An overview about the presence of arsenic (As) in groundwaters of Argentina, made by a transdisciplinary group of experts is presented. Aspects on As occurrence, effects of As on human health, regulations regarding the maximum allowable amount of As in drinking water as well as bottled water, and analytical techniques for As determination are presented. The most affected region in Argentina is the Chaco-Pampean plain, covering around 10 million km 2 , where approximately 88% of 86 groundwater samples collected in 2007 exceeded the World Health Organization (WHO) guideline value. In the Salí river basin, As concentrations ranged from 11.4 to 1660 μg/L, with 100% of the samples above the WHO guideline value. In the Argentine Altiplano (Puna) and Subandean valleys, 61% of 62 samples collected from surface and groundwaters exceeded the WHO limit. Thus, it can be estimated that, at present, the population at risk in Argentina reaches around four million people. Pathologies derived from the chronic consumption of As, the metabolism of As in the human body and the effects of the different As chemical forms, gathered under the name HACRE (hidroarsenicismo crónico regional endémico in Spanish, for chronic regional endemic hydroarsenicism) are described. Regarding the regulations, the 10 μg/L limit recommended by the WHO and the United States Environmental Protection Agency has been incorporated in the Argentine Food Code, but the application is still on hold. In addition, there is disparity regarding the maximal admitted values in several provinces. Considerations about the As concentrations in bottled water are also presented. A survey indicates that there are several Argentine laboratories with the suitable equipment for As determination at 10 μg/L, although 66% of them are concentrated in Buenos Aires City, and in the Santa Fe, Córdoba and Buenos Aires provinces. Conclusions and recommendations of this first part are provided.

An overview about the presence of arsenic (As) in groundwaters of Argentina, made by a transdisciplinary group of experts is presented. In this second part, the conventional and emerging technologies for As removal, management of wastes, and the initial investment costs of the proposed technologies, with emphasis on developments of local groups are described. Successful examples of real application of conventional and emerging technologies for As removal in waters for human consumption, for medium, small and rural and periurban communities are reported. In the country, the two most applied technologies for arsenic removal at a real scale are reverse osmosis and coagulation-adsorption-filtration processes using iron or aluminum salts or polyelectrolytes as coagulants. A decision tree to evaluate the possible technologies to be applied, based on the population size, the quality of the water and its intended use, is presented, including preliminary and indicative investment costs. Finally, a section discussing the treatment and final disposal of the liquid, semiliquid and solid wastes, generated by the application of the most used technologies, is included. Conclusions and recommendations, especially for isolated rural and periurban regions, have been added.

Nowadays, a spotlight on the direct manipulation of water from the geothermal fields is laid for manifold applications. This manuscript discusses the utilization of water produced from geothermal wells for irrigation and industrial purposes. In order to identify the suitability of the water for the above mentioned uses, various hydrochemical parameters were evaluated. Samples were collected from three geothermal well sites from Unai village, a prominent geothermal field situated in Navsari district, Gujarat, India. The hydrochemistry of the samples collected from hot spring (depth 30–45 m) was studied and samples were examined by calculating different parameters. The complete study was done individually for both industrial and irrigational uses of geothermal water. The mean surface temperature of the water is 55 °C and average pH of the sample studied is 8.12. The key Water Quality Indices (WQI) such as Langelier Saturation Index (LSI), Ryznar Stability Index (RSI), Puckorius Scaling Index (PSI) and Larson-Skold Index (LS) were examined for industrial utilization and the key indices like Sodium Absorption Ratio (SAR), Sodium Percentage (SP), Kelly Ratio (KR) Residual Sodium Carbonate (RSC) and Permeability Index (PI) were examined for irrigational utilization of geothermal water. LSI and RSI values show that carbonate and bicarbonate concentration is in the desirable range, however, LS (15.09, 13.54) is very high which indicates higher Cl- content. High value of indices such as SAR, KR, and SP points out the increased concentration of Na+ in the water sample. The results of this study would help the end users to identify the necessary water-treatments before utilizing the water for industrial and irrigation purposes in the study area.

