Yu Zhiqiang, Sharma Samriti, Huang Weilin
Department of Environmental Sciences, Rutgers University, 14 College Farm Road, New Brunswick, New Jersey 08901-8551, USA.
Environ Toxicol Chem. 2006 Aug;25(8):1975-83. doi: 10.1897/05-478r.1.
Recent studies have indicated that soil organic matter (SOM) may consist of physically and chemically different fractions, including particulate organic matter (POM), such as black carbon and unburned coal materials. The present study examined the differential roles of three different SOM fractions isolated from a peat and a topsoil in the equilibrium sorption of the herbicide atrazine (ATZ). The SOM fractions isolated from the two samples included humic acids (HAs), base-extracted humin (HM), and POM after demineralization of HM. A batch technique was employed to measure both the nonequilibrium ATZ sorption on the original and HA samples and the equilibrium ATZ sorption and desorption. The results showed that the phase-distribution relationships measured under nonequilibrium conditions were more linear and had lower sorption-capacity parameters compared with their respective isotherms measured under equilibrium conditions. The sorption isotherms were variously nonlinear, with POM exhibiting the greatest organic carbon-normalized sorption capacity. There existed apparent sorption-desorption hysteresis for each sorbent-sorbate system. It appeared that the extracted HAs could facilitate hydrolysis of ATZ when the reaction time extended to 4 d or longer. The equilibrium sorptive behavior of the HAs therefore was not examined. The present study indicated that both original samples showed lower organic carbon-normalized sorption distribution coefficients compared with their respective SOM fractions, suggesting that a fraction of sorption sites in soil aggregates were not accessed by ATZ.
近期研究表明，土壤有机质（SOM）可能由物理和化学性质不同的组分构成，包括颗粒有机 matter（POM），如黑碳和未燃烧的煤炭物质。本研究考察了从泥炭和表层土壤中分离出的三种不同SOM组分在除草剂阿特拉津（ATZ）平衡吸附中的不同作用。从这两个样品中分离出的SOM组分包括腐殖酸（HAs）、碱提取胡敏素（HM）以及HM脱矿后的POM。采用批量技术测量了非平衡条件下ATZ在原始样品和HA样品上的吸附以及平衡条件下ATZ的吸附和解吸。结果表明，与在平衡条件下测量的各自等温线相比，在非平衡条件下测量的相分布关系更呈线性，且吸附容量参数更低。吸附等温线呈不同程度的非线性，POM表现出最大的有机碳归一化吸附容量。每个吸附剂 - 吸附质体系都存在明显的吸附 - 解吸滞后现象。当反应时间延长至4天或更长时，提取的HAs似乎能促进ATZ的水解。因此未考察HAs的平衡吸附行为。本研究表明，与各自的SOM组分相比，两个原始样品的有机碳归一化吸附分配系数均较低，这表明土壤团聚体中的一部分吸附位点未被ATZ占据。
