Metal distribution and stability in constructed wetland sediment

The A-01 wetland treatment system (WTS) is a surface flow wetland planted with giant bulrush [Schoenoplectus californicus (C.A. Mey.) Palla] that is designed to remove Cu and other metals from the A-01 National Pollution Discharge Elimination System (NPDES) effluent at the Savannah River Site near Aiken, SC. Copper, Zn, and Pb concentrations in water were usually reduced 60 to 80% by passage through the treatment system. The Cu concentrations in the wetland sediments increased from about 4 to 205 and 796 mg kg(-1), respectively, in the organic and floc sediment layers in cell 4A over a 5-yr period. Metal concentrations were higher in the two top layers of sediment (i.e., the floc and organic layers) than in the deeper inorganic layers. Sequential extraction was used to evaluate remobilization and retention of Cu, Pb, Zn, Mn, and Fe in the wetland sediment. Metal remobilization was determined by the potentially mobile fraction (PMF) and metal retention by the recalcitrant factor (RF). The PMF values were high in the floc layer but comparatively low in the organic and inorganic layers. High RF values for Cu, Zn, and Pb in the organic and inorganic layers indicated that these metals were strongly bound in the sediment. The RF values for Mn were lower than for the other elements especially in the floc layer, indicating low retention or binding capacity. Retention of contaminants was also evaluated by distribution coefficient (Kd) values. Distribution coefficient (Kd) values were lower for Cu and Zn than for Pb, indicating a smaller exchangeable fraction for Pb.     

Economic feasibility of no-tillage and manure for soil carbon sequestration in corn production in northeastern Kansas

This study examined the economic potential of no-tillage versus conventional tillage to sequester soil carbon by using two rates of commercial N fertilizer or beef cattle manure for continuous corn (Zea mays L.) production. Yields, input rates, field operations, and prices from an experiment were used to simulate a distribution of net returns for eight production systems. Carbon release values from direct, embodied, and feedstock energies were estimated for each system, and were used with soil carbon sequestration rates from soil tests to determine the amount of net carbon sequestered by each system. The values of carbon credits that provide an incentive for managers to adopt production systems that sequester carbon at greater rates were derived. No-till systems had greater annual soil carbon gains, net carbon gains, and net returns than conventional tillage systems. Systems that used beef cattle manure had greater soil carbon gains and net carbon gains, but lower net returns, than systems that used commercial N fertilizer. Carbon credits would be needed to encourage the use of manure-fertilized cropping systems.     

Towards a Regional Index of Biological Integrity: the Example of Forested Riparian Ecosystems

Our premise is that measures of ecological indicators and habitat conditions will vary between reference standard sites and reference sites that are impacted, and that these measures can be applied consistently across a regional gradient in the form of a Regional Index of Biological Integrity (RIBI). Six principles are proposed to guide development of any RIBI: 1) biological communities with high integrity are the desired endpoints; 2) indicators can have a biological, physical, or chemical basis; 3) indicators should be tied to specific stressors that can be realistically managed; 4) linkages across geographic scales and ecosystems should be provided; 5) reference standards should be used to define target conditions; and 6) assessment protocols should be efficiently and rapidly applied. To illustrate how a RIBI might be developed, we show how four integrative bioindicators can be combined to develop a RIBI for forest riparian ecosystems in the Mid-Atlantic states: 1) macroinvertebrate communities, 2) amphibian communities, 3) avian communities, and 4) avain productivity, primarily for the Louisiana waterthrush (Seirius motacilla). By providing a reliable expression of environmental stress or change, a RIBI can help managers reach scientifically defensible decisions.     

The Occurrence and Impact of Sedimentation in Central Pennsylvania Wetlands

Sedimentation rates and deposited sediment characteristics in twenty-five wetlands in central Pennsylvania were measured during the period Fall 1994 to Fall 1995. Wetlands were located primarily in five watersheds, and represented a variety of hydrogeomorphic (HGM) subclasses and surrounding land use. Sedimentation rates were measured via the placement of 135 Plexiglas disks. Annual organic and inorganic loadings were determined. Sedimentation rates ranged from 0 to 8 cm/year, with sedimentation rates significantly correlated with surrounding land use and HGM subclass. Overall mean mineral and organic accretion rates were 778 g m2 yr-1 (+/- 1417) and 550 g m2 yr-1 (+/- 589), respectively. Mean mineral and organic accretion rates were significantly different by HGM subclass. The highest mineral accretion rates were for headwater floodplains, followed by impoundments, riparian depressions, mainstem floodplains, and slopes. The highest organic accretion rates were for riparian depressions, followed by impoundments, slopes, headwater floodplains, and mainstem floodplains. The potential effects of landscape disturbance on these sedimentation rates was also investigated, in order to develop a conceptual model to predict sedimentation rates for a given wetland in a variety of landscape settings. Different HGM subclasses exhibited significantly different mineral and organic accumulation rates, and varied in their responses to landscape disturbance and spatial variability in sedimentation patterns. Characterization of wetland plant communities in these same wetlands showed clear associations between individual plant species and ability to tolerate sediment. Species were categorized as very tolerant, moderately tolerant, slightly tolerant, and intolerant based on their association with environments of varying sedimentation magnitude. In general, species that were categorized as very tolerant or moderately tolerant increased their percent cover (dominance) over the sedimentation gradient. These observations were supported by greenhouse germination trials of eight species of wetland plants under a variety of sediment depths, ranging from 0 to 2 cm.     

