Sulphate-based electrochemical processes as an alternative for the remediation of a beauty salon effluent‡.

Beauty salons (BS) are places that deal with a wide range of cosmetics with potentially hazardous chemicals, and their effluent should be properly treated before going to the sewage system, once it represents characteristics of industrial wastewater. This work provides an extensive characterization of a BS effluent and its respective electrochemical treatment by comparing NaCl, Na2SO4, and Na2S2O8 as supporting electrolytes with a boron-doped diamond (BDD) as anode, applying 10 or 30 mA cm-2 of current density (j). The inclusion of UVC irradiation was also performed but the improvements achieved in removing the organic matter were null or lower. The analysis of chemical oxygen demand (COD) removal, energy consumption, and total current efficiency (TCE) was required to prove the efficacy of the processes and the comparative study of the performance of different technologies. Precipitate analysis was also done due to the high turbidity of the raw effluent and the appearance of a precipitate before and during the electrolysis, mainly with Na2S2O8. The precipitate confirmed the presence of silicates and small amounts of heavy metals. The results clearly showed that 6 h of treatment with Na2SO4 achieved 58% of COD removal with an energy consumption of about 0.52 kWh m-3, being the best electrolyte option for treating BS effluent by applying 10 mA cm-2. Under these experimental conditions, the final wastewater can be directly discharged into the sewage system with a lower amount of visible precipitate, and with 73% less turbidity. The treatment here proposed can be used as an alternative to decision-makers and governments once it can be a step further in the implementation of better and advanced politics of water sanitation.

Marine Submicron Aerosols from the Gulf of Mexico: Polluted and Acidic with Rapid Production of Sulfate and Organosulfates.

We measured submicron aerosols (PM1) at a beachfront site in Texas in Spring 2021 to characterize the "background" aerosol chemical composition advecting into Texas and the factors controlling this composition. Observations show that marine "background" aerosols from the Gulf of Mexico were highly processed and acidic; sulfate was the most abundant component (on average 57% of total PM1 mass), followed by organic material (26%). These chemical characteristics are similar to those observed at other marine locations globally. However, Gulf "background" aerosols were much more polluted; the average non-refractory (NR-) PM1 mass concentration was 3-70 times higher than that observed in other clean marine atmospheres. Anthropogenic shipping emissions over the Gulf of Mexico explain 78.3% of the total measured "background" sulfate in the Gulf air. We frequently observed haze pollution in the air mass from the Gulf, with significantly elevated concentrations of sulfate, organosulfates, and secondary organic aerosol associated with sulfuric acid. Analysis suggests that aqueous oxidation of shipping emissions over the Gulf of Mexico by peroxides in the particles might potentially be an important pathway for the rapid production of acidic sulfate and organosulfates during the haze episodes under acidic conditions.

Groundwater quality and vulnerability in farms from agricultural-dairy basin of the Argentine Pampas.

Agricultural and livestock activities strongly influence groundwater quality and conditioning its use as water supply in rural areas. The aim was to determine the quality and suitability of the groundwater supply used in dairy farms of an agricultural area of Pampa plain of Córdoba (Argentina). Piper's diagram showed that the groundwater types were sodium bicarbonate, sodium bicarbonate-chloride, sodium chloride-sulfate, and sodium sulfate. Physicochemical parameters revealed that cations and anions showed a high and significant correlation in water samples, indicating a strong water-rock interaction. Nitrate (NO3-) content was significantly correlated with pH, water well depth, and distance from contamination sources. A high positive correlation between arsenic (As) and bicarbonate, sulfate, sodium, and chloride (p < 0.05) indicates a similar origin. Among the pesticides monitored, 2,4-D was detected in 25% of groundwater samples (0.4 to 0.8 µg/L) coinciding with the ordinary application practices. In general, most of the groundwater samples did not comply with national and international regulations for drinking water and dairy hygiene, due to the high content of As, NO3-, bacteria, and the presence of 2,4-D herbicide. However, the quality of water was suitable for livestock drink. The data obtained in this study contribute to a better understanding of the contamination processes taking place and improve the agricultural and livestock management for an efficient use of this resource by dairy farmers.

Basic oxygen furnace sludge to treat industrial arsenic- and sulfate-rich acid mine drainage.

