Stream Water Sources Research Articles

The age and sources of stream water in a boreal forest watershed in the permafrost region: a case study of a watershed in northeast China

Determining the age and sources of stream water is critical for understanding the watershed hydrological processes and biogeochemical cycle. In this study, daily isotope data of rainfall and runoff, as well as continuously monitored conductivity data from June to October in 2019 in-Laoyeling(LYL) watershed located in permafrost region of northeastern China were used to separate streamflow components through the application of two independent methods: isotope-based hydrograph separations (IHS) and the conductivity mass balance (CMB) methods. The results showed that stream water in a boreal forest watershed with permafrost of the Daxing’an Mountains is mainly composed of pre-event water. Although the IHS method is more sensitive and provides more details than the CMB method, the results of both methods show a similar trend. The average value of the young water fractions (Fyw) for those aged less than 65 days is 5.6%, while the mean transit time (MTT) was calculated to be 3.33 years. These findings enhance our understanding of the fundamental characteristics of runoff generation mechanisms and changes in runoff components in permafrost regions. Such knowledge is crucial for effective regional water resource management under the context of climate change, such as construction of water conservancy facilities and prediction of flood and drought disasters.

Evaluation of Legacy Forest Harvesting Impacts on Dominant Stream Water Sources and Implications for Water Quality Using End Member Mixing Analysis

Forests are critical water supply regions that are increasingly threatened by natural and anthropogenic disturbance. Evaluation of runoff-generating processes within harvested and undisturbed headwater catchments provides insight into disturbance impacts on water quality and drinking water treatability. In this study, an extensive hydrologic dataset collected at the experimental Turkey Lakes Watershed (TLW) located on the Canadian Shield was used to quantify sources of stormflow in legacy clear-cut (24-years post harvesting) and forested (control) headwater catchments using an end member mixing analysis (EMMA) model. Stream water, groundwater, soil water, and throughfall water quality were evaluated during spring snowmelt, stormflow, and fall wet-up. Groundwater chemistry was similar to stream water chemistry in both catchments, suggesting that groundwater is a major contributor to stream flow. The water chemistry in small wetlands within the study catchments was comparable to stream water chemistry, suggesting that wetlands are also important contributors to stream flow. Differences in wetland position between the legacy clear-cut and control catchments appeared to have a greater influence on source contributions than legacy harvesting. Results from this study provide insight into runoff-generation processes that reflect event/seasonal flow dynamics and the impacts on water quality.

Improving the representation of stream water sources in surrogate nutrient models with water isotope data

An important part of meeting nutrient reduction goals in the lower Great Lakes basin and assessing the success of different land management strategies is modeling nutrient losses from agricultural land. This study aimed to improve the representation of water source contributions to streamflow in generalized additive models for predicting nutrient fluxes from three headwater agricultural streams in southern Ontario monitored during the Multi-Watershed Nutrient Study (MWNS). The previous development of these models represented baseflow contributions to streamflow using the baseflow proportion derived using an uncalibrated recursive digital filter. Recursive digital filters are commonly used to partition stream discharge into separate components from slower and faster pathways. In this study, we calibrated the recursive digital filter using stream water source information from stable isotopes of oxygen in water. Across sites, optimization of the filter parameters reduced bias in baseflow estimates by as much as 68 %. In most cases, calibrating the filter also improved agreement between filter-derived baseflow and baseflow calculated from isotope and streamflow data: the average Kling-Gupta Efficiencies using default and calibrated parameters were 0.44 and 0.82, respectively. When incorporated into the generalized additive models, the revised baseflow proportion predictor was more often statistically significant, improved model parsimony, and reduced prediction uncertainty. Moreover, this information allowed for a more rigorous interpretation of how different stream water sources influence nutrient losses from the agricultural MWNS watersheds.

