Characteristics of Vegetational Distribution of Weeds in Petroleum-Contaminated Soil

Vegetational characteristics of weeds in petroleum contaminated soil were examined and compared with those of uncontaminated field. To know the intensity of oil pollution total petroleum hydrocarbon (TPH) and benzene, toluene, ethylbenzene, and xylenes (BTEX) concentrations were determined in the contaminated fields located in Pohang and Chuncheon city, Korea. In the experimental site located in Pohang, the concentrations of TPH ranged from 873 to 3819mg kg-1, while BTEX was not detected in the soil samples. In the experimental site located in Chuncheon city, TPH and BTEX concentrations ranged from 2920 to 7704mg kg-1 and from 220 to 1727mg kg-1, respectively. The levels of TPH were higher than the safe levels in both experimental sites. However BTEX levels in experimental sites were different in its hazardous level. BTEX concentration was hazardous in only the site located in Chuncheon. Weed flora in contaminated fields was different from the uncontaminated fields. Dominant weed species in petroleum contaminated soil of Pohang was Zoysia japonica, and those of the contaminated field in Chuncheon were Bidens frondosa and Microstegium vimineum. Compared with uncomtaminated site, vegetational characteristic of petroleum contaminated soil showed higher dominance index and lower diversity index than uncontaminated fields located nearby oil-contaminated sites. Distributions of weed species according to life cycle indicated that the proportions of annual plants were lowered in both contamination sites while those of perennials were increased. Proportion of annual plants in the flora of contaminated sites located in Pohang and Chuncheon were 16.7 and 38.5%, respectively, which were lower than those of uncontaminated sites (34.4 and 42.9%, respectively). The proportions of biennial in contaminated sites were slightly increased from 9.4 to 16.7 and 14.3 to 15.4 in Pohang and Chuncheon, respectively. Proportional similarity between vegetation of contaminated and uncontaminated site in Pohang and Chuncheon city was 24.3 and 4.4%, respectively.