| Carrying out heavy metal pollution assessment of vegetable fields and analysis of the sources of heavy metals have important theoretical and practical significance for the healthy development of the vegetable industry in Luliang County.The paper takes Luliang County vegetable planting base as the research background,and collects soil,vegetable and fertilizer samples of vegetable fields under different planting patterns as research objects through field investigation,and analyzes the pollution status of Cd,Pb,Cr,Cu,Zn and As in the samples.The single-factor pollution index method,the field accumulation index method and the Nemero comprehensive quality index method are used to evaluate the pollution degree and ecological risk of heavy metals in vegetable soil;through the bioavailability,morphological analysis and enrichment coefficients of heavy metals in the soil The correlation characteristics of heavy metals in vegetable systems were characterized;through multivariate statistical analysis methods,the main sources of heavy metal pollution in vegetable fields were revealed.The main findings are as follows:1.The 6 heavy metals in the surface soil of 0 ~ 20 cm in the vegetable cultivation area of Luliang County all exceed the background value of soil in Yunnan Province,and there is a phenomenon of heavy metal enrichment.Except for heavy metal Cd,the average of the other five heavy metals is lower than the risk screening value.According to the p H value of the sample point,the standard value is used to calculate the over-standard situation of 6 heavy metals at each point.Among them,the over-standard rate of Cd reaches 67.5%,followed by As,Cu,Pb,and Zn.15%,7.5%,2.5%,of which only Cr did not exceed the standard.2.The evaluation result of the field accumulation index shows that the open vegetable field is not polluted,and the Cu and As in the vegetable field of the facility are at a light pollution level;the evaluation result of the Nemero comprehensive index method shows that the soil of the vegetable field is in light and moderate pollution as a whole The polluted sites of open vegetable fields accounted for 33.33% while thepolluted sites of facility vegetable fields accounted for 50%.3.The content of Pb is higher in the edible parts of vegetables in the study area,and the contents of tubers Cd,Pb,Cr and As are higher than that of leaf vegetables;compare with the standard of GB2762-2017 "National Food Safety Standard Contaminant Limits in Food" Among the vegetable samples,33%,33%,and 11% of the potatoes,cabbage,and cabbage,respectively,exceeded the standard Pb,and the Cd in the potato samples also exceeded the standard.4.Heavy metals Cd,Pb,Cr and As are mainly in the residue state,and the content of weak acid soluble state of Cd is up to 12%;RAC evaluation results show that Cd has the highest risk level and is at a medium risk.The risk levels of other heavy metal elements are all compared.low.5.Pb and As in the chicken manure organic fertilizer applied in the vegetable cultivation process exceed the standard;there are only a large number of elements in the water-soluble fertilizer.The water-soluble fertilizer As exceeds the standard;on the whole,the foliar fertilizer does not exceed the standard,but the amino acids are soluble The Cd content in fertilizers is the highest among all fertilizers.6.The analysis results of the source of heavy metals in vegetable fields show that the heavy metal elements Cd,Cu,Zn and As are mainly related to the application of fertilizers and pesticides during vegetable cultivation;Pb in open vegetable fields mainly comes from traffic pollution sources and Pb in facility vegetable fields Mainly from the application of organic fertilizer;the correlation between Cr and other heavy metal elements is not significant,and it is a natural parent material source that is less affected by human activities. |
PDF Full Text Request