Hydroclimate Drives Seasonal Riverine Export Across a Gradient of Glacierized High‐Latitude Coastal Catchments

AbstractGlacierized coastal catchments of the Gulf of Alaska (GoA) are undergoing rapid hydrologic fluctuations in response to climate change. These catchments deliver dissolved and suspended inorganic and organic matter to nearshore marine environments, however, these glacierized coastal catchments are relatively understudied and little is known about total solute and particulate fluxes to the ocean. We present hydrologic, physical, and geochemical data collected during April–October 2019–2021 from 10 streams along gradients of glacial fed to non‐glacial (i.e., precipitation) fed, in one Southcentral and one Southeast Alaska region. Hydrologic data reveal that glaciers drive the seasonal runoff patterns. The ẟ18O signature and specific conductance show distinctive seasonal variations in stream water sources between the study regions apparently due to the large amounts of rain in Southeast Alaska. Total dissolved solids concentrations and yields were elevated in the Southcentral region, due to lithologic influence on dissolved loads, however, the hydroclimate is the primary driver of the timing of dissolved and suspended yields. We show the yields of dissolved organic carbon is higher and that the δ13CPOC is enriched in the Southeast streams illustrating contrasts in organic carbon export across the GoA. Finally, we illustrate how future yields of solutes and sediments to the GoA may change as watersheds evolve from glacial influenced to precipitation dominated. This integrated analysis provides insights into how watershed characteristics beyond glacier coverage control properties of freshwater inputs to the GoA and the importance of expanding study regions to multiple hydroclimate regimes.

Molecular Characterization and Antibiogram of Selected Pathogens Isolated from Streams and Wells Water Sources in Three Local Government Areas of Rivers State, Nigeria

Aims: Reliance on unhealthy water sources such as hand dug wells and streams have led to the occurrence of waterborne diseases such as amoebic dysentery, gastroenteritis, typhoid fever and cholera among several communities in Rivers State. This study tends to identify selected multidrug resistant pathogens isolated from streams and wells water sources in three Local Government Areas of Rivers State using molecular techniques.
 Methodology: A total of 48 well and stream water samples were collected aseptically from 24 sampling sites in Ikwerre, Emohua and Etche Local Government Areas of Rivers State. Samples were analysed using membrane filtration technique for total heterotrophic bacterial count and total coliform count. The well and stream water samples were also cultured for E. coli, Salmonella and Vibrio sp. Antibiotic sensitivity test of the isolates was carried out using the disk diffusion method and multidrug resistant isolates were identified using PCR-based techniques (16S rRNA).
 Results: The results of this study showed that total aerobic heterotrophic bacteria count occurred more in Emohua LGA for both well and stream water sources with bacterial count of 1.71 x104 cfu/ml for well water samples and 2.35 x 104 cfu/ml for stream water samples. The mean fungal count of the stream water samples was highest in Emohua LGA with 2.55 x 104 cfu/ml followed by Ikwerre LGA which had 4.20 x 103 cfu/ml and Etche LGA with the least count of 1.80 x 102 cfu/ml. All the isolated bacteria species were found to be resistant to more than 50% of the antibiotics used with highest Multi Antibiotic Resistant Index of 0.625. multidrug resistant bacterial isolates identified include Vibrio sp strain 201707CJKOP-Y162 (MG593726), Bacillus sbtilis clone N55 (JQ622582), Chryseobacterium sp strain CB2915-325-DE_0621 (MH512534), Enterobacter sp strain AB55 (MF407145), Klebsiella pneumonia strain M792-16(MH680830), Shigella sonnei strain AR_0030(CP032523), Escherichia coli strain WECHEC025943(CP027205) and Salmonella bongori strain KC153129.116 (MG663494).
 Conclusion: Access to good quality or potable drinking water and efficient sanitary practices are fundamental to human health and economic development. The occurrence of multidrug resistant pathogenic bacterial isolates in natural water sources requires serious routine evaluation in order to forestall the outbreak of waterborne disease epidemics.

