Estimation of pollutant unit load of paddy fields with and without a rainfall factor

Abstract

The new guideline of the National Institute of Environmental Research (NIER) method for unit load estimation suggested using long‐term average annual precipitation, representative event mean concentrations (EMCs) of pollutants and runoff ratio in Korea. The guideline also suggested estimating the runoff ratio and EMCs for rainfall groups (0–10, 10–30, 30–50, above 50 mm) and rainfall weighting factor, to give a representative runoff ratio and EMC of a pollutant. The objective of this study is to evaluate the method suggested by the NIER. In this study, a 5‐year intensive field monitoring was carried out to determine pollutant load from paddy fields. The observed average annual pollutant losses from the studied paddy fields were compared to the unit load determined by three different methods. Overall, the method using the NIER guideline produced similar results to the method using arithmetic mean runoff ratio and EMC, which had been used for previous unit load determination. Meanwhile, the study revealed that estimation of unit load by the NIER method was closer to the observed unit load of pollutant from paddy fields than that by the method using EMCs from log‐normal and gamma distribution. Copyright © 2016 John Wiley & Sons, Ltd.

Determination of NPS Pollutant Unit Loads from Different Landuses

“…In particular, in the case of FL, the results showed that 42% of the total monitoring was performed in the 10-30 mm rainfall range, and most runoff did not occur in rainfall events below the 10 mm rainfall range. This is similar to the results of some other studies [20][21][22][23]. For the same reason, in PF, 36% of the total monitoring was performed in the rainfall range of 50 mm or more.…”

“…The calculated unit loads were higher than the existing unit loads for the agricultural landuse categories (i.e., UL and PF), and lower for BS. Figure 6 shows the BOD and TP unit load of the BS, PF, and UL landuse by year, and the unit load results of domestic studies from 2000 to 2014 [6,23,[26][27][28][29][30][31][32][33][34][37][38][39][40][44][45][46][47][48], the existing unit load (red), and the unit load calculated in this study (blue) are displayed together. BS, which represents urban areas, shows a tendency for BOD and TP unit load to decrease over time (Figure 6a, b).…”