Effects of Landscape Features on the Roadside Soil Heavy Metal Distribution in a Tropical Area in Southwest China

Yuhong Dong,Fangfang Wang,Yixuan Liu,Yongxiu Sun,Shiliang Liu

doi:10.3390/app11041408

Yuhong Dong, Fangfang Wang + Show 3 more

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https://doi.org/10.3390/app11041408

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Abstract

Soil heavy metals along roadsides pose a great threat to ecosystems while their spatial variations and influencing factors still remain unclear in some regions, especially in tropical areas with complex landscape characteristics. Our study was carried out to determine how the land use, vegetation characteristics, topographical factors and distance to the road affect the soil heavy metal distribution. Taking Jinghong county in Yunnan Province, Southwest China as a case, soil samples were collected at different distances off roads and canonical correspondence analysis (CCA) methods were used to determine the relative importance of different factors. Our results showed that heavy metal sources were obtained mainly from the road, based on the principle component analysis (PCA) identification. There were no obvious trends of soil quality index (SQI) with distance to the road in natural soils, while SQI nutrients and SQI metals in farmlands had a decreasing and increasing trend, respectively, which could both be expressed by logarithm models. However, soil properties showed little differences for road levels while they showed significant differences under land use types. The CCA further showed that heavy metal variations in natural soils were jointly affected by distance, plant coverage, relative elevation and soil properties in decreasing order.

Highlights

Roads, as an important linear landscape element, affect both abiotic and biotic ecosystems, especially the vegetation composition and soil properties along them [1,2]
It is very clear that the soil quality index (SQI) values varied greatly in the natural soils regardless of soil nutrients or soil heavy metals (Figure 2a)
Different weights could be added for different soil factors to get a comprehensive SQI, studies showed that soil deterioration index method with direct difference was a simple and effective way to determine the changes of soil quality [13]

Summary

Introduction

As an important linear landscape element, affect both abiotic and biotic ecosystems, especially the vegetation composition and soil properties along them [1,2]. In China, the development of road networks has been rapid with many high-level roads being constructed in recent years [7]. The negative effects, such as pollution, ecological damage, landscape fragmentation and hydrological connectivity interruption, are becoming more and more prominent and causing severe environmental, economic and even social issues, it is necessary to pay great attention to the road ecological protection [8]. The road effect zone suffers from long-term accumulation of heavy metals, and these pollutants have an impact on the environment and nearby ecosystems. More studies have shown the contamination by these elements and the distribution of heavy metals in road dusts and soils [16,17,18]. Gasoline containing lead has been forbidden in China, the exhaust gas containing other heavy metals still shows significant effects on the soils

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