In this study, four systems (S1, S2, S3, and S4) were evaluated to determine whether basic oxygen furnace sludge (BOFS), mainly composed of Fe (84%, mostly as elemental Fe and FeO), Ca (3%, as CaCO3), and Si (1%), is capable of removing As-spiked, Mn, Mg, and sulfate from an industrial acid mine drainage (AMDi) collected in a gold mine in Minas Gerais, Brazil. In the S1 system (BOFS/deionized water pH 2.5), the stability of the residue was evaluated for 408 h under agitation. The results showed that only Ca and Mg were solubilized, and the pH increased from 2.5 up to 11.4 within the initial 24 h and kept still until the end of the experiment (408 h). The S2 system (BOFS/AMDi) achieved 100% removal of As and Mn, and 70% removal of sulfate after 648 h. In the first 30 min, the pH increased from 2.5 to 10, which was maintained until the end of the experiment. The removal of As, Mn, and sulfate in the presence of hydrogen peroxide (S3 and S4 systems - BOFS/AMDi/H2O2) was similar to that in the S2 system, which contained only BOFS. The formation of iron oxides was not accelerated by H2O2. As regards the removal of arsenic and sulfate species, the formation of incipient calcium arsenate and calcium sulfate dehydrated was indicated by X-ray diffraction analysis and PHREEQC modeling. Dissolved manganese and magnesium precipitated as oxides, according to the geochemical modeling. After contact with AMDi, the raw BOFS, initially classified as hazardous waste, became a non-inert waste, which implies simplified, less costly disposal. Except for sulfate, the concentrations of all the other elements were below the maximum permitted levels.

Relative bioavailability of manganese in relation to proteinate and sulfate sources for broiler chickens from one to 20 d of age.

The objective of this study was to evaluate the relative bioavailability (RB) of manganese (Mn) proteinate compared to Mn sulfate for broilers fed a diet based on corn and soybean meal for 20 d. The diets of 1,350 male Cobb broilers were supplemented with 0, 35, 70, 105, or 140 mg of Mn/kg of feed in the form of Mn sulfate or Mn proteinate. Weight gain, feed intake, feed conversion, bone strength, and Mn concentration in the tibia and liver, as well as the concentration of type I collagen in the tibia, were evaluated. No differences were observed for performance variables (P > 0.05) or for type I collage concentration in broiler tibia (P > 0.05), regardless of the source and level of supplementation used. Relative bioavailability was determined using bone strength values and Mn concentration in the tibia and liver, assuming Mn sulfate as the standard source (100%) by the slope-ratio method. The RB of Mn proteinate based on bone strength was 111%, based on liver Mn concentration was 128%, and based on tibia Mn concentration was 105%. Manganese proteinate was more bioavailable than Mn sulfate; it can be an important source of supplementation to improve bone quality in broilers.

Sulfate and metals removal from acid mine drainage in a horizontal anaerobic immobilized biomass (HAIB) reactor.

The acid mine drainage (AMD) can causes negative impacts to the environment. Physico-chemical methods to treat AMD can have high operational costs. Through passive biological methods, such as anaerobic reactors, sulfate reduction, and recovery of metals are promoted. This study evaluated the performance of a horizontal anaerobic immobilized biomass (HAIB) reactor for the treatment of synthetic AMD using polyurethane foam as support material, and anaerobic sludge as inoculum. Ethanol was used as an electron donor for sulfate reduction, resulting in an influent chemical oxygen demand (COD) in the range of 500-1,500 mg/L and COD/sulfate ratio at 1. A gradual increase of sulfate and COD concentration was applied that resulted in COD removal efficiencies higher than 78%, and sulfate removal efficiencies of 80%. Higher sulfate and COD concentrations associated with higher hydraulic retention times (36 h) proved to be a better strategy for sulfate removal. The HAIB reactor was able to accommodate an increase in the SLR up to 2.25 g SO42-/L d-1 which achieved the greatest performance on the entire process. Moreover, the reactor proved a suitable alternative for reaching high levels of metal removal (86.95 for Zn, 98.79% for Fe, and 99.59% for Cu).

