China's natural wetlands: past problems, current status, and future challenges

Natural wetlands, occupying 3.8% of China's land and providing 54.9% of ecosystem services, are unevenly distributed among eight wetland regions. Natural wetlands in China suffered great loss and degradation (e.g., 23.0% freshwater swamps, 51.2% costal wetlands) because of the wetland reclamation during China's long history of civilization, and the population pressure and the misguided policies over the last 50 years. Recently, with an improved understanding that healthy wetland ecosystems play a vital role in her sustainable economic development, China started major efforts in wetland conservation, as signified by the policy to return reclaimed croplands to wetlands, the funding of billions of dollars to restore degraded wetlands, and the national plan to place 90% of natural wetlands under protection by 2030. This paper describes the current status of the natural wetlands in China, reviews past problems, and discusses current efforts and future challenges in protecting China's natural wetlands.     

土壤气监测在污染地块调查评估中的优势、局限及解决思路

目前,我国污染地块调查评估以土壤监测为主,辅以地下水监测。这套方法对于挥发性有机物(VOCs)的特殊性考虑不足,可能出现遗漏污染区域的可能性。与土壤监测相比,土壤气监测在VOCs污染地块调查评估中具有可捕捉VOCs污染区域的能力更强,能更准确反映VOCs的气态扩散迁移过程和呼吸暴露风险,以及长期监测成本较低等优势,故有必要将土壤气监测作为VOCs污染地块调查评估的常规工作内容。针对土壤气监测在国内推广应用中仍受到缺乏土壤气采样技术规范、分析检测标准方法、土壤气环境质量标准或风险筛选值及相应的数据分析方法等问题的局限,提出相应的解决思路以供参考。     

Seaweed future cultivation in Chile: perspectives and challenges

Production of seaweeds in Chile has fluctuated between 120,000 and 316,000 wet metric tons per year during the last ten years. The most important Phaeophyta are exploited for alginate production and as abalone feed. Among the Rhodophyta, Chilean production comes mainly from wild stocks, as at present cultivation on a commercial scale is restricted to Gracilaria. Large scale production of this species has been the result of a sharp increase in the number of farms. During the last five years an important trend towards diversification of seaweed exploitation and cultivation has developed. The demand for brown algal materials for the alginate industry, abalone cultivation, seaweed flour production for human and animal feeding and the development of novel food products has encouraged the farming of Macrocystis pyrifera and of red edible seaweeds, such as Chondracanthus chamissoi and Callophyllis variegata, is also promoting the development of cultivation activities.     

Climate change,future Arctic Sea ice,and the competitiveness of European Arctic offshore oil and gas production on world markets

A significant share of the world’s undiscovered oil and natural gas resources are assumed to lie under the seabed of the Arctic Ocean. Up until now, the exploitation of the resources especially under the European Arctic has largely been prevented by the challenges posed by sea ice coverage, harsh weather conditions, darkness, remoteness of the fields, and lack of infrastructure. Gradual warming has, however, improved the accessibility of the Arctic Ocean. We show for the most resource-abundant European Arctic Seas whether and how a climate induced reduction in sea ice might impact future accessibility of offshore natural gas and crude oil resources. Based on this analysis we show for a number of illustrative but representative locations which technology options exist based on a cost-minimization assessment. We find that under current hydrocarbon prices, oil and gas from the European offshore Arctic is not competitive on world markets.     

Measuring carbon in forests: current status and future challenges

To accurately and precisely measure the carbon in forests is gaining global attention as countries seek to comply with agreements under the UN Framework Convention on Climate Change. Established methods for measuring carbon in forests exist, and are best based on permanent sample plots laid out in a statistically sound design. Measurements on trees in these plots can be readily converted to aboveground biomass using either biomass expansion factors or allometric regression equations. A compilation of existing root biomass data for upland forests of the world generated a significant regression equation that can be used to predict root biomass based on aboveground biomass only. Methods for measuring coarse dead wood have been tested in many forest types, but the methods could be improved if a non-destructive tool for measuring the density of dead wood was developed. Future measurements of carbon storage in forests may rely more on remote sensing data, and new remote data collection technologies are in development.     

