Study Of Reducing Of Biovalability And Accumulation Of As And Cd On Rice In As-Cd Combined Pollution Soil By Si Based Soil Amendment Combined With Water Management

In southern China,the problem of soil Cd-As combined pollution has become more and more serious.It has become a research hotspot in recent years to govern the Cd-As combined pollution of farmland soil and ensure the quality and safety of rice.Water conditions can inhibit the absorption and accumulation of heavy metals Cd by rice brown rice,while the adsorption and solubility of heavy metals Cd and As in soils have the opposite properties of absorption and enrichment by rice.Common single control measures,such as water management,application of deactivators,etc.,cannot simultaneously inhibit rice.Absorption and accumulation of Cd and As.In order to explore new ideas for blocking control,the activities of heavy metals in Cd-As combined pollution soil were controlled and scientific theoretical basis and control products were provided for safe rice production.In this paper,a typical cadmium-arsenic compound contaminated soil in Hunan Province is taken as the research object.Through three groups of outdoor rice pot experiments,two types of silicon fertilizer,silicon-containing bamboo charcoal and silicon-containing rice husk were applied under flooding conditions.Two types of biochar carbon,manganese modified bamboo charcoal,manganese modified rice hull carbon,and two kinds of manganese modified silicon-containing materials were used to study the effects of differentsilicon-containingamendmentsandfloodingmeasureson As-Cd-contaminated Cd and As biota in paddy soils.Effectiveness and Accumulation of Rice and Its Application Value.The main test results are as follows:?1?The effect of wet irrigation?CK?,agronomic measure flooding?F?,instantaneous silicon fertilizer combined with flooding measures?FYsi?,mineral silicon fertilizer combined with flooding measures?FKsi?,and a mix of two kinds of silicon fertilizer combined with flooding measures?FYK?on the bio-availability of As and Cd in soil and the accumulation of As and Cd in rice were investigated by pot experiments.The results showed that the pH of the soils combined with flooding measures was increased by 0.12-0.72 units with similar trends of an increase and then a decrease before finally become neutral.The Eh of the soil combined with flooding was significantly decreased,but the Eh of soil after flooding treated by FYsi,FKsi,and FYK combined with the flooding was significantly higher than that treated by F,and the content of Cd in brown rice was reduced by 38.83%-65.05%compared with that treated by CK.The F and FYK treatments can significantly reduce the accumulation of Cd in brown rice,resulting in the lowest Cd contents in brown rice of 0.98 and 0.72 mg·kg^-1,respectively.The contents of As in brown rice treated by FYsi,FKsi,and FYK were decreased by 23.80%,38.10%,and 47.62%,respectively,compared with that with the CK treatment,except that the content of As in brown rice treated by F increased by 36.64%.FYsi and FYK treatments had the best inhibitory effect on the accumulation of As in brown rice,with the lowest As contents of 0.13 mg·kg^-1and 0.11 mg·kg^-1in brown rice?P<0.01?,respectively.There was an extremely significant correlation between the contents of extractable Cd and the total content of Cd in the brown rice?P<0.05?,and there was no significant difference between the contents of extractable As and the total content of As in the brown rice.Therefore,FYsi,FKsi,and FYK can effectively inhibit the accumulation of Cd and As in rice grown in Cd-As compound polluted soil,and FYK showed the best performance?2?In this study,The effect of?CK:wet irrigation,F:agronomic measures flooding,ZC:bamboo charcoal,ZF:bamboo charcoal with irrigation,GC:chaff carbon,GF:chaff carbon with irrigation?on the bioavailability of As and Cd in soil and the accumulation of As and Cd in brown rice.The results showed that the pH increased by 0.12 to 0.72 units for all the six treatments which showed the increasing trend firstly and then decreasing to neutral.Compared with the CK,the Eh of the other five treatments showed a downward trend.However,the Eh of the ZC and GC treatments were significantly higher than that of the F,ZF and GF treatments with biochar during the same growth stage and was maintained in a weak reductive state.The content of Cd in brown rice treated with F,ZF and GF flooded with biochar decreased by 51.46%⁵7.28%,and the optimal inhibition effects for Cd were achieved by the GF and F which is significant different from ZF.The content of As in the grain reached 0.29,0.32 and 0.30mg·kg^-1,which were 39.74%-53.58%higherthan that of the CK.The content of Cd in brown rice decreased by 16.50%and39.81%,while the content of As in brown rice increased by 27.24%and 12.23%,respectively.However,there was no significant difference between GC and CK.GC treatment with single addition of biochar could be used to contaminate the farmland with cadmium and arsenic in the soils,and could provide theoretical basis for food safety production on Cd-As contaminated paddy soils.?3?The experimental results of two manganese-modified silicon-containing materials prepared with different biochars as matrix showed that several treatments could significantly reduce the acid-extractable content of cadmium in the soil,and the T9 cadmium-reducing effect was best reduced by 20.79%.Followed by T3,T5 two kinds of treatment.Four kinds of treatments with different amounts of Zc and Gc activated residual arsenic into other forms of arsenic.With the increase of the application amount of the same kind of material,the risk of arsenic in soil was increased.The bioavailability of four treatments of arsenic with different amounts of Gc-Mn and Zc-Mn decreased with increasing application rates.The two treatments of Zc had a cumulative effect on As in brown rice,while Zc-Mn had an inhibitory effect on arsenic enrichment in brown rice.For both T5 and T4 treatments,the arsenic reduction rate reached 52.29%and 27.52%,respectively.With different amounts of modified and unmodified silicon-containing materials Gc and Gc-Mn,the effect of arsenic reduction was T9>T8>T7>T6,and the cadmium reduction rates were 66.06%,53.67%,50.92%,and 26.61%,respectively.The content of arsenic in brown rice was0.07 mg·kg^-1,0.10 mg·kg^-1,0.10 mg·kg^-1,and 0.16 mg·kg^-1.Four treatments with different amounts of Gc-Mn and Zc-Mn could effectively control the Cd-As combined pollution of rice,and with the increase of application amount,it could better control the migration of Cd and As in soil-rice.Comprehensive comparison,silicon fertilizer,rice husk carbon and manganese modified biochar can achieve the combined effect of Cd-As inhibition,and silicon fertilizer is a material with a relatively low economic cost and a good repair effect.The research results can provide data support and scientific reference for the safe production of Cd-As compound pollution farmland in typical southern mining areas,and have strong practical value.