Overview of state approaches to vapor intrusion

A large number of states have issued guidance addressing the vapor intrusion pathway making it difficult to keep up with various policies and requirements. We have compiled and reviewed guidance from 35 states, half of which have issued documents within the last three years. A comparison of policies among states shows reasonable consistency in some areas—for example, 20 of 23 states that provide an exclusion distance for subsurface sources of chlorinated volatile organic compounds (VOCs) use a distance of 100 feet. However, more commonly, the policy decisions vary widely. Among states, indoor air screening concentrations for the same VOC vary by more than 2,000 times and subsurface screening concentrations vary by more than 2,000,000 times. These wide discrepancies suggest a need for communication and consensus building in order to increase consistency in the management of the vapor intrusion pathway. © 2012 Wiley Periodicals, Inc.     

Remediation techniques for mitigating vapor intrusion from sewer systems to indoor air

Investigations at former dry cleaning sites in Denmark show that sewer systems often are a major vapor intrusion pathway for chlorinated solvents to indoor air. In more than 20 percent of the contaminated drycleaner sites in Central Denmark Region, sewer systems were determined to be a major vapor intrusion pathway. Sewer systems can be a major intrusion pathway if contaminated groundwater intrudes into the sewer and contamination is transported within the sewer pipe by water flow in either free phase or dissolved states. Additionally, the contamination can volatilize from the water phase or soil gas can intrude the sewer system directly. In the sewer, the gas phase can migrate in any direction by convective transport or diffusion. Indications of the sewer as a major intrusion pathway are:

• higher concentrations in the upper floors in buildings,
• higher concentrations in indoor air than expected from soil gas measurements,
• higher concentrations in bathrooms/kitchen than in living rooms,
• chlorinated solvents in the sewer system, and
• a pressure gradient from the sewer system to indoor air.

Measurements to detect whether or not the sewer system is an intrusion pathway are simple. In Central Denmark Region, the concentrations of contaminants are routinely measured in the indoor air at all floors, the outdoor air, behind the water traps in the building, and in the manholes close to the building. The indoor and outdoor air concentration, as well as concentrations in manholes, are measured by passive sampling on sorbent samplers over a 14‐day period, and the measurements inside the sewer system are carried out by active sampling using carbon tubes (sorbent samplers). Furthermore, the pressure gradient over the building slab and between the indoor air and the sewer system are also measured. A simple test is depressurization of the sewer system. Using this technique, the pressure gradient between the sewer system and the indoor air is altered toward the sewer system—the contamination cannot enter the indoor air through the sewer system. If the sewer system is a major intrusion pathway, the effect of the test can be observed immediately in the indoor air. Remediation of a sewer transported contamination can be:

• prevention of the contaminants from intruding into the sewer system or
• prevention of the contaminated gas in the sewer system from intruding into the indoor air.

Remediation techniques include the following:

• lining of the sewer piping to prevent the contamination from intruding into the sewer;
• sealing the sewer system in the building to prevent the contamination from the sewer system to intrude the indoor air;
• venting of manholes; and
• depressurizing the sewer system.

     

Addressing soil gas vapor intrusion using sustainable building solutions

Soil gas vapor intrusion (VI) emerged in the 1990s as one of the most important problems in the investigation and cleanup of thousands of sites across the United States. A common practice for sites where VI has been determined to be a significant pathway is to implement interim building engineering controls to mitigate exposure of building occupants to VI while the source of contamination in underlying soil and groundwater is assessed and remediated. Engineering controls may include passive barriers, passive or active venting, subslab depressurization, building pressurization, and sealing the building envelope. Another recent trend is the emphasis on “green” building practices, which coincidentally incorporate some of these same engineering controls, as well as other measures such as increased ventilation and building commissioning for energy conservation and indoor air quality. These green building practices can also be used as components of VI solutions. This article evaluates the sustainability of engineering controls in solving VI problems, both in terms of long‐term effectiveness and “green” attributes. Long‐term effectiveness is inferred from extensive experience using similar engineering controls to mitigate intrusion of radon, moisture, mold, and methane into structures. Studies are needed to confirm that engineering controls to prevent VI can have similar long‐term effectiveness. This article demonstrates that using engineering controls to prevent VI is “green” in accelerating redevelopment of contaminated sites, improving indoor air quality, and minimizing material use, energy consumption, greenhouse gas emissions, and waste generation. It is anticipated that engineering controls can be used successfully as sustainable solutions to VI problems at some sites, such as those deemed technically impracticable to clean up, where remediation of underlying soil or groundwater contamination will not be completed in the foreseeable future. Furthermore, green buildings to be developed in areas of potential soil or groundwater contamination may be designed to incorporate engineering controls to prevent VI. © 2009 Wiley Periodicals, Inc.     

