Research On Characteristics And Mechanism Of Phthalate Acid Esters Pollution In Farmland Of The Huang-Huai-Hai Region Of China

Phthalate acid esters（PAEs）are widely used as plasticizers and various additives.In recent years,with large-scale use of plastic products,they have become common pollutants in Chinese farmland,which have attracted much attention in domestic and overseas.Through literature research,it is found that the current research mainly focused on the distribution of PAEs in greehouse vegetable soils and health risk assessment.Some researchs have found that the pollution situation and potential risks of PAEs in the rotation open-field soils are equal to or even more than the greehouse vegetable soils.However,existing studies have paid less attention to the pollution situation in actual farmlands.The research on the relationship between soil enzyme activity,soil microbial community and PAEs residues mainly based on indoor addition experiments,and the concentrations of added PAEs was high and the type was single,which cannot reflected the complex situation in the actual farmland system and the impact of multiple PAEs with relatively low concentrations.In this paper,the pollution of 16 PAEs and agricultural inputs in the open-field and vegetable soils of the Huang-Huai-Hai region was investigated.The human risk assessment model was used to estimate the risk of PAEs in agricultural soils.Through the determination of soil physical and chemical properties and soil enzymes’activities,the biological and abiotic factors related to PAE pollution were discussed.Based on high-throughput sequencing and related statistical analysis,the effects of PAEs on the microbial community of typical greenhouse vegetable soils and the response of different microbial communities in agricultural soils to PAEs in different planting patterns were studied.The conclusion of this study is as follows:1.The total concentration of 16 PAEs ranged from 66.7-3646.5 g kg-¹ and the average value was912 g kg-¹,and the detection rate was 100%.The mean value of 16 PAEs concentration in the soil of the greenhouse vegetable soil was higher than that of the open-field soil,so the greenhouse vegetable soil was the hotpot of PAEs pollution.However,it is worth noting that,as the main pollutant,Bis（2-ethylhexyl）phthalate（DEHP）has similar concentration levels in greenhouse vegetable and open-field soils.Therefore,considering the total concentration alone does not reflect the actual pollution situation,and it is necessary to study the individual types of PAEs.In terms of the analysis of pollution sources,the research on agricultural inputs shows that the agricultural film is the main source of PAEs pollution in the farmland soil of the Huang-Huai-Hai region,and the statistical analysis of the pollution concentration shows that the soil of the contaminated greenhouse vegetable soil will also become a potential source of PAEs pollution.The distribution and regularity of PAEs in farmland soil in the Huang-Huai-Hai region are obviously regional,which is related to agricultural inputs and planting methods..2.Through the human risk assessment model recommend by U.S.Environmental Protection Agency,the carcinogenic and non-carcinogenic human health risks of PAEs from agricultural soil were assessed.It was found that the non-carcinogenic risks were mainly caused by diet.Risk of the main pollutants,DBP and DEHP,can represent the non-carcinogenic risk of PAEs.For the non-carcinogenic risk through dietary,DEHP contributes to the harzard index of PAEs in greenhouse vegetable soils in the range of 61.4%-81.3%,with the highest in Hebei Province.DEHP contributes to the harzard index of PAEs in open-field soils exceeding 96.8%,of which Tianjin is the highest,reaching 98.2%.Therefore,the main risk of PAEs in farmland soil comes from DEHP.The non-carcinogenic risk through dietary was affected by the combination of the dietary structure of the population and the level of PAEs pollution.The non-carcinogenic risk of DBP through dietary in open-field soils was higher than that of in greenhouse vegetable soils,while DEHP is the opposite（except for Tianjin children）.Children had higher risk compared to adults.For the carcinogenic risk caused by DEHP,the carcinogenic risk of more than 99%of the samples is lower than 10-⁶,which was at a very low level.As the main production base of agricultural products in China,the product safety in the Huang-Huai-Hai region is reassuring.3.Based on the pollution degree of PAEs,Shouguang city was divided into three areas,it was found that pollution of PAEs in different areas was related to composition of soil microorganisms and activities of soil enzymes.Concentration of PAEs in the typical vegetable soil was positively related to activities of catalase and sucrase and negatively related to activities of dehydrogenase and urease.The effect of dimethyl phthalate（DMP）and DBP on soil microbial community was greater than that of other PAEs.Soil microbial richness and diversity decreased with the increase of PAEs concentration.Metastat analysis was used to screen some resistant and sensitive bacteria,such as Rhodanobacter and Dokdonella,which can be used as potential biological indicators of PAE pollution in soil.4.Through high-throughput sequencing,it was found that the microbial community in agricultural soil of Hebei Province was more affected by planting patterns than by geographical location.As a significant factor,PAEs had a greater impact on the microbial community in vegetable soils.The microbial community in open-field soils is mainly affected by PAEs with high Octanol-Water Partition Coefficient(K_OW),and all the detected PAEs had a greater impact on the microbial community of vegetable soils.PAEs can participate in the cycle of macronutrients in the soil by affecting the abundance of microorganisms,such as inhibiting Nitrospira,which is involved in nitrogen metabolism,in greenhouse vegetable soil.