Farenhorst A, Londry K L, Nahar N, Gaultier J
Department of Soil Science, University of Manitoba, Winnipeg, Canada.
J Environ Sci Health B. 2008 Feb;43(2):113-9. doi: 10.1080/10934520701781160.
This study was undertaken to assess 2,4-D mineralization in an undulating cultivated field, along a sloping transect (458 m to 442 m above sea level), as a function of soil type, soil microbial communities and the sorption of 2,4-D to soil. The 2,4-D soil sorption coefficient (Kd) ranged from 1.81 to 4.28 L kg(-1), the 2,4-D first-order mineralization rate constant (k) ranged from 0.04 to 0.13 day(-1) and the total amount of 2,4-D mineralized at 130 days (M(130)) ranged from 24 to 39%. Both k and M(130) were significantly negatively associated (or correlated) with soil organic carbon content (SOC) and Kd. Both k and M(130) were significantly associated with two fatty-acid methyl esters (FAME), i17:1 and a18, but not with twenty-two other individual FAME. Imperfectly drained soils (Gleyed Dark Grey Chernozems) in lower-slopes showed significantly lesser 2,4-D mineralization relative to well-drained soils (Orthic Dark Grey Chernozems) in mid- and upper-slopes. Well-drained soils had a greater potential for 2,4-D mineralization because of greater abundance and diversity of the microbial community in these soils. However, the reduced 2,4-D mineralization in imperfectly drained soils was predominantly because of their greater SOC and increased 2,4-D sorption, limiting the bioavailability of 2,4-D for degradation. The wide range of 2,4-D sorption and mineralization in this undulating cultivated field is comparable in magnitude and extent to the variability of 2,4-D sorption and mineralization observed at a regional scale in Manitoba. As such, in-field variations in SOC and the abundance and diversity of microbial communities are determining factors that require greater attention in assessing the risk of movement of 2,4-D by runoff, eroded soil and leaching.
本研究旨在评估起伏耕地上2,4-滴的矿化情况，该耕地位于一个倾斜样带（海拔458米至442米），研究其作为土壤类型、土壤微生物群落以及2,4-滴在土壤中吸附作用的函数关系。2,4-滴的土壤吸附系数（Kd）范围为1.81至4.28升/千克，2,4-滴的一级矿化速率常数（k）范围为0.04至0.13天，130天时2,4-滴矿化的总量（M(130)）范围为24%至39%。k和M(13)均与土壤有机碳含量（SOC）和Kd显著负相关（或相关）。k和M(130)均与两种脂肪酸甲酯（FAME），即i17:1和a18显著相关，但与其他22种单个FAME无关。下坡处排水不良的土壤（潜育暗灰色黑钙土）相对于中坡和上坡处排水良好的土壤（直型暗灰色黑钙土），2,4-滴矿化明显较少。排水良好的土壤具有更大的2,4-滴矿化潜力，因为这些土壤中微生物群落的丰度和多样性更高。然而，排水不良土壤中2,4-滴矿化减少主要是由于其更高的SOC和2,4-滴吸附增加，限制了2,4-滴降解的生物可利用性。在这个起伏耕地上，2,4-滴吸附和矿化的广泛范围在幅度和程度上与在曼尼托巴省区域尺度上观察到的2,4-滴吸附和矿化的变异性相当。因此，SOC以及微生物群落的丰度和多样性的田间变化是在评估2,4-滴通过径流、侵蚀土壤和淋溶迁移风险时需要更多关注的决定因素。
