Non-point Source Pollution Discharge Research Articles

Distribution of antibiotic resistance genes in the sediments of Erhai Lake, Yunnan-Kweichow Plateau, China: Their linear relations with nonpoint source pollution discharges from 26 tributaries

Erhai Lake, a typical plateau deep water lake, experienced long-term nonpoint source (NPS) pollution discharge from 26 tributaries, which significantly affected the abundance and spread of resistance genes. In this study, 25 antibiotic resistance genes (ARGs), classified into six types, and NPS pollution discharges were investigated throughout around the Erhai basin. FCA (mexF) and sulfonamide resistance genes (sul1, sul2 and sul3) were the most common. Although the absolute overall abundance of ARGs there was low so far, the individual gene like sulfonamide resistance gene was high. Regression analysis using an ordinary least squares model (OLS) showed that the discharge of NPS pollution into Erhai Lake would have an obvious effect on the distribution of ARGs. And the relations between them were linear. Concretely speaking, the total nitrogen (TN) pollution input from tributaries could significantly correlated with the increasing of ARG abundance, while the total phosphorus (TP) pollution input showed the opposite correlation, and ultimately affect the distribution of ARGs. Moreover, the effect of TP on ARG distribution was more significant than TN. This study provides a geographical profile of ARG distribution in a subtropical deep lake on Yunnan-Kweichow Plateau. The results are beneficial for predicting the distribution characteristics of ARGs and controlling their pollution in plateau lakes.

Temporal-spatial analysis of water environmental capacity based on the couple of SWAT model and differential evolution algorithm

The objective of this study was to advance a new method to dynamically analyze the water environmental capacity (WEC) of non-point source (NPS) pollution. A Soil and Water Assessment Tool (SWAT) model and differential evolution (DE) algorithm were coupled to automatically provide a calculation of the WEC in a daily step. The results showed that the largest ideal WECs occurred in the wet season with values up to 4500 t and 80 t for total nitrogen (TN) and total phosphorus (TP), respectively. The ideal WEC had a positive correlation with the rainfall intensity, while the opposite was true for actual WEC. The smallest value of actual WEC for TN was −150 t in June, and a negative value also occurred in June for TP. This is because NPS pollution discharge was more sensitive to rainfall and flow change than the ideal WEC. Compared to phosphorus, the WEC of nitrogen was more affected by the hydrological and NPS pollution discharge conditions. In addition, the WEC of nitrogen and phosphorus in organic species was more affected by seasonal change than that of nitrogen and phosphorus in inorganic species. Spatially, the channels in the middle and southeast of the study area had the smallest actual WEC and even negative values were observed. The results of remnant WEC showed that the smallest value occurred in July and June with values of −800 t and −140 t for TN and TP, respectively. Thus, significant attention should be paid to controlling NPS pollution during the wet season, and organic nitrogen and phosphorus should be set as the priority pollutants to control. Furthermore, controlling the NPS pollution discharge and enhancing the WEC should be carried out simultaneously. Compared to previously used methods, the calculation method employed in this study had the ability to simulate the transformation and interaction between nitrogen and phosphorus in organic and inorganic species, and better considered dynamic changes in the input conditions.

Effect of System of Rice Intensification on Water Productivity and NPS Pollution Discharge

AbstractPaddy fields comprise the single largest land use in Korea, occupying nearly 60% of arable land, consuming about 56% of the nation's water supply, and discharging a significant amount of agricultural non‐point source (NPS) pollution to public waters. Rural water resources conservation, the improvement of irrigation water productivity (IWP) and the reduction of NPS pollution from paddy fields are important issues in Korea. To quantify the issue, a field‐size rice‐plot study was conducted for 3 years comparing the treatment of a system of rice intensification (SRI) irrigation management and a conventional practice (CT). The SRI reduced the irrigation requirement at field level by 50% compared to the CT. The IWP of the SRI improved by an average of 94% over that of the CT. The average reductions of the NPS pollutants by SRI was 44.4% (BOD), 38.6% (SS), 35.3% (CODMn), 28.3% (CODCr), 23.8% (TN) and 36.3% (TN). The SRI treatment was concluded to have contributed to healthy rice plant growth, improvement of IWP and reduction of agricultural NPS pollution from paddy fields, which could significantly conserve rural water resources and improve water quality in Korea. Copyright © 2016 John Wiley & Sons, Ltd.

