High Concentrations Of Arsenic Research Articles

Arsenic causing gallbladder cancer disease in Bihar

In recent times Gallbladder cancer (GBC) incidences increased many folds in India and are being reported from arsenic hotspots identified in Bihar. The study aims to establish association between arsenic exposure and gallbladder carcinogenesis. In the present study, n = 200 were control volunteers and n = 152 confirmed gallbladder cancer cases. The studied GBC patient’s biological samples-gallbladder tissue, gallbladder stone, bile, blood and hair samples were collected for arsenic estimation. Moreover, n = 512 gallbladder cancer patients blood samples were also evaluated for the presence of arsenic to understand exposure level in the population. A significantly high arsenic concentration (p < 0.05) was detected in the blood samples with maximum concentration 389 µg/L in GBC cases in comparison to control. Similarly, in the gallbladder cancer patients, there was significantly high arsenic concentration observed in gallbladder tissue with highest concentration of 2166 µg/kg, in gallbladder stones 635 µg/kg, in bile samples 483 µg/L and in hair samples 6980 µg/kg respectively. Moreover, the n = 512 gallbladder cancer patient’s blood samples study revealed very significant arsenic concentration in the population of Bihar with maximum arsenic concentration as 746 µg/L. The raised arsenic concentration in the gallbladder cancer patients’ biological samples—gallbladder tissue, gallbladder stone, bile, blood, and hair samples was significantly very high in the arsenic exposed area. The study denotes that the gallbladder disease burden is very high in the arsenic exposed area of Bihar. The findings do provide a strong link between arsenic contamination and increased gallbladder carcinogenesis.

Study on the relationship between hydrodynamic conditions and arsenic content in Quaternary sediments.

Groundwater is susceptible to arsenic contamination by sediment with high arsenic content, which is the primary culprit of regional arsenic pollution and poisoning. To explore the influence of the change in hydrodynamic conditions caused by changes in the sedimentary environment over time on arsenic content in sediments during the Quaternary, the hydrodynamic characteristics and arsenic content enrichment of borehole sediments were studied in typical high-arsenic groundwater areas of the Jianghan-Dongting Basin, China. The regional hydrodynamic conditions represented by each borehole location were analyzed, the correlation between the variation in groundwater dynamics characteristics and arsenic content in different hydrodynamic periods was analyzed, and the relationship between arsenic content and grain size distribution was quantitatively investigated using grain size parameter calculation, elemental analysis, and statistical estimates of arsenic content in borehole sediments. We observed that the relationship between arsenic content and hydrodynamic conditions differed between sedimentary periods. Furthermore, arsenic content in the sediments from the borehole at Xinfei Village was significantly and positively correlated with a grain size of 127.0-240.0μm. For the borehole at Wuai Village, arsenic content was significantly and positively correlated with a grain size of 1.38-9.82μm size (at 0.05 level of significance). However, arsenic content was inversely correlated with grain sizes of 110.99-716.87 and 133.75-282.07μm at p values of 0.05 and 0.01, respectively. For the borehole at Fuxing Water Works, arsenic content was significantly and positively correlated with a grain size of 409.6-655.0μm size (at 0.05 level of significance). Arsenic tended to be enriched in transitional and turbidity facies sediments with normal corresponding hydrodynamic strength but poor sorting. Furthermore, continuous and stable sedimentary sequences were conducive to arsenic enrichment. Fine-grain sediments provided abundant potential adsorption sites for high-arsenic sediments, but finer particle size was not correlated with higher arsenic levels.