Improving the Representation of Stream Water Sources in Surrogate Nutrient Models with Water Isotope Data

Improving the Representation of Stream Water Sources in Surrogate Nutrient Models with Water Isotope Data

Bacteriological Quality Assessment of Well and Stream Water Sources from Ikwerre, Emohua and Etche Local Government Areas of Rivers State

Background: Majority of the human population in semi-urban and urban areas in Nigeria are heavily reliant on well and stream water as the main source of water supply for drinking and domestic use due to the inadequate provision of potable pipe borne water. These groundwater sources can easily be fecally contaminated and thus, increase the incidence and outbreaks of preventable waterborne diseases. This study was carried out to determine the bacteriological quality of some well and stream waters sources in Ikwerre, Emohua and Etche Local Government Areas of Rivers State.
 Methodology: Twenty-four sampling sites with 8 from each Local Government Area were randomly selected for this study. A total of 48 samples, 2 from each of the sites were collected aseptically for 12 months. Samples were analysed using membrane filtration technique for total heterotrophic bacterial count and total coliform count. The well and stream water samples were also cultured for E. coli, Salmonella, and Vibrio sp.
 Results: The results show that Emohua Local Government Area had the highest total heterotrophic bacterial count of 5.2 x 103 cfu/ml. This was followed by Ikwerre LGA with total bacterial count of 4.3 x 102 cfu/ml, while Etche LGA had 3.1 x 102 cfu/ml. The total coliform count ranged from 25 cfu/100ml to 50 cfu/100ml for the three LGA’s, whereas the faecal coliform count was between 12 cfu/100ml and 20 cfu/100ml. The total coliform, E. coli, Salmonella and Vibrio counts from the three local government areas occurred above the WHO stipulated zero count in 100ml of water.
 Conclusion: The results from this study showed contamination of all the wells studied with faecal coliforms thus, indicating the presence of other enteric pathogens and a potential source for waterborne disease outbreaks. Well water in Ikwerre, Emohua and Etche Local Government Areas of Rivers State are not safe for drinking without additional treatment like disinfection or boiling. Periodic testing and constant monitoring of these water sources should also be done to meet up with the World Health Organization Standards in the provision of safe, clean drinking water.

Use of stable Mg isotope ratios in identifying the base cation sources of stream water in the boreal Krycklan catchment (Sweden)

The knowledge of the sources of base cations in stream water is a prerequisite to assess potential effects of changing environmental conditions such as changing rainfall, weathering or groundwater flows on cation export with stream water. This study use stable Mg isotopes to identify potential sources in the well-studied catchment of Krycklan located on gneissic bedrock covered by quaternary sediments in Sweden. Samples were collected from open filed rain, throughfall, stream, soil, rock and litterfall. The δ26Mg values of these samples was determined and the contributions of different sources to Mg fluxes in the stream were determined from the variation of the Mg isotope and Sr / Mg ratios.The results show an overall variation of 1.10‰ between all samples. In addition, Magnesium isotope ratios varied little in the streamwater and in soil solution, except during snowmelt periods during which a large portion of the annual runoff occurs. Magnesium in the streamwater is explained as a mixture of three pools (open field rain, soil solution and groundwater) with the latter two influenced by catchment processes. Outside the snowmelt period, Mg in streamwater mainly derived from the groundwater, assumed to be mineral weathering signature in this catchment, with a contribution ranging from 12 to 63% to Mg fluxes. Open field rain dominates Mg fluxes in streamwater during spring flood (0 to 78%) and may contribute significantly during larger summer and autumn rainfall events. Soil solution input to streamwater range from 16 to 59% of Mg fluxes in streamwater. Our results demonstrate that δ26Mg values together with Mg concentrations and Sr/Mg ratios can be used to constrain the Mg sources of stream water and quantify weathering release rates.

