Surface Water Chemistry Research Articles

The response of vegetation to chemical and hydrological gradients at a patterned rich fen in northern Alberta, Canada

Study regionAcross northern Alberta Canada, patterned rich fens, with high concentrations of base cations, high pH, and high species richness, are important landscape features. McClelland Wetland is one of the largest representatives of this peatland type. Study focusWe explored the surficial water chemistry and plant community patterns through a grid of 64 plots placed within a patterned rich fen of 420 ha. New hydrological insights for the regionPlant communities and individual species abundances are tightly associated with surface water chemistry and water levels influenced by inflowing waters from surrounding mineral soils. Based on location and string/flark size and orientation, five spatial areas are recognized to occur in the fen. Spatial Areas located in the northern portion of the fen have different water chemistry and plant communities than Spatial Areas of the center and southern portions of the fen. The water chemistry of the northern spatial areas contains about one-half of the cation concentrations than those from the southern spatial areas and the stoichiometry of the water is different between these regions of the fen. Distributions of dominant plant species are associated with differing water chemistries, and separated by a narrow transition zone. Water sourced from different areas of the surrounding watershed largely control the water chemistry and plant distributions within the patterned area.

Investigating groundwater and surface water interactions using stable isotopes and hydrochemistry in the Notwane River Catchment, South East Botswana.

Study regionThe ephemeral Notwane River Catchment (NRC) is situated in semi-arid Southeast (SE) Botswana. It is part of the Ramotswa Transboundary Dolomitic Aquifer (RTBDA) in the Limpopo basin, shared by Botswana and South Africa. Study focusStable isotopic composition of deuterium (2H) and oxygen (18O) of the water molecule and water chemistry of groundwater and surface water (GW and SW) including rainfall samples were used to assess GW-SW interactions in the NRC. In addition, the seasonal effects on GW-SW interactions were also evaluated. As such, sample collection excursions were timed to coincide with the wet- and dry seasons, respectively. New hydrological insights for the regionGW and SW were found to have similar chemical characteristics. The major ions in both water types were Ca2+ and HCO-3 in both the dry- and wet season. There was a clear inverse relationship between ground relief and/or elevation and the concentration of chloride ions (mg/L) and electrical conductivity (µS/cm). That is, higher concentrations of chlorine were measured downstream compared to upstream and vice versa. The same trend was manifested for EC levels. Overall, the data indicated the existence of some highly active groundwater recharge sites along the Notwane River, that may be responsible for the aquifer recharge during above-normal rainfall events. In addition, the data revealed albeit inconclusively that GW-SW interactions in the NRC are likely to be influenced by an interplay of several factors such as: (a) the difference in water levels between the river and the adjacent groundwater table (b) the hydrogeology and location of the river channel because geologic formations such as faults and karsts play a critical role in GW-SW interactions. Karsts are known to support groundwater recharge which is different from the nearby semi-arid Kalahari region where recharge is driven by soil profile.

Net ecosystem dissolution and respiration dominate metabolic rates at two western Atlantic reef sites

AbstractOcean acidification is changing surface water chemistry, but natural variability due to nearshore processes can mask its effects on ecosystem responses. We present an approach of quantitatively resolving net ecosystem metabolism from an array of long‐term time series stations, offering perhaps the longest record of such processes over a reef to date. We used 8 and 6 yr of in situ, high‐quality frequency observations to characterize the changes in dissolved inorganic carbon and oxygen in La Parguera, Puerto Rico and Cheeca Rocks, Florida, respectively. Net respiration and net dissolution are the dominant metabolic processes at both systems, with a narrow window of ~ 4 months under net calcification. The annual mean net ecosystem calcification (NEC) rates for La Parguera (−0.68 ± 0.91 kg CaCO3 m−2 yr−1) and Cheeca Rocks (−0.48 ± 0.89 kg CaCO3 m−2 yr−1) were on the lower end of typical NEC ranges determined for other reef areas using chemistry‐ and census‐based approaches. At Cheeca Rocks, 53% of the variance in NEC can be explained by net ecosystem production (NEP) and 30% by aragonite saturation state (Ωarag). At La Parguera, NEC is primarily driven by changes in NEP. The linear relationship between NEC and NEP showed a significant slope (± standard error) of 1.00 ± 0.005 and 0.88 ± 0.04 for La Parguera and Cheeca Rocks, respectively. These results suggest that NEP appears to play a prominent role on NEC, and Ωarag probably is not the most informative measure to monitor when attempting to resolve the long‐term impacts of ocean acidification.

