Remediation Of Streams Research Articles

Adaptive governance strategies to address wildfire and watershed resilience in New Mexico's upper Rio Grande watershed

Global climate models project that New Mexico's Upper Rio Grande watershed is expected to become more arid and experience greater climatic and hydrological extremes in the next 50 years. The resulting transitions will have dramatic implications for downstream water users. The Upper Rio Grande and its tributaries provide water to about half of New Mexico's population, including the downstream communities of Albuquerque and Santa Fe, and surrounding agricultural areas. In the absence of formal climate adaptation strategies, informal governance arrangements are emerging to facilitate watershed climate adaptation strategies, including fuel treatments and stream remediation. One example is the Rio Grande Water Fund (RGWF), a collaborative effort coordinating work to protect storage, delivery, and quality of Rio Grande water through landscape-scale forest restoration treatments in tributary forested watersheds. This article examines the RGWF as one example of an emerging adaptation strategy that is working within—and beyond—existing legal and policy frameworks to accomplish more collaborative efforts across jurisdictional lines and administrative barriers. We identified ten (10) key characteristics of adaptive governance from the relevant literature and then applied them to the RGWF's experience in the watershed to date. Key findings include: (1) the RGWF's approach as a collaborative network created the right level of formality while also keeping flexibility in its design, (2) a scalar fit to the environmental challenge built social capital and investment in its work, (3) leadership from key stakeholders leveraged opportunities in the watershed to create and maintain stability, and (4) use of adaptive management and peer review processes built capacity by creating the feedback loops necessary to inform future work.

Enhancing Urban Stream Values: The Case of the Cooks and Georges River Catchments

Waterway restoration in urban areas can be an important environmental policy topic. However, there have been few studies of monetary benefits to help justify expenditures and inform priority setting for remediation works. We investigated values for improving river health in two catchments in Sydney, Australia: the Cooks Catchment, which is smaller and urban-based, and the Georges Catchment, which is larger and located in both urban and periurban areas. Using choice experiments, we found that households are willing to pay Australian Dollars (AUD) 10.34 per year for 5 years in the Cooks Catchment, and AUD 2.64 in the Georges Catchment, to restore 1 km of urban waterway. We found that willingness to pay is moderated by the time until project outcomes are achieved. Comparison with typical costs of urban stream remediation suggested that there is a broad range of projects that will produce positive net benefits in the Cooks Catchment, whereas in the Georges Catchment the economically viable projects are those with lower cost and that can achieve their outcomes relatively quickly.

Catchment controls of denitrification and nitrous oxide production rates in headwater remediated agricultural streams

Heavily modified headwater streams and open ditches carry high nitrogen loads from agricultural soils that sustain eutrophication and poor water quality in downstream aquatic ecosystems. To remediate agricultural streams and reduce the export of nitrate (NO3−), phosphorus and suspended sediments, two-stage ditches with constructed floodplains can be implemented as countermeasures. By extending hydrological connectivity between the stream channel and riparian corridor within constructed floodplains, these remediated ditches enhance the removal of NO3− via the microbial denitrification process. Ten remediated ditches were paired with upstream trapezoidal ditches in Sweden across different soils and land uses to measure the capacity for denitrification and nitrous oxide (N2O) production and yields under denitrifying conditions in stream and floodplain sediments. To examine the controls for denitrification, water quality was monitored monthly and flow discharge continuously along reaches. Floodplain sediments accounted for 33 % of total denitrification capacity of remediated ditches, primarily controlled by inundation and stream NO3− concentrations. Despite reductions in flow-weighted NO3− concentrations along reaches, NO3− removal in remediated ditches via denitrification can be masked by inputs of NO3−-rich groundwaters, typical of intensively managed agricultural landscapes. Although N2O production rates were 50 % lower in floodplains compared to the stream, remediated ditches emitted more N2O than conventional trapezoidal ditches. Higher denitrification rates and reductions of N2O proportions were predicted by catchments with loamy soils, higher proportions of agricultural land use and lower floodplain elevations. For realizing enhanced NO3− removal from floodplains and avoiding increased N2O emissions, soil type, land use and the design of floodplains need to be considered when implementing remediated streams. Further, we stress the need for assessing the impact of stream remediation in the context of broader catchment processes, to determine the overall potential for improving water quality.

