Assessment Of Agricultural Non-Point Source Pollution In The Pearl River Delta Region

With the improvement of people’s living standard, the problems of water environment arebecoming more serious increasingly. Eutrophication is caused by many reasons, and industrialwaste water and city sewage are the most important ones, however, as the research showed, theagricultural non-point source pollution is also one of the important reasons causing waterdeterioration.A case study of drains at Zhangsong Village and No.15Chung of Wanqingsha was carriedout to survey agricultural non-point source pollution in the Pearl River Estuary. According to thefiled-work, samples sites were set up to monitor the concentrations of nitrogen, phosphorus andCODcr at the two study areas from October2010to October2011. The spatial-temporaldynamics of all mornitoring indicators in agricultural ditch systems and the correlation betweenthem were analyzed. The dominant factor affecting the water quality of the two study areas wasanalyzed by the principal component analysis. The relevant prevention and control measures ofagricultural non-point source pollution were proposed.The main research results are as follows:1. The study areas are far from industrial zone. The contents of nitrogen and phosphorusand CODcr in Zhangsong Village farmland water are high by the influence of farmland andfarmer drainage.The farmland water of ZhangsongVillage is serious polluted which belows theⅣ class. Besides total nitrogen and CODcr, the average contents of other water quality indexatNo.15Chung of Wanqingsha drainage is relatively low and it is only influenced by the farmlanddrainage. The average contents of nitrogen, phosphorus and CODcr are as follows: the flow﹥farmland water﹥pearl river channel in different periods.2. The time distribution of the contents of nitrogen, phosphorus and CODcr is: wet period﹥dry period. The spatial distribution of them is: along with the downstream of drains, the averagecontents of total phosphorus and CODcr decreased, but has no significant change of nitrogencontents in drains of Zhangsong Village in different period. Along with the downstream of drains,the average contents of nitrogen, total phosphorus and CODcr aslo decreased in No.15Chung ofWanqingsha, except the nitrate nitrogen.3. The result shows that the relationships between ammonia nitrogen, total phosphorus,CODcr, salinity and total nitrogen are significantly positive, but there is no significantcorrelation between taotal nitrogen and nitrate nitrogen in drains of Zhangsong Village in wetand dry season, which reveals that nitrate nitrogen may directly from the loss of farmlandfertilizer rather than organic nitrogen transformation. The relationships between nitrate nitrogen,ammonia nitrogen and total nitrogen are positively correlated respectively in No.15Chung ofWanqingsha drainage, which shows that they had completely transformed. 4. The results show that the main factor affecting the water quality of Zhangsong Villagefarmland water is ammonia.And CODcr and salinity are the main factors in No.15Chung ofWanqingsha farmland water.