太湖微囊藻毒素的时空分布特征

微囊藻毒素对水体危害严重,为了探究太湖中微囊藻毒素的变化规律及其主要环境影响因子,对太湖34个采样点进行了为期1 a(2011年11月—2012年10月)的监测与采样,分析了水体中ρ(MCs)(MCs为微囊藻毒素)〔包括ρ(TMC)(TMC为总藻毒素)、ρ(EMC)(EMC为胞外藻毒素)和ρ(IMC)(IMC为胞内藻毒素)〕,以及ρ(Chla)、蓝藻生物量、ρ(TN)、ρ(TP)、N/P〔ρ(TN)/ρ(TP)〕、pH、温度、透明度、电导率、ρ(DO)等水环境因子的变化特征,讨论了ρ(MCs)与各水环境因子之间的相关性. 结果表明:ρ(MCs)在太湖中呈现一定的规律性,在7—8月蓝藻爆发期,ρ(MCs)低于0.10 μg/L,之后逐渐升高,9月达到最高值(0.28 μg/L). 受地理位置和沉积环境等影响,太湖西北区MCs污染最严重,ρ(MCs)最大值为0.30 μg/L. 相关性分析结果表明,ρ(MCs)与ρ(Chla)、ρ(TN)、ρ(TP)、N/P显著相关,其中,ρ(MCs)与ρ(Chla)呈极显著正相关(P<0.01)；ρ(IMC)和ρ(TMC)均与蓝藻生物量呈显著正相关(P<0.05),而ρ(EMC)与蓝藻生物量相关性不显著；ρ(IMC)和ρ(TMC)均与ρ(TN)呈极显著负相关(P<0.01),而ρ(EMC)与ρ(TN)呈显著负相关(P<0.05)；ρ(MCs)与ρ(TP)呈显著正相关,而与N/P呈显著负相关(P<0.05). 

Spatial and Temporal Distribution of Microcystin in Taihu Lake

In order to explore the variation of microcystin and its main environmental factors, the spatial-temporal variations of a series of biological, chemical and environmental parameters including total microcystin (TMC), extracellular microcystin (EMC), intracellular microcystin (IMC), ρ(Chla), cyanobacterial biomass, ρ(TN), ρ(TP), N/P〔ρ(TN)/ρ(TP)〕, pH, temperature, transparency, conductivity and ρ(dissolved oxygen) were characterized based on continuous and synchronous monitoring of water quality from 34 locations in Taihu Lake from November 2011 to October 2012. The relationship between water quality and MCs was also investigated. Taihu Lake was divided into six regions - with a total of 34 sampling points - based on its terrain and water quality. The concentrations of microcystin were measured by Enzyme-Linked Immunosorbent Assay (ELISA), using standard recovery experiments to evaluate the method's accuracy. All statistical analyses were conducted with SPSS software. The concentrations of ρ(MCs) in Taihu Lake showed a temporal pattern. ρ(MCs) were at a low level from March to June, then gradually increased during the outbreak of cyanobacterial blooms from July to August, but were still below the level of 0.10 μg/L. In September, ρ(IMC) and ρ(EMC) spiked to 0.18 and 0.10 μg/L, respectively. Although the temporal pattern of microcystin concentrations was similar among plots, the unbalanced development of regions and different hydrological conditions around Taihu Lake affected the spatial variation. Toxin levels were slightly higher in the northwest than in other regions, with the maximum value of 0.30 μg/L appearing in the northwest area. Strong correlations were found between ρ(MCs) and ρ(Chla), ρ(TN), ρ(TP) and N/P. The biomass of cyanobacteria was positively correlated to ρ(TMC) and ρ(IMC) (P<0.05), but not ρ(EMC). ρ(TN) was negatively correlated to ρ(IMC) (P<0.01), ρ(TMC) (P<0.01) and ρ(EMC) (P<0.05). ρ(MCs) was positively correlated to ρ(TP) (P<0.05), while negatively correlated to N/P (P<0.05).