Habitat restoration for brown trout (Salmo trutta) has limited effects on macroinvertebrate communities in a historically metal-contaminated stream.

Quantifying the success of stream remediation or restoration projects that are designed to improve water quality or habitat, respectively, is often challenging because of insufficient posttreatment monitoring, poorly defined restoration goals, and failure to consider fundamental aspects of ecological theory. We measured the effects of habitat restoration on aquatic and terrestrial prey resources in a system recovering from the long-term effects of mining pollution. The study was conducted in the Upper Arkansas River, a Rocky Mountain stream located in central Colorado, USA. Remediation of California Gulch, a United States Environmental Protection Agency (USEPA) Superfund Site that discharged metals from past mining operations into the stream, was completed in 2000, resulting in significant improvements in water quality, benthic macroinvertebrate communities, and brown trout (Salmo trutta) populations. A large-scale restoration project designed to improve habitat and increase the density and biomass of brown trout was completed in 2014. To assess the effectiveness of these habitat improvements on invertebrate communities in this system, we sampled sites for 9 years before (2010-2014) and after (2015-2018) restoration was completed. In contrast to our expectations, we observed few changes in the abundance of aquatic or terrestrial invertebrates after restoration. The most common response was an overall reduction in abundance resulting from significant instream disturbances during and immediately after restoration, followed by a gradual return to pretreatment conditions. Despite reductions in prey abundance, the number of prey items in the diet of brown trout increased significantly after restoration. We discuss several explanations for these responses, including the effects of residual metals, increased predation by brown trout, and the recalcitrance of novel communities dominated by metal-tolerant species. Our results suggest that the effectiveness of remediation and restoration differed between macroinvertebrates and fish. Benthic macroinvertebrates were more dependent on water quality improvements at the watershed scale, whereas brown trout populations responded to both improvements in water quality and reach-scale improvements in habitat.Integr Environ Assess Manag 2022;18:1047-1055. © 2021 SETAC.

Stream Algal Biofilm Community Diversity Along An Acid Mine Drainage Recovery Gradient Using Multimarker Metabarcoding.

In southeastern Ohio, active remediation of streams affected by Acid Mine Drainage (AMD) has proven to be successful for some streams, while others have not recovered based on macroinvertebrate assessment. In this study, biofilms were collected from three Moderately Impaired, three Recovered, and two Unimpaired streams. The biodiversity was characterized by metabarcoding using two universal barcode markers (16S and 18S) along with two algal specific markers (UPA and rbcL) and high-throughput amplicon sequencing. For each marker, the ordination of Bray-Curtis Index calculated from the total Amplicon Sequence Variants (ASVs) present in each stream showed the Unimpaired and Recovered streams clustered, while Moderately Impaired streams were more distant. Focusing on the algal ASVs, the Shannon index for the rbcL, and UPA markers showed significantly lower alpha diversity in Moderately Impaired streams compared to Unimpaired streams, but the Recovered streams were not significantly different from the other two stream categories. The two universal markers together captured all algal phyla providing an outline of the diversity, but the two algal specific markers produced a greater number of ASVs and taxonomic depth for algal taxa. Further examination of the UPA marker revealed a drastic decrease in relative abundance of diatoms in Moderately Impaired streams compared to Recovered and Unimpaired streams. Likewise, diatom genera identified in the rbcL data and indicative of stream water quality showed marked differences in relative abundance among stream categories. Although all markers were useful, the algal-specific UPA and rbcL contributed more insights into algal community differences among stream categories.

