Development of Layered Sediment Structure and its Effects on Pore Water Transport and Hyporheic Exchange

Hyporheic exchange is known to provide an important control on nutrient and contaminant fluxes across the stream-subsurface interface. Similar processes also mediate interfacial transport in other permeable sediments. Recent research has focused on understanding the mechanics of these exchange processes and improving estimation of exchange rates in natural systems. While the structure of sediment beds obviously influences pore water flow rates and patterns, little is known about the interplay of typical sedimentary structures, hyporheic exchange, and other transport processes in fluvial/alluvial sediments. Here we discuss several processes that contribute to local-scale sediment heterogeneity and present results that illustrate the interaction of overlying flow conditions, the development of sediment structure, pore water transport, and stream-subsurface exchange. Layered structures are shown to develop at several scales within sediment beds. Surface sampling is used to analyze the development of an armor layer in a sand-and-gravel bed, while innovative synchrotron-based X-ray microtomography is used to observe patterns of grain sorting within sand bedforms. We show that layered bed structures involving coarsening of the bed surface increase interfacial solute flux but produce an effective anisotropy that favors horizontal pore water transport while limiting vertical penetration.     

Control of invasive rats on islands and priorities for future action

Invasive rats are one of the world's most successful animal groups that cause native species extinctions and ecosystem change, particularly on islands. On large islands, rat eradication is often impossible and population control, defined as the local limitation of rat abundance, is now routinely performed on many of the world's islands as an alternative management tool. However, a synthesis of the motivations, techniques, costs, and outcomes of such rat‐control projects is lacking. We reviewed the literature, searched relevant websites, and conducted a survey via a questionnaire to synthesize the available information on rat‐control projects in island natural areas worldwide to improve rat management and native species conservation. Data were collected from 136 projects conducted over the last 40 years; most were located in Australasia (46%) and the tropical Pacific (25%) in forest ecosystems (65%) and coastal strands (22%). Most of the projects targeted Rattus rattus and most (82%) were aimed at protecting birds and endangered ecosystems. Poisoning (35%) and a combination of trapping and poisoning (42%) were the most common methods. Poisoning allows for treatment of larger areas, and poison projects generally last longer than trapping projects. Second‐generation anticoagulants (mainly brodifacoum and bromadiolone) were used most often. The median annual cost for rat‐control projects was US$17,262 or US$227/ha. Median project duration was 4 years. For 58% of the projects, rat population reduction was reported, and 51% of projects showed evidence of positive effects on biodiversity. Our data were from few countries, revealing the need to expand rat‐control distribution especially in some biodiversity hotspots. Improvement in control methods is needed as is regular monitoring to assess short‐ and long‐term effectiveness of rat‐control.     

The data not collected on community forestry

Conservation and development practitioners increasingly promote community forestry as a way to conserve ecosystem services, consolidate resource rights, and reduce poverty. However, outcomes of community forestry have been mixed; many initiatives failed to achieve intended objectives. There is a rich literature on institutional arrangements of community forestry, but there has been little effort to examine the role of socioeconomic, market, and biophysical factors in shaping both land‐cover change dynamics and individual and collective livelihood outcomes. We systematically reviewed the peer‐reviewed literature on community forestry to examine and quantify existing knowledge gaps in the community‐forestry literature relative to these factors. In examining 697 cases of community forest management (CFM), extracted from 267 peer‐reviewed publications, we found 3 key trends that limit understanding of community forestry. First, we found substantial data gaps linking population dynamics, market forces, and biophysical characteristics to both environmental and livelihood outcomes. Second, most studies focused on environmental outcomes, and the majority of studies that assessed socioeconomic outcomes relied on qualitative data, making comparisons across cases difficult. Finally, there was a heavy bias toward studies on South Asian forests, indicating that the literature on community forestry may not be representative of decentralization policies and CFM globally.     

Essential and non-essential element concentrations in two sleeper shark species collected in arctic waters

A number of elements/metals have increased in arctic biota and are of concern due to their potential toxicity. Most studies on elements in the Arctic have focused on marine mammals and seabirds, but concentrations in the Greenland shark (Somniosus microcephalus) and Pacific sleeper shark (Somniosus pacificus), the only two shark species known to regularly inhabit arctic waters, have never been reported. To address this data gap, concentrations and patterns of 25 elements were analyzed in liver of Greenland sharks collected about Cumberland Sound (n=24) and Pacific sleeper sharks collected about Prince William Sound (n=14). Several non-essential elements differed between species/locations, which could suggest geographical exposure differences or ecological (e.g., diet) differences between the species. Certain essential elements also differed between the two sleeper sharks, which may indicate different physiological requirements between these closely related shark species, although information on such relationships are lacking for sharks and fish.     

