Finding new sources of water for semi-arid cities in unlikely places

Environmental Science and Pollution Research - Determining alternative water sources to meet municipal water demands is important when availability is limited. The purpose of this study was to...     

Zerovalent iron nanoparticles for treatment of ground water contaminated by hexachlorocyclohexanes

Ground water and aquifer samples from a site contaminated by hexachlorocyclohexanes (HCHs; C(6)H(6)Cl(6)) were exposed to nanoscale iron particles to evaluate the technology as a potential remediation method. The summed concentration of the HCH isomers in ground water was approximately 5.16 micromol L(-1) (1500 microg L(-1)). Batch experiments with 2.2 to 27.0 g L(-1) iron nanoparticles showed that more than 95% of the HCHs were removed from solution within 48 h. Using a pseudo first-order kinetics model, the HCH isomers were removed in accordance with the trend gamma congruent with alpha > beta > delta. This seems to be correlated with the orientation (axial vs. equatorial) of the chlorine atoms lost in the dihaloelimination steps. Although the reactivity of the HCH isomers has been investigated in the classical organic chemistry literature, the present study was the first in the environmental remediation arena. The rate of removal is directly correlated to the number of axial chlorines. The observed rate constant varied from 0.04 to 0.65 h(-1), and the rate constant normalized to the iron surface area concentration ranged from 5.4 x 10(-4) to 8.8 x 10(-4) L m(-2) h(-1). Post-test extractions of the reactor contents detected little HCH remaining in solution or on the iron surfaces, reinforcing the contention that reaction rather than sorption was the operative mechanism for the HCH removal. Together with previously published work on a wide variety of chlorinated organic solvents, this work further demonstrates the potential of zerovalent iron nanoparticles for treatment and remediation of persistent organic pollutants.     

Concentrations of polychlorinated biphenyls (PCBs) in water, sediment, and aquatic biota in the Houston Ship Channel, Texas

Polychlorinated biphenyls (PCBs) were quantified in water, sediment, and catfish and crab tissue collected from the Houston Ship Channel (HSC) in Texas. The total concentrations of the 209 PCB congeners ranged from 0.49 to 12.49 ng l(-1), 4.18 to 4601 ng g(-1) dry wt, 4.13 to 1596 ng g(-1) wet wt, and 3.44 to 169 ng g(-1) wet wt, in water, sediment, catfish and crab tissue, respectively. All media showed maximum concentrations greater than studies in other regions with the highest concentrations occurring in the most industrialized segments of the channel. Inter-media correlations suggested that sediment is a source to water. Galveston Bay sediment concentrations compared to a previous study showed a declining trend though the rate of the decline may be slowing. Detailed homolog profiles revealed that the industrialized part of the channel may be receiving PCB-laden sediment from its tributaries. An unusually high fraction of the deca-chlorinated congener (PCB-209) was found in all media. Seen in only a few other studies and in previous air concentrations in the channel, this may point to unusual Aroclor mixtures used in the history of the HSC or to contemporary sources from local industry. A comparison of PCB concentrations obtained using Aroclor, representative congener, and all congener methods, indicated that Aroclors are not an appropriate surrogate for total PCBs and that the NOAA NST method is more representative than the NOAA EPA method.     

Risk perception, risk management and vulnerability to landslides in the hill slopes in the city of La Paz, Bolivia. A preliminary statement

The article begins by describing the difficult living conditions of many people in the hill slopes (laderas) of La Paz, Bolivia, demonstrating that they are exposed to a combination of natural and social hazards. ¹ It shows that residents, community leaders and city planners tend to underestimate or deny risk, with important consequences for risk management, such as a failure to raise risk awareness. The article then proposes some hypotheses to explain risk perceptions in La Paz, discarding the usual single-approach interpretations and suggesting instead more nuanced theoretical explanations to account for why people build their homes in such hazardous environments.     

Comparison of regression coefficient and GIS-based methodologies for regional estimates of forest soil carbon stocks

Estimates of forest soil organic carbon (SOC) have applications in carbon science, soil quality studies, carbon sequestration technologies, and carbon trading. Forest SOC has been modeled using a regression coefficient methodology that applies mean SOC densities (mass/area) to broad forest regions. A higher resolution model is based on an approach that employs a geographic information system (GIS) with soil databases and satellite-derived landcover images. Despite this advancement, the regression approach remains the basis of current state and federal level greenhouse gas inventories. Both approaches are analyzed in detail for Wisconsin forest soils from 1983 to 2001, applying rigorous error-fixing algorithms to soil databases. Resulting SOC stock estimates are 20% larger when determined using the GIS method rather than the regression approach. Average annual rates of increase in SOC stocks are 3.6 and 1.0 million metric tons of carbon per year for the GIS and regression approaches respectively.     

Subterranean freshwater gastropod biodiversity and conservation in the United States and Mexico

Many taxonomic groups successfully exploit groundwater environments and have adapted to a subterranean (stygobiotic) existence. Among these groups are freshwater gastropods (stygosnails), which represent a widespread and taxonomically diverse component of groundwater ecosystems in North America. However, owing to sampling difficulty and lack of targeted study, stygosnails remain among the most understudied of all subterranean groups. We conducted a literature review to assess the biodiversity and geographic associations of stygosnails, along with the threats, management activities, and policy considerations related to the groundwater systems they inhabit. We identified 39 stygosnail species known to occur in a range of groundwater habitats from karst regions in the United States and Mexico. Most stygosnails exhibit extreme narrow-range endemism, resulting in a high risk of extinction from a single catastrophic event. We found that anthropogenically driven changes to surface environments have led to changes in local hydrology and degradation of groundwater systems inhabited by stygosnails such as increased sedimentation, introduction of invasive species, groundwater extraction, or physical collapse of water-bearing passages. Consequently, 32 of the 39 described stygosnail species in the United States and Mexico have been assessed as imperiled under NatureServe criteria, and 10 species have been assessed as threatened under International Union for Conservation of Nature criteria. Compared with surface species of freshwater snails, stygosnail conservation is uniquely hindered by difficulties associated with accessing subterranean habitats for monitoring and management. Furthermore, only three species were found to have federal protection in either the United States or Mexico, and current laws regulating wildlife and water pollution at the state and federal level may be inadequate for protecting stygosnail habitats. As groundwater systems continue to be manipulated and relied on by humans, groundwater-restricted fauna such as stygosnails should be studied so unique biodiversity can be protected.     

Parasites as conservation tools

Parasite success typically depends on a close relationship with one or more hosts; therefore, attributes of parasitic infection have the potential to provide indirect details of host natural history and are biologically relevant to animal conservation. Characterization of parasite infections has been useful in delineating host populations and has served as a proxy for assessment of environmental quality. In other cases, the utility of parasites is just being explored, for example, as indicators of host connectivity. Innovative studies of parasite biology can provide information to manage major conservation threats by using parasite assemblage, prevalence, or genetic data to provide insights into the host. Overexploitation, habitat loss and fragmentation, invasive species, and climate change are major threats to animal conservation, and all of these can be informed by parasites.