加油站埋地油罐呼吸排放因子法的本地化应用

加油站汽油挥发是挥发性有机物(VOCs)的重要来源之一。加油站VOCs排放包括卸油排放、加油排放、呼吸排放、加油枪滴油和胶管渗透排放等5个环节。针对加油站各环节排放因子已开展了诸多统计研究,但并未考虑加油站工艺及设备配置、日均加油规模等因素对排放因子的影响。参考美国CARB认证规程,采用自主研发的加油站呼吸排放测试系统,以北京某年销汽油量约9 000 t且未安装油气处理装置的加油站为测试站点,开展埋地油罐呼吸排放因子的本地化研究。通过对呼吸排放量的连续监测,采用实验检测与数据统计相结合的方法,研究呼吸排放因子与加油量的相关性。结果表明：加油站的埋地油罐呼吸排放因子与日均加油量显著相关;对于标准化加油站,日均加油量小于15 920 L时,呼吸排放因子为0;随着日均加油量的升高,呼吸排放因子逐步升高,且符合多项式方程;超过28 800 L后,呼吸排放因子变化趋于稳定在约30 mg·L⁻¹。综合考虑后处理装置安装成本和产生的环境效益,年汽油销售规模超过4 500 t的加油站应安装后处理装置,以降低呼吸排放的油气量。本研究结果可为不同规模加油站的VOCs排放分级管理提供参考。     

Interactions of forests with secondary air pollutants: some challenges for future research

The effects of ozone and other photochemical oxidants on individual trees have been studied for several decades, but there has been much less research on the potential effects on entire forest ecosystems. Given that ozone and other oxidants affect the production and subsequent fate of biogenic volatile organic compounds that act as signalling molecules, there is a need for more detailed study of the role of oxidants in modifying trophic interactions in forests. Deposition of fine particulates to forests may act as a source of nutrients, but also changes leaf surface properties, increasing the duration of surface wetness and modifying the habitat for epiphytic organisms, leading to increased risks from pathogens. Even where this pathway contributes a relatively small input of nutrients to forests, the indirect effects on canopy processes and subsequent deposition to the forest floor in throughfall and litter may play a more important role that has yet to be fully investigated.     

Emissions tradeoffs among alternative marine fuels: total fuel cycle analysis of residual oil, marine gas oil, and marine diesel oil

Worldwide concerns about sulfur oxide (SOx) emissions from ships are motivating the replacement of marine residual oil (RO) with cleaner, lower-sulfur fuels, such as marine gas oil (MGO) and marine diesel oil (MDO). Vessel operators can use MGO and MDO directly or blended with RO to achieve environmental and economic objectives. Although expected to be much cleaner in terms of criteria pollutants, these fuels require additional energy in the upstream stages of the fuel cycle (i.e., fuel processing and refining), and thus raise questions about the net impacts on greenhouse gas emissions (primarily carbon dioxide [CO2]) because of production and use. This paper applies the Total Energy and Environmental Analysis for Marine Systems (TEAMS) model to conduct a total fuel cycle analysis of RO, MGO, MDO, and associated blends for a typical container ship. MGO and MDO blends achieve significant (70-85%) SOx emissions reductions compared with RO across a range of fuel quality and refining efficiency assumptions. We estimate CO2 increases of less than 1% using best estimates of fuel quality and refinery efficiency parameters and demonstrate how these results vary based on parameter assumptions. Our analysis suggests that product refining efficiency influences the CO2 tradeoff more than differences in the physical and energy parameters of the alternative fuels, suggesting that modest increases in CO2 could be offset by efficiency improvements at some refineries. Our results help resolve conflicting estimates of greenhouse gas tradeoffs associated with fuel switching and other emissions control policies.     

