Arsenic in Soil and Runoff From Poultry Litter-Amended Grasslands.

The use of organo-arsenical compounds such as roxarsone as feed additives in poultry diets is a potential environmental concern because these compounds appear in poultry litter, as do copper and zinc, which are also used in poultry feeds. Since poultry litter is surface applied to grasslands, significant amount of arsenic (As), copper (Cu), and zinc (Zn) may potentially contaminate surface runoff. The organic form of arsenic can be degraded to inorganic forms such as arsenite and arsenate which are more toxic than roxarsone. The objectives of this study were 1) to investigate total amounts of As, Cu, and Zn in soil from litter-amended, field-scale plots on tall fescue/bermudagrass; 2) to assess concentration of As in surface runoff from the same field-scale plots; and 3) to investigate concentrations of inorganic and organic species of arsenic in surface runoff from a rainfall simulation study with grassed plots. There was a significant difference in the amount of As in soil between poultry litter-amended plots and control plots. However, the concentrations of As, Cu, and Zn in poultry litter-amended soil were below USEPA loading limits for sewage sludge application. Analysis of surface runoff from poultry litter-amended plots showed that As concentration was greater than the USEPA drinking water standard (10 ug/L) immediately after poultry litter application and decreased over time. Results of the rainfall simulation study showed that concentrations of As in surface runoff were significantly greater from poultry-litter amended plots than from control plots. Inorganic As (arsenate) was the predominant species in runoff compared to organic species. The concentration of As in runoff was significantly greater immediately after litter application than after one, two, or four weeks, but in all cases was greater than the USEPA drinking water standard.