| Persistent organic pollutants(POPs) characterized by organochlorine pesticides (OCPs) in the soil and plant residues remains the threats on the survival and health of human beings,although the pesticide has been prohibited over twenty years.Meanwhile, the results obtained in the past were still difficult to make the needs of polluted soil remediation and agricultural and forestry clean production resulting from the compex geomorph,diverse soils and ecological types,varied application methods and amounts of pesticide,although numerous studies have been given to the characteristics of residue and migration of OCPs.In order to provide the scientific basis with the optimal layout of agricultural and forestry clean production and polluted soil remediation,therefore,the contents of OCPs and their isomers and metabolites in 93 surface soils and 45 plants(215 plant samples) were detected in typical hilly and plain region(Wutongqiao County) of SW Sichuan,the characteristics of the residue and migration of OCPs in soils and its effect on soil enzyme activity were studied,the potential ecological risk was assessed,and the plants with higher and lower OCPs contents were distinguished based on the residual characteristics of OCPs in the representative plants,employing the methods of randomly sampling the soils according to functional zones and Kriging method in geostatistics in combination with simulated soil core experiment.Residual HCHs and DDTs and their isomers and metabolites in soils distributed normally with strong variations.HCHs concentration in 18.4%soils was lower than the first level of National Soil Environment Quality Standard(GB15618-1995)(＜50μg·kg-1), and the rest the second level(＜500μg·kg-1).Correspondingly,DDTs concentration in 68.1%soils were lower than 50μg·kg-1,which accorded with the first level of National Soil Environment Quality Standard.Soils in the region(Shilin town) mainly with agricultural and forestry production had the highestα-HCH andβ-HCH contents,while soils in the region(Guanying town) mainly with agricultural production had the highestγ-HCH content.Similarly,soils from the region(Yangliu town) with the frequent human activities had the contents of the highestδ-HCH and the lowest p,p'-DDT,while soils from the region(Jinshan town) mainly with forestry production had the contents of lower p, p'-DDE and p,p'-DDD.The ranked order of the total OCPs content was rice fields＞agroforestry intercrop land＞vegetables land＞orchard land＞dry land＞nursery land＞rape land＞wheat rotate land,that ofΣHCH was agroforestry intercrop land＞orchard land＞vegetables land＞rice fields＞rape land＞dry land＞nursery land＞wheat rotate land, and that ofΣDDTwas rice fields＞vegetables land＞agroforestry intercrop land＞orchard land＞nursery land＞dry land＞wheat rotate land＞rape land.The contents of HCHs and their isomers and metabolites in soils distributed limpidly, while the total content of HCHs in soils were the highest in the agricultural zone(Caijin, Guanying and Shilin towns).The hilly region(Shilin town) had the highest contents of total DDT and p,p'-DDT,while the basin plain(Yangliu,Zhugen and Xiba towns) had the highest contents of p,p'-DDD and p,p'-DDE in soils.On the whole,scils in the studied region were contaminated to a certain extent by residual organochlorine pesticide.The transfer and degradation of OCPs correlated positively and significantly with the eluviation intensity.0～10cm soil layers had higher OCPs degradation rate when soil moisture was 25.1%in calcareous purple soil,while higher soil moisture was not favorable for OCPs degradation.Similarly,0～10cm soil layers had higher OCPs degradation rate when soil moisture was 29.9%in acid purple soil,while higher soil moisture was not favorable for OCPs degradation.PPO activity correlated was favorable for OCPs degradation in soils.However,OCPs degradation was not significantly correlated with the activities of dehydrogenase and urease in soils.In addition,residual OCPs were positively and significantly correlated with the positive correlation with nitrate reductase activity in calcium purple soil.Soils in the study area had the low-dose potential ecological risks of DDTs.Soils in the zones of residence and industry had the lower potential ecological risks,while agricultural zone might have the higher potential risks to birds,mammals and soil animals. In addition to wheat and rapeseed,other land use types may have the potential ecological risks of mammals.Soils in other land uses had the potential ecological risks to mammals to a certain extent expect for wheat and rape fields.The plants with higher contents of organochlorine pesticide included Pinus massoniana,Phragmites communis,Canna edulis,Ipomoea batatas and Rubus multibracteatus,and the contents were 149.30μg·kg-1,112.99μg·kg-1,88.18μg·kg-1,75.90μg·kg-1,and 999.43μg·kg-1,respectively.The plants lower contents of organophosphorus pesticide included Firmiana simplex,Cucurbita moschata and Citrus grandis had,and the contents were 5.91μg·kg-1,1.60μg·kg-1,and 1.44μg·kg-1,respectively.The organochlorine pesticide in Astragalus sinicus and Medicago sativa had not been detected. Organophosphorus pesticide had lower contents in all plants,only the plants of Eucalyptus grandis(31.22μg·kg-1),Metasequoia glyptostnobcides(6.45μg·kg-1),Artemisia annua (43.23μg·kg-1),Ipomoea batata(1.70μg·kg-1),Apium graveolens(22.90μg·kg-1),Glycine max Merr(49.57μg·kg-1) and Ficus microcarpa(4.95μg·kg-1) had been detected.It was suggested that Canna edulis,Rubus multibracteatus,Camellia japomica and Ficus micro Carpa be good accumulator plants for pesticides,and Astragalus sinicus,Medicago sativa, Gynura pseudochinabicolor be good non-accumulator plants for pesticides.
|
PDF Full Text Request