Effect of oxygen status on pesticide transformation and sorption in undisturbed soil and lake sediment

• Published in: Environmental toxicology and chemistry Vol. 16; no. 4; pp. 608 - 616
• Main Authors: Vink, J.P.M. (RIZA, Lelystad, The Netherlands.), Zee, S.E.A.T.M. van der
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Periodicals, Inc 01.04.1997; SETAC
• Subjects: adsorptie; adsorption; ALDICARB; ALDICARBE; AMBIENTE ACUATICO; Applied sciences; Biological and physicochemical properties of pollutants. Interaction in the soil; Biotransformation; Environment; Exact sciences and technology; gewasbescherming; HERBICIDAS; HERBICIDE; Hydrologie; Hydrology; MCPA; microbial degradation; microbiële afbraak; MILIEU AQUATIQUE; OXIRREDUCION; OXYDOREDUCTION; Oxygen; persistence; persistentie; pesticide residues; pesticiden; pesticidenresiduen; pesticides; plant protection; Pollution; Redox; RIESGO; Risk assessment; RISQUE; SIMAZINA; SIMAZINE; Soil and sediments pollution; sorptie; sorption; water bottoms; waterbodems; Biodegradation; Sediment water interaction; Oxygen; Pollutant behavior; Medium effect; Pesticides; Redox potential; Lake sediments; Soil pollution
• ISSN: 0730-7268; 1552-8618
• DOI: 10.1002/etc.5620160402

The behavior of four chemically distinctly different pesticides (aldicarb, simazine, mecoprop, and phenoxic acid [MCPA] was investigated under simulated redox conditions that occur at the terrestrial-aqueous interface. Sorption was measured in soil and lake sediment and in pure and combined pesticide solutions to study effects of competition. Transformation was investigated in undisturbed soil microcolumns and in anaerobic lake sediment. Using an air-tight nitrogen incubator, oxygen concentrations were varied from 20.8% (ambient) to less then 0.01 % v/v O2, while redox potentials varied from +330 to -120 mV. Aldicarb was transformed more rapidly under anaerobic than under aerobic conditions. Under low oxygen conditions, both reductive and oxidative metabolites were formed. Simazine showed some reductive transformation, but the overall transformation rate decreased with decreasing O2 concentrations. A pronounced redox effect was shown for both mecoprop and MCPA. With decreasing oxygen concentrations, transformation rates decreased from 0.173 to less than 0.001 d-1, monitored over 200 d. These compounds, which are considered improbable leachers based on their short aerobic half lifes, appear to be more persistent in low-oxygenous conditions. It is shown that a period of oxygen inhibition could be survived by the responsible soil microorganisms and was followed by accelerated transformation of the compound when oxygen became abundant again. No relationship was observed between sorption affinity and transformation rate. The effect of redox conditions that occur along the pesticide's emission route appears to be an important screening parameter to assess environmental risks