Mass Transport Influence on Electrooxidation of Urea for Wastewater Remediation

Introduction Urea [CO(NH2)2] is one of the world’s most abundant waste products and is therefore commonly found in waste streams in varying concentrations. Human urine is 0.33 M urea while ruminant livestock urine has about half that concentration due to their herbivore diet [1]. Urea is also a versatile chemical that is industrially manufactured and commonly used. In effluent streams, urea hydrolyzes to form toxic ammonia (NH3) gas that can oxidize to form other pollutants like nitrates, nitrites, and nitrogen oxides [2]. Electrooxidation of urea for wastewater remediation is of interest whereby Eqn. (1) occurs at the anode of an electrochemical cell at a standard potential of E0 = –0.46 V vs. SHE at pH 14 [3]. Urea oxidation can be paired with concurrent reduction of water to produce H2 for energy storage, or reduction of O2 to directly produce energy in a direct urea fuel cell (DUFC) [4]. DUFCs and H2 production from urea both require high oxidation rates to make them economically viable. As a result, these studies typically use concentrations of 0.33 M urea to imitate human urine concentrations. Urea concentrations in wastewater will be diluted and therefore much lower, yet urea removal remains desirable for environmental reasons. At such low urea concentrations, transport to the electrode surface dominates the overall oxidation rate. The effects of low urea concentration on oxidation have yet to be fully studied, which is what this work aims to address. In an alkaline aqueous environment, nickel provides an active surface for urea oxidation due to the Ni2+/Ni3+ reversible redox couple described by Eqn. (2) at a standard electrode potential of E0= 0.49 V vs. SHE at pH 14 [3]. Subsequent urea oxidation occurs on Ni3+ and regenerates a Ni2+ site [Eqn. (3)]. At sufficiently anodic potentials, Eqns. (2–3) will occur in tandem and oxidize urea. Experimentally, urea oxidation is observed on Ni at potentials that favor Ni3+ which suggests that Eqn. (3) dominates over Eqn. (1). According to Eqn. (2), an alkaline environment is required for urea oxidation on Ni. To increase reaction rate, studies commonly use 1–5 M KOH, which is too harsh for an effluent stream. This work aims to investigate oxidation kinetics from pH 7–14. Materials and Methods Voltammetric studies were performed using a Solartron 1287A electrochemical interface coupled with CorrWare/CorrView software for data collection and visualization. Electrochemical experimental methods include cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronoamperometry (CA) in a three-electrode cell utilizing a 3.0 mm diameter Ni disk working electrode (WE), Hg/HgO reference electrode (RE), and a platinum coil counter electrode (CE). Urea is the analyte in all experiments, varying in concentration from 1.0 mM to 1.0 M. Supporting electrolytes include KOH and KHCO3 in varying concentrations to maintain pH between 7 and 14. Concentration and temperature variation are used to investigate transport and kinetic mechanism control, respectively. Results and Discussion Results will be discussed including electrochemical surface area (ECSA) and electrode characterization and the concentration regimes for both urea and KOH that define transport vs. kinetic reaction mechanism control. Initial experiments confirm mass transfer limited reaction at 15 mM urea and 0.1 M KOH at room temperature as seen in Figure 1. Experiments focusing on the temperature and concentration dependence are in progress. Significance Waste stream remediation is a major application of urea oxidation that focuses on removal of urea over maximizing current density. Further, it requires lower urea concentration and more neutral pH than typically studied. We lay the groundwork for mechanistic understanding over a range pH and urea concentrations relevant to such motivations. References Dijkstra, J., Oenema, O., Van Groenigen, J., Spek, J., Van Vuuren, A., and Bannink, A. Animal 7, 292 (2013).Ye, K., Wang, G., Cao, D. et al. Top Curr Chem 376, 42 (2018).Boggs, B. K., King, R. L., and Botte, G. Chem Comm 32, 4859 (2009).Singh, R. K., and Schechter, A. Acta 278, 405 (2018). Figure 1

Determination of impairment of Lambert’s Run Stream.

