Sorption and desorption of herbicide MCPA in soils and sediments
2006
Hiller, E.,Univerzita Komenského, Bratislava (Slovak Republic). Prírodovedecká fakulta. Katedra geochémie | Sirotiak, M.,Slovenská technická univ., Trnava (Slovak Republic). Materiálovotechnologická fakulta. Katedra environmentálneho a bezpečnostného inžinierstva | Zemanová, L.,Univerzita Komenského, Bratislava (Slovak Republic). Prírodovedecká fakulta. Katedra geochémie | Bartaľ, M.,Výskumný ústav vodného hospodárstva, Bratislava (Slovak Republic). Národné referenčné laboratórium
We investigated the sorption-desorption behavior of acid herbicide MCPA (4-chloro-2-methylphenoxy acetic acid) in five soils (denoted as A1-5), three bottom sediments (S1-3) and in two river sediments (L1-2) at two initial concentrations in aqueous solution – C0 = 0.5 and 10 mg/L. Sorption and desorption of MCPA was measured by a batch equilibrium technique using analytical pure MCPA. There was no significant influence of the initial concentration of MCPA on its equilibrium distribution between soil/sediment and aqueous solution. The difference between distribution coefficient KD at C0 = 0.5 mg/L and KD at C0 = 10 mg/L was found only in the case of one bottom sediment (S2). Simple regression analysis between KD at C0 = 0.5 and 10 mg/L and soil/sediment properties indicated that the most important property which determined the variation in MCPA sorption is organic carbon (r = 0.885** and r = 0.921***, respectively). Similarly, the desorption of MCPA was inversely proportional to organic carbon content of the soils and sediments used (r = -0.821* and r = -0.888**). These observations showed that sorption-desorption behaviour of MCPA in soils and sediments was primarily controlled by organic components of the geosorbents used. Overall, the sorption extent of MCPA in soils and sediments was low (Psorp ≈ 5 - 53%; KD = 0.131 -2.827 L/kg) and desorption extent was relatively high (Pdes ≈ 11 - 52 %), especially in soils and sediments with the lower organic carbon content. The experimental results and calculated values of groundwater ubiquity score GUS and relative leaching potential index RLPI imply that MCPA is very mobile in all soils and has high potential to contaminate groundwater.
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