Evaluating the effects of vanadyl sulfate on biomarkers of oxidative stress and inflammation in renal tissue of rats with diabetes type 2

Vanadyl sulfate (VS) is an ingredient in some food supplements and experimental drugs. This study was designed to assay the effects of VS on biomarkers of oxidative stress and inflammation in renal tissue of rats with diabetes type 2. 30 male Wistar rats were divided into three equal groups as follow: non-diabetics, non-treated diabetics and VS-treated diabetics. Diabetes type 2 has been induced through high fat diet and fructose in the animals. Diabetic rats were treated with 25 mg/kgBW of VS in water for 12 weeks. At the end of study, glucose and insulin were measured using commercially available kits in serum and biomarkers of oxidative stress and inflammation in renal homogenates of animals were measured by related methods. Compared to controls, glucose and insulin were increased significantly in non-treated diabetic rats (p-value <0.05) that showed the induction of diabetes type 2 in rats. The results showed that in VS-treated diabetic rats compared to the non-treated diabetic group, vanadyl sulfate significantly reduced the glucose and insulin secretion and changed renal inflammatory and oxidative markers, except protein carbonyl so that we couldn't find any significant changes. Our study showed that vanadyl supplementation had positive effects on oxidative stress and inflammation biomarkers in kidney of diabetic rats

Enhanced anaerobic performance and SMD process in treatment of sulfate and organic S-rich TMBA manufacturing wastewater by micro-electric field-zero valent iron-UASB.

This study focused on investigating reactor performance, simultaneous methanogeneis and denitrifiction (SMD) process for treatment of a sulfate plus organic sulfur - rich 3,4,5-Triethoxybenzaldehyde (TMBA) manufacturing wastewater with variable COD/TSO42- (total sulfate) ratio by micro-electric field- zero-valent-iron (ZVI) UASB for 390 days. The initial COD/TSO42- was set as 1.42, 0.9 and 0.5, respectively by manually introducing sulfate. The experimental results indicated that micro-electric field- zero-valent-iron UASB was an attractive integrated option for satisfactory COD removal, nitrate reduction and a reasonable methane yield rate even at COD/TSO42- as low as 0.9. Further declining the COD/TSO42- to 0.5 can result in a moderate inhibition of SMD process. The behavior of organic S release was not inhibited over the entire experimental period. Thus, surprisingly, sulfate concentration in the effluent was always higher than that in the influent. In comparison with sludge sample at Day-1, sludge at Day-390 was characterized with high abundant Tissierella Soehngenia, Anaerolinaceae and Brevundimonas diminuta, which played critical role in promising performance in COD abatement. The relatively low abundance of sulfate reducing bacteria (SRB) such as Desulfobulbus and Desulfomicrobium can explain the lower sulfate reduction efficiency in term of high concentration of sulfate plus released from organic S-rich compounds.

Assessment of water quality from the Blue Lagoon of El Cobre mine in Santiago de Cuba: a preliminary study for water reuse.

The creation of pit lakes is usually an acceptable solution from the landscaping point of view for voids left by discontinued open-pit mines. However, without rehabilitation, these voids represent a potential environmental risk. The aim of the present work was to assess, for the first time, the water quality, i.e., physicochemical characteristics, metal and metalloid (MM) content, and ecotoxicity of the waters of the El Cobre Blue Lagoon, a pit lake formed in an open-pit copper mine in Cuba. Potential effects of rainy season vs. dry season and spatial location (different depths) on water characteristics were considered. Results revealed that water contained was moderately acidic (pH = 4.6 ± 0.2), with high electrical conductivity (EC = 3.02 ± 0.03 mS cm-1), whatever the season. Dissolved oxygen (DO = 9.9 ± 2.0 mg L-1), total dissolved solid (TDS = 7003 ± 245 mg L-1), and sulfate concentration (6556 ± 1410 mg L-1) in the El Cobre Blue Lagoon water were above acceptable limits for sources of surface water as recommended by Cuban standard (NC 1021:2014). High copper (43.6 ± 1.7 mg L-1) and manganese (24.1 ± 1.1 mg L-1) contents were detected. Except for EC, sulfates, chlorides, TDS, nitrates, and phosphates, other physicochemical parameters were stable between dry and rainy seasons (p < 0.05). El Cobre Blue Lagoon waters showed an ecotoxicological impact on Vibrio fischeri. No significant differences were detected between all sampling points in the lake for each parameter monitored for a given time. These first results show the spatial homogeneity but poor quality of waters from El Cobre Blue Lagoon. Remediation processes need to be implemented in order to lessen the human and environmental health risk and favor potential water reuse. We suggest the use of constructed wetlands for water treatment. This preliminary research work can serve to alert Cuban local public authorities to the need to rehabilitate such sites.

