Characteristics of Metal Element Distribution in Urban Surface Soil and Plants: Observations in Kyoto City Area and Stochastic Analysis

Abstract

To design a rational management system of urban soil pollution, it is necessary to know first the regional soil pollution characteristics and their governing mechanism. In this study, the X-ray fluorescence (XRF) method was selected for quick monitoring of metal concentrations in many solid samples. Soil and plant samples were collected along two streets and at a sports ground in Kyoto City area, and their metal concentrations were determined by the XRF method. Those metal concentrations in soil and plants were analyzed in a stochastic manner. The results obtained in this study can be summarized as follows: (i) The XRF method is useful for quick monitoring of many solid samples because its simple pre-treatment requirement for concentration determination. The practical quantitative detection limits are determined (e.g., 0.010mg g−1 for Zn). (ii) Metal concentrations in surface soils along two streets in Kyoto City showed that the soil contamination was heavier in the central part of the city. (iii) Some metal concentration correlation with sampling distance showed a distance dependent decrease of correlation coefficient, but other metals did not, which suggested random distribution in surface soil of the surveyed area. (iv) Most metal concentrations in grasses had a negative correlation with some element concentration in soil, and some metal concentration in grasses was larger than in soil. These facts indicate that grasses might be used for remediation of polluted soil.