GEOCHEMICAL CHARACTERISTICS OF SOME TROPICAL PLANTS IN HAINAN ISLAND
海南岛某些热带植物的地球化学特征

The present work was conducted to study tropical forest located in Hainan Island in Southern China. The climate of that area is of typical monsoon, with an average annual rainfall of 2000mm in eastern part of the Island, and 1000mm in western part. The Hainan Island itself has a clear-cut dry season from November to April, when rainfall is only about 20% of the total. Due to variety of ecological environment, the evergreen monsoon forest, tropical rain forest, tropical deciduous forest, evergreen broadleaf forest, and savannas all grow in Hainan Island. 77 tree species have been collected from tropical forest. Content of Fe, Cu, Mn, Ni, Ca, Mg, K, in the tropical forest of Hainan Island area was determined by atomic absorption method. The mean values of these elements in various plants are given.Content of Si, Fe, Mn, Cu, Zn, in coniferous tree and herbosa is higher than those in the broadleaf tree. Higher concentration of Ca as a nutrient element was seen in coniferous tree, but higher concentration of K and Mg was seen in herbosa and broadleaf tree. Samples obtained from different parts of plant, including root, stem, leaf and bark show a rather great difference in elemental content.Background value of lead in tropical plants, soils and rocks is respectively 40ppb, 20.9ppm and 28.8ppm. The Casuarina equisetifolia growing nearby highway contains higher concentration of Pb than those faraway from it. Pb content in leaf and bark is 264ppb and 2400ppb respectively. It can obviously be in connection with atmospheric pollution nearby the highway.