Organosulfates in aerosols downwind of an urban region in central Amazon.

Organosulfates are formed in the atmosphere from reactions between reactive organic compounds (such as oxidation products of isoprene) and acidic sulfate aerosol. Here we investigated speciated organosulfates in an area typically downwind of the city of Manaus situated in the Amazon forest in Brazil during "GoAmazon2014/5" in both the wet season (February-March) and dry season (August-October). We observe products consistent with the reaction of isoprene photooxidation products and sulfate aerosols, leading to formation of several types of isoprene-derived organosulfates, which contribute 3% up to 42% of total sulfate aerosol measured by aerosol mass spectrometry. During the wet season the average contribution of summed organic sulfate concentrations to total sulfate was 19 ± 10% and similarly during the dry season the contribution was 19 ± 8%. This is the highest fraction of speciated organic sulfate to total sulfate observed at any reported site. Organosulfates appeared to be dominantly formed from isoprene epoxydiols (IEPOX), averaging 104 ± 73 ng m-3 (range 15-328 ng m-3) during the wet season, with much higher abundance 610 ± 400 ng m-3 (range 86-1962 ng m-3) during the dry season. The concentration of isoprene-derived organic sulfate correlated with total inorganic sulfate (R2 = 0.35 and 0.51 during the wet and dry seasons, respectively), implying the significant influence of inorganic sulfate aerosol for the heterogeneous reactive uptake of IEPOX. Organosulfates also contributed to organic matter in aerosols (3.5 ± 1.9% during the wet season and 5.1 ± 2.5% during the dry season). The present study shows that an important fraction of sulfate in aerosols in the Amazon downwind of Manaus consists of multifunctional organic chemicals formed in the atmosphere, and that increased SO2 emissions would substantially increase SOA formation from isoprene.

Long term metal release and acid generation in abandoned mine wastes containing metal-sulphides.

The sulphide-rich mine wastes accumulated in tailing dumps of La Concordia Mine (Puna of Argentina) have been exposed to the weathering action for more than 30 years. Since then, a series of redox reactions have triggered the generation of a highly acidic drainage -rich in dissolved metals-that drains into the La Concordia creek. The extent of metal and acid release in the site was analysed through field surveys and laboratory experiments. Static tests were conducted in order to predict the potential of the sulphidic wastes to produce acid, while Cu-, Zn-, Fe- and Pb-bearing phases present in the wastes were identified by XRD, SEM/EDS analysis and sequential extraction procedures. Finally, the release of these metals during sediment-water interaction was assessed in batch experiments carried out in a period of nearly two years. Field surveys indicate that the prolonged alteration of the mine wastes led to elevated electrical conductivity, pH values lower than 4 and metal concentrations that exceed the guide values for drinking water in the La Concordia stream regardless of the dominating hydrological conditions. The highly soluble Fe and Mg (hydrous)sulphates that form salt crusts on the tailings surfaces and the riverbed sediments play an important role in the control of metal mobility, as they rapidly dissolve in contact with water releasing Fe, but also Cu and Zn which are scavenged by such minerals. Another important proportion of the analysed metals is adsorbed onto Fe (hydr)oxides or form less soluble hydroxysulfates. Metals present in these phases are released to water more slowly, thus representing a potential long term source of heavy metal pollution. The obtained results are a contribution to the understanding of long term metal transformations and mobility in mine waste-impacted sites.

Natural and anthropic processes controlling groundwater hydrogeochemistry in a tourist destination in northeastern Brazil.

The objective of this study was to analyze spatial-seasonal changes to identify the natural and anthropic processes that control groundwater hydrogeochemistry in urban aquifers in municipality of Lençóis (Bahia). Tourism is the main activity of this municipality, which is an important tourist destination in northeastern Brazil and which maintains its tourism infrastructure by using groundwater. Two field campaigns were conducted (dry and rainy seasons) in order to collect groundwater samples extracted from 15 tubular wells distributed over the urban area of the municipality. The Piper diagram, multivariate statistical analyses, and artificial neural networks indicated that there are two types of water (Na-Cl and Na-[Formula: see text]-), which were divided into five different clusters. Seasonal variation was observed to significantly alter groundwater hydrogeochemistry. According to the Gibbs diagram, groundwater within the urban area of Lençóis belonged to the rainfall dominance, demonstrating low water-rock interaction. Hydrogeochemical modeling results suggested hydrolysis as the main natural factors controlling process. However, mineral dissolution also occurred in one of the clusters. Human-originated trace contamination by nitrate, chloride, and sulfate occurred in a zone of the urban area. This contamination was observed regardless of climate seasonality, indicating that the main controlling process for groundwater hydrochemistry in this region is wastewater mobilization (indirect artificial recharge).

