| Although the road is one of the important powers of economic progress, development of road also caninduce a lot of environmental problems. In the past few decades, these environmental problems are alwayshot topic. In the study, on the basis of ‘source-path-acceptor-effect’ of heavy metals, environmental effectsand migration rule of traffic-source heavy metals were investigated, using theories and methods of SystemScience.310thNational Highway and337thProvincial Highway were chosen as the research objects.Roadside soils, wheat, rice, ambient particulate matter, precipitation andsurface water were collected assamples, and their heavy metals (Pb, Cu, Ni, Cr, Cd and Zn) were detected by the inductively coupledplasma mass spectrometry (ICP-MS) respectively according to the recommended standard method. Spatialdistribution of heavy metals concentrations by applying Universal Kriging interpolation model,concentration, PollutionIndex&Risk Index of heavy metals in soils, wheat, rice, ambient particulate matter,precipitation&surface water were analysed. Meanwhile, roadside atmospheric particulate and the spatialconcentration distribution of roadside heavy metals was fitted using line source particle diffusion model.The main results were as follows:(1) Highway traffic has great effect on heavy metals in soil, plant, airand water in road-domainenvironment. Since the traffic-source heavy metals appear, they are adsorbed by and migrate with ambientparticulate matters, finally, they are imported into soils and water. As a result, traffic-source heavy metalshave been accumulated in road-domain environment, and caused environment polluted. The models ofmigration in air and spatial distribution in soils for traffic-source heavy metals were built, and verified bythe measured concentrations. The spatial distributions of ambient particulate matter&its heavy metalconcentrations were well fitted by the model, and the spatial distributions of soil heavy metalconcentrations were better fitted by.(2) The different tillage systems and characteristics of heavy metals have great effects on spatialdistribution of heavy metals in roadside soils.The distributions of metal concentrations in upland-uplandrotationfield were strips parallel to the highway stretching. The concentrations of Cr and Cu decreasedexponentially with the distance from the roadbed, however, the concentrations of Cd, Pb, Ni and Znrevealed an asymmetrical distribution with the distance, which increased firstly, reached their highest values between30and50m away from the roadbed, and then gradually decreased to the control values.Distribution types have significant relationship with sizes of ambient particulate matters whichtraffic-source heavy metals are adsorbed by. Being adsorbed by the larger ambient particulate matters,heavy metal concentrations reveal an exponential distribution. While they are adsorbed by the smaller ones,their concentrations reveal an asymmetrical distribution. In contrast, heavy metal concentrations showedirregular patch distribution in paddy-upland rotation field, resulted from waterlogged condition changingpH, Eh of soils, leading to horizontal migration of soil heavy metals.(3) Traffic-source heavy metals have posed pollution, certain potential ecological risk and health riskon road-domain soil environment. According to the second index in the national standards for soil quality,the assessment by pollution index indicates that it was in not polluted states on Xinghuaying&Xiangdiantransect. On Duliang transect, Ni was in light polluted states within100meter away from the roadbed onthe south side, and within500meter on the north side. Zn was in light polluted at the position of140&150meter away from the roadbed on the south side. The others were in not polluted states. Totally, heavymetals were in comprehensive not polluted state on the three transects. Making a reference to the controlvalues, the assessment by geoaccumlation index of heavy metal shows that six heavy metals were indifferent polluted states. On Xinghuaying transect, Cr was in middle polluted states within30meters, andin slight polluted states between35~120meters away from the roadbed on the south side. Cr was in middlepolluted states at the position of15meter, and in slight polluted states between35~120&20~120metersaway from the roadbed on the north side. Cu, Zn, Cd and Pb appear light polluted at some positions within80meters away from roadbed on both sides. On Duliang transect, Pb, Ni, Zn, Cr and Cu were in middlepolluted