Absorption and Enrichment Characteristics of PAHs in Vegetables and the Screening of Cleaning Agents for PAHs

The purpose of this project was to study the absorption and enrichment characteristics of polycyclic aromatic hydrocarbons(PAHs)in vegetables,and to optimize the cleaning agent for PAHs degradation. In this experiment,tomato,pepper,eggplant,cucumber,radish,beans,Lactuca sativa were selected as experimental samples and soaked in 500 μg/kg PAHs solution for 2,4 h respectively. PAHs concentration characteristics of different vegetables were analyzed by detecting PAHs content in the exposed part of the peel and the pulp of vegetables. By comparing the coefficient of variation of PAHs average content in different vegetables,the uniform experimental materials were screened,and then the appropriate conditions of soaking were determined through further experiments. Eight kinds of cleaning agents were used to treat the toxic vegetables,and then chose the degradation effect as the evaluation standard to select the best cleaning agent. After soaking treatment,most of the vegetables showed that the PAHs enrichment ability of the peel was stronger than that of the pulp,and the PAHs migration ability decreased with the increase of PAHs ring number. By comparing the variation coefficient of PAHs content,except the Lactuca sativa,the changes of contents of vegetables were not consistent,and the average content of fruit pulp fluctuated greatly. With Lactuca sativa as the experimental material,the results showed that the appropriate immersion condition was 500 μg/kg of PAHs solution and 60 min of immersion time. The degradation rate of lightweight PAHs was higher than that of heavy PAHs in Lactuca sativa treated with five cleaning agents. By comparing the degradation rate of PAHs of different cleaning agents,and the results showed that detergents and ozone water had the worst degradation ability,and ultrasonic cleaning only had good degradation effect on light PAHs,with the degradation rate up to 72.72%. There were 7 groups of the optimal cleaning agent treatments,all of which were oxidant treatments. The degradation rate of each treatment group was compared,it was found that the best degradation effect was achieved when the concentration of Fenton(nH₂O₂∶nFeSO₄=8∶1)reagent was 800 mg/L,with an average degradation rate of 79.29% for light and 59.07% for heavy PAHs in Lactuca sativa. By exploring the enrichment characteristics of vegetables for PAHs and comparing the degradation effects of different cleaning treatments on PAHs,this experiment provided theoretical guidance for effective pollution control and consumers to select the reasonable and efficient cleaning agents.