Hotspots of Dissolved Arsenic Generated from Buried Silt Layers along Fluctuating Rivers.

Previous studies along the banks of the tidal Meghna River of the Ganges-Brahmaputra-Meghna Delta demonstrated the active sequestration of dissolved arsenic (As) on newly formed iron oxide minerals (Fe(III)-oxides) within riverbank sands. The sand with high solid-phase As (>500 mg/kg) was located within the intertidal zone where robust mixing occurs with oxygen-rich river water. Here we present new evidence that upwelling groundwater through a buried silt layer generates the dissolved products of reductive dissolution of Fe(III)-oxides, including As, while mobilization of DOC by upwelling groundwater prevents their reconstitution in the intertidal zone by lowering the redox state.

A review on the fate of micro and nano plastics (MNPs) and their implication in regulating nutrient cycling in constructed wetland systems.

This review discusses the micro-nano plastics (MNPs) and their interaction with physical, chemical and biological processes in a constructed wetland (CW) system that is typically used as a nature-based tertiary wastewater treatment for municipal as well as industrial applications. Individual components of the CW system such as substrate, microorganisms and plants were considered to assess how MNPs influence the CW processes. One of the main functions of a CW system is removal of nutrients like nitrogen (N) and phosphorus (P) and here we highlight the pathways through which the MNPs influence CW's efficacy of nutrient removal.

Origin of tungsten and geochemical controls on its occurrence and mobilization in shallow sediments from Fallon, Nevada, USA.

Tungsten (W) occurrence and speciation was investigated in sediments collected from Fallon, Nevada where previous studies have linked elevated W levels in human body fluids to an unusual cluster of childhood leukemia cases. The speciation of sedimentary W was determined by μ-XRF mapping and μ-XANES. The W content of the analyzed surface sediments ranged between 81 and 25,908 mg/kg, which is significantly higher than the W content in deeper sediments which ranged from 37 to 373 mg/kg at 30 cm depth.

Occurrence and distribution of high arsenic in sediments and groundwater of the Claromecó fluvial basin, southern Pampean plain (Argentina).

Occurrences of high arsenic (As) in sediments and groundwaters were investigated in the Claromecó fluvial basin, southern Pampean plain, Argentina. This investigation includes sedimentology, mineralogy, and hydrogeochemistry of the Neogene and Quaternary aquifers to determine possible sources and transport mechanisms for As in the Claromecó basin. Characterization of the sediments revealed homogeneous mineralogy in both Neogene highlands and Quaternary floodplains with abundant plagioclase, volcanic glass shards (VGS), K-feldspar, quartz, clay minerals and minor concentrations of clinopyroxenes, orthopyroxenes, hornblende, epidote, Fe-(oxy)hydroxides and fluorapatite.

Investigating Fluorescent Organic-Matter Composition as a Key Predictor for Arsenic Mobility in Groundwater Aquifers.

Dissolved organic matter (DOM) is linked to the heterogeneous distribution of elevated arsenic (As) in groundwater used for drinking and irrigation purposes, but the relationship between DOM characteristics and arsenic mobility has yet to be fully understood. Here, DOM from groundwater sampled in the Bengal Basin region was characterized using both conventional bulk emission-excitation (EEM) spectroscopy and high-performance size-exclusion chromatography coupled to spectroscopy (HPSEC-EEM). Notably, application of the novel HPSEC-EEM approach permitted the total fluorescence of individual samples to be independently resolved into its underlying components.

Water Recovery from Advanced Water Purification Facility Reverse Osmosis Concentrate by Photobiological Treatment Followed by Secondary Reverse Osmosis.

Reverse osmosis (RO)-based desalination and advanced water purification facilities have inherent challenges associated with concentrate management and disposal. Although enhanced permeate recovery and concentrate minimization are desired, membrane scaling due to inorganic constituents, such as silica, calcium, phosphate, and iron, hinders the process. To solve this problem, a new diatom-based photobiological process has been developed to remove these scaling constituents by biological uptake and precipitation.

Influence of monsoonal recharge on arsenic and dissolved organic matter in the Holocene and Pleistocene aquifers of the Bengal Basin.

Arsenic (As) mobilization in the Bengal Basin aquifers has been studied for several decades due to the complex redox bio-geochemistry, dynamic hydrogeology and complex nature of dissolved organic matter (DOM). Earlier studies have examined the changes in groundwater As in the dry season before monsoon and during the wet season after monsoonal recharge. To investigate the more immediate influence of recharge during the active monsoon period on As mobilization and DOM character, groundwater samples were analyzed in the pre-monsoon and during the active monsoon period.

Dissolved fulvic acids from a high arsenic aquifer shuttle electrons to enhance microbial iron reduction.

It was demonstrated more than two decades ago that microorganisms use humic substances, including fulvic acid (FA), as electron shuttles during iron (Fe) reduction in anaerobic soils and sediments. The relevance of this mechanism for the acceleration of Fe(III) reduction in arsenic-laden groundwater environments is gaining wider attention. Here we provide new evidence that dissolved FAs isolated from sediment-influenced surface water and groundwater in the Bengal Basin were capable of electron shuttling between Geobacter metallireducens and Fe(III).