Research On The Variation Characteristics Of Water Quality In Jiangsu Coastal Waters

Marine economy in Jiangsu province has been sustained growth in recent years, but in the meanwhile deterioration of marine ecosystem highlighted day after day. Seawater as the accepting water body of pollutants from production activities in coastal zone, the feature analysis on which has an important guiding significance on the management of coastal development and ocean environment protection.This article studied the changing trends and time-space characteristics of water quality and the eutrophication in coastal waters through comparative analysis based on the water quality data of many years in offshore area of Jiangsu. On the basis of the trend analysis, combined with the conditions of geomorphic features and the exploration and utilization of sea area, Jiangsu coastal waters could be divided into three parts and the causes of pollution in each part were analyzed. The main conclusions are as follows.(1) Inorganic nitrogen and phosphate are major pollutants of current Jiangsu coastal waters. The three coastal cities all have their own characteristics. The pollution of Lianyungang coastal area is mixed type, while Nantong coastal water is mainly polluted by nutrients salts. Yanchen coastal area is the transition region between the former two parts. The characteristics of Jiangsu coastal waters showed that from spring to autumn oxygen consumption pollution reduced and nutrient pollution aggravated.The current restricting factors of eutrophication in coastal waters of the three cities are different. Lianyungang nearshore water turned gradually from phosphorus restrict state to eutrophication dominated state from spring to autumn. Yanchen nearshore water was almost in the eutrophication dominated state and in autumn some areas showed Nitrogen limitiation feature on very local scales. Nantong nearshore water present the variation trend of "hybrid nutritional state-eutrophication dominated state-potential eutrophication of Nitrogen limitiation dominanted state" from spring to autumn.(2) Inorganic nitrogen and phosphate have been major pollutants of Jiangsu coastal waters for many years. Inorganic nitrogen content is general stability and phosphate concentration increases significantly. The concentrations of oxygen consumption pollutants in the north part was heavier than that in the south part, and the most seriously polluted areas were around GanYu nearshore and the waters from Guanhe estuary to Feihuanghe estuary. The pollution of nutrients in the north part was lighter than that in the south part, just in contrast to the spatial distribution characteristic of oxygen consumption pollutants. The most seriously polluted areas located in the border of Yancheng and Nantong nearshore, the nearshore of Yaowanggang brake to Tuanjie brake and the east coastal waters of Qidong.According to the results of eutrophication index method, EI value in Lianyungang and Nantong nearshore waters was on the rise. Eutrophication status of yancheng waters improved over the past few years. For years, the areas where eutrophication occurred frequently mainly distributed in the areas from Dongtai estuary to Xiaoyangkou harbor as well as the region from the estuary of Rutai canal to Dayang harbor. At the early stage of the11th five-year plan, the value of N/P of coastal waters of Jiangsu was on the high side compared to Redfield value and this region might become potential eutrophication areas of phosphate limitiation when the nutrient concentration reached a certain level. Over the last few years, the value of N/P in yancheng and nantong waters was on the decline. The value of Yanchen coastal waters reduced to nomal levels and that value of Nantong dropped to a lower level which meant that Nangtong coastal waters would become potential eutrophication areas of nitrogen limitiation just as the nutrient concentration reached a certain level.(3) GanYu nearshore waters, lianyun port and Xuwei port were heavy polluted areas in Haizhou Bay region. Fisheries and transportation had a severe impact on the regional water environment. Besides, the diffusion of contaminants reduced because of the half open terrain features. All of above made Haizhou Bay a heavy polluted region.The south part of Guanhe estuary and Zhongshanhe estuary were seriously polluted areas of abandoned delta of Huanghe River region. Guanhe River, Zhongshan River, chemical industry park located at Guanhe estuary and the waters used for dumping and sewage located outside Zhongshan estuary all had great influence on the regional water environment. The pollution levels of waters of Fansheng estuary and Biandan port was not remarkable because of intense water dynamic condition.Waters of Xinyang port, Xiaoyangkou pot, Dongzhao port located at the end of Xiaomiaohong channel, Tuanjie brake and the east coastal waters of Qidong were heavy polluted areas in the region of radiate sandbanks. Estuaries including Sheyang estuary, Xinyang port, Doulong port, Bencha canal, Tonglv canal, north branch of Changjiang estuary, waters used for transportation including Sheyang port, Yangkou port, Dongzhao port, Lvsi port and waters used for dumping and sewage located at Yangkou chemical industry park of Rudong all had great influence on the regional water environment. Terrain conditions of offshore radiate sandbanks also had a certain impact on the distributions of the pollutents.