Great Lakes degradation

The exponential growth in population and technology that has occurred in the Great Lakes Basin has resulted in human activities degrading even these large bodies of water. 

Mirex and its degradation products in herring gull eggs collected from the Great Lakes in 1977... 

Modified from Norstrom, R.J., D.J. Hallett, F.l. Onuska, and M.E. Comba. 1980. Mirex and its degradation products in Great Lakes herring gulls. Environ. Sci. Technol. 14 860-866. 

Bennett, E.R. and Metcalfe, C.D. 2000, Distribution of degradation products of alkylphenol ethoxylates near sewage treatment plants in the lower Great Lakes, North America. Environ. Toxicol. Chem. 19 784-792. 

Peaks 5 and 7 were depleted in both the soil and overlying air. Similar degradation profiles were seen in southern ambient air samples from Alabama [34], Texas and Arkansas [38], and in Great Lakes air (Sect. 3.1.3). Their main components, B8-531, B8-806 and B8-809, are predicted to be relatively labile on the basis of molecular structures [39,40]. 

Of the 5.34 x 1051 of toxaphene that were used in North America (includes the United States and Mexico), 1.541 (3%) was estimated to remain in active circulation as of the year 2000, 6.5 x 1041 (12%) had been removed from the continental environment by advection of air and water and burial in soils and sediments, and 4.54 x 1051 (85%) had been removed by degradation reactions. Most of the toxaphene in active circulation resides in the soils of the southern U.S. and Mexico (83%). The efficiency of toxaphene transfer to the Great Lakes from its usage within the basin was estimated to be 78 to 220 times greater than transfer from the southern United States. However, load-... 

Table 10 Proportion of persistent chlorobornane degradation products B6-923 and B7-1001 in total chlorobornanes in Great Lakes sediments...

There are several natural non-combustion sources of PAHs. A study in 1980 by Wakeham [43] concluded that phenanthrene could be created by the dehydrogenation of steroids, retene could be produced by the diagenesis of abietic acid, and alkyl chrysenes could form from the degradation of the pentacyclic triterpenes alpha- and beta-amyrin, which are components of higher plant waxes. In this section we will look at the natural non-combustion sources of retene and perylene and how these sources might impact the Great Lakes. 

Once in the Great Lakes, photolysis reactions are predicted to result in relatively short half-lives [67], but the experiments to determine these photolysis rate constants were performed in pure water and some even involved the presence of photosensitizers. PAHs have been shown to be much more resistant to photo-degradation when sorbed to suspended particulate matter in natural waters [68]. Simcik et al. [23] found no evidence of photodegradation of PAHs that were atmospherically deposited to Lake Michigan, settled through the water column and collected in the sediments. 

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