Effects Of Arsenic Concentration In Irrigation Water And Improvers On Rice Yield,Quality And Arsenic Concentration

With the increasingly prominent environmental pollution and other issues,rice as China's first staple food,its quality and safety issues have aroused great concern in society.With the continuous development of the industrial field,heavy metals cause water and soil pollution,which leads to farmland pollution.The problems such as excessive heavy metal content in crops,low quality of crops and yield reduction,pose a serious threat to China's economy,ecological environment,food safety and people's health.Therefore,it is of great significance to solve the heavy metal pollution in farmland and establish the value of sewage irrigation system based on food limit standards for ecosystem health.This project intends to carry out the outdoor potted rice split plot experiment,using the water quality standard of irrigation water?As<0.05mg/kg?,select the concentration of arsenic in irrigation water?O,0.00mg/kg of arsenic in irrigation water;As,0.05mg/kg of arsenic in irrigation water?for irrigation.Soil heavy metal amendments?zeolite,SZ;rice husk biochar,SC₁;and corn straw biochar,SC₂?,were selected to investigate the effects of three amendments on rice growth and yield under the condition of arsenic concentration in irrigation water,on rice quality,physical and chemical properties of paddy soil and arsenic accumulation in crop system.By constructing regression model,the relationship between arsenic content in rice and total arsenic content in crop system and yield was explored.The main results are as follows:?1?The effects of three modifiers on rice growth and yield were not significant under arsenic concentration in irrigation water:the effect on rice growth was not significant because arsenic concentration inhibited the promotion of rice growth;the effect of modifiers on rice yield under standard irrigation water quality was not obvious,possibly because zeolite and biochar absorbed heavy metals and occupied zeolite and biochar.In the lattice structure of biochar,the exchange site of ammonia nitrogen caused no significant synergistic effect.?2?The effects of three amendments on rice milled rice rate,chalkiness and hygienic quality were significant under the concentration of arsenic in irrigation water:in the absence of amendments,the milled rice rate of As treatment decreased by 0.85%compared with that of O treatment;in the presence of three amendments,the milled rice rate of OSZ group,OSC₁group and OSC₂group increased by 2%respectively.Compared with As SO group,the milled rice rate of As SZ group,As SC₁group and As SC₂group increased by 5.4%,7.61%and 1.52%respectively.The order of improvement of milled rice rate by three amendments was SC₁>SZ>SC₂.Compared with O treatment,the chalkiness of As treatment was improved by 0.3%.The chalkiness of As treatment was decreased by 0.2%,0.05%and 0.1%after three kinds of improvers were applied.Compared with As SO group,the chalkiness of As SZ,As SC₁and As SC₂groups was decreased by 0.2%,0.05%and 0.1%respectively.The order of reducing chalkiness of the three improvers was SZ>SC₂>SC₁,and the order of reducing chalkiness of the three improvers was SZ>SC₂>SC₁.The milled rice rate and chalkiness of rice before and after treatment can reach the standard of green rice.Compared with O treatment,the arsenic content in rice treated with As increased significantly,reaching 0.153mg/kg,exceeding 0.15mg/kg in the standard of green rice,and decreased significantly to 0.138 mg/kg,0.132mg/kg and 0.130mg/kg after three different amendments were applied.The order of reducing arsenic in rice was SC₂>SC₁>SZ.?3?The effects of three amendments on soil physical and chemical properties of paddy field were significant under the concentration of arsenic in irrigation water.After applying three amendments under O treatment and As treatment,compared with O treatment,the contents of soil organic matter,total nitrogen,total phosphorus and p H in As treatment decreased by 3.9%,16.9%,4.4%,1.7%respectively without amendments,which had a negative impact on soil physical and chemical properties.The degree of influence was As>O.The effects of three amendments on soil physical and chemical properties were SC₂>SZ>SC₁.Under O treatment,the total nitrogen in soil increased by 2.5%,1.6%and 4.2%compared with OSO group,OSZ group,OSC₁group and OSC₂group respectively.Under As treatment,compared with As SO group,total nitrogen in soil increased by 19.4%,16.3%,22.4%in As SZ group,As SC₁group and As SC₂group,respectively.Regression analysis showed that soil nitrogen content could be reduced by adding amendments,and rice yield could be indirectly improved.?4?Under the concentration of arsenic in irrigation water,the arsenic concentration in rice organs was significantly affected by three amendments:root>stem>leaf>milled rice in all parts of the crop system;under the condition of no amendment,the arsenic concentration in roots,stems,leaves and milled rice in As treatment was increased by 4.6%,16.3%,4.7%,3.4%compared with that in O treatment,respectively.Compared with As SO group,As SC₂group in As SZ group reduced arsenic in rice roots by 19.1%,23.0%,34.1%,stems by 17.1%,29.8%,39.4%,leaves by 11.3%,19.04%,35.36%,milled rice by 9.8%,13.7%and 15.0%,respectively.The maximum reduction rate of arsenic in edible part was 74.60%in OSC₂group,and the transporting coefficient after application of modifier was all higher.The reduction is far less than 1.Through regression analysis.The arsenic content in milled rice and total arsenic content in crop system can be reduced by adding amendments,which can indirectly improve rice yield.In summary,it can be concluded that there are adverse effects of arsenic concentration in irrigation water on rice yield,quality,physical and chemical properties of soil and arsenic accumulation in crop system.