Chlorinated vapor intrusion indicators,tracers, and surrogates (ITS): Supplemental measurements for minimizing the number of chemical indoor air samples—Part 1: Vapor intrusion driving forces and related environmental factors

Vapor intrusion (VI) assessment is complicated by spatial and temporal variability, largely due to compounded interactions among the many individual factors that influence the vapor migration pathway from subsurface sources to indoor air. Past research on highly variable indoor air datasets demonstrates that conventional sampling schemes can result in false negative determinations of potential risk corresponding to reasonable maximum exposures (RME). While high‐frequency chemical analysis of individual chlorinated volatile organic compounds (CVOCs) in indoor air is conceptually appealing, it remains largely impractical when numerous buildings are involved and particularly for long‐term monitoring. As more is learned about the challenges with indoor air sampling for VI assessment, it has become clear that alternative approaches are needed to help guide discrete sampling efforts and reduce sampling requirements while maintaining acceptable confidence in exposure characterization. Indicators, tracers, and surrogates (ITS), which include a collection of quantifiable metrics and tools, have been suggested as a potential solution for making VI pathway assessment and long‐term monitoring more informative, efficient, and cost‐effective. This review, compilation, and evaluation of ITS demonstrates how even low numbers of indoor air CVOC samples can provide high levels of confidence for representing the RME levels (e.g., 95th percentile) often sought by regulatory agencies for less than chronic effects. A two‐part compilation of available evidence for select low‐cost ITS is presented, with Part 1 focused on introducing the concepts of ITS, meteorologically based ITS, and the evidence from data‐rich studies to support lower cost CVOC VI assessments. Part 1 includes the results of quantitative analyses on two robust residential building VI datasets, where numerous supplemental metrics were collected concurrently with indoor air concentration data. These are supplemented with additional less‐intensive studies in different circumstances. These analyses show that certain ITS metrics and tools, including differential temperature, differential pressure, and radon (in Part 2), can provide benefits to VI assessment and long‐term monitoring. This includes indicators that narrow the assessment period needed to capture RME conditions, tracers that enhance understanding of the conceptual site model, and aid in the identification of preferential pathways and surrogates that support or substitute for CVOC sampling results. The results of this review provide insight into the scientifically supportable uses of ITS.     

Terrestrial approaches to integration of waste treatment

Solar energy driven physical, chemical and biological recycling of nutrients is the characteristic of the Earth-Sun system which permits life on earth to continue. Natural recycle of nutrients on Earth may literally require thousands or even millions of years to be complete, but for modern civilization to continue on Earth or in space, mankind must take charge of, and accelerate, the recycle of all essentials of life. In this paper we describe studies of two accelerated recycle systems; a solar powered energy system and an integrated feed lot. Both systems require special infrastructures permitting the accelerated physical, chemical and biological processing to occur. These systems do not integrate respiratory carbon dioxide as must be done in a complete closed ecological life support system (CELSS). The Algatron, a more complete system involving microalgal bacterial waste treatment with water, oxygen and carbon dioxide recycle was designed for use in Space Stations over 20 years ago.     

现有设备协同脱汞技术概述

介绍了燃煤电站汞的排放状况,并指出了汞危害性以及我国面临的脱汞压力,论述了烟气中汞存在形式以及影响其存在形式的因素.探讨了当前燃煤电站利用现有污染控制设备进行协同脱汞的研究进展,包括：燃烧器/反应器、选择性催化还原脱硝（SCR）、电除尘器（布袋除尘）（ESP/FF）、湿法烟气脱硫系统（WFGD）等设备.提出了脱汞吸附剂处理问题,并对今后烟气脱汞技术的研究趋势进行了展望.     

