Refinery evaluation of optical imaging to locate fugitive emissions

Fugitive emissions account for approximately 50% of total hydrocarbon emissions from process plants. Federal and state regulations aiming at controlling these emissions require refineries and petrochemical plants in the United States to implement a Leak Detection and Repair Program (LDAR). The current regulatory work practice, U.S. Environment Protection Agency Method 21, requires designated components to be monitored individually at regular intervals. The annual costs of these LDAR programs in a typical refinery can exceed US$1,000,000. Previous studies have shown that a majority of controllable fugitive emissions come from a very small fraction of components. The Smart LDAR program aims to find cost-effective methods to monitor and reduce emissions from these large leakers. Optical gas imaging has been identified as one such technology that can help achieve this objective. This paper discusses a refinery evaluation of an instrument based on backscatter absorption gas imaging technology. This portable camera allows an operator to scan components more quickly and image gas leaks in real time. During the evaluation, the instrument was able to identify leaking components that were the source of 97% of the total mass emissions from leaks detected. More than 27,000 components were monitored. This was achieved in far less time than it would have taken using Method 21. In addition, the instrument was able to find leaks from components that are not required to be monitored by the current LDAR regulations. The technology principles and the parameters that affect instrument performance are also discussed in the paper.     

Levels and possible sources of PCDD/PCDF in sediment and pike samples from Swedish lakes and rivers. (Part one)

One goal of the Swedish survey project is to discover possible sources of PCDD/F. Bottom sediment and pike were sampled at various sites near different types of industries along the coast line of two lakes and one river. The results show background levels of PCDD/F in some lakes which can only be explained by atmospheric input. In some lakes paper mill emissions of chlorinated PCDD/F give high levels of local contamination (≈1 ng/g IG) within short distances (<1 km) from the source. PCDD/F from paper mill effluents are transported long distances and traces can be detected over the entire lake area. The PCDD/F levels in pike are correlated with levels in the underlying sediment.     

盐池湾国家级自然保护区景观格局演变分析

景观格局演化是土地利用/覆盖变化和景观破碎化在时空上的直接表现,其时空演变过程和影响因素分析,对了解区域生态环境变化、维持生态系统平衡及可持续发展具有重要意义。该文基于1996、2006和2017年3期遥感影像,结合景观格局分析方法,对盐池湾国家级自然保护区近20年景观格局时空演变及影响因素进行分析。结果表明:1996-2017年盐池湾国家级自然保护区沼泽草地、沼泽地、冰川及永久积雪和沙地面积增幅分别为42.05%、63.24%、259.03%和87.62%,天然牧草地、河流水面和裸岩石砾地面积降幅分别为20.15%、24.33%和22.39%;斑块密度、最大斑块指数减小,斑块形状趋于简单,连通性增强,景观的破碎化程度降低;降水与冰川及永久积雪和裸岩石砾地呈显著相关(P<0.05),气温与各土地覆被类型之间关系不显著(P>0.05)。在自然和人为活动共同作用下,盐池湾国家级自然保护区的景观格局向连通性高、破碎化程度降低的方向演变。     

Home buyouts and household recovery: neighborhood differences three years after Hurricane Sandy

Home buyout programs facilitate the permanent relocation of residents away from areas considered to be at risk from future hazards, though few studies have examined the impacts of home buyout programs on affected households and communities beyond the program implementation period. In this paper, we examine between-neighborhood variation in key recovery indicators for three neighborhoods that followed different paths to recovery after Hurricane Sandy: one that rebuilt in situ, one that participated in a buyout and relocated, and one located immediately adjacent to the buyout zone. Three years post-disaster, buyout participants are faring worse in terms of place attachment and social capital compared to residents in the other two neighborhoods, while the neighborhood adjacent to the buyout zone is also showing signs of decline. These findings suggest that the social costs of buyouts extend well into the recovery period, and that the place-based ties and social networks that would typically help individuals cope with disaster impacts and persevere through adversity may be diminished for buyout participants, ultimately hindering their recovery. We conclude with a discussion of the implications of buyouts on participating and affected communities, as well as implications for research and policy.     

Levels, profile and pattern of PCDDs and PCDFs in samples related to the production and use of chlorine

Analyses of sludge from graphite electrodes used in the chloralkali process show total levels of PCDFs as high as 650000 pg/g sludge. The levels of tetra-, penta-and hexaCDFs were found to be approximately the same. The levels for the corresponding PCDDs were below the detection level. The dominating congeners within each group are the toxic 2,3,7,8-substituted PCDFs at levels of 340000 pg/g, This typical pattern, called the “chloralkali pattern” can also be found in soil samples taken at another chloralkali plant. The typical pattern can also be identified in a solution of ferric chloride. Traces of “chloralkali pattern” are identified in a sludge sample from the drinking water purification plant, the source for PCDFs in the sludge is unknown.     

Levels of PCDDs and PCDFs in products and effluent from the Swedish pulp and paper industry and chloralkali process

Within the Swedish Dioxin Survey various samples from the pulp and paper industry and the chloralkali process have been analyzed by congener specific analytical methods. In addition to the generally discussed “bleaching pattern” of the tetrachlorinated congeners, these samples also contained higher chlorinated congeners like hexa-CDDs, hepta-CDFs, octa-CDD and octa-CDF. Consequently it is recommended that samples from the pulp industry should be analyzed for all PCDDs and PCDFs (tetra- through octa-). Counted as Nordic Toxic Equivalents (NTEQ), the recycled pulp samples had the highest contamination level followed by TMP, unbleached sulfite and bleached softwood and hardwood. In addition to the bleaching process, various chemicals used in the pulping, bleaching and wastewater treatment can contribute to the contamination.