Mine drainage has been a serious issue throughout West Virginia due to the large amount of abandoned coal mines. A recent wave of mine closures is further decreasing the resources for mine drainage treatment, and some of the closed mines may have additional water pollution problems. Treatment of mine drainage is one of the largest environmental problems the mining industry faces. Therefore, it is a good time to study mine drainage treatment and to become as efficient as possible at it. This research examines the impairment of Lamberts Run and determines ways to improve the quality of the water. Impairment was determined based on West Virginia water quality standards by collecting stream data upstream and downstream of treatment sites. Collection of stream data included pH, temperature, conductivity, total dissolved solids, salt, and iron content to determine the effectiveness of the stream remediation that has previously occurred. Water samples from each site were collected and mixed into a Coliscan Easygel plate to determine the amount of coliform bacteria present, which causes harm to surrounding ecosystems. Benthic macroinvertebrate data was also analyzed for this stream. From the preliminary data collected, it is determined that Lamberts Run remains impaired despite rehabilitation attempts according to WVDEP water quality standards. Future investigation will focus on how to rehabilitate this stream.

Predicting mayfly recovery in acid mine-impaired streams using logistic regression models of in-stream habitat and water chemistry.

Mayflies (Order Ephemeroptera) require high quality water and habitat in streams to thrive, so their appearance after restoration is an indicator of ecological recovery. To better understand the importance of restoring in-stream habitat versus water chemistry for macroinvertebrate communities, we developed taxon-specific models of occurrence for five mayfly genera (Caenis, Isonychia, Stenonema, Stenacron, and Baetis) inhabiting streams in the Appalachian Mountains, USA. Presence/absence records from past decades were used to develop single and multiple logistic predictive models based on catchment characteristics (drainage area, gradient), in-stream habitat variables (e.g., substrate, channel morphology, pool and riffle quality), and water chemistry. Model performance was evaluated using (a) classification rates and Hosmer-Lemeshow values for test sets of data withheld from the original model-building dataset and (b) a field comparison of predicted versus observed mayfly occurrences at 53 sites in acid mine drainage-impaired watersheds in 2012. The classification accuracies of final models for Caenis, Stenacron, and Baetis ranged from 50 to 75%. In-stream habitat features were not significant predictor variables for these three taxa, only water chemistry. Models for Isonychia and Stenonema had higher classification rates (81%) and included both habitat and chemical variables. However, actual occurrences of Isonychia and Stenonema at study sites in 2012 were low, consistent with the calculated probability of occurrence (Po) < 0.60. Caenis occurred at test sites 35% of the time when the model predicted a Po > 0.40. Stenacron showed the greatest consistency of actual versus predicted occurrences, occurring at 56% of sites when the Po (based on pH and conductivity) was > 0.50 and only at 1 site when Po < 0.5. The results demonstrate how predictive models of individual indicator taxa could be valuable for evaluating the relative impacts of restoring physical habitat versus water chemistry during stream remediation.

Design of Remediation Actions for Nutrient Mitigation in the Hyporheic Zone

AbstractAlthough hyporheic exchange has been shown to be of great importance for the overall water quality of streams, it is rarely considered quantitatively in stream remediation projects. A main driver of hyporheic exchange is the hydraulic head fluctuation along the streambed, which can be enhanced by modifications of the streambed topography. Here we present an analytical 2‐D spectral subsurface flow model to estimate the hyporheic exchange associated with streambed topographies over a wide range of spatial scales; a model that was validated using tracer‐test‐results and measurements of hydraulic conductivity. Specifically, engineered steps in the stream were shown to induce a larger hyporheic exchange velocity and shorter hyporheic residence times compared to the observed topography in Tullstorps Brook, Sweden. Hyporheic properties were used to parameterize a longitudinal transport model that accounted for reactions in terms of first‐order decay and instantaneous adsorption. Theoretical analyses of the mitigation effect for nitrate due to denitrification in the hyporheic zone show that there is a Damköhler number of the hyporheic zone, associated with several different stream geomorphologies, that optimizes nitrate mass removal on stream reach scale. This optimum can be limited by the available hydraulic head gradient given by the slope of the stream and the geological constraints of the streambed. The model illustrates the complex interactions between design strategies for nutrient mitigation, hyporheic flow patterns, and stream biogeochemistry and highlights the importance to diagnose a stream prior remediation, specifically to evaluate if remediation targets are transport or reaction controlled.

