Effects of biochar and crop straws on the bioavailability of cadmium in contaminated soil.

Numerous studies have been investigated the potential of biochar (BC) derived from various materials and crop straw (CS) to decrease the bioavailability of heavy metals in soil contaminated with cadmium (Cd), and thereby reduce their potential risk to human health and the ecological environment. However, little attention has been given to the comparison of heavy metal remediation efficiency using BC and CS such as peanut vine (PV) and rice straw (RS), especially in soil contaminated with Cd. Here, we explore if Cd bioavailability is affected in contaminated soil by BC and CS. Peanuts were grown in plastic pots, which contained BC or CS at 5% (dry weight, w/w) in controlled environment mesocosms. The bioavailability of Cd in contaminated soil was measured by Cd concentration in the plant and the concentrations of various forms of Cd in the soil. At the same plant age, growth with BC (compared with PV and RS) led to 13.56% and 8.28% lower rates of Cd content in the aboveground parts, 40.65% and 35.67% lower rates of Cd content in the seeds, yet 9.08% and 7.09% lower rates of Cd content in the roots, yet 35.80% and 28.48% lower rates of exchangeable Cd content in the soil. Moreover, BC amendment enhanced the biomass of peanut and physiological quality. Thus, BC had a greater impact on immobilizing Cd in the soil. The results imply that BC was more significantly (P < 0.05) remarkable in decreasing the Cd bioavailability and improving the biomass of peanut. BC has greater potential for enhancing soil quality and promoting peanut growth. In conclusion, this research demonstrates an understanding of employing BC as a promising inexpensive and eco-friendly amendment to remediate soil contaminated with Cd.

Varietal differences in the growth of rice seedlings exposed to perchlorate and their antioxidative defense mechanisms.

A hydroponic experiment was conducted to investigate perchlorate (ClO4 (-) ) phytotoxicity in different rice varieties. Considerable variations were observed when 24 rice varieties were treated with ClO4 (-) . The shoot height, root length, and biomass of most varieties were significantly reduced by ClO4 (-) . The roots were more sensitive than the shoots. Hierarchical clustering analysis demonstrated primarily 4 groups: ClO4 (-) -sensitive, medium ClO4 (-) -sensitive, medium ClO4 (-) tolerant, and ClO4 (-) -tolerant. Gannuoxiang (a ClO4 (-) -tolerant variety) and IR65598-112-2 (a ClO4 (-) -sensitive variety) were chosen to explore their antioxidant response when exposed to 0.2 mmol/L, 2.0 mmol/L, and 4.0 mmol/L ClO4 (-) . The results showed that the activities of superoxide dismutase and catalase increased in the shoots and roots of gannuoxiang with increasing doses of ClO4 (-) , but both of them decreased at higher concentrations of ClO4 (-) in IR65598-112-2. The addition of ClO4 (-) led to a significant increase in peroxidase activities for both of the varieties, whereas the increase was more pronounced in gannuoxiang than in IR65598-112-2. No significant difference was found in malondialdehyde (MDA) contents in gannuoxiang, whereas the addition of ClO4 (-) increased the MDA level significantly in IR65598-112-2. The results indicated that gannuoxiang has higher activities of antioxidant enzymes than IR65598-112-2 to cope with oxidative damage caused by ClO4 (-) stress, which may be the main cause of its high tolerance.

[Distribution and migration of zinc in Avicennia marina plant-soil system].

Zinc is a major anthropogenic contaminant in estuarine ecosystem, and has potential ecotoxicological consequences for aquatic animals and plants. An artificial mangrove wetland was set up in greenhouse to study the distribution and migration of zinc in synthetic wastewater in Avicennia marina plant-soil system. Different concentration synthetic wastewater and 1.5% salinity artificial seawater (control) were discharged into the system in fixed quantity twice a week for a year. The results showed that most part (> 67%) of zinc in the artificial wastewater discharged into the system was remained in the soil, and only a small portion (1.24%-10.4%) of it was entered into plant and litter, indicating that this artificial plant-soil system had a stronger purifying effect on the zinc in synthetic wastewater. The calculation with matter balance model indicated that soil subsystem had a higher environmental capacity of bearing zinc.