| The discharge and stockpiling of coal gangue have great influence and harm to the soil environment,plant growth and human health,among which the soil heavy metal pollution is the most harmful.Phytoremediation is the most promising technology in the field of soil heavy metal pollution control,among which herbage plants with rapid growth and easy planting have become the hot research object of soil heavy metal pollution phytoremediation in mining areas.In this study,alfalfa and ryegrass were selected as the materials,and unpolluted undisturbed soil from typical gangue accumulation area of Fengfeng mining area was used as the test soil.The effects of different heavy metal pollution types and loads on the growth characteristics of ryegrass and alfalfa were studied by soil culture pot method,and the changes of heavy metal enrichment and transport capacity of ryegrass and alfalfa under different heavy metal pollution types and loads were studied.The main conclusions are as follows.(1)The effects of single Pb,Cd,Cu and Hg pollution on alfalfa and ryegrass were obviously different in germination and growth stages.To be specific ① The germination potential,germination rate,germination index and vigor index of alfalfa and ryegrass decreased by 8.7%～65.8%,8.6%～53.7%,4.3%～51.7%,1.9%～69.7%under single heavy metal pollution load,respectively.The results showed that heavy metal pollution in soil inhibited the germination ability and speed of alfalfa and ryegrass,as well as the strength,regularity and health of seedlings.② Under single Pb,Cd and Cu pollution load,the germination potential of alfalfa decreased by 18.4%-62.3%(P<0.05);8.7%-47.3%and 24.5%-65.8%(P<0.05),respectively,indicating that Pb,Cd and Cu all had the strongest inhibition effect on the strength and regularity of alfalfa seedlings.③ Alfalfa vigor index decreased by 28.2%-64.8%(P<0.05)under single Hg pollution load,indicating that Hg had the strongest inhibitory effect on alfalfa seedling health.④Under single Pb,Cd,Cu and Hg pollution load,ryegrass vitality index decreased by 25.3%-38.0%,9.5%-23.8%,7.7%-25.3%and 31.1%-54.8%,respectively,with significant differences(P<0.05).The results showed that Pb,Cd,Cu and Hg all had the strongest inhibitory effect on the health degree of ryegrass seedlings.⑤ single heavy metal pollution load of alfalfa and plant height,fresh weight of perennial ryegrass and biomass were reduced by 5.3%～44.5%,1.6%～84.5%.2.9%～89.2%,3.5%～42.9%,1.3%～90.1%,3.4%～63.4%,The results showed that heavy metals in soil could inhibit the growth,biomass accumulation and plant height growth of alfalfa and ryegrass.⑥ The root biomass of alfalfa decreased by 4.6%-61.5%under single Pb pollution load,indicating that Pb had the strongest inhibition effect on the root biomass accumulation of alfalfa.⑦ The fresh weight of alfalfa root decreased by 46.2%-66.9%,33.6%-67.4%and 74.5%-84.5%under single Cd,Cu and Hg pollution load,respectively,with significant differences(P<0.05),indicating that Cd,Cu and Hg had the strongest inhibition effect on the growth of alfalfa root.⑧Fresh weight of ryegrass root decreased by 53.8%～82.9%,74.7%～86.7%,62.2%～88.0%,81.9%～90.1%under single Pb,Cd,Cu,Hg pollution load,respectively,with significant differences(P<0.05).The results showed that Pb,Cd,Cu and Hg all had the strongest inhibition on the root growth of ryegrass.(2)The effects of soil Pb-Cu-Cd combined pollution on alfalfa and ryegrass were obviously different in germination and growth stages.To be specific ① The germination potential,germination rate,germination index and vigor index of alfalfa and rrye decreased by 25.2%-43.8%(P<0.05),25.0%-40.6%(P<0.05),33.2%-44.2%(P<0.05),43.5%-61.0%(P<0.05),respectively,under pB-Cu-Cd combined pollution load.0%(P<0.05),0.1%～19.2%,1.1%～16.9%,0.2%～14.9%and 11.9%～37.4%(P<0.05),The results showed that the combined pollution load of soil Pb-Cu-Cd had inhibition effect on the germination ability,germination speed,seedling strength and regularity and health degree of alfalfa and ryegrass,and the combined pollution of soil Pb-Cu-Cd had the strongest inhibition effect on the seedling health degree of alfalfa and ryegrass.②Plant height,fresh weight and biomass of alfalfa and rye grass decreased by 11.2%-30.8%(P<0.05),34.5%-85.5%(P<0.05)and 0.7%-81.5%,respectively,under Pb-Cu-Cd combined pollution load.13.9%-37.6%(P<0.05),10.0%-89.9%(P<0.05),20.7%-73.6%(P<0.05)showed that the combined pollution load of Pb-Cu-Cd had inhibitory effects on the growth,biomass accumulation and plant height growth of alfalfa and rye grass.