Chemical composition of rainwater in the Sinos River Basin, Southern Brazil: a source apportionment study.

This study aimed to assess the chemical composition of the rainwater in three areas of different environmental impact gradients in Southern Brazil using the receptor model EPA Positive Matrix Factorization (EPA PMF 5.0). The samples were collected in a bulk sampler, from October 2012 to August 2014, in three sampling sites along with the Sinos River Basin: Caraá, Taquara, and Campo Bom. The major ions NH4+, Na+, K+, Ca2+, Mg2+, F-, Cl-, NO3-, SO42-, and pH were analyzed, as well as identify the main emission sources. The most abundant cations and anions were Ca2+, Na+, Cl-, and SO42-, respectively. The mean pH value in the Sinos River Basin during the study period was 6.07 ± 0.49 (5.13-7.05), which suggests inputs of alkaline species into the atmosphere. The most important neutralizing agents of sulfuric and nitric acids in the Sinos River Basin are Ca2+ (NF = 1.36) and NH4+ (NF = 0.57). The source apportionment provided by the EPA PMF 5.0 resulted in four factors, which demonstrate the influence of anthropogenic and natural sources, in the form of (a) industry/combustion of fossil fuels (F- and SO42-), (b) marine contribution (Na+ and Cl-), (c) crustal contribution (K+, Ca2+, and NO3-), and (d) agriculture/livestock (NH4+). Therefore, this study allows a more appropriate understanding of factors that contribute to rainwater chemical composition and also to possible changes in air quality.

Hydrochemical and environmental isotope analysis of groundwater and surface water in a dry mountain region in Northern Chile.

This case study examines the geological imprint and land use practices on water quality in the arid Huasco Valley against the backdrop of ongoing water conflicts surrounding competing demands for agriculture and mining. The study is based on a detailed analysis of spatial and temporal variations of monthly surface and bi-monthly groundwater quality samples measured during the Chilean summer of 2015/16. Additional information on source regions and river-groundwater interactions were collected using stable water isotopes. Regarding the geological impact on water quality, high concentrations of Ca2+, SO42- and HCO3- indicate a strong influence of magmatic rocks, which constitute this high mountain basin, on the hydrochemistry. Piper and Gibbs-diagrams revealed that all samples show a homogenous distribution dominated by rock-water interactions. Measured NO3- concentrations in surface water are generally low. However, groundwater aquifers exhibit higher concentrations. Mn is the only heavy metal with elevated concentrations in surface water, which are possibly related to mining activities. The results illustrate that both surface and groundwater can be classified as suitable for irrigation. In addition, groundwater has been found to be suitable as drinking water. High similarities in isotopic signatures indicate a strong connection between surface and groundwater. Isotopic analyses suggest a strong influence of evaporation. This combined approach of hydrogeochemical and isotopic analysis proved to be a helpful tool in characterizing the catchment and can serve as a basis for future sustainable water management.

A selective volatilization method for determination of chloride and sulfate in calcium carbonate pharmaceutical raw material and commercial tablets.