Analysis of soil vapor extraction laboratory data to obtain equilibrium constants

A method of analyzing soil vapor extraction (SVE) laboratory data using a sample of contaminated soil is presented to allow the calculation of equilibrium constants for an assumed gas/soil equilibrium expression. The constants can be determined for any compound measured in the exit gas. A Freundlich equilibrium expression was shown to represent the equilibrium in a soil contaminated with trichloroethylene (TCE) and several aromatic solvents.     

Dynamic subsurface explosive vapor concentrations: Observations and implications

Conventional vapor intrusion characterization efforts can be challenging due to background indoor air constituents, preferential subsurface migration pathways, sampling access, and collection method limitations. While it has been recognized that indoor air concentrations are dynamic, until recently it was assumed by many practitioners that subsurface concentrations did not vary widely over time. Newly developed continuous monitoring platforms have been deployed to monitor subsurface concentrations of methane, carbon dioxide, oxygen, hydrogen sulfide, total volatile organic constituents, and atmospheric pressure. These systems have been integrated with telemetry, geographical information systems, and geostatistical algorithms for automatically generating two‐ and three‐dimensional contour images and time‐stamped renderings and playback loops of sensor attributes, and multivariate analyses through a cloud‐based project management platform. The objectives at several selected sites included continuous monitoring of vapor concentrations and related physical parameters to understand explosion risks over space and time and to then design a long‐term risk reduction strategy. High‐frequency data collection, processing, and automated visualization have resulted in greater understanding of natural processes, such as dynamic contaminant vapor intrusion risk conditions potentially influenced by localized barometric pumping. For instance, contemporaneous changes in methane, oxygen, and atmospheric pressure values suggest there is interplay and that vapor intrusion risk may not be constant. As a result, conventional single‐event and composite assessment technologies may not be capable of determining worst‐case risk scenarios in all cases, possibly leading to misrepresentation of receptor and explosion risks. While dynamic risk levels have been observed in several initial continuous monitoring applications, questions remain regarding whether these situations represent special cases and how best to determine when continuous monitoring should be required. Results from a selected case study are presented and implications derived. © 2011 Wiley Periodicals, Inc.     

Passive soil vapor extraction: A cost effectiveness study

An analysis of the cost effectiveness of passive soil vapor extraction (PSVE) is presented. PSVE, or “barometric pumping,” is an approach to the remediation of volatile organic compounds (VOCs) that seeks to harness and enhance the naturally occurring processes of wind and atmospheric pressure changes to facilitate the release of gas-phase contaminants from the subsurface. The technology background and current status are discussed, niches for the potential applicability of PSVE are identified, and a cost comparison with the conventional treatment method of active soil vapor extraction (ASVE) is examined.     

Electronic waste management approaches: An overview

Electronic waste (e-waste) is one of the fastest-growing pollution problems worldwide given the presence if a variety of toxic substances which can contaminate the environment and threaten human health, if disposal protocols are not meticulously managed. This paper presents an overview of toxic substances present in e-waste, their potential environmental and human health impacts together with management strategies currently being used in certain countries. Several tools including Life Cycle Assessment (LCA), Material Flow Analysis (MFA), Multi Criteria Analysis (MCA) and Extended Producer Responsibility (EPR) have been developed to manage e-wastes especially in developed countries. The key to success in terms of e-waste management is to develop eco-design devices, properly collect e-waste, recover and recycle material by safe methods, dispose of e-waste by suitable techniques, forbid the transfer of used electronic devices to developing countries, and raise awareness of the impact of e-waste. No single tool is adequate but together they can complement each other to solve this issue. A national scheme such as EPR is a good policy in solving the growing e-waste problems.     

Unprecedented Chitin and Chitosan: A Chemical Overview

Chitin and Chitosan are polysaccharide polymers. Polysaccharide is a carbohydrate whose molecules consist of a number of sugar molecules bonded together. It contains more than 5,000 acetylglucosamine and glucosamine (sugar) units, respectively and their molecular weights are over one million Daltons. Most of the naturally occurring polysaccharides are neutral or acidic in nature, whereas Chitin and Chitosan are examples of highly basic polysaccharides. Chitin is isolated from crab and shrimp waste and is a renewable resource. It is widely accepted that this biopolymer is an important biomaterial in many aspects. This review explores the various aspects of Chitin research.     

