Study On Passivation Of Mild Cadmium Pollution In Vegetable Soil

With the increasingly severe heavy metal pollution in vegetable fields,more and more attention has been paid to the safe production of vegetables,and the remediation of heavy metal pollution in vegetable fields has also become a popular research topic among experts and scholars.Relevant findings show that the application of passive materials and the planting of low-accumulation varieties are both effective ways to remedy heavy metal pollutions in vegetable fields,but the application of passive materials increases the agricultural production cost to a certain extent.If the applied passive materials are not properly tested and screened in conjunction with the vegetables planted locally,the heavy metal reduction effect in soil may not be obvious,and the content of heavy metals in vegetables cannot be reduced below the national standard,etc.Therefore,it is of great significance to conduct relevant studies on passive materials and vegetable varieties.In order to study the remediation effects of different kinds of passive materials on vegetable fields with slight cadmium(Cd)pollution,field experiments were conducted in this study on vegetable fields with slight Cd pollution to analyze the correlation of the application of lime,nano remediation materials(SAMMNS),and calcium magnesium phosphate fertilizer with Cd contents in different vegetables,with available Cd content,p H value and nutrient content in soil,as well as with how different Cd contents in vegetables vary with available Cd content in soil,p H value of soil,and organic matter content in soil.The main findings are summarized as follows:1)Under the same treatment conditions,the rank of enrichment degrees of vegetables on Cd in soil is: water spinach > spinach > Chinese cabbage > capsicum > cabbage > pakchoi >ginger > water dropwort > radish > sweet potato > leek.2)The nanomaterials and lime can reduce Cd content in vegetables to a certain extent by4.19%-42.33%.To be specific,the nanomaterials can reduce the Cd content in cabbage,pakchoi and ginger that exceeded the content(0.05mg/kg)stipulated in National Food Safety Standard,bringing it to an acceptable level.The results of each treatment and repair of vegetables in three seasons showed that the three repair materials applied in three consecutive seasons had the best effect of the nanomaterials treatment.The results of lime treatment in the first season were better than those in the second and third seasons.The effect of calcium magnesium phosphate fertilizer treatment was not obvious in the first and second quarters,but improved in the third quarter.3)The nanomaterials,lime and calcium magnesium phosphate fertilizer can increase thep H value of soil significantly by 0.25-0.65.To be specific,lime treatment was the most effective in the first quarter,and the nanomaterials treatment was the best in the second and third quarters.4)The nanomaterials,lime and calcium magnesium phosphate fertilizer can reduce the available Cd content in soil to a certain extent,i.e.,by 2.86%-25.95%,among which the nanomaterials treatment had the best quarterly reduction effect and obvious reduction effects.Compared with the first season,the content of available Cd in the soil of the three treatments in the second season decreased obviously.However,compared with the second season,there was no significant change in the content of Cd in the soil in the third season.5)The nanomaterials and calcium magnesium phosphate fertilizer can improve the content of organic matter and nitrogen,phosphorus and potassium in soil to some extent.The range of increase of organic matter,alkali-hydrolyzable nitrogen,available phosphorus and rapidly available potassium were 3.99%-12.37%,2.55%-13.59%,3.14%-27.66%,and11.89%-18.45% respectively.6)Cd content in vegetables is positively correlated with the available Cd content in soil,while available Cd content in soil is negatively correlated to a very dramatic extent with soil p H and organic matter in soil.