From Global to Local: Providing Actionable Flood Forecast Information in a Cloud‐Based Computing Environment

Global and continental scale flood forecast provide coarse resolution flood forecast, but from the perspective of emergency management, flood warnings should be detailed and specific to local conditions. The desired refinement can be provided by the use of downscaling global scale models and through the use of distributed hydrologic models to produce a high‐resolution flood forecast. Three major challenges associated with transforming global flood forecasting to a local scale are addressed in this work. The first is using open‐source software tools to provide access to multiple data sources and lowering the barriers for users in management agencies at local level. This can be done through the Tethys Platform that enables web water resources modeling applications. The second is finding a practical solution for the computational requirements associated with running complex models and performing multiple simulations. This is done using Tethys Cluster that manages distributed and cloud computing resources as a companion to the Tethys Platform for web app development. The third challenge is discovering ways to downscale the forecasts from the global extent to the local context. Three modeling strategies have been tested to address this, including downscaling of coarse resolution global runoff models to high‐resolution stream networks and routing with Routing Application for Parallel computatIon of Discharge (RAPID), the use of hierarchical Gridded Surface and Subsurface Hydrologic Analysis (GSSHA) distributed models, and pre‐computed distributed GSSHA models.     

Digital innovation through partnership between nature conservation organisations and academia: A qualitative impact assessment

Nature conservation organisations increasingly turn to new digital technologies to help deliver conservation objectives. This has led to collaborative forms of working with academia to spearhead digital innovation. Through in-depth interviews with three UK research-council-funded case studies, we show that by working with academics conservation organisations can receive positive and negative impacts, some of which cut across their operations. Positive impacts include new ways of engaging with audiences, improved data workflows, financial benefits, capacity building and the necessary digital infrastructure to help them influence policy. Negative impacts include the time and resources required to learn new skills and sustain new technologies, managing different organisational objectives and shifts in working practices as a result of the new technologies. Most importantly, collaboration with academics was shown to bring the opportunity of a profound change in perspectives on technologies with benefits to the partner organisations and individuals therein.     

Effects of Urbanization on Flow Duration and Stream Flashiness: A Case Study of Puget Sound Streams,Western Washington,USA

The overall influence of urbanization on how flows of different frequency might change over time, while important in hydrologic design, remains imprecisely known. In this study, we investigate the effects of urbanization on flow duration curves (FDCs) and flow variability through a case study of eight watersheds that underwent different amounts of growth, in the Puget Sound region in Western Washington State, United States. We computed annual FDCs from flow records spanning 1960‐2010 and, after accounting for the effects of precipitation, we conducted statistical trend analyses on flow metrics to quantify how key FDC percentiles changed with time in response to urbanization. In the urban watersheds, the entire FDC tended to increase in magnitude of flow, especially the 95th‐99th percentile of the daily mean flow series, which increased by an average of 43%. Stream flashiness in urban watersheds was found to increase by an average of 70%. The increases in FDC magnitude and flashiness in urbanizing watersheds are most likely a result of increasing watershed imperviousness and altered hydrologic routing. Rural watersheds were found to have decreasing FDC magnitude over the same time period, which is possibly due to anthropogenic extractions of groundwater, and increasing stream flashiness, which is likely a result of reductions in base flow and increasing precipitation intensity and variability.     

An innovative sustainability assessment for urban wastewater infrastructure and its application in Chengdu, China

Sustainability assessments are an increasingly common tool for measuring progress towards sustainable development. Despite their popularity, sustainability assessments and the indicators that compose them are said to have had little impact on the policy arena. In this paper we discuss four attributes that we contend will improve the use of sustainability assessments to guide decision making: non-compartmentalization, site specificity, built-in guidance for target setting, and ability to measure active sustainability. We present a novel assessment tool for wastewater treatment infrastructure that illustrates these attributes. The assessment is composed of two-dimensional indicators we call “burden to capacity” ratios, that reveal and quantify the local value of resources embodied in wastewater and treatment byproducts, and the tradeoffs between designing systems for disposal versus reuse. We apply the sustainability assessment framework to an existing treatment plant in Chengdu, China and discuss the results.     

Sustainable Development and Wildlife Conservation in Tanzanian Maasailand

Many current wildlife conservation efforts in Africa focus on providing local communities with economic incentives to utilize wildlife as a form of land use in order to achieve the twin goals of ecological preservation as well as sustainable human economic development. Tanzanian Maasailand is home to some of the greatest concentrations of large mammals remaining outside National Parks and reserves, as well as a uniquely traditional human culture in the form of the Maasai themselves. Both are increasingly threatened by a variety of factors; poaching and habitat loss for wildlife, and the increasing marginalization of their pastoralist economy with regards to the Maasai. The fundamental cause of declining wildlife populations and biodiversity loss is that the Maasai have little economic or social interest in wildlife due to centralized management and financial benefits which are directed primarily to the Tanzanian state. Maasai pastoralism is highly compatible with wildlife, and the potential for the local communities to sustainably manage and benefit from this resource is promising. However, implementation of effective community-based natural resource management in the area faces political, cultural, and economic obstacles which will be critical in determining the outcomes of both conservation and community development efforts in Maasailand.