In this work, we combined macroscopic measurements of precipitate aggregation and chemical composition (Mn/Fe solids ratio) with Fe and Mn K-edge X-ray absorption spectroscopy to investigate the solids formed by co-oxidation of Fe(II) and Mn(II) with O-2, MnO4, and HOCl in the presence of groundwater ions. In the absence of the strongly sorbing oxyanions, phosphate (P) and silicate (Si), and calcium (Ca), O-2 and HOCl produced suspensions that aggregated rapidly, whereas co-oxidation of Fe(II) and Mn(II) by MnO4 generated colloidally stable suspensions. The aggregation of all suspensions decreased in P and Si solutions, but Ca counteracted these oxyanion effects. The speciation of oxidized Fe and Mn in the absence of P and Si also depended on the oxidant, with O-2 producing Mn(III)-incorporated lepidocrocite (Mn/Fe = 0.01-0.02 mol/mol), HOCl producing Mn(III)-incorporated hydrous ferric oxide (HFO) (Mn/Fe = 0.08 mol/mol), and MnO4 producing poorly-ordered MnO2 and HFO (Mn/Fe > 0.5 mol/mol). In general, the presence of P and Si decreased the crystallinity of the Fe(III) phase and increased the Mn/Fe solids ratio, which was found by Mn K-edge XAS analysis to be due to an increase in surface-bound Mn(II). By contrast, Ca decreased the Mn/Fe solids ratio and decreased the fraction of Mn(II) associated with the solids, suggesting that Ca and Mn(II) compete for sorption sites. Based on these results, we discuss strategies to optimize the design (i.e. filter bed operation and chemical dosing) of water treatment plants that aim to remove Fe(II) and Mn(II) by co-oxidation.

High groundwater arsenic (As) across the globe has been one of the most well researched environmental concerns during the last two decades. Consequently, a large scientific knowledge-base has been developed on As distributions from local to global scales. However, differences in bulk sediment As concentrations cannot account for the As concentration variability in groundwater. Instead, in general, only aquifers in sedimentary basins adjacent to mountain chains (orogenic foreland basins) along continental convergent tectonic margins are found to be As enriched. We illustrate this association by integrating observations from long-term studies of two of the largest orogenic systems (i.e., As sources) and the aquifers in their associated foreland basins (As sinks), which are located in opposite hemispheres and experience distinct differences in climate and land-use patterns. The Andean orogenic system of South America (AB), an active continental margin, is in principle a modern analogue of the Himalayan orogenic system associated with the Indus-Ganges-Brahmaputra river systems in South Asia (HB). In general, the differences in hydrogeochemistry between AB and HB groundwaters are conspicuous. Major-solute composition of the arid, oxic AB groundwater exhibits a mixed-ion hydrochemical facies dominated by Na-Ca-Cl-SO4-HCO3. Molar calculations and thermodynamic modeling show that although groundwater of AB is influenced by cation exchange, its hydrochemical evolution is predominated by feldspar dissolution and relationships with secondary clays. In contrast, humid, strongly reducing groundwater of HB is dominated by Ca-HCO3 facies, suggestive of calcite dissolution, along with some weathering of silicates (monosiallitization). This work demonstrates that although hydrogeochemical evolutionary trends may vary with local climate and lithology, the fundamental similarities in global tectonic settings can still lead to the elevated concentrations of groundwater As.

