Redox reactions of iron and manganese oxides in complex systems

• Mechanisms of redox reactions of Fe- and Mn-oxides were discussed. • Oxidative reactions of Mn- and Fe-oxides in complex systems were reviewed. • Reductive reaction of Fe(II)/iron oxides in complex systems was examined. • Future research on examining the redox reactivity in complex systems was suggested. Conspectus Redox reactions of Fe- and Mn-oxides play important roles in the fate and transformation of many contaminants in natural environments. Due to experimental and analytical challenges associated with complex environments, there has been a limited understanding of the reaction kinetics and mechanisms in actual environmental systems, and most of the studies so far have only focused on simple model systems. To bridge the gap between simple model systems and complex environmental systems, it is necessary to increase the complexity of model systems and examine both the involved interaction mechanisms and how the interactions affected contaminant transformation. In this Account, we primarily focused on (1) the oxidative reactivity of Mn- and Fe-oxides and (2) the reductive reactivity of Fe(II)/iron oxides in complex model systems toward contaminant degradation. The effects of common metal ions such as Mn²⁺ , Ca²⁺, Ni²⁺, Cr³⁺ and Cu²⁺, ligands such as small anionic ligands and natural organic matter (NOM), and second metal oxides such as Al, Si and Ti oxides on the redox reactivity of the systems are briefly summarized.     

Real-world fuel consumption of light-duty passenger vehicles using on-board diagnostic (OBD) systems

• Fuel consumption (FC) from LDPVs is measured using on-board diagnostic method (OBD). • The FC of the OBD is 7.1% lower than that of the carbon balance results. • The discrepancy between the approved FC and real-world FC is 13%±18%. • There is a strong relationship (R²=0.984) between the average speed and relative FC. An increasing discrepancy between real-world and type-approval fuel consumption for light-duty passenger vehicles (LDPVs) has been reported by several studies. Normally, real-world fuel consumption is measured primarily by a portable emission measurement system. The on-board diagnostic (OBD) approach, which is flexible and offers high-resolution data collection, is a promising fuel consumption monitoring method. Three LDPVs were tested with a laboratory dynamometer based on a type-approval cycle, the New European Driving Cycle (NEDC). Fuel consumption was measured by the OBD and constant-volume sampling system (CVS, a regulatory method) to verify the accuracy of the OBD values. The results of the OBD method and the regulatory carbon balance method exhibited a strong linear correlation (e.g., R² = 0.906-0.977). Compared with the carbon balance results, the fuel consumption results using the OBD were 7.1%±4.3% lower on average. Furthermore, the real-world fuel consumption of six LDPVs was tested in Beijing using the OBD. The results showed that the normalized NEDC real-world fuel consumption of the tested vehicles was 13%±17% higher than the type-approval-based fuel consumption. Because the OBD values are lower than the actual fuel consumption, using a carbon balance method may result in a larger discrepancy between real-word and type-approval fuel consumption. By means of the operating mode binning and micro trip methods, a strong relationship (R² = 0.984) was established between the average speed and relative fuel consumption. For congested roads (average vehicle speed less than 25 km/h), the fuel consumption of LDPVs is highly sensitive to changes in average speed.     

Reconnecting Cities to the Biosphere: Stewardship of Green Infrastructure and Urban Ecosystem Services

Within-city green infrastructure can offer opportunities and new contexts for people to become stewards of ecosystem services. We analyze cities as social–ecological systems, synthesize the literature, and provide examples from more than 15 years of research in the Stockholm urban region, Sweden. The social–ecological approach spans from investigating ecosystem properties to the social frameworks and personal values that drive and shape human interactions with nature. Key findings demonstrate that urban ecosystem services are generated by social–ecological systems and that local stewards are critically important. However, land-use planning and management seldom account for their role in the generation of urban ecosystem services. While the small scale patchwork of land uses in cities stimulates intense interactions across borders much focus is still on individual patches. The results highlight the importance and complexity of stewardship of urban biodiversity and ecosystem services and of the planning and governance of urban green infrastructure.     

Impacts of Nomad Sedentarization on Social and Ecological Systems at Multiple Scales in Xinjiang Uyghur Autonomous Region,China

China’s government is now promoting the Nomad Sedentarization Project (NSP) in large areas of grassland as a solution for ecological restoration and poverty alleviation. To examine the effects of this policy, we conducted in-depth interviews at two of the project’s sites and examined the social and ecological systems at village, county, and catchment scales in Jinghe County of Xinjiang. We found that (1) the NSP in one village greatly improved the household standard of living and changed their resource utilization modes; (2) the success in this village can be attributed to resources imported from the social and ecological systems at larger scales, and could not be repeated in a second nearby village with different constraints; and (3) the NSP is poorly adapted to local ecosystem characteristics, and may therefore have negative impacts at larger scales. To avoid these problems, holistic assessments are necessary to judge the NSP’s impacts on social and ecological systems at multiple scales, and the program must be implemented cautiously to account for the potential risks in ecologically vulnerable areas.     