Isotope hydrology and water sources in a heavily urbanized stream

AbstractComplex networks of both natural and engineered flow paths control the hydrology of streams in major cities through spatio‐temporal variations in connection and disconnection of diverse water sources. We used spatially extensive and temporally intensive sampling of water stable isotopes to disentangle the hydrological sources of the heavily urbanized Panke catchment (~220 km2) in the north of Berlin, Germany. The isotopic data enabled us to partition stream water sources across the catchment using a Bayesian mixing analysis. The upper part of the catchment streamflow is dominated by groundwater (~75%) from gravel aquifers. In dry summer periods, streamflow becomes intermittent in the upper catchment, possibly as a result of local groundwater abstractions. Storm drainage dominates the responses to precipitation events. Although such events can dramatically change the isotopic composition of the upper stream network, storm drainage only accounts for 10%–15% of annual streamflow. Moving downstream, subtle changes in sources and isotope signatures occur as catchment characteristics vary and the stream is affected by different tributaries. However, effluents from a wastewater treatment plant (WWTP), serving 700,000 people, dominate stream flow in the lower catchment (~90% of annual runoff) where urbanization effects are more dramatic. The associated increase in sealed surfaces downstream also reduces the relative contribution of groundwater to streamflow. The volume and isotopic composition of storm runoff is again dominated by urban drainage, though in the lower catchment, still only about 10% of annual runoff comes from storm drains. The study shows the potential of stable water isotopes as inexpensive tracers in urban catchments that can provide a more integrated understanding of the complex hydrology of major cities. This offers an important evidence base for guiding the plans to develop and re‐develop urban catchments to protect, restore, and enhance their ecological and amenity value.

Effects of Heterogeneous Stream‐Groundwater Exchange on the Source Composition of Stream Discharge and Solute Load

AbstractThe exchange of water and solutes between the stream and groundwater along a stream network affects the source composition of discharge and solute load in the stream. To date, this hydrologic turnover has only been analyzed with respect to the exchange of water. In this study, we extend the concept of hydrologic turnover to solutes and analyze the effects of different hydrologic conditions on the spatial patterns and magnitude of exchange fluxes. Based on a coupled stream‐groundwater model built in MODFLOW using the Streamflow‐routing package, we simulated stream‐groundwater exchange along a stream of 30 km in length and evaluated the evolution of stream water source composition under different precipitation and streamflow conditions. Results show that even for highly variable hydrologic conditions, the direction of stream‐groundwater exchange (loss/gain) remained unchanged in consistently gaining or losing reaches, but changed in interspersed transitional reaches. The comparison between the source composition of discharge and nitrate load in stream water revealed a decoupling of discharge and solute load contribution from groundwater to the stream, as zones of high water gains do not necessarily coincide with zones of high solute concentrations. Overall, nearly 80% of total groundwater contributions to the outflow of water from the catchment were generated over only 20% of the total stream length. Our research highlights the importance of distinguishing water and solute load contributions to streams. This in turn implies that to reduce groundwater‐borne nutrient loads to streams, measures need to focus on the specific reaches with highest load contributions.

Estimating the sources of stream water in snow dominated catchments of western Himalayas

Snow and glaciers are important freshwater resources in the Himalayan catchments for all biological activities. However, under recent climate change, these resources are decreasing, thereby posing a serious threat to the future freshwater resources among the Himalayan catchments. Therefore, understanding the hydrological behaviour and sources of streamflow is necessary for better assessment, planning and management of these waters in the mountainous catchments. This study is based on the use of δ18O and d-excess to identify and estimate the different sources of streamflow in the western Himalayas. The isotopic composition of different source waters varied over space and time. These variabilities are attributed to the seasonal meteorological changes, precipitation form, differential melting of snowpacks and moistures sources. The vertical isotope gradients were observed between the sampling sites and the elevation of the basin. The results suggest that snow and snowpack dominantly (up to 55%) contribute to the streamflow during high flow period, while as groundwater maintains the flow in the streams during lean period and contributes up to 78%. The study provides the important insights about the understanding of spatio-temporal variability of different source waters contributing to runoff. In addition, the changing climate could have serious impact on the water resources of the region and thereby affecting the economic and social values of the downstream populations.