Molecular level insight of thiocyanate degradation by Pseudomonas putida TDB-1 under a high arsenic and alkaline condition

It is a big challenge to bioremediate thiocyanate pollution in the gold extraction heap leaching tailings and surrounding soils with high contents of arsenic and alkali. Here, a novel thiocyanate-degrading bacterium Pseudomonas putida TDB-1 was successfully applied to completely degrade 1000 mg/L thiocyanate under a high arsenic (400 mg/L) and alkaline condition (pH = 10). It also leached the contents of thiocyanate from 1302.16 to 269.72 mg/kg in the gold extraction heap leaching tailings after 50 h. The maximum transformation rates of S and N in thiocyanate to the two finial products of SO42− and NO3− were 88.98 % and 92.71 %, respectively. Moreover, the genome sequencing confirmed that the biomarker gene of thiocyanate-degrading bacterium, CynS was identified in the strain TDB-1. The bacterial transcriptome revealed that critical genes, such as CynS, CcoNOQP, SoxY, tst, gltBD, arsRBCH and NhaC, etc. in the thiocyanate degradation, S and N metabolisms, and As and alkali resistance were significantly up-regulated in the groups with 300 mg/L SCN− (T300) and with 300 mg/L SCN− and 200 mg/L As (TA300). In addition, the protein-protein interaction network showed that the glutamate synthase encoding by gltB and gltD served as central node to integrate the S and N metabolism pathways with thiocyanate as substrate. The results of our study provide a novel molecular level insight for the dynamic gene expression regulation of thiocyanate degradation by the strain TDB-1 with a severe arsenic and alkaline stress.

Controlling Arsenic Accumulation in Rice Grain under Nanomaterials-Assisted Optimal Greenhouse Set-Up

Rice is being increasingly exposed to inorganic arsenic and this affects half of the world population because they are rice consumers. In this study, pot experiments were carried out to investigate the effect of two dose-dependent nanomaterials (silica and graphene) treatment on varied arsenic levels (2, 7 and 12 mg/kg). The results showed that both nanomaterials were affected significantly with 1 mg/mL of nanomaterial. Arsenic adversely affected the plant height, tillering, number of grains, and grain weight and when high concentrations of arsenic were applied at 12 mg/kg, the plant could not withstand it and died before 75 days even in the presence of graphene. Based on inductively coupled plasma mass spectrometry analysis, silica nanoparticles showed the highest inhibition on the total accumulation of arsenic as 93% (control plant), 84% (2 mg/kg), 67% (7 mg/kg) to 35 % (12 mg/kg), whereas graphene showed lower inhibition percentages. This outcome confirms that silica nanoparticles prevent arsenic uptake, because they translocate from the root to the grains and are able to offer a promising way to reduce consumer health risk.

Conditioning of POX slurry and its effect on pressure oxidation performance of refractory gold sulphide ore

This paper describes the results of a laboratory study that looked at the conditioning of POX slurries produced by pressure oxidation (225 oC) of refractory gold flotation concentrates. The authors used a case study of sulphide concentrates produced as a result of flotation of refractory gold ores of the Malomyr and Pioner deposits to define the conditioning parameters applicable to POX slurries: i.e. temperature &mdash; 95 oC, duration &mdash; 2 to 4 hours. The above conditions help improve the quality of POX cakes before cyanidation so that the POX residue contained less sulphate sulphur and the cake weight could be lowered by 40&ndash;70%. The authors looked at the relationship between the conditioning parameters (60&ndash;95 oC with the duration of up to 7 hours) and the solids yield. They also examined how the above parameters influenced the transfer of the key components (i.e. iron, sulphur and arsenic) into liquid phase. In particular, the authors examined the process of conditioning POX cakes obtained from concentrates with the minimum (up to 2%) and high (8&ndash;10%) concentration of arsenic. The paper examines how the material composition of POX products tends to change after conditioning when dealing with sulphide concentrates. Conditioning was found to benefit the recovery of gold from POX cakes when dealing with high-arsenic concentrates. The gold particles in cakes can be encapsulated by mixed arsenate/sulphates of iron(III), which get dissolved during atmospheric conditioning, and the gold surface becomes available for cyanide solution. After conditioning, the share of cyanidable gold in POX cakes increases by 3.0 to 5.5%.