The study aimed to investigate the most usable drinking water sources quality and the dependent population's exposure to potentially contaminated water. The specific area chosen for the study was the coastal area in Satkhira district's Tala Upazila. Six hundred and fourty nine most usable drinking water sources were selected, that included Deep Tubewell (DTW), Shallow Tubewell (STW) and Pond Sand Filter (PSF) for drinking water sampling. Following standard sampling procedures, in-situ measurements were taken for seven important water quality parameters: Arsenic-As, Iron-Fe, Electrical Conductivity-EC, Temperature-Temp, Total Coliform- TC, E-coli, and Fecal Coliform-FC. In addition, semi-structured questionnaire surveys were conducted at corresponding dependent households (HH). Weighted arithmetic water quality index (WQI) was used to calculate the suitability of the derived water for drinking purposes. In the tested water sources, As, Fe and EC range were found 0-500 mu g/L, 0-18 mg/L, and 165-8,715 mu S/cm, respectively. Of all the tested water sources, 74% exceeded the permissible limit for As, 83% for Fe and 99% for EC, according to WHO standards. Comparatively higher percentages of Point of Uses (PoU) were found to be more contaminated than Point of Sources (PoS), such as TC found in 38% PoS and 54% of corresponding PoU, E. coli found in 24% PoS and 35% of PoU and FC found in 45% PoS and 55% of PoU. WQI suggested that the majority (72%) of most usable drinking water sources were found to be unsuitable for drinking. Thus, 40% of the population (0.12 million) in the study area were directly consuming contaminated water. Dependent household members most frequently suffered from fever, diarrhea and high blood pressure, resulting in the average household spending USD 3-13 per month/HH for health-related expenditures, which is higher than national average. To acquire safe drinking water, the majority (58%) of the dependent HH expressed willingness to pay USD 1 per month/ HH which is costly for them. The situation can be improved by installing a deep tube well for safe drinking water, periodically testing the water quality, educating the public for better hygiene practices, and providing entrepreneurial incentives to help deliver safe water to the public at lower cost.

Legal framework is very crucial to protect the vital resources, to provide rights to public and administration, to support national policy and to bring technological intervention to ensure equitable distribution, fair management, and effective decision making. In Bangladesh, groundwater is not directly priced (other than pumping costs), perhaps such issue is not surprising that users do not meter the volumes of water usage. Beside the industry, agricultural sector is by far the biggest groundwater consumer of this country, contributing significant amount of annual meter drop in the groundwater table to the annual decline of groundwater table. Additionally, the groundwater resources are severely affected by, pollution, encroachment and overexploitation. National Water Policy (1999) and Bangladesh Water Act (2013) are considered as country's pivotal legal framework but both of these lag behind to provide effective guidelines on permission, extraction limit, monitoring, protection of quality, water harvesting procedure, and recharge mechanism. Existing institutions suffer from consistent crisis, politics, corruption, absence of public participation and coordination of other institutions, mismanagement, and empirical assessment. This study evaluates the existing water related policies and functions of multidimensional institutions, and discusses the key challenges of effective groundwater management. The present paper also provides an overview of established practices around the world to cope with the common challenges.

Hydrochemical investigations of groundwater and surface water were carried out to better understand the spatial distribution of As, major ions and trace elements. The study was carried out to evaluate the sources of dissolved species and elucidate the processes that govern the evolution of natural water in the Lower Katari Basin. The study area is close to the Titicaca Lake (Cohana Bay) formed by sediments of the Quaternary system, deposited in the fluvio-glacial to fluvio-lacustrine environment and geologic formations of the Devonian and Neogene system of volcanic origin. The study area has several environmental problems mainly caused by contaminants such as heavy metals, nutrients, and bacteria. These problems are linked to the urban and industrial wastes, natural geologic conditions, and mining activities carried out upstream of the Katari Basin, where rivers discharge into the Cohana Bay. A total of 37 water samples were collected during wet season, 31 groundwater samples including drinking water wells and six surface water samples. The hierarchical cluster analysis and principal component analysis were applied to hydrochemical data. Results show high salinity in groundwater related to the evaporation causing serious problems for the groundwater quality and rendering it unsuitable for drinking. Dissolved As concentration ranges from 0.7 to 89.7 μg/L; the principal source of As could be the alteration of volcanic rocks, more than 48% of the shallow groundwater samples exceeded the WHO guideline value for As and more than 22% for NO3 -. Groundwater has neutral to slightly alkaline pH, and moderately oxidizing character. The groundwater chemistry reveals considerable variability, ranging from Na-SO4,Cl type through mixed Na-HCO3 type and Ca,Na-HCO3,Cl type. The distribution of trace elements shows a large range of concentrations. Speciation of As indicates that the predominant oxidation state is As (V). The geochemical modelling indicates that As could be associated with iron oxides and hydroxides which are probably the most important mineral phases for the As adsorption. The spatial distribution and the variation of dissolved As concentration in groundwater is governed by the variability in geological characteristics of the region that raises a significant concern about drinking water quality.