The Effect of Different Cleaning Methods on Needles for Assessing the Atmospheric Heavy Metal Retention Capacity of Three Coniferous Trees

Tong Liu,Mei Zhang,Kefan Wang,Fuchen Shi,Yihan Wang,Lili Tang

doi:10.3390/app11041668

Abstract

Urban air pollution has received increasing attention in recent years. To investigate the interaction between several heavy metal elements and the degree of atmospheric pollution, the leaves of three evergreen tree species—Chinese juniper (Juniperus chinensis L.), dragon juniper (Juniperus chinensis L. ‘Kaizuca’), and cedar (Cedrus deodara (Roxb. ex D.Don) G.Don)—were collected from main road intersections in the urban area of Tianjin, China. Two different treatments—water washing (WW) and ethanol washing (EW)—were used, and the contents of Cu, Mn, Cd, and Zn were measured in both washed and unwashed (UW) leaves. It was found that the heavy metal contents within Chinese juniper and dragon juniper were ranked as Mn > Zn > Cu > Cd, and the metal accumulation index (MAI) value was higher for dragon juniper. For the three plants, water washed off 5.36% to 58.58% of the total heavy metals in the needles, while ethanol washed off 16.08% to 71.60% of the total. Both washes were more effective for Cu, Zn, and Cd, and especially for the element Cd. Ethanol could clean off 38.64% to 71.60% of the total Cd from the leaves. Ethanol had a better elution effect compared to water, and the trend of the Cd content in the leaves of the three plants showed a change after the use of different washing methods, which suggests that the water washing may have masked the real difference.

Highlights

Received: 29 December 2020Heavy metal pollution has received increasing attention in recent years because it can threaten human health to different degrees [1,2]
The ranking of heavy metal contents in both Chinese juniper and dragon juniper was Mn > Zn > Cu > Cd, which was similar to the trend of heavy metal contents in
The relatively low Cd content in the needles of the three plants and the high metal accumulation index (MAI) value in the dragon juniper provide a direction for the treatment of heavy metal pollution in the atmosphere

Summary

Introduction

Heavy metal pollution has received increasing attention in recent years because it can threaten human health to different degrees [1,2]. Many studies have been conducted on the sources and contents of heavy metals in soil, the atmosphere, and water [4,5,6]. A method for directly detecting the degree of atmospheric heavy metal pollution is to detect heavy metals in different particle matters (PM). The use of this method to indicate environmental pollution has not been comprehensively analyzed. This is because the level of heavy metals in the environment may be high, but only a small proportion belongs to the bioavailable fraction

Methods

Results

Discussion

Conclusion