51ng/L) [27] and the Wuhan section of the Yangtze River (1.88ng/L) [28], and comparable with that in the Huaxi River in Guizhou (2.079ng/L) [29] and the Guanting Reservoir in Beijing (2.26 �� 2.84ng/L) [30]. The levels of HCHs were similar to those in Lake Baiyangdian (2.1 �� 0.8ng/L) [31], considerably lower than those in the Qiantang River in Zhejiang (33.07 sellekchem �� 14.64ng/L) [32], the Chiu-lung River in Fujian (71.1 �� 85.5ng/L) [33], and the Kucuk Menderes River in Turkey (187�C337ng/L) [6], and higher than those in Meiliang Bay in Lake Taihu (>0.4ng/L) [34], Lake Co Ngoin in Tibet (0.3ng/L) [35], and Lake Baikal in Russia (0.056�C0.96ng/L) [36]. The concentrations of DDTs were also at low levels, which were roughly equal to those in the Nanjing section of the Yangtze River (1.57�C1.

79ng/L) [37] and lower than those in the Guanting Reservoir (3.71�C16.03ng/L) [38], the Huangpu River (3.83�C20.90 [11.97]ng/L) [39], the Pearl River artery estuary during the low flow season (5.85�C9.53ng/L) [11], the Kucuk Menderes River in Turkey (ND-120ng/L) [6], and the Lake Baikal in Russia (ND-0.015��g/L) [36].3.2. The Spatial and Temporal Distribution of OCPs in the WaterThe changes in the concentrations of the total OCPs and the three main pollutants (HCHs, DDTs, and aldrin) in Lake Chaohu and the three subregions from May 2010 to February 2011 are shown in Figure 4. There were similar trends for the OCPs over time both in the entire lake and in the Central Lake. The OCP levels increased jaggedly from May to September, and the peak was in September.

Then, the residues declined rapidly, reached the bottom in November, and rose again from December to February. The trend in the Western Lake from September to February was the same, but the trend in the Eastern Lake was different. One of the main causes was that the concentrations of DDT in July were excessive, resulting in the higher OCPs from the Eastern Lake in July than that in the other months. There was presumably a temporary point source pollution in July. Moreover, the high values of aldrin both in the Western and the Central Lake in September, which were not observed Drug_discovery in the Eastern Lake, made the overall trends of the Eastern Lake different from the other subregions.Figure 4The temporal and spatial variation of OCPs in the water from Lake Chaohu.Ten months were divided into four seasons, with spring just using the data of May as a reference. The concentrations of HCHs in the four seasons were 1.44ng/L, 1.25ng/L, 1.19ng/L, and 2.81ng/L, and the concentrations of DDTs were 3.61ng/L, 3.75ng/L, 1.53ng/L, and 0.24ng/L. The variable trends of the HCHs and the DDTs were similar except during winter, and the concentrations were higher in spring and summer than in autumn.