Abstract
Air and soil pollution from mining activities has been considered as a critical issue to the health of living organisms. However, few efforts have been made in distinguishing the main pathway of organism genetic damage by heavy metals related to mining activities. Therefore, we investigated the genetic damage of Leymus chinensis leaf cells, the air particulate matter (PM) contents, and concentrations of the main heavy metals (Pb, Cd, Cr, Hg) in soil and foliar dust samples collected from seven experiment points at the core mining area and one control point 20 kilometers away from the core mining area in Inner Mongolia in 2013. Comet assay was used to test the genetic damage of the Leymus chinensis leaf cells; the Tail DNA% and Tail Moment were used to characterize the genetic damage degree of the plant cells. The comet assay results showed that the cell genetic damage ratio was up to 77.0% in experiment points but was only 35.0% in control point. The control point also had the slight Tail DNA% and Tail Moment values than other experiment groups. The cell damage degree of the control group was 0.935 and experiment groups were 1.299–1.815. The geo-accumulation index and comperehensive pollution index(CPI) were used to characterize heavy metal pollution in foliar dust samples, and single factor pollution index and CPI were used to characterize the heavy metal pollution in soil samples. The CPIfoliar dust of control group was 0.36 and experiment groups were 1.45–2.57; the CPIsoil of control group was 0.04 and experiment groups were 0.07–0.12. The results of correlation analyze showed that Air Quality Index (AQI) -CPIfoliar dust(r = 0.955**)>Damage degree-CPIfoliar dust(r = 0.923**)>Damage degree-AQI(r = 0.908**)>Damage degree-CPIsoil (r = 0.824*). The present research proved that mining activity had a high level of positive correlation with organism genetic damage caused by heavy metals through comparing with the control point; soil and atmosphere were both the important action pathway for heavy metal induced genetic damage in mining area. Furthermore, heavy metal contents in foliar dust showed a higher positive correlation with genetic damage than when compared with soil. This means the heavy metal contents that L.chinensis absorbed through respiration from the atmosphere could make more serious genetic damage than when absorbed by root systems from soil in the mining area. This study can provide theoretical support for research on plant genetic damage mechanisms and exposure pathways induced by environmental pollution.
Highlights
With the spread of heavy “smog and haze”, the problem of environmental health impact is regaining worldwide concern
Comparing the positive correlations between the pairs of Damage degree-CPIfoliar dust (r = 0.923) and Damage degree-CPIsoil (r = 0.824), it can be said that heavy metals contained in the foliar dust have a higher level correlationship with leaf cells damage degree compared with heavy metals contained in soil. This may be because the heavy metal particles in the fly dust in mining areas accumulated in high concentration in a short time on the blade surface, and with the enrichment, lots of nanoscale particles could be absorbed by the leaf through micrometer size leaf stomatas during respiration, leading to enriched mesophyll tissue and induced genetic damage
Our results firstly focus on whether the atmosphere or the soil is the main pathway of plants genetic damage in mining areas
Summary
With the spread of heavy “smog and haze”, the problem of environmental health impact is regaining worldwide concern. The domestic and foreign research about heavy metal pollutions are mainly related to the health risk assessment of some small mammals, hydrobiose and plants. Mining activities and mineral processing can generate large volumes of metal-rich waste materials and be considered as the principal cause of heavy metal soil contamination[10,11]. The results suggested that heavy metal stress influenced antioxidant status and induced DNA damages in U. dioica that may help to understand the effects of metals genotoxicity. With the atmospheric pollution issues getting more and more serious, the health risk of the organisms surrounding mining areas induced by these airborne heavy metal particles can not be ignored anymore. The majority of studies carried out so far about heavy metal pollution on plants have been concerned with root uptake rather than foliar uptake[14,15]. Studying the main pathway for plants genetic damaged in the mining area has very important significance for protecting the plants, animals, and human health living around the mining area
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