Heavy Metal Concentrations in Orchard Soils with Different Cultivation Durations and Their Potential Ecological Risks in Shaanxi Province, Northwest China

Hongmei Dong,Jingbo Zhao,Mengping Xie

doi:10.3390/su13094741

Abstract

The heavy metal pollution of soils, resulting from long-term fertilizing activity, is becoming serious in many countries, endangering ecological safety and human health. This study employed inductively coupled plasma-mass spectrometry (ICP-MS) to investigate concentrations of eight heavy metal elements (Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn) in five apple orchard soil profiles after different cultivation durations, one modern intercropping farmland soil profile, and one natural soil profile from Baishui County, in Shaanxi Province, Northwest China. The potential risk associated with the presence of heavy metals in the soils was assessed by the single-factor pollution index (Pi), Nemerow comprehensive index (NCI), and potential ecological risk index (RI). Results showed that the average concentrations of Cr, Ni, As, Pb, and Hg in the farmland soil were higher than those in the apple orchard soils. The average concentrations of Ni, Cu, As, and Hg in the apple orchard soils reached the highest after 25 years of cultivation. The results imply that concentrations of heavy metals will increase with increasing cultivation time. The farmland soil had the highest NCIs, while the NCIs of the apple orchard soils also increased with cultivation time. Compared with the quality standards of pollution-free orchards and green food production areas, all Pis and NCIs were less than 1 and 0.7, respectively, indicating that the soils were in healthy condition. The RI results also suggest that the soils have a low ecological risk (RI < 150). Although the potential ecological risk is currently low, predicting and reducing heavy metal input should be considered.

Highlights

A healthy farmland ecosystem is a basic requirement, for food safety and for human health [1]
The intercropping farmland soil (IFL) soil had the highest risk index (RI) value, but all RI values were lower than 15, and much less than the threshold of 150 (Figure 7). These results indicate that the potential ecological risk in apple orchards and farmland is low
Heavy metal elements such as Cr, Ni, As, Pb, and Hg were more enriched in intercropping farmland soil than in apple orchard soil

Summary

Introduction

A healthy farmland ecosystem is a basic requirement, for food safety and for human health [1]. Heavy metal pollution negatively affects plant/fruit quality and yield, and causes changes in the size, composition, and activity of the microbial community [2]. The uptake of heavy metals by plants and their subsequent accumulation along the food chain may result in great health risks to animals and humans. To reduce disease and boost yields, farmers use fertilizers and pesticides containing heavy metals, which directly affect the quality and safety of fruits [3,4,5,6,7,8],

Methods

Results

Conclusion