Effects Of Heavy Metal Copper On Rice Growth And Risk Assessment In Red Soil Paddy Soil

In order to clarify the effects of heavy metal copper stress on rice growth and risk assessment under high iron content in red soil,the paper adopted field sampling survey and potted simulation experiment to select the red soil paddy soil region of Le’an River Basin polluted by copper mine as field.The sampling and investigation area was used to collect and analyze the soil and rice samples in the main polluted areas in the area.The physical and chemical properties of the soil,the contents of heavy metals Cu and Fe in soil and rice,and the physical and chemical properties of the soil and heavy metals Cu and Fe were analyzed.The correlation between the soil and rice heavy metals Cu and Fe in the Le’an River Basin and the migration of heavy metals Cu and Fe in soil and rice were evaluated,and the risk of heavy metal Cu pollution in the study area was evaluated.On the basis of this,the effects of heavy metal Cu stress on the growth of rice under high iron content in the red soil of Loan River Basin were simulated by exogenous addition of heavy metals Cu and Fe.The growth indexes of plant height(leaf height,leaf area,tiller number and Relative yield)and physiological indicators(chlorophyll content,superoxide dismutase(SOD),peroxidase(POD),catalase(CAT)and malondialdehyde(MDA)activity),and comprehensive index for each index The analysis reveals the effect of heavy metal copper stress on rice growth under high iron content in paddy soil in red soil,aiming at optimizing rice quality for safe production and improvement of rice,and providing scientific basis for prevention and control of heavy metal pollution.The main conclusions are as follows:(1)The soil pH of each sampling point in the study area is less than 7,showing acidity;the average content of heavy metal Cu in soil exceeds the background value of heavy metal Cu in Jiangxi soil by 7 times,exceeding the national agricultural land risk control standard(GB15618-2018)5 times;the average content of heavy metal Fe element is more than 28 times that of China’s soil background value,which is 20 times higher than the world soil background value.There was a negative correlation between soil pH and EC value and content of heavy metals Cu and Fe in soil.There was a positive correlation between soil CEC and OM values and soil Cu and Fe contents.In addition,the two elements of Cu and Fe in the soil also showed a very significant positive correlation.(2)Cu and Fe in various parts of the rice in the study area showed a trend of decreasing along the river direction at the maturity stage of each sampling point.Cu and Fe accumulated in various parts of rice at each point were: root>stem >Leaf>The law of rice.(3)The bioconcentration coefficients of heavy metals Cu and Fe in all parts of rice in the study area showed roots>stem>leaf>rice,indicating that rice roots are the main enrichment of heavy metal elements;rice at different sampling points The bioconcentration coefficient(BCF)of each part decreased with the increase of Cu and Fe contents in the soilat the sampling point,indicating that the bioconcentration coefficient(BCF)of various parts of rice was inversely related to the contents of Cu and Fe in soil heavy metals.(4)The single factor pollution index(PI)of heavy metals in rice at each sampling point in the study area was greater than 1.0,indicating that the content of heavy metal Cu in the rice in the study area exceeded the standard;75% of the sampling points in the rice heavy metal Cu high risk commercial index(HQ)above 1.0 indicates a significant health risk in rice in the study area.(5)With the exogenous Cu,Fe and its combined stress,the growth indexes of rice showed a trend of increasing first and then decreasing.When single exogenous Fe stress,the plant height,tiller number and leaf area reached the maximum when the exogenous Fe concentration was 400 mg/kg,and the relative yield reached the maximum when the exogenous Fe concentration was 200 mg/kg.In a single exogenous Cu stress,rice plant height,tiller number and leaf area reached a maximum when the exogenous Cu concentration was 100 mg/kg.The rice yield showed a continuous decline,and reached a minimum when the exogenous Cu concentration was 300 mg/kg,and the relative yield was68.8%.When exogenous Cu and Fe were combined,the plant height,tiller number,leaf area and rice yield reached the maximum when the copper concentration was 100 mg/kg and the iron concentration was 200 mg/kg.After that,the growth indexes began to decline.When the copper and iron stress concentrations were 300mg/kg and 800mg/kg,respectively,the growth indexes reached the lowest value,and the rice was withered at this time.(6)High-iron-bearing red soil cultivated soil(exogenous Fe ≦ 400 mg/kg)in the absence of exogenous Cu is conducive to the growth and development of rice,and has no low concentration of Cu(≦100 mg/kg)in the exogenous Fe background.The combination of low concentration of Cu(≦100 mg/kg)and Fe(≦200 mg/kg)promoted the growth of crops and induced SOD,POD and CAT activities in rice leaves.However,when the exogenous Fe concentration exceeds 800 mg/kg or the Cu concentration exceeds 200mg/kg,although the antioxidant enzymes SOD,POD and CAT activities are significantly induced,the growth of rice begins to be significantly affected.(7)IBR comprehensive analysis showed that exogenous Cu stress had a greater effect on the comprehensive effects of rice biomarkers than exogenous Fe stress.(8)Under the exogenous Cu and Fe and their combined stress,when Cu concentration is 100mg/kg and Fe concentration is 200mg/kg,it is most suitable for rice growth.