Social Demand for Ecosystem Services and Implications for Watershed Management

We performed a sociocultural preference assessment for a suite of ecosystem services provided by the Kiamichi River watershed in the south‐central United States, a region with intense water conflict. The goal was to examine how a social assessment of services could be used to weigh tradeoffs among water resource uses for future watershed management and planning. We identified the ecosystem services beneficiaries groups, analyzed perception for maintaining services, assessed differences in the importance and perceived trends for ecosystem services, and explored the perceived impact on ecosystem services arising from different watershed management scenarios. Results show habitat for species and water regulation were two ecosystem services all beneficiaries agreed were important. The main discrepancies among stakeholder groups were found for water‐related services. The identification of potential tradeoffs between services under different flow scenarios promotes a dynamic management strategy for allocating water resources, one that mitigates potential conflicts. While it is widely accepted the needs of all beneficiaries should be considered for the successful incorporation of ecosystem services into watershed management, the number of studies actually using the sociocultural perspective in ecosystem service assessment is limited. Our study demonstrates it is both possible and useful to quantify social demand of ecosystem services in watershed management.     

Two-stage vertex analysis method for planning electric power systems with greenhouse gas abatement consideration

This study presents a two-stage vertex analysis (TSVA) method for the planning of electric power systems (EPS) under uncertainty. TSVA has advantages in comparison to other optimization techniques. Firstly, TSVA can incorporate greenhouse gas (GHG) abatement policies directly into its optimization process, and, secondly, it can readily integrate inherent system uncertainties expressed as fuzzy sets and probability distributions directly into its modeling formulation and solution procedure. The TSVA method is applied to a case study of planning EPS and it is demonstrated how the TSVA efficiently identify optimal electricity-generation schemes that could help to minimize system cost under different GHG-abatement considerations. Different combinative considerations on the uncertain inputs lead to varied system costs and GHG emissions. Results reveal that the total electricity supply will rise up along with the time period due to the increasing demand and, at the same time, more non-fossil fuels should be used to satisfy the increasing requirement for GHG mitigation. Moreover, uncertainties in connection with complexities in terms of information quality (e.g., capacity, efficiency, and demand) result in changed electricity-generation patterns, GHG-abatement amounts, as well as system costs. Minimax regret (MMR) analysis technique is employed to identify desired alternative that reflects compromises between system cost and system-failure risk.     

合流制排水系统降雨径流初期冲刷效应

通过对昆明主城区3个集水区合流制排水系统10次降雨径流过程水质水量的监测,计算了污染物的次降雨平均浓度(EMC),并采用无因次累积负荷体积分数曲线(M(V)曲线)和初期冲刷系数方法对初期冲刷现象进行了探讨。结果表明:(1)对于同一个常规污染指标,不同集水区的EMC平均值没有较明显差异,但都表现出较高浓度的污染特征。不同集水区总悬浮颗粒物(TSS)、COD、TN和TP的EMC平均值分别为140.18~174.11、144.65~161.78、21.44~23.18、1.80~2.35mg/L。(2)3个集水区所有观测降雨事件中,TP、TN、COD和TSS的初期30%径流量所对应的污染物累积负荷量(FF30)平均值分别为38.7%、37.1%、40.7%、44.6%;TSS和COD的初期冲刷强度明显较TP和TN变化更剧烈,不同污染物初期冲刷强度依次为TSSCODTPTN。(3)对于合流制排水系统,在区域特征相近情况下,汇水面积越小则初期冲刷效应越显著。而当汇水面积大到一定程度时,不同集水区之间初期冲刷强度没有显著差异。(4)降雨量、平均雨强和最大雨强与合流制排水系统的初期冲刷强度呈显著的正相关性,是影响其初期冲刷的重要水文参数;降雨历时和前期晴天与其初期冲刷强度没有显著相关性,两者对初期冲刷无明显影响。     

燃煤电厂排放总气态汞连续自动监测技术的选择

介绍了汞连续排放监测系统和汞吸附管采样系统的主要特点,比较了不同仪器的测定原理、样品处理技术、检出限和测定汞的形态,报道了美国环境保护署认证中心关于两个系统的认证结果.建议将汞连续排放监测系统与汞吸附管监测系统两种技术联合用于我国燃煤电厂排放总气态汞的自动监测.     

水土环境介质中阿特拉津修复过程研究进展

除草剂阿特拉津农用后的残留物会随地表径流或地下渗漏作用进入江河湖泊等自然水体,由于阿特拉津的环境内分泌干扰作用,其会造成水资源污染和水生态失衡。根据阿特拉津的生产和使用状况,将阿特拉津的污染对象分为土壤、市政污水、河流湖泊等地表水和地下水系统模块,分别阐述了这几种环境介质中阿特拉津的物理、化学和生物修复技术以及阿特拉津在修复过程中的变化特点,介绍了土壤在淋溶过程中阿特拉津的固定手段和今后污染水体中阿特拉津修复的研究重点。