Study On Multi-element Coupling Analysis And Potential Ecological Effect Evaluation Of Typical Agricultural Land Soils In Eastern Anhui Province

Following with the urbanization and the changes in industrial and agricultural structure,production and life styles,such as mining pollution,garbage incineration,sewage hazard,exhaust emission,abuse of chemical fertilizers,have caused the destruction of the local land ecological environment,soil pollution,especially the geological environment problems caused by heavy metal pollution,has received widespread attention.Exceeding standard of heavy metal elements is one of the main problems of soil pollution in commodity grain base in China,which directly restricts the quality of agricultural land,the scientific development of land resources,the construction of high-standard prime farmland,and threatens food security and human health.So it has important meaning in scientific research and real life to carry out the distribution law of soil elements in agricultural land,multi-element coupling analysis in soil,source analysis of heavy metal elements,occurrence characteristics of heavy metal sources and potential ecological risk assessment for deeply understanding of the land quality status in the study area.In this paper,344 soil samples and 9 groups of root soil-rice samples were collected from the soil of typical agricultural land in eastern Anhui Province.Combined with step-by-step chemical extraction experiments and soil microscopic experiments,the chemical structure,distribution characteristics and occurrence state of heavy metal elements in soil of agricultural land were studied by Atomic fluorescence spectroscopy(AFS),X-ray diffraction(XRD),X-ray fluorescence spectroscopy(XRF),plasma mass spectrometry(ICP-MS),inductively coupled plasma spectrometry(ICP-AES),Kjeldahl nitrogen distillation acid-base titration volumetric method,scanning electron microscopy(SEM)and other technical methods,and comprehensive benefit evaluation of nutrient elements and potential ecological risk evaluation of heavy metal elements were carried out.The main achievements are as follows:(1)The reference values of 14 elements in soil of the study area were determined.It was found that the reference values of 11 indexes were basically equivalent to the national soil background values,such as As,P,Hg,Ni,Pb,Cr,Zn,Se,Org,etc.The standard value of N was significantly higher,and the standard value of Mo and K2O were lower,compared with the national soil background value.Study on the soil minerals composition and microstructure showed that the clay minerals in soil were mainly montmorillonite,kaolinite and illite.(2)The spatial distribution characteristics of nutrient elements were systematically analyzed,and it was concluded that the distribution of nutrient indexes such as organic matter,nitrogen and phosphorus in the study area was similar,and the high value areas were mainly distributed in the plain area,the high-value areas of K,Cu,Zn,Se and Mo were distributed in hilly area.Among them,the classifications of P,Org,Zn and Mo were relatively scarce,the classification of Se was relatively moderate,and the classification of Cu was mainly rich and abundant.The spatial distribution of elements in agricultural soil were revealed,such as Ni,Cr,As,Hg,Cd and Pb,and it was found that the high value areas of them were all distributed in hilly area.(3)The coupling relationship model between nutrient index and heavy metal index in soil was established,and the heavy metal content was accurately predicted.The main sources of heavy metals in the soil were studied.It was found that the heavy metals Cr-Ni-As in the soil of the study area mainly came from the parent material,and the high values of Cd and Hg in study area were mainly related to anthropogenic emissions and atmospheric sedimentation.Pb had dual sources of parent material and anthropogenic contribution.(4)The occurrence state of As,Cd and Hg in agricultural soil was studied.It was concluded that As and Hg were mainly in the residual form,and the bioactive state of Cd was relatively high,which indicated that Cd in the soil of the study area had certain activity.(5)Agricultural land evaluation system suitable for the study area was established by nutrient comprehensive index method and potential ecological risk assessment method,distribution characteristics of soil nutrients and ecological risk in the study area were systematically evaluated.It was concluded that the soil nutrients in the study area were relatively deficient,and the comprehensive potential ecological risk grades were mainly mild and moderate.