国家自主贡献机制下的减排力度调控机制设计

现有国家自主贡献机制存在约束力弱、减排力度小的问题,对此,本文在论证该机制内在缺陷的基础上,基于信息不对称理论的委托代理模型设计了减排力度调控机制。该减排力度调控机制既能使各国的自主贡献额具有强约束力,又能灵活调控各国的减排力度,并发掘各国的减排潜力。该减排力度调控机制有助于弥补现有国家自主贡献机制的缺陷,促进国际社会的减排。     

典型类雌激素的降解方法及其影响因素研究进展

类雌激素是一类新兴污染物,目前在环境中普遍存在,且在极低浓度下可对生物体和环境产生重大威胁.本文重点介绍了酚类、天然类固醇类和邻苯二甲酸酯等3种典型类雌激素的来源、环境分布特征及其生物毒性,综述了典型类雌激素的最新化学降解法(直接光解法和高级氧化法)和生物降解法(菌类降解法和藻类降解法)及其特点.直接光解法操作简便,但降解效果不佳;高级氧化法能快速高效地去除类雌激素,但操作相对复杂、影响因素较多;生物降解法的应用性强,但处理周期长、受环境因素影响大.此外还阐述了类雌激素的降解机理及其影响因素,最后对典型类雌激素的多种高效联合降解技术提出了展望.     

Stratification effects on hydrodynamics and mixing at a river confluence with discordant bed

Environmental Fluid Mechanics - Stratification effects induced by density differences between the incoming flows are investigated at a medium-size stream confluence with a highly discordant bed....     

Utilization of MSWI fly ash as partial cement or sand substitute with focus on cementing efficiency and health risk assessment

• Washed MSWI fly ash was used as partial cement or sand substitute. • Sand replacing is beneficial for strength, while cement replacement reduces strength. • Cementing efficiency factor and mortar pore structure explain the strength results. • Health risk assessment was conducted for MSWI fly ash blended cement mortar. • CR and HI contributed by different exposures and heavy metals were analyzed. The strength of cement substituted mortar decreases with the increase in fly ash amount, whereas the strength increases when the fly ash is blended as sand substitute. A mortar with highest strength (compressive strength= 30.2 Mpa; flexural strength= 7.0 Mpa) was obtained when the sand replacement ratio was 0.75%. The k value (cementing efficiency) of fly ash varied between 0.36 and 0.15 for the fly ash fraction in binder between 5% and 25%. The k values of fly ash used for sand replacement were all significantly above that used for cement substitution. The macropores assigned to the gaps between particles decreased when the fly ash was used as sand replacement, providing an explanation for the strength enhancement. The waste-extraction procedure (toxicity-sulphuric acid and nitric acid method (HJ/T 299-2007)) was used to evaluate metal leaching, indicating the reuse possibility of fly ash blended mortar. For the mortar with the mass ratio of fly ash to binder of 0.5%, the carcinogenic risks (CR) and non-carcinogenic hazard quotient (HQ) in sensitive scenario for blended mortar utilization were 9.66 × 10^-7 and 0.06, respectively; these results were both lower than the threshold values, showing an acceptable health risk. The CR (9.89 × 10^-5) and HQ (3.89) of the non-sensitive scenario for fly ash treatment exceeded the acceptable threshold values, indicating health risks to onsite workers. The main contributor to the carcinogenic and non-carcinogenic risk is Cr and Cd, respectively. The CR and HQ from inhalation was the main route of heavy metal exposure.     

Biogenic palladium prepared by activated sludge microbes for the hexavalent chromium catalytic reduction: Impact of relative biomass

• Pd nanoparticles could be reduced and supported by activated sludge microbes. • The effect of biomass on Pd adsorption by microbes is greater than Pd reduction. • More biomass reduces Pd particle size, which is more dispersed on the cell surface. • When the biomass/Pd add to 6, the catalytic reduction rate of Cr(VI) reaches stable. Palladium, a kind of platinum group metal, owns catalytic capacity for a variety of hydrogenations. In this study, Pd nanoparticles (PdNPs) were generated through enzymatic recovery by microbes of activated sludge at various biomass/Pd, and further used for the Cr(VI) reduction. The results show that biomass had a strong adsorption capacity for Pd(II), which was 17.25 mg Pd/g sludge. The XRD and TEM-EDX results confirmed the existence of PdNPs associated with microbes (bio-Pd). The increase of biomass had little effect on the reduction rate of Pd(II), but it could cause decreasing particle size and shifting location of Pd(0) with the better dispersion degree on the cell surface. In the Cr(VI) reduction experiments, Cr(VI) was first adsorbed on bio-Pd with hydrogen and then reduced using active hydrogen as electron donor. Biomass improved the catalytic activity of PdNPs. When the biomass/Pd (w/w) ratio increased to six or higher, Cr(VI) reduction achieved maximum rate that 50 mg/L of Cr(VI) could be rapidly reduced in one minute.     

