Occurrence of arsenic and phosphorus in ditch flow from litter-amended soils and barn areas

Little is known about the fate of arsenic (As) in land-applied litter from chickens that have been fed roxarsone, an organic feed additive containing As. Th is study seeks to elucidate the transfer of As in runoff from ditch-drained soils of the poultryproducing region of the Delmarva Peninsula by tracking As and phosphorus (P) export from seven drainage ditches over two water-years (1 July 2005 to 30 June 2007). Annual losses of As from ditches ranged from 0.004 to 0.071 kg h^a-1 while P losses ranged from 0.33 to 18.56 kg h ^a-1, with the largest loads associated with a litter storage shed that served as a point source. Event-based As and P losses in ditch flow fluctuated by a factor of 162 and 1882, respectively. Th e two elements were correlated in flow from the ditch draining a litter storage shed (r = 0.99), and in sediment extracts in soils near the litter shed (r = 0.73), pointing to similar behavior under point source conditions. Indeed, As and P exhibited similar behavior within storms for all ditches, characterized by relatively high initial concentrations subject to rapid concentration declines before peak flow, consistent with dilution of a finite source. However, As and P concentrations varied significantly between ditches and showed considerable temporal variability within ditches, with no clear seasonal trends or associations with current management strategies. Th e results suggest that similar management strategies might be effective for As and P point sources, but that field management practices geared toward controlling nonpoint source P losses may not readily transfer to the control of As losses.