Effects of the geophagous earthworm Metaphire guillelmi on sorption, mineralization, and bound-residue formation of 4-nonylphenol in an agricultural soil

- The earthworm Metaphire guillelmi inhibited mineralization of 4-NP in the soil.
- A less-polar metabolite of 4-NP (2-nitro-4-NP111) was detected in the soil and cast.
- The presence of earthworm reduced the amount of 2-nitro-4-NP111 in the soil.
- M. guillelmi significantly reduced formation of bound residues of 4-NP in the soil.

Effects of earthworms on fate of nonylphenol (NP) are obscure. Using 14C-4-NP111 as a representative, we studied the fate of 4-NP in an agricultural soil with or without the earthworm Metaphire guillelmi and in fresh cast of the earthworm. Sorption of 4-NP on the cast (Kd 1564) was significantly higher than on the parent soil (Kd 1474). Mineralization of 4-NP was significantly lower in the cast (13.2%) and the soil with earthworms (10.4%) than in the earthworm-free soil (16.0%). One nitro metabolite of 4-NP111 (2-nitro-4-NP111) was identified in the soil and cast, and the presence of the earthworm significantly decreased its amounts. The presence of earthworm also significantly decreased formation of bound residues of 4-NP in the soil. Our results demonstrate that earthworms could significantly change the fate of 4-NP, underlining that earthworm effects should be considered when evaluating behavior and risk of 4-NP in soil.