Cadmium surface water

The calculation of the (001) cadmium-surface-water interface used a hexagonal unit cell with a c lattice constant of 135 a.u., and an a lattice constant of 33.788 a.u., corresponding to 36 cadmium atoms in the surface layer. The Cd slabs were 5 layers thick (perpendicular to the c-axis), for a total of 180 cadmium atoms per unit cell. The region between the slabs was filled with 525 water molecules. The plane wave expansion of the electron eigenstates had a cutoff of 9 Ry, giving 20,209 basis functions. Calculational details are described in reference [52]. 

In landfills, heavy metals have the potential to leach slowly into soil, groundwater, or surface water. Dry cell batteries contribute about 88% of the total mercury and 50% of the cadmium in the MSW stream. In the past, household batteries accounted for nearly half of the mercury used in the United States and over half of the mercury and cadmium in the MSW stream. When burned, some heavy metals such as mercury may vaporize and escape into the air, and cadmium and lead may end up in the ash. 

Hall, L.W., Jr., M.C. Scott, and W.D. Killen. 1998. Ecological risk assessment of copper and cadmium in surface waters of Chesapeake Bay watershed. Environ. Toxicol. Chem. 17 1172-1189. 

Cadmium is found naturally deep in the subsurface in zinc, lead, and copper ores, in coal, shales, and other fossil fuels it also is released during volcanic activity. These deposits can serve as sources to ground and surface waters, especially when in contact with soft, acidic waters. Chloride, nitrate, and sulfate salts of cadmium are soluble, and sorption to soils is pH-dependent (increasing with alkalinity). Cadmium found in association with carbonate minerals, precipitated as stable solid compounds, or coprecipitated with hydrous iron oxides is less likely to be mobilized by resuspension of sediments or biological activity. Cadmium absorbed to mineral surfaces (e.g., clay) or organic materials is more easily bioaccumulated or released in a dissolved state when sediments are disturbed, such as during flooding. 

Spencer, M.3., Piotrowicz, S.R. and Betzer, P.R., 1982. Concentrations of cadmium, copper, lead and zinc in surface waters of the northwest Atlantic Ocean - a comparison of Go-Flo and teflon water samplers. Mar. Chem., 11 403-410. 

Evidence has been detected of the biomethylation of cadmium. Studies with differential pulse anodic stripping voltammetry have shown detectable amounts of monomethylcadmium ion, H3CCd+, in surface water of the South Atlantic.5 Examination of water from some Arctic meltwater ponds showed that up to half of the cadmium present in the water was in the monomethylcadmium ion form. 

O Day, P.A., Carroll, S.A., and Waychunas, G.A., Rock-water interactions controlling zinc, cadmium, and lead concentration in surface waters and sediments, U.S. tri-state mining district. 1. Molecular identification using x-ray absorption spectroscopy, Environ. Sci. Technol., 32, 943, 1998. 

In the early 1960s, over 19,000 municipal water systems had been identified. These systems drew surface waters for treatment into drinking water. At this time, however, federal water pollution control efforts revealed that chemical and industrial wastes had polluted many surface waterways. Thus, the 1962 standards provided the addition of more recommended maximum limiting concentrations for various substances such alkyl benzene sulfonate, barium, cadmium, carbon-chloroform extract, cyanide, nitrate, and silver. 

Trace metals for which active biological assimilation may be an important factor in controlling surface-water concentrations and distributions include the first-row transition metals iron, zinc, manganese, copper, nickel, and cobalt, along with cadmium. Bruland et al. (1991) compiled data on the composition of plankton in... 

Cadmium is taken up by phytoplankton slightly preferentially to PO4 (Loscher et al, 1998 Elderfield and Rickaby, 2000). Waters with low PO4 concentrations thus have lower Cd PO ratios (0.1 nmolCd per p,mol PO4) than waters with higher PO4 concentrations where Cd POJ may approach 0.4 nmol Cd per p,mol PO (Elderfield and Rickaby, 2000). Additionally, surface water Cd PO4 ratios drop over the development of the spring bloom in the Southern Ocean (Loscher et al, 1998). 

Cadmium in seawater has a nutrient-like profile, with depleted values in warm surface waters, and... 

Lea and Boyle (1989) showed that the barium content in foraminifera shells is, like cadmium, controlled by the barium content in bottom waters. Barium, in a broad sense, also cycles like a nutrient (depleted in surface waters, and higher in deep waters), but its regeneration occurs deeper than the organic matter. This results in a close correlation between barium and alkalinity in today s ocean (Lea, 1993). Like Cd/Ca, Ba/Ca in foraminifera has also been used, as a paleo-tracer of water masses (e.g.. Lea and Boyle (1990), but suffers the same carbonate-saturation-state-linked effect as Cd/Ca (McCorkle et al., 1995). 

Hem J. D. (1972) Chemistry and occurrence of cadmium and zinc in surface water and ground water. Water Resour. Res. 8, 661-679. 

Data obtained on Legs 1 and 2 are presented in Table II. Concentrations were calculated by comparison with an added standard which increased the concentrations of the samples by 2.0 X 10" M cadmium and 2.0 X 10" M lead. Results for measurements which were not followed by standard additions were estimated by interpolating between bracketing standard additions. The concentration levels are those generally expected for open-ocean water (13). Lead values are somewhat higher than those of Southern Cahfomia surface waters recently measured by isotope dilution (10), but it must be noted that these data were not corrected for an analysis T)lank, which in our system may include... 

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