Xianzhe Xiong

Risk assessment of heavy metals in soil previously irrigated with industrial wastewater in Shenyang, China

The Zhangshi Irrigation Area (ZIA) in Shenyang, China has been irrigated by industrial wastewater since 1962. Since then, parts of the ZIA have been rezoned for industrial uses, but the remaining area, named Sluice Gate III (SLIII) and Lower Reaches (LR), still occupies 1825ha. Although land irrigation with industrial wastewater ceased in 1992, a study on heavy metals in soils was carried out to assess the feasibility of agricultural crop cultivation in SLIII and LR. A detailed field investigation was conducted and both total heavy metal concentrations and bioavailable fraction in soil were determined. The results have highlighted that Cd concentrations in soils still exceed the Environmental Quality Standard for Soil in China (GB15618-1995) grade C standard in SLIII region, and grade B standard in LR. In the SLIII, Zn and Pb concentrations in soil are higher than the grade A standard, although Cu is close the grade A standard. In SLIII the dominant chemical fractions were the exchangeable and carbonatic forms, which represent up to 43% and 35% of the Cd, respectively. The Cd in these two fractionations poses the highest risk for the plant absorption and accumulation. Therefore the SLIII should be abandoned for cultivated crops to prevent the Cd contamination of food chain and any associated hazards to human health.

Competitive sorption of metals in water repellent soils: Implications for irrigation recycled water

Australia is a water-stressed nation and demand on potable water supply is increasing. Consequently water conservation and reuse are increasingly becoming important. Irrigation of recycled wastewater on water repellent soils is a technology that is being trialled as a means of improving crop production and conserving potable supply. However, recycled water contains potentially harmful heavy metals. This paper reports the competitive sorption and desorption of several common heavy metals found in soils collected from a farm located in the south-east of South Australia. The soil from this location is severely water repellent, but some sites were amended with kaolinite clay (Si4Al4O10(OH)8) about 7 and 15 years ago. The metals studied were Cu, Pb, Cd, Cr, Ni, and Zn. Competitive sorption of the metals was distinctly observed. For all heavy metals, the quantity of metal sorbed was higher in amended soil, and there was a strong correlation between the specific sorption to total sorption ratio and the amount of clay in the soil. The sorption intensities varied with metal, Cr, Pb, and Cu having a high sorption tendencies and Zn, Cd, and Ni having comparatively low sorption tendencies. The total sorption capacity for all metals increased in clay-treated soils compared with non-treated soils. On average, clay-amended water repellent soils had a 20–40% increased capacity to adsorb total metals; however, this increase was largely caused by the increased capacities to adsorb Zn, Cd, and Ni. The effect of clay treatment largely enhanced the sorption capacity of relatively weakly adsorbing heavy metals. The implications for using recycled wastewater on the long-term sustainable agro-environmental management of these soils are discussed.

Studies on the sources of benzo[a]pyrene in grain and aboveground tissues of rice plants

Rice plant pot experiments designed to identify benzo[a]pyrene (B[a]P) sources in plant tissues were conducted in an air-quality controlled greenhouse built to prevent contamination from B[a]P air pollution. Results from quartz sand cultures with control and 50, 100 and 500 microgkg(-1) of B[a]P treatments were compared with those from outdoor field experiments, in which rice plants were exposed to polluted air in the urban area of Shenyang, China. When B[a]P was strictly controlled in both air and quartz sand culture medium, the background values of B[a]P in rice plant tissues were uniformly very low. There was no significant difference of B[a]P contents of rice grain between control and treatments of B[a]P in controlled air quality trials. This indicated that the source of B[a]P in the rice grains is not from any B[a]P in the root culture media. The B[a]P content of rice grain, husk, and stem with leaf sampled from outdoor field was up to 7.33-, 9.21- and 27.10-fold higher than corresponding tissues from air-quality controlled conditions. This indicated that polluted air is the main source of B[a]P in aboveground tissues. Therefore control of B[a]P pollution in ambient air is of prime importance for improving the quality of cereal crops.

Sorption and Fractionation of Copper in Soil at a Sewage Irrigation Farm in Australia

Abstract Copper (Cu) is an important heavy metal to be considered in soil contamination, because high concentrations of copper in soil produce toxic effects and may accumulate in plant tissues. In Australias oldest sewage irrigation farm, located in Werribee, Victoria, soil in the land filtration area is contaminated by Cu. However, Cu content in herbage tissues is in the normal range and has been trending downward since 1979. Therefore, studies on the sorption capacity and sequential extraction of Cu in soil at the Werribee Farm is of significance, not only for better understanding the mechanism of transport, chemical processes, and plant uptake of Cu, but also in providing information for the practical management of sewage farm soils. Methods of combining sorption isotherms with sequential extraction procedures were adopted, and the results showed that the soil in the land filtration area at Werribee Farm has a high sorption capacity for Cu, and distribution coefficients, Kf of Cu, were 629 L kg−1 in surface soils (0–20 cm) and 335 L kg−1 in subsurface soils (20–40 cm). The sequential extraction fractions demonstrate that exchangeable and carbonate fractions are very low, only comprising 3.49 to 5.49% of total copper. The other fractions are also discussed. This characteristic of Cu in soil is related to the low concentration of Cu in plant tissues.

Environmental quality: issues and causes of deterioration – A survey on environmental awareness among the public in Liaoning Province, China

A large-scale and comprehensive survey of public environmental awareness was carried out in Liaoning Province, China, where one of the largest heavy industrial bases is located. This survey was organized by the EU-CHINA Liaoning Integrated Environmental Program. The aim of the survey was to collect public information and awareness of environmental issues and therefore provide a valuable reference source for the government to formulate environmental policy. Statistical survey specialists and environmental protection experts worked together to establish survey items and questionnaires, and the design and survey were performed in strict accordance to the requirements of the project. The survey involved five large cities and 5996 respondents, representing residents, policy-makers, teachers, students, workers in enterprises, and farmers in suburban regions of the five cities. The evaluation of public opinion on current environmental issues and diversity among different survey groups were summarized statistically. The findings of the survey research are: the public is very concerned about air, water, and food pollution, improvement of the environment for community life and further global environmental changes. The survey also emphasized the need for better education to raise environmental awareness and the importance of public initiatives in environmental protection and management.

Distribution and migration of nitrobenzene in water following a simulated spill

Releases of nitrobenzene into the aquatic environment pose a threat to human health and aquatic resources, and have attracted much attention world-wide. In order to find out the distribution and migration patterns of pooled nitrobenzene underwater in different conditions, laboratory column experiments were designed to simulate stagnant water, flowing water and rainfall disturbance events. The results showed that in stagnant water there was a slow diffusion of the nitrobenzene from the pool leading to higher concentrations of the chemical deeper in the water column. In flowing water, the removal of the substance was rapid and water concentrations were much lower and more uniform throughout the column. The disturbance event brought a substantial quantity of nitrobenzene into the water column which then dissipated according to the flow regime. Analysis of the data showed that distribution pattern of nitrobenzene in the stagnant water column followed a logarithmic equation C(NB) = a ln(t) + b, and in disturbed flowing water, the distribution pattern of nitrobenzene followed a negative exponential regression equation C(NB) = Ne(-Mt). These conclusions have practical significance in developing remediation technologies for water polluted by nitrobenzene.