Calcium oxide for CO2 capture: Operational window and efficiency penalty in sorption-enhanced steam methane reforming

Calcium oxide (CaO) is a material that is being widely investigated in the context of CO₂ capture. One such application is as a CO₂ sorbent in the sorption-enhanced steam methane reforming processes (SERP). CO₂ is captured in an adsorption mode, where the conversion of CH₄ to H₂ is also enhanced, and released later in a separate desorption mode. This work presents an analysis of the relation between different process conditions and parameters during both adsorption and desorption modes. The interrelation between these conditions and the sorbent properties as well as the targeted carbon capture ratio is analysed. Conditions relevant for capturing 85% of carbon in the feed on CaO are determined and interlinked. A steam-to-carbon ratio of 4.2 has been determined to be relevant under 600 °C and 17 bar adsorption conditions. Similarly, process conditions relevant for regenerating the sorbent are determined and interlinked. For purge steam-to-CO₂ ratio of 1.8 at a desorption pressure of 1 bar, relevant desorption temperature has been calculated to be 820 °C. System simulations under these adsorption and desorption conditions resulted in a system efficiency of 50.8%. Effect of tuning process operating conditions on system efficiency as well as the efficiency penalty associated with the regeneration of the sorbent are investigated by process simulations using Aspen Plus^®. Possible system heat integration routes to reduce the efficiency penalty are proposed and the results of the process simulations are presented.     

The ChimERA project: coupling mechanistic exposure and effect models into an integrated platform for ecological risk assessment

Current techniques for the ecological risk assessment of chemical substances are often criticised for their lack of environmental realism, ecological relevance and methodological accuracy. ChimERA is a 3-year project (2013–2016), funded by Cefic’s Long Range Initiative (LRI) that aims to address some of these concerns by developing and testing mechanistic fate and effect models, and coupling of these models into one integrated platform for risk assessment. This paper discusses the backdrop against which this project was initiated and lists its objectives and planned methodology.     

保护生态系统亟需对农药进行注册后监测

现行的农药准入政策遵循一种可控的实验性分级风险评估方法,结果很难外推到实际情况。对DDT和烟碱类杀虫剂等化合物的分析清楚地表明,化学品对生态系统的实际影响比风险评估的预计更大。因此,为了管理由人工合成的化合物对生态系统造成的实际风险,提出了目前的化学药品准入政策,并通过注册后监测来补充。这种监测对于识别化合物通过多种传播途径和暴露方式对生物体产生的直接和间接影响是至关重要的。实施注册后监测可以建立在现有的监测网络上。这一方法将解决基于区域型法规与基于暴露型法规的现行政策僵局,更重要的是,将为跨部门间的风险评估提供一个安全锁,更有可能确保我们的自然环境得到保护。
精选自Vijver, M. G., Hunting, E. R., Nederstigt, T. A.P., Tamis, W. L.M., van den Brink, P. J. and van Bodegom, P. M. (2017), Postregistration monitoring of pesticides is urgently required to protect ecosystems. Environmental Toxicology and Chemistry, 36: 860–865. doi: 10.1002/etc.3721
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.3721/full
     

Fate and transport of chlormequat in subsurface environments

Background, aim and scope  

Chlormequat (Cq) is a plant growth regulator used throughout the world. Despite indications of possible effects of Cq on mammalian health and fertility, little is known about its fate and transport in subsurface environments. The aim of this study was to determine the fate of Cq in three Danish subsurface environments, in particular with respect to retardation of Cq in the A and B horizons and the risk of leaching to the aquatic environment. The study combines laboratory fate studies of Cq sorption and dissipation with field scale monitoring of the concentration of Cq in the subsurface environment, including artificial drains.     

Triclosan affects the microbial community in simulated sewage-drain-field soil and slows down xenobiotic degradation

Effects of the common antibacterial agent triclosan on microbial communities and degradation of domestic xenobiotics were studied in simulated sewage-drain-field soil. Cultivable microbial populations decreased 22-fold in the presence of 4 mg kg⁻¹ of triclosan, and triclosan-resistant Pseudomonas strains were strongly enriched. Exposure to triclosan also changed the general metabolic profile (Ecoplate substrate profiling) and the general profile (T-RFLP) of the microbial community. Triclosan degradation was slow at all concentrations tested (0.33-81 mg kg⁻¹) during 50-days of incubation. Mineralization experiments (¹⁴C-tracers) and chemical analyses (LC-MS/MS) showed that the persistence of a linear alkylbenzene sulfonate (LAS) and a common analgesic (ibuprofen) increased with increasing triclosan concentrations (0.16-100 mg kg⁻¹). The largest effect was seen for LAS mineralization which was severely reduced by 0.16 mg kg⁻¹ of triclosan. Our findings indicate that environmentally realistic concentrations of triclosan may affect the efficiency of biodegradation in percolation systems.     

