Ecological Behavior of Linear Alkylbenzene Sulfonate (LAS) in Soil-Plant Systems

More and more linear alkylbenzene sulfonate (LAS) has contaminated the water and soil via pollution discharge,making it important to identify the ecological behavior and toxicity of LAS so as to carry out measures that will reduce its negative effects on the ecosystem. The ecological behavior of LAS, including degradation, migration, and plant uptake,in both soil-paddy rice and soil-soybean systems was studied. Reduction of LAS in pot and field plots followed the first order reaction kinetics with degradation half-lives of 35-50 days with LAS decreasing to very low concentrations after a season of crop growth. Strong migration ability for LAS was found and the breakthrough time in a 1.5 m soil monolith was significantly shortened to 23 days by preferential flow. Leachate volumes of soil-paddy and soil-soybean systems at preferential breakthrough were much different, while the leachate volumes at equilibrium governed by soil adsorption/desorption processes were very similar. Significant uptake of LAS in both paddy rice and soybeans was observed in pot and field experiments (P ＜ 0.05). In aquatic culture, 20 μg mL-1 and above of LAS significantly inhibited the growth of paddy seedlings (P ＜ 0.05). The critical concentration for LAS in soil inhibiting the growth and yield of paddy was 160 μg g-1; when higher, there was a strong negative influence, with decreases in height, spike length,and production; when lower than 80 μg g-1, paddy growth was stimulated. There was little effect of LAS on soybeans.

Scenario simulation of water security in China

Limited water resources, increasing demand, low use efficiency, and serious pollution result in severe water resource difficult in China. The evaluation of addressing water problems and the search for effective countermeasures that ensure sustainable water use are key to China's sustainable development. The “compound water security” consists of food security, life security, environmental security, and economic security. By establishing a conceptual model, the water security of China has been simulated in terms of four scenarios called BAU(the business-as-usual scenario), TEC(the technology and economics scenario), IVL(the institution, values, and lifestyles scenario) and TSD(toward sustainable development) in this paper. The results indicated that water crises, especially water shortages, are being experienced now and will continue to do so for a relatively long time in China and that it is possible to reach a basic balance between supply and demand of water and grain under the TSD developing pattern by a series of approaches including technological innovation, policy adjustments, and behaviour inducement.

Simulation of temporal and spatial change of N_2O emissions in the Yangtze River Delta

A biogeochemical model(DNDC) is combined with a plant ecological model to estimate N_2O emission from rice paddy fields in the Yangtze River Delta region. The model is driven by local meteorological, soil, and physiological data and is validated for 1999 and 2000 at a site in the region, which showed that the simulated N_2O emissions agree fairly well with the observed data. This adds some confidence in the estimated N_2O emissions during 1950 and 2000 in the Hangzhou Region. A significant correlation between the N_2O emissions and the population for the Hangzhou Region is found, which is due to a combination of increased application of fertilizers and cultivated area. Such a correlation can not be established for the whole Yangtze River Delta region when the data of both urban and rural areas are included. However, when the data from the heavily urbanized areas are excluded, a significant correlation between population and N_2O emissions emerges. The results show clearly that both the temporal and the spatial N_2O emissions have significant positive relationship with population under traditional farming practice. These results have implications for suitable mitigation options towards a sustainable agriculture and environment in this region.