Medium-Term Effects of Sprinkler Irrigation Combined with a Single Compost Application on Water and Rice Productivity and Food Safety.

Traditional rice (Oryza sativa L.) management (tillage and flooding) is unsustainable due to soil degradation and the large amount of irrigation water used, an issue which is exacerbated in the Mediterranean region. Therefore, there is a need to explore rice management strategies in order to improve water-use efficiency and ensure its sustainability. Thus, field experiments were conducted to determine the medium-term effects of different irrigation and tillage methods combined with a single compost application on water and rice productivity, as well as food safety in a semiarid Mediterranean region. The management systems evaluated were: sprinkler irrigation in combination with no-tillage (SNT), sprinkler irrigation in combination with conventional tillage (ST), which were implemented in 2015, and flooding irrigation in combination with conventional tillage (FT), and their homologues (SNT-C, ST-C, and FT-C) with single compost application in 2015. In reference to rice grain yield, the highest values were observed under ST treatment with 10 307 and 11 625 kg ha-1 in 2018 and 2019 respectively; whereas between FT and SNT there were no significant differences, with 8 140 kg ha-1 as mean value through the study. Nevertheless, sprinkler irrigation allowed saving 55% of the total amount of water applied in reference to flooding irrigation. Furthermore, the highest arsenic concentration in grains was found under FT but it decreased with compost application (FT-C) and especially with sprinkler irrigation, regardless of tillage management systems. However, sprinkler irrigation favors the cadmium uptake by plants, although this process was reduced under SNT in reference to ST, and especially under amended compost treatments. Therefore, our results suggested that a combination of sprinkler irrigation and compost application, regardless of the tillage system, could be an excellent strategy for rice management for the Mediterranean environment in terms of water and crop productivity as well as food safety.

Arsenic enrichment in the north Gangetic Plains of Laksar, Uttarakhand, India

This study reports new data on arsenic contamination in groundwater in Laksar, a pristine and semi-rural region of India's Himalayan state of Uttarakhand. Based on a systematic investigation of hydrogeochemical parameters influencing arsenic mobilisation, the most plausible mechanism of arsenic release into groundwater has been proposed. The groundwater in the research area is mostly homogeneous, with the Ca–Mg–HCO3 facies accounting for 87.5 percent of groundwater samples. The combined effect of silicate weathering, and the dissolution of carbonate minerals predominantly influence Laksar groundwater composition, as evident from bivariate plots of Mg/Na vs. Ca/Na and HCO3−/Na vs. Ca/Na. The statistical analysis (PCA and correlation analysis) performed on the geochemical data indicates that natural processes such as carbonate weathering, reductive dissolution of Fe/Mn minerals together with anthropogenic activities such as the utilization of fertilizers in agricultural fields, human and animal waste disposal, exert control on the major ion chemistry, and As enrichment in groundwater. The study area has extremely high arsenic concentrations, ranging from 0.60 to 91.21 μg/L (mean: 15.63 μg/L), with majority of groundwater samples (>50%) having arsenic contents exceeding the WHO permitted limit (10 μg/L). Analysis of the Eh-pH diagram shows that As(III) species (H3AsO3) accounts for 79% of samples, whereas As (V) species (HAsO4−) accounts for the remaining. The observed arsenic enrichment in groundwater can be attributed to As desorption from iron oxide/hydroxide minerals via reductive dissolution mechanism under reducing groundwater conditions, which is supported by negative Eh values and high levels of Fe and comparatively low levels of sulphate and nitrate.

