Optimization and validation of lead effective state analysis method ( AB-DTPA ) in farmland soils

The soil type in China are rich and diverse, and the occurrence forms of heavy metals in different regions are different. It is difficult to compare and evaluate the effectiveness of heavy metals in different regions and different types of soils. In order to screen and establish a method for evaluating the effectiveness of heavy metals in farmland soils in suitable areas, five typical farmland soils (yellow brown soil, yellow soil, red soil, lime soil and purple soil) with different properties in eastern Yunnan were selected. The extraction conditions (solid-liquid ratio, extractant pH value and oscillation time) of AB-DTPA method were orthogonally combined by orthogonal test, the soil-crop Pb migration model was established to compare the goodness of fit with the total method, CaCl₂-DTPA method and AB-DTPA method. Pot experiments were carried out with Chinese cabbage and spinach as indicator plants to explore the correlation between different analysis methods and plant Pb accumulation ability, and then comprehensively evaluate the suitability of different methods.The results showed that the solid-liquid ratio (g/mL) 1:3, pH 7.6 and shaking time 120 min had a great influence on the extraction amount of Pb; The optimized AB-DTPA method (solid-liquid ratio (g/mL) 1:3, pH 7.6, and oscillation time of 120 min) obtained through orthogonal experimental screening has the best effect on predicting the effective state extraction amount of Pb and the amount of Pb absorbed by crops, which can better predict the crop's ability to absorb Pb; The pot experiment showed that the available Pb content extracted by the optimized AB-DTPA method had a better correlation with the Pb content absorbed by Chinese cabbage and spinach ( R² = 0.898, R² = 0.752 ), with a Pb spiked recovery rate range of 99.5%-113.0% and high accuracy. Therefore, the optimized AB-DTPA method (Solid-liquid ratio 1:3, pH 7.6 and shaking time 120 min) is suitable for the extraction of Pb available state in Yunnan farmland soil. The method is feasible, universal and accurate. The research results provide a basis for the effect of regional farmland soil remediation technology and pollution risk assessment.