Heavy metals accumulated in soils were characterized by polluting large area, non-degradation, and difficulty to clean etc. With human activities, the pollution of heavy metals becomes more and more serious and arouses more attentions by environmentalists and correlative scholars. Longitudinal Range-Gorge Region, located in South-West of China, has many mountain ridges and valleys stretching from north to south. Because of the local native environment, road is the major traffic method. By far the majority of the studies on the impact of road construction on the contents of heavy metals in roadside soils was conducted on the small scale.
We report the spatial distribution and variation of heavy metal contents in the roadside topsoils along the longitudinal, transverse and upright directions on the large scale. In order to provide available study instruct and method on macroscopy scale, the road was divided into three segments: north, middle and south segment. Soil samples were taken at 94 locations from roadside soils along the north, middle and south parts of the Lijiang-Jinghong road in Yunnan Province. The total contents of heavy metals in the soil samples were determined. The following results were found:
(1) In longitudinal direction, the concentrations of Cu, Zn, Pb, Cr, Cd, As, Mg and Mn in roadside soils were higher for the north segment than those for the middle and south segments. Correlation analysis indicated that the construction of road absolutely impacted the longitudinal distribution of Pb, Cd and Zn content in the roadside soils.
(2) In transverse direction, the contents of heavy metals in roadside soils varied in uniform trend with soil types and soil utilization manners, indicating that the construction of road had crucial impact on the transverse spatial variability of heavy metal contents. This impact extended to 50 m away from the road.
(3) In vertically direction, the spatial variability of heavy metal contents in native soils was not significant and heavy metals were concentrated only in the roadside soils close to the road. Because of the local influence of artificial counterfort, there was no vertical spatial variability in constructing area.