In this work a feasible method for chloride and sulfate determination in calcium carbonate pharmaceutical raw material and commercial tablets by ion chromatography after microwave-induced combustion was developed. The analytes were released from matrix by combustion in closed system pressurized with oxygen. Starch as volatilization aid, 100mmolL-1 HNO3 as absorbing solution and 5min of microwave irradiation time were used. Recovery tests using standard solutions were performed for the accuracy evaluation. A mixture of calcium carbonate pharmaceutical raw material or commercial tablets, starch and a certified reference material was also used as a type of recovery test. Recoveries ranging from 88% to 103% were obtained in both spike tests. Limits of detection (Cl-: 40µgg-1 and SO42-: 140µgg-1) were up to eighteen times lower than the maximum limits established for the analytes by Brazilian, British, European and Indian Pharmacopoeias. The limit tests recommended by the European Pharmacopoeia for Cl- and SO42- in CaCO3 were carried out to compare the results. Chloride and SO42- concentrations in the samples analyzed by proposed method were in agreement with those results obtained using the tests recommended by the European Pharmacopoeia. However, the proposed method presents several advantages for the routine analysis when compared to pharmacopoeial methods, such as the quantitative simultaneous determination, high sample preparation throughput (up to eight samples per run in less than 30min), reduced volume of reagents and waste generation. Thus, the proposed method is indicated as an excellent alternative for Cl- and SO42- determination in CaCO3 pharmaceutical raw material and commercial tablets.

Developing a Water Quality Index (WQI) for an Irrigation Dam.

Pollution levels have been increasing in water ecosystems worldwide. A water quality index (WQI) is an available tool to approximate the quality of water and facilitate the work of decision-makers by grouping and analyzing numerous parameters with a single numerical classification system. The objective of this study was to develop a WQI for a dam used for irrigation of about 5000 ha of agricultural land. The dam, La Vega, is located in Teuchitlan, Jalisco, Mexico. Seven sites were selected for water sampling and samples were collected in March, June, July, September, and December 2014 in an initial effort to develop a WQI for the dam. The WQI methodology, which was recommended by the Mexican National Water Commission (CNA), was used. The parameters employed to calculate the WQI were pH, electrical conductivity (EC), dissolved oxygen (DO), total dissolved solids (TDS), total hardness (TH), alkalinity (Alk), total phosphorous (TP), Cl-, NO3, SO4, Ca, Mg, K, B, As, Cu, and Zn. No significant differences in WQI values were found among the seven sampling sites along the dam. However, seasonal differences in WQI were noted. In March and June, water quality was categorized as poor. By July and September, water quality was classified as medium to good. Quality then decreased, and by December water quality was classified as medium to poor. In conclusion, water treatment must be applied before waters from La Vega dam reservoir can be used for irrigation or other purposes. It is recommended that the water quality at La Vega dam is continually monitored for several years in order to confirm the findings of this short-term study.

Wood burning pollution in southern Chile: PM2.5 source apportionment using CMB and molecular markers.

Temuco is a mid-size city representative of severe wood smoke pollution in southern Chile; i.e., ambient 24-h PM2.5 concentrations have exceeded 150 µg/m3 in the winter season and the top concentration reached 372 µg/m3 in 2010. Annual mean concentrations have decreased but are still above 30 µg/m3. For the very first time, a molecular marker source apportionment of ambient organic carbon (OC) and PM2.5 was conducted in Temuco. Primary resolved sources for PM2.5 were wood smoke (37.5%), coal combustion (4.4%), diesel vehicles (3.3%), dust (2.2%) and vegetative detritus (0.7%). Secondary inorganic PM2.5 (sulfates, nitrates and ammonium) contributed 4.8% and unresolved organic aerosols (generated from volatile emissions from incomplete wood combustion), including secondary organic aerosols, contributed 47.1%. Adding the contributions of unresolved organic aerosols to those from primary wood smoke implies that wood burning is responsible for 84.6% of the ambient PM2.5 in Temuco. This predominance of wood smoke is ultimately due to widespread poverty and a lack of efficient household heating methods. The government has been implementing emission abatement policies but achieving compliance with ambient air quality standards for PM2.5 in southern Chile remains a challenge.

Geochemical behavior of an acid drainage system: the case of the Amarillo River, Famatina (La Rioja, Argentina).