The influence of gold mining wastes on the migration-transformation behavior and health risks of arsenic in the surrounding soil of mined-area

Understanding the characteristic heavy metals and their migration-transformation behavior in mining areas is essential for the prevention and control of mining pollution. This study selected a gold mine in the Anqing-Guichi ore-cluster region in the Middle-Lower Yangtze metallogenic belt as the research area, the concentrations, and migration-transformation mechanisms of metalloid As and typical heavy metals (Cd, Zn, Pb, Cu, Cr, and Ni) in gold mining wastes (mine tailings and sewage sludge) and the surrounding soil (farmland soil and soil a mining area) were investigated. The results showed that the concentration of As was high in both mining wastes and soils, and the geo-accumulation index values of As in soils ranging from 1.44–6.70, indicated that As pollution was severe in the soil. Besides, a close correlation between the concentration of As and the content of iron was observed by XRF analysis, in conjunction with SEM observations, most As-bearing phases are embedded in Fe, O, and Si compounds. According to EDS and XPS results, the Fe-O-As particle was suggested to be Fe-(oxy)hydroxides with absorbed or co-precipitated As. Furthermore, the arsenic phase observed in the soils were consistent with the weathering oxidation products in the tailings, demonstrating that the mineral particles in the tailings could migrate into soils via atmospheric transport, rainwater leaching, surface runoff, etc., and consequently result in heavy metal accumulation. The sequential chemical extraction result showed that the residual state of As in the soil exceeded 60%, and As posed no risk to low risk according to the Risk assessment code result. However, due to the high concentration and high mobility of arsenic, its environmental impact cannot be ignored even if its bio-accessibility in mined area soil is low.

Seasonal arsenic in catfish (Siluriformes, Ariidae) and the hydrochemical conditions of two areas in a Ramsar site on the Brazilian coast

The construction of a data bank concerning metal and metalloid content of bioindicator fish from coastal areas is very important as it can help environmental managers in decision making. In natural conditions, the concentration of elements can be influenced by abiotic parameters such as water salinity. In this study, catfish Cathorops spixii were evaluated concerning the total arsenic (As) concentration in the muscle tissues of individuals subjected to different abiotic conditions in the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC), which was recently included on the Ramsar list of wetlands of international importance. Seventy-four catfish were seasonally caught in the northern and southern regions of the CIELC and their hydrochemical parameters were obtained. C. spixii from the southern, best preserved, area showed arsenic concentrations around ten times higher than the maximum limit established for fish intended for human consumption. However, these high concentrations of arsenic could be associated with the abiotic parameters of the water, such as salinity variations, in this area.

Assessment of soil contamination by heavy metals and arsenic in Tamesguida abandoned copper mine area, Médéa, Algeria.

Heavy metal and arsenic pollution of soil remains a serious environmental problem long after mining operations have ended. For instance, the Tamesguida copper mine located in north-central Algeria has been abandoned for several decades without restoration or even an environmental impact assessment. Therefore, soils were collected from several locations in the vicinity of the old mine and tailings and analyzed for their Cu, Cr, As, Pb, Ni, Zn, and Fe rates to gauge the scope of the soil contamination caused by these elements, and assessing their origin and their dispersion in the mine area. High copper and arsenic contents were recorded in tailings and surrounding soils, far exceeding the world average shale, crustal average, and local soils. Except for lead, the spatial distribution of heavy metals and As shows a decrease in content as one moves away from the tailings, and the correlation matrix and PCA performed associate the origin of these elements with previous mining activities. The pollution indices, notably contamination degree (CD) and the pollution load index (PLI), categorize the site as a highly polluted area.

The key role of biogenic arsenic sulfides in the removal of soluble arsenic and propagation of arsenic mineralizing communities

