Department of Geography, Western University and Canadian Rivers Institute, 1151 Richmond Street, London, ON N6A 3K7, Canada.
Sci Total Environ. 2017 May 15;586:1124-1134. doi: 10.1016/j.scitotenv.2017.02.102. Epub 2017 Feb 17.
Temporal variation may influence the ability of best management practices (BMPs) to mitigate the loss of agricultural pollutants to streams. Our goal was to assess variation in mitigation effects of BMPs by examining the associations between instream nutrient concentrations and the abundance and location of four structural BMPs over a hydrologic year. Water samples were collected monthly (Nov. 2013-Oct. 2014) in 15 headwater streams representing a gradient of BMP use in Southern Ontario, Canada. Partial least squares (PLS) regression models were used to associate two groups of collinear nutrient forms with the abundance and location of BMPs, antecedent precipitation and time of year. BMP metrics in PLS models were associated with instream concentrations of major phosphorus forms and ammonium throughout the year. In contrast, total nitrogen and nitrate-nitrite were only associated with BMPs during snowmelt. BMP metrics associated with reductions of phosphorus and ammonium included greater abundances of riparian buffers and manure storage structures, but not livestock restriction fences. Likewise, the abundance and location riparian vegetation in areas capturing more surface runoff were associated with decreased stream nitrogen concentrations during snowmelt. However, the amount of tile drainage was associated with increased nitrogen concentrations following snowmelt, as well as with greater phosphorus and ammonium concentrations throughout the year. Overall, our findings indicate that increasing the abundance of riparian buffers and manure storage structures may decrease instream nutrient concentrations in agricultural areas. Additionally, the implementation of these structural BMPs appear to be an effective year-round strategy to assist management objectives in reducing phosphorus concentrations in small agricultural streams and thus loadings to downstream tributaries. Further mitigation measures, such as managerial BMPs and controlled tile drainage, may be required to further reduce instream nutrient concentrations during baseflow periods and snowmelt events.
时间变化可能会影响最佳管理实践（BMP）减轻农业污染物向溪流流失的能力。我们的目标是通过检查溪流中养分浓度与四种结构 BMP 的丰度和位置之间的关系，评估 BMP 缓解效果的变化，以了解水文年内 BMP 的缓解效果。在 2013 年 11 月至 2014 年 10 月期间，我们在加拿大安大略省南部的 15 条源头溪流中每月采集一次水样，这些溪流代表了 BMP 使用的梯度。偏最小二乘（PLS）回归模型用于将两组共线性养分形式与 BMP 的丰度和位置、前期降水和年份相关联。PLS 模型中的 BMP 指标与全年溪流中主要磷形态和铵的浓度相关。相比之下，总氮和硝酸盐-亚硝酸盐仅与融雪期间的 BMP 相关。与磷和铵减少相关的 BMP 指标包括更丰富的河岸缓冲区和粪肥储存结构，但不包括牲畜限制围栏。同样，在截留更多地表径流的区域，河岸植被的丰度和位置与融雪期间溪流氮浓度的降低有关。然而，随着融雪后排水渠的数量增加，以及全年磷和铵浓度的增加，排水渠的数量与氮浓度的增加有关。总的来说，我们的研究结果表明，增加河岸缓冲区和粪肥储存结构的丰度可能会降低农业区的溪流养分浓度。此外，这些结构 BMP 的实施似乎是一种有效的全年策略，可以帮助管理目标减少小型农业溪流中的磷浓度，从而减少下游支流的负荷。可能需要进一步的缓解措施，如管理 BMP 和控制排水渠，以在基流期和融雪期间进一步降低溪流中的养分浓度。
