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Journal of Geographical Sciences    2015, Vol. 25 Issue (12) : 1439-1451     DOI: 10.1007/s11442-015-1244-1
Research Articles |
Contamination and health risk assessment of heavy metals in road dust in Bayan Obo Mining Region in Inner Mongolia, North China
LI Kexin,LIANG Tao(),YANG Zhiping(),YANG Zhiping
Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
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The objective of this study was to investigate the concentration and spatial distribution patterns of 9 potentially toxic heavy metal elements (As, Cd, Co, Cr, Pb, Cu, Zn, Mn, and Ni) in road dust in the Bayan Obo Mining Region in Inner Mongolia, China. Contamination levels were evaluated using the geoaccumulation index and the enrichment factor. Human health risks for each heavy metal element were assessed using a human exposure model. Results showed that the dust contained significantly elevated heavy metal elements concentrations compared with the background soil. The spatial distribution pattern of all tested metals except for As coincided with the locations of industrial areas while the spatial distribution of As was associated with domestic sources. The contamination evaluation indicated that Cd, Pb, and Mn in road dust mainly originated from anthropogenic sources with a rating of “heavily polluted” to “extremely polluted,” whereas the remaining metals originated from both natural and anthropogenic sources with a level of “moderately polluted”. The non-cancer health risk assessment showed that ingestion was the primary exposure route for all metals in the road dust and that Mn, Cr, Pb, and As were the main contributors to non-cancer risks in both children and adults. Higher HI values were calculated for children (HI=1.89), indicating that children will likely experience higher health risks compared with adults (HI=0.23). The cancer risk assessment showed that Cr was the main contributor, with cancer risks which were 2-3 orders of magnitude higher than those for other metals. Taken in concert, the non-cancer risks posed by all studied heavy metal elements and the cancer risks posed by As, Co, Cr, Cd, and Ni to both children and adults in Bayan Obo Mining Region fell within the acceptable range.

Keywords road dust      heavy metal elements      contamination assessment      health risk assessment      Bayan Obo Mining Region     
Fund:National Natural Scientific Foundation of China, No.41571473, No.41401591
Corresponding Authors: LIANG Tao,YANG Zhiping     E-mail:;
Issue Date: 05 January 2016
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LI Kexin,LIANG Tao,YANG Zhiping, et al. Contamination and health risk assessment of heavy metals in road dust in Bayan Obo Mining Region in Inner Mongolia, North China[J]. Journal of Geographical Sciences, 2015, 25(12): 1439-1451.
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Figure 1  Map of the study area and sampling sites in Bayan Obo Mining Region (April 2014)
Igeo value Class
Igeo ≤0 Unpolluted
0 < Igeo≤1 Unpolluted/Moderately polluted
1 < Igeo≤2 Moderately polluted
2 < Igeo≤3 Moderately polluted/Strongly polluted
3 < Igeo≤4 Strongly polluted
4 < Igeo≤5 Strongly polluted/Extremely polluted
Igeo > 5 Extremely polluted
Table 1  The classification of contamination levels based on the Igeo values
Factor Definition Value Unit Reference
Adults Children
BW Average body weight 70 15 kg EPA, 1989
IngR Ingestion rate 100 200 mg·day-1 EPA, 1989
InhR Inhalation rate 20 7.6 m3·day-1 Zheng et al., 2010a
PEF Particle emission factor 1.36×109 m3·kg-1 EPA, 2001
SA Surface areas of the skin that contacts the airborne particulates 5700 2800 cm-2 EPA, 2004
SL Skin adherence factor 0.07 0.2 mg·m-3
EF Exposure frequency 180 180 days·year-1 Zheng et al., 2010a
ED Exposure duration 24 6 years EPA,2001
ET Exposure time 24 hours·day-1
AT (non-cancer risk) Averaging time ED×365 days
AT (cancer risk) Averaging time 70×365 days
ABS Dermal absorption factor 0.03 for As,
0.001 for other metals
- EPA,2004
CF Conversion factor 1×10-6 kg·mg-1
Table 2  Exposure factors
Concentration Maximum Minimum Mean Geometric mean Median S.D. Inner Mongolia B.
