Water Chemistry Variables Research Articles

Assessment of water quality variation: tool for effective water treatment system operations

Water quality and treatment systems are dynamic because they constantly undergo seasonal variations in water chemistry, varying plant operating conditions, and new environmental laws, among others. Because of this, proper monitoring is essential to ensure that the water supplied by the treatment system safeguards public health from waterborne diseases. Selected surface water quality parameters as inflow were obtained before treatment against the treated water for different hydrological periods (2009 – 2019) from a water treatment system to determine the trend in water quality variation, water quality index, and effectiveness of the treatment process. Each hydrologic year had varying concentrations of selected parameters for raw and treated water quality. The concentration values of pH, electrical conductivity, total hardness, calcium and magnesium hardness, chloride, and total dissolved solids of the natural source water were within the recommended limit. Turbidity concentrations were above the recommended value for each hydrologic year, values ranging from 14.65 – 57.98 NTU, and iron concentration was above the permissible for 2010 and 2012. Selected parameters were all within the threshold limit after treatment with a water quality index (WQI) ranging between 1.09 – 39.39, rated as good/excellent water quality. The treatment system operations were effective throughout the observation period. However, turbidity, iron and hardness should be tested more frequently during the operational and verification monitoring process.

Spatiotemporal distribution of cyanobacteria in relation to water chemistry of Sutlej River, Punjab (India).

In this investigation, the spatiotemporal distribution of cyanobacteria and their relationships with variations in water chemistry (physico-chemical parameters and heavy metal) of Sutlej River, Punjab (India) has been analyzed by employing multivariate statistical methods. Sutlej River exhibits a rich array of cyanobacterial diversity, comprising 28 species across 15 genera, distributed among 11 families and spanning 5 orders within the class Cyanophyceae. In terms of relative abundance, Microcystis aeruginosa (17.47%) was documented as the most abundant taxa followed by Microcystis robusta (16.55%), Merismopedia punctata (11.03%), Arthrospira fusiformis (6.67%) and Pseudanabaena galeata (3.68%). Significant variations were observed among sampling sites in most of the physico-chemical parameters. Principal Component Analysis delineated sampling sites into two discernible groups according to variations in water chemistry. River Pollution Index (RPI) showed that river water is under the unpolluted (RPI 1.5) to negligibly polluted category in the upstream sites, while moderately polluted (RPI 5.5) in the downstream sites. Heavy metal Pollution Index (HPI) revealed consistent heavy metal contamination at sites RWS7 and RWS8 across all seasons. Conversely, site RWS1 consistently exhibited lower HPI values throughout the three studied seasons. Further, Canonical Correspondence Analysis identified that pH, TDS, TA, NO3, Na, and NH4 are the key physicochemical parameters which affect the spatiotemporal distribution of cyanobacteria in the studied river system. Overall, this study will offer significant information for hydrologists, ecologists, and taxonomists to develop future holistic strategies for further monitoring of the Sutlej River and other similar habitats.

A survey of water chemistry used in zebrafish facilities and their effects on early zebrafish development.

There are a variety of published standard methods and water chemistry recommendations for zebrafish ( Danio rerio) husbandry, but empirical evidence for their justification is often lacking, as is information on some variables that have important biological effects on fish. Importantly, these different recommendations could contribute to variability in results and fish welfare between or within institutions. Here we document the current range of water chemistry used by various research institutions around the world and report initial findings on their effects on the development and growth of zebrafish. Over 40 institutes responded to a survey that revealed a large variation in water chemistry used for zebrafish husbandry including differences in the set-points and acceptable ranges for temperature, pH and conductivity. In subsequent experiments, zebrafish ( D. rerio, WIK) embryos/larvae exposed to a large range of salt concentrations (50μM to 10mM Na + or 30 - 2500 μS/cm) and CO 2 levels (400 - 8,000 μatm). Larvae exposed to the lowest salt concentration (5 μM Na + or < 30μS/cm) had a slower response to touch and their swim bladders were not inflated. Larvae exposed to 5-100 μM Na + were 5 % shorter in total body length than those exposed to higher salt concentrations (>100 μM Na +). Zebrafish embryo/larvae exposed to intermediate pCO 2 values (~2000 μatm) were 1 to 3.5% longer than those exposed to either ambient (400 μatm) or higher (4000 μatm) pCO 2, but pCO 2 did not affect developmental endpoints up to 4 dpf. Overall, we highlight the magnitude of variation in water chemistry used within zebrafish research and provide some empirical evidence to show that not all of these water conditions might be optimal for developing zebrafish and reproducibility of research, although further research is necessary to determine longer-term effects of water chemistry on older larvae, juveniles and adults.

