High Concentrations Of As Research Articles

Speciation, mobilization, and bioaccessibility of arsenic in geogenic soil profile from Hong Kong.

The behaviour of arsenic (As) from geogenic soil exposed to aerobic conditions is critical to predict the impact of As on the environment, which processes remain unresolved. The current study examined the depth profile of As in geologically derived subsoil cores from Hong Kong and investigated the mobilization, plant availability, and bioaccessibility of As in As-contaminated soil at different depths (0-45.8m). Results indicated significant heterogeneity, with high levels of As in three layers of soil reaching up to 505mg/kg at a depth of 5m, 404mg/kg at a depth of 15m, and 1510mg/kg at a depth of 27-32m. Arsenic in porewater samples was <11.5μg/L in the study site. X-ray absorption spectroscopy (XAS) indicated that main As species in soil was arsenate (As(V)), as adsorbed fraction to Fe oxides (41-69% on goethite and 0-8% on ferrihydrite) or the mineral form scorodite (30-57%). Sequential extraction procedure demonstrated that 0.5±0.4% of As was exchangeable. Aerobic incubation experiments exhibited that a very small amount (0.14-0.48mg/kg) of As was desorbed from the soil because of the stable As(V) complex structure on abundant Fe oxides (mainly goethite), where indigenous microbes partly (59±18%) contributed to the release of As comparing with the sterilized control. Furthermore, no As toxicity in the soil was observed with the growth of ryegrass. The bioaccessibility of As was <27% in the surface soil using simplified bioaccessibility extraction test. Our systematic evaluation indicated that As in the geogenic soil profile from Hong Kong is relatively stable exposing to aerobic environment. Nevertheless, children and workers should avoid incidental contact with excavated soil, because high concentration of As was present in the digestive solution (<0.1-268μg/L).

Arsenic Hyperaccumulation Strategies: An Overview.

Arsenic (As) pollution, which is on the increase around the world, poses a growing threat to the environment. Phytoremediation, an important green technology, uses different strategies, including As uptake, transport, translocation, and detoxification, to remediate this metalloid. Arsenic hyperaccumulator plants have developed various strategies to accumulate and tolerate high concentrations of As. In these plants, the formation of AsIII complexes with GSH and phytochelatins and their transport into root and shoot vacuoles constitute important mechanisms for coping with As stress. The oxidative stress induced by reactive oxygen species (ROS) production is one of the principal toxic effects of As; moreover, the strong antioxidative defenses in hyperaccumulator plants could constitute an important As detoxification strategy. On the other hand, nitric oxide activates antioxidant enzyme and phytochelatins biosynthesis which enhances As stress tolerance in plants. Although several studies have focused on transcription, metabolomics, and proteomic changes in plants induced by As, the mechanisms involved in As transport, translocation, and detoxification in hyperaccumulator plants need to be studied in greater depth. This review updates recent progress made in the study of As uptake, translocation, chelation, and detoxification in As hyperaccumulator plants.

Effect of farmland type on the transport and spatial distribution of metal(loid)s in agricultural lands near an abandoned gold mine site: Confirmation of previous observations

In many parts of the world, metal(loid)s resulting from mining activities are causing significant environmental concern, in particular because they are contaminating agricultural lands. In this respect, a previous study in South Korea suggested that a specific agricultural practice, associated with the growing of rice in paddy fields, could contribute specifically to the geographic spread of metal(loid)s contamination away from mine sites. The purpose of the research described in this article was to confirm this hypothesis at a different site. Samples from the surface soil of agricultural lands were collected from 374 sites (267 paddy soils and 107 dry field soils). The concentrations of As, Pb, Cd, Cu and Zn from the samples were analyzed and descriptive statistics and multivariate statistical analysis were carried out to identify potential sources of these various elements. In addition, geographical information systems (GIS) technology was applied to analyze the interrelationship between the mining activities and the distribution of meta(loid)s in agricultural lands. The results clearly show that the transport and distribution of As and Pb originating from the abandoned mine are distinct depending on the agricultural practice that was adopted locally. The highest concentrations of As and Pb are in agricultural soils nearest the abandoned mine site (<1km) because of climatic factors such as wind and precipitation that affect the direct mobilization of metal-bearing mine wastes. However, the distribution characteristics of As and Pb in the oxidizing environment of dry field soils in general suggest that the degree of pollution by these elements fell notably as the distance from the abandoned mine increased. In the alternatingly oxidizing and reducing environment of paddy soils, by contrast, the distribution of As and Pb is noticeably different from those of the dry field soils. Arsenic in particular is widely distributed across the study area with a high level of pollution regardless of the distance from the abandoned mine. These results confirm the hypothesis that the transport characteristics of metal(loid)s initially mobilized from an abandoned mine site into the paddy soils are predominantly governed by the specific submerged environment of rice paddy soils and these specific environments impact a wider area than climatic factors.