Hydrobiogechemical interactions in the hyporheic zone of a sulfate-impacted, freshwater stream and riparian wetland ecosystem.

Coupled abiotic and biotic processes in the hyporheic zone, where surface water and groundwater mix, play a critical role in the biogeochemical cycling of carbon, nutrients, and trace elements in streams and wetlands. Dynamic hydrologic conditions and anthropogenic pollution can impact redox gradients and biogeochemical response, although few studies examine the resulting hydrobiogeochemical interactions generated within the hyporheic zone. This study examines the effect of hyporheic flux dynamics and anthropogenic sulfate loading on the biogeochemistry of a riparian wetland and stream system. The hydrologic gradient as well as sediment, surface water, and porewater geochemistry chemistry was characterized at multiple points throughout the 2017 spring-summer-fall season at a sulfate-impacted stream flanked by wetlands in northern Minnesota. Results show that organic-rich sediments largely buffer the geochemical responses to brief or low magnitude changes in hydrologic gradient, but sustained or higher magnitude fluxes may variably alter the redox regime and, ultimately, the environmental geochemistry. This has implications for a changing climate that is expected to dramatically alter the hydrological cycle. Further, increased sulfate loading and dissolved or adsorbed ferric iron complexes in the hyporheic zone may induce a cryptic sulfur cycle linked to iron and carbon cycling, as indicated by the abundance of intermediate valence sulfur compounds (e.g., polysulfide, elemental sulfur, thiosulfate) throughout the anoxic wetland and stream-channel sediment column. The observed deviation from a classical redox tower coupled with potential changes in hydraulic gradient in these organic-rich wetland and stream hyporheic zones has implications for nutrient, trace element, and greenhouse gas fluxes into surface water and groundwater, ultimately influencing water quality and global climate.

Optimization of Landsat Chl-a Retrieval Algorithms in Freshwater Lakes through Classification of Optical Water Types

The application of remote sensing data to empirical models of inland surface water chlorophyll-a concentrations (chl-a) has been in development since the launch of the Landsat 4 satellite series in 1982. However, establishing an empirical model using a chl-a retrieval algorithm is difficult due to the spatial heterogeneity of inland lake water properties. Classification of optical water types (OWTs; i.e., differentially observed water spectra due to differences in water properties) has grown in favour in recent years over traditional non-turbid vs. turbid classifications. This study examined whether top-of-atmosphere reflectance observations in visible to near-infrared bands from Landsat 4, 5, 7, and 8 sensors can be used to identify unique OWTs using a guided unsupervised classification approach in which OWTs are defined through both remotely sensed reflectance and surface water chemistry data taken from samples in North American and Swedish lakes. Linear regressions of algorithms (Landsat reflectance bands, band ratios, products, or combinations) to lake surface water chl-a were built for each OWT. The performances of chl-a retrieval algorithms within each OWT were compared to those of global chl-a algorithms to test the effectiveness of OWT classification. Seven unique OWTs were identified and then fit into four categories with varying degrees of brightness as follows: turbid lakes with a low chl-a:turbidity ratio; turbid lakes with a mixture of high chl-a and turbidity measurements; oligotrophic or mesotrophic lakes with a mixture of low chl-a and turbidity measurements; and eutrophic lakes with a high chl-a:turbidity ratio. With one exception (r2 = 0.26, p = 0.08), the best performing algorithm in each OWT showed improvement (r2 = 0.69–0.91, p < 0.05), compared with the best performing algorithm for all lakes combined (r2 = 0.52, p < 0.05). Landsat reflectance can be used to extract OWTs in inland lakes to provide improved prediction of chl-a over large extents and long time series, giving researchers an opportunity to study the trophic states of unmonitored lakes.