Biogeochemical processes govern the transport and availability of arsenic in sediments. However, little is known about the transition from indigenous communities to cultivable consortia when exposed to high arsenic concentrations. Such cultivable communities could be exploited for arsenic bioremediation of waste streams and polluted sites. Thus, it is crucial to understand the dynamics and selective pressures that shape the communities during the development of customized bacterial consortia. First, from the arsenic partitioning of two sediments with high arsenic concentrations, we found that up to 55% of arsenic was bioavailable because it was associated with the soluble, carbonate, and ionically exchangeable fractions. Next, we prepared sediment enrichment cultures under arsenate- and sulfate-reducing conditions to precipitate arsenic sulfide biominerals and analyze the communities. The produced biominerals were used as the inoculum to develop bacterial consortia via successive transfers. Tracking of the 16S rRNA gene in the fresh sediments, sediment enrichments, biogenic minerals, and bacterial consortia revealed differences in the bacterial communities. Removing the sediment caused a substantial decrease in diversity and shifts toward the dominance of the Firmicutes phylum to the detriment of Proteobacteria. In agreement with the 16S rRNA gene results, the sequencing of the arrA gene confirmed the presence of phylotypes closely related to Desulfosporosinus sp. Y5 (100% similarity), highlighting the pivotal role of this genus in the removal of soluble arsenic. Here, we demonstrated for the first time that besides being important as arsenic sinks, the biogenic arsenic sulfide minerals are reservoirs of arsenic resistant/respiring bacteria and can be used to culture them.

Nanoplastics promote arsenic-induced ROS accumulation, mitochondrial damage and disturbances in neurotransmitter metabolism of zebrafish (Danio rerio)

As a carrier, nanoplastics (NPs) can adsorb other toxic substances and thus modify their biological toxicity. Numerous studies have investigated the neurotoxic of high concentrations of arsenic (As, 2.83 mg/L-5 mg/L). However, it is still unknown whether the relatively low environmentally relevant concentrations of As (200 μg/L) can damage the structure and function of fish brains with the presence of NPs. In this study, zebrafish were exposed to polystyrene NPs, As and their mixture for 30 days respectively. Firstly, we found that the presence of NPs promoted the accumulation of As in zebrafish brains. Thereby the co-exposure of NPs and As further promoted the production of reactive oxygen species (ROS) in zebrafish brains compared with the single exposure of NPs or As, resulting in severe oxidative stress. Moreover, accumulated ROS directly damaged the mitochondrial membrane and mtDNA in zebrafish brains. Moreover, the mitochondrial damage was further aggravated due to inhibited mitochondrial fusion and activated mitochondrial division and mitophagy. Ultimately, the co-exposure led to mitochondrial damage in the zebrafish brain. Damaged mitochondria may not meet the high energy metabolic requirement for neuronal function. As a result, the normal function of nerve cells was adversely affected and eventually cell apoptosis may occur. Besides, the co-exposure caused more significant structural alterations in zebrafish brain tissue. Finally, the co-exposure of NPs and As caused abnormal biosynthesis and degradation of dopamine and acetylcholine. These resulted in decreased dopamine levels and increased acetylcholine levels in zebrafish brains. In conclusion, the presence of NPs promoted the accumulation of As, thereby inducing severe oxidative stress, which caused structural alterations and mitochondrial damage in the zebrafish brain, thus disordering neuromodulation, which may ultimately cause neurological dysfunction in zebrafish. This study will provide a risk assessment for evaluating the biotoxicity of NPs and As to fish and even other animals.

Accumulation of heavy metals and arsenic by living organisms at the waste dump of a gold processing plant

The soil samples were taken from different depths, as well as plant samples and tissue and wool samples of small mammals Talpa europaea to study the ecological situation in the conditions of Novotroitsk tailing dump, the dumping site of Novotroitsk gold-arsenic deposits. For comparison, samples of plants, tissues, and wool of animals from background areas of the Kabanka River and Demarino village were obtained. The greatest interest was to determine the content of arsenic and heavy metals such as cadmium, copper, lead, and zinc in the samples. All samples from the tailing dump showed multiple exceedances of arsenic and heavy metals. On average, there was 1,286 times more arsenic in the soil than is allowed by health standards. It was noted that the accumulation of heavy metals and arsenic in plants is uneven and depends on the taxonomic affiliation and part of the plant, but exceeding the background levels were found in all samples. In animals, the highest concentrations of arsenic were found in wool; body organs – liver, exceeding the background values 181.3-273.9. There was also a noticeable accumulation of lead and copper in the liver. Thus, the ecology of the tailing dump area is in a depressed state, and comprehensive reclamation measures are needed.