Conservation Leverage: Ecological Design Culverts also Return Fiscal Benefits

Traditional hydraulically designed culverts impede ecological connectivity and degrade aquatic ecosystems. This problem is compounded by their ubiquity in the built environment. To overcome these limitations, alternative designs have been created to facilitate natural conditions and restore ecological connectivity. However, these “ecological design” culverts have perceived fiscal limitations that have prevented widespread implementation and consequently hampered conservation and remediation of stream ecosystems important for myriad fish species and aquatic organisms. We addressed these perceived fiscal limitations using cost–benefit analysis to estimate the lifetime fiscal net benefits of ecological design culverts over hydraulic culverts. We found that in nearly half of all cases remediation with ecological design culverts was more cost effective than maintaining hydraulic culverts and that it is most cost effective on small streams compared to larger ones. We also found that higher upfront replacement costs for ecological design culverts are overcome by their lifetime fiscal benefits. This is because of longer life span, reduced maintenance, and improved flood event resiliency of ecological design culverts. Our findings suggest that cost–benefit analysis could help conservation decision makers overcome higher construction costs and guide more cost‐effective and sustainable solutions for aquatic conservation and ecological connectivity.

Bioaccumulation trends of arsenic and antimony in a freshwater ecosystem affected by mine drainage

Environmental context The food web behaviours of As and Sb are poorly understood. We compare As and Sb bioaccumulation in a contaminated freshwater ecosystem. Metalloid accumulation decreased with increasing trophic level. Bioprecipitated minerals in microbial mats represent a direct route of uptake (by ingestion) of metalloids to tadpoles, which contained the highest concentrations ever reported. We demonstrate food web bioaccumulation, but not biomagification, of As and Sb. We also report an unexpectedly high tolerance of tadpoles to metalloid toxicity. Abstract We compared As and Sb bioaccumulation and biomagnification when these metalloids co-occurred at varying environmental concentrations in a stream and wetlands near a contaminated mine site in Idaho (USA). We measured As and Sb concentrations in water and substrate samples, and in tissues of organisms representing several trophic levels. Bioaccumulation of both As and Sb was observed in stream organisms with the following trend of bio-diminution with increasing trophic level: primary producers&gt;tadpoles&gt;macroinvertebrates&gt;trout. We also note reductions in metalloid concentrations in one of two stream remediation reaches engineered within the past 17 years to ameliorate metalloid contamination in the stream. Several wetlands contained thick microbial mats and were highly populated with boreal toad tadpoles that fed on them. The mats were extremely contaminated (up to 76564mgkg–1 As and 675mgkg–1 Sb) with amorphous As- and Sb-bearing minerals that we interpret as biogenic precipitates from geomicrobiological As- and Sb-cycling. Ingested mat material provided a direct source of metalloids to tadpoles, and concentrations of 3867mgkg–1 (As) and 375mgkg–1 (Sb) reported here represent the highest whole body As and Sb levels ever reported in living tadpoles. The bulk of tadpole metalloid burden remained in the gut despite attempts to purge the tadpoles prior to analysis. This study adds to a number of recent investigations reporting bioaccumulation, but not biomagnification, of As and Sb in food webs. Moreover, our results suggest that tadpoles, in particular, may be more resistant to metalloid contamination than previously assumed.

Changes in the visual preference after stream remediation using an image power spectrum: Stone revetment construction in the Nan-Shi-Ken stream, Taiwan

This paper investigates changes in the visual perception of a stream landscape due to remediation work (i.e., the construction of a stone revetment, which is a common ecological engineering technique in Taiwan) in the Nan-Shi-Ken stream. Various images of the Nan-Shi-Ken streambank before and after remediation were collected. The visual preference (P) and perceived naturalness (N), which were selected as indices of visual perception, were quantified using a questionnaire survey. The image characteristics were analyzed by the image spectrum method and presented by the spectrum-frequency slope (S). Furthermore, the relationship between S and the visual perceptual reaction was presented. The results of this study demonstrate that P and N increase with increasing vegetative cover on a stone revetment after stream remediation. P and N were highly correlated with S and proportional to S. S provides an index to assess P or N for a stream landscape change due to variation in vegetation.