In-depth analysis of the removal mechanisms behind neonicotinoid pesticides and bimetal ZIF derived-magnetic carbon

Emerging organic contaminants, such as pesticides, pose significant environmental challenges and necessitate the development of advanced materials and technologies for their efficient removal. This study explored various morphologies of bimetal ZIF-derived magnetic carbon for the removal of three representative neonicotinoid pesticides from water. Among the materials investigated, Co-NP3-1000, carbonized at 1000℃ from Zn/Co-ZIF with a Zn/Co molar ratio of 3:1, demonstrated outstanding adsorption performance, even in the presence of varying water chemistry parameters (e.g., humic acid and particulate matter), and effectively removed neonicotinoid pesticides at low concentrations from diverse actual water samples. Due to its strong magnetic properties, Co-NP3-1000 could be easily separated from solutions and maintained over 70% adsorption efficiency after five consecutive cycles. Moreover, Co-NP3-1000 exhibited high efficiency in removing other neonicotinoid pesticides (i.e., acetamiprid, nitenpyram, and thiamethoxam). Microstructure analysis and density functional theory calculation identified pore filling, hydrogen bonding, and π-π interactions as the primary forces driving NEOs adsorption. Notably, the relative contribution of these interactions was quantitatively assessed across different solution pH levels, and their sequence was elucidated using two-dimensional Fourier transform infrared correlation spectroscopy. This work advances both the design of versatile materials for the removal of emerging organic contaminants and quantitative insights into the interaction mechanisms between advanced adsorbents and these contaminants.

Trends of water composition and discharge in the Ramganga River, Ganga Basin over the last 40 years signal enhanced nitrate flux

Studying long-term trends in river water chemistry is critical to assessing the impacts of human activities and climate change on water resources. This is of particular importance in the Indian subcontinent such as the Ganga River Basin – home to nearly 500 million people. As previous studies are mostly focused on seasonal to annual scale variabilities, the long-term riverine changes in the hydrochemistry of the rivers draining the Ganga Basin remain poorly constrained. Here we present the river chemistry and discharge data of Ramganga Basin, a major sub-catchment of Ganga River, for three hydrological stations between 1981 and 2020. Our results indicate that the total concentration of dissolved solids (TDS) within the Ramganga basin varies from 123 to 1170 mg/L and does not show a systematic spatiotemporal trend. However, we found that the fluxes of certain dissolved inorganic constituents from Ramganga Basin have significantly increased in the last 40 years with NO3– having the highest trend followed by Ca2+, Cl−, K+, SiO2, F−, and PO43−. The concentration-discharge (C–Q) analysis suggests a dominant dilution behaviour for most of the major solutes in the basin at longer timescales. We find that the cations and anions riverine loads are primarily dominated by Ca2+ and HCO3– ions, respectively, controlled by rock weathering processes, whereas the fluxes of NO3–, PO43−, and SO42− are controlled by anthropogenic processes. In summary, the long-term dataset for the Ramganga River revealed significant variability in river water chemistry, solute fluxes, and C–Q relationships over the last 40 years controlled by natural and anthropogenic processes.