Cd 4.63 1.21 2.20 2.05 1.83 0.90 0.037
Co 41.27 20.65 26.94 26.62 25.74 4.49 9.0
Cr 260.80 85.09 141.24 136.76 139.60 38.46 35.7
Cu 51.09 20.49 36.39 35.75 36.36 6.79 12.7
Pb 526.70 88.04 183.93 167.51 160.50 95.41 13.5
Zn 729.00 192.00 299.37 283.92 261.80 117.51 47.5
As 19.46 8.01 12.02 11.78 11.49 2.57 6.1
Ni 49.82 24.96 31.25 30.85 29.41 5.52 16.6
Mn 7956.00 1575.00 3407.30 3206.43 3172.00 1349.94 434.3
Table 3  The concentrations of heavy metals in road dust collected in Bayan Obo (April 2014, mg·kg-1)
Concentration Cd Co Cr Cu Pb Zn As Ni Mn Reference
Bayan Obo 2.20 26.94 141.24 36.39 183.93 299.37 12.02 31.25 3407.30 This study
Hangzhou 1.59 19.96 51.29 116.04 202.16 321.40 25.88 509.56 Zhang and Wang, 2009
Urumqi 1.17 10.97 54.28 94.54 53.53 294.47 43.28 926.60 Wei et al., 2009
Shanghai 1.23 159.30 196.80 294.90 733.80 83.98 Shi et al., 2008
Baoji 15.90 126.70 123.17 433.20 715.30 19.80 48.80 804.20 Lu et al., 2009
Nanjing 139.0 238.0 113.0 307.0 47.0 786.0 Liu et al., 2014
Inner Mongolia B. 0.037 9.0 35.7 12.7 13.5 47.5 6.1 16.6 434.3 Xu et al., 2004
Gao et al., 2007
China B. 0.07 11.2 53.9 20.0 23.6 67.7 11.2 23.4 482.0 Xu et al., 2004
Table 4  The average concentrations of heavy metals in road dust in different areas (mg·kg-1)
Figure 2  Map of the study area and sampling sites in Bayan Obo Mining Region (April 2014)
Figure 3  The Igeo value of heavy metals in road dust in Bayan Obo (April 2014)
Figure 4  Non-carcinogenic risk distribution of different exposure ways for children and adults in Bayan Obo (April 2014)
Igeo Cd Co Cr Cu Pb Zn As Ni Mn Reference
Bayan Obo 5.21 0.98 1.35 0.90 3.05 1.99 0.36 0.31 2.30 This study
Hangzhou 3.14 0.10 -1.10 1.70 2.42 1.51 -0.88 -0.98 Zhang and Wang, 2009
Urumqi 0.80 -0.30 -0.10 0.40 0.30 0.50 0.00 0.00 Wei et al., 2009
Shanghai 2.65 0.50 2.19 2.94 2.54 0.84 Shi et al., 2008
Baoji 1.79 3.19 2.58 3.04 0.17 -0.21 Lu et al., 2009
Table 5  The average Igeo values of heavy metals in road dust in different areas
Cd Cr Cu Pb Zn Co As Ni Mn
EF 81.37 5.31 3.74 19.51 8.82 3.98 2.57 2.53 11.0
Table 6  The average EFs values of heavy metals in road dust collected in Bayan Obo (April 2014)
C (95%UCL) Oral RfD Inhal RfD Dermal RfD HQ ingestion
Adult Children
Cd 2.59 1.00E-03 1.00E-03 5.00E-05 1.82E-03 1.70E-02
Cr 157.87 3.00E-03 2.86E-05 6.00E-05 3.71E-02 3.46E-01
Cu 39.33 4.00E-02 4.02E-02 1.20E-02 6.93E-04 6.47E-03
Pb 225.19 3.50E-03 3.52E-03 5.25E-04 4.53E-02 4.23E-01
Zn 350.18 3.00E-01 3.00E-01 6.00E-02 8.22E-04 7.68E-03
Ni 33.63 2.00E-02 2.06E-02 5.40E-03 1.18E-03 1.11E-02
Co 28.88 2.00E-02 5.71E-06 1.60E-02 1.02E-03 9.49E-03
As 13.13 3.00E-04 3.01E-04 1.23E-04 3.08E-02 2.88E-01
Mn 3991.06 4.60E-02 1.43E-05 1.84E-03 6.11E-02 5.70E-01
Sum 1.80E-01 1.68E+00
HQ inhalation HQ dermal HI
Adult Children Adult Children Adult Children
Cd 2.81E-07 4.98E-07 1.52E-04 9.98E-04 1.98E-03 1.80E-02
Cr 5.71E-04 1.01E-03 7.39E-03 4.84E-02 4.50E-02 3.95E-01
Cu 1.01E-07 1.80E-07 1.00E-05 6.55E-05 7.03E-04 6.53E-03
Pb 6.98E-06 1.24E-05 1.27E-03 8.32E-03 4.66E-02 4.31E-01
Zn 1.34E-07 2.38E-07 1.82E-05 1.19E-04 8.41E-04 7.79E-03
Ni 1.65E-07 2.93E-07 1.71E-05 1.12E-04 1.20E-03 1.12E-02
Co 5.23E-04 9.27E-04 5.06E-06 3.32E-05 1.55E-03 1.05E-02
As 4.57E-06 8.11E-06 9.00E-03 5.90E-02 3.98E-02 3.47E-01
Mn 2.89E-02 5.13E-02 6.10E-03 3.99E-02 9.61E-02 6.62E-01
Sum 3.00E-02 5.32E-02 2.40E-02 1.57E-01 2.34E-01 1.89E+00
Table 7  HIs for each non-carcinogenic metal in road dust collected in Bayan Obo (April 2014)
Figure 5  The HQs of each heavy metal in road dust in Bayan Obo for adults (a) and children (b) (April 2014)
Cd Cr Ni Co As
Inhal SF 6.30E+00 4.20E+01 8.40E-01 9.80E+00 1.51E+01
R 8.37E-10 3.40E-07 1.45E-09 1.45E-08 1.02E-08
Table 8  Cancer risks for each carcinogenic metal in road dust collected in Bayan Obo (April 2014)
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