Antibiotics Residue and Ecological Risks in Purple Soils of the Central Sichuan Basin,China
The enrichment of antibiotics in topsoil will interfere with the growth and development of plants,soil fauna,and microorganisms,threatening ecosystem security.As an important agricultural soil resource in the middle and upper reaches of the Yangtze River,China,purple soils are characterized by weak erosion resistance and preferential flow development,which provide dynamic conditions for the migration of environmental residual antibiotics.Formerly,most of the related studies in antibiotics migration in purple soil focused on the mechanism of environmental migration of target antibiotics;unfortunately,the natural abundance,natural contamination characteristics,and environmental risks of soil residual antibiotics are not yet addressed.In this study,purple soil in 6 land use types(dryland,woodland,orchard,paddy field,fertilizing vegetable garden and manuring vegetable garden)and irrigation water in the hilly area of central Sichuan basin,China were targeted for determination of residue levels of 11 antibiotics in five categories,followed by an ecological risk assessment of antibiotics using the risk quotient method.(1)Chlortetracycline(CTC),norfloxacin(NFX),ciprofloxacin(CFX)and enrofloxacin(EFX)were detected in purple soils.NFX,CFX and EFX were only detected in manuring vegetable garden,with soil residues values of 5.95,3.36 and 6.52 µg·kg-1,respectively.CTC had the highest residue of 43.00 μg·kg-1 in manuring vegetable garden among six typical land uses.(2)No antibiotics were detected in irrigation water in the study area,suggesting that the levels of all types of antibiotics residues in irrigation water were below the detection limit of instrument to be used in the study.(3)The risk quotient values(RQ)of antibiotics in purple soils in the study area ranged from 0.08 to 0.43,which were at a low or middle ecological risk level;the antibiotics residues were all lower than the international soil biological toxicity trigger value(100 μg·kg-1),at a relatively safe ecological risk level.(4)The source of antibiotics in the study area might contribute to the application of organic fertilizer;therefore,environmental and ecological risks of antibiotics in soil might be reduced to a certain extent by adjusting the fertilizer application structure.This study provides a basis for ecological security construction in the purple soil area of the central Sichuan basin.
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