Abstract
Levels of trace element pollution in surface soil can be estimated using soil analyses and leaching tests. These methods may reveal different results due to the effect of soil properties, such as grain size and mineral composition, on elemental availability. Therefore, this study advocates an alternative method for monitoring and assessment of trace element pollution in surface soil using terricolous fruticose lichens. Lichens growing at abandoned mine sites and unpolluted areas in southwest Japan and their substrata were analyzed using inductively coupled plasma-mass spectrometry and X-ray fluorescence spectrometry to clarify the relationships between Cu, Zn, As, and Pb concentrations in lichens and soils, including their absorption properties. Concentrations of these elements in the lichens were positively correlated with those in the soils regardless of lichen species, location, habitat, or conditions of soils. The analyzed lichens had neither competitive nor antagonistic properties in their elemental absorption, which made them good biomonitors of trace element pollution in surface soil. The distribution maps of average Cu, Zn, As, and Pb concentrations at each sampling region detected almost all of the Cu, Zn, and As pollution of the soils. Therefore, lichens could be used in practical applications to monitor Cu, Zn, and As pollution in surface soils.
Highlights
Soil pollution has been estimated using soil analyses and leaching tests
To evaluate a practical application of Stereocaulon commixtum and several Cladonia spp. as biomonitors, this study investigated the correlation between concentrations of Cu, Zn, As, and Pb in the lichen thalli and those in the corresponding substrata
This study advocated that the analysis of lichens may be an alternative method for soil analyses or leaching tests to decrease artificial error, time, cost, and secondary environmental impact for assessment and monitoring of soil pollution, which are important advantages for practical applications
Summary
Soil pollution has been estimated using soil analyses and leaching tests. No single laboratory leaching test can evaluate the leaching behavior of a wide variety of material in a broad range of management scenarios [1]. The methods of leaching tests should be chosen after consideration of soil properties, such as chemical and physical properties of soil-forming minerals and climatic conditions of the sampling area. Results differing from the actual condition may be obtained by the leaching test if an inappropriate method is chosen. The leaching test methods may lead to misuse and misinterpretation of the results [1]. Many organisms have been investigated as potential biomonitors as a means to assess the level of soil pollution [2]. The use of local-resident biomonitors growing in a polluted area could reduce the limitations shown in leaching tests. Used indicator organisms include fishes, mollusks, Environments 2016, 3, 35; doi:10.3390/environments3040035 www.mdpi.com/journal/environments
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