The search for an alternative to piped water and sewer systems in the Alaskan Arctic

Forty-two communities in rural Alaska are considered unserved or underserved with water and sewer infrastructure. Many challenges exist to provide centralized piped water and sewer infrastructure to the homes, and they are exacerbated by decreasing capital funding. Unserved communities in rural Alaska experience higher rates of disease, supporting the recommendation that sanitation infrastructure should be provided. Organizations are pursuing alternative solutions to conventional piped water and sewer in order to maximize water use and reuse for public health. This paper reviews initiatives led by the State of Alaska, the Alaska Native Tribal Health Consortium, and the Yukon Kuskokwim Health Corporation to identify and develop potential long-term solutions appropriate and acceptable to rural communities. Future developments will likely evolve based on the lessons learned from the initiatives. Recommendations include Alaska-specific research needs, increased end-user participation in the design process, and integrated monitoring, evaluation, and information dissemination in future efforts.     

Spatial and seasonal variations in atrazine and metolachlor surface water concentrations in Ontario (Canada) using ELISA

Concerns regarding the impacts of pesticides on aquatic species and drinking water sources have increased demands on water quality monitoring programs; however the costs of sample analysis can be prohibitive. In this study we investigated enzyme-linked immunosorbent assay (ELISA) as a cost-effective, high through-put method for measuring pesticide concentrations in surface waters. Seven hundred and thirty-nine samples from 158 locations throughout Ontario were analysed for atrazine and metolachlor from April to October 2007. Concentrations ranged from <0.1 to 3.91 μg L⁻¹ (median = 0.12 μg L⁻¹) for atrazine and from <0.1 to 1.83 μg L⁻¹ (median = 0.09 μg L⁻¹) for metolachlor. Peak concentrations occurred in late spring/early summer, in rural agricultural locations, and decreased over the remainder of the growing season for both herbicides. About 3% of the samples that had ELISA results occurring above the limit of quantification (0.10 μg L⁻¹) were evaluated against gas chromatography-mass spectrometry (GC-MS). Linear regression analysis revealed a R² value of 0.88 and 0.39, for atrazine and metolachlor, respectively. ELISA tended to overestimate concentrations for atrazine and metolachlor, most likely because the ELISA kits also detect their metabolites. Atrazine data suggest that ELISA may be used complementary with GC-MS analysis to enhance the spatial and temporal resolution of a water quality monitoring study. The commercially available metolachlor ELISA kit requires further investigation. ELISA may be used to detect atrazine and metolachlor in surface water samples, but it is not recommended as a quantitative replacement for traditional analytical methods.     

Photophysical and photochemical properties of the pharmaceutical compound salbutamol in aqueous solutions

Salbutamol is a potent β₂-adrenergic receptor agonist widely used in the treatment of bronchial asthma and chronic obstructive pulmonary disease. An increasing number of studies have detected salbutamol in natural water systems worldwide. Studies have shown that sunlight degrades salbutamol resulting in the formation of products; some showing higher toxicity to bacteria Vibrio fischeri than the parent compound. In this contribution, steady-state absorption and emission techniques, high-performance liquid chromatography, and transient absorption spectroscopy are used to investigate the photochemistry of salbutamol in aqueous buffer solutions at controlled pH values. Ground- and excited-state calculations that include solvent effects are performed to guide the interpretation of the experimental results. Salbutamol is sensitive to UVB light absorption in the pH range from 3 to 12, forming products that absorb light at longer wavelengths than the parent compound. Quantum yields of degradation reveal that the deprotonated species is 10-fold more photo-active than the protonated species. In line with this result, the fluorescence quantum yield of the protonated species is more than an order of magnitude higher than that of the deprotonated species. Transient absorption spectroscopy shows that population of the triplet state occurs with a rate constant of 7.1 × 10⁸ s⁻¹ in the protonated species, while a rate constant of 1.7 × 10¹⁰ s⁻¹ is measured for the deprotonated species. While degradation of the deprotonated species is not affected by the presence of molecular oxygen, a twofold increase in the photodegradation yield of the protonated species in air-saturated conditions is observed.     

Demonstrating Contaminant Degradation at an MGP Site With Metabolic Gas Flux and Radio Carbon Dating

Obtaining lines of evidence indicating that contamination in sediment environments is degrading and being transformed to less toxic forms is an important component of building support for a monitored natural recovery remedy for contaminated sediments. This project was a field demonstration of manufactured gas plant contaminant degradation in river sediments using metabolic gas flux and was performed in an urban area section of a river in northeastern Indiana. CO₂ sorbent traps were deployed to measure CO₂ flux from the river sediments. Sediment samples were collected and analyzed for polycyclic aromatic hydrocarbon (PAH) concentrations and for microbial community composition using molecular techniques. The results showed that the deployment was successful, measuring CO₂ flux at all sediment locations and demonstrating that microbial contaminant degrading activity was occurring in the sediments. Radio carbon dating showed a significant portion of the CO₂ being generated (approximately 19–27 percent) was the result of fossil fuel degradation. Molecular results showed that the microbial community consisted of phylotypes known to be associated with monocyclic aromatic and PAH degradation. ©2017 Wiley Periodicals, Inc.