Analysis And Evaluation Of Typical Rural Water Quality Situation In Taihu-Lake Region

The objective of this paper was to study the pollution situation of rural water bodiessuch as irrigating water, farmland drainage, groundwater, Tai Lake water and urban riverwater in Tai-lake typical region (Yixing, Wangzhuang and Xinzhuang) from Mar., 2005 toJul., 2006. The research results were taken through analyzing the contents and variation ofnitrogen, total-phosphorus and other polluting factors, such as chloride, sulfate, totalhardness, COD_Mn and some other water quality indexes in different water bodies. Thenprincipal component analysis method and grey clustering method were applied to evaluatestudied surface water and groundwater quality respectively.The results were as follows:1. The difference of total-phosphorus (TP), nitrate nitrogen (NO₃^--N), ammoniumnitrogen (NH₄⁺-N) and nitrite nitrogen (NO₂^--N) contents between groundwater and surfacewater were obvious in rainy season(from May to September each year) than that in dryseason(from November to March each year). However, blooming of algae in surface watersuch as Tai-lake water incarnated the contribution of nitrogen and phosphorus fromfarmland indirectly. Phosphorus pollution situation of studied surface water was bad. TaiLake was in eutrophication situation chronically and phosphorus pollution, which was moreserious than irrigating water and urban river water. In studied region, average content of TPin groundwater was lower than in surface water. Therefore, the loosing of phosphorus byrunoff was more than it by filtering. Nitrate nitrogen was the main contamination ingroundwater. Higher water table of Xinzhuang was an important masons that accumulatingmuch nitrate nitrogen and total-phosphorus. So nitrate nitrogen and total-phosphoruscontents of groundwater in Xinzhuang were more than that in Yixing and Wangzhuang. Thecontents of nitrate nitrogen in groundwater of Xinzhuang from May to September exceededthe limit value (10mg/L) for drinking which prescribed by World Health Organization(WHO) and it was not fit to drink. Ammonium nitrogen and total-phosphorus were themain contamination and with high contents in surface water. However, the limit value oftypesâ…¤for ammonium nitrogen is 0.5mg/L, which prescribed by quality standard forgroundwater in China. So the pollution of ammonium nitrogen of groundwater was moreserious and 74 percent of groundwater in studied region exceeded the limit value.Ammonium pollution of groundwater in Yixing and Wangzhuang were worse than that inXingzhuang and the highest values of them exceed the standard of typesâ…¤of groundwaterquality than 6 and 10 times respectively. Nitrite nitrogen contents of surface water wereobvious higher than that of groundwater. Comparing with the contents of nitrite nitrogen instudied groundwater, the highest one was in Yixing. And 57 percent of groundwater instudied region exceeded the limit value of typesâ…¡for nitrite nitrogen, 40 percent exceededlimit value of typesâ…¢, 8 percent exceeded limit value of typesâ…¤and the highest value of it was 0.323mg/L(Nov., 2005, Yixing), reaching the limit value of typesâ…¤for nitrite nitrogen3 times.2. In three studied regions, comparing with the contents of chloride in surface water,the chloride content was higher in Wangzhuang and Xinzhuang's than that in Yixing.Chloride was not the main contamination in studied groundwater. In three studied regions,comparing with the average contents of chloride in groundwater, the highest one was inXinzhuang, Wangzhuang was lower and Yixing was the lowest. The research resultsshowed that sulfate and total hardness was not the main contamination in studied waterbody. Comparing with studied groundwater, the highest contents of sulfate was inWangzhuang and content of total hardness in Xinzhuang was the highest of all.In surface water of three studied regions, pollution of COD_Mn was serious. COD_Mncontents of irrigating water exceeded 10mg/L, which is the limit of the standard of typesâ…¤of surface water quality. The COD_Mn content of Tai Lake water was 9.85mg/L, whichapproached the limit of the standard of typesâ…¤. COD_Mn pollution was also serious ingroundwater, although its contents were lower than surface water. COD_Mn average contentof grounderwater in Xinzhuang was higher than other research regions. The contents ofCOD_Mn in Xinzhuang and Yixing were all exceed the limit value of the standard of typesâ…¤of groundwater quality (3.0mg/L). There was 47.2 percent of groundwater in studied regionexceeding limit value of typesâ…¢for COD_Mn and the highest value of them was39.662mg/L, exceeding the limit value of the standard of typesâ…¤for COD_Mn ofgroundwater quality 10 times nearly.Contents of As., Se. and heavy metal were very low in studied water body. They werenot main contamination of studied water body. Turbidities of surface water were higherthan that of groundwater. For groundwater, the highest of turbidities was in Yixing and thehighest of total deliquescent solid (TDS) was in Xinzhuang. However, all the contents ofTDS were not exceeded limit value (1000mg/L) of typesâ…¢of groundwater. Contents ofDO in groundwater were lower than that in surface water. In studied regions, there was 62.5percent of surface water exceeding limit value (4mg/L) of typesâ…¢for BOD₅.3. Analysis results of principal component showed that COD_Mn, TN and NH₄⁺-N wereconsanguineous correlative factors with the first principal component of surface water inrainy season and NH₄⁺-N and TP were consanguineous correlative factors with the firstprincipal component of surface water in dry season.Evaluating results of water quality showed that groundwater quality was bad in studiedregions. In all groundwater monitor sits, 15.28 percent of them wereâ…¡type's groundwater,19.44 percent wereâ…¢type's groundwater, 27.78 percent wereâ…£types and 37.5 percentwereâ…¤types. During studied period, the worst groundwater quality was in January. Therewere 67 percent of them reachingâ…¤type's groundwater and 25 percent reachingâ…£type'sgroundwater. The proportion ofâ…¡type's groundwater was 0 in this month. In March andJuly, groundwater qualities were better than January. There were 59 and 49 percentreachingâ…¤type's groundwater, 33 and 17 percent reachingâ…£type's groundwaterrespectively. In November, groundwater quality was the best and 58 percent wasâ…¢type'sgroundwater or better. Comparatively, groundwater quality in Wangzhuang was the best,Yixing was next and Xinzhuang was the worst. These results of this paper can providescience datum for rural groundwater protection, agricultural non-point sources treatment or country environmental protection in Tai-Lake region.