B. Papp szerk.: Studia Botanica Hungarica 29. 1998 (Budapest, 1999)

Iqbal, M. Z., Sherwani, A. K.; Shafiq, M.: Vegetation characteristics and trace metals (Cu, Zn and Pb) in soils along the super highways near Karachi, Pakistan

Studia bot. hung. 29, pp. 79-86, 1998 (1999) VEGETATION CHARACTERISTICS AND TRACE METALS (CU, ZN AND PB) IN SOILS ALONG THE SUPER HIGHWAYS NEAR KARACHI, PAKISTAN M. Z. IQBAL, A. K. SHERWANI and M. SHAFIQ Dept. Botany, University of Karachi Karachi-7

5270, Pakistan In this study, Senna holosericea and Prosopis juliflora are found to be the leading dominant species because of their wide ecological tolerance along the Super Highway near Sohrab Ghoth in Karachi. Abutilon indicum, Fagonia indica and Blepharis sindica were also found as leading species in other stands, but their importance values were rather low. Heavy metals such as Cu, Zn and Pb in stands dominated by P. juliflora and S. holosericea showed their broad range of occurrence, particularly for P. juliflora. One of the stands in which B. sindica was dominant, highest concentration of Cu (305 pg g~ ) and the lowest levels of Zn (35 pg g-1

) and Pb (15 pg g-1

) have been reported. Considerable higher values of Cu, Zn and Pb metals have been recorded in some of the stands, where Suaedafmucosa and Salsola baryosma was associated with P. juliflora. Key words: air pollution, heavy metal, highway, Pakistan, soil INTRODUCTION Pollution by heavy metals is a worldwide problem. These metals are discharged in to the air by man-made activities, e.g. industries, auto vehicles etc. In heavily populated areas, automobile activity is one of the major sources of heavy metal pollution, particularly on the major highways in cities. Some of the heavy metals of which lead is the most important one are dispersed in the environment mainly through the exhaust gases of automobiles (ALBASEL and COTTENIE 1985, BEYER and MOORE 1980, BISHOP et al. 1975, DAVIES and HOUGHTON 1984, GILES et al. 1973, HARRISON and JOHNSTON 1985, HARRISON et al. 1985, KRYYSTOFIAK 1986, MADANY et al. 1990, PRICE et al. 1974, UDEVITZ et al. 1980) to a lesser extent through the emissions of industry (MAKOVSKÁ 1978, STARY and KUBIZMAKOVÁ 1987). Mostly lead is found in the aerial parts of plants and little translocation occurs (ALSTAD et al. 1982, GILES et al. 1973). Effects on plant communities are most easily studied where a heavily polluting industry affects natural vegetation. An iron sintering plant at Sudbury, Ontario, releasing sulfur dioxide in an area of spruce forest (GORHAM and GORDON 1963) about 25 km from the plant, the dominant spruce trees of the forests were