| The use of chelating agents to strengthen plants to repair heavy metal contaminated soil has attracted the attention of scholars at home and abroad,and has made breakthrough progress.This article takes arsenic contaminated soil in antimony smelting sites as the research object and conducts arsenic pollution in 5 different areas of the research area The surface layer and profile were analyzed for As content and occurrence form,and the regional soil with high arsenic content was selected as the test soil.Three new biodegradable aminocarboxylic acid chelating agents,ethylenediamine,were explored through the indoor static activation test Disuccinic acid(EDDS),glutamic acid diacetic acid(GLDA)and methylglycine diacetic acid(MGDA)and the traditional chelating agent ethylenediaminetetraacetic acid(EDTA)are effective for soil pH value and biological under different concentration and time conditions The effect of the As content and the arsenic occurrence form was selected to select the appropriate time and concentration,and then through the pot experiment of centipede planting combined with the addition of chelating agent,the ability of the chelating agent to strengthen the centipede grass to repair arsenic-contaminated soil was explored:(1)There are obvious differences in the total arsenic content of the soil in different areas of the antimony mining area,specifically as follows:Xuan Shiping(60.53 mg·kg-1)>residential area(42.07 mg·kg-1)>tailings area(36.69 mg·kg-1)>Smelting area(31.84 mg·kg-1)>Farmland area(15.05 mg·kg-1),all of which exceed the soil background value of Hunan Province.The soil selected in the Shipingping area with the highest total arsenic content was selected as the research obj ect.(2)The arsenic in the test soil is mainly residual arsenic(51.82%?79.00%of the total arsenic),and the content of bioavailable arsenic is extremely low,of which exchangeable arsenic and surface adsorbed arsenic account for 1.00%?5.82%and 0.06%?0.53%,and the total arsenic and various forms of arsenic generally show a trend of rising first(0?40 cm soil layer)and then decreasing to a stable trend with the increase of soil profile depth.Total arsenic and five forms of arsenic are mainly distributed In the shallow soil layer(0?40 cm).(3)In the indoor static activation test,all four kinds of chelating agents can increase the soil pH.Among them,the pH value increased most significantly on the 28th day of EDTA activation,and the most significant improvement on the other three kinds of chelating agents on the 7th to 14th days,and The higher the concentration of the chelating agent,the more significant the effect of increasing the pH value,but the pH value of each treatment group gradually returned to the initial level with time.The content of bioavailable As in soil increased under the activation of 4 chelating agents,and the effect was the best when it was activated on the 28th day of EDTA(10.00 mmol·kg-1).The content of bioavailable arsenic reached 3.66 mg·kg-1,76.88%higher than the original soil.Other chelating agents showed the best effect of increasing the content of bioavailable arsenic at 28?35 days after activation at high concentration(10.00 mmol·kg-1).(4)The overall occurrence of arsenic in the soil in the static activation experiment showed that the activation effect of arsenic was better when the EDTA concentration was 1.25 mmol·kg-1,F5 decreased by 9.12%?34.21%compared with the original soil,and F4 and F3 increased by 27.61%?117.44%and 10.78%?53.98%;EDDS at 1.25 mmol·kg-1 had a good activation effect after day 14;F5 decreased by 16.93%?39.96%compared to the original soil;F4 and F3 increased by 56.90%?128.27%and 6.80%?73.23%;GLDA and MGDA have the same ability to activate soil arsenic,which is slightly weaker than EDTA and EDDS.(5)Indoor pot experiments showed that the four chelating agents can significantly increase the biomass of centipede grass at a concentration of 1.25 mmol·kg-1,and the maximum biomass of centipede grass is 4.48 when the concentration of MGDA is 1.25 mmol·kg-1.4.48 g·pot-1,an increase of 51.3%over CK.As the concentration of the chelating agent increased,the residual As content in the rhizosphere soil of Centipede decreased,and the bioavailable As content in the rhizosphere soil was the highest when the EDDS concentration was 10.00 mmol·kg-1,which was 69.2%higher than that of CK.EDTA,GLDA and MGDA began to inhibit the growth of Centipede at the concentration of 10.00 mmol·kg-1,but it could still increase the BCF of Centipede on As.The concentration of Centipede at the concentration of 5.00 mmol·kg-1 was the highest.Is 7.99,which is 1.7 times of CK. |
PDF Full Text Request