Spatial variability in water strontium isotopes and trace metals from the Clarence River Basin, New South Wales, Australia

Understanding fish movement in river systems is essential in identifying habitats which are important for species to perpetuate. Water chemistry, paired with fish otoliths, can be used to trace movements among different habitats, although a detailed understanding of spatial variation in water chemistry is first required. To obtain this knowledge, we analysed surface water collected from 59 sites throughout the Clarence River Basin, a coastal river basin in northern New South Wales, Australia. The primary objective was to quantify the spatial variation of trace metals and strontium isotope ratios (87Sr:86Sr) for future and paired use with otolith microchemistry to track fish movement. Using ICP-OES, we identified that some trace metals, particularly strontium and barium as well as 87Sr:86Sr ratios, varied spatially when analysing all water samples and revealed three distinct regions centring around the estuary, interior and outer regions. These differences were driven by variation in the underlying surface geology between the Clarence–Moreton Basin and the New England Block. Tidal influence also affected trace metals and 87Sr:86Sr ratios throughout the estuarine area. We suggest that the level of differentiation identified in the current study has the potential to discriminate broad-scale fish movements among regions/habitats using otolith analysis, with fine scale movements best elucidated using complementary techniques.

Seasonal variation in metabolic profiles and microbial communities in a subarctic ore processing plant.

The mining industry strives to reduce its water footprint by recycling water in ore processing. This leads to build-up of ions, flotation chemicals and microbial biomass, which may affect the process. The Boliden Kevitsa mine in Northern Finland is exposed to seasonal change and recycles up to 90% of the process water. We studied the variation in size, composition and putative functions of microbial communities in summer and winter in the ore processing plant. The raw water, Cu and Ni thickener overflow waters had statistically significantly higher bacterial numbers in winter compared to summer, and specific summer and winter communities were identified. Metagenomic analysis indicated that Cu and Hg resistance genes, sulphate/thiosulphate, molybdate, iron(III) and zinc ABC transporters, nitrate reduction, denitrification, thiosulphate oxidation and methylotrophy were more common in winter than in summer. Raw water drawn from the nearby river did not affect the microbial communities in the process samples, indicating that the microbial communities and metabolic capacities develop within the process over time in response to the conditions in the processing plant, water chemistry, used chemicals, ore properties and seasonal variation. We propose that the microbial community structures are unique to the Boliden Kevitsa mine and processing plant.

Key factors influencing Hg levels and trends in unperturbed oligotrophic temperate and boreal lakes

Mercury (Hg) is a toxic metal that presents a major risk to ecosystems, biota, human health, and remains a priority concern. In temperate and boreal lakes Hg and methylmercury (MMHg) are expected to vary as a function of atmospheric Hg deposition, lake water chemistry, catchment characteristics and climate variables. The aim of this study was to quantify Hg and MMHg in unperturbed oligotrophic lakes and to identify the factors controlling their distribution. We first hypothesized that lake Hg (and MMHg to lesser extent) spatial variations are linked to atmospheric deposition, catchment characteristics, and terrestrial exportation of dissolved organic carbon (DOC). We secondly examined if lake Hg concentrations have followed the decrease in atmospheric Hg emission observed between the mid-1990s to the end-2010s. We found that overall, atmospheric Hg has little impact on lake Hg and MMHg concentrations, which are both primarily influenced by DOC input originating from the forest catchment. The relationship between DOC and Hg differed between the spring and the fall, with a Hg-to-DOC ratio twice as high in spring. This seems related to snowmelt input of Hg (with a relatively reduced input of DOC) or the internal lake build-up of Hg during the ice-covered period. Of the 10 lakes intensively visited over a 20-year period, only 3 showed significant lake Hg decreases despite significant negative trends in atmospheric Hg concentrations, suggesting a lag between atmospheric and surface water temporal trends. Overall, terrestrial catchments retain around 80% of atmospheric Hg implying that large Hg pools have been built up in soils in the last decades. As such, the reduction of atmospheric Hg alone will not necessarily result in Hg decreases in lakes, since the Hg concentrations may be modulated by DOC export trends and catchment characteristics. This stresses the need to improve our understanding of the processes governing Hg transfers from catchments into lakes.