Application of a constructed wetland system for polluted stream remediation

Summary In 2010, the multi-function Kaoping River Rail Bridge Constructed Wetland (KRRBW) was constructed to improve the stream water quality and rehabilitate the ecosystem of the surrounding environment of Dashu Region, Kaohsiung, Taiwan. The KRRBW consists of five wetland basins with a total water surface area of 15 ha, a total hydraulic retention time (HRT) of 10.1 days at a averaged flow rate of 14 740 m 3 /day, and an averaged water depth of 1.1 m. The influent of KRRBW coming from the local drainage systems containing untreated domestic, agricultural, and industrial wastewaters. Based on the quarterly investigation results of water samples taken in 2011–2012, the overall removal efficiencies were 91% for biochemical oxygen demand (BOD), 75% for total nitrogen (TN), 96% for total phosphorus (TP), and 99% for total coliforms (TC). The calculated first-order decay rates for BOD, TN, TP, NH 3 –N, and TC ranged from 0.14 (TN) to 0.42 (TC) 1/day. This indicates that the KRRBW was able to remove organics, TC, and nutrients effectively. The high ammonia/nitrate removal efficiency indicates that nitrification and denitrification processes occurred simultaneously in the wetland system, and the detected nitrite concentration confirmed the occurrence of denitrification/nitrification. Results from sediment analyses reveal that the sediment contained high concentrations of organics (sediment oxygen demand = 1.9–5.2 g O 2 /m 2 day), nutrients (up to 15.8 g total nitrogen/kg of sediment and 1.48 g total phosphorus/kg of sediment), and metals (up to 547 mg/kg of Zn and 97 mg/kg of Cu). Appropriate wetland management strategies need to be developed to prevent the release of contaminants into the wetland system. The wetland system caused the variations in the microbial diversities and dominant microbial bacteria. Results show the dominant nitrogen utilization bacteria including Denitratisoma oestradiolicum , Nitrosospira sp., Nitrosovibrio sp., D . oestradiolicum , Alcaligenes sp., Steroidobacter denitrificans , Hydrocarboniphaga effuse were responsible for nitrogen removal, and the dominant carbon degrading bacteria ( Stenotrophomonas maltophilia , H. effuse , Alcaligenes sp., Pseudomonas sp., Fusibacter sp., Chlofoflex i, Guggenheimella bovis , Bacillus pumilus ) were responsible for carbon reduction. The denaturing gradient gel electrophoresis (DGGE) and nucleotide sequence techniques provide a guide for microbial ecology evaluation, which can be used as an indication of contaminants removal. Results from this study show that constructed wetlands have the potential to be developed into an environmentally acceptable river water quality improvement and wastewater polishment alternative for practical application.

An ecotoxicological screening tool to prioritise acid mine drainage impacted streams for future restoration

Streams impacted by acid mine drainage (AMD) typically present water exhibiting low pH and high metal concentrations. These factors result in the environmental degradation of watercourses. The objective of this study was to develop and evaluate an ecotoxicological screening tool (EST) to prioritise future remediation of streams impacted by AMD. The Bloubank stream drainage system in South Africa, served as study area for this purpose. In the initial EST development phase physicochemical variables were assessed while in the second phase, epilithic filamentous green algae biomass (chl-a mg m−2), diatoms and filamentous green algae community structures were employed as bioindicators as well as Daphnia magna toxicity assays. Using a weight of evidence approach, the first three sites receiving AMD were critically and seriously modified, followed by site 4 that was modified. Sites 1–3 with EST scores ≤70% were assessed as priority candidates for future restoration.

Effect of imposed anaerobic conditions on metals release from acid-mine drainage contaminated streambed sediments

