Geochemical features of poplar leaf elemental composition in urban areas

Relevance of the work is caused by the necessity of obtaining new data on natural and anthropogenic geochemical processes, occurring under conditions of widespread urbanization and industrial development, the development of biogeochemical indicators to measure the impact of environmental factors on human health and urban systems. The main aim of the study is quantitative estimation of factors of natural and man-made biogeochemical peculiarities of urban system with intensive transport and industrial infrastructure based on the data of elemental analysis of poplar leaf ash. The methods used in the study: selection of poplar leaf samples on a uniform grid of 2x2, 1x1, 0,5x0,5 km; ashing the samples at 450 °C with determination of ash content in accordance with GOST 26929-94; quantitative instrumental neutron activation analysis (determination of content of 28 chemical elements); empirical data processing and analysis by correlation, cluster and factor (method of principal components) analyzes, as well as with the use of indicator ratios: Th/U, La/Th, La/Lu, La/Yb, La/Sm, Ce/Nd, La+Ce/Sm+Eu, La+Ce/Yb+Lu. The results. The authors have determined the contents of some major (Na, Ca, Fe), trace, rare earth (REE) and radioactive (U, Th) elements in poplar leaf ash in some cities of Kazakhstan, southern Siberia and Far East of Russia. General character of element chemical distributions in samples follows the universal geochemical law. Biophil (Br, Zn) and specific for biological species (Au, Ag, Sr) elements are accumulated in poplar leaf ash. The authors determined the abnormal geochemical associations of elements for urban systems with different industrial specialization. It is shown that the high value of the ratio Th/U (>2) mainly reflect the impact of natural environmental factor, and low values of Th/U value (