National Exposure Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, OH 45268, USA.
Environ Manage. 2010 Feb;45(2):336-50. doi: 10.1007/s00267-009-9401-x. Epub 2009 Dec 3.
The Little Miami River (LMR) basin, dominated by agriculture, contains two geologically-distinct regions; a glaciated northern till plain with soils three times more permeable than a southern, pre-Wisconsinan drift plain. The influences of two landscape measures, percent row crop cover (%RCC, computed at three spatial scales), and soil permeability (PERM), on baseflow nutrient concentrations were modeled using linear regressions. Quarterly water samples collected for four years were analyzed for nitrate-N (NN), Kjeldahl-N (KN), total-N (TN), and total-P (TP). In till plain streams (n = 17), NN concentrations were 8.5-times greater than drift plain streams (n = 18), but KN and TP were 20-40% lower at comparable %RCC. These differences resulted in TN/TP molar ratios >80 in till plain streams, but <6 in drift plain streams. For till plain steams regression models based on %RCC accounted for 79% of the variance in NN concentrations but only 27% in drift plain streams. However, regressions on %RCC accounted for 68-75% of the KN and TP concentration variance in the drift plain streams but essentially none in the till plain. Catchment PERM influenced the regional NN/KN ratios which were 10-fold higher in the drift plain streams. For both till and drift streams the catchment scale %RCC gave the best predictions of NN, a water soluble anion, but the smaller spatial scales produced better models for insoluble nutrient species (e.g., KN and TP). Published literature on Ohio streams indicates that these inter-regional differences in nutrient ratios have potential implications for aquatic biota in the receiving streams.
小迈阿密河流域（LMR）以农业为主，包含两个地质上不同的区域；北部为冰川作用形成的冰碛平原，土壤渗透率是南部前威斯康星漂移平原的三倍。使用线性回归模型，对两种景观措施（行作物覆盖率百分比（%RCC）和土壤渗透率（PERM））对基流养分浓度的影响进行建模。在四年间，每季度采集水样进行硝酸盐-N（NN）、凯氏氮（KN）、总氮（TN）和总磷（TP）分析。在冰碛平原溪流（n = 17）中，NN 浓度比漂移平原溪流（n = 18）高 8.5 倍，但在可比的 %RCC 下，KN 和 TP 低 20-40%。这些差异导致 TN/TP 摩尔比在冰碛平原溪流中>80，但在漂移平原溪流中<6。对于冰碛平原溪流，基于 %RCC 的回归模型解释了 NN 浓度方差的 79%，但在漂移平原溪流中仅解释了 27%。然而，在漂移平原溪流中，%RCC 的回归解释了 KN 和 TP 浓度方差的 68-75%，而在冰碛平原溪流中几乎没有。集水区 PERM 影响区域 NN/KN 比，漂移平原溪流中的比值高 10 倍。对于冰碛和平原溪流，流域尺度的 %RCC 对 NN（一种水溶性阴离子）的预测最佳，但较小的空间尺度对不溶性养分物质（如 KN 和 TP）的模型更好。俄亥俄州溪流的文献表明，这些养分比率的区域差异可能对受纳溪流中的水生生物群具有潜在影响。
