| Elemental arsenic is commonly found in soil,and its compounds are mostly toxic,and the available arsenic can well reflect the actual contamination status of soil and its harm to plants,so the study of available arsenic in soil of agricultural products origin has an important role in the analysis and evaluation of soil arsenic contamination.At present,there is no unified standard for the determination of available arsenic in soils of wheat producing areas at home and abroad,so it is necessary to develop measurement standards.In this study,the soil samples and wheat samples were mainly from Hebei province,at the same time,comparison and validation experiments were conducted with soil and plant samples from other wheat-producing areas of China,and the physicochemical properties and method validation were combined to increase the accuracy,scientificity and universality for the development of standards.The evaluation method and the risk evaluation model of soil available arsenic contamination were developed to systematically evaluate the safety of soil available arsenic in wheat-producing areas with the aim of achieving"soil-environment-food-safety".The main results of the study are as follows:（1）Principle coordinate analysis and cluster heat map analysis showed that the physicochemical properties of soils in different regions varied greatly,which might be an important factor affecting the extraction of available arsenic by extractants.Redundancy analysis showed that total phosphorus was significantly and positively correlated with AB-DTPA extractants and was the main environmental factor affecting the distribution of available arsenic in wheat-producing areas,and p H and available phosphorus were important environmental factors affecting available arsenic in wheat-producing areas.The correlation analysis between the extraction amounts of wheat fruits and rhizosphere soils,combined with the correlation analysis between the extraction amounts of wheat stems and leaves,root systems and rhizosphere soil,which leads to a conclusion that AB-DTPA was the optimal extractant.The experiments were conducted to optimize the conditions of AB-DTPA in terms of the three influencing factors of soil sample mass（liquid-soil ratio）,shaking time and shaking speed,which leads to the conclusion that 8g,60 min and 150 r·min-1were the optimal extraction conditions.（2）The results verified the accuracy of the extraction of the available arsenic content by AB-DTPA extractant by determining the recovery of the Tessier continuous extraction five-step method within the standard experimental range of 90%to 110%;The experimental methods were validated using atomic fluorescence analysis on the standard curve,method detection limit,lower limit of determination,precision,accuracy,actual samples and spiked recoveries,and the results met the scientific and integrity of the experimental determination standard study.It was finally concluded that the selection of AB-DTPA extractant could be the standard for the determination of available arsenic in soil of wheat-producing areas by applying atomic fluorescence analysis under the conditions of 8g of soil mass,50 m L of extractant,60 min of oscillation time and 150 r·min-1of oscillation speed.（3）The results of single-factor contamination index,Nemero contamination index evaluation method and wheat exposure and health risk analysis showed that the soil and wheat in all the collected areas were in the safe level and belonged to the non-contamination level,and the available arsenic content in wheat was in the safe consumption range.However,there is a risk of exposure to arsenic contamination,therefore,starting from the main sources of soil available arsenic,we have developed a risk evaluation model based on the standard of determination of available arsenic,which can be used to predict the wheat contamination index and risk evaluation level by the available arsenic content of soils,and then the safety evaluation of wheat-producing areas can be carried out systematically. |
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