Mineral contributions to atrazine and alachlor sorption in soil mixtures of variable organic carbon and clay content

• Published in: Journal of contaminant hydrology 1993-09, Vol.14 (2), p.117-128
• Main Authors: Grundl, Tim, Small, Greg
• Format: Article
• Language: English
• Subjects: ALACHLOR; ALACHLORE; ALACLORO; ATRAZINA; ATRAZINE; CARBON; CARBONE; CARBONO; CLAY MINERALS; CONTAMINANTES; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Hydrogeology; Hydrology. Hydrogeology; MINERAL ARGILEUX; MINERALES DE ARCILLA; POLLUANT; POLLUTANTS; Pollution, environment geology; SOIL SORPTION; SORCION DEL SUELO; SORPTION DU SOL
• ISSN: 0169-7722; 1873-6009
• DOI: 10.1016/0169-7722(93)90034-P

A sediment mixing approach was taken to systematically vary the organic carbon (oc) and clay content (cm) of a suite of organic-poor, clay-rich sediments. Organic carbon content ranged from 3.2% to 0.4% and clay content ranged from 24% to 51%. Atrazine and alachlor were shown to sorb to both natural organic carbon and clay minerals. Partition coefficients to natural organic carbon ( K oc) were found to be 217 and 412 L/kg organic carbon for atrazine and alachlor, respectively. Partition coefficients to the clay fraction were found to be 3.5 and 4.9 L/kg clay for atrazine and alachlor, respectively. When expressed in terms of surface area, the partition coefficients to clay for atrazine and alachlor were 1.80·10 −5 and 2.51·10 −5 L/m 2 clay, respectively. Critical cm/oc ratios at which mineral phase sorption accounts for 50% of the total are defined. Implications for the modelling of herbicide movement in the subsurface if mineral phase sorption is ignored is discussed.