Occurrence characteristics， source apportionment， and ecological risk assessment of pesticides in plateau lakes：a case study of Dianchi Lake

This study systematically investigated the occurrence， multi-dimensional spatial distribution， sources， and ecological risks of 160 pesticides in Dianchi Lake， a typical plateau lake impacted by agricultural activities. The results showed that a total of 37 pesticides were detected in the water of Dianchi Lake， with a total concentration range of 64.2 to 1132.8 ng/L （average concentration： 610.0 ng/L）. Fungicides such as boscalid （BOS）， fluopicolide （FPC）， and dimethomorph （DMM） were the dominant compounds. accounting for up to 65.0% of the total concentration. Spatially， concentrations in the southern lake region （672.5 ng/L） were significantly higher than those in the north due to intensive facility agriculture， and highly hydrophobic pesticides （e.g.， penconazole （PEN）） showed a migration trend of enrichment towards the bottom layer. Source apportionment results indicated that inflowing rivers and wastewater treatment plant effluents were the main input sources of pesticides in Dianchi Lake， with average concentrations being 7 and 9 times higher than those in the lake water， respectively. The ecological risk of pesticides to aquatic organisms in Dianchi Lake was ranked as algae > daphnia > fish. Prometryn （PMT） was identified as a high-risk factor for algae， while profenofos （PFF） and carbendazim （CBD） posed potential threats to organisms at higher trophic levels. These findings provide fundamental data and technical support for understanding the occurrence characteristics， source apportionment， and ecological risks of pesticides in typical plateau lake waters.