Screening Of Enriched Plants For Phytoremediation Of Typical Chromium Contaminated Sites

The chromium-contaminated site not only damages its surrounding environment,but also poses a hazard to the ecological environment and human health.Finding a safe,ecologically viable and reliable remediation method to remedy chromium contaminated sites has become a hot topic in current social research.Phytoremediation is an ecological,feasible and green method for the remedy of heavy metals,in which the screening of enriched plants is the key.Therefore,in this paper,based on the actual situation of a typical chromium-contaminated site,the seed germination experiment and hydroponic experiment were used to quickly screen nine plants,and the pot experiment of chromium-contaminated soil was further simulated to compare and analyze the growth and enrichment ability of plants and impact on soil biological properties in chromium-contaminated soil,and high-efficiency chromium-enriched plants were screened.On this basis,the in situ restoration of chromium contaminated site experiments was carried out to verify the actual remedy effect of the selected plants.This study aims to provide technical support for phytoremediation of chromium-contaminated sites.The main results are as follows:(1)Seed germination experiment showed that heavy metal chromium inhibits the germination and seedling growth of nine plants,and this inhibition effect increases with the increase of heavy metal chromium concentration.Under the same chrome concentration,the seed germination and seedling growth of four gramineous plants,Pennisetum,Setaria,Lolium and Festuca,were higher than those of Trrifolium,Cyperus,Amaranthus,Brassica and Taraxacum.This indicates that these four gramineous plants are more tolerant to chromium.In addition,Amaranthus,Pennisetum,Setaria,Lolium and Festuca have higher accumulation of chromium.(2)The hydroponic experiment showed that heavy metal chromium inhibited the growth and development of plants.Trrifolium,Cyperus and Brassica were all killed after one month of culture.And the growth and development of the other six plants were different degrees of inhibition,and the higher the concentration of chromium,the more obvious the inhibition of plants.(3)Pennisetum,Setaria and Amaranth have strong tolerance and enrichment ability to chromium,and have high potential for chromium remediation.The chromium content of these three plants increased with the increase of chromium concentration,among which Pennisetum,Setaria and Amaranth had stronger absorption capacity for chromium.In addition,Pennisetum,Setaria and Amaranth have higher enrichment coefficient and transport coefficient,the enrichment coefficient is above0.65,and the transport coefficient is basically around 0.70.(3)Pot experiments showed that chromium pollution inhibited the growth of plants.The dry weight,plant height and root length of Pennisetum were larger than that of Setaria and Amaranth,and the decrease rate with the increase of chromium concentration was smaller than that of the other two plants.The absorption,enrichment and transport ability of Pennisetum was higher than that of Setaria and Amaranth.When the concentration of chromium was 400mg/kg,the accumulation of chromium in the upper part and root of the Pennisetum reached the maximum,252.44mg/kg and406.19mg/kg,respectively.The enrichment coefficient of the upper part of the Pennisetum was above 0.63,the enrichment coefficient of root was above 1.00,and the transport coefficient was above 0.60.Pennisetum has a good resistance mechanism to the stress of chromium pollution in soil.The stimulation of chromium enhances the defense response of Pennisetum,increases the activity of SOD and CAT of protective enzymes,and the plant photosynthesis of Pennisetum was the least inhibited under the condition of chromium pollution.In chromium-contaminated soil,heavy metal chromium reduced the activities of invertase,catalase,phosphatase and urease in soil,and planting plants could reduce the inhibitory effect of heavy metal chromium on soil enzyme activity.Compared with Amaranth and Setaria,Pennisetum can significantlyincrease soil enzyme activity.Planting plants can significantly increase the diversity of microbial community distribution,change the distribution and abundance of soil microbial communities,and inhibit or enhance the expression of related genes,thereby promoting the remedy effect of plants.Pennisetum shows strong self-regulation and resistance,as well as the potential for remediation of chromium-contaminated soil.(4)The in situ phytoremediation experiment of typical chromium contaminated sites showed that the Pennisetum can grow to about 1.80 m and tiller in two contaminated sites with different concentrations.Pennisetum has a higher absorption capacity for chromium,in the A and B plots,the highest chromium content in the upper part of plants reached 82.52 and 303.76 mg/kg,respectively.The enrichment coefficient of the roots of Pennisetum was more than 1.00,the enrichment coefficient of the upper part of the Pennisetum was about 0.90,and the transport coefficient was above 0.85.In addition,Pennisetum effectively reduced the chromium content in the soil,which is between 60.69%-79.72%.The above results indicate that Pennisetum has a good remedy effect in remediation of chromium-contaminated sites.In summary,under the condition of chromium pollution,Pennisetum has high chromium tolerance and chromium enrichment ability,and has a good application prospect in phytoremediation of chromium contaminated sites,which can well remedy chromium contaminated sites and improve soil ecological environment.