A simple methodology for in situ study of microplastics’ aggregation

AbstractDue to the critical impacts of microplastic (MP) aggregation on their fate, mobility, and bioavailability, this study developed a simple approach to examine their aggregation under varying water chemistry and MPs’ surface aging conditions. An accelerated photodegradation experiment was conducted for 6 weeks. The water chemistry conditions varied by altering pH, using natural organic matter (NOM), and conducting experiments in ultrapure water and synthetic stormwater. The surface chemistry analysis of photodegraded MPs revealed the formation of carbonyl and vinyl functional groups. Zeta potential measurements revealed a more negative surface charge for photodegraded MPs compared to new MPs. The aggregation kinetics of MPs were studied by comparing the number of MP clusters formed over time after intense dispersion in water. The results showed that the presence of NOMs reduces the aggregation tendency of new low‐density polyethylene MPs due to enhanced steric hindrance and electrostatic repulsion. However, variations of pH and utilizing synthetic stormwater versus ultrapure water did not alter the aggregation kinetics of new MPs. The aggregation behavior of photodegraded MPs was significantly different from new MPs. A greater tendency for aggregation of photodegraded MPs was found in the stormwater compared to the ultrapure water. This study contributes to a better understanding of the transport and fate of MPs within the aqueous environment and their subsequent environmental risks.

Carbon Dioxide Toxicity to Zebra Mussels (Dreissena polymorpha) is Dependent on Water Chemistry.

Carbon dioxide (CO2) is gaining interest as a tool to combat aquatic invasive species, including zebra mussels (Dreissena polymorpha). However, the effects of water chemistry on CO2 efficacy are not well described. We conducted five trials in which we exposed adult zebra mussels to a range of CO2 in water with adjusted total hardness and specific conductance. We compared dose-responses and found differences in lethal concentration to 50% of organisms (LC50) estimates ranging from 108.3 to 179.3 mg/L CO2 and lethal concentration to 90% of organisms (LC90) estimates ranging from 163.7 to 216.6 mg/L CO2. We modeled LC50 and LC90 estimates with measured water chemistry variables from the trials. We found sodium (Na+) concentration to have the strongest correlation to changes in the LC50 and specific conductance to have the strongest correlation to changes in the LC90. Our results identify water chemistry as an important factor in considering efficacious CO2 concentrations for zebra mussel control. Additional research into the physiological responses of zebra mussels exposed to CO2 may be warranted to further explain mode of action and reported selectivity. Further study could likely develop a robust and relevant model to refine CO2 applications for a wider range of water chemistries. Environ Toxicol Chem 2024;43:1312-1319. Published 2024. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Water and sediment chemistry drivers of chlorophyll-a dynamics within a Ramsar declared floodplain pan wetland system.

Floodplain pans are hydrologically dynamic in nature and characterised by variables such as chlorophyll-a (chl-a), water, and sediment chemistry over their hydroperiods. The present study investigated the spatio-temporal variations in water and sediment physico-chemical, and chlorophyll-a concentration characteristics of six floodplain pans found in the Ramsar declared Makuleke wetlands, Kruger National Park, South Africa. The water and sediment physico-chemical variable values were generally elevated during the high-water period, whereas chlorophyll-a concentrations varied across pans and hydroperiod. Benthic chl-a concentration significantly varied across pans with concentrations ranging from 161 to 1036.2mg m2. The two-way ANOVA showed significant differences in benthic chl-a concentration among hydroperiods, and no significant differences were observed in pelagic chl-a across pans and hydroperiods. Generally, pelagic and benthic chl-a concentration increased as water and sediment chemistry variables increased. Furthermore, three sediment variables, i.e. pH, calcium, and magnesium, and water conductivity were found to be significant in structuring benthic chlorophyll-a dynamics in pans. However, none of the sediment and water variables had a significant effect on pelagic chl-a. Hydroperiod had a significant effect on influencing chl-a concentration, with high and low water level periods being characterised by low and high chl-a concentration, respectively. The n-MDS results showed strong overlaps in chl-a biomass among the Makuleke floodplain pans across hydroperiods. The increasing chl-a concentration in these floodplain pans due to potential bioturbation effects as a result of large mammals could potentially lead to eutrophication, which in turn could affect the system's primary productivity and aquatic biota. Therefore, it is important to establish a continuous monitoring programme on these pans to inform sound management decisions.

