Joint Toxicity And Mechanisms Of Typical PPCPs And Cd In Soil

In this paper, the acute toxic effects of typical polycyclic musks (HHCB and AHTN) and cadimum (Cd) on seed germination and root and shoot elongation on wheat(Triticum aestivum), and the responses of T. aestivum at biochemical and physiological levels such as chlorophyll (CHL), malondialdehyde (MDA), superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were investigated. In order to better understand toxicolgical mechanisms of polycyclic musks and Cd, accumulation of HHCB and Cd in wheat and effects of heavy metals on sorption and desorption of HHCB in soils were investigated.The results showed that there was a good dose-effect relationship between polycyclic musks (Cd) and inhibitory rates of root and shoot elongation. According to the EC50 values, the sensitivities of seed germination, root and shoot elongation to polycyclic musks were different to Cd. The EC50 values of HHCB-Cd and AHTN-Cd were 0.530 TUmix and 0.614 TUmix, respectively, which were significantly higher than 1 TUmix, thus the joint stress of HHCB-Cd and AHTN-Cd had synergistic effects on T. aestivum when root elongation was selected as the toxicological endpoint.In single HHCB stress, contents of CHL showed a biphasic response to HHCB that is characterized by low-dose stimulation, or a beneficial effect, and a high dose inhibitory or toxic effect after 7-day exposure. After 14 and 21 days of exposure, contents of CHL decreased with the increasing concentration of HHCB. The change of MDA in leaves and roots was different. In leaves, MDA increased with the increasing concentration of HHCB, but the MDA content in root was inhibited by high concentration of HHCB. The antioxidative defense system in wheat had ability to protect plant from oxidative stress, but it was destroyed by increasing concentration of HHCB and prolongation of exposure time.In joint stress of HHCB and Cd, contents of CHL decreased with increasing concentration of HHCB and were significantly lower than that in control and treatments with single Cd. In wheat leaves, contents of MDA were higher than that in single Cd treatments. In wheat roots, contents of MDA were significantly higher than that in single Cd treatment after 7 days of exposure under treatments with low concentration of Cd and HHCB. With prolongation of exposure time and increase of pollutants’concentration, contents of MDA decreased and were lower than that in treatments with single Cd. According to the change of CHL and MDA, it was indicated that the joint stress of HHCB and Cd could strengthen the oxidative stress. Besides, the joint stress of AHTN and Cd also could strengthen the oxidative stress.Accumulation of single HHCB in wheat root was more than that of stem and leaf. Due to the high lipophility of HHCB, it is easier to be accumulated in parts with high lipid. The accumulation of HHCB in wheat seedlings cultured in alluvial soil was higher than that in cinnamon soil, but the accumulation of Cd in alluvial soil was lower than that in cinnamon soil. With the combined pollution of HHCB and Cd, Cd in alluvial soil could induce the accumulation of HHCB in wheat roots significantly, but inhibit the accumulation of HHCB in wheat stems and leaves. However, Cd in cinnamon soil could induce the accumulation of HHCB in root without significant differences, and significantly induce the accumulation of HHCB in stem and leaf. In addition, HHCB could significantly induce the accumulation of Cd in wheat seedlings cultured in two different soils.Datas of sorption and desoiption of HHCB in soils were fitted well Freundlich model. The amounts of HHCB adsorded in soils followed the sequence that brown soil>alluvial soil>red soil. Cd inhibited the sorption of HHCB in soils, but Cu induced the sorption of HHCB. According to hysteresis coefficients, Cd inhibited desorption of HHCB but Cu promoted.