Distribution of mercury in soil and its concentration in runoff from a biosolids-amended agricultural watershed.
Biosolids applications can significantly increase Hg concentrations in cultivated soils. The objective of this study was to quantify levels of mercury in soils and runoff from a biosolids-amended watershed. The study site was a terraced, cultivated watershed that received cumulative biosolids loadings of 0, 87, or 224 Mg ha(-1) between 1974 and 1993. Snowmelt runoff samples were collected from the three treatment areas in the spring of 1995. Soils were collected along transects from the 0 and 224 Mg ha(-1) biosolids treatment areas at depths of 0 to 15 and 15 to 30 cm. Mercury analysis of stored, freeze-dried biosolids samples showed that Hg concentrations during the 20-year study ranged from 12.4 mg kg(-1) initially to 2.4 mg kg(-1) near the end. Soil Hg concentrations were elevated in the surface (0-15 cm) and subsurface (15-30 cm) of the 224 Mg ha(-1) biosolids-treated terrace relative to the control. Mercury concentrations in the 0- to 15-cm soil depth ranged from 30 to 50 microg kg(-1) for the control terrace and 180 to 390 microg kg(-1) for the 224 Mg ha(-1) biosolids-treated terrace. Concentrations were lower in the 15- to 30-cm depth. Total Hg concentrations in snowmelt from the control terrace ranged from 9.2 to 27.9 ng L(-1) and 19.8 to 44.8 ng L(-1) for the biosolids-treated terraces. Most Hg was associated with particulates > 0.45 microm. Mercury concentrations were elevated in grass tissue growing near the watershed's runoff lagoon.
Sloan
J J
JJ
Texas Agricultural Experiment Station, Texas A&M University, Dallas 75252-6599 USA. j-sloan@tamu.edu
Dowdy
R H
RH
Balogh
S J
SJ
Nater
E
E
D000383:Agriculture; D001682:Biological Availability; D003247:Conservation of Natural Resources; D004784:Environmental Monitoring; D008372:Manure; D008628:Mercury / Q000032:analysis*; D006109:Poaceae / Q000737:chemistry; D011891:Rain; D012914:Snow; D012989:Soil Pollutants / Q000032:analysis*; D014018:Tissue Distribution; D014872:Water Movements; D014873:Water Pollutants / Q000032:analysis*
D008372:Manure; D012989:Soil Pollutants; D014873:Water Pollutants; D008628:Mercury