Assessing the Influence of Agricultural Nonpoint Source Pollution on Water Quality in Central Kentucky’s Headwater Streams

This study addresses the pressing issue of nonpoint source water pollution in Kentucky, particularly associated with large-scale agriculture. Centered on the outer bluegrass region of Central Kentucky, the research examines the water quality of headwater streams during the agricultural season. The approach involves geospatial land cover classification using aerial imagery. Water quality data were collected during the agricultural growing season from May to October 2018. Land cover classification utilized ERDAS Imagine 2016 and ESRI ArcGIS 10.6 GIS software, while conventional water quality parameters were measured with a YSI ProDSS® multiparameter water probe and a Marsh-McBirney Flo-Mate 2000 flow meter. Statistical analyses show significant differences in stream water chemistry, suggesting the impact of agricultural nonpoint source pollution. Forested streams exhibited more varied conditions, indicating a potentially better environment. As agricultural land percentage increased, water chemistry variation suggested a measurable threshold for changes. Significant differences in water quality between agricultural and forested streams highlight the potential benefits of expanding riparian zones beyond regulations. Enlarging these zones is proposed as a strategy to mitigate nonpoint source pollution in Kentucky’s waterways.

Temporal variability of water chemistry in the Cherkashinskaya well No. 36-RG (Tobolsk district, Tyumen region)

This article focuses on a temporary change in the chemical composition of water in the Cherkashinskaya well No. 36-RG, which is located in the Tobolsk district near the village of Shestakovo. The impact of underground mineral waters on catchments and watercourses can be caused by the open gushing of orphaned geological exploration wells. This can lead to the disturbance of the hydrochemical regime of neighbouring water systems. Publications on this topic are available not only in Tyumen region, but also throughout the Russian Federation. For example, scientific articles and conference proceedings, such as "Groundwater of the East of Russia" (2018), "Issues of studying surface and groundwater of Siberia" (2021), and the International Conference "Underground Waters 2023", are available. The study highlights the behavior of various components of water composition. The article presents changes in the mineralization of groundwater and identifies the main sources of negative impact on its quality. In 2019, the chemical composition of the water in the containing well underwent a transformation. This article focuses on the changes in the chemical composition of water from the Cherkashinskaya well No. 36-RG and its impact on the surrounding areas.

Long‐term changes in stream water chemistry in small forested watersheds in the northern Kanto region

AbstractConcerns have been raised regarding the degradation of stream water quality due to the excessive influx of atmospheric deposition. This study aimed to reveal the long‐term variation in stream water chemistry in approximately 40 forested small watersheds in the northern Kanto region, based on 3 surveys conducted in 1991–1992, 2006–2007, and 2022. The factors influencing each dissolved element were investigated. Regarding long‐term variations in stream water chemistry, relatively stable concentrations of cations (Ca2+, Mg2+, K+, and Na+) and SiO2 were observed. However, the concentrations of anions (Cl−, , and ) decreased due to the improvement in the atmospheric environment and the diminishing effect of fertilization. Furthermore, the recent increase in stream water pH was attributed to an increase in bicarbonate (), compensating for the decrease in anion concentrations relative to cations. Geology was the most significant factor for inter‐watershed variations in cations and SiO2, and this influence remained relatively constant over 30 years. Forest practices, especially fertilization, had a significant effect on Cl− and , and contributed to higher concentrations in the fertilized watersheds than in the non‐fertilized watersheds over the 15 years following fertilization. Sulfate deposition was a significant influencing factor for , and the concentration fluctuated under long‐term variations in deposition over the past 30 years. Despite substantial acid deposition in the study area, the absence of stream water acidification could be attributed to the abundant cation supply from bedrock and volcanic ash, which underwent weathering processes.

A survey of water chemistry used in zebrafish facilities and their effects on early zebrafish development

