After the appalling ＂Wuxi Drinking Water Crisis＂, increasing investigations concerning the contaminations of cyanobacterial blooms and their toxins in Lake Taihu have been performed and reported in the last two years. However, information regarding these issues before the crisis in 2007 remained insufficient. To provide some background data for further comparisons, the present study reported our investigations conducted in 2004, associated with the cyanotoxin contaminations as well as the eutrophication status in Lake Taihu. Results from the one-year-study near a drinking water resource for Wuxi City indicated that, unlike the status in recent two years, cyanobacteria and chlorophyta are the co-dominance species throughout the year. The highest toxin concentration （34.2 ng/mL） in water columns occurred in August. In bloom biomass, the peak value of intracellular toxin （0.59 μg/mg DW） was determined in October, which was lag behind that in water column. In addition, MC-RR was the major toxin variant throughout the year. During the study period, nutrients levels of total nitrogen and phosphorus were also recorded monthly. Results from the present study will lead to a better understanding of the eutrophication status and the potential risks before ＂Wuxi Drinking Water Crisis＂.
Yongmei LiuWei ChenDunhai LiZebo HuangYinwu ShenYongding Liu
The temporal distribution of polycyclic aromatic hydrocarbons （PAHs） was investigated in a sediment core from Lake Erhai in Southwest China using gas-chromatography/mass spectrometry （GC/MS） method. The total organic carbon （TOC） normalized total PAHs concentrations （sum of US Environmental Protection Agency proposed 16 priority PAHs） ranged from 31.9 to 269 ixg/g dry weight （dw）, and were characterized by a slowly increasing stage in the deeper sediments and a sharp increasing stage in the upper sediments. The PAHs in the sediments were dominated by low molecular weight （LMW） PAHs, suggesting that the primary source of PAHs was low- and moderate temperature combustion processes. However, both the significant increase in high molecular weight （HMW） PAHs in the upper sediments and the vertical profile of diagnostic ratios pointed out a change in the sources of PAHs from low-temperature combustion to high-temperature combustion. The ecotoxicological assessment based on consensus-based sediment quality guidelines implied that potential adverse biological impacts were possible for benzo（ghi）perylenelene and most LMW PAHs. In addition, the total BaP equivalent quotient of seven carcinogenic polycyclic aromatic hydrocarbons （BaA, CHr, BbF, BkF, BaP, DBA and INP） was 106.1 rig/g, according to the toxic equivalency factors. Although there was no great biological impact associated with the HMW PAils, great attention should be paid to these PAH components based on their rapid increase in the upper sediments.
