenem, currently one of the antibiotics of last resort used to treat infections by penicillin-resistant bacteria. Some (3-lactam antibiotics are also powerful inhibitors of (3-lactamases.U/aa/bb These antibiotics may also have uses in inhibition of serine proteasesCC/dd such as elastase. Some antibiotic-resistant staphylococci produce an extra penicillin-binding protein that protects them from beta lactams.ee Because of antibiotic resistance the isolation of antibiotics from mixed populations of microbes from soil, swamps, and lakes continues. Renewed efforts are being... 

Although most of the oil from the lakes has been removed or has been the subject of heavy weathering, the lakebeds still contain a large amount of oil, which cannot be easily removed. Analysis of samples indicated that the composition of the oil in the lakes continues to change [77]. The chemical composition of weathered oil showed a decrease in aromatic compounds, and an increase in resins and higher polycyclic aromatic hydrocarbons. This inaeases the hazard potential of oil lakes. Heavily contaminated soils may eventually erode and be resuspended and transported to populated areas during dust storms and could cause health hazards [35]. There is also the possibility of contaminating soil with heavy metals, particularly nickel, vanadium, chromium, and lead. 

The principal source of 2-thiophenecarboxaldehyde is Great Lakes Fine Chemicals Ltd. in the United Kingdom, whereas 2-acetylthiophene is produced by a number of manufacturers. Some of the 2-acetylthiophene producers continue derivatization to 2-thiophenecarboxyhc acid and 2-thiopheneacetic acid. 

In the manufacture of colored papers, it is best to add the dyestuffs before addition of rosin size and alum. This is not always possible in continuous dyeing procedures where dyestuffs must be added to stock containing size and/or alum, and this may cause premature laking of the dyestuffs and subsequent loss of tinctorial strength and/or dullness of shade. The proper selection of dyestuffs can help to reduce these disadvantages. 

Sodium, 22 700 ppm (2.27%) is the seventh most abundant element in crustal rocks and the fifth most abundant metal, after Al, Fe, Ca and Mg. Potassium (18 400 ppm) is the next most abundant element after sodium. Vast deposits of both Na and K salts occur in relatively pure form on all continents as a result of evaporation of ancient seas, and this process still continues today in the Great Salt Lake (Utah), the Dead Sea and elsewhere. Sodium occurs as rock-salt (NaCl) and as the carbonate (trona), nitrate (saltpetre), sulfate (mirabilite), borate (borax, kemite), etc. Potassium occurs principally as the simple chloride (sylvite), as the double chloride KCl.MgCl2.6H2O (camallite) and the anhydrous sulfate K2Mg2(S04)3 (langbeinite). There are also unlimited supplies of NaCl in natural brines and oceanic waters ( 30kgm ). Thus, it has been calculated that rock-salt equivalent to the NaCl in the oceans of the world would occupy... 

Water birds have not been shown to be directly affected by acidification. However, the prey of waterbirds may be of concern as these lower food-chain organisms may have elevated levels of toxic metals related to acidification of their habitat. Moreover, most water birds rely on some component of the aquatic food-chain for their high protein diet. Invertebrates that normally supply caJcium to egg-laying birds or their growing chicks are among the first to disappear as lakes acidify. As these food sources are reduced or eliminated due to acidification, bird habitat is reduced and reproductive rate of the birds is affected. The Common Loon is able to raise fewer chicks, or none at all, on acidic lakes where fish populations are reduced 37 and 5S). However, in some isolated cases, food supplies can be increased when competitive species are eliminated (e.g.. Common Goldeneye ducks can better exploit insects as food when competition from fish is eliminated). The collective influences of acidification are difficult to quantify on a specific area basis but for species that rely on a healthy aquatic ecosystem to breed, acidification remains a continuing threat in thousands of lakes across eastern North America 14). 

Concentrations of PCBs in fish from each of the Great Lakes currently exceed the GLWQA objectives for the protection of aquatic life. Similarly, concentrations of some substances (e.g., PCBs, Hg, mirex, toxaphene) in Great Lakes fish continue to exceed acceptable guidelines for human consumption. Documented effects in the Great Lakes include reproductive failure, congenital abnormalities and induction of tumours in various aquatic, terrestrial and avian species (23). 

It is clear that water quality management of the Great Lakes has resulted in a number of successes. However, major problems remain or will arise continually to test the management system and its capability. Some of these issues are summarized briefly below. 

In many ways, both Canada and the United States continue to be involved in a unique experiment of co-operative management of serious environmental issues which plague a shared international resource. Despite the institutional complexity and the history of abuse that man s activities have wrought on the Great Lakes, the experiment to restore and protect them has had several successes typhoid and cholera were eradicated eutrophication problems are now largely under control and where adequate control programs for toxic chemicals have been implemented and enforced (e.g., mercury, DDT, PCBs), there have been associated declines in concentrations in the lakes. These successes have been due in no small way to the spirit of co-operation that has continued to exist between Canada and the United States and the unique institutional arrangements entered into by the two countries. 

It has become increasingly evident, however, that management of Great Lakes resources to provide sustainable benefits cannot be achieved by the cooperative action of governments alone. Despite admirable efforts carried out under the Canada/United States Water Quality Agreements, problems continue to persist and many important resources continue to be depleted both qualitatively and quantitatively. Collective action on the part of all users of the lakes will be required if the Great Lakes are to be restored and protected for the benefit of future generations. 

Thus, as with studies on the double-crested cormorant in the Great Lakes (see Chapter 16 in Walker et al. 2006), there is evidence of a continuing (although reduced) effect of p,p -DDE on reproductive success even after environmental levels had fallen and eggshell thinning was much less. This raises the possibility that p,p -DDE may have had toxic effects other than eggshell thinning on these species (Nisbet 1989). There is the further complication that other OCs such as PCBs, dieldrin, and hep-tachlor epoxide were present in the same samples and may have had toxic effects. 

PCBs have been implicated in the decline of certain populations of fish-eating birds, for example, in the Great Lakes of North America. Although their use is now banned in most countries and very little is released into the environment as a consequence of human activity, considerable quantities remain in sinks (e.g., contaminated sediments and landfill sites), from which they are slowly redistributed to other compartments of the environment. There continues to be evidence that PCB residues are still having environmental effects, for example, on birds and fish. 

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