The Heavy Metals Analysis Of Lichens In Nanshan In Urumqi And Xilinhot Grassland

With the improvement of living standards,people are increasingly interested in the pursuit of natural products in terms of health care products and food.Due to its potential value in aspects of edible and medical,lichens which is a kind of algae bacterial symbionts has been used as vegetables and health products and attracted people’s interest gradually.However lichens’ eco-physiological characteristics have decided its enrichment capacity for heavy metals,while toxic heavy metals can do harm to human health.The research on lichens whether meets the food standards in terms of heavy metal content or not is still a lack.This is a preliminary study of edible lichen which selects two areas where is relatively light in air pollution,Nanshan in Urumqi and Xilinhot grassland.The study is based on the standards of National pollution-free vegetables in restrictions on Pb,Cr,Cd content and the relationship between excessive degree and the collection site,the substrate,the growth type.164 lichen samples are measured,belonging to 27 genera of 62 species of 164 copies.In which 9 genera of 19 species of 13 copies is gathered in NANSHAN and 22 genera of 50 species of 145 copies is gathered in Xilinhaote grassland.The results are as follows:1)When we put all the lichen samples as a whole sample for analysis,the content of this three elements were significantly exceeded the national standard of the highest value.Cr exceeded the highest multiples(70 times on average),followed by Pb,Cd exceeded the lowest multiples.2)In paticular,almost all of the growth form of all the elements are beyond the national standards.And the relationship between the excessive magnitude and growth-type of these three kinds of elements was not significant.The difference of excessive multiples of Pb and Cr element in leaflike lichens was significant between two places.The excessive multiples of Pb and Cr of leaflike lichens gathered in Urumqi are higher than that in Xilinhot.3)The content of Pb in the same lichen will varies due to the difference of substrate.There are differences between lichens of distinct growth types,even when they are gathered in the same substrate.The excessive multiples of Pb in lichens grown in rocks are higher than those grown in trees and soil.Collection sites will produce large differences of Cr enrichment in two places when the lichens are of the same growth type.There is no significant difference of Cr enrichment between distinct substrates when the lichens are of the same growth type.Collection site,growth type and substrate produce no significant influence on Cd enrichment.4)The contents of Pb,Cr and Cd in lichens have all reached the level of doing harm to human health.There are differences between the content of these three elements,Cr > Pb > Cd.The dissertation not only systematically analyzed the content of Pb,Cr and Cd in lichens gathered in NANSHAN in Urumqi and Xilinhot grassland but also conducted a research of the main effects and interactions on the excessive multiple levels of three elements in lichens.It will clarify whether lichen are edible or not and provide theoretical foundation of the relationship between excessive multiple levels of heavy metals in lichens and collection sites,substrates and growth types.It also provide references for lichen’s edible and medical use.