Seasonal variations in leaf capturing of particulate matter, surface wettability and micromorphology in urban tree species

The seasonal changes in leaf particulate matter (PM) accumulation, surface wettability and micromorphology in urban tree species, including Sophora japonica (S. japonica), Platanus acerifolia (P. acerifolia) and Cedrus deodara (C. deodara), were studied during a single growing season. The three species showed distinct seasonal trends in PM accumulation, increasing from spring to autumn (or winter) even during the rainy season, but at different rates. During the study, the leaf PM retention amount of P. acerifolia, a species with ridged leaf surfaces, was significantly higher than that of S. japonica and C. deodara, species with waxy leaf surfaces. The contact angles of water droplets on leaves decreased with leaf age except on the abaxial surface of S. japonica, which remained non-wettable or highly non-wettable throughout the growing season; the decrease in the contact angle on adaxial surface of S. japonica was greater when compared with P. acerifolia and C. deodara. A significant and negative relationship existed between leaf PM retention amounts and contact angles on adaxial surface of leaves of all three species. The increase in wettability, probably caused when epicuticular wax was destroyed by mechanical and chemical abrasion, seemed to be the main factor leading to seasonal variations in leaf PM accumulation.     

毒气泄漏扩散风险的参数不确定性分析

有毒气体泄漏扩散受很多不确定性因素的影响,为了分析和评估影响毒气泄漏扩散的风速和泄漏速率的变化和不确定性,采用蒙特卡罗模拟和基于Wilks公式容许限的非参数统计法,通过抽样计算得到“95/95准则”下的毒气泄漏扩散地面浓度分布,计算了有毒气体泄漏扩散的不同风险等级的影响范围和风险概率曲线。以氨气泄漏事故为例进行实例分析,结果表明,相对于以确定性参数得出的氨气泄漏扩散浓度分布,引入参数的不确定性评估,更能贴合泄漏现场存在不确定性因素的实际情况,更有利于人员的安全和应急疏散管理。     

Optimized production of a novel bioflocculant M-C11 by Klebsiella sp. and its application in sludge dewatering

The optimized production of a novel bioflocculant M-C11 produced by Klebsiella sp. and its application in sludge dewatering were investigated. The optimal medium carbon source,nitrogen source, metal ion, initial pH and culture temperature for the bioflocculant production were glucose, NaNO3, MgSO4, and pH 7.0 and 25°C, respectively. A compositional analysis indicated that the purified M-C11 consisted of 91.2% sugar, 4.6% protein and 3.9% nucleic acids（m/m）. A Fourier transform infrared spectrum confirmed the presence of carboxyl, hydroxyl,methoxyl and amino groups. The microbial flocculant exhibited excellent pH and thermal stability in a kaolin suspension over a pH range of 4.0 to 8.0 and a temperature range of 20 to 60°C.The optimum bioflocculating activity was observed as 92.37% for 2.56 mL M-C11 and 0.37 g/L CaCl2 dosages using response surface methodology. The sludge resistance in filtration（SRF）decreased from 11.6 × 1012 to 4.7 × 1012m/kg, which indicated that the sludge dewaterability was remarkably enhanced by the bioflocculant conditioning. The sludge dewatering performance conditioned by M-C11 was more efficient than that of inorganic flocculating reagents,such as aluminum sulfate and polymeric aluminum chloride. The bioflocculant has advantages over traditional sludge conditioners due to its lower cost, benign biodegradability and negligible secondary pollution. In addition, the bioflocculant was favorably adapted to the specific sludge pH and salinity.     

Removal of ammonium ion from water by Na-rich birnessite: Performance and mechanisms

Na-rich birnessite (NRB) was synthesized by a simple synthesis method and used as a high-efficiency adsorbent for the removal of ammonium ion (NH₄⁺) from aqueous solution. In order to demonstrate the adsorption performance of the synthesized material, the effects of contact time, pH, initial ammonium ion concentration, and temperature were investigated. Adsorption kinetics showed that the adsorption behavior followed the pseudo second-order kinetic model. The equilibrium adsorption data were fitted to Langmuir and Freundlich adsorption models and the model parameters were evaluated. The monolayer adsorption capacity of the adsorbent, as obtained from the Langmuir isotherm, was 22.61 mg NH₄⁺-N/g at 283 K. Thermodynamic analyses showed that the adsorption was spontaneous and that it was also a physisorption process. Our data revealed that the higher NH₄⁺ adsorption capacity could be primarily attributed to the water absorption process and electrostatic interaction. Particularly, the high surface hydroxyl-content of NRB enables strong interactions with ammonium ion. The results obtained in this study illustrate that the NRB is expected to be an effective and economically viable adsorbent for ammonium ion removal from aqueous system.     

Characterization of polycyclic aromatic hydrocarbons and gas/particle partitioning in a coastal city, Xiamen, Southeast China

An intensive sampling program had been undertaken in autumn (October, 2008) and winter (December, 2008 and January, 2009) at urban (Xiamen University and Xianyue residential area), suburban (Institute of Urban Environment), industrial area (Lulian Hotel) and background (Tingxi Reservoir) in Xiamen, Fujian Province, to characterize the atmospheric concentration and gas-particle phase partitioning of PAHs. The average concentration of total PAHs in winter was almost 1.7 times higher than those in autumn. The log scale plot of Kp versus sub-cooled liquid vapor pressure (P0 L) for all the data of autumn and winter season samples gave significantly di erent slopes. The slope for the winter samples (–0.72) was steeper than that for the autumn samples (–0.58). The partitioning results indicated that slope values varied depending on characteristics of specific site, source region and meteorological conditions which play important roles in the partitioning of PAHs. In addition, local emission sources had a stronger e ect on partitioning results than long-transported polluted plume. The sources of PAHs in five sampling sites in Xiamen also have been discussed initially. Diagnostic ratios showed that the primary source of PAHs in urban, suburban and industrial area was from vehicle exhausts. While emission from petrochemical factory and power plant was another main contributor to industrial area.