Sources and biodegradability of dissolved organic matter in two headwater peatland catchments at the Marcell Experimental Forest, northern Minnesota,USA

AbstractWhere they are present in catchments, peatlands are a dominant source of dissolved organic matter (DOM) to surrounding waterways due, in part, to high production rates. Despite the preponderance of peatlands in northern latitudes and expected peatland vulnerability to climate change, little is known about peatland DOM degradation relative to a more comprehensive understanding of degradation when DOM is sourced from upland‐dominated catchments. We compared DOM biodegradability of various sources of stream water in two catchments having peatlands (22%–33% of the area) surrounded by upland forests (70%–90% of the area, either deciduous or coniferous). We measured total organic carbon (TOC), and biodegradable dissolved organic carbon concentrations; bacterial respiration rates; streamflow; and upland runoff during and after snowmelt (March to June, 2009–2011). We also explored if DOM in upland runoff stimulated biodegradation of peatland‐derived DOM (i.e., a priming effect), and if forest cover type affected DOM biodegradability. As expected, the peatlands were the largest sources of both water (72%–80%) and TOC (92%–96%) to the streams although more area in each catchment was in uplands (70%–90%). Several results were unexpected, yet revealing: (1) DOM from peatlands sometimes had the same biodegradability as DOM from uplands, (2) upland sources of DOM had negligible effects on biodegradability in the peatland and downstream, and (3) upland deciduous cover did not yield more degradable DOM than conifer cover. The most pronounced effect of upland runoff was dilution of downstream TOC concentrations when there was upland runoff. Overall, the effects of upland DOM may have been negligible due to the overriding effect of the large amount of biodegradable DOM that originated in bogs. This research highlights that peatland‐sourced DOM has important effects on downstream DOM biodegradability even in catchments where upland area is substantially larger than peatland area.

Stormflows Drive Stream Carbon Concentration, Speciation, and Dissolved Organic Matter Composition in Coastal Temperate Rainforest Watersheds

AbstractStream water carbon concentrations can be highly dynamic on the time scales of both individual storm events and seasonal hydroclimatic shifts. We collected stream water daily over a 6‐day storm from three headwater subcatchments of varying landcover (poor fen, forested wetland, and upland forest) and the catchment outlet to evaluate how precipitation events impact the concentration and speciation of carbon (organic vs. inorganic) as well as the composition of dissolved organic matter (DOM) exported laterally from coastal temperate rainforest catchments. Dissolved and particulate organic carbon concentrations increased during the storm at all sites, while dissolved inorganic carbon concentrations were diluted during peak flows. These results highlight the importance of quantifying all forms of lateral carbon export when evaluating the role of storms in catchment‐scale carbon cycling. Isotopic hydrograph separation using stream water δ18O showed that percent new water was significantly related to carbon concentration and form providing a clear link between stream water sources (i.e., recent event water) and soil carbon source areas that become connected to surface water during storms. Furthermore, ultrahigh‐resolution mass spectrometry showed that stream water DOM exported from the upland forest contained the greatest molecular diversity of the three landscape types and had the largest changes in composition over the storm suggesting that the wetland‐dominated subcatchments were less compositionally diverse with regard to soil DOM pools active during the storm. Overall, this study provides insight into hydro‐biogeochemical drivers that control lateral carbon export from forested catchments in a region where an increasing fraction of precipitation is falling as rain.

Nitrate removal and young stream water fractions at the catchment scale

AbstractDespite extensive research on nitrate export and removal, nutrient contamination remains a major threat to water bodies worldwide. At the local scale, nitrate removal is governed by biogeochemical conditions that vary in space and time, making integration to entire landscapes critical. Water transit times have often been used to describe solute transport, but the relation between water age and nitrate removal at the catchment scale is still poorly understood. We test the hypothesis that nitrate removal peaks when the fraction of young water in discharge is at its minimum, because nitrate removal occurs mostly under dry conditions where deeper, older groundwater dominates streamflow. We tested this hypothesis by exploring a detailed water quality record from the Kervidy–Naizin catchment (FR) and comparing the dynamics of nitrate to those of a conservative solute (chloride). We find that estimates of nitrate removal are consistent with previous estimates at the site and they show a good (inverse) correlation with the fraction of streamflow that is younger than 2.5 months. However, this young water fraction cannot be used to predict nitrate removal in the winter–spring period, when no removal is observed regardless of streamflow age. While this leads us to reject our hypothesis during the winter period, it also suggests that water age distributions and their correlation with nitrate removal can possibly reveal distinct sources of stream water at different hydrologic regimes and relevant biogeochemical reactions.