Geochemistry and textural evolution of As-Tl-Sb-Hg-rich pyrite from a sediment-hosted As-Sb-Tl-Pb ± Hg ± Au mineralization in Janjevo, Kosovo

The sediment-hosted As-Sb-Tl-Pb ± Hg ± Au Janjevo occurrence is located in the southern part of the Kizhnica-Hajvalia-Badovc ore field, in the Trepça (Trepča) Mineral Belt (TMB) in Kosovo. The As-Sb-Tl-Pb ± Hg ± Au mineralization is hosted by Upper Triassic marbles and occurs in the form of quartz-stibnite veins and dolomitized irregular pockets associated with jasperoid rocks. The main sulfide most widespread in the mineralization studied is pyrite which is the main carrier of thallium. A wide range of techniques was used to characterize the geochemistry and textural evolution of pyrite/marcasite from Janjevo: polarized reflected-light microscopy, electron microprobe (EPMA), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), X-ray powder diffraction (XRPD), Mössbauer spectroscopy, and isotopic studies. The study of 42 thin and polished sections resulted in the identification of 4 generations of pyrite/marcasite. The first generation of pyrite related to the pre-ore stage occurs as framboidal pyrite with different degrees of evolution (Py1a), as well as recrystallized pyrite/marcasite (Py1b). Au-enriched pyrite (Py2) occurs as elongated fibrous aggregates and is genetically associated with the formation of stibnite veins (Sb stage). As-Tl-Sb-Hg pyrite (Py3) forms irregular colloform aggregates which fill the stylolites and also overgrow older generations of pyrite. The youngest generation is represented by marcasite (Py4), which forms euhedral crystals. Co/Ni ratio < 1 in all pyrite/marcasite generations implies a sedimentary fingerprint. On the other hand, δ34S isotopic studies confirm a magmatic sulfur source for As-Tl-Sb-Hg pyrite (Py3), as well as co-occurring stibnite and realgar. The most important minor and trace elements in pyrite/marcasite are As (up to 14.1 %), Tl (up to 3.94 %), Sb (up to 3.73 %), and Hg (up to 0.55 %), which are mainly hosted by Py3. In addition to arsenic, thallium, antimony, and mercury, other generations of pyrite show enrichment in Ni, Co, and Cu (framboidal pyrite Py1), Au, and Se (Au-enriched pyrite Py2), and Se (marcasite Py4). The highest gold content of up to 6.08 ppm was recorded at Py2. Studies on Py3 geochemistry confirm the presence of 2Fe2+ ↔ Tl+ + Sb3+ heterovalent substitution in pyrite. As-Tl-Sb-Hg pyrite (Py3) is the main thallium host mineral in the mineralization studied, with significantly less thallium present in the Pb-Sb ± Tl ± As sulfosalts. In addition, the high arsenic content of Py3 is due to the presence of arsenic in the form of As1− and As0 related to amorphous arsenic-rich nanoparticles. The reported Py3 is the best phenomenon of the crystallization of colloform As-Tl-Sb-Hg-rich pyrite under hydrothermal conditions. Pyrite-rich sediment-hosted As-Sb-Tl-Pb ± Hg ± Au mineralization from Janjevo is associated with the distal manifestation of a concealed porphyry system.

