Analysis of heavy metal contamination in the soil and enrichment capabilities of terrestrial plants around a typical vanadium smelter area

Phytoremediation is an important means of soil heavy metal pollution remediation. In order to figure out the soil pollution status of the water source in the middle line of the South-to-North Water Transfer Project and repair it, soil samples (n = 14) and local dominant terrestrial plants (n = 113) were collected in typical areas around Chaobei River and the typical vanadium smelter in Hubei Province in four seasons. Microwave digestion–inductively coupled plasma mass spectrometry (ICP‒MS) was applied to analyze the concentrations of vanadium (V), chromium (Cr), arsenic (As), and cadmium (Cd) in soils and plants. Soil pollution levels were evaluated on the basis of the Nemerow index method. The enrichment capabilities of plants for the four heavy metals were also analyzed. Results show that the heavy metal content of soil around the junction of the sewage outfall and the river is the highest among the seven sampling sites around Chaobei River. The concentration of V in the raw ore stacking area exceeds the limit by approximately 83 times and the concentrations of Cr, As, and Cd exceed the limit by approximately 2 times, which make the soil in the raw ore stacking area heavily contaminated. The soils in the six other sampling sites in the smelter are polluted in different degrees. The results of the evaluation of the enrichment and tolerance capabilities indicate that Gnaphalium affine, Erigeron multifolius, and Erigeron annuus have the highest tolerance capability for the four heavy metals. Conyza canadensis, Imperata cylindrica, Solanum photeinocarpum, Dendranthema indicum, Trifolium repens, and Echinochloa crusgalli are the hyperaccumulators for V, Cr, and Cd. The enrichment capabilities of Pteris vittata and Broussonetia papyrifera for As are extremely high. Moreover, Artemisia lavandulaefolia has a high enrichment capability for Cr and Cd, Ludwigia prostrata and Picris japonica have prominent tolerance and enrichment specificities for Cr and V, and Potentilla chinensis and Phytolacca americana have obvious enrichment capabilities for Cd specifically. The pot experiments of five local dominant terrestrial plants illustrate that, under the composite heavy metal contaminant conditions, Boehmeria nivea has the highest tolerance capability and Potentilla chinensis has the highest enrichment capability.