The air quality forecast rote: Recent changes and future challenges

Air quality forecasting is a recent development, with most programs initiated only in the last 20 years. During the last decade, forecast preparation procedure—the forecast rote—has changed dramatically. This paper summarizes the unique challenges posed by air quality forecasting, details the current forecast rote, and analyzes prospects for future improvements. Because air quality forecasts must diagnose and predict several pollutants and their precursors in addition to standard meteorological variables, it is, compared with weather forecasts, a higher-uncertainty forecast. Forecasters seek to contain the uncertainty by “anchoring” the forecast, using an a priori field, and then “adjusting” the forecast using additional information. The air quality a priori, or first guess, field is a blend of past, current, and near-term future observations of the pollutants of interest, on both local and regional scales, and is typically coupled with predicted air parcel trajectories. Until recently, statistical methods, based on long-term training data sets, were used to adjust the first guess. However, reductions in precursor emissions in the United States, beginning in the late 1990s and continuing to the present, eroded the stationarity assumption for the training data sets and degraded forecast skill. Beginning in the mid-2000s, output from modified numerical air quality prediction (NAQP) models, originally developed to test pollution control strategies, became available in near real time for forecast support. The current adjustment process begins with the analyses and postprocessing of individual NAQP models and their ad hoc ensembles, often in concert with new statistical techniques. The final adjustment step uses forecaster expertise to assess the impact of mesoscale features not resolved by the NAQP models. It is expected that advances in model resolution, chemical data assimilation, and the formulation of emissions fields will improve mesoscale predictions by NAQP models and drive future changes in the forecast rote.

Implications: Routine air quality forecasts are now issued for nearly all the major U.S. metropolitan areas. Methods of forecast preparation—the forecast rote—have changed significantly in the last decade. Numerical air quality models have matured and are now an indispensable part of the forecasting process. All forecasting methods, particularly statistically based models, must be continually calibrated to account for ongoing local- and regional-scale emission reductions.     

Variable-density groundwater flow and solute transport in heterogeneous porous media: approaches, resolutions and future challenges

In certain hydrogeological situations, fluid density variations occur because of changes in the solute or colloidal concentration, temperature, and pressure of the groundwater. These include seawater intrusion, high-level radioactive waste disposal, groundwater contamination, and geothermal energy production. When the density of the invading fluid is greater than that of the ambient one, density-driven free convection can lead to transport of heat and solutes over larger spatial scales and significantly shorter time scales than compared with diffusion alone. Beginning with the work of Lord Rayleigh in 1916, thermal and solute instabilities in homogeneous media have been studied in detail for almost a century. Recently, these theoretical and experimental studies have been applied in the study of groundwater phenomena, where the assumptions of homogeneity and isotropy rarely, if ever, apply. The critical role that heterogeneity plays in the onset as well as the growth and/or decay of convective motion is discussed by way of a review of pertinent literature and numerical simulations performed using a variable-density flow and solute transport numerical code. Different styles of heterogeneity are considered and range from continuously "trending" heterogeneity (sinusoidal and stochastic permeability distributions) to discretely fractured geologic media. Results indicate that both the onset of instabilities and their subsequent growth and decay are intimately related to the structure and variance of the permeability field. While disordered heterogeneity tends to dissipate convection through dispersive mixing, an ordered heterogeneity (e.g., sets of vertical fractures) allows instabilities to propagate at modest combinations of fracture aperture and separation distances. Despite a clearer understanding of the processes that control the onset and propagation of instabilities, resultant plume patterns and their migration rates and pathways do not appear amenable to prediction at present. The classical Rayleigh number used to predict the occurrence of instabilities fails, in most cases, when heterogeneous conditions prevail. The incorporation of key characteristics of the heterogeneous permeability field into relevant stability criteria and numerical models remains a challenge for future research.     

Baltic Sea ecosystem-based management under climate change: Synthesis and future challenges

Ecosystem-based management (EBM) has emerged as the generally agreed strategy for managing ecosystems, with humans as integral parts of the managed system. Human activities have substantial effects on marine ecosystems, through overfishing, eutrophication, toxic pollution, habitat destruction, and climate change. It is important to advance the scientific knowledge of the cumulative, integrative, and interacting effects of these diverse activities, to support effective implementation of EBM. Based on contributions to this special issue of AMBIO, we synthesize the scientific findings into four components: pollution and legal frameworks, ecosystem processes, scale-dependent effects, and innovative tools and methods. We conclude with challenges for the future, and identify the next steps needed for successful implementation of EBM in general and specifically for the Baltic Sea.     