Application of Surface Cover Materials for Reduction of NPS Pollution on Field‐Scale Experimental Plots

AbstractA 2‐year experimental plot study was conducted in Korea to measure the effect of different surface treatments on runoff and agricultural non‐point source (NPS) pollution. The treatments were straw mat conjunctive with polyacrylamide and gypsum (SPG), straw mat (SM) and plastic sheet (PM) mulches. Four plots on a sandy loam, mildly sloped (2–8.4%) soybean field were monitored with respect to runoff and water quality. Average annual rainfall was 1270 mm. Runoff reduction by the SPG and SM treatments ranged from 22.0 to 90.9% and from 50.0 to 68.1%, respectively, compared with runoff from the control. The SM treatment produced less runoff than did the PM treatment. Event mean concentrations did not show any consistent differences between the treatments except for suspended solids (SS), which were always lower than that from the control. The reduction of NPS pollution load by the SPG and SM treatments ranged between 27.6 and 95.0%, and between 38.7 and 96.7%, respectively. The SS reduction by the treatments ranged between 50.0 and 92.2%. The SPG and SM treatments were effective in the control of soil erosion, turbid runoff and other NPS pollution discharge. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of Surface Cover on NPS Pollution from Sloping Fields under Intensive Farming in Korea

AbstractSloping fields under intensive farming have been a major source of agricultural nonpoint source (NPS) pollution in Korea. Comprehensive studies to quantify edge‐of‐field water quality and measure surface mulch effects on NPS pollution discharge have been conducted over the past several years. Edge‐of‐field water quality was seriously degraded by NPS pollutants. The range of average event mean concentrations (EMCs) was suspended solids (SS) 547 ~ 2600 mg l−1, biochemical oxygen demand (BOD) 8.7 ~ 50.7 mg l−1, total nitrogen (TN) 3.5 ~ 21.8 mg l−1, and total phosphorus (TP) 2.4 ~ 13.1 mg l−1. Experiments treated by a rice straw mat mulch (S), S with gypsum (SG), and SG with PAM (SPG) showed good results as best management practices (BMPs) in controlling NPS pollution from sloping fields. The range of reductions by the treatments was runoff 28.3 ~ 96.7%, SS 71.5 ~ 99.5%, BOD 37.5 ~ 91.9%, TN 32.4 ~ 91.0%, and TP 43.0 ~ 95.7%. The SPG showed the best reduction effect for both runoff and NPS pollution. The S also showed encouraging results as a prospective BMP. Crop yields under the treatments also increased by up to 740% (lettuce) and 6.1 ~ 39.2% (cabbage and radish). The mulch treatments were proven to be effective for the increase of farm productivity and to improve runoff quality as well. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of SRI methods on water use, NPS pollution discharge, and GHG emission in Korean trials

A field experiment with a locally-bred Japonica rice cultivar was conducted in 2011 to measure the effect of paddy irrigation management in Korea on rice yield, water use, NPS pollution discharge, and greenhouse gas (GHG) emissions. Experimental treatments were conventional paddy cultivation (CT), CT with SRI water management (CS), CT with two forced mid-season drainages (CD), and SRI methods with two different transplant spacing (SRI-30, SRI-40). Each treatment was replicated. The rice yields, selected water quality indices of the irrigation and drainage water, and GHG emissions were measured and analyzed. Irrigation water was reduced by 49.4 and 47.6 % in the SRI and CS treatments, respectively, compared with the CT treatment. Reductions in non-point source (NPS) pollution load with SRI water management ranged from 16.5 to 53.9 % in the CS plots and from 27.1 to 46.0 % in the SRI plots, depending on the water quality indices measured. The GHG emissions from the CD and CS plots when converted to CO2 equivalents were reduced by 65.5 and 72.8 %, respectively, compared with emissions from the CT plots because CH4 reduction far exceeded the N2O increase from the CD and CS plots. The two highest polished rice yields were 6.47 and 6.34 ton/ha from the SRI-30 and CS plots, respectively; these represented 20 and 17 % increase over yields from the CT plots. Trial results indicate that SRI water management in Korean paddy farming could significantly decrease the paddy irrigation requirements and also discharges of NPS pollution and GHG emissions.

Feasibility of SRI methods for reduction of irrigation and NPS pollution in Korea

An experimental study on the System of Rice Intensification (SRI) methods was conducted to investigate the feasibility of using them to conserve irrigation water and reduce non-point source (NPS) pollution in Korea. Eight experimental runoff plots were prepared at an existing paddy field. Runoff and water quality were measured during the 2010 growing season in which a Japonica rice variety was cultivated. The irrigation water requirements of SRI methods and conventional (CT) plots were 243.2 and 547.3 mm, respectively, meaning that SRI methods could save 55.6% of irrigation water. Runoff from SRI methods plots decreased 5–15% compared with that from CT plots. Average NPS pollutant concentrations in runoff from SRI methods plots during rainfall-runoff events were SS 89.4 mg/L, CODCr 26.1 mg/L, CODMn 7.5 mg/L, BOD 2.0 mg/L, TN 4.2 mg/L, and TP 0.4 mg/L. Except for CODCr and TN, these concentrations were significantly lower than those from CT plots. Measured pollution loads from SRI methods plots were SS 874 kg/ha, CODCr 199.5 kg/ha, CODMn 47 kg/ha, BOD 13 kg/ha, TN 36.9 kg/ha, and TP 2.92 kg/ha. These were 15.8–44.1% lower than those from CT plots. Rice plants grew better and healthier in SRI methods plots than in CT plots. However, rice production from SRI methods plots ranged between 76 and 92% of that of CT plots because the planting density in SRI methods plots was too low. It was concluded that SRI methods could be successfully adopted in Korea and could help save a significant amount of irrigation requirement in paddies and reduce NPS pollution discharge.