Environment Canada, 45 Alderney Drive, Queen Square, Dartmouth, NS, B2Y 2N6, Canada.
Sci Total Environ. 2011 Feb 1;409(5):868-82. doi: 10.1016/j.scitotenv.2010.11.011. Epub 2010 Dec 16.
To minimize the risk posed by runoff from row crops, Prince Edward Island introduced buffer legislation in 2000. The legislation mandates 10-m and 20-m buffers, respectively, for moderate sloped (i.e. <5%) and steep sloped (i.e. >5%) agricultural fields that border streams. Since 2001, Environment Canada has been evaluating the effectiveness of various buffer widths on operational farms in reducing toxicity and contaminant concentrations in runoff. Sample collectors, placed in 44 fields at the field edge (0m), 10m and at distances out to 30m, collected overland flow following rainfall-induced runoff events. Samples were collected within 24 hours of an event and analysed for seven pesticides (endosulfan, chlorothalonil, carbofuran, linuron, metribuzin, metalaxyl, mancozeb), water quality parameters and Daphnia magna toxicity. The 10-m buffer required for moderate sloped fields was effective at reducing contaminant concentrations but not always to less than lethal concentrations to Daphnia magna. Limited data beyond 10m for fields of both slope types precluded making recommendations on a suitable buffer width for shallow sloped fields and evaluating the effectiveness of 20-m buffers for steep sloped fields. When paired data were combined and statistically tested for all fields, the studied pesticides underwent a 52-98% and 68-100% reduction in aqueous and particulate concentrations within 10m and 30m, respectively. In addition, by 10m, soluble phosphorus, nitrate-nitrogen and total suspended solids were reduced by 34%, 38% and 64%, respectively. Results suggest buffer zones on operational farms are capable of achieving contaminant reductions comparable to those reported for controlled experiments. Inconsistent siting of sample collectors beyond 10m limited the evaluation of the effects of field slope and buffer width on buffer effectiveness on working farms. Future studies on buffer efficiency on operational farms should focus on building the data set beyond 10m and evaluating load reductions.
为了最大限度地降低农作物径流带来的风险，爱德华王子岛于 2000 年出台了缓冲带法规。该法规规定，坡度在 5%以下的中度坡地和坡度在 5%以上的陡坡地的农田与溪流接壤时，需分别设置 10 米和 20 米的缓冲带。自 2001 年以来，加拿大环境部一直在评估不同缓冲带宽度在减少运营农场中径流毒性和污染物浓度方面的有效性。在降雨引发径流事件后，采样员在农田边缘（0 米）、10 米和 30 米处的 44 个田块中放置样本收集器，收集地表径流。事件发生后 24 小时内采集样本，分析七种农药（硫丹、百菌清、克百威、氯脲、二甲戊灵、甲霜灵、代森锰锌）、水质参数和大型蚤毒性。对于中度坡地，10 米宽的缓冲带可以有效降低污染物浓度，但并不总能将污染物浓度降低到对大型蚤无毒的水平。由于两种坡度类型的农田超过 10 米的数据有限，无法为浅坡农田推荐合适的缓冲带宽度，也无法评估 20 米宽的陡坡农田的缓冲带效果。当对所有农田的数据进行合并和统计检验时，研究中的农药在 10 米和 30 米处的水相和颗粒相浓度分别降低了 52%-98%和 68%-100%。此外，在 10 米处，可溶性磷、硝酸盐氮和总悬浮物分别减少了 34%、38%和 64%。结果表明，运营农场的缓冲带能够实现与对照实验报告的相当的污染物减少。由于超过 10 米处的样本收集器位置不一致，限制了对工作农场中农田坡度和缓冲带宽度对缓冲带有效性的影响的评估。未来在运营农场进行的关于缓冲带效率的研究应重点在 10 米以外的范围内建立数据集并评估负荷削减。