Volatile organic compounds at two oil and natural gas production well pads in Colorado and Texas using passive samplers

A pilot study was conducted in application of the U.S. Environmental Protection Agency (EPA) Methods 325A/B variant for monitoring volatile organic compounds (VOCs) near two oil and natural gas (ONG) production well pads in the Texas Barnett Shale formation and Colorado Denver–Julesburg Basin (DJB), along with a traffic-dominated site in downtown Denver, CO. As indicated in the EPA method, VOC concentrations were measured for 14-day sampling periods using passive-diffusive tube samplers with Carbopack X sorbent at fenceline perimeter and other locations. VOCs were significantly higher at the DJB well pad versus the Barnett well pad and were likely due to higher production levels at the DJB well pad during the study. Benzene and toluene were significantly higher at the DJB well pad versus downtown Denver. Except for perchloroethylene, VOCs measured at passive sampler locations (PSs) along the perimeter of the Barnett well pad were significantly higher than PSs farther away. At the DJB well pad, most VOC concentrations, except perchloroethylene, were significantly higher prior to operational changes than after these changes were made. Though limited, the results suggest passive samplers are precise (duplicate precision usually ≤10%) and that they can be useful to assess spatial gradients and operational conditions at well pad locations over time-integrated periods.

Implications: Recently enacted EPA Methods 325A/B use passive-diffusive tube samplers to measure benzene at multiple fenceline locations at petrochemical refineries. This pilot study presents initial data demonstrating the utility of Methods 325A/B for monitoring at ONG facilities. Measurements revealed elevated concentrations reflective of production levels and spatial gradients of VOCs relative to source proximity at the Barnett well pad, as well as operational changes at the DJB well pad. Though limited, these findings indicate that Methods 325A/B can be useful in application to characterize VOCs at well pad boundaries.     

The impact of COVID-19 pandemic on air pollution: a global research framework,challenges, and future perspectives

Environmental Science and Pollution Research - As a result of extreme modifications in human activity during the COVID-19 pandemic, the status of air quality has recently been improved. This...     

Research status,challenges and future prospects of renewable synthetic fuel catalysts for CO2 photocatalytic reduction conversion

Environmental Science and Pollution Research - In recent years, with global climate change, the utilization of carbon dioxide as a resource has become an important goal of human society to achieve...     

管道式分离技术及其在油气行业混合介质分离中的应用

油气开采过程中会产生大量油、气、水、砂等两种或多种介质共存的混合液,混合介质的非均相分离是原油开采、炼制过程中重要的工艺单元。管道分离技术及装备以离心等动态分离为主要分离方式。通过离心、重力、膨胀、气浮等分离作用及其复合强化,开发出螺旋管、T型管、旋流管、管式聚结器、旋流气浮管等系列核心设备。大量工程应用实践显示,管道分离技术具有工艺模块化设计、应用灵活、占地小、分离效率高等优点,可适用于油气水分离、液固分离、除砂洗砂等不同场景需求,对于油气田老旧站扩容或升级改造,具有较好的技术经济优势和广阔的应用前景。     

Utilization of coal fly ash in China: a mini-review on challenges and future directions

Environmental Science and Pollution Research - The rapid economic development in China places a large demand for energy, and as a result, thermal power plants in China are producing an enormous...     

Pyrolysis-GC-MS analysis of crude and heavy fuel oil asphaltenes for application in oil fingerprinting

A Pyrolysis – Gas Chromatography – Mass Spectrometry (Py-GC-MS) method was developed for the analysis and profiling of crude and heavy fuel oil asphaltenes, for application in oil fingerprinting. Asphaltenes were precipitated from ten geographically different oils using n-pentane, and analysed by Py-GC-MS. Alkane profiles and sulphur/aromatic profiles were used to compare the oils, and to correctly differentiate oils from different geographical regions. Py-GC-MS could not differentiate a weathered oil sample and a fresh oil sample from the same source. The results of this study support the findings from a previously developed FTIR method for asphaltene profiling.