Objective To evaluate the eutrophication status and microcystins (MCs) pollution in 2013 in the Dianshan Lake in Qingpu District of Shanghai.
Methods From March to September of 2013, we set five monitoring sites around the Dianshan Lake based on its geographical and functional characteristics and collected water samples and aquatic animal samples once a month, covering wet, normal, and dry seasons. The samples were evaluated according to quality of surface water category Ⅲ stipulated by Environmental Quality Standards for Surface Water (GB 3838-2002).
Results The average turbidity was 10.73NTU. The average pH was 8.42, the average CODMn was 4.98mg/L, and the average ammonia nitrogen was 0.82mg/L, respectively, meeting the corresponding requirements of the national standard for surface water category Ⅲ. The total nitrogen and total phosphorus were 2.98 mg/L and 0.17 mg/L respectively, beyond the limits of category Ⅲ. No max values of the detected indicators exceeded the limits. The quality of water showed a distinct monthly variation. The average MC-LR and MC-RR during the monitoring periods were 7.02 μg/kg and 10.14 μg/kg respectively; MC-RR was dominant between March and July, and MC-LR was dominant between August and September. MCs were mostly detected in mussels and spiral shells, highest in Hypophthalmichthys molitrix (25.1μg/kg) and Carassius (21.4 μg/kg).
Conclusion The Dianshan Lake is mid-eutrophic. MCs are cumulated in the aquatic animals in the lake.
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