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首页> 外文期刊>Environmental Science & Technology >Measurement of DDT fluxes from a historically treated agricultural soil in Canada
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Measurement of DDT fluxes from a historically treated agricultural soil in Canada

机译：测量加拿大历史处理过的农业土壤中的滴滴涕通量

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Organochlorine pesticide (OCP) residues in agricultural soils are of concern due to the uptake of these compounds by crops, accumulation in the foodchain, and reemission from soils to the atmosphere. Although it has been about three decades since DDT was banned for agricultural uses in Canada, residues persist in soils of some agricultural areas. Emission of DDT compounds to the atmosphere from a historically treated field in southern Ontario was determined in fall 2004 and spring 2005. The Sigma DDTs concentration in the high organic matter (71%) soil was 19 +/- 4 mu g g(-1) dry weight. Concentration gradients in the air were measured at 5, 20, 72, and 200 cm above soil using glass fiber filter-polyurethane foam cartridges. Air concentrations of Sigma DDTs averaged 5.7 +/- 5.1 ng m(-3) at 5 cm and decreased to 1.3 +/- 0.8 ng m(-3) at 200 cm and were 60-300 times higher than levels measured at a background site 30 km away. Soil-air fugacity fractions, f(s)/(f(s) + f(a)), of p,p'-DDE, p,p'-DDD, and p,p'-DDT ranged from 0.42 to 0.91 using air concentrations measured above the soil and >= 0.99 using background air concentrations, indicating that the soil was a net source to the background air. Fractionation of DDT compounds during volatilization was predicted using either liquid-phase vapor pressures (P-L) or octanol-air partition coefficients (K-OA). Relative emissions of p,p'-DDE and p,p'-DDT were better described by P-L than K-OA, whereas either P-L or K-OA successfully accounted for the fractionation of p,p'-DDT and o,p'-DDT. Soil-to-air fluxes were calculated from air concentration gradients and turbulent exchange coefficients determined from micrometeorological measurements. Average fluxes of Sigma DDTs were 90 +/- 24 ng m(-2) h(-1) in fall and 660 +/- 370 ng m(-2) h(-1) in spring. Higher soil temperatures in spring accounted for the higher fluxes. A volatilization half-life of similar to 200 y was estimated for Sigma DDT in the upper 5 cm of the soil column, assuming the average flux rate for 12 h d(-1) over 8 months of the year. Thus, in the absence of other dissipation processes, the soil will continue to be a source of atmospheric contamination for a very long time.
机译：由于农作物对这些化合物的吸收，食物链中的积累以及从土壤中释放到大气中，农业土壤中的有机氯农药（OCP）残留受到关注。尽管从加拿大禁止滴滴涕用于农业用途已经过去了大约三十年，但残留物仍然存在于某些农业地区的土壤中。 2004年秋季和2005年春季确定了安大略省南部一个经过历史处理的田地向大气中排放的DDT化合物。高有机质（71％）土壤中Sigma DDTs的浓度为19 +/- 4 mu gg（-1）净重。使用玻璃纤维过滤器-聚氨酯泡沫滤芯在土壤上方5、20、72和200 cm处测量空气中的浓度梯度。 Sigma DDT的空气浓度在5厘米处平均为5.7 +/- 5.1 ng m（-3），在200厘米处降至1.3 +/- 0.8 ng m（-3），比背景测量的浓度高60-300倍网站距离30公里。 p，p'-DDE，p，p'-DDD和p，p'-DDT的土壤空气逸度分数f（s）/（f（s）+ f（a））为0.42至0.91使用土壤上方测得的空气浓度，使用背景空气浓度> = 0.99，表明土壤是背景空气的净源。使用液相蒸气压（P-L）或辛醇-空气分配系数（K-OA）可以预测挥发期间DDT化合物的分馏。 PL比K-OA更好地描述了p，p'-DDE和p，p'-DDT的相对排放，而PL或K-OA都成功地解释了p，p'-DDT和o，p'的分离-滴滴涕。根据空气浓度梯度和微气象测量确定的湍流交换系数来计算土壤对空气通量。 Sigma DDT的平均流量在秋季为90 +/- 24 ng m（-2）h（-1），在春季为660 +/- 370 ng m（-2）h（-1）。春季较高的土壤温度导致较高的通量。假设在一年中的8个月内12 h d（-1）的平均通量速率，在土壤柱上部5 cm处，Sigma DDT的挥发半衰期估计接近200 y。因此，在没有其他耗散过程的情况下，土壤将在很长一段时间内继续成为大气污染的来源。

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