乌伦古湖水质污染的空间分布特征

评价湖泊水质并探究其空间分布规律对于湖泊管理具有重要意义。通过对乌伦古湖2017年7-8月采样点(S1~S8)的8个水质指标(矿化度、pH值、透明度、总氮、总磷、高锰酸盐指数、溶解氧、五日生化需氧量)监测,运用主成分分析法(PCA)评价乌伦古湖水质现状,采用空间插值法分析其空间分布特征,并基于聚类分析法(CA)识别水质污染驱动因素。结果表明,乌伦古湖水体呈弱碱性,水质污染以氮、磷有机污染为主;8个采样点主成分综合得分排序结果为:骆驼脖子>小海子>码头>中海子>农十师渔政点>湖中心>吉力湖中心>吉力湖入水口,呈现出小湖区水质优于大湖区、湖中心区水质优于湖岸区、距离进水口越远水质越差的显著空间差异特征。骆驼脖子采样点(S1)水质污染最严重,吉力湖采样点(S7、S8)水质相对最好;基于湖区水质空间分布特征将乌伦古湖湖区分为3类,Ⅰ类湖区水质最差,Ⅱ类湖区水体呈咸化趋势,Ⅲ类湖区水质相对最好;水体矿化度、营养盐与有机污染物是乌伦古湖污染的主要来源,主要原因可归结为自2000年来乌伦古河常态化断流以及湖区渔业养殖、周边农业面源污染导致的盐分与营养成分及有机污染物由河道不断向湖泊的迁移富集。

Spatial Distribution of Water Quality in Ulungur Lake

Ulungur Lake, consisting of Buluntuohai Lake and Jili Lake, is the second largest inland lake in Xinjiang and serves important ecological functions. Assessing lake water quality is important for tracking changes and evaluating lake health, and is closely related to the ecological security of the basin. In this study, the current situation and spatial distribution of water quality in Ulungur Lake were evaluated and analyzed using principal component analysis(PCA) and spatial interpolation. The driving factors of water pollution were explored using cluster analysis(CA). The objective was to provide a reference for conserving the water environment and managing Ulungur Lake, and for other typical arid inland lakes. In July and August 2017, a water quality investigation was carried out at eight sampling sites, covering all of Ulungur Lake:(S1) Luotuobozi,(S2) Matou,(S3) Zhonghaizi,(S4) the open area of Buluntuohai Lake,(S5) the Nongshishi fishery administration station,(S6) Xiaohaizi,(S7) the inlet of Jili Lake and(S8), the open area of Jili Lake. Eight water quality parameters were measured including salinity, pH, Secchi disk transparency(SD), total nitrogen(TN), total phosphorus(TP), permanganate index(CODMn), dissolved oxygen(DO) and the 5-day biochemical oxygen demand(BOD5). The water in Ulungur Lake was weakly alkaline, and pollution was dominated by organics, nitrogen and phosphorus. The comprehensive water quality index for the eight sampling sites ranked as follows: Luotuobozi>Xiaohaizi>Matou>Zhonghaizi>Nongshishi fishery administration station >open area of the Buluntuohai Lake>open area of the Jili Lake>inlet of the Jili Lake and spatial differences in water quality were significant. Water quality in Jili Lake was better than in Buluntuohai Lake, water quality was better in open waters than near the shoreline and water quality declined with distance from the inlet. Water pollution at S1 was most serious, and water quality at S7 and S8 in Jili Lake was the best. Based on the spatial distribution of water quality, Ulungur Lake had three distinct areas: Class I included S1, S2, S4 and S5 with the worst water quality in eastern, western and central Buluntuohai Lake;Class II included S3 and S6 in south and north Buluntuohai Lake and the water is becoming more saline;Class III included S7 and S8 in Jili Lake, with much better water quality than in the other two areas. Salinization and inputs of nutrients and organics were the primary threats to water quality in Ulungur Lake. Salinization and declining water quality were attributed primarily to the normalized water cut-off in Ulungur River since 2000. This has resulted in the buildup of salt, exacerbated by organic pollutant inputs from aquaculture in the lake and agricultural non-point source pollution from peripheral areas.