| Abandoned mining lands are those abandoned land including the open mining field and waste dump and tailing pond which was formed in the process of mineral resources exploitation and processing and utilization, their soil is serious polluted and Low fertility and poor matrix structure and very little vegetation, they pollute the local water, air and soil, and vegetation restoration is difficult on them, they will lead to the function of ecosystem degradation and have a serious threat to the regional ecological environment. Consequently, it is of great significance to research heavy metal pollution and ecological restoration on the local abandoned mining lands.This study base on the representative abandoned mining land which were the waste dump of Gulian river open coal mine and the tailing pond of Rouge ditch gold mine in Da Xing’ anling, and it was with the analysis of soil heavy metal pollution and ecological restoration as the goal on abandoned mining land, and it studied the matrix and Mn、Pb、Cu、Zn and fertility index and natural recovery and artificial restoration on abandoned mining lands. This study analyzed and studied soil nutrients, soil chemical speciation of heavy metals, matrix improvement and its effect, natural recovery of vegetation and artificial restoration of vegetation by the method of data analysis, field investigation and sampling, laboratory tests and analysis, matrix modification and vegetation restoration, at the same time,it analyzed the correlation between related contents.The main research results are as follows:(1) In waste dump, the content of Mn and Zn in soil of natural state was higher than the corresponding content of control land, however, the content of Pb and Cu was lower than the corresponding content of control land. Mn and Pb was priority to Reducible speciation, Zn and Cu was priority to Residue speciation. This showed that Mn, Pb and Zn had higher potential biological activity, so they had potential pollution characteristics; however, Cu had lower biological activity, so it was stable and little pollution. The correlation between all speciation and total content are very significant in Mn and Pb, The correlation between Residue speciation and total content are significant in Cu, The correlation between all speciation and total content are significant except Residue speciation in Zn.(2) In tailing pond, the content of Mn, Pb and Zn in soil of natural state was higher than the corresponding content of control land, however, the content of Zn was lower than the corresponding content of control land. Mn and Pb was priority to Reducible speciation, Zn and Cu was priority to Residue speciation. This showed that Mn and Pb had higher potential biological activity, so they had potential pollution characteristics; however, Cu and Zn had lower biological activity, so it was stable and little pollution. The correlation between all speciation and total content are very significant in Mn, The correlation between all speciation and total content are significant except Reducible speciation in Pb and Cu, The correlation between Oxidizable speciation, Residue speciation and total content are significant in Zn.(3) In two kinds of abandoned mining land, the average content of Pb in soil of natural state were beyond the common value in soil, Cu and Zn as well, their single pollution index and comprehensive pollution index had reached the alert level. However, in all content of Mn, only the maximum was beyond the common value in soil, it’s all single pollution index were in the security level; From the point of maximum of four kinds of heavy metal content, pollution levels would not reach or exceed moderate pollution level in waste dump and tailing pond. The degree of variation of four kinds of heavy metal belong to medium.(4) The dominant herbaceous plants of natural recovery on waste dump have Leymus secalinus (Georgi) Tzvel., Rubus saxatilis L., Poa sphondylodes Trin. Ex Bunge, Polygonum alpinum All. and Rumex maritimus L.; The dominant woody plants have Betula platyphylla Suk., Pinus sylvestris L. var. mongolica Litv. and Larix gmelini (Rupr.) Rupr.. Compared with bare soil fertility index, root surrounding soil fertility of Poa sphondylodes Trin. Ex Bunge, Leymus secalinus (Georgi) Tzvel. Rumex maritimus L. and Larix gmelini (Rupr.) Rupr. was improved larger; In all fertility index, available p, total K and available K were changed minimum, even they showed downward trend; But all fertility index of root surrounding soil was lower than that of natural forest. Among all dominant plants, Leymus secalinus (Georgi) Tzvel., Rumex maritimus L., Rubus saxatilis L., Larix gmelini (Rupr.) Rupr., Betula platyphylla Suk. and Pinus sylvestris L. var. mongolica Litv. have better removal effect to heavy metal of waste dump.(5) The dominant herbaceous plants of natural recovery on tailing pond of gold mine have Carex rhynchophysa C. A. Mey., Chenopodium album L., Saussurea japonica (Thunb.) DC, Epilobium angustifolium (L.) Korch. and Sorbaria sorbifolia (L.) A. Br.; The dominant woody plants have Salix hsinganica Chang et Sky., Larix gmelini (Rupr.) Rupr. and Pinus sylvestris L. var. mongolica Litv.. Among all dominant plants, Compared with bare soil fertility index, root surrounding soil fertility of Carex rhynchophysa C. A. Mey., Chenopodium album L. Larix gmelini (Rupr.) Rupr. and Salix hsinganica Chang et Sky.Rupr. was improved larger; In all fertility index, available p, total K and available K were also changed minimum, even they showed downward trend; And all fertility index of root surrounding soil was also lower than that of natural forest. Among all dominant plants, Carex rhynchophysa C. A. Mey., Chenopodium album L., Sorbaria sorbifolia (L.) A. Br, Larix gmelini (Rupr.) Rupr. and Pinus sylvestris L. var. mongolica Litv. have better removal effect to heavy metal of waste dump.(6) By replace soil with out-soil and soil preparation measures, etc, Selected plant according to the principle of "matching site with trees", and reference to the study results of natural recovery, Selected the plants of appropriate artificial recovery and experimented successfully on waste dump of Gulian river open coal mine, they are local Pinus sylvestris L. var. mongolica Litv., Larix gmelini (Rupr.) Rupr. and Betulaplatyphylla Suk., As well as introduced Hippophae rhamnoides Linn., Syringa oblata Lindl., their survival rate is above80%; The plants of appropriate artificial recovery on tailing pond of Rouge ditch gold mine have Pinus sylvestris L. var. mongolica Litv. wiht soil block, Larix gmelini (Rupr.) Rupr. and Salix hsinganica Chang et Sky., At the same time introduced Hippophae rhamnoides Linn., Syringa oblata Lindl. and Medicago sativa L., their survival rate is above85%. Finally, put forward five kinds of ecological restoration mode which are Suitable for local abandoned mining lands, and their effect which improved the soil fertility of abandoned mining lands was significantly higher than that of natural restoration, and their effect which removed heavy metals and held water and soil was significantly better than that of natural restoration.(7) If using Lycium chinense Mill., Parthenocissus tricuspidata (Sieb. Ee Zucc.) Planch, and Tamarix chinensis Lour, to restore the vegetation of abandoned mining land in Mohe county, the survival rate of plant could not be ensured, and it didn’t succeed to plant Medicago sativa L. on waste dump of open coal mine.(8) On waste dump of coal mine, it would ensure the survival rate of plants by delt with side slope and covered humus soil on the last dumping step and the final dumping flat and slope; On tailing pond of gold mine, created a matrix stable layer by Mixed with sand to matrix, the effect was very significant because it greatly improved the capacity of matrix holding water and protecting fertilizer. Mixed sand volume is about one third, and finally, it is the most appropriate that there are not big pores in matrix; and artificial restoration effect is more significant by replace soil with out-soil which mixed with waste homestead soil and living garbage according to1:1proportion, at the same time, plant roots were dealt with rooting powder and super absorbent polymers, or chose those plants with soil block or nutrition cup, the restoration effect is also very significant. |
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