A method to evaluate pollutant loads from tile drains

The quantification of pollutant loads from agricultural non-point source pollution is difficult because: (1) there is no direct means of continuously recording pollutant concentration; (2) and available human resources and funds always limit sampling. For those reasons, sampling strategy and pollutant concentration interpolation methods are essential to estimate pollutant loads. In this study, a method was tested to evaluate pollutant loads using daily flow volume and daily mass load regression for nitrate-nitrogen, orthophosphate-phosphorous and atrazine. The method worked well for nitrate-nitrogen, but generally did not work well for either orthophosphate-phosphorous or atrazine. Nitrate-nitrogen load was calculated for several tile-monitoring stations based on this method. Results were compared with volume interpolation methods; the difference between the two methods is not significant at the 95% level of confidence. This method can provide a reliable estimate of nitrate-nitrogen loads where limited samples are available. This method was not successful with orthophosphate-phosphorous or atrazine.