③ The root fresh weight of alfalfa and rye grass decreased by 56.9%-85.5%and 70.7%-89.9%,respectively,under the heavy metal Pb-Cu-Cd combined pollution load,and the differences were significant(P<0.05),indicating that the combined pollution of Pb-Cu-Cd had the strongest inhibition effect on the root growth of alfalfa and rye grass.(3)The effects of Pb-Cu-Cd-Hg combined pollution on alfalfa and ryegrass in germination and growth stages were obviously different.To be specific.① The germination potential,germination rate,germination index and vigor index of alfalfa and rye grass were decreased by 29.8%～64.9%(P<0.05),30.1%～61.0%(P<0.05),28.0%～59.4%(P<0.05),43.1%～75.6%(P<0.05),3.9%～34.6%,6.7%-21.3%(P<0.05),6.8%～24.7%(P<0.05),39.4%～53.5%(P<0.05),The results showed that the combined pollution load of soil Pb-Cu-Cd-Hg had inhibition effect on the germination ability,germination speed,seedling strength,regularity and health degree of alfalfa and rye-grass,and the combined pollution of soil Pb-Cu-Cd-Hg had the strongest inhibition effect on the seedling health degree of alfalfa and rye-grass.② Plant height,fresh weight and biomass of alfalfa and rye decreased by 17.9%～36.9%(P<0.05),2.1%～83.1%and 0.9%～93.8%under Pb-Cu-Cd-Hg combined pollution load,respectively.The results showed that the combined pollution load of Pb-Cu-Cd-Hg could inhibit the growth,biomass accumulation and plant height growth of alfalfa and rrye grass.③The root biomass of alfalfa decreased by 26.2%-93.8%(P<0.05)under the combined pollution load of Pb-Cu-Cd-Hg,indicating that the combined pollution of Pb-Cu-Cd-Hg had the strongest inhibition effect on the root biomass accumulation of alfalfa.④Leaf biomass of ryegrass decreased by 44.0%～81.0%(P<0.05)under heavy metal Pb-Cu-Cd-Hg combined pollution load,indicating that soil Pb-Cu-Cd-Hg combined pollution had the strongest inhibition effect on leaf biomass accumulation of ryegrass.(4)The enrichment and transport of heavy metal elements in alfalfa and ryegrass showed different characteristics under different soil heavy metal pollution types.To be specific,①Under the single heavy metal pollution type,the enrichment coefficient and transport coefficient of Cd for alfalfa and ryegrass were 1.47-8.68,1.34-4.38,1.83-3.65,0.90-2.26,respectively.The maximum enrichment of Cd in roots,stems and leaves was 6.27,5.11,3.18,7.83,6.30,4.88mg/kg,indicating that alfalfa and ryegrass had the highest Cd enrichment and transport capacity.②Under the single heavy metal pollution type,the enrichment ability of Pb and Cu to alfalfa and ryegrass was root>stem>leaf,the enrichment ability of Cd to alfalfa was stem>root>leaf,and the enrichment ability of Cd to ryegrass was root>leaf>stem.③ Under Pb-Cu-Cd combined pollution type,the enrichment and transport coefficients of Cd in alfalfa were 1.01-2.37 and 0.77-5.98,respectively.The maximum enrichment of Cd in roots,stems and leaves were 7.96,4.25 and 2.45mg/kg,respectively.Alfalfa had the highest enrichment and transport capacity of Cd.④Under Pb-Cu-Cd combined pollution type,the enrichment coefficient of Cd in ryegrass ranged from 0.63 to 2.06,and the maximum enrichment of Cd in roots,stems and leaves were 5.57,3.46 and 1.33mg/kg,respectively.Ryegrass had the highest enrichment ability of Cd.⑤Under Pb-Cu-Cd combined pollution type,the transport coefficients of Ryegrass to Pb ranged from 0.38 to 2.09,and the maximum enrichment of Pb in roots,stems and leaves were 91.62,33.49 and 15.19mg/kg,respectively.Ryegrass had the strongest transport capacity of Pb.⑥Under Pb-Cu-Cd-Hg combined pollution type,the Cu enrichment coefficient and transport coefficient of alfalfa were 1.02-3.56 and 0.78-2.37,respectively.The maximum Cu enrichment in roots,stems and leaves were 124.41,39.99 and 46.7mg/kg,respectively.Alfalfa had the highest Cu enrichment and transport capacity.⑦Under Pb-Cu-Cd-Hg combined pollution type,the enrichment coefficient and transport coefficient of Ryegrass for Cd were 0.54～2.78 and 0.56～1.60,respectively.The maximum enrichment of Cd in roots,stems and leaves were 5.34,1.83 and 2.07mg/kg,respectively.Ryegrass had the highest enrichment and transport capacity of Cd. |
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