title: Sorption of chlorimuron-ethyl on montmorillonite clays: effects of exchangeable cations, pH, and ionic strength.
abstract: Sorption interaction of chlorimuron-ethyl with montmorillonite clays was investigated under varied types of exchangeable cation, pH, and ionic strength conditions. Chlorimuron-ethyl sorption on bentonites exhibited pronounced cation dependency, and the sorption ability increased as the sequence Ca(2+)- < Na(+)- < Al(3+)- < Fe(3+)-bentonite, due to different sorption mechanisms, whereas the cation dependency was influenced by the clay type and much weaker for montmorillonites. The decrease of pH at the range of 4.0-6.0 prominently increased sorption of chlorimuron-ethyl on all cation-exchanged montmorillonite clays, and nearly a neglected sorption (about 2 %) can be observed at pH over 7.0. In the presence of CaCl2, sorption of chlorimuron-ethyl on Fe(3+)-bentonite was promoted because of complexion of Ca(2+) and the surface of Fe(3+)-bentonite. However, as the concentration of CaCl2 increased, chlorimuron-ethyl sorption on Ca(2+)- and Fe(3+)-exchanged bentonite decreased, suggesting that Ca bridging was not the prevailing mechanism for sorption of chlorimuron-ethyl on these clays. Furthermore, chlorimuron-ethyl sorption was relatively sensitive to pH, and the change of pH may obscure effect of other factors on the sorption, so it was quite necessary to control pH at a constant value when the effect of other factor was being studied.
authors.affiliation: Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China.
authors.forename: Wenjie
authors.initials: W
authors.lastname: Ren
authors.forename: Ying
authors.initials: Y
authors.lastname: Teng
authors.forename: Qixing
authors.initials: Q
authors.lastname: Zhou
authors.forename: Albrecht
authors.initials: A
authors.lastname: Paschke
authors.forename: Gerrit
authors.initials: G
authors.lastname: Schüürmann
mesh_terms: D000327:Adsorption; D000535:Aluminum / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D001546:Bentonite / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D000077215:Clay; D006540:Herbicides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry; D009994:Osmolar Concentration; D011743:Pyrimidines / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry*; D013453:Sulfonylurea Compounds / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D006540:Herbicides; D011743:Pyrimidines; D012989:Soil Pollutants; D013453:Sulfonylurea Compounds; D001546:Bentonite; D012964:Sodium; C112343:chlorimuron ethyl; D000535:Aluminum; D007501:Iron; D002118:Calcium; D000077215:Clay