| The problem of soil pollution at this stage in China is gradually serious.Among all of those soil pollution,heavy metal pollution is the main type of soil pollution.It has threatened people’s agriculture activities and life safety seriously.Therefore,a method is needed to solve the heavy metal pollution.Phytoremediation is considered the most feasible and practical method for remediation of soil heavy metal pollution.One of the methods is to use hyperaccumulator plants to extract heavy metal from the soil to achieve the purpose of efficient remediation.Sedum alfredii Hence is a kind of plant grow in the mining environment,which can tolerate heavy metal pollution and has a strong adsorption capacity for cadmium.However,in the current experiments in phytoremediation field,it has been found that there are many limitations in the use of hyperaccumulator plants for phytoremediation,such as slow growth,short and small plants.Therefore,some studies have focused on finding strengthening methods for phytoremediation,and the most effective way is using some small-molecule inorganic modifiers to chelate soil heavy metal elements and increase the absorption of hyperaccumulator plants.But,small-molecule inorganic modifiers have the defects of easy degradation and short duration,easy migration and could cause secondary pollution.so this experiment was designed to use polymer compounds as modifiers to provide more data basis for solving practical problems in the field of phytoremediation.This experiment is based on systems science,ecology,polymer chemistry and designed a pot experiment.The Sedum alfredii was planted on the soil contaminated by lead,cadmium and arsenic,and 12 kinds of polymer compounds(Polyacrylamide(PAM),Polymer-4-vinlpyridine(P4VP),Polyaspartic acid(PASP),Polyvinyl alcohol(PVA),Polyethyleneimine(PEI),Anionic polyacrylamide(APAM),Sodium alginate,Sodium polyacrylate(PAAS),Sodium hyaluronate,Carbomer,Polyvinylpyrrolidone(PVP)and Chitosan)are applied to the soil as a phytoremediation modifier,most of which have not been used in the experiments in the field of phytoremediation enhancement.The effect of these 12 polymer compounds were investigated in the experiment,and the experiment was intended to find some polymer compounds with better effects on phytoremediation as modifier.The main research content and research results are as follows:(1)By harvesting the Sedum alfredii and dividing the sample to above-ground part and underground part.Then could know their biomass.the dry weight of the above-ground part is ordered:sodium alginate>polyacrylamide>carbomer>PAAS>blank>PVA>PVP>sodium hyaluronate>P4VP>PASP>APAM>PEI>chitosan.It can be found by comparison that the effects of Sodium alginate promote the most above-ground part’s dry weight,the above-ground dry weight of this sodium alginate experiment group is 7.8g,which is 80%higher that that of the blank group.Among them,the dry weight of the lower underground is arranged as carbomer>PAAS>sodium alginate>PAM>PEI>PASP>APAM>sodium hyaluronate>blank group>PVP>PVA>P4VP>chitosan.The best promote effect of underground dry weight is the Carbomer group,the dry weight has reached 0.5g,is an increase of 181%compared with the blank group.And the highest total dry weight is the Sodium alginate group.(2)By comparing the research on the concentration of Arsenic in Sedum alfredii,it can be concluded that for arsenic,the experimental group with the highest aboveground concentration is P4VP group,which is 53.6 mg/kg,while the underground concentration of the polyaspartic acid groups is the highest,which is 320.3 mg/kg,besides,its’coefficient is also the highest,being 0.35.However,the enrichment coefficient of all experimental groups is lower than 1.In terms of total enrichment,by calculating the content of the corresponding part and the dry weight,the enrichment of Arsenic enriched by Sedum alfredii can be obtained.the Sodium alginate group is the best group with the highest enrichment,which is 0.31 mg.And the transport coefficients of all the experimental groups are lower than the blank group,indicating that all have shown an inhibitory effect on the transport process.The enrichment of arsenic in all experimental groups are:sodium alginate>PAM>PASP>blank>carbomer>PAAS>P4VP>APAM>PVA>VP>chitosan>PEI.(3)By comparing the Cadmium concentration in the plant,the experimental group with the highest aboveground concentration is the PAM group,which is 1622 mg/kg,and the group with the highest underground concentration is the PASP group.In terms of enrichment coefficient,the most obvious promotion effect is the PAM and Sodium alginate groups,the enrichment coefficients reach 178 and 175,respectively,which have a strong ability to accumulate Cadmium.By calculating the content of the corresponding part and the dry weight,the enrichment of Cadmium enriched by Sedum alfredii can be obtained.The Sodium alginate group is the best group with the highest enrichment,From the perspective of enrichment,sodium alginate group’s total Cadmium enrichment reached 12.4 mg.And the group with the highest transport coefficient is aPAM group,with a transport coefficient of 15.0.The concentration of cadmium in all experimental groups is arranged in:sodium alginate>PAM>PAAS>carbomer>blank>PVP>sodium hyaluronate>P4VP>PVA>PASP>APAM>chitosan>PEI(4)By comparing the Lead concentration in plants,shown that the concentration of underground Lead in plant is much higher than above ground concentration.The experimental group with the highest underground concentration is the Sodium alginate group,reaching 3642.7 mg/kg.Most of the experimental groups are enriched in Lead,the enrichment coefficients are higher than 1,and the best enrichment coefficient is from PAM group,which is 2.65.By calculating the content of the corresponding part and the dry weight,the enrichment of Lead enriched by Sedum alfredii can be obtained.The Sodium alginate group is the best group with the highest enrichment,reaching 2.21 mg,but 1.05 mg of Lead was concentrated underground,while the concentration of the PAM group was mostly in aboveground.And the experimental group with the highest transport coefficient is the PVA group,which is 0.37.The enrichment of lead in all experimental groups is arranged in descending order:sodium alginate>PAAS>carbomer>PASP>PAM>blank>APAM>PVP>Sodium hyaluronate>P4VP>PVA>PEI>chitosan.As for the remediation effect on Soil contaminated with Lead,Cadmium,and Arsenic.The PASP group has a significant increase in the enrichment coefficient,but due to the lower dry weight,the enrichment is low,and remediation effect is poor.However,Sodium alginate does not significantly improve the enrichment coefficient,but the growth state is good,so that the Sodium alginate group has a good promotion effect on the remediation of Lead,Cadmium,and Arsenic pollution with practical potential.The PAM also has a promoting effect on the growth state,which increases the ability of Sedum alfredii to repair the Lead,Cadmium and Arsenic polluter soil.However,the effects of other modifier are not obvious or have inhibitory effects on phytoremediation. |
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