Evaluation of the community multiscale air quality (CMAQ) model version 4.5: Sensitivities impacting model performance; Part II—particulate matter

This paper is Part II in a pair of papers that examines the results of the Community Multiscale Air Quality (CMAQ) model version 4.5 (v4.5) and discusses the potential explanations for the model performance characteristics seen. The focus of this paper is on fine particulate matter (PM_2.5) and its chemical composition. Improvements made to the dry deposition velocity and cloud treatment in CMAQ v4.5 addressing compensating errors in 36-km simulations improved particulate sulfate (SO₄²⁻) predictions. Large overpredictions of particulate nitrate (NO₃⁻) and ammonium (NH₄⁺) in the fall are likely due to a gross overestimation of seasonal ammonia (NH₃) emissions. Carbonaceous aerosol concentrations are substantially underpredicted during the late spring and summer months, most likely due, in part, to a lack of some secondary organic aerosol (SOA) formation pathways in the model. Comparisons of CMAQ PM_2.5 predictions with observed PM_2.5 mass show mixed seasonal performance. Spring and summer show the best overall performance, while performance in the winter and fall is relatively poor, with significant overpredictions of total PM_2.5 mass in those seasons. The model biases in PM_2.5 mass cannot be explained by summing the model biases for the major inorganic ions plus carbon. Errors in the prediction of other unspeciated PM_2.5 (PM_Other) are largely to blame for the errors in total PM_2.5 mass predictions, and efforts are underway to identify the cause of these errors.     

Probing the potential of polyester for CO2 capture

Global warming, the major environmental issue confronted by humanity today, is caused by rising level of green house gases. Carbon capture and storage technologies offer potential for tapering CO2 emission in the atmosphere. Adsorption is believed to be a promising technology for CO2 capture. For this purpose, a polyester was synthesized by polycondensation of1,3,5-benzenetricarbonyl trichloride and cyanuric acid in pyridine and dichloromethane mixture. The polymer was then characterized using FT-IR, TGA, BET surface area and pore size analysis, FESEM and CO2 adsorption measurements. The CO2 adsorption capacities of the polyester were evaluated at a pressure of 1 bar and two different temperatures（273 and 298 K）.The performance of these materials to adsorb CO2 at atmospheric pressure was measured by optimum CO2 uptake of 0.244 mmol/g at 273 K. The synthesized polyester, therefore, has the potential to be exploited as CO2 adsorbent in pre-combustion capture process.     

Monitoring the drastic growth of ship breaking yards in Sitakunda: a threat to the coastal environment of Bangladesh

The vast coastal and marine resources that occur along the southern edge of Bangladesh make it one of the most productive areas of the world. However, due to growing anthropogenic impacts, this area is under considerable environmental pressure from both physical and chemical stress factors. Ship breaking, or the dismantling and demolition of out-of-service ocean-going vessels, has become increasingly common in many coastal areas. To investigate the extent of ship breaking activities in Bangladesh along the Sitakunda coast, various spatial and non-spatial data were obtained, including remote sensing imagery, statistical records and published reports. Impacts to coastal and marine life were documented. Available data show that ship breaking activities cause significant physical disturbance and release toxic materials into the environment, resulting in adverse effects to numerous marine taxonomic groups such as fish, mammals, birds, reptiles, plants, phytoplankton, zooplankton and benthic invertebrates. Landsat imagery illustrates that the negatively impacted coastal area has grown 308.7 % from 367 ha in 1989 to 1,133 ha in 2010. Physicochemical and biological properties of coastal soil and water indicate substantially elevated pollution that poses a risk of local, regional and even global contamination through sea water and atmospheric transport. While damage to the coastal environment of Bangladesh is a recognized hazard that must be addressed, the economic benefits of ship breaking through job creation and fulfilling the domestic demand for recycled steel must be considered. Rather than an outright ban on beach breaking of ships, the enterprise must be recognized as a true and influential industry that should be held responsible for developing an economically viable and environmentally proactive growth strategy. Evolution of the industry toward a sustainable system can be aided through reasonable and enforceable legislative and judicial action that takes a balanced approach, but does not diminish the value of coastal conservation.     

平寨水库荧光溶解性有机质的来源、特征及其动态转化

利用三维激发发射矩阵光谱(3-D EEM)和平行因子分析,研究了三岔河流域平寨水库溶解有机质的来源、组成和转化情况。在平寨水库的入库水、表层水(0～5 m)、深层水(10～60 m)和出库水中,检测到了几种荧光溶解有机质组分,分别为陆源类腐殖质、自源类腐殖质和浮游植物源的类蛋白质(或类色氨酸或类酪氨酸)。陆源类腐殖质的荧光强度在入库水中略高于出库水,表明陆源类腐殖质在水库系统中相对稳定,大坝截流对其影响不大。自源类腐殖质的荧光强度在库区明显高于入库水和出库水,表明自源类腐殖质既由自源有机物分解产生,又在光化学、微生物和大坝物理拦截过程的影响下发生分解;其他荧光组分中也检测到相似的结果。水温、pH、溶解氧和有色溶解有机质表现出相似的季节变化,光化学和微生物以及大坝拦截是引起水库入库水、库区表层水、库区深层水和出库水中荧光溶解有机质时空动态变化的主要原因。