Background There are a variety of published standard methods and water chemistry recommendations for zebrafish (Danio rerio) husbandry, but empirical evidence for their justification is often lacking, as is information on some variables that have important biological effects on fish. Importantly, these different recommendations could contribute to variability in results and fish welfare between or within institutions. Methods Here we document the current range of water chemistry used by various research institutions around the world and report initial findings on their effects on the development and growth of zebrafish. Over 40 institutes responded to a survey that revealed a large variation in water chemistry used for zebrafish husbandry including differences in the set-points and acceptable ranges for temperature, pH and conductivity. In subsequent experiments, zebrafish (D. rerio, WIK) embryos/larvae exposed to a large range of salt concentrations (50μM to 10mM Na+ or 30 – 2500 μS/cm) and CO2 levels (400 – 8,000 μatm). Results Larvae exposed to the lowest salt concentration (5 μM Na+ or &lt; 30μS/cm) had a slower response to touch and their swim bladders were not inflated. Larvae exposed to 5-100 μM Na+ were 5 % shorter in total body length than those exposed to higher salt concentrations (&gt;100 μM Na+). Zebrafish embryo/larvae exposed to intermediate pCO2 values (~2000 μatm) were 1 to 3.5% longer than those exposed to either ambient (400 μatm) or higher (4000 μatm) pCO2, but pCO2 did not affect developmental endpoints up to 4 dpf. Conclusions Overall, we highlight the magnitude of variation in water chemistry used within zebrafish research and provide some empirical evidence to show that not all of these water conditions might be optimal for developing zebrafish and reproducibility of research, although further research is necessary to determine longer-term effects of water chemistry on older larvae, juveniles and adults.

Macroinvertebrate Community in a Mediterranean Mountain River: Relationship with Environmental Factors Measured at Different Spatial and Temporal Scales

The macroinvertebrate community, physical–chemical water variables and hydromorphological indices were studied in the Turón River (Málaga, Southern Spain). Our study aims to improve the knowledge of the most influential environmental factors at different spatial and temporal scales in Mediterranean rivers, in order to establish better management of Mediterranean river ecosystems. To this end, in this work, seasonal sampling was carried out for one year to evaluate the effect of the characteristics of the drainage basin (i.e., geology, topography, land use) on the macroinvertebrate community. To this end, the environmental variables of the catchment basins were evaluated at three different scales: (i) watershed level, (ii) valley segment level and (iii) local level. The results showed that 13 environmental variables, 3 at the watershed scale, 5 at the valley segment scale and 5 at the local scale, influenced the macroinvertebrate community. Land use is the main explanatory variable at the watershed scale, while stream channel curvature is the most common variable at the valley segment scale, and the habitat assessment index is the variable with the strongest influence at the local scale. The influence of different spatial scales presented a seasonal variation. During spring, autumn and winter, the watershed scale exhibited the highest resolution (adjusted R2 = 0.20–0.29), while in summer, the local scale became the most significant in explaining the presence of macroinvertebrate taxa (adjusted R2 = 0.17). The obtained results emphasize the significance of temporal and spatial scales in Mediterranean rivers for adequate river ecosystem management.

Impact of Variable Water Chemistry on PFOS-Goethite Interactions: Experimental Evidence and Surface Complexation Modeling.

Perfluorooctanesulfonate (PFOS) has become a major concern due to its widespread occurrence in the environment and severe toxic effects. In this study, we investigate PFOS sorption on goethite surfaces under different water chemistry conditions to understand the impact of variable groundwater chemistry. Our investigation is based on multiple lines of evidence, including (i) a series of sorption experiments with varying pH, ionic strength, and PFOS initial concentration, (ii) IR spectroscopy analysis, and (iii) surface complexation modeling. PFOS was found to bind to goethite through a strong hydrogen-bonded (HB) complex and a weaker outer-sphere complex involving Na+ coadsorption (OS-Na+). The pH and ionic strength of the solution had a nontrivial impact on the speciation and coexistence of these surface complexes. Acidic conditions and low ionic strength promoted hydrogen bonding between the sulfonate headgroup and protonated hydroxo surface sites. Higher electrolyte concentrations and pH values hindered the formation of strong hydrogen bonds upon the formation of a ternary PFOS-Na+-goethite outer-sphere complex. The findings of this study illuminate the key control of variable solution chemistry on PFOS adsorption to mineral surfaces and the importance to develop surface complexation models integrating mechanistic insights for the accurate prediction of PFOS mobility and environmental fate.