Sources, speciation and transformation of arsenic in the gold mining impacted Jiehe River, China

Mining-contaminated waters may contain high levels of arsenic (As) and iron (Fe), among various metals and metalloids. The complex behavior of As makes its contamination difficult to remediate. This study aimed to determine the sources, possible association of As and Fe with colloids and their speciation and mobility in the Jiehe River, a stream impacted by gold mining. Particulate (>450 nm), colloidal (7–450 nm), and truely dissolved (<7 nm) forms of As and Fe were determined, and the species of As [As(III), As(V), monomethylarsonic acid, and dimethylarsinic acid] and Fe [Fe(II) and Fe(III)] were both analyzed and modelled using geochemical program Visual MinteQ 3.0. High concentrations of As and Fe were observed in both filtered and particulate forms in most of the water samples. Total As was in the range of 1.0–719 μg L−1 with a median of 140 μg L−1. Total Fe was 0.4–68.2 mg L−1 with a median of 15.0 mg L−1. Arsenic was mainly adsorbed on ferrihydrite, goethite, and hematite in the upstream water samples. In contrast, it was mostly in truely dissolved forms in the water samples at downstream. Visual MinteQ 3.0 modelling results revealed that As adsorbed on, or co-precipitated with, stream sediment can be easily released under the environmental conditions of the downstream reach (11.4–37.5 km). These findings would benefit the environmental management of gold mining impacted Jiehe River, and indicate the need for further quantitative research on As migration facilitated by Fe (hydr)oxide colloids and the release of As from contaminated stream sediments.

Contribution to the improvement of diatom-based assessments of the ecological status of large rivers – The Sava River Case Study

The Sava River Basin is a major drainage basin of southeastern Europe, significantly influenced by anthropogenic activities. Our study was focused on diatom communities as an indicator of the ecological status of running waters. We investigated over 937km of the Sava River at 19 sampling sites. Benthic diatom communities and 17 diatom indices were analyzed along with a large set of environmental parameters. CCA revealed that the most important elements along the spatial gradient were As and Si. Our results show that the species Navicula recens (Lange-Bert.) Lange-Bertalot and Eolimna minima (Grunow) Lange-Bertalot are very abundant at downstream localities where the highest concentrations of As were measured. The number of motile diatoms increased along the nutrient gradient, i.e. with Si availability. Correlations between diatom indices and selected environmental factors showed that temperature, As, Si and Fe are in significant negative correlation with most diatom indices. Analysis revealed the influence of As and metals in water on diatoms, although their concentrations did not exceed environmental standards. While our findings do not confirm that diatom indices reveal the intensity of pressures solely caused by nutrient and/or organic pollutants, they suggest that in moderately polluted large rivers benthic diatoms are good bioindicators of multiple pressures, and that diatom indices could serve as indicators of the level of overall degradation of an ecosystem.

Organochlorine pesticide, antibiotic and heavy metal residues in mussel, crayfish and fish species from a reservoir on the Euphrates River, Turkey

This study investigated the residues of 19 organochlorine pesticides, 37 antibiotics and 5 heavy metals in biota samples (one mussel species, one crayfish species, six wild fish species and one farmed fish species) from the Keban Dam Reservoir on the Euphrates River, Turkey. Among monitored OCPs, only p,p′-DDE was detected in biota samples. It was found only in mussel, fish muscle and fish gill samples. The highest concentration of p,p′-DDE (0.032 mg/kg ww) was determined in the gill of common carp, which was found to be below the maximum residue limit (MRL). Only sulfadimethoxine was detected among antibiotics in biota samples. Its maximum concentration (0.0044 mg/kg ww) did not exceed the MRL of 0.1 mg/kg. Sulfadimethoxine was found only in muscle and gill of common carp collected from site S6, where there are many rainbow trout cage farms. However, no detectable residue of sulfadimethoxine was found in farmed rainbow trout. The highest concentrations of As, Cd and Pb were detected in mussels, while the highest concentrations Cu and Zn were determined in crayfish. Metal concentrations in biota samples did not exceed the maximum permissible levels. According to these results, the consumption of biota samples from the Keban Dam Reservoir is safe for human health.

A water quality management strategy for regionally protected water through health risk assessment and spatial distribution of heavy metal pollution in 3 marine reserves

Severe water pollution and resource scarcity is a major problem in China, where it is necessary to establish water quality-oriented monitoring and intelligent watershed management. In this study, an effective watershed management method is explored, in which water