Remediation of streams influenced by mine-drainage may require removal and burial of metal-containing bed sediments. Burial of aerobic sediments into an anaerobic environment may release metals, such as through reductive dissolution of metal oxyhydroxides. Mining-impacted aerobic streambed sediments collected from North Fork Clear Creek, Colorado were held under anaerobic conditions for four months. Eh, pH, and concentrations of Cd, Cu, Fe, Mn, and Zn (filtered at 1.5 μm, 0.45 μm, and 0.2 μm), sulfate, and dissolved organic carbon (DOC) were monitored in stream water/sediment slurries. Two sediment size fractions were examined (2 mm–63 μm and <63 μm). Sequential extractions evaluated the mineral phase with which metals were associated in the aerobic sediment. Released Cu was re-sequestered within 5 weeks, while Fe and Mn still were present at 16 weeks. Mn concentration was lower than in the initial stream water at and beyond 14 weeks for the smaller sized sediment. Cd was not released from either sediment size fraction. Zn was released at early times, but concentrations never exceeded those present in the initial stream water and all was re-sequestered over time. The greatest concentrations of Cu, Fe, Mn, and Zn were associated with the Fe/Mn reducible fraction. Sulfate and Fe were strongly correlated ( r = 0.90), seeming to indicate anaerobic dissolution of iron oxy-hydroxy-sulfate minerals. DOC and sulfate were strongly correlated ( r = 0.81), with iron having a moderately strong correlation with DOC ( r = 0.71). Overall concentrations of DOC, sulfate, Cu, Fe, and Zn and pH were significantly higher ( p < 0.05) in the water overlying the small sized sediment samples, while the concentrations of Mn released from the larger sized sediment samples were greater.

Impacts of manure management practices on stream microbial loading into Conesus Lake, NY

The microbiology of stream water has a seasonal component that results from both biogeochemical and anthropogenic processes. Analysis of nonevent conditions in streams entering Conesus Lake, NY (USA), indicated that total coliform, Escherichia coli, and Enterococcus spp. levels peak in the summer in all streams, independent of the agricultural use in the stream sub-watershed. Prior to implementation of management practices, E. coli in water draining Graywood Gully, a sub-watershed with 74% of the land in agriculture, reached as high as 2806 CFU/100 mL, exceeding the 235 CFU/100 mL EPA Designated Bathing Beach Standard (EPA-DBBS). In contrast, North McMillan Creek, a sub-watershed with < 13% of its land in agriculture, had E. coli maxima generally near or below the EPA-DBBS. Graywood Gully at times had a higher microbial loading than North McMillan Creek, a sub-watershed 48 times larger in surface area. Over a 5-year study period, there was a major decrease in bacterial loading during nonevent conditions at Graywood Gully, especially after manure management practices were implemented, while bacterial loading was constant or increased in streams draining three other sub-watersheds. E. coli levels dropped more than 10 fold to levels well below the EPA-DBBS while the yearly maximum for Enterococcus dropped by a factor 2.5. Similarly, exceedency curves for both E. coli and Enterococcus also showed improvement since there were fewer days during which minimum standards were exceeded. Even so, Graywood Gully at times continued to be a major contributor of E. coli to Conesus Lake. If wildlife represents a significant source of indicator bacteria to Graywood Gully as has been reported, stream remediation, management efforts and compliance criteria will need to be adjusted accordingly.

Can forest fragments reset physical and water quality conditions in agricultural catchments and act as refugia for forest stream invertebrates?

Forest fragments embedded within agricultural landscapes have the potential to provide a “forest reset effect” by mitigating agricultural effects on water quality, and acting as refugia and conservation reserves for aquatic species. We investigated the ability of forest fragments to reset agricultural effects using four catchments in the South Island, New Zealand. Two catchments were dominated by agricultural activities, but each had an isolated forest fragment in the lower valley, and two catchments had continuous riparian forest along the valley floor. Riffles sampled in continuous forest were generally deeper than those in agricultural and forest fragments, and not surprisingly streams in forest fragments and continuous forest received less light than those in agricultural land. All sites had circum-neutral pH, but both conductivity and temperature were significantly lower at continuous forest sites than agricultural and forest fragment sites. Taxonomic richness, Margalef’s index and numbers of Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa were significantly higher in continuous forest than at forest fragment sites, but overall invertebrate densities did not differ between fragments and continuous forest. Several taxa were abundant at agricultural and forest fragment sites, but absent or at low densities in continuous forest. They included the blackfly Austrosimulium spp. and two caddisflies Pycnocentrodes sp. and Hydrobiosis parumbripennis. Conversely, the mayflies Austroclima sp. and Coloburiscus humeralis and the blepharicerid Neocurupira chiltoni were either restricted to continuous forest, or abundant in continuous forest but rare in agricultural and forest fragments. An ordination of communities separated those in agricultural and continuous forest sites, but communities at forest fragment sites were clustered among the agricultural sites. In this study forest fragments of 5–7 ha, located in the lower reaches of the catchment did not mitigate the negative upstream effects of agriculture on stream functioning. Fragment size (or riparian forest length), riparian forest width and vegetation type, and fragment location in the catchment may have critical roles in enabling forest fragments to reset the negative impacts of agriculture. Determining these characteristics of fragments has important consequences for stream remediation.