states in part regions, Cd was in light polluted in part regions. On Xiangdian transect, Cr, Ni, Zn,Cu and Cd were in middle polluted states in part regions, Pb was in light polluted in part regions. Making areference to the control values, the assessment by potential ecological risk index of heavy metals shows thatthere was comprehensive milddle potential ecological risk on all transects. Cd in middle potentialecological risk states was82.43%on Xinghuaying transect,45.07%on Duliang transect, and87.83%onXiangdian transect. Pb in middle risk state was8.45%on Duliang transect. While, all the others were inlight risk states. CR and TCR on all transects were lower than the standard suggested by US EPA whichmeant where may be carcinogenic riskpossibility, and Cr is the main factor of potential ecological risks. (4) The concentrations of heavy metals in grain crops within200m away from roadbed weredistinguishably higher than the control values. Pb in wheat samples were all in heavy polluted states. Thewheat sample number of Cr achieving slight polluted state, middle pollutedstate and heavy polluted staterespectively accounted for2.70%,16.22%and81.08%of the total sample number. The wheat samplenumber of Ni achieving slight polluted state, middle polluted state and heavy polluted state respectivelyaccounted for8.11%,40.54%and51.35%. While the wheat sample number of Cu, Cd&Pb achievingslight polluted state respectively accounted for89.19%,9.11%and45.95%. Cr in rice samples were all atheavy polluted state. The rice sample number of Ni achieving slight polluted state, middle pollutedstate andheavy polluted state respectively accounted for19.44%,16.67%and11.11%of the total sample number.Therice sample number of Pb achieving slight polluted state accounted for25.00%. While Cu, Cd&Znwere in not polluted state.The metals in wheat had comprehensive heavy polluted index, and the metals inrice partly had comprehensive midlle polluted index, partly had comprehensive heavy polluted index. Cr&Pb in wheat had non-carcinogen risk possibility, while Cu、Cd、Zn&Ni had not non-carcinogen riskpossibility. Heavy metals in wheat had comprehensive non-carcinogen risk possibility. Cr in wheat is thefirst main factor of non-carcinogen risk possibility, for the risk of Cr accounted for52.16%of the total risk.And Pb is the second main factor of non-carcinogen risk possibility, for the risk of Cr accounted for26.59%of the total risk. Cr in rice had non-carcinogen risk possibility, while Pb, Cu, Cd, Zn&Ni had notnon-carcinogen risk possibility. Heavy metals in rice had comprehensive non-carcinogen risk possibility. Crin rice is main factor of non-carcinogen risk possibility, for the risk of Cr accounted for82.90%of the totalrisk. Cr&Pb in wheat&rice had non-carcinogen risk possibility, while Cu, Cd, Zn&Ni had notnon-carcinogen risk possibility. Heavy metals in wheat&rice had comprehensive non-carcinogen riskpossibility.(5) Highway traffic had great effect on road-domain water environment. The concentrations of heavymetals in surface water200m away from roadbed were distinguishably higher that the control values, evenpart of surfacewaterhad been polluted. The surfacewater sample number of Cr achieving slight pollutedstate, middle pollutedstate and heavy polluted state respectively accounted for16.67%,8.33%and8.33%of the total sample number. And the number of Zn achieving slight polluted state accounted for4.17%.Highway traffic had great effect on roadside precipitation but it did not cause roadside precipitation polluted.(6) Ambient particulate matter in road-domain environmentwas mainly affected by wind direction androad towards. The migration distance of ambient particulate matter is negatively correlated with its size.The larger ambient particulate matter is the nearer its migrationis. The effects of atmospheric particulate onspatial distributions of heavy metals mainly occurred in the downwind region of road-domain environment.They revealedtwo type distributions: exponentialdistribution (Pb&Cr)&skew distribution (Cd, Cu, Ni&Zn). The sizes of atmospheric particulate, absorbing heavy metals, are in decreasing order ofCd=Cu>Cr>Ni>Pb. Pb achieved middle or heavy polluted state in road-domain environment, and thesmallerambient particulate matter is, the more serious its pollutionis. Heavy metals of ambient particulatematter hadcomprehensive non-carcinogen (carcinogen) risk possibility, and Cr is main factor ofriskpossibility. |
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