Conducting model ecosystem studies in tropical climate zones: lessons learned from Thailand and way forward

Little research has been done so far into the environmental fate and side effects of pesticides in the tropics. In addition, those studies conducted in tropical regions have focused almost exclusively on single species laboratory tests. Hence, fate and effects of pesticides on higher-tier levels have barely been studied under tropical conditions. To address this lack of knowledge, four outdoor aquatic model ecosystem experiments using two different test systems were conducted in Thailand evaluating the insecticide chlorpyrifos, the herbicide linuron and the fungicide carbendazim. Results of these experiments and comparisons of recorded fate and effects with temperate studies have been published previously. The present paper discusses the pros and cons of the methodologies applied and provides indications for i) possible improvements; ii) important aspects that should be considered when performing model ecosystem experiments in the tropics; iii) future research.     

Managing broiler litter application rate and grazing to decrease watershed runoff losses

Pasture management and broiler litter application rate are critical factors influencing the magnitude of nutrients being transported by runoff from fields. We investigated the impact of pasture management and broiler litter application rate on nutrient runoff from bermudagrass (Cynodon dactylon) pastures. The experiment was conducted on a Ruston fine sandy loam with a factorial arrangement on 21 large paddocks. Runoff water was collected from natural rainfall events from 2001 to 2003. Runoff water and soil samples were analyzed for nutrients and sediments. Runoff was generally greater (29%) from grazed than hayed pastures regardless of the litter application rate. There was greater inorganic N in the runoff from grazed paddocks when litter rate was based on N rather than P. The mean total P loss per runoff event for all treatments ranged from 7 to 45 g ha(-1) and the grazed treatment with litter applied on N basis had the greatest total P loss. Total dissolved P was the dominant P fraction in the runoff, ranging from 85% to 93% of the total P. The soluble reactive P was greater for treatments with litter applied on N basis regardless of pasture management. Runoff total sediments were greater for N-based litter application compared to those which received litter on P basis. Our results indicate that litter may be applied on N basis if the pasture is hayed and the soil P is low. In contrast, litter rates should be based on a P-basis if pasture is grazed.     

Type 'A' and 'B' recovery revisited: the role of field-edge habitats for Collembola and macroarthropod community recovery after insecticide treatment

Previous work has identified two patterns of arthropod recovery after insecticide applications to arable crops: dispersal-mediated recolonisation from untreated areas (Type A) and recolonisation within treated areas assisted by reduced predation (Type B). In this study, connectivity between field-edge habitats was manipulated using barriers to investigate whether a crop edge and adjacent hedgerow influence recolonisation of an insecticide-treated crop by surface-active Collembola and other arthropods. Collembola recovery patterns differed among closely-related taxa. Epigeic collembolan and macroarthropod communities were more diverse and abundant, and rates of artificial prey predation were higher, in sprayed crop areas connected to both hedgerow and unsprayed crop edge than in sprayed areas connected to the unsprayed edge alone. These findings indicate that effectiveness of unsprayed crop edges as sources of field recolonisation may depend on adjoining field margin habitats. An assumption in risk assessment that unsprayed crop edges assist population recovery within treated areas is not supported.     

Dependence of home outdoor particulate mass and number concentrations on residential and traffic features in urban areas

The associations between residential outdoor and ambient particle mass, fine particle absorbance, particle number (PN) concentrations, and residential and traffic determinants were investigated in four European urban areas (Helsinki, Athens, Amsterdam, and Birmingham). A total of 152 nonsmoking participants with respiratory diseases, not exposed to occupational pollution, were included in the study, which comprised a 7-day intensive exposure monitoring period of both indoor and home outdoor particle mass and number concentrations. The same pollutants were also continuously measured at ambient fixed sites centrally located to the studied areas (fixed ambient sites). Relationships between concentrations measured directly outside the homes (residential outdoor) and at the fixed ambient sites were pollutant-specific, with substantial variations among the urban areas. Differences were more pronounced for coarse particles due to resuspension of road dust and PN, which is strongly related to traffic emissions. Less significant outdoor-to-fixed variation for particle mass was observed for Amsterdam and Birmingham, predominantly due to regional secondary aerosol. On the contrary, a strong spatial variation was observed for Athens and to a lesser extent for Helsinki. This was attributed to the overwhelming and time-varied inputs from traffic and other local sources. The location of the residence and traffic volume and distance to street and traffic light were important determinants of residential outdoor particle concentrations. On average, particle mass levels in suburban areas were less than 30% of those measured for residences located in the city center. Residences located less than 10 m from a street experienced 133% higher PN concentrations than residences located further away. Overall, the findings of this multi-city study, indicated that (1) spatial variation was larger for PN than for fine particulate matter (PM) mass and varied between the cities, (2) vehicular emissions in the residential street and location in the center of the city were significant predictors of spatial variation, and (3) the impact of traffic and location in the city was much larger for PN than for fine particle mass.