Polyelectrolytes derived from electron beam-induced polymerization

Electron-beam induced polymerization of water-soluble monomers is shown to drive the formation of water-soluble polymers that have application for waste water stream remediation. Irradiation parameters and precursor solution compositions have been identified that yield a water-soluble polymer with targeted properties. The process has been demonstrated in a pilot-scale operation.

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An understanding of the dynamics of metals and other solutes from mine drainage is essential to successful planning and stream remediation in mined Appalachian watersheds. Consequently, we conducted a study designed to quantify the spatial and temporal dynamics of trace metals and other water chemistry variables across a range of mining impairment. Water chemistry was monitored every three weeks in 34 stream segments of the lower Cheat River basin in northeastern West Virginia. Water sampling was conducted regardless of flow levels over a period from May 2002 - October 2003 and produced data on spatial and temporal variation in water temperature, dissolved oxygen, pH, conductivity, alkalinity, acidity, hardness, total dissolved solids, and dissolved concentrations of sulfates, iron, aluminum, manganese, cadmium, chromium, and nickel. Our study produced the following results. 1) Water chemistry was temporally variable in all streams examined; however, variability was generally highest in the moderately impaired streams. 2) Severely impaired waterbodies experienced poorest water quality during periods of extended low flows, whereas moderately impaired streams experienced poorest water quality under a variety of moderate and high flow conditions. 3) Elevated trace metal concentrations (chronic and acute) were common in moderately impaired streams and may provide an explanation for biological degradation in these streams. Our results suggest that water samples must be taken during late winter and late summer seasons in order to properly quantify chemical conditions in moderately impaired streams. Furthermore, full restoration of mining impacted watersheds may not be possible unless remediation approaches target reductions in trace metals and control temporal variability in water quality.

The effective source area of 90Sr for a stream near Chernobyl, Ukraine

Remediation of streams impacted by non-point source contaminants requires an understanding of both the areas within a watershed that are contributing contamination to streams and the pathways of contaminant migration to streams. From 1998 to 2002, we studied the migration of 90Sr in the Borschi watershed, a small (8.5 km 2) catchment three km south of the Chernobyl Nuclear Power Plant, Ukraine. Fuel particles, distributed in a heterogeneous pattern across the watershed, are weathering and releasing 90Sr from the fuel matrix. Depletion of 90Sr, evaluated in comparison to the immobile fission product europium-154, is occurring in the channel and wetland sediment. Channel sediments are uniformly depleted in 90Sr with depth. In wetland sediments, there is a zone of depletion in the top10 cm and a zone of accumulation at depths from 10 to 25 cm. Estimates of 90Sr depletion are used to map the effective source area that has contributed 90Sr loading to the main channel. The effective source area includes channel bottom sediments, a wetland in the central region of the watershed, and periodically flooded soils surrounding the wetland. The total depletion from the effective source area is estimated to be 36±7×10 10 Bq. Based on observations of stream flow rate and water quality in 1999–2001, the annual 90Sr removal rate from the watershed is estimated to be 1.4±0.2×10 10 or 1.5% of the inventory per year. When extrapolated over a 15-year period following the Chernobyl accident, the last value is in reasonable agreement with the estimated depletion of the source area based on 90Sr/ 154Eu ratios. The 90Sr yearly leaching rate considering the whole watershed is 0.2% while the 90Sr leaching rate considering the effective source area is an order of magnitude higher. Most of the 90Sr release in the watershed has originated from an effective source area of 0.62 km 2, or 7% of the watershed area.