Mbonimpa Eric G, Yuan Yongping, Nash Maliha S, Mehaffey Megan H
USEPA Office of Research and Development, Landscape Ecology Branch, Las Vegas, USA.
USEPA Office of Research and Development, Landscape Ecology Branch, Las Vegas, USA.
J Environ Manage. 2014 Jan 15;133:214-21. doi: 10.1016/j.jenvman.2013.11.030. Epub 2013 Dec 31.
Total phosphorous (TP) and total suspended sediment (TSS) pollution is a problem in the US Midwest and is of particular concern in the Great Lakes region where many water bodies are already eutrophic. Increases in monoculture corn planting to feed ethanol based biofuel production could exacerbate these already stressed water bodies. In this study we expand on the previous studies relating landscape variables such as land cover, soil type and slope with changes in pollutant concentrations and loading in the Great Lakes region. The Rock River watershed in Wisconsin, USA was chosen due to its diverse land use, numerous lakes and reservoirs susceptible to TSS and TP pollution, and the availability of long-term streamflow, TSS and TP data. Eight independent subwatersheds in the Rock River watershed were identified using United States Geological Survey (USGS) monitoring sites that monitor flow, TSS and TP. For each subwatershed, we calculated land use, soil type, and terrain slope metrics or variables. TSS and TP from the different subwatersheds were compared using Analysis of Variance (ANOVA), and associations and relationships between landscape metrics and water quality (TSS and TP) were evaluated using the partial least square (PLS) regression. Results show that urban land use and agricultural land growing corn rotated with non-leguminous crops are associated with TSS and TP in streams. This indicates that increasing the amount of corn rotated with non-leguminous crops within a subwatershed could increase degradation of water quality. Results showed that increase in corn-soybean rotation acreage within the watershed is associated with reduction in stream's TSS and TP. Results also show that forest and water bodies were associated with reduction in TSS and TP. Based on our results we recommend adoption of the Low Impact Development (LID) approach in urban dominated subwatersheds. This approach attempts to replicate the pre-development hydrological regime by reducing the ratio of impervious area to natural cover wherever possible, as well as recycling or treating stormwater runoff using filter strips, ponds and wetlands. In agriculturally dominated subwatersheds, we recommend increasing corn-soybean rotation, keeping corn on areas with gentle slope and soils with lower erodibility.
总磷（TP）和总悬浮固体（TSS）污染是美国中西部地区面临的一个问题，在五大湖地区尤为令人担忧，该地区许多水体已经处于富营养化状态。为满足基于乙醇的生物燃料生产而增加的单一栽培玉米种植可能会使这些本已压力重重的水体状况恶化。在本研究中，我们拓展了以往关于五大湖地区景观变量（如土地覆盖、土壤类型和坡度）与污染物浓度及负荷变化之间关系的研究。美国威斯康星州的岩石河流域因其土地利用多样、有众多易受TSS和TP污染的湖泊和水库，以及可获取长期的流量、TSS和TP数据而被选中。利用美国地质调查局（USGS）监测流量、TSS和TP的监测站点，在岩石河流域确定了8个独立的子流域。对于每个子流域，我们计算了土地利用、土壤类型和地形坡度指标或变量。使用方差分析（ANOVA）比较不同子流域的TSS和TP，并使用偏最小二乘（PLS）回归评估景观指标与水质（TSS和TP）之间的关联和关系。结果表明，城市土地利用以及种植与非豆科作物轮作玉米的农业用地与溪流中的TSS和TP有关。这表明在一个子流域内增加与非豆科作物轮作的玉米种植量可能会加剧水质恶化。结果显示，流域内玉米 - 大豆轮作面积的增加与溪流中TSS和TP的减少有关。结果还表明，森林和水体与TSS和TP的减少有关。基于我们的研究结果，我们建议在以城市为主的子流域采用低影响开发（LID）方法。这种方法试图通过尽可能降低不透水面积与自然覆盖面积的比例，以及使用过滤带、池塘和湿地对雨水径流进行再循环或处理，来重现开发前的水文状况。在以农业为主的子流域，我们建议增加玉米 - 大豆轮作，将玉米种植在坡度平缓且土壤侵蚀性较低的区域。
