Effects Of Difenoconazole And Fludioxonil On Aquatic Benthic Organisms In Surrounding Paddy Fields

The fungicides difenoconazole and fludioxonil are commonly used in agriculture to control the various fungal diseases.It was easy to remain directly or indirectly in water and sediments since these pesticides were widespread using.The pesticides residue may cause damage to benthic animals in aquatic ecosystems,thereby ultimately the service functions of aquatic ecosystems will be completely destroyed.In this paper,in order to study the aquatic ecological risks of difenoconazole and fludioxonil exposed to sediments,the chronic toxicity effects of two organic fungicides on benthic animals were explored separately by the chemical substance spiked sediment method.The exposure and effects of sediment-spiked fungicides on benthic and zooplankton in indoor microcosm.The result showed that:1.Based on the indoor single-species toxicity test,the species sensitivity distribution curves were constructed about 8 species of benthic animals exposure to fludioxonil and difenoconazole,and the 5% hazardous concentration(HC5)was calculated for freshwater benthic organisms.The results showed that:(1)The no effect concentrations on 95% species(HC5)exposed the fludioxonil and difenoconazole were 0.53 mg/kg and 0.40 mg/kg,respectively.(2)the cumulative probability were lower about Neocaridina denticulate,Corbicula fluminea,Limnodrilus hoffmeisteri and Branchiura sowerbyi,which were sensitive to the dienoconazole.Among them,the Neocaridina denticulate was the most sensitive to the difenoconazole,NOEC28 d=0.28 mg/kg;(3)Corbicula fluminea,Hirudo nipponia,Limnodrilus hoffmeisteri and Branchiura sowerbyi were more sensitive to the fludioxonil.Among them,Corbicula fluminea were the most sensitive to fludioxonil,NOEC28 d=0.4 mg/kg.2.A sediment-spiked indoor freshwater microcosm experiment was conducted with fludioxonil and difenoconazole to study exposure dynamics and treatment-related responses of benthic and pelagic zooplankton.It showed that the Cladocerans were the most significantly inhibited exposure to two fungicides.Then Ostracoda and Copepods was secondly inhibited,and finally Rotifers.the NOEC of zooplankton for fludioxonil and difenoconazole were 1.77 ?g/L and 2.60 ?g/L,respectively.Benthic animals showed different sensitivities to the two fungicides.The sensitivity of eight benthic organisms to difenoconazole were Neocaridina denticulata > Physa acuta ? Dugesia japonica > Limnodrilus hoffmeisteri > Branchiura sowerbyi > Corbicula fluminea > Dicrotendipes pelochloris.The NOECbenthonic of fludioxonil was 0.69 mg/kg.The sensitivity of benthic organisms to fludioxnil were Neocaridina denticulata > Corbicula fluminea > Limnodrilus hoffmeisteri > Dugesia japonica > Physa acuta > Branchiura sowerbyi > Dicrotendipes pelochloris.The NOECbenthonic of fludioxonil was 5.58 mg/kg.The maximum predicted exposed concentrations of difenoconazole and fludioxonil in the overlying water using TOP-Rice to predict,were 12.19 ?g/L and 6.38 ?g/L respectively,The RQ values of difenoconazole and fludioxonil calculated wereless than 1.So it was concluded that the toxicity of difenoconazole and fludioxonil were high-risk for zooplankton communities.Compared with the actual exposure concentration of field sediments,difenoconazole and fludioxonil are low-risk pesticides for benthic animals.