Elevated Urbanization-Driven Plant Accumulation of Metal(loid)s Including Arsenic Species and Assessment of the Kłodnica River Sediment Contamination

The impact of water and bottom sediment pollution of a river subjected to a strong industrial anthropogenic pressure of metal(loid) (including arsenic and its species) accumulation in riverbank plants such as Solidago virgaurea L., Phragmites L. and Urtica dioica L. was investigated. The high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) technique was used to study organic and inorganic arsenic species in selected plants and their response to heavy metal and arsenic contamination. The modified BCR extraction results showed that arsenic was mainly bound to the mobile reducible and organic-sulfide fractions in the Kłodnica River bottom sediments. Research has shown that the bottom sediments of the Kłodnica River are contaminated with metals, including Pb, Zn, Ni, As, and among arsenic species, the As(V) form dominated quantitatively, with its highest concentration being 49.3 mg kg−1 and the organic species occurred extremely rarely. The highest concentration of arsenic, among the tested plants, occurred in Phragmites communis L. The evaluation of the bottom sediment pollution was performed using Sb/As factor, geoaccumulation index (Igeo), enrichment factor (EF) and pollution load index (PLI). The ability of the plant to assimilate metals from the substrate was studied by calculation of the bioaccumulation factor (BAF). Values of the Igeo change in a wide range from class 1 (uncontaminated to moderately polluted for Cu and Zn) at the first sampling point, to 5 (highly to extremely polluted for Ba and Fe) at the K4 sampling point. The Igeo results show an increase in the contamination with elements toward the runoff of the Kłodnica River.

Eco-friendly extraction of arsenic and tungsten from hazardous tungsten residue waste by pressure oxidation leaching in alkaline solutions: Mechanism and kinetic model

Tungsten residue waste (TRW), considered an environmental burden due to high content and excessive leaching toxicity of arsenic (As), are also secondary tungsten (W) resources. A novel method for simultaneous extraction of arsenic and tungsten from TRW via alkaline pressure oxidative leaching was proposed. The results show that As in the TRW mainly exists in the form of As coprecipitated with Mn(Ⅱ) oxides and FeAsS. In addition, As coprecipitated with Mn(Ⅱ) oxides and W are encapsulated in Fe, Mn oxides. The structure of Fe, Mn oxides with dense surface can be destroyed and the chemically stable arsenopyrite can be efficiently oxidized by oxygen in alkaline solutions. The leaching efficiency of As and S reached 97% and 99% at 80 min, respectively, while that of W reached 82% at 10 min. The leaching rate of As and S is controlled by diffusion with the apparent activation energies of 16.67 kJ/mol and 15.66 kJ/mol, respectively. Compared with TRW, the leaching toxicity of As in the leach residue decreased from 10.2 mg/L to only 0.071 mg/L. The new process suggests new possibilities for removal and recovery of As and W from TRW that will contribute to circular economy and environmental protection.

A feasible strategy for deep arsenic removal and efficient tungsten recovery from hazardous tungsten residue waste with the concept of weathering process strengthening

Tungsten residue waste (TRW), generated by tungsten hydrometallurgy, is classified as a hazardous solid waste by Chinese government due to its high content and leaching toxicity of arsenic, but is also a typical critical metal secondary resource of tungsten. Deep arsenic removal and tungsten recovery of TRW are beneficial to waste harmless treatment and circular economy. However, the occurrence state and weathering mechanism of arsenic in TRW have not been investigated and reported, which is the fundamental reason why the harmless treatment of TRW has become a bottleneck problem. In this paper, a feasible and novel strategy for deep arsenic removal and efficient tungsten recovery from TRW was proposed based on the concept of weathering process strengthening. The results show that arsenic in TRW mainly exists in the form of arsenopyrite, and ionically bound arsenic (V) generated by weathering of arsenopyrite directly leads to leaching toxicity of arsenic in TRW exceeding 5 mg/L. The environmental risk of arsenic in TRW can be completely eliminated by strengthening the uncontrollable and slow weathering process of TRW into a controllable and efficient process. Over 98 % of arsenic and 84 % of tungsten were simultaneously leached from TRW under optimal conditions via an enhanced pressure oxidation leaching process in alkaline solutions based on the leaching thermodynamic and kinetic, resulting in only 0.07 mg/L of arsenic leaching toxicity in the secondary leach residue. Hydrated ferric oxide (HFO) generated by the leaching process provides the possibility for the diffusion of reactants and products, so that arsenic and tungsten can be high-efficiently leached. The harmless secondary leach residue can be used as a raw material for the production of building materials, cement, and glass. Taking into account the reduction of alkali consumption and recovery of tungsten and arsenic, the leach solution was recycled. The closed-loop strategy shows great promise for the harmless treatment and tungsten recovery of TRW on an industrial scale to promote circular economy and environmental protection.

