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Biodegradation of 2,4‐D in a Noncontaminated Grassland Soil Profile
Author(s) -
Shaw Liz J.,
Burns Richard G.
Publication year - 1998
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1998.00472425002700060024x
Subject(s) - subsoil , biodegradation , mineralization (soil science) , topsoil , environmental chemistry , chemistry , bioremediation , soil contamination , zoology , soil water , environmental science , soil science , contamination , ecology , biology , organic chemistry
Prediction of groundwater contamination and the development of rational bioremediation strategies require a greater understanding of xenobiotic biodegradation at the soil profile scale. We studied 2,4‐dichlorophenoxyacetic acid (2,4‐D) biodegradation for up to 83 d in soil samples collected in 10‐cm depth increments from a noncontaminated soil profile (0–50 cm), and examined factors that influenced biodegradation in the subsoil (40–50 cm). For the four samples collected from 0 to 40 cm, total evolution of 14 CO 2 from 14 C‐ring‐ UL ‐2,4‐D (20 mg kg −1 , 0.25 MBq kg −1 ) was 50.02 to 60.46% (maximum rate = 4.84% d −1 at 10–20 cm) at the end of the mineralization phase. Subsoil (40–50 cm) mineralization was either 5.47% (maximum rate = 0.113% d −1 ) or 56.1% (maximum rate = 2.67% d −1 ) after 83 d. Enhanced mineralization of successive 2,4‐D applications was recorded in all topsoil (0–10 cm) samples and in the subsoil replicates that initially mineralized > 50%. Measurements of 2,4‐D disappearance and most probable number analysis corresponded well with the biodegradation data. Inoculation of subsoil with topsoil (10%) increased 2,4‐D mineralization in the 5% soil to > 50%, whereas amendment with N, P, K, and/or organic C sources (acetate, catechol, vanillin, 3,5‐dihydroxybenzoic acid) did not. We conclude that the subsoil contained a low number of unevenly distributed microorganisms capable of using 2,4‐D as a source of C and energy such that not all the subsamples had competent microorganisms present.