Elemental compositions of lichens from Duolun County, Inner Mongolia, China: Origin, road effect and species difference.

To assess the response of lichen elemental compositions to road traffic and species difference in the context of high dust input and anthropogenic emissions, two foliose epiphytic lichens (Phaeophyscia hirtuosa, PHh; Candelaria fibrosa, CAf) were sampled near a road adjacent to Dolon Nor Town (Duolun County, Inner Mongolia, China). Twenty elements (Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, Sb, Sr, Ti, V and Zn) in lichen and surface soil samples were analysed using inductively coupled plasma mass spectrometer (ICP-MS). The results demonstrate that lichen elemental compositions are highly influenced by both their natural environment and anthropogenic input. Windblown dust associated with sand dunes and degraded/desertified steppes represents the predominant source of lichen elements. Road traffic can enhance the lichen elemental burden by increasing the number of soil particles. Anthropogenic emissions from the town and road traffic have also led to the enrichment of Cd and Zn in lichens. PHh was higher than CAf in concentrations of 14 terrigenous metals. Both lichens are applicable to biomonitoring of atmospheric element deposition and, in most cases, yield comparable results.

Determination of Elemental Concentrations in Lichens Using ICP-AES/MS.

Lichens are good biomonitors for air pollution because of their high enrichment capability of atmospheric chemical elements. To monitor atmospheric element deposition using lichens, it is important to obtain information on the multi-element concentrations in lichen thalli. Because of serious air pollution, elemental concentrations in thalli of lichens from North China (especially Inner Mongolia, Hebei, Shanxi and Henan province) are often higher than those from other regions, therefore highlighting the necessity to optimize ICP-AES/MS (Inductively coupled plasma-atomic emission spectroscopy/mass spectrometry) for analyzing lichen element content. Based on the high elemental concentrations in the lichen samples, and the differences in the sensitivity and detection limits between ICP-MS and ICP-AES, we propose a protocol for analyzing 31 elements in lichens using ICP-AES/MS. Twenty-two elements (Cd, Ce, Co, Cr, Cs, Cu, K, La, Mo, Na, Ni, Pb, Rb, Sb, Sc, Sm, Sr, Tb, Th, Tl, V and Zn) can be identified by using microwave digestion- ICP-MS, and 9 elements (Al, Ba, Ca, Fe, Mg, Mn, P, S and Ti) by using ashing-alkali fusion digestion- ICP-AES.

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

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.

Optimization of ICP-AES and ICP-MS Techniques for the Determination of Major, Minor and Micro Elements in Lichens.

Lichens are one of the best materials for air quality biomonitoring, and they have been widely used in atmospheric element deposition monitoring in many regions. Inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) are two efficient techniques widely used in quantifying and quantifying plant elements. However, elemental levels in lichens from some regions in China are much higher than in other plants, and their variation is highly dependent on space, time, species and elements. Although atmospheric pollution monitoring is urgently needed in China in recent decades, little studies have been performed on biomonitoring in the country. Therefore, the methodological studies on the determination of lichen elements in China are needed to accelerate future biomonitoring studies with lichens. Two techniques such as ICP-MS and ICP-AES were used to determine elements in four reference materials, as GBW10014 (cabbage), GBW10015 (spinach), GBW10052 (green tea) and IAEA-336 (lichen), with an attempt to reveal the effects of different digestions, sampling size, spectral lines, isotopes and internal standard elements on measured results. ICP-AES after dry ashing-alkali fusion digestion and ICP-MS after microwave digestion were optimized for lichen element determination. In the optimized techniques, good linear relationship (r>0.999 0), low detection limit, high analytic accuracy and precision were obtained. The optimized techniques were applied to lichen samples collected from Taihang Mountains of China and Ardley Island of Antarctica. The results show that all lichen samples from Taihang Mountains were much higher in elemental concentration with the contribution of atmospheric deposition higher than those from Antarctica. These results suggest the applicability of the techniques in determining lichen elements, and provide evidences and technique supports for air pollution biomonitoring in China.