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.

     

Building pressure control test to examine if VOC contamination in indoor air is caused by an interior source or by a subslab source

When determining whether or not remediation of subslab contamination is warranted, it is often important to know if the presence of volatile organic compounds (VOCs) in indoor air is caused primarily by interior sources, or primarily by subslab contamination. With a Building Pressure Control test, the pressure differential across the building envelope and, thereby, also the pressure differential across the slab, can be controlled by a blower. By measuring the indoor air concentrations of VOCs under depressurization (upward pressure gradient over the slab) and under pressurization (downward pressure gradient over the slab), it can be determined if the subslab contamination contributes significantly to the VOC concentrations in indoor air. This technique has been applied at several sites in the Central Denmark Region, and the results show that a Building Pressure Control test is a quick and effective method to examine if VOC contamination in indoor air is caused primarily by interior sources or primarily by subslab sources. With numerous measurement points in the indoor air, at some sites this test method has identified the area where the subslab contamination is located. A pressure differential at ?5/+5 Pa across the building envelope was sufficient at all the test sites to control the pressure gradient across the slab to be uniquely upward/downward.     

Biodegradation of triclosan and formation of methyl-triclosan in activated sludge under aerobic conditions

Triclosan is an antimicrobial agent which is widely used in household and personal care products. Widespread use of this compound has led to the elevated concentrations of triclosan in wastewater, wastewater treatment plants (WWTPs) and receiving waters. Removal of triclosan and formation of triclosan-methyl was investigated in activated sludge from a standard activated sludge WWTP equipped with enhanced biological phosphorus removal. The removal was found to occur mainly under aerobic conditions while under anoxic (nitrate reducing) and anaerobic conditions rather low removal rates were determined. In a laboratory-scale activated sludge reactor 75% of the triclosan was removed under aerobic conditions within 150 h, while no removal was observed under anaerobic or anoxic conditions. One percent of the triclosan was converted to triclosan-methyl under aerobic conditions, less under anoxic (nitrate reducing) and none under anaerobic conditions.     

Will PM control undermine China's efforts to reduce soil acidification?

China’s strategies to control acidifying pollutants and particulate matter (PM) may be in conflict for soil acidification abatement. Acidifying pollutant emissions are estimated for 2005 and 2020 with anticipated control policies. PM emissions including base cations (BCs) are evaluated with two scenarios, a base case applying existing policy to 2020, and a control case including anticipated tightened measures. Depositions of sulfur (S), nitrogen (N) and BCs are simulated and their acidification risks are evaluated with critical load (CL). In 2005, the area exceeding CL covered 15.6% of mainland China, with total exceedance of 2.2 Mt S. These values decrease in the base scenario 2020, implying partial recovery from acidification. Under more realistic PM control, the respective estimates are 17.9% and 2.4 Mt S, indicating increased acidification risks due to abatement of acid-neutralizing BCs. China’s anthropogenic PM abatement will have potentially stronger chemical implications for acidification than developed countries.     

Promise and performance of agricultural nutrient management policy: Lessons from the Baltic Sea

Following decades of international collaboration to restore the Baltic Sea, we provide an assessment of the domestic implementation of measures agreed to limit diffuse agricultural pollution and the patterns of policy instruments applied. Despite the Helsinki Convention being unusually specific in detailing what measures countries should introduce, we find many shortcomings. These are most pronounced in the larger countries (Poland, Germany and Russia), while smaller countries perform better, notably Sweden and Estonia. The patterns of policy instruments applied differ, influenced by domestic politics. The limited use of complementary policy instruments suggests that other priorities overrule full and effective implementation, with engagement mirroring the advantages that a restored Baltic Sea can bring to countries. Using the European Agricultural Fund for Rural Development to support farmers in managing nutrients, particularly advisory services and investments in modern manure management technologies, represents a significant opportunity for reducing agricultural pollution in most countries.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01549-3.     

The potential of willow for remediation of heavy metal polluted calcareous urban soils

Growth performance and heavy metal uptake by willow (Salix viminalis) from strongly and moderately polluted calcareous soils were investigated in field and growth chamber trials to assess the suitability of willow for phytoremediation. Field uptakes were 2-10 times higher than growth chamber uptakes. Despite high concentrations of cadmium (≥80 mg/kg) and zinc (≥3000 mg/kg) in leaves of willow grown on strongly polluted soil with up to 18 mg Cd/kg, 1400 mg Cu/kg, 500 mg Pb/kg and 3300 mg Zn/kg, it is unsuited on strongly polluted soils because of poor growth. However, willow proved promising on moderately polluted soils (2.5 mg Cd/kg and 400 mg Zn/kg), where it extracted 0.13% of total Cd and 0.29% of the total Zn per year probably representing the most mobile fraction. Cu and Pb are strongly fixed in calcareous soils.     

