Managing Excessive Methanogenesis During ERD/ISCR Remedial Action

Excessive production of methane has been observed at some remediation sites following the addition of organic hydrogen donors such as (emulsified) oils/lecithin, sugars, and conventional carbon + zero‐valent iron (ZVI) amendments. This is due to the fact that methanogens are commonly the most ubiquitous indigenous microbes in anoxic aquifer settings, and, under enriched environmental conditions, methanogens replicate every one to two hours (whereas Dehalococcoides spp., e.g., double in 24–48 hr). Hence, methanogens often bloom and dominate the microbial ecosystem following the addition of remedial amendments, thereby liberating large amounts of methane gas. There are at least three important consequences of this response:

1. By utilizing hydrogen, the methanogens compete with dechlorinating microbes, thus making inefficient use of the remedial amendment (just 20 ppm methane in groundwater represents an approximate 30 percent “waste” of added fermentable substrate (i.e., hydrogen donor)—this is a common and tangible detriment);
2. Methanogens can methylate heavy metals and their rapid growth consumes alkalinity, while generating acidity, thereby facilitating multiple potential mechanisms for creating secondary contaminant issues (i.e., arsenic plumes); and
3. Elevated methane concentrations can exceed current and pending regulations of <10 to <28 ppm methane in groundwater and/or 0.5 percent by volume methane in soil gas (e.g., 10 percent of the lower explosive limit) and/or indoor air (methane is flammable between 5 percent and 15 percent by volume) and this will induce migration of contaminant vapors potentially causing indoor air issues.

Considering the recent guidelines for indoor air published by the US Environmental Protection Agency, it is increasingly important to prevent excessive methanogenesis associated with remedial actions. From a regulatory perspective, public safety issues are paramount; from a property re‐use or real estate (brownfield) developers’ perspective, project delays are costly and can jeopardize an entire program. The use of antimethanogenic compounds as inhibitors of protein biosynthesis and the activity of enzyme systems unique to Archaea (i.e., methanogens) during in situ remedial action can improve contaminant removal while offering safer, more efficacious treatment, simply by impeding the methanogenic bacteria's ability to proliferate and out compete desired bacterial communities (e.g., Dehalococcoides spp.). ©2016 Wiley Periodicals, Inc.     

Cellular arsenic transport pathways in mammals

Natural contamination of drinking water with arsenic results in the exposure of millions of people world-wide to unacceptable levels of this metalloid. This is a serious global health problem because arsenic is a Group 1 (proven) human carcinogen and chronic exposure is known to cause skin, lung, and bladder tumors. Furthermore, arsenic exposure can result in a myriad of other adverse health effects including diseases of the cardiovascular, respiratory, neurological, reproductive, and endocrine systems. In addition to chronic environmental exposure to arsenic, arsenic trioxide is approved for the clinical treatment of acute promyelocytic leukemia, and is in clinical trials for other hematological malignancies as well as solid tumors. Considerable inter-individual variability in susceptibility to arsenic-induced disease and toxicity exists, and the reasons for such differences are incompletely understood. Transport pathways that influence the cellular uptake and export of arsenic contribute to regulating its cellular, tissue, and ultimately body levels. In the current review, membrane proteins (including phosphate transporters, aquaglyceroporin channels, solute carrier proteins, and ATP-binding cassette transporters) shown experimentally to contribute to the passage of inorganic, methylated, and/or glutathionylated arsenic species across cellular membranes are discussed. Furthermore, what is known about arsenic transporters in organs involved in absorption, istribution, and metabolism and how transport pathways contribute to arsenic elimination are described.     

The Role of Women in Water Management and Conflict Resolution in Marsabit,Kenya

We employed qualitative methods to explore how conflict over water collection and use impacts women, and the role that women play in water management and conflict resolution in Marsabit, Kenya. Conflicts between domestic and livestock water led to insufficient water for domestic use and intra-household conflict. Women’s contributions to water management were valued, especially through informal initiatives, though involvement in statutory water management committees was not culturally appropriate. Promoting culturally appropriate ways to involve women in water management, rather than merely increasing the percentage of women on water committee, may reduce conflicts and increase women’s access to domestic water supplies.     

