Study On The Growth Of Three Woody Plants In Manganese Mine Waste Polluted Soil And Their Absorption Of Heavy Metal Manganese Characteristics

With the development of industry and agriculture and human activities,soil heavy metal pollution is becoming more and more serious,which has become a global environmental problem.China is a country rich in mineral resources.In the process of mining mineral resources,due to the lag of environmental technology,a large number of mining wastelands have been formed,and a series of environmental and ecological problems have been caused.Hunan Province,as the hometown of non-ferrous metals,its rich mineral resources in the process of mining and utilization also brought a series of ecological and environmental hazards.In recent years,the "cadmium rice" incident,which has been widely concerned,makes the pollution problem caused by the abandoned land of heavy metal mining area cause great concern of the whole society.Phytoremediation technology,which has the advantages of low cost and environmental friendliness,is attracting more and more attention.Phytoremediation of heavy metal contaminated soil has attracted worldwide attention.In this study,soils collected from Xiangtan Manganese mine wasteland was taken as the research object to carry out the improvement experiment of the mixing ratio of manganese sludge and manganese tailings in situ.By means of pot experiment with Pinus massoniana,Koelreuteria paniculata and Schima superba seedlings,combined with the biomass and survival rate of potted seedlings under different mixing ratios of manganese sludge and manganese tailings,the distribution quantity of manganese in plants was analyzed.To explore the distribution and translocation mechanism of manganese in potted plant seedlings under the mixed effect of manganese sludge and manganese tailings.This study can provide a theoretical basis and basis for the promotion and demonstration of the optimization model of phytoremediation technology of manganese mine wasteland in the future.The main results are as follows:(a)The soil physiochemical properties of mixed soil substrates varied with ratios of mixing of manganese sludge and manganese tailings.The results showed that the mechanical composition,bulk density,organic matter,pH,total nitrogen,total phosphorus,total manganese,available phosphorus,available manganese and other physical and chemical properties of the mixed matrix are changed after mixing manganese sludge and manganese tailings in different proportions.In general,the soil texture of the mixed substrates tends to loam,the bulk density tends to decrease.The pH value of the control soil in the potted medium was the lowest,which was 5.0;The pH value of the mixed matrix is between 5.8 for manganese tailing mud and 8 for manganese tailing slag.The average content of total phosphorus in potted soil was 1297.72 mg/kg,and the maximum value appeared in the manganese tailing soil matrix.The total phosphorus content in the control soil matrix was the lowest,and the content in the manganese tailing soil matrix was the second lowest.The content of total manganese in the control soil is the lowest,the content of manganese tailing mud is lower than the average,the content of total manganese in the manganese tailing slag is the highest,and the content of total manganese in the mixed matrix of the two is between the two.The average content of available manganese was 287.53 mg/kg,and the content of available manganese in control soil was the lowest(29.3 mg/kg);The available manganese in manganese tailing mud and slag is also lower than the average;However,the content of available manganese in the mixed matrix was higher than the average value,and the content of available manganese in the matrix was the highest when.the ratio of manganese tailing and manganese tailing mud was 1:3.(b)The survival rate of K.paniculata and S.superba seedlings could be improved by mixing manganese sludge and manganese tailings.The survival rates of K.paniculata and S.superba seedlings were significantly increased by the mixture of manganese sludge and manganese tailings.The survival rate of K.paniculata and S.superba seedlings could be improved by the mixture of these two manganese wasteland.The optimum mass ratio of manganese sludge and manganese tailings is 2:2.Similarly,both K.paniculata and S.superba can be used as suitable tree species for phytoremediation of manganese mine wasteland,and P.massoniana is not suitable for phytoremediation of manganese mine wasteland because of its low survival rate.Specifically,the survival rate of K.paniculata seedlings was 75%in the control soil matrix,75%in the mixed matrix,and more than 75%in the 1:3 mixed matrix of manganese tailings and manganese sludge.The average survival rate of P.massoniana seedlings was 29%.Except for 100%survival rate in the control soil matrix,they could not survive in other matrices.The survival rate of S.superba seedlings was 100%in the control soil matrix.The survival rate of S.superba seedlings was only about 25%in the manganese sludge,manganese tailing and manganese sludge mixed with ratio of 3:1,and ca 50%in the manganese tailing matrix.On the contrast,its survival rate was higher than the average level,about 75%potted in the mixed matrix of manganese tailing and sludge with ratio of 1:3 and 2:2.(c)The mixture of manganese sludge and manganese tailings affected the biomass and its distribution in phytoremediation plants.The results showed that the mixed matrix of manganese tailings had certain effects on the growth and biomass of K.paniculata and S.superba seedlings.The survival rate and growth of seedlings were basically consistent with the development of fine roots,and the change of biomass was closely related to the survival rate.From the perspective of root(fine root)biomass,the quantitative evidence was found that manganese mine sludge was not suitable for seedling growth;the mixed substrates of T1S3 and T2S2 had a great promoting effect on fine root growth.The biomass and its distribution characteristics of K.paniculata and S.superba seedlings under manganese sludge,manganese tailings and their mixed substrates not only reflect their different biological characteristics,but also reflect their adverse conditions,such as heavy metal toxicity to manganese contaminated substrates,high bulk density caused by clay soil,imbalance of nitrogen and phosphorus ratio,unsuitable soil pH value,etc.The response to stress level was also different.(d)The bioconcentration factor(BCF)and translocation factor(TF)of remediation plants were changed after mixing manganese sludge and manganese tailings.The differences of BCF,TF and TFf(translocation factor for foliage)provide quantitative evidence for the differences of manganese tolerance mechanism between K.paniculata and S.superba.The BCF and TF showed that K.paniculata and S.superba were not hyperaccumulators,but tolerant plants of heavy metal manganese.Although they have some differences in manganese tolerance mechanism,they are adapted to be potential phytoremediation plants in manganese mine wastelands.This study provides a feasible way for the phytoremediation of manganese mine wastelands,that is,mixing the local mine sludge and mine tailings to enhance the phytoremediation effect.