Combined use of stable isotopes and hydrochemical characteristics to determine streamflow sources in the Jonkershoek catchment, South Africa

ABSTRACT The stable isotopes of water (18O, 2H) and other hydrochemical properties were used to assess seasonal changes between sources of stream water and flow pathways in baseflow conditions for two headwater sub-catchments (∼3 km2) of the Jonkershoek, a mountainous catchment in the Western Cape of South Africa. The sub-catchments differ in land cover, one is dominated by indigenous fynbos vegetation and the other by pine plantation. Stream water, higher elevation springs, and lower elevation groundwater samples were collected monthly from January 2018 to January 2019, and were analysed for stable isotopes, electrical conductivity (EC) and pH. The stream water isotopic values resembled those of groundwater during the dry and wet seasons. Results indicated a steady contribution of spring discharge to streams during the dry season, with rainfall contribution less evident. Wet season flows were attributed to interflow including perennial and ephemeral springs. Spatial variations in EC between the sub-catchments were indicative of a greater proportional input from subsurface water, more evaporation and/or more mineral dissolution in the pine-dominated sub-catchment. The spatiotemporal variability in EC was significantly larger than for the stable isotopes. These findings enabled conceptualization of streamflow generation processes that can support strategic water resource management practices in this region.

Recharge pathways and rates for a sand aquifer beneath a loess-mantled landscape in western Tennessee, U.S.A.

Study region: Western Tennessee, U.S.A. Study focus: Recharge to aquifers that underlie loess and other fine-grained surficial deposits in western Tennessee as well as other areas is commonly impeded resulting in sensitivity in regard to sustainability of groundwater resources. This study investigates the role of preferential pathways of recharge to the regional Memphis aquifer in an area mantled by loess and fine-grained paleosols. New hydrological insights: Data gathered through a vadose-zone chloride mass balance analysis and a year of monitoring physical hydrologic, water chemistry, and environmental and applied tracer data within an upland watershed in western Tennessee indicate that recharge to the Memphis aquifer is dominated by lateral recharge of infiltrated stream water sources rather than vertical infiltration through loess-covered uplands. The results from this research challenge prevailing models of recharge to the Memphis aquifer and aquifers mantled by loess or other fine-grained soils in other regions that envision vertical recharge through fine-grained soils to be the dominant recharge mechanism.

The Importance of Interflow to Groundwater Recharge in a Snowmelt‐Dominated Headwater Basin

AbstractUnderstanding the sensitivity of groundwater generation to climate in a mountain system is complicated by the tight coupling of snow dynamics to vegetation and topography. To address these feedbacks, we combine light detection and ranging (LiDAR)‐derived snow observations with an integrated hydrologic model to quantify spatially and temporally distributed water fluxes across varying climate conditions in a Colorado River headwater basin. Results indicate that annual groundwater flow is an important and stable source of stream water. However, interflow decreases during drought as a function increased plant water use and the relative fraction of groundwater to streams increases. Seasonal snowmelt and vegetation water use regulate small recharge rates in the lower portions of the basin, but snowmelt transported via interflow from high mountain ridges toward convergent topographic zones defines preferential recharge in the upper subalpine. Recharge in this zone appears decoupled from annual climate variability and resilient to drought.

