River anthropogenic sources

It is difficult to assess the different anthropogenic sources of major ions which depend on the factors mentioned above. These human factors also vary in time for a given society and reflect the different environmental concerns of these societies, resulting in multiple types of river-society relationships (Meybeck, 2002). In the developed regions of the northern temperate zone it is now difficult to find a medium-sized basin that is not significantly impacted by human activities. In industrialized countries, each person generates dissolved salt loadings that eventually reach river systems (Table 8). 

Continental crust is the ultimate source of trace elements in hydrologic systems. Trace elements are introduced in the river basin by rock weathering, atmospheric dry and wet deposition and by anthropogenic activities. The sketch diagram of Figure 8 summarizes the natural and anthropogenic sources of elements in aquatic environments (modified after Foster and Charles worth, 1996). 

The concentration of Ni in the lithosphere is 55p.gg (Li, 2000) and the concentration of dissolved Ni in stream water is 2p,gL (Turekian, 1971). More recent data on the concentration of dissolved Ni in average world river water indicates the value to be 0.8 xgL (Gaillardet et al., 2003) and the Ni concentration in ocean water to be 0.47 xgL (Chester, 2000). Natural emissions of Ni to the atmosphere are dominated by windblown dusts while anthropogenic sources that represent 65% of all emission sources are dominated by fossil-fuel... 

In an attempt to assess the quantitative contribution of reactive processes to the overall cycling of anthropogenic source contamination, two examples will be considered (i) vinyl chloride oxidation at groundwater-surface water interface (GSI) St. Joseph, Michigan (e.g., Lendvay et al., 1998a,b), and (ii) dioxin dechlorination in estuarine sediment cores collected from the Passaic River, New Jersey... 

The natural occurrence of mercury in the environment means that mercury is likely to occur in surface waters, even when anthropogenic sources of mercury are absent. Freshwaters without known sources of mercury contamination generally contain less than 5 ng/L (ppt) of total mercury in aerobic surface waters (Gilmour and Henry 1991). Mercury levels in water-borne particulates in the St. Louis River estuary... 

Dreissena polymorpha St. Lawrence River near Sainte-Foy Quebec, Canada Graczyk et al., 2001 C. parvum genotype 1, anthropogenic source, oocysts in hemolymph and flesh, 4.4 x 102 oocysts/mussel... 

Davis, J. S., and J. Zobrist (1978), The Interrelationships among Chemical Parameters in Rivers—Analysing the Effect of Natural and Anthropogenic Sources, Progr. Water Techno . 10, 65-78. 

The global cycling of copper has been reviewed by Nriagu (1979) and is described schematically in Fig. 15-16. Like most heavy metals and in contrast to mercury, the flux of copper from terrestrial to oceanic reservoirs is dominated by transport in rivers. Copper reaching the oceans by atmospheric transport is of the same order of magnitude as that by three strictly anthropogenic sources direct discharge... 

In order to understand the full extent of the mercury problem in these times, one has only to consider the enormous loss rates. From the total of 2865 tons of mercury purchased in the U.S. in 1968, 76% or 2160 tons were lost to the environment. According to calculations of Kemp et al. (1974), the Lake Ontario reservoir contained a mass of 500 to 600 metric tons of "excess" mercury, i.e. discharged from anthropogenic sources. With the improvements in the methods of chlor-alkali electrolysis and by subsequent purification of waste streams the mercury loss has been reduced from 100 g per metric ton of manufactured chlorine to approx. 2 g per ton or less (Anon., 1973). The effect of these measures can be seen from concentration profiles of mercury in sediment cores taken off the mouth of Niagara River by Mudroch (1983), where a very distinct decrease from formerly approx. 4-7 ug Hg/g to less than lug Hg/g in recent years has occurred (Figure 2-6). 

---