Abstract
Due to the unique geographical location and rapid development in the agricultural industry, heavy metals’ risk of soil contamination in the Qaidam Basin is gradually increasing. The following study was conducted to determine the soil heavy metal contents under different types of land use, contamination levels, and the physicochemical properties of soil. Soil samples were collected from facility lands, orchards, farmlands, and grasslands at 0–10 and 10–20 cm soil layers. Heavy metals including copper (Cu), chromium (Cr), nickel (Ni), zinc (Zn), lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) were analyzed using inductively coupled plasma mass spectrometry and the soil was evaluated with different methods. Overall, the average Cu (25.07 mg/kg), Cr (45.67 mg/kg), Ni (25.56 mg/kg), Zn (71.24 mg/kg), Pb (14.19 mg/kg), Cd (0.17 mg/kg), As (12.54 mg/kg), and Hg (0.05 mg/kg) were lower than the environmental quality standard. However, the Cu, Cr, Ni, and As were highest in farmland, and Zn and Hg were highest in the facility land. The Pb content was highest in orchards, and the Cd content was the same in facility land, orchards, and farmland. Among the different land-use types, the soil heavy metal concentrations decreased in the order of facility land > farmland > grassland > orchards. The pH was alkaline, the content of SOC (soil organic carbon) 15.76 g/kg in grassland, TN (total nitrogen) 1.43 g/kg, and TP (total phosphorus) 0.97 g/kg in facility land showed the highest result. The soil BD (bulk density) had a significant positive correlation with Cu, Cr, Ni, Zn, Pb, Cd, and the TP positively correlated with Cu, Zn, Cd, and Hg. The soil evaluation results of the comprehensive pollution index indicated that the soil was in a clean condition. The index of potential environmental risk indicates that heavy metals are slightly harmful to the soil.
Highlights
As a significant part of the earth, the soil is an essential sink for nutrients and pollutants [1,2]
The central part of the Qaidam Basin is located in the Qinghai province, in the Tibetan autonomous prefecture of Haixi, which is in relatively low terrain and surrounded by mountains
Hg (61%) had a high coefficient of variation (CV) value, which indicated a high variability of the mercury content between all sampling sites in the Qaidam Basin
Summary
As a significant part of the earth, the soil is an essential sink for nutrients and pollutants [1,2]. Soil pollution by heavy metals is a global problem that has recently received a great deal of attention [3,4]. More than 10 million soil sites are polluted, and more than 50% of these soil sites are contaminated with heavy metals [5]. Heavy metal pollution in soils may result from multiple sources, such as atmospheric deposition, waste disposal, waste incineration, urban effluents, traffic emission, fertilizer application, and the long-term application of wastewater in agriculture [6,7]. The land-use type affects the migration and accumulation of heavy metals in the soil [8,9]. Heavy metals are not naturally degradable and tend to accumulate and turn into more toxic metal compounds that severely affect crop yields and quality [10,11,12,13].
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