Studies on parasitic contamination of soil and local drinking water sources, Doma Local Government Area, Nasarawa State, Nigeria

Water is essential to all living things on earth, however if contaminated, can be injurious to human health when consumed. This study evaluates the parasitic contamination of potable water sources and surrounding soil in Doma Local Government Area of Nasarawa State. Forty-eight soil and water samples from different sources (wells, streams and boreholes) were collected from March to July 2017. Water samples were analyzed using the Calcium carbonate (CaCO 3 ) floatation method while a modified Baermann Technique was used to microscopically examine soil samples for the parasitic presences. 32 water samples were parasitized including 2 protozoans ( Entamoeba histolytica , and Giardia lamblia) 3 nematodes ( Trichuris trichiura , Ascaris lumbricoides and hookworm), and Fasciola hepatica a trematode. The nematodes were most contaminated 19(59.38%) while trematodes were least 1(3.13%). The most contamination was in stream water sources for late dry and early wet season (69.23% and 94.74%) while the boreholes had no contamination for both seasons. Prevalence of parasites in relation to water sources showed a high significant difference ( p = 0.0000001), while there was no significant difference in relation to late dry and early rainy seasons ( p = 0.1258). Geohelminths was highest around the boreholes 15(35.71%) but least in the streams 13(30.95%). However, there was no significant difference ( p = 0.6221) in the prevalence rate of geohelminths in relation to sources of water. Result indicated a high rate of parasitic contamination of soil and drinking water sources in the study=area. Hence there is need for advocacy and enlightenment on the importance of proper drinking water treatment. Keywords: Geohelminths; parasitic contamination; water

Distribution and potential ecological risk assessment of trace elements in the stream water and sediments from Lanmuchang area, southwest Guizhou, China.

Trace elements contamination in sediment is regarded as the global crisis with a large share in developing countries like China. Water and sediment samples were collected during (2016) from Qingshui Stream and analyzed for major physicochemical properties and trace elements by using ICP-MS. Our result of sediments showed that studied trace elements (except Pb, Cd, Co) had a concentration higher than Chinese sediment guideline as well as stream water data for studied trace elements (except Cr, Pb, Cd, Cu, and Zn) had a higher concentration than the maximum permissible safe limit of WHO. Contamination factor (CF) confirmed a moderate to high contamination in the sediment samples due to As and Tl, respectively. The values of pollution load index (PLI) were found above one (> 1), describing the progressive sediment quality decline. Pearson correlation showed that there was a significant positive association between Tl and As (r = 0.725, p < 0.05) in sediment samples. Results revealed that water-rock interaction, weathering of Tl sulfide mineralization, and hydrogeological conditions were major sources of stream water and sediments contamination in the study area. This experimental study contributes to a better understanding of the geochemistry and prevention of trace element contamination in sediments from Lanmuchang area.

Freshwater pearl mussels as a stream water stable isotope recorder

AbstractFor several decades, stable isotopes have been a commonly used and effective tool for flow path analysis, stream water source apportionment, and transit time analysis. The Global Network of Isotopes in Precipitation repository now has monthly precipitation isotope time series extending over several years and even decades in some settings. However, stream water isotope composition time series remain rather short with only very few data sets spanning over more than a few years. A critical challenge in this respect is the collection of stream water isotope data sets across a wide variety of headwater streams and for long durations. We rely on a new approach for stream signal reconstruction based on freshwater mussels, specifically the freshwater pearl mussel Margaritifera margaritifera. We use secondary ion mass spectrometry (SIMS) to quantify oxygen isotope ratios in pearl mussel shell growth bands. In our study area, the observed seasonal variability in precipitation δ18O values ranges between −15‰ and −3‰. This input signal is strongly damped in stream water, where observed values of δ18O range between −10‰ and −6.5‰. These values are consistent with our measured average shell‐derived stream water δ18O of −7.19‰. Along successive growth bands, SIMS‐based stream water δ18Ow values varied within a seasonal range of −9‰ to −5‰. The proposed SIMS‐based shell analysis technique is obviously well suited for analysing isotopic signatures of O in shell material—especially from the perspective of reconstructing historical series of in‐stream isotope signatures.