| With the increasing development of industry and urbanization,unreasonable emissions from activities such as metal smelting and mining have led to increasingly serious heavy metal pollution in farmland around mining areas,with Cd pollution being the most prominent.In recent years,soil heavy metal remediation technology has developed rapidly,among which in-situ passivation remediation technology is one of the commonly used technologies for Cd contaminated farmland soil remediation.However,the price of passivating agents is relatively expensive,which is divorced from practical application needs.Therefore,selecting more economical fertilizers with good passivation effects on heavy metals is of great significance in practical application remediation.This article uses soil culture and pot experiments to study Cd contaminated paddy soil and rice "Teyou 63".Different sulfur sources(sulfur,sodium sulfate)and calcium magnesium phosphate fertilizers and their combinations are selected as treatments.By measuring the soil available Cd content,soil Cd morphological characteristics,rhizosphere soil available Cd content,and rice agronomic indicators,the distribution and accumulation of Cd in rice roots,stems,and leaves are analyzed,The aim is to screen out effective passivation agent combinations and provide reference and basis for alleviating Cd pollution in rice fields.The main results are as follows:1.Through soil culture experiments,the effects of different sulfur sources(sulfur,sodium sulfate)and phosphorus fertilizers and their combinations(six treatments were set up: control(CK),calcium magnesium phosphate fertilizer(P),sulfur(S1),sodium sulfate(S2),calcium magnesium phosphate fertilizer+sulfur(PS1),and calcium magnesium phosphate fertilizer+sodium sulfate(PS2))on the availability and morphological transformation of Cd in paddy soil were studied.The results showed that the effective Cd content in the soil of each treatment was significantly reduced(P<0.05),with PS1 treatment having the lowest available Cd,which was 49.8% lower than CK treatment.P treatment can significantly(P<0.05)increase the soil pH value,which is 0.39 units higher than CK;P.PS1 treatment can significantly(P<0.05)reduce the soil Eh value,which is23.2% and 20.9% lower than CK,respectively,promoting the reduction of SO42-to S2-.PS1 treatment significantly increased the content of soil available phosphorus(P<0.05),and compared with CK,PS1 treatment increased soil available phosphorus by 81.9%.The combined application of sulfur and calcium magnesium phosphate fertilizers can synergistically promote the transformation of soil exchangeable Cd into residual Cd by regulating Eh,available sulfur,and available phosphorus.2.On the basis of soil culture experiments,the optimal sulfur source for matching calcium magnesium phosphate fertilizer was selected.A pot experiment was conducted to study the effectiveness of sulfur and calcium magnesium phosphate fertilizers and their combinations(four treatments were set up: control(CK),calcium magnesium phosphate fertilizer(P),sulfur(S1),and calcium magnesium phosphate fertilizer+sulfur(PS1))on Cd uptake in rhizosphere soil and rice.The results showed that the combination of sulfur and calcium magnesium phosphate fertilizer treatment had the lowest effective Cd content in the rhizosphere soil,which was 39.5% lower than the CK treatment,consistent with the effect of reducing the effective Cd content in non rhizosphere soil in soil culture experiments.PS1 treatment can significantly(P<0.05)increase the biomass of roots,stems,and leaves in rice,which is 76.5% and 23.1% higher than CK treatment,respectively.The application of sulfur and calcium magnesium phosphate fertilizers can significantly increase(P<0.05)the content of phosphorus and sulfur in various parts of rice,promoting the growth and development of rice plants.The Cd content in various parts of rice treated with PS1 was the lowest.Compared with CK treatment,the Cd content in roots,stems,and leaves decreased by 46.3%,54.3%,and 59.1%,respectively,which significantly reduced the absorption of Cd by rice(P<0.05).Soil culture experiments conducted with different sulfur sources(sulfur,sodium sulfate)and calcium magnesium phosphate fertilizers and their mixtures showed that PS1 treatment had the best effect in reducing the effectiveness of Cd in paddy soil,effectively promoting the transformation of exchangeable Cd into residual Cd in the soil.Pot experiments conducted with sulfur and calcium magnesium phosphate fertilizers and their combinations found that the PS1 treatment had the lowest effective Cd content in the rhizosphere soil.Moreover,the PS1 treatment promoted the absorption of phosphorus and sulfur by rice,affected the absorption of Cd by rice roots,and inhibited the transport of Cd within rice tissues,thereby reducing the accumulation of Cd absorption by rice plants.The research results provide effective information for reducing the bioavailability of Cd in paddy soil and inhibiting the enrichment of Cd in rice. |
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