Team approaches to the development of innovative technologies and processes to facilitate remediation

The enactment of the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) created a complex liability scheme for owners, operators and prospective purchasers of contaminated properties, particularly brownfields. As the program developed, liability issues related to contiguous property, prospective purchasers, and no further action determinations became barriers to brownfield property redevelopment. The national effort on the cleanup and redevelopment of brownfield sites took on new emphasis with the passing of the federal “Small Business Liability Protection and Brownfields Revitalization Act” in January 2002. This new law provides liability clarifications as well as funding to facilitate the cleanup of brownfield sites. President Bush stated in his 2003 State of the Union address, “In this century, the greatest environmental progress will come about not through endless lawsuits or command‐and‐control regulations, but through technology and innovation.” The subject of this article is the Interstate Technology Regulatory Commission's Brownfield team, its current initiative, goals, and areas of special focus. © 2003 Wiley Periodicals, Inc.     

Aerobic Cometabolism of Halogenated Aliphatic Hydrocarbons: A Technology Overview

Bioremediation of chlorinated solvents has been moving from an innovative to mainstream technology for environmental applications. Cometablism of chlorinated solvents by monooxygenase has been demonstrated for trichloroethylene (TCE). Cl‐out microbes combine the dehalogenation of PCE with the monooxygenase destruction of TCE to complete the PCE breakdown pathway. Underthe right conditions, cometabolic bioremediation can be cost effective, fast, and complete. Aerobic bioremediation can augment mass transfer technologies such as pump and treat or sparging/vapor extraction to improve their efficiency.     

Water vapor permeability of biodegradable polymers

The water vapor transmission rates (WVTR) of several biodegradable polymers were evaluated to determine their suitability as water-resistant coatings and to understand WVTR better in terms of polymer structure. Values of WVTR at 25‡C ranged from 13 to 2900 g/m² /day and increased in the order PHBV PLA (cryst.) PLA (amorph.) PCL Bionolle BAK 1095 CAP CA. Values of WVTR were positively correlated with higher polymer solubility parameters, lower crystallinities, and higher free volumes. Although the WVTR of biodegradable polymers are much higher than those of good barrier materials such as low-density polyethylene, they are sufficient for short-term (hours to days) protection of polysaccharide-based materials against water. Product names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Treatment technology for remediation of wood preserving sites: Overview

This is the first in a series of five articles describing the applicability, performance, and cost of technologies for the remediation of contaminated soil and water at wood preserving sites. Site‐specific treatability studies conducted under the supervision of the United States Environmental Protection Agency (US EPA), National Risk Management Research Laboratory (NRMRL), from 1995 through 1997 constitute much of the basis for the evaluations presented, although data from other treatability studies, literature sources, and actual site remediations have also been included to provide a more comprehensive evaluation of remediation technologies. This article provides an overview of the wood preserving sites studied, including contaminant levels, and a summary of the performance of the technologies evaluated. The subsequent articles discuss the performance of each technology in more detail. Three articles discuss technologies for the treatment of soils, including solidification/stabilization, biological treatment, solvent extraction and soil washing. One article discusses technologies for the treatment of liquids, water and nonaqueous phase liquids (NAPLS), including biological treatment, carbon adsorption, photolytic oxidation, and hydraulic containment. The reader should be aware that other technologies including, but not limited to, incineration, thermal desorption, and base catalyzed dehalogenation, also have application for treating contaminants on wood preserving sites. They are not discussed in these five articles since the focus was to evaluate lesser known and hopefully lower cost approaches. However, the reader should include consideration of these other technologies as part of any evaluation or screening of technologies applicable to remediation of wood preserving sites.     

Systems approaches to integrated solid waste management in developing countries

Solid waste management (SWM) has become an issue of increasing global concern as urban populations continue to rise and consumption patterns change. The health and environmental implications associated with SWM are mounting in urgency, particularly in the context of developing countries. While systems analyses largely targeting well-defined, engineered systems have been used to help SWM agencies in industrialized countries since the 1960s, collection and removal dominate the SWM sector in developing countries. This review contrasts the history and current paradigms of SWM practices and policies in industrialized countries with the current challenges and complexities faced in developing country SWM. In industrialized countries, public health, environment, resource scarcity, climate change, and public awareness and participation have acted as SWM drivers towards the current paradigm of integrated SWM. However, urbanization, inequality, and economic growth; cultural and socio-economic aspects; policy, governance, and institutional issues; and international influences have complicated SWM in developing countries. This has limited the applicability of approaches that were successful along the SWM development trajectories of industrialized countries. This review demonstrates the importance of founding new SWM approaches for developing country contexts in post-normal science and complex, adaptive systems thinking.     

