Lichen elemental composition distinguishes anthropogenic emissions from dust storm inputs and differs among species: Evidence from Xilinhot, Inner Mongolia, China

Hua-Jie Liu,Xiao-Di Liu,Si-Wa Liu,Jian-Sen Hu,Yun-Jun Jiang,Qing-Feng Wu,Yu Xia,Shi-Bo Fang,Liang-Cheng Zhao,Yi-Dan Wang,Xiu-Ping Guo

doi:10.1038/srep34694

Abstract

To test the applicability of lichens in the biomonitoring of atmospheric elemental deposition in a typical steppe zone of Inner Mongolia, China, six foliose lichens (Physcia aipolia, PA; P. tribacia, PT; Xanthoria elegans, XE; X. mandschurica, XM; Xanthoparmelia camtschadalis, XPC; and Xp. tinctina, XPT) were sampled from the Xilin River Basin, Xilinhot, Inner Mongolia, China. Twenty-five elements (Al, Ba, Cd, Ce, Cr, Cs, Cu, Fe, K, La, Mn, Mo, Na, Ni, P, Pb, Sb, Sc, Sm, Tb, Th, Ti, Tl, V and Zn) in the lichens were analysed using inductively coupled plasma mass spectrometry (ICP-MS). The results show that Cd, Pb and Zn were mainly atmospheric in origin, whereas the other elements were predominantly of crustal origin. Compared with other studies, our data were higher in crustal element concentrations and lower in atmospheric element concentrations, matching with the frequent, severe dust storms and road traffic in the area. The elemental concentrations in lichens are both species- and element-specific, highlighting the importance of species selection for biomonitoring air pollution using lichens. We recommend PT, XE, XM and XPT for monitoring atmospheric deposition of crustal elements; XPC and XPT for Cd and Pb; PA for Cd and Zn; and PT for Cd.

Highlights

To test the applicability of lichens in the biomonitoring of atmospheric elemental deposition in a typical steppe zone of Inner Mongolia, China, six foliose lichens (Physcia aipolia, PA; P. tribacia, PT; Xanthoria elegans, XE; X. mandschurica, XM; Xanthoparmelia camtschadalis, XPC; and Xp. tinctina, XPT) were sampled from the Xilin River Basin, Xilinhot, Inner Mongolia, China
Studies on the atmospheric deposition of elements in Inner Mongolia have mainly focused on nitrogen[3,4]
Lichens are widespread in the diverse ecosystems of Inner Mongolia, they have not been applied to air quality assessment in the region

Summary

Introduction

To test the applicability of lichens in the biomonitoring of atmospheric elemental deposition in a typical steppe zone of Inner Mongolia, China, six foliose lichens (Physcia aipolia, PA; P. tribacia, PT; Xanthoria elegans, XE; X. mandschurica, XM; Xanthoparmelia camtschadalis, XPC; and Xp. tinctina, XPT) were sampled from the Xilin River Basin, Xilinhot, Inner Mongolia, China. Atmospheric metal deposition has become a major environmental problem in China due to its adverse effects on human and ecosystem health[1,2] This is true in Inner Mongolia, where frequent dust storms (due to steppe degradation and desertification) and air pollution (associated with the increasing urbanization and industrialization) have occurred in recent decades. Lichens can be a complement, or to a lesser extent, an alternative to the traditional methods of studying atmospheric deposition from anthropogenic or natural sources and have been widely used outside of China in the past few decades[5,6] These organisms are highly dependent on atmospheric deposition for mineral nutrients and have the extraordinary capability of accumulating metals far above their need. Two questions are prerequisite to the assessment of air quality in Inner Mongolia using lichens. (1) Can lichens distinguish anthropogenic contribution from dust storm inputs? This question has rarely been addressed because most relevant studies have been performed in industrial/urban or remote sites without dust storms7–13. (2) Which lichen should be selected as a biomonitor? Species selection is necessary in such studies because the metal concentrations and enrichment capability are different among lichens[5,14,15,16]

Methods

Results

Conclusion