Cadmium concentrations in field collections

Cadmium concentrations in field collections of selected species of plants and animals... 

Table 1.2 Cadmium Concentrations in Field Collections of Selected Species of Plants... 

Table 1.2 (continued) Cadmium Concentrations in Field Collections of Selected Species of Plants and Animals (Values shown are in mg Cd/kg fresh weight [FW], dry weight [DW], or ash weight [AW].)... 

Field and laboratory studies were conducted to determine the levels of Cd, Pb, and HCBD in various samples collected from a swamp environment in Louisiana and to assess the toxicities of As, Cd, and Hg to two species of aquatic organisms (bluegills and crawfish) indigenous to this swamp [18]. Cadmium and Pb were present in almost all collected samples. Their concentrations in fish were below the action levels set by EPA for the protection of human health. However, hazardous levels of these two elements were found in samples of crawfish, vegetation, soil, sediment, and water to some extent. Low levels of HCBD were recorded in water and sediment samples. In bioassay studies, Hg was found to be the most toxic metal, while As was the least toxic. Between the two test organisms, blue-gills appeared to be more sensitive than crawfish. Mixtures of Cd with As or Hg resulted in a combined toxic effect which was simply additive. However, a synergistic effect was recorded with the mixtures of As and Hg. 

Several tests that could not be carried out in the field were completed in the laboratory within five hours after the samples were collected. These included chemical oxygen demand (COD), which was determined photometrically after oxidation of the oombustible organic material in chromate sulfuric add in the presence of silver sulfate. The nitrate concentration was calculated from the nitrite concentration determined photometrically employing the Griess Reaction after the reduction of the nitrate to nitrite by metallic cadmium. The nitrite-N concentration determined in the field was subtracted 6om the result to calculate the nitrate-N content of the water, which was then converted to the nitrate concentration by multiplication. Fluoride was determined photometrically based on the decoloration of Spadns reagent. 

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