Effects of climate and acidic deposition on interannual variations of stream water chemistry in forested watersheds in the Shimanto River Basin, southern Japan

AbstractAlthough the amount of acidic deposition has recently decreased in Japan, it has still deteriorated some forest ecosystems during the past several decades. Moreover, recent climate changes can affect stream water chemistry. We investigated the temporal trend and effects of climate conditions on stream water chemistry for more than 20 years in two areas (Yusuhara and Taisho) in the Shmanto River Basin, southern Japan, where the effects of acidic deposition are considered to be modest. Stream water samples were collected monthly from three forest watersheds selected at each site. The annual means of the stream chemistry were predicted by multiple regression analysis. The ammonium, nitrate, and sulfate concentrations in the bulk precipitation have decreased at Yusuhara, and the sodium, magnesium, calcium, chloride, nitrate, and sulfate concentrations in the stream water have decreased in both areas. The nitrate and sulfate concentrations apparently responded to the decreasing input of acidic deposition. The sunlight hours were positively related with the potassium, magnesium, calcium, nitrate, sulfate, and bicarbonate concentrations in stream water. The results suggest that long sunlight hours boost the photosynthetic activities, thus promoting soil respiration and decomposition of soil organic matter. Moreover, a higher carbonic acid concentration in the soil solution promotes cation weathering and carbonic acid dissociation to bicarbonate. Given the decreasing trends in magnesium and calcium concentration with no change in bicarbonate concentration, we inferred that previousinputs of acidic deposition enhanced the rate of rock weathering.

Effects of chloride on corrosion scale compositions and heavy metal release in drinking water distribution systems

Variations in water chemistry may lead to the release of harmful heavy metals in drinking water distribution systems (DWDSs). In this study, the effects of chloride on the release of heavy metals such as Fe, Mn, As, Cr, Mo, V, Sr, and Co were examined using steel and cast iron pipe loops. After chloride was added, the relative contents of goethite (α-FeOOH), lepidocrocite (γ-FeOOH), and siderite (FeCO3) in pipe scales increased, but the contents of magnetite (Fe3O4) decreased. The most prevalent compounds were α-FeOOH and γ-FeOOH. When the chloride levels were increased, the effluent concentrations of Fe, Mn, As, Cr, Mo, V, Sr, and Co significantly increased. These heavy metals were released presumably because of the destabilization and dissolution of corrosion scales induced by chloride and adsorption site competition. Strong positive correlations were also observed between Fe&Mn, Fe/Mn&As, Fe/Mn&Cr, Fe/Mn&Mo, Fe/Mn&V, Fe/Mn&Sr, and Fe/Mn&Co, indicating the co-release of Fe, Mn, and other metals. This study may be helpful for the potential strategies on avoidance of heavy metal release and improvement of water supply security.

Poluição em riachos em um município de turismo de luxo na Serra da Mantiqueira (Sudeste do Brasil)

Abstract Aim Our aim was to analyze the limnological characteristics of streams located in a luxury tourism municipality in the Serra da Mantiqueira (Southeast Brazil). Methods We analyzed water physical and chemical variables of six sampling sites located in three streams of the Sapucaí-Guaçú River Basin along the urban area of the municipality of Campos do Jordão and one sampling site in the Rio da Prata stream, as a reference location not impacted by urban pollution (São Paulo, Brazil). We measured some physical and chemical variables of the water and analyzed the concentration of nutrients (forms of N and P) in the streams close to the basin's sources (Sites 1, 2 and 3), within and downstream of the urban area (sites 4 and 5), downstream of the municipality's Wastewater Treatment Plant (WWTP) (Site 6) and the reference location (Site 7). To find out whether there were differences in limnological variables among the sampling sites we used the Analysis of Variance (ANOVA). To order the sampling sites according to the variation in their limnological characteristics we applied a Principal Component Analysis (PCA). Results Our results showed that sites 1, 2 and 3, although close to the sources, presented limnological changes in relation to the reference location (Site 7) due to urban occupations in their surroundings. The sampling sites 4 and 6 are the most polluted due to urbanization and the discharge of effluents from the WWTP, respectively. The stretch between these two locations (Site 5) proved to be less polluted due to the autodepuration process. Conclusions We concluded that the streams in the Sapucaí-Guaçú River Basin are polluted, although at different levels. The urban area of Campos do Jordão causes pollution of the streams in its surroundings due to surface runoff and the discharge of untreated sewage due to the lack of access to sewage services for a large part of the population. The absence of tertiary treatment at the WWTP leads to pollution of the stream after the release of its effluent.