| Previous studies have confirmed that arsenic is one of the five toxic elements.Arsenic in the soil is related to the soil parent material.The physical and chemical properties of different parent materials are different,on the other hand,it is related to the exogenous input pathway.The arsenic and toxicity of crops are different from the soil properties and crop varieties or varieties.Generally,the arsenic toxicity of the rice field rice system is generally believed to be greater than that of the dry soil.Hunan is a big province of rice production.It is not only a soil parent,there are many soil types,but also the arsenic and mineral resources are rich.Therefore,it is very important to warn and control the arsenic pollution of rice paddy rice system.This study was based on "investigation and compilation of soil series in Hunan Province(2014FY110200)",a total of 274 soil samples in 51 profiles were collected from 5 kinds of parent paddy soils in eastern and northern Hunan Province.The total arsenic,available arsenic and basic physical and chemical indexes of the soil were analyzed and determined.The distribution of arsenic in five parent paddy soils and the relationship between arsenic and physical and chemical properties of paddy soils were studied,and the effects of arsenic on the growth and development of early rice were studied by pot experiment of adding arsenic to three parent paddy soils.Effects of yield and arsenic uptake by Rice.The conclusions are as follows:(1)The total arsenic content in the whole layer of the five parent paddy soils varied greatly,and the difference was above 2mg/kg.The highest content of arsenic in yellow mud was 19.62 mg / kg,followed by 16.86 mg / kg in river mud and 5.79 mg / kg in Ma Sha mud.The maximum of available arsenic in the whole layer of the section is 0.15 mg / kg in the sediment,and the other four paddy soils are below 0.12mg/kg,the average value is 0.10 mg / kg.The difference of total arsenic and available arsenic content between sections was the smallest in red yellow mud,the coefficient of variation was 20% and 25%,and the maximum in river sediment was 39% and 43%.The difference of total arsenic distribution was less than that of available arsenic.(2)The total arsenic in the cultivated layer of five parent paddy soils was higher in river sand mud and yellow mud field(16.85 mg/kg and 16.23 mg/kg,respectively).The other paddy soils were lower than the first grade standard value of soil environmental quality(15 mg/kg),which were 13.39 mg/kg(red yellow mud)10.87 mg/kg(purple mud)and 5.70 mg/kg(granitic sandy mud),respectively.The available arsenic in tilling layer was river sediment(0.203 mg/kg)? yellow mud(0.198 mg/kg)? red yellow mud(0.186 mg/kg).The content of available arsenic in purple mud and Ma Sha mud was lower,the lower values were 0.127 mg/kg and 0.115 mg/kg.(3)Compared with different soil layers,total arsenic content was the highest in plow bottom layer(13.87 mg/kg),followed by water-tillage redox layer(13.32 mg/kg,tilling layer(12.61 mg/kg),available arsenic(0.168 mg/kg)> plow bottom layer(0.126 mg/kg)> water redox layer(0.100 mg/kg).The difference of distribution of total arsenic and available arsenic in different soil layers was the biggest in the bottom of plough,the coefficient of variation was 39% and 46%,respectively.The average value of total arsenic distribution was 32% and 37%,respectively.And the difference of total arsenic distribution was less than that of available arsenic.The ratio of available arsenic to total arsenic in different paddy soils was 1.34% in granitic sandy mud,0.82% in yellow mud,and close to 1% in other paddy soils.(4)Correlation analysis showed that there was a very significant positive correlation between available arsenic in soil and total arsenic content,and a very significant positive correlation between soil total arsenic and soil free iron oxide,clay(< 0.002 mm)and silt(0.05 mm),but a very significant negative correlation with sand(0.05~2 mm).Soil available arsenic and soil organic matter pH,total phosphorus and silt were significantly or positively correlated,respectively,and negatively correlated with sand.(5)The pot experiment results showed that there was no significant effect on the treatment and soil in 0~10 mg/kg,and the rice plant height,tiller number and rice yield were significantly decreased when adding arsenic 20 mg/kg.The yield of red and yellow mud was reduced by 47.2%~84.8% and that of Ma Sha mud was reduced by 24.8%~48.6%,respectively.With the increase of arsenic concentration in the soil,the total arsenic content of rice straw and milled rice increased with the increase of arsenic concentration.As the addition arsenic above 20mg/kg,the arsenic content of straw and milled rice all increased more than 100% compared with the control treatment in 3 kinds of paddy soil.However,the total arsenic content of milled rice in three kinds of paddy soils was not higher than the national grain total arsenic standard(0.7 mg/kg,GB4810-1994).Correlation analysis showed that plant height,tiller number and dry weight of rice were significantly negatively correlated with available arsenic content in paddy soil. |
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