Can home gardens scale up into movements for social change? The role of home gardens in providing food security and community change in San Jose,California

Urban policymakers and sustainable food activists have identified urban agriculture as an important strategy for confronting a host of urban problems, including food insecurity, health disparities, access to urban green space and community economic revitalisation. Much recent work on urban agriculture has examined community and school gardens, but little research has been undertaken on home gardens as a solution to urban problems. This article examines a home-gardening programme in San Jose, California, La Mesa Verde, asking whether some of the benefits found in community gardens can be found in home gardens. Specifically, we look at financial, health and community benefits, examining the potential of home gardens to become forces for broader social change. We ask whether gardens can become agents of cultural preservation, self-determination, particularly for recent immigrants who use these spaces to build identities and work towards collective action and self-determination.     

Perchlorate in fish from a contaminated site in east-central Texas

Perchlorate, a known thyroid endocrine disruptor, contaminates surface waters near military instillations where solid fuel rocket motors are manufactured or assembled. To assess potential perchlorate exposure to fish and the human population which may feed on them, fish were collected around the Naval Weapons Industrial Reserve Plant in McLennan County, TX, and analyzed for the presence of the perchlorate anion. The sampling sites included Lake Waco and Belton Lake, and several streams and rivers within their watersheds. The general tendency was that perchlorate was only found in a few species sampled, and perchlorate was not detected in every individual within these species. When detected in the fish, perchlorate tissue concentrations were greater than that in the water. This may be due to highly variable perchlorate concentrations in the water coupled with individual-level variation in elimination from the body, or to routes of exposure other than water.     

Using a systems approach to improve process and environmental performance

By providing companies with a set of analytical tools, the systems approach allows decision makers to achieve the elusive goal of continuous environmental improvement. © 2000 John Wiley & Sons, Inc.     

Human disturbance and shifts in vertebrate community composition in a biodiversity hotspot

Understanding how human modification of the landscape shapes vertebrate community composition is vital to understanding the current status and future trajectory of wildlife. Using a participatory approach, we deployed the largest camera-trap network in Mesoamerica to date to investigate how anthropogenic disturbance shapes the occupancy and co-occurrence of terrestrial vertebrate species in a tropical biodiversity hotspot: the Osa Peninsula, Costa Rica. We estimated species richness in different categories of land protection with rarefaction analysis and estimated the expected occupancy with a joint species distribution model that included covariates for anthropogenic disturbance, land protection, habitat quality, and habitat availability. Areas with the most stringent land-use protections (e.g., Corcovado National Park, 24 species [95% CI 23–25]) harbored significantly more species than unprotected areas (20 species [19.7–20.3]), mainly due to a reduced presence of large-bodied species of conservation concern in unprotected areas (e.g., jaguar Panthera onca and white-lipped peccary Tayassu pecari). Small-bodied generalist species, such as opossums (Didelphidae) and armadillos (Dasypus novemcinctus), in contrast, were more common at disturbed sites, resulting in a significant difference in vertebrate community composition between sites with low and high disturbance. Co-occurrence of species was also mainly associated with response to disturbance. Similar responses to disturbance create two groups of species, those whose site-level occupancy usually increased as anthropogenic disturbance increased and those whose estimated occupancy decreased. The absence of large-bodied species entails an important loss of ecological function in disturbed areas and can hinder forest development and maintenance. Efforts to protect and restore forested landscapes are likely having a positive effect on the abundance of some threatened species. These efforts, however, must be sustained and expanded to increase connectivity and ensure the long-term viability of the wildlife community.     

Global rarity of intact coastal regions

Management of the land–sea interface is essential for global conservation and sustainability objectives because coastal regions maintain natural processes that support biodiversity and the livelihood of billions of people. However, assessments of coastal regions have focused strictly on either the terrestrial or marine realm. Consequently, understanding of the overall state of Earth's coastal regions is poor. We integrated the terrestrial human footprint and marine cumulative human impact maps in a global assessment of the anthropogenic pressures affecting coastal regions. Of coastal regions globally, 15.5% had low anthropogenic pressure, mostly in Canada, Russia, and Greenland. Conversely, 47.9% of coastal regions were heavily affected by humanity, and in most countries (84.1%) >50% of their coastal regions were degraded. Nearly half (43.3%) of protected areas across coastal regions were exposed to high human pressures. To meet global sustainability objectives, all nations must undertake greater actions to preserve and restore the coastal regions within their borders.