Placement of a microbial active sand cap on a coal tar-contaminated river sediment has been suggested as a cost effective remediation strategy. This approach assumes that the flux of contaminants from the sediment is sufficiently balanced by oxygen and nutrient fluxes into the sand layer such that microbial activity will reduce contaminant concentrations within the new benthic zone and reduce the contaminant flux to the water column. The dynamics of such a system were evaluated using batch and column studies with microbial communities from tar-contaminated sediment under different aeration and nutrient inputs. In a 30-d batch degradation study on aqueous extracts of coal tar sediment, oxygen and nutrient concentrations were found to be key parameters controlling the degradation rates of polycyclic aromatic hydrocarbons (PAHs). For the five PAHs monitored (naphthalene, fluorene, phenanthrene, anthracene, and pyrene), degradation rates were inversely proportional to molecular size. For the column studies, where three columns were packed with a 20-cm sand layer on the top of a 5 cm of sediment layer, flow was established to sand layers with (1) aerated water, (2) N(2) sparged water, or (3) HgCl(2)-sterilized N(2) sparged water. After steady-state conditions, PAH concentrations in effluents were the lowest in the aerated column, except for pyrene, whose concentration was invariant with all effluents. These laboratory scale studies support that if sufficient aeration can be achieved in the field through either active and passive means, the resulting microbially active sand layer can improve the water quality of the benthic zone and reduce the flux of many, but not all, PAHs to the water column. 相似文献
Hunting is a threat to wildlife within the Hkakaborazi National Park in north Myanmar. We used questionnaire surveys to obtain
data on variables such as commonly targeted species, prices of traded wildlife, reasons for hunting and the relative importance
of livelihood sources. We examine (a) the significance of hunting and trade for livelihoods and explore (b) the impacts of
hunting on targeted species. Ninety per cent of trade records (n = 803) was constituted by seven species commonly targeted by hunters (serow, red goral, muntjac, bear, Assamese macaque,
black musk deer and takin). Commercially valuable species previously targeted by hunters (tiger, otter, pangolin) appear to
be completely absent from current harvest records and potentially in decline. Although farming is the predominant occupation,
hunting (driven by trade) represents a significantly higher source of income than other livelihood activities. Management
recommendations include increased investment in enforcement, education and outreach, small livestock development, improved
crop productivity, demarcation of no-take areas for wildlife and biological monitoring of targeted species. 相似文献
Wastewater treatment plants (WWTP) are highly non-linear operations concerned with huge disturbances in flow rate and concentration of pollutants with uncertainties in the composition of influent wastewater. In this work, the activated sludge process model with seven reactor configuration in the ASM3bioP framework is used to achieve simultaneous removal of nitrogen and phosphorus. A total of 8 control approaches are designed and implemented in the advanced simulation framework for assessment of the performance. The performance of the WWTP (effluent quality index and global plant performance) and the operational costs are also evaluated to compare the control approaches. Additionally, this paper reports a comparison among proportional integral (PI) control, fuzzy logic control, and model-based predictive control (MPC) configurations framework. The simulation outcomes indicated that all three control approaches were able to enhance the performance of WWTP when compared with open loop operation.
Environmental Science and Pollution Research - Biodiesel is a renewable, clean-burning diesel replacement that can be used in existing diesel engines without modification. Biodiesel is among the... 相似文献
Environmental Science and Pollution Research - Toxic contaminants (metals and metal-containing compounds) are accumulating in the environment at an astonishing rate and jeopardize human health.... 相似文献
Environmental Science and Pollution Research - The inactivation of bacteriophage MS2 under irradiation above 320 nm was investigated, focusing on different solution pH, ionic strength, and... 相似文献
Air quality data often contain several observations reported only as below the analytical limit of detection (LOD), resulting in “censored” data sets. Such censored and/or truncated data sets tend to complicate statistical analysis. This paper discusses various procedures for estimating mean concentration and Its 95 percent confidence bounds from air contaminant data sets which contain values that are reported as below the LOD, A quantitative approach for assessing the uncertainty Inherent In the estimated mean concentration due to (a) presence of values below the LOD In the data set, and (b) natural variability of atmospheric concentration data, is described. The utility of this approach In the analysis and interpretation of ambient pollutant concentration data Is demonstrated for both hypothetical and observed singly-censored data sets, and for a multiply-censored, multi-pollutant observed concentration data set. The methodologies discussed here should be particularly useful In verifying compliance with environmental regulations, and In estimating the risks associated with long-term exposure of populations to toxic air contaminants and assessing the uncertainty associated with these estimates. 相似文献