**Absorption and Accumulation of Heavy Metal Pollutants in Roadside Soil-Plant Systems – A Case Study for Western Inner Mongolia**

Lu Zhanyuan1, Zhi Yingbiao2,3\*, Wang Zai-lan4, Hua Yupeng2, Hong Ge2, Emmy Camada5 and Yao Yiping1 *1Inner Mongolia Academy of Agricultural Science, Hohhot, 2Ordos College, Inner Mongolia University, Ordos, 3College of Life Science, Nanjing University, Nanjing, 4School of Environment and Natural Resources, Renmin University of China, Beijing, 5Chinese Culture Center of San Francisco, CA, 1,2,3,4China 5USA* 

#### **1. Introduction**

156 Novel Approaches and Their Applications in Risk Assessment

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Soil - plant system is the biosphere and pedosphere whose the basic structural unit of soil is the main target. Soil - plant systems enable human productivity but suffer from pollution damage caused by humans. Currently, the annual loadings of harmful metals in soil are (104 t / a): Hg 0.83, Cd 2.2, Cr 89.6, Pb 79.6, Ni 32.5, Cu 95.4, Zn 137.1, As 8.1, Se 4.1 [1,2]. Contaminated soil will directly, or by amplifying through the food chain, affect the normal function and growth of plant and even human health. At the same time, the ecosystem, through a series of physical, chemical and biological processes in the environment, provides a purification of pollutants. Beyond the loading capacity of the environmental pollution load capacity and super-threshold, its biological production will be affected, resulting in severe loss of productivity and may even directly or indirectly endanger human life and health. Phytoremediation is considered a green technology for the removal of heavy metal pollution in the ascendant [3]. With the rapid development of the national economy and the subsequent traffic pollution, negative environmental effects are becoming increasingly apparent, especially for roadside soil - plant systems. The the evidence is apparent in Shanxi Province where 5,000 km of roadside farmland was polluted by coal dust, reducing food productivity by 2 800 × 104kg [4]. In recent years, car exhaustion and road dust caused heavy metal pollution on the soil-plant systems on both sides of the roads, and consequently, the heavy metal content has brought stress on the structure and function of ecosystem, which increasingly exposed agricultural issues. Currently, research on the domestic and international distribution of heavy metals in soil

<sup>\*</sup> Corresponding Author

Absorption and Accumulation of Heavy Metal Pollutants

Fig. 1. The map of the sampling station.

method, the soil and water ratio of 1:1 [21].

**2.1.3 Determination** 

ground, sieved, bagged, spared, and cold stored [21].

in Roadside Soil-Plant Systems – A Case Study for Western Inner Mongolia 159

And the simultaneous acquisition of the plants as control (CK) is from relatively clean area around the off-road and industrial pollution. Samples of plants was washed with distilled water. Plant roots, stems, leaves and rhizosphere soil samples were naturally air-dried,

Plant (roots, stems and leaves mixed sample, and overall) and soil heavy metal content was assessed by using atomic absorption spectrophotometer Spectr AA DUO, AF 610A, atomic fluorescence spectrometer; traces of heavy metals Cd, Pb, Cu, Zn, Ni, Cr were determined by dry ash method, and perform GB/T5009 in Cd, Pb, Cu, Zn, Ni, Cr atomic absorption spectrometry determination in a muffle oven 500C dry ashing, with 1:1 nitric acid dissolved in 2 ml. The way of metal determination is as follows: the plant samples adopt nitric acid perchloric acid digestion, atomic fluorescence spectrometry; Hg uses aqua regia digestion, atomic fluorescence spectrometry; Se uses nitric acid - perchloric acid digestion, atomic fluorescence spectrometry; rhizosphere soil of heavy metals Cu, Zn, Pb, Ni and Cr speciation experiment uses synchronized Tessier sequential extraction method [22] for the determination of the specific processes shown in Figure 2. Soil pH measured with pH meter

on both sides of the road have been reported [5-10]. At the same time, studies on heavy metal pollution on soil-plant systems on both sides of the road have been carried out [11-17], but only limited studies are conducted on the heavy metal absorption and accumulation on the highway [18]. With the rapid development of the regional economy, the western region of Inner Mongolia produces more coal, building materials, and chemical products, and the rapid increase in traffic and road transport vehicles increased significantly [19]. In 1992, the average traffic in the Inner Mongolia Autonomous Region were 731 vehicles per day. By the end of 2004, the average number of traffic had increased to 5 171 per day, of which 2 533 are State Roads with G109 vehicles / day, G210 are State Roads with 4946 vehicles / day, and G110 are National Roads with 6 739 vehicles / day. With heavy road traffic and associated problems of automobile exhaust emissions becoming more evident, it is necessary to have studies on the accumulation of heavy metals and the potential ecological risk assessment. Therefore, in this study western Inner Mongolia Transport heavy G110 National Road, G210 National Highway and the G109 National Road are selected as study objects, along with highway green vegetable pine (*Pinus tabulaeformis* Carr.) and lobular Yang (*Populus simonii* Carr.) Heavy metal absorption and accumulation and heavy metals in rhizosphere soil and the relationship between distribution and morphology to the road along the soil - plant system bioremediation of heavy metals are investigated to provide theoretical reference.
