Gaultier Jeanette, Farenhorst Annemieke, Cathcart Jason, Goddard Tom
Dep. of Soil Science, Univ. of Manitoba, Winnipeg, MB, Canada R3T 2N2.
J Environ Qual. 2008 Aug 8;37(5):1825-36. doi: 10.2134/jeq2007.0578. Print 2008 Sep-Oct.
Sorption and degradation of the herbicide 2,4-D [2,4-dichlorophenoxyacetic acid] were determined for 123 surface soils (0 to 15 cm) collected in 2002 and in 2004 between 49 degrees to 60 degrees north longitude and 110 degrees to 120 degrees west latitude in Alberta, Canada. The soils were characterized by soil organic carbon content (SOC), pH, electrical conductivity, soil texture, cation exchange capacity, carbonate content, and total soil microbial activity. The 2,4-D sorption coefficients, Kd and Koc, were highly variable with coefficients of variation of 89 and 59%, respectively, at the provincial scale. Both Kd and Koc were well described by regression models with SOC and soil pH as variables, regardless of scale. Surprisingly, variations in 2,4-D mineralization were much smaller than variations in sorption. Variability in total 2,4-D mineralization was particularly low, with a coefficient of variation of only 7% at the provincial scale. Average 2,4-D half-lives in ecoregions ranged from 1.7 to 3.5 d, much lower than the field dissipation half-life of 10 d reported for 2,4-D in general pesticide property databases. Regression models describing degradation parameters were generally poor or not significant because 2,4-D mineralization was only weakly associated with measured 2,4-D sorption parameters and soil properties. As such, regional variations in herbicide sorption coefficients should be measured or calculated based on soil properties, to assign distinct pesticide fate model input parameters when estimating 2,4-D off-site transport at the provincial scale. Spatial variations in herbicide degradation appear less important for Alberta as 2,4-D half-lives were similar in soils across the province. The rapid mineralization of 2,4-D is noteworthy because 2,4-D is widely used in Alberta and perhaps adaptation of soil microbial communities allowed for accelerated degradation regardless of soil properties or the extent of 2,4-D sorption by soil.
对2002年和2004年在加拿大艾伯塔省北纬49度至60度、西经110度至120度之间采集的123份表层土壤（0至15厘米）进行了除草剂2,4 - D[2,4 - 二氯苯氧乙酸]的吸附和降解测定。这些土壤通过土壤有机碳含量（SOC）、pH值、电导率、土壤质地、阳离子交换容量、碳酸盐含量和土壤总微生物活性进行表征。在省级尺度上，2,4 - D的吸附系数Kd和Koc变化很大，变异系数分别为89%和59%。无论尺度如何，Kd和Koc都能通过以SOC和土壤pH值为变量的回归模型很好地描述。令人惊讶的是，2,4 - D矿化的变化远小于吸附的变化。2,4 - D总矿化的变异性特别低，在省级尺度上变异系数仅为7%。生态区域内2,4 - D的平均半衰期在1.7至3.5天之间，远低于一般农药特性数据库中报道的2,4 - D田间消散半衰期10天。描述降解参数的回归模型通常较差或不显著，因为2,4 - D矿化仅与测得的2,4 - D吸附参数和土壤性质弱相关。因此，在省级尺度上估算2,4 - D的场外迁移时，应根据土壤性质测量或计算除草剂吸附系数的区域差异，以指定不同的农药归宿模型输入参数。除草剂降解的空间差异对艾伯塔省似乎不太重要，因为全省土壤中2,4 - D的半衰期相似。2,4 - D的快速矿化值得注意，因为2,4 - D在艾伯塔省广泛使用，也许土壤微生物群落的适应性使得无论土壤性质或土壤对2,4 - D的吸附程度如何，降解都能加速。