Introduction/Overview to In Situ Burning of Oil Spills

In situ burning is an oil spill response technique or tool that involves the controlled ignition and burning of the oil at or near the spill site on the surface of the water or in a marsh (see Lindau et al., this volume). Although controversial, burning has been shown on several recent occasions to be an appropriate oil spill countermeasure. When used early in a spill before the oil weathers and releases its volatile components, burning can remove oil from the waters surface very efficiently and at very high rates. Removal efficiencies for thick slicks can easily exceed 95% (Advanced In Situ Burn Course, Spiltec, Woodinville, WA, 1997). In situ burning offers a logistically simple, rapid, inexpensive and if controlled a relatively safe means for reducing the environmental impacts of an oil spill. Because burning rapidly changes large quantities of oil into its primary combustion products (water and carbon dioxide), the need for collection, storage, transport and disposal of recovered material is greatly reduced. The use of towed fire containment boom to capture, thicken and isolate a portion of a spill, followed by ignition, is far less complex than the operations involved in mechanical recovery, transfer, storage, treatment and disposal (The Science, Technology, and Effects of Controlled Burning of Oil Spills at Sea, Marine Spill Response Corporation, Washington, DC, 1994).However, there is a limited window-of-opportunity (or time period of effectiveness) to conduct successful burn operations. The type of oil spilled, prevailing meteorological and oceanographic (environmental) conditions and the time it takes for the oil to emulsify define the window (see Buist, this volume and Nordvik et al., this volume). Once spilled, oil begins to form a stable emulsion: when the water content exceeds 25% most slicks are unignitable. In situ burning is being viewed with renewed interest as a response tool in high latitude waters where other techniques may not be possible or advisable due to the physical environment (extreme low temperatures, ice-infested waters), or the remoteness of the impacted area. Additionally, the magnitude of the spill may quickly overwhelm the deployed equipment necessitating the consideration of other techniques in the overall response strategy (The Science, Technology, and Effects of Controlled Burning of Oil Spills at Sea, Marine Spill Response Corporation, Washington, DC, 1994; Proceedings of the In Situ Burning of Oil Spills Workshop. NIST. SP934. MMS. 1998, p. 31; Basics of Oil Spill Cleanup, Lewis Publishers, Washington, DC, 2001, p. 233). This paper brings together the current knowledge on in situ burning and is an effort to gain regulatory acceptance for this promising oil spill response tool.     

Correlation between physicochemical and ecotoxicological approaches to estimate landfill leachates toxicity

Leachates from municipal solid waste (MSW) landfills may contain a huge diversity of contaminants; these wastewaters should be considered as potentially hazardous complex mixtures, representing a potential environmental risk for surface and groundwater. Current MSW landfill wastes regulatory approaches deem exclusively on the physicochemical characterization and does not contemplate the ecotoxicological assessment of landfill leachates. However, the presence of highly toxic substances in consumer products requires reconsideration on the need of more specific ecotoxicological assessments. The main aim of this study was to evaluate the toxicity of different MSW landfill leachates using a battery of toxicity tests including acute toxicity tests with Daphnia magna and the anuran Xenopus laevis and the in vitro toxicity test with the fish cell line RTG-2. The additional objective was to study the possible correlation between physicochemical properties and the toxicity results obtained for untreated landfill leachates. The results showed that the proposed test battery was effective for the ecotoxicological characterization of MSW landfill leachates. A moderate to strong correlation between the measured physicochemical parameters and the calculated toxicity units was detected for all toxicity assays. Correlation factors of 0.85, 0.86 and 0.55 for Daphnia, Xenopus and RTG-2 tests, respectively, were found. The discriminant analysis showed that certain physicochemical parameters could be used for an initial categorization of the potential aquatic acute toxicity of leachates; this finding may facilitate leachates management as the physicochemical characterization is currently the most common or even only monitoring method employed in a large majority of landfills. Ammonia, alkalinity and chemical oxygen demand (COD), together with chloride, allowed a proper categorization of leachates toxicity for up to 75% of tested samples, with a small percentage of false negatives.