Leaching potential of nonsteroidal anti-inflammatory drugs in soils

Nonsteroidal anti-inflammatory drugs (NSAIDs) in soils resulting from application of municipal wastewater or biosolids may migrate through soils intact or be transformed and reach groundwater. In the present study, the leaching potential of four NSAIDs (ibuprofen, naproxen, ketoprofen, and diclofenac sodium) in three U.S. cropland soils was evaluated, and the effect of CaCl(2) solution (as an index of salinity), dissolved organic matter (DOM), and polyacrylamide (PAM) amendment was investigated. The soils were spiked with selected NSAIDs, incubated for 24 h followed by 7-d storage in glass flasks, and then packed into stainless steel columns and leached with deionized water (DIW), 10 mM CaCl(2), DOM (DOC 34 mg/L), and PAM solution (1.0 mg/L) by gravity. Initial concentrations of ibuprofen, naproxen, ketoprofen, and diclofenac sodium in the three packed soils were 1.93 to 2.07, 1.74 to 2.27, 1.79 to 2.16, and 1.99 to 2.13 mg/kg, respectively. Maximum concentrations of the above NSAIDs in column effluents were 1.23, 0.92, 0.69, and 1.12 mg/L, respectively, when the soil was leached with 10 pore volumes of water, which occupied 17.4, 11.1, 9.6, and 15.2% of the total chemicals in each soil column. Dissolved organic matter or PAM solution did not facilitate the NSAIDs release from soils. The CaCl(2) solution, however, reduced the amounts of NSAIDs leached from all three soils. Leaching of NSAIDs differed among the three tested soils. The results suggest that the leaching of NSAIDs through soil to water is significant, and the mobility of NSAIDs in soil is related to their chemicals' characteristics (such as pK(a) values) and soil properties (such as soil organic matter and clay content). Amending soil with DOM or PAM does not significantly affect the leaching behavior of NSAIDs in soil, whereas increasing the salinity of the irrigation water may decrease the extent of contamination of groundwater posed by NSAIDs.