The Amarillo River (Famatina range, Argentina, ~29° S and ~67° W) is unusual because acid mine drainage (AMD) is superimposed on the previously existing acid rock drainage (ARD) scenario, as a Holocene paleolake sedimentary sequence shows. In a markedly oxidizing environment, its water is currently ferrous and of the sulfate-magnesium type with high electrical conductivity (>10 mS cm-1 in uppermost catchments). At the time of sampling, the interaction of the mineralized zone with the remnants of mining labors determined an increase in some elements (e.g., Cu ~3 to ~45 mg L-1; As ~0.2 to ~0.5 mg L-1). Dissolved concentrations were controlled by pH, decreasing significantly by precipitation of neoformed minerals (jarosite and schwertmannite) and subsequent metal sorption (~700 mg kg-1 As, 320 mg kg-1 Zn). Dilution also played a significant role (i.e., by the mixing with circumneutral waters which reduces the dissolved concentration and also enhances mineral precipitation). Downstream, most metals exhibited a significant attenuation (As 100 %, Fe 100 %, Zn 99 %). PHREEQC-calculated saturation indices (SI) indicated that Fe-bearing minerals, especially schwertmannite, were supersaturated throughout the basin. All positive SI increased through the input of circumneutral water. PHREEQC inverse geochemical models showed throughout the upper and middle basin, that about 1.5 mmol L-1 of Fe-bearing minerals were precipitated. The modeling exercise of mixing different waters yielded results with a >99 % of correlation between observed and modeled data.

Application of water quality index to evaluate groundwater quality (temporal and spatial variation) of an intensively exploited aquifer (Puebla valley, Mexico).

The spatial and temporal variation of water quality in the urban area of the Puebla Valley aquifer was evaluated using historical and present data obtained during this investigation. The current study assessed water quality based on the Water Quality Index developed by the Canadian Council of Ministers of the Environment (CCME-WQI), which provides a mathematical framework to evaluate the quality of water in combination with a set of conditions representing quality criteria, or limits. This index is flexible regarding the type and number of variables used by the evaluation given that the variables of interest are selected according to the characteristics and objectives of development, conservation and compliance with regulations. The CCME-WQI was calculated using several variables that assess the main use of the wells in the urban area that is public supply, according to criteria for human use and consumption established by Mexican law and international standards proposed by the World Health Organization. The assessment of the index shows a gradual deterioration in the quality of the aquifer over time, as the amount of wells with excellent quality have decreased and those with lower index values (poor quality) have increased throughout the urban area of the Puebla Valley aquifer. The parameters affecting groundwater quality are: total dissolved solids, sulfate, calcium, magnesium and total hardness.

Groundwater contamination in coastal urban areas: Anthropogenic pressure and natural attenuation processes. Example of Recife (PE State, NE Brazil).

In a context of increasing land use pressure (over-exploitation, surface-water contamination) and repeated droughts, identifying the processes affecting groundwater quality in coastal megacities of the tropical and arid countries will condition their long-term social and environmental sustainability. The present study focuses on the Brazilian Recife Metropolitan Region (RMR), which is a highly urbanized area (3,743,854 inhabitants in 2010) on the Atlantic coast located next to an estuarial zone and overlying a multi-layered sedimentary system featured by a variable sediment texture and organic content. It investigates the contamination and redox status patterns conditioning potential attenuation within the shallow aquifers that constitute the interface between the city and the strategic deeper semi-confined aquifers. These latter are increasingly exploited, leading to high drawdown in potenciometric levels of 20-30m and up to 70m in some high well density places, and potentially connected to the surface through leakage. From a multi-tracer approach (major ions, major gases, δ(11)B, δ(18)O-SO4, δ(34)S-SO4) carried out during two field campaigns in September 2012 and March 2013 (sampling of 19 wells and 3 surface waters), it has been possible to assess the contamination sources and the redox processes. The increasing trend for mineralization from inland to coastal and estuarial wells (from 119 to around 10,000µS/cm) is at first attributed to water-rock interactions combined with natural and human-induced potentiometric gradients. Secondly, along with this trend, one finds an environmental pressure gradient related to sewage and/or surface-channel network impacts (typically depleted δ(11)B within the range of 10-15‰) that are purveyors of chloride, nitrate, ammonium and sulfate. Nitrate, ammonium and sulfate (ranging from 0 to 1.70mmol/L, from 0 to 0,65mmol/L, from 0.03 to 3.91mmol/L respectively are also potentially produced or consumed through various redox processes (pyrite oxidation, denitrification, dissimilatory nitrate reduction to ammonium) within the system, as is apparent within a patchwork of biogeochemical reactors. Furthermore, intensive pumping in the coastal area with its high well density punctually leads to temporary well salinization ([Cl] reaching temporarily 79mmol/L). Our results, summarized as a conceptual scheme based on environmental conditions, is a suitable basis for implementing sustainable management in coastal sedimentary hydrosystems influenced by highly urbanized conditions.