Kroeger Kevin D, Cole Marci L, York Joanna K, Valiela Ivan
Boston University Marine Program, Marine Biological Laboratory, Woods Hole, MA 02543, USA.
Ground Water. 2006 Mar-Apr;44(2):188-200. doi: 10.1111/j.1745-6584.2005.00130.x.
We developed, and applied in two sites, novel methods to measure ground water-borne nitrogen loads to receiving estuaries from plumes resulting from land disposal of waste water treatment plant (WWTP) effluent. In addition, we quantified nitrogen losses from WWTP effluent during transport through watersheds. WWTP load to receiving water was estimated as the difference between total measured ground water-transported nitrogen load and modeled load from major nitrogen sources other than the WWTP. To test estimated WWTP loads, we applied two additional methods. First, we quantified total annual waste water nitrogen load from watersheds based on nitrogen stable isotopic signatures of primary producers in receiving water. Second, we used published data on ground water nitrogen concentrations in an array of wells to estimate dimensions of the plume and quantify the annual mass of nitrogen transported within the plume. Loss of nitrogen during transport through the watershed was estimated as the difference between the annual mass of nitrogen applied to watersheds as treatment plant effluent and the estimated nitrogen load reaching receiving water. In one plume, we corroborated our estimated nitrogen loss in watersheds using data from multiple-level sampling wells to calculate the loss of nitrogen relative to a conservative tracer. The results suggest that nitrogen from the plumes is discharging to the estuaries but that substantial nitrogen loss occurs during transport through the watersheds. The measured vs. modeled and stable isotopic approaches, in comparison to the plume mapping approach, may more reliably quantify ground water-transported WWTP loads to estuaries.
我们开发了新方法，并在两个地点应用，以测量因污水处理厂（WWTP）废水土地处置产生的羽流中进入受纳河口的地下水携带的氮负荷。此外，我们还对污水处理厂废水在流域输送过程中的氮损失进行了量化。污水处理厂对受纳水体的负荷估计为实测的地下水输送氮总负荷与除污水处理厂外主要氮源的模拟负荷之差。为了检验估计的污水处理厂负荷，我们应用了另外两种方法。首先，我们根据受纳水体中初级生产者的氮稳定同位素特征，对流域的年度废水总氮负荷进行了量化。其次，我们利用一系列井中地下水氮浓度的已发表数据来估计羽流的范围，并量化羽流中每年输送的氮质量。流域输送过程中的氮损失估计为作为处理厂废水施用于流域的氮年质量与到达受纳水体的估计氮负荷之差。在一个羽流中，我们利用多级采样井的数据来计算相对于保守示踪剂的氮损失，从而证实了我们对流域氮损失的估计。结果表明，羽流中的氮正在排入河口，但在流域输送过程中发生了大量氮损失。与羽流测绘方法相比，实测与模拟以及稳定同位素方法可能更可靠地量化地下水输送的污水处理厂对河口的负荷。
