Natural background levels of trace elements in wild plants

Abstract

Natural background levels of trace elements in wild plants were investigated. Firstly, the validity of the analytical methods using inductively-coupled plasma mass spectroscopy after wet digestion with HNO3 and HF was confirmed. Measurement results for standard plant material were almost the same as the certified values of Cu, Zn, Mo, Cd, Sb, and Pb. Additionally, other 6 elements, Be, Cs, La, Ba, n, and Bi were also analyzed simultaneously. Secondly, 87 plant species were collected from our Institute, and the basic statistical parameters of the element concentrations were calculated. Although distribution of the concentrations of Cu, Zn, Mo, Ca, Sb, and Pb displayed as logarithms was considered to be more symmetrical than that of normal data, only distribution of Cu and Cd fitted to a normal curve by chi-square test. Variance of element concentration was larger among species than within a species. Thirdly, plants and soils from 16 sites located in the central and eastern parts of Japan were collected. Median values of elemental concentrations in wild plants were used as representative values of a site, and median values among sites were 7.17,28.2, 0.367,0.150,0.031,0.701,0.009,0.043,32.4,0.125, 0.010, and 0.006 for Cu, Zn, Mo, Cd, Sb, Pb, Be, Cs, Ba, La, Tl, and Bi, respectively. The results for Cu, Zn, Mo, Pb, Be, La, and Bi were similar to the element concentrations for "Reference Plant," cited from a study by Markert (Markert, B. 1992: Multi-element analysis in plant materials. Analytical tools and biological questions. In Biogeochemistry of Trace Metals, Ed. D.C. Adriano, p. 401–428, Lewis Publishers, Boca Raton). The level of Cd was slightly higher and the levels of Sb, Cs, and Tl slightly lower than those of the “Reference Plant.” Our results for Be were 10-times as high as that for the “Reference Plant,” but very close to the concentrations reported by other researchers in Japan. Finally, to investigate the relationship of trace element concentrations between plants and soils, element concentrations in soils were analyzed after extraction with HF and HNO3 A high correlation was found in the case of Tl, but not for the other elements.