Painted surfaces--important sources of polychlorinated biphenyls (PCBs) contamination to the urban and marine environment

A study of a large number of samples of flaking old paint from various buildings in Bergen, Norway (N = 68) suggests that paint may be the most important contemporary source of PCBs in this urban environment with concentrations of PCB₇ up to 3.39 g/kg. Twenty-three of the samples were collected from a single building, and the concentrations were found to vary over 3 orders of magnitude. In addition, 16 concrete samples from a large bridge previously coated with PCB-containing paint were collected and separated into outer- and inner samples indicating that PCBs are still present in high concentrations subsequent to renovation. PCBs were found in several categories of paint from wooden and concrete buildings, potentially introduced to the environment by natural weathering, renovation, and volatilization. Consequently, this dispersion may lead to increased levels of PCBs in urban atmospheres, soils, and harbor sediments where high concentrations have resulted in Governmental advice against consumption of certain seafood.     

The influence of cosolvent and heat on the solubility and reactivity of organophosphorous pesticide DNAPL alkaline hydrolysis

The presented research concerned the compatibility of cosolvents with in situ alkaline hydrolysis (ISAH) for treatment of organophosphorous (OPP) pesticide contaminated sites. In addition, the influence of moderate temperature heat increments was studied as a possible enhancement method. A complex dense non-aqueous phase liquid (DNAPL) of primarily parathion (~50 %) and methyl parathion (~15 %) obtained from the Danish Groyne 42 site was used as a contaminant source, and ethanol and propan-2-ol (0, 25, and 50 v/v%) was used as cosolvents in tap water and 0.34 M NaOH. Both cosolvents showed OPP solubility enhancement at 50 v/v% cosolvent content, with slightly higher OPP concentrations reached with propan-2-ol. Data on hydrolysis products did not show a clear trend with respect to alkaline hydrolysis reactivity in the presence of cosolvents. Results indicated that the hydrolysis rate of methyl-parathion (MP3) decreased with addition of cosolvent, whereas the hydrolysis rate of ethyl-parathion (EP3) remained constant, and overall indications were that the hydrolysis reactions were limited by the rate of hydrolysis rather than NAPL dissolution. In addition to cosolvents, the influence of low-temperature heating on ISAH was studied. Increasing reaction temperature from 10 to 30 °C provided an average rate of hydrolysis enhancement by a factor of 1.4–4.8 dependent on the base of calculation. When combining 50 v/v% cosolvent addition and heating to 30 °C, EP3 solubility was significantly enhanced and results for O,O-diethyl-thiophosphoric acid (EP2 acid) showed a significant enhancement of hydrolysis as well. However, this could not be supported by para-nitrophenol (PNP) data indicating the instability of this product in the presence of cosolvent.

     

Results of Community Deliberation About Social Impacts of Ecological Restoration: Comparing Public Input of Self-Selected Versus Actively Engaged Community Members

Participatory processes for obtaining residents' input about community impacts of proposed environmental management actions have long raised concerns about who participates in public involvement efforts and whose interests they represent. This study explored methods of broad-based involvement and the role of deliberation in social impact assessment. Interactive community forums were conducted in 27 communities to solicit public input on proposed alternatives for recovering wild salmon in the Pacific Northwest US. Individuals identified by fellow residents as most active and involved in community affairs ("AE residents") were invited to participate in deliberations about likely social impacts of proposed engineering and ecological actions such as dam removal. Judgments of these AE participants about community impacts were compared with the judgments of residents motivated to attend a forum out of personal interest, who were designated as self-selected ("SS") participants. While the magnitude of impacts rated by SS participants across all communities differed significantly from AE participants' ratings, in-depth analysis of results from two community case studies found that both AE and SS participants identified a large and diverse set of unique impacts, as well as many of the same kinds of impacts. Thus, inclusion of both kinds of residents resulted in a greater range of impacts for consideration in the environmental impact study. The case study results also found that the extent to which similar kinds of impacts are specified by AE and SS group members can differ by type of community. Study results caution against simplistic conclusions drawn from this approach to community-wide public participation. Nonetheless, the results affirm that deliberative methods for community-based impact assessment involving both AE and SS residents can provide a more complete picture of perceived impacts of proposed restoration activities.     

Regional Management of Farmland Feeding Geese Using an Ecological Prioritization Tool

Wild geese foraging on farmland cause increasing conflicts with agricultural interests, calling for a strategic approach to mitigation. In central Norway, conflicts between farmers and spring-staging pink-footed geese feeding on pastures have escalated. To alleviate the conflict, a scheme by which farmers are subsidized to allow geese to forage undisturbed was introduced. To guide allocation of subsidies, an ecological-based ranking of fields at a regional level was recommended and applied. Here we evaluate the scheme. On average, 40 % of subsidized fields were in the top 5 % of the ranking, and 80 % were within the top 20 %. Goose grazing pressure on subsidized pastures was 13 times higher compared to a stratified random selection of non-subsidized pastures, capturing 67 % of the pasture feeding geese despite that subsidized fields only comprised 13 % of the grassland area. Close dialogue between scientists and managers is regarded as a key to the success of the scheme.