Eco-toxicological Effects of Phenanthrene, Pyrene and 1,2,4-Trichlorobenzene in Soils on the Inhibition of Root Elongation of Higher Plants
菲、芘、1,2,4-三氯苯对土壤高等植物根伸长抑制的生态毒性效应

Ecological bioassays using higher plants were included in a test battery because vegetation is the dominant biological component of terrestrial ecosystem, and they could reflect the toxicity of hazardous chemicals in soils, therefore providing an alternative method for the evaluation of toxic effects such as adverse effects of a bioavailable fraction of pollutants in a complex soil matrix. It is well known that a reduction in toxicity of a complex mixture could not be measured by parent compound disappearance. In addition, bioassays could compensate expenses of chemical analyze and its difficulties in detecting the total amount of bioavailable toxicants due to the lower concentration, lower solubility or insolubility in chemical extracting. Seed germination test adopted in the OECD guideline suggested two indexes as the endpoints (seed germination and root elongation). The main advantage of the seed germination test as an additional endpoint is the possibility of giving a more fast and cost\|effective results based on them, which can be very useful for several applications including identification of phytotoxicity threshold of target pollutants, evaluating contaminated soils and bioremediation sites. Available reports are most based on the early growth stage as the endpoint with recommended species for toxicity test by the US EPA and OECD and ISO to evaluate the toxicity of the toxicants, only a few concerned with seed germination test using root elongation as the endpoint. Since toxicity can be specific to plant species, it is thus important to use a variety of species from different families for each evaluation. Polycyclic aromatic hydrocarbons (PAHs) and organic chlorides are two groups of priority pollutants listed in US EPA and were well known to be toxic, carcinogenic and mutagenic to a wide range of organisms, whereas less is known of the phytotoxicity threshold of these pollutants. The sensitivity of plants to the PAHs and organic chlorides and tolerance responses of different plant species to them was unknown.Individual and combined responses of phenanthrene, pyrene, 1,2,4\|trichlorobenzene and the extent of combined toxicity effects were compared by determination of the inhibition rates of phenanthrene, pyrene and 1,2,4\|trichlorobenzene on higher plants (wheat, Chinese cabbages and tomatoes) and toxic effects of combined pollution of these chemicals in the meadow brown soils. The root elongation was used as endpoint. Results indicated that there was a significant liner or logarithmic relationship between the concentration of phenanthrene, pyrene and 1,2,4\|trichlorobenzene and the inhibition rates of root elongation of plants ( p =0 05). Inhibition strength of three chemicals on plant elongation was in the sequence: 1,2,4\|trichlorobenzene>phenanthrene>pyrene, which was closely related with the water solubility of the chemicals tested. Wheat was the most sensible plant to the organic pollutants. There was a synergism of phenanthrene, p