Taxonomic and functional variations in the microbial community during the upgrade process of a full-scale landfill leachate treatment plant – from conventional to partial nitrification-denitrification

• Upgrade process was investigated in a full-scale landfill leachate treatment plant. • The optimization of DO can technically achieve the shift from CND to PND process. • Nitrosomonas was mainly responsible for ammonium oxidation in PND system. • An obviously enrichment of Thauera was found in the PND process. • Enhanced metabolic potentials on organics was found during the process update. Because of the low access to biodegradable organic substances used for denitrification, the partial nitrification-denitrification process has been considered as a low-cost, sustainable alternative for landfill leachate treatment. In this study, the process upgrade from conventional to partial nitrification-denitrification was comprehensively investigated in a full-scale landfill leachate treatment plant (LLTP). The partial nitrification-denitrification system was successfully achieved through the optimizing dissolved oxygen and the external carbon source, with effluent nitrogen concentrations lower than 150 mg/L. Moreover, the upgrading process facilitated the enrichment of Nitrosomonas (abundance increased from 0.4% to 3.3%), which was also evidenced by increased abundance of amoA/B/C genes carried by Nitrosomonas. Although Nitrospira (accounting for 0.1%–0.6%) was found to stably exist in the reactor tank, considerable nitrite accumulation occurred in the reactor (reaching 98.8 mg/L), indicating high-efficiency of the partial nitrification process. Moreover, the abundance of Thauera, the dominant denitrifying bacteria responsible for nitrite reduction, gradually increased from 0.60% to 5.52% during the upgrade process. This process caused great changes in the microbial community, inducing continuous succession of heterotrophic bacteria accompanied by enhanced metabolic potentials toward organic substances. The results obtained in this study advanced our understanding of the operation of a partial nitrification-denitrification system and provided a technical case for the upgrade of currently existing full-scale LLTPs.     

A review of measurement methods for peracetic acid (PAA)

• Physical and chemical properties and application of peracetic acid solution. • Determination method of high concentration peracetic acid. • Determination method of residual peracetic acid (low concentration). Peroxyacetic acid has been widely used in food, medical, and synthetic chemical fields for the past several decades. Recently, peroxyacetic acid has gradually become an effective alternative disinfectant in wastewater disinfection and has strong redox capacity for removing micro-pollutants from drinking water. However, commercial peroxyacetic acid solutions are primarily multi-component mixtures of peroxyacetic acid, acetic acid, hydrogen peroxide, and water. During the process of water treatment, peroxyacetic acid and hydrogen peroxide (H₂O₂) often coexist, which limits further investigation on the properties of peroxyacetic acid. Therefore, analytical methods need to achieve a certain level of selectivity, particularly when peroxyacetic acid and hydrogen peroxide coexist. This review summarizes the measurement and detection methods of peroxyacetic acid, comparing the principle, adaptability, and relative merits of these methods.     

Compartmentation and effects of lead (Pb) in the collembolan,Folsomia candida

Environmental Science and Pollution Research - The impact of soil lead (Pb) pollution on survival, growth, and reproduction of the collembolan, Folsomia candida, and Pb compartmentation in its gut...     

A novel sigma coordinate system to simulate abrupt changes of underwater terrain in a hydrodynamic model: application to Lake Mead,USA

The sigma (SIG) coordinate system in ocean circulation simulation models results inevitably in horizontal pressure gradient error. This problem also emerges in models of deep lakes or reservoirs with the same characteristics of underwater terrain mutation. SIG coordinates reflect vertical relative stratification but cannot be used to calculate horizontal pressure gradient force in places with drastic topographic changes; this results in vertical water temperature and circulation errors. In deep lakes or reservoirs, differences in water density caused by the temperature difference between upper and lower water bodies is the primary cause of thermal stratification phenomena. Lake Mead was used as a case study on steep topography based on Environmental Fluid Dynamics Code (EFDC) model in this study. SIG coordinates result in close agreement between the calibrated temperature time series at the top and middle water layers, but disparity in the bottom water layer. The error emerges in the horizontal pressure gradient error due to the SIG coordinate transformation. Neither increasing the vertical resolution nor adjusting the horizontal viscosity coefficient resolve this error. We test the sigma-zed (SGZ) coordinate which combines Z coordinate and SIG coordinate as a replacement for the SIG coordinate to find that they effectively reduce the model’s runtime and simulation efficiency. The vertical temperature distribution in SGZ coordinate mode is more accurate than the distribution in SIG coordinate mode. The Navier-Stokes horizontal gradient and advection diffusion equation results under SIG coordinates are very sensitive to the pressure gradient. The replacement also enhances resolution near the thermocline, facilitates reclosing of the water bottom and the equal sigma surface, lends significant advantages in terms of vertical temperature in the simulation for local deep water with steep terrain, and shortens runtime for 0.14 h. SGZ mixed coordinates are recommended in the simulation of deep lakes or reservoirs wherein the underwater topography is large (with abundant continuous deep trenches or reefs).

     

Integrated factor analysis of water level variation in geographically isolated ponds

Environmental Science and Pollution Research - Small geographically isolated ponds provide a multitude of ecological functions and services, but water table fluctuations alter the magnitude of...