| The use of passivator to remediate the safe use of cadmium-like contaminated farmland soil remediation technology,while production and remediation,because it can not affect agricultural production,has great advantages,has been widely used.However,current studies have only focused on the repair effect of the season,and the sustained repair effect of passivators is less understood.Therefore,the commonly used passivators,limestone(SH),Maiko fungus agent(MK),meerschaum(HP),iron-modified woody peat(TG),compound passivator(FH),weakly acidic bio-organic fertilizer(RS)and weakly alkaline bio-organic fertilizer(RJ),were selected for field experiments to study the effect of different passivators on cadmium-polluted farmland in two consecutive crops of rice restoration.At the same time,in order to improve the remediation effect of cadmium-polluted farmland by woody peat,a cadmium-activated material,sulfur modification was carried out.The specific results are as follows:(1)Effects of different passivators on soil pH and soil effective Cd content in paddy fields in two consecutive seasons.After the application of passivator after two crops of rice planting,SH-1500,MK-45,HP-1125,TG-3000,FH-3000 and RJ-3000 and other six passivation treatments had an effect on soil pH improvement,the increase range was 0.29～0.87,among which,FH-3000 treatment had the best effect on soil pH improvement,increasing by 0.87 units,pH value was 7.41.RS-3000 treatment has a reducing effect on soil pH due to its soft acidity,and the soil pH value is 6.41,which is reduced by 1.53%.The different treatments differed from the first quarter,with FH processing increasing the most,by 0.05 units.After two crops of rice planting,six passivation treatments,including SH-1500,MK-45,HP-1125,TG-3000,FH-3000 and RJ-3000,had a reduced effect on the effective cadmium content of soil,with a decrease of 7.6%～54.3%,among which the compound passivator FH-3000 treatment had the largest decrease in the effective cadmium content,which decreased by 54.3%,and the effective cadmium content was 0.301 mg/kg.The effective cadmium content of weakly acidic bio-organic fertilizer was 0.694mg/kg under RS-3000 treatment,which increased by 4.5%.The different treatments were different from the first quarter,with FH-3000 treating the largest decrease of 0.05mg/kg.(2)Effects of different passivators on Cd content of brown rice in two consecutive seasonsAfter the application of passivation agent after two crops of rice planting,SH-1500,MK-45,HP-1125,TG-3000,FH-3000 and RJ-3000 and other six passivation treatments had a reduction effect on the cadmium content of rice brown rice,the decrease range was 2.3%～72.1%,among which the compound passivator FH-3000 treatment,the cadmium content of rice brown rice decreased the most,decreased by 72.1%,and the cadmium content of brown rice was 0.066 mg/kg.Under the treatment of weakly acidic bio-organic fertilizer RS-3000,the cadmium content of brown rice in rice was 0.249 mg/kg,which increased by 5.1%.Compared with the first season,FH-3000 treated rice brown rice decreased the most,with a difference of 0.013 mg/kg.(3)Effects of different passivators on soil enzyme activity in rice in the second yearSeven passivators,including SH-1500,MK-45,HP-1125,TG-3000,FH-3000,RS-3000 and RJ-3000,had an increasing effect on sucrase and catalase in rice soil in the second year,with increases ranging from 4.3%-94.1%and 5.2%-23.1%,respectively.Among them,FH-3000 treated soil sucrase and catalase activities increased the most,and the sucrase activity was 17.58 mg·g-1·24h-1,which increased by 94.1%.Catalase activity was 2.91 mL·g-1h-1,which increased by 17.8%,which was significantly different compared with CK treatment(P<0.05),and urease activity in soil was increased by 44.6%in RJ-3000 treatment,with urease activity of 0.454 mg·g-124h-1.(4)Effects of different passivators on rice yield and quality in the second seasonSix passivation treatments,including SH-1500,MK-45,HP-1125,TG-3000,FH-3000,and RJ-3000,had an effect on rice yield in the second year,and TG-3000 had the best improvement effect,increasing by 13.3%and yielding 8661 kg/hm.However,after RS-3000 treatment,there was a significant downward trend in rice yield,with a decrease of 3.8%,and rice yield was 7378kg/hm2.After TG-3000 treatment,SH-1500,MK-45,HP-1125,TG-3000,FH-3000 and RJ-3000 were treated with the best brown rice rate and polished rice rate,which increased by 2.5%and 6.6%,respectively.After TG-3000 treatment,the chalk whiteness and chalk whiteness of rice decreased the most,by 42.5%and 49.3%,respectively.After TG-3000 treatment,the protein lifting effect was the best,with an increase of 13.5%;After TG-3000 treatment,amylose content decreased the most,with a decrease of 41.8%.After RJ-3000 treatment,the final viscosity of rice improved the most,with an increase of 13.1%.(5)Study on the preparation and characterization of passivator sulfur-modified woody peat biocharWood peat was calcined at 600℃ for CS2 modification to obtain sulfur modified woody peat,which was shown by SEM and EDS that the S element was loaded on the surface of the woody peat material.XPS and XRD analysis showed that the adsorption mechanism of woody peat biochar on Cd was mainly to generate Cd(OH)2 and CdCO3 precipitation,while sulfur-modified woody peat biochar also involved the interaction of Cd with organic sulfur to form more stable and insoluble and oxidized CdS and CdHS+.In order to study the effects of woody peat biochar(BC)and sulfur-modified woody peat biochar(SBC)on the adsorption rate of Cd,the adsorption data results were fitted with first-and second-order kinetic models.Therefore,it is concluded that the material conforms to the second-order kinetic adsorption model,and the ability of SBC to adsorb Cd is about 6 times that of BC.(6)Study on the effect of modified woody peat biochar on the remediation of Cd pollution in farmlandIn soil culture experiments,SBC and BC were put into 10mg/kg cadmium-contaminated soil according to different dosage amounts of 0.5%～5%,which had different effects on soil pH and effective Cd content,and after adding 1%SBC treatment,the soil pH value increased the most,increased by 12.5%,and the soil pH value was 7.52.In addition,after 1%SBC treatment,the effective Cd content in soil decreased the most,only 4.01mg/kg,and the difference was significant compared with CK treatment(P<0.05).The results showed that the biomass of ryegrass was lower than that of CK after SBC and BC treatment,indicating that BC and SBC could inhibit the absorption of cadmium by ryegrass.In addition,after SBC and BC treatment,the cadmium content in ryegrass decreased,decreasing by 70.7%and 40.7%,respectively.Among them,SBC decreased the most,down 70.7%,and the cadmium content in ryegrass was 0.87mg/kg. |
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