Effects Of Mercapto Modified Palygorskite On Reducing Cadmium Uptake Of Crops And Its Mechanism

With the development of agriculture and industry,plenty of pollutants enter soil environment through different ways,coursing serious problem.Cadmium is one of heavy metal elements with high biological toxicity,which has the characteristics of high chemical activity,mobility,long-lasting in soil,and is easy to endanger human health through the enrichment of the food chain.It is important to how to choose a high efficiency,cheap,applicable to the status quo of our repair method.In-situ passivation repair technology is simple and easy to operate,suitable for a wide range of mild to moderate heavy metal contamination,can change the existence forms of heavy metals,which will be fixed in the passivation agent.In this paper,pot experiments of rice and rape were conducted to study the properties of Cd-contaminated palygorskite on Cd-contaminated farmland soil,Cd transformation,distribution of Cd uptake by rice and rape,soil enzyme activity of rapeseed,and antioxidant enzyme system and low-molecular-weight mercapto compound of rice.The impact and mechanism are of great significance for the effective restoration of soil heavy metal cadmium pollution,reducing the content of heavy metal cadmium in crops,ensuring food security in China and protecting human health.Rice pot experiment results showed that after adding different doses of thiol modified palygorskite,the two rice varieties significantly reduced the cadmium content in brown rice,cadmium contents in brown rice of rice varieties CX-8 and TY-272,were reduced by 17.5%-17.5% and 47.4%-65.4%,respectively,both the cadmium content in brown rice rice varieties under standard of food hygiene in our country the limit of 0.2 mg/kg(GB2762-2017).The addition of mercapto modified palyzolite inhibited the transfer of cadmium from rice root to rice grain and reduces the transfer coefficient of cadmium.The contents of DTPA extractable cadmium were decreased with the addition of mercapto modified palyzolite,and the content of cadmium in the iron plaque of rice root decreased.The addition of mercapto modified palyzolite made the superoxide dismutase(SOD),catalase(CAT)enzyme activity and total antioxidant capacity(T-aoc)of rice root decreased.The total sulfhydryl(T-SH)and metallothionin(MT)content of rice root decreased.Rape pot experiment result showed cadmium contents in rape aerial of two seasons significantly reduced by mercapto modified palygorskite addition;cadmium contents of the first and second season were reduced by 36.4%-75.5%.The contents of DTPA extractable cadmium in rape soil were obviously decreased with the addition of mercapto modified palygorskite.With the mercapto modified palygorskite addition,soil catalase(CAT)and peroxidase(POD)showed the tendency of decrease of first season,and a trend of increase of the second season,activities of soil urease(UE)and invertase(SC)increase.It was concluded that mercapto modified palygorskite can be effectively fixed cadmium of paddy soil and canola,reduce biological availability of soil heavy metal cadmium in the paddy fields and rape,alleviated the oxidative stress of soil cadmium pollutant in rice?rape,effectively repair paddy soil and canola soil cadmium pollution.