Analysis of the geological control on the spatial distribution of potentially toxic concentrations of As and F- in groundwater on a Pan-European scale

The distribution of the high concentrations of arsenic (As) and fluoride (F-) in groundwater on a Pan-European scale could be explained by the geological European context (lithology and structural faults). To test this hypothesis, seventeen countries and eighteen geological survey organizations (GSOs) have participated in the dataset. The methodology has used the HydroGeoToxicity (HGT) and the Baseline Concentration (BLC) index. The results prove that most of the waters considered in this study are in good conditions for drinking water consumption, in terms of As and/or F- content. A low proportion of the analysed samples present HGT≥ 1 levels (4% and 7% for As and F-, respectively). The spatial distribution of the highest As and/or F- concentrations (via BLC values) has been analysed using GIS tools. The highest values are identified associated with fissured hard rock outcrops (crystalline rocks) or Cenozoic sedimentary zones, where basement fractures seems to have an obvious control on the distribution of maximum concentrations of these elements in groundwaters.

Drinking Water Supply in the Region of Antofagasta (Chile): A Challenge between Past, Present and Future.

Since the mid-nineteen century, when the first mining companies were established in the region of Antofagasta to extract saltpeter, mining managers and civil authorities have always had to face a number of problems to secure a water supply sufficient for the development of industrial activities and society. The unique features of the region, namely the scarcity of rainfall, the high concentration of arsenic in freshwaters and the increasing pressure of the mining sector, have made the supply of drinking water for local communities a challenge. In the 1950s, the town of Antofagasta experienced a serious drinking water crisis. The 300 km long aqueduct starting from the Toconce catchment, opened in 1958, temporarily ended this shortage of drinking water but created an even more dramatic problem. The concentration of arsenic in the water consumed by the population had grown by approx. ten times, reaching the value of 0.860 mg/L and seriously affecting people's health. The water treatment plants (WTPs) which were installed starting from the 1970s in the region (namely the Old and New Salar del Carmen in Antofagasta and Cerro Topater in Calama, plus the two recent desalination plants in Antofagasta and Tocopilla), have ensured, since 2014, that the drinking water coverage in the urban areas was practically universal (>99.9%). However, the rural areas have continued to experience significant shortcomings regarding their capacity to ensure the quality and continuity of the water supply service in the long run. Presently, approx. 42% of the rural population of the region of Antofagasta does not have a formal supply of drinking water. The recent amendments to the Chilean Water Code (March 2022) and the interventions carried out in the framework of the Agua Potable Rural (APR) program were intended to reduce the socio-ecological inequalities due to the lack of drinking water in the semi-concentrated and isolated rural population.

Trace elements and δ15N values in micronekton of the south-western Indian Ocean.

Trace elements and δ15N values were analysed in micronekton (crustaceans, fishes and squids) sampled in the south-western Indian Ocean. Myctophids were associated with high concentrations of arsenic at La Pérouse and MAD-Ridge seamounts, and with lead and manganese at MAD-Ridge and in the Mozambique Channel. The difference in cadmium, copper and zinc concentrations between micronekton broad categories reflected differing metabolic and storage processes. When significant, negative relationships were found between micronekton body size and trace element concentrations, which can possibly be attributed to differing metabolic activity in young and old individuals, dietary shifts and/or dilution effect of growth. No relationships were found between trace element concentrations and δ15N values of micronekton (except cobalt which decreased with increasing δ15N values), since most trace elements are not biomagnified in food webs due to regulation and excretion processes within organisms. All trace element pairs were positively correlated in fishes suggesting regulation processes.