Natural Water Chemistry Change in the Surface Water of Chengdu and Impact Factors

To investigate the impact of megacities on the chemistry of surface waters, monthly sampling and monitoring were conducted in the Chengdu section of the Minjiang and Tuojiang River basin, corresponding to the upper reaches of the Yangtze River since the spring of 2019, including the influent and effluent water samples from 57 sewage treatment plants in Chengdu. All the samples were analyzed for major ions and other water chemistry parameters, and compared with the historical data of the Minjiang and Tuojiang River. The results showed that the Chengdu surface water still presented a natural chemistry with medium-low total dissolved solids(TDS), and calcium bicarbonate chemistry type, which is the natural consequence of the weathering of carbonate rocks in the basin effected by the weathering of silicates and evaporites. The natural water chemistry of the surface waters in Chengdu presented monthly variation, i.e.,the concentration of major ions and TDS was higher in the dry season compared to the wet season, reflecting the variations of point source. Spatially, the concentration of major ions and TDS downstream of the city was higher than those in the upper reaches, and the concentration in the tributary was higher than that in the mainstream, which may reflect urban influence. Further analyses, such as simulation calculations, indicated that urban activities were the major driving factor for the chemistry change in the surface waters in Chengdu, which is evidenced by the significant contribution of the sewage discharge to the elevated Cl- and Na+ and the ratio of hardness/alkalinity>1 from anthropogenic acid gas emissions. A comparison with the water chemistry of the Minjiang and Tuojiang River in the 1960s indicated that, the current Cl-/Na+ ratio has significantly increased, which has been evidenced by a salinization trend. As a megacity nearest to the source of the Yangtze River, the impact of Chengdu on the natural water chemistry of the Yangtze River system and its environmental effects deserves more attention.

Water quality assessment of three tropical freshwater lakes of Kerala, SW India, with special reference to drinking water potential

Investigation on the physico-chemical parameters and bacteriological examination of surface waters of Sasthamkotta, Vellayani, and Pookot lakes of Kerala, SW India has been performed to assess the quality of lake waters for drinking purposes. For this study, a total of 60 surface water samples, 20 samples each from the three lakes were collected along S-N-W transects that cover the entire area and was performed during the year 2016–2017. The results obtained during the analyses were compared with maximum permissible limit values recommended by World Health Organization (2017) and Bureau of Indian standards (2012). The results showed that the annual concentration of a majority of the constituent parameters showed an increasing trend in their concentration.Acidification (mean pH 5.6) of Pookot lake owing to the forest canopy and spring water intrusion may deteriorate the species diversity of Pookot lake. TDS values of Sasthamkotta lake (mean TDS > 500 mg/l) and Vellayani lake (mean TDS > 500 mg/l) reflect the turbid and contamination scenario of the freshwater ecosystems. Increased concentration of primary nutrients like NO3− (mean >4 mg/l) and PO43− (mean >3 mg/l) in Vellayani lake depict nutrient enrichment, both from anthropogenic influences and runoff from point and non-point sources in a swift pace. The observed hydro-chemical facies were NaHCO3 for Pookot lake, NaCl with subordinates of Ca and Mg for Sasthamkotta lake and NaHCO3 with subordinates of SO42− for Vellayani lake, based on Piper trilinear diagrams. Water Quality Index (WQI) were calculated for evaluating influence of natural and anthropogenic activities based on several key parameters (pH, EC, TDS, HCO3−, Cl−, SO42−, NO3−, Ca2+, Mg2+, Na+, K+) in surface water chemistry. As per the WQI, majority of the samples in the three lakes, based on the observed chemical constituents were falling under ‘good’ category but the real havoc was existed due to bacteriological contamination. It was observed that there was an increased count of coliforms in the lake waters of Vellayani (140 MPN/ml), Sasthamkotta (260 MPN/ml) and Pookot (90 MPN/ml), which must be zero for drinking needs, according to WHO (2017) and BIS (2012) drinking water guidelines. The increased microbial population in all the three lakes indicate the unhealthy practices in the lake catchments. Therefore, sustainable management measures should be taken to improve the water quality of the fresh water resources of Kerala.

Application of multivariate statistical analysis and water quality index for quality characterization of Parbati River, Northwestern Himalaya, India

The present study is an attempt to accomplish the understanding of the factors impacting Parbati river water quality in Kullu district of Himachal Pradesh. The main objective is to assess the overall water quality, to explore its hydrogeochemical characteristics including major ion contents and other chemical parameters using Water Quality Index (WQI), statistical techniques (principal component analysis) and conventional graphical representation such as Piper trilinear diagram, Durov. Eighteen surface water samples were collected from different altitudinal sites to analyze physico-chemical parameters for June 2019 and September 2019. Analytical outcomes of thirty-six surface water samples collected in Pre-monsoon and Post-monsoon seasons are well within the permissible limits as per BIS, 2012 and WHO 2011 for drinking and domestic purposes. Water quality characterization for the assigned use shows that maximum surface water samples fall under excellent to good water quality index and are suitable for drinking without conventional treatment. The Piper trilinear diagram classified 100% of surface water samples for both seasons’ falls in the fields of Ca2+-Mg2+-HCO3− water type indicating temporary hardness. Abundance of ions in the water samples is in the order: anions HCO3−>Cl−>SO42−>NO3− and cations Mg2+>Ca2+>Na+>K+. PCA identifies that the surface water chemistry is influenced by natural factors as well as minor anthropogenic activities in both the seasons. The correlation matrix has been prepared to analyse and observe the significance of the factors on the assessment of river water quality. Periodic assessment of surface water samples of the Parbati river and adjoining areas should be carried out. This approach will help in finding out any contamination of water occurring due to rapid socio-economic development as well as explosion of tourism industry in the region. Present study will work as baseline database for any future work in the region.

The geochemistry of Irish rivers

Study regionIreland Study focusMultiple studies have established that catchment geology and weathering regime strongly influence surface water chemistry, and that geochemical cycling can vary due to seasonal climatic conditions. However, fewer studies have focused on the influence these controls in a holistic manner. We relate the water chemistry of a country-wide Irish river survey to atmospheric input, underlying geology, and the influence of bogs. Climatic conditions were defined by an atypically wet winter and an unusually dry summer, providing the opportunity to investigate river chemistry variation across hydrologic conditions. Sampling included 21 of Ireland’s 22 largest rivers ranked by discharge, first-order and second-order streams draining bog lands, a second-order stream draining a limestone catchment, and downstream transects along the River Shannon. All samples were analyzed for major elements, selected trace elements, and nutrients, and a subset was analyzed for δ34SSO4. New hydrological insightsMost catchments were dominated by carbonate weathering with little contribution from the weathering of aluminosilicates. River water composition also varied geographically along the prevailing wind direction due to inputs from marine aerosols, with additional weathering components important in some systems. Seasonal influences could be seen in the chemistry of the headwaters of the River Shannon, while the lower reaches of the river exhibited less variable behavior throughout seasonal changes, likely due to the influence of lakes in the River Shannon system.

Hydrochemical Characteristics and Factors of Surface Water and Groundwater in the Upper Yongding River Basin

The Yongding River basin is an important water conservation and ecological barrier area in the Northwest of Hebei Province. Reduced runoff and deterioration of the water environment in this area have become increasingly prominent under the effects of climate change and intensive human activities. Clarifying the chemical characteristics and factors of surface water and groundwater in the upper Yongding River basin can provide data and support for the sustainable use of water resources. Stable isotopes of hydrogen and oxygen (δ2H and δ18O) were used to study the sources of surface water and groundwater. Mathematical statistics and hydrogeochemical methods were then used to analyze the regional hydrogeochemical processes and factors of surface water and groundwater. The results showed that precipitation was the main source of surface water and groundwater. Under the effects of natural factors and human activities, the Yang River and Sanggan River basins exhibited significant differences in surface water chemistry. The sub-basins were ranked by ion concentration as follows: Sanggan River>Yang River. The main cation and anions of the Sanggan River basin were Na+, Cl-, and SO42-, while in the Yang River basin, Ca2+ and HCO3- were the most common. The water chemistry of the Sanggan River exhibited greater variation than that of the Yang River. Surface water chemistry were mainly controlled by mineral dissolution and evaporation, but human activities were reflected in different sub-basins. Surface water in the Sanggan River basin was affected by industrial wastewater discharge, while that of the Yang River basin was affected by agricultural production and cities. However, the continuous increase of Cl- and SO42- concentrations, caused by industrial wastewater discharge and acid rain, was the limiting factor for sustainable use of surface water resources. In future, surface water in Sanggan River basin should be used with consideration to the effects of both total salinity and chemical composition of the water, while in Yang River, a focus should be placed on total salinity. The use of surface water resources in accordance with local conditions is an effective measure for the sustainable use of water resources and the restoration of groundwater levels in this region.

Drivers, pressures, and state responses to inform long-term oil sands wetland monitoring program objectives

Boreal peatlands provide numerous ecosystem services ranging from carbon sequestration to the provisioning of habitat for species integral to Indigenous communities. In the Oil Sands Region of Alberta, Canada, human development related to oil and gas extraction occurs in a wetland-dominated landscape. Wetland monitoring programs can determine the extent to which development impacts wetlands, but existing monitoring programs focus on characterizing biodiversity across the region and on compliance and regulatory monitoring that assumes impacts from oil sands development do not extend past lease boundaries. This is unlikely to be true since some impacts, such as particulate deposition, can extend over large areas contingent on local weather and topography. To inform the development of a new regional wetland monitoring program to assess the cumulative effects of oil sands development on wetlands, we synthesized information on the scope of wetland research across the Oil Sands Region, including the anthropogenic stressors that impact wetlands and the wetland characteristics sensitive to different disturbances. We developed a conceptual model linking human development with wetland ecology in the region to make explicit the relationships among oil sands development stressors and different components of wetland ecosystems. By highlighting testable relationships, this conceptual model can be used as a collection of hypotheses to identify knowledge gaps and to guide future research priorities. relationships among We found that the majority of studies are short-term (77% were ≤ 5 years) and are conducted over a limited spatial extent (82% were sub-regional). Studies of reclaimed wetlands were relatively common (18% of all tests); disproportionate to the occurrence of this wetland type. Results from these studies likely cannot be extrapolated to other wetlands in the region. Nevertheless, the impacts of tailings contaminants, wetland reclamation activities, and surface water chemistry are well-represented in the literature. Research on other types of land disturbance is lacking. A coordinated, regional monitoring program is needed to gain a complete understanding of the direct and indirect impacts of human development in the region and to address remaining knowledge gaps.

Evaluation of factors influencing surface water quality in a coalfield area of Damodar valley, India: a sustainable uses

ABSTRACT A systematic study on the major ions and heavy metals was carried out for surface water resources of EB coalfield for water quality assessment, source apportionment and studying the geochemical processes controlling the surface water quality. Seasonal effect was not very prominent for the surface water quality parameters inclusive of metals, though some dilution was observed in some parameters during the monsoon season. Some of the parameters exceeded the drinking water limits like TDS, turbidity, NO3 −, F−, total hardness and Mg2+ in surface water. The Fe concentrations exceeded the desirable limit of the BIS standard in about 26% of the water sample. The surface water chemistry of the EB coalfield is influenced by extensive coal mining activities. The principal component analysis of metals and health concerning anions demonstrated that the data were synthesised into three loading factors with Eigen values >1 and explaining about 71.4% of the total variance. The extracted factors seem to indicate geogenic sources, coal mining and associated transportation. The quality assessment of the surface water for irrigation suitability suggested that the calculated parameters (SAR, %Na, RSC and MH) of water to be in the range of good to permissible; however, at a few sites, SAR values and MH make it unsuitable for irrigation. Thus, the study exemplified the need for awareness about the contamination of surface water within EB coalfield area. The findingsof the present study may be useful to decision-makers in developing plans for surface water quality management and sustainable use.

Effects of biotransport and hydro-meteorological conditions on transport of trace elements in the Scott River (Bellsund, Spitsbergen).

The shaping of surface water chemistry in the Svalbard Archipelago is strongly dependent on the geology of the catchment and the process of long-range transport of atmospheric pollutants (LRATP). It was found that the dissolved trace elements in the Scott River, which catchment is characterized by a decreasing degree of glaciation, were of the natural origin (i.a. weathering and dissolution of local geological substratum). The exception was Zn originated from LRATP. The paper describe the influence changes in hydro-meteorological conditions and the presence of a seabird colony on the variability in the transport of trace elements within the Scott River catchment. The work assesses long-time fluctuations in the concentration of twenty five trace elements (i.a. Al, Cr, Cu, Pb, Sr, and Zn) from eighty-four surface water samples and their relation to changes in water discharge (Q), precipitation (P), pH, and dissolved organic carbon (DOC) at two river sites (with one being under the influence of the biotransport factor). Based on the results of matrix correlation and cluster analysis it was found that the additional load of DOC from the nesting site of Larus Argentatus in the mouth section of the river drastically changed the hydro-geochemical cycle of Co, Ni, Zn, Ga, Sr, Rb, Ba and U (0.30 < r < 0.51). Furthermore, the results of cluster analysis confirmed that the bird colony’s nesting site was strongly responsible for the presence of U, Rb, Zn, Ni and marine-derived nutrients (e.g. Se and Li). The discharge of glacier meltwater and the alkaline character of water have a negative effect on the dissolution of Li and Mn (−0.31 < r < −0.51), but positively affect the level of Rb and U (r = 0.31 and 0.35, respectively) due to it being washing out a seabird nesting colony in the mouth section of the Scott River. It was observed that the event of rises in air temperature and rain, which results in increased water discharge, caused an intense transport of the trace elements load. Moreover, results of the precipitation sensitivity coefficient factor (CF) proved that precipitation effect the occurrence of Li, Sr and U in the Scott River.

Geochemical Characteristics of Sediment in Tropical Lake Sentani, Indonesia, Are Influenced by Spatial Differences in Catchment Geology and Water Column Stratification

Physical and (bio)chemical processes in the catchment as well as internal lake processes influence the composition of lacustrine sediments. Lake internal processes are a consequence of reactions and fluxes between sediment, porewater and the water column. Due to its separation into four interconnected sub-basins, Lake Sentani, Papua Province, Indonesia, is a unique tropical lake that reveals a wide range of geochemical conditions. The highly diverse geological catchment causes mineralogical and chemical differentiation of the sediment input into each sub-basin. Also, strong morphological differences between the sub-basins result in a unique water column structure for each sub-basin, ranging from fully mixed to meromictic. Given the strong differences in sediment composition and bottom water chemistry among the four sub-basins, Lake Sentani offers a unique chance to study multiple lacustrine systems under identical climate conditions and with a common surface water chemistry. We used sediment cores and water samples and measured physicochemical water column profiles to reveal the geochemical characteristics of the water column, the sediment and pore water for all four sub-basins of Lake Sentani. The chemical composition of the sediment reveals differentiation among the sub-basins according to their sediment input and water column structure. Catchment lithology mainly affects overall sediment composition, whereas pore water chemistry is also affected by water column structure, which is related to basin morphology and water depth. In the meromictic sub-basins the bottom water and sediment pore water appear to form a single continuous system, whereas in those sub-basins with oxygenated bottom water the sediment-water interface forms a pronounced chemical barrier.

Assessment of anthropogenic pollution using multiple hydrogeochemical tools and statistical analysis in rural plain basins of the Argentinian Pampean Plain

AbstractChemistry of surface water and groundwater can be conditioned by geology, anthropic influence, and exchange of flow between them. The Pampean Plain located in Argentina has gaining streams and mainly rural activities. An increase in the concentration of chemical values of surface waters with respect to groundwater can be attributed to the anthropogenic contribution. The aim of this work was to identify the natural and/or anthropic processes that determine the chemistry of surface water and groundwater in a sector of the Pampean Plain of Argentina through the analysis of major and trace elements, 18O and 2H isotopes, and statistical tools. A surface water and groundwater sampling network was designed, where physicochemical parameters were measured, and samples were taken to determine major and trace elements and stable isotopes of water. The results indicate that dissolution, cation exchange, and evaporation are the main processes that determine the chemistry of the major elements associated with natural processes without showing evidence of anthropic involvement. Some trace elements that are statistically associated with major ions evidence water‐sediment interaction within the aquifer. On the other hand, trace elements, as heavy metals, present a higher concentration in surface water compared to groundwater. This fact, evidences an anthropogenic contribution attributable to anthropic activities. The multivariate statistical analysis allowed discriminating between those trace elements associated with natural processes from those influenced by anthropic activity, even when these elements' concentration was very low.

A missing link in the mid‐late Permian record of north‐eastern Pangea: A sedimentological evaluation of the Permian Belfast Harbour Evaporite Formation of County Antrim, Northern Ireland

AbstractAncient salt deposits preserve a record of highly specific environmental, climatic and biological conditions, including past surface water chemistry and water depths, local air temperatures, atmospheric composition and halophilic microorganisms. This paper presents the first sedimentological study of the mid‐Late Permian Belfast Harbour Evaporite Formation of Northern Ireland. This formation is dominated by bedded halite, contains some siliciclastic mudstone and bedded anhydrite, and is cross‐cut by intrusive igneous rocks. The bedded halite lithology contains bottom‐growth chevron and cornet crystals, efflorescent crusts and dissolution pipes, which are evidence of a saline surface brine that underwent periods of evapoconcentration, desiccation and flooding. The mudstone lithology contains dewatering structures, intraclasts and mudcracks, which indicate flooding and desiccation in dry mudflats. Bedded anhydrite was deposited as beds of gypsum cumulate crystals in saline surface waters. The Belfast Harbour Evaporite Formation was formed by saline lakes with associated mudflats, based on sedimentary characteristics and supported by mineralogical, geochemical and stratigraphic context. Diagenetic features reflect dissolution and cementation at the surface and shallow subsurface in the depositional environment and limited late‐stage alterations. Syndepositional dissolution pipes in bedded halite were formed by flooding events. Early halite cement is present in dissolution pipes and mudstones. Gypsum/anhydrite repeatedly dehydrated and rehydrated to form an interlocking crystal mosaic. Later features include fluid migration and the intrusion of mafic rocks. The Belfast Harbour Evaporite Formation was deposited by an ephemeral saline lake and dry mudflat system in an arid climate. This study, when compared to age‐equivalent continental deposits elsewhere, suggests that arid settings with saline lakes existed across much of Pangea during the Permo‐Triassic. The Belfast Harbour Evaporite Formation stratigraphically underlies the extremely low pH saline lakes of the Mercia Mudstone Group, implying that it aids in understanding the formation of Pangean acid brine lakes.

Role of Ca2+ in the CO2 corrosion behavior and film characteristics of N80 steel and electroless Ni–P coating at high temperature and high pressure

The effects of Ca2+ on the CO2 corrosion behavior and film characteristics of N80 carbon steel and electroless Ni–P coating at high temperature and high pressure were investigated by immersion tests, in-situ electrochemical measurements, surface characterization techniques and water chemistry analysis. The results demonstrate that the corrosion of N80 steel is significantly influenced by Ca2+ concentration, however Ni–P coating exhibits exceptional corrosion resistance regardless of Ca2+ concentration. The microstructure and compactness of FeCO3 corrosion film is altered with the increased incorporation of Ca2+, thereby affecting the electrolyte penetration and the corrosion rate consequently. The added Ca2+ also impacts the water chemistry of the aqueous phase, postponing the FeCO3 precipitation. Meanwhile, the superb corrosion resistance of Ni–P coating is owing to the protection of the formed NiO/Ni(OH)2 film and the absence of scale formation.

Metals Alter Membership but Not Diversity of a Headwater Stream Microbiome

Metal contamination from mining or natural weathering is a common feature of surface waters in the American west. Advances in microbial analyses have created the potential for routine sampling of aquatic microbiomes as a tool to assess the quality of stream habitat. We sought to determine if microbiome diversity and membership were affected by metal contamination and identify candidate microbial taxa to be used to indicate metal stress in stream ecosystems. We evaluated microbiome membership from sediments at multiple sites within the principal drainage of an EPA superfund site near the headwaters of the Upper Arkansas River, Leadville, CO. From each sample, we extracted DNA and sequenced the 16S rRNA gene amplicon on the Illumina MiSeq platform. We used the remaining sediments to simultaneously evaluate environmental metal concentrations. We also conducted an artificial stream mesocosm experiment using sediments collected from two of the observational study sites. The mesocosm experiment had a two-by-two factorial design: (i) location (upstream or downstream of contaminating tributary), and (ii) treatment (metal exposure or control). We found no difference in diversity between upstream and downstream sites in the field. Similarly, diversity changed very little following experimental metal exposure. However, microbiome membership differed between upstream and downstream locations and experimental metal exposure changed microbiome membership in a manner that depended on origin of the sediments used in each mesocosm.IMPORTANCE Our results suggest that microbiomes can be reliable indicators of ecosystem metal stress even when surface water chemistry and other metrics used to assess ecosystem health do not indicate ecosystem stress. Results presented in this study, in combination with previously published work on this same ecosystem, are consistent with the idea that a microbial response to metals at the base of the food web may be affecting primary consumers. If effects of metals are mediated through shifts in the microbiome, then microbial metrics, as presented here, may aid in the assessment of stream ecosystem health, which currently does not include assessments of the microbiome.

Tailings dust characterization and impacts on surface water chemistry at an abandoned Zn-Pb-Cu-Au-Ag deposit

The increased potential for dust mobilization as a result of climate change indicates a need to better understand interactions between dust and water. This research investigates the geochemical effects of tailings dust on surface waters near Stirling mine, Nova Scotia. Tailings were sieved to <63 μm as a proxy for dust and analyzed geochemically and mineralogically for the identification of primary and secondary metal-bearing phases using a scanning electron microscope with automated mineralogy, electron microprobe analysis and synchrotron-based microanalysis. Metal-hosting phases identified include in order of abundance; sphalerite (ZnS), cerussite (PbCO3), chalcopyrite (CuFeS2), Pb–Mn phases (possibly cesàrolite (PbMn3O6(OH)2)), smithsonite (ZnCO3), goethite (FeO(OH), aurichalcite ((Zn,Cu)5(CO3)2(OH)6), hydrohetaerolite (ZnMn2O4·H2O), tennantite (Cu6(Cu4Zn2)As4S12S), and galena (PbS). Shake flask tests were conducted in simulated stream waters (pH = 7) using sieved tailings and passive dry deposition collector filters to investigate the solubility of metal-hosting mineral phases within dust. Results indicate metal leaching at near neutral pH conditions. Sphalerite, cerussite and chalcopyrite are likely the main sources of Zn, Pb, and Cu in the shake flask leachate, based on calculated saturated indices and mass balance. Analyses of stream waters indicate similar conditions (pH, ORP, saturation indices, etc.) compared to the results of the shake flask tests, suggesting they provide reasonable insight about processes occurring in the field. Tailings dust generated at the site is therefore a potential source of metals to surface waters.

Using Concentration–Discharge Relationships to Identify Influences on Surface and Subsurface Water Chemistry along a Watershed Urbanization Gradient

Urban development within watersheds impacts the hydrology and water quality of streams, but changes to groundwater–surface water interactions in this “urban stream syndrome” are not yet well understood. This study focused on three stream systems in a northern Virginia (USA) protected area with 14.2, 31.7, and 66.1% developed land in their watersheds. Surface water was sampled weekly for nutrients, dissolved metals, sulfate, ancillary water quality parameters, and discharge over two non-consecutive years with the hyporheic zone sampled during the second year. Concentration–discharge relationships revealed largely chemostatic behavior in surface water solutes in the least urbanized stream, while in the two more urbanized streams, these relationships tended to have significant positive and negative slopes, indicating diverse delivery pathways depending on the constituent. In the least urbanized stream, linear regressions between discharge and solute concentrations in hyporheic water had exclusively negative slopes, indicating source-limited delivery, while the other two urbanized streams maintained largely chemostatic behavior. Average specific conductance and nitrate + nitrite concentrations in stream surface water reflected an urbanization gradient, while sulfate, Ca, K and Sr concentrations suggested a threshold effect: the stream with a mostly forested watershed had the lowest concentrations, while the other two were higher and similar. Specific conductance indicated salinization of both surface and groundwater at the two more urban streams, possibly threatening aquatic organisms. Metal concentrations in surface and subsurface water were often positively correlated with specific conductance and negatively correlated with pH, suggesting that they may originate from road salt and/or be mobilized by acid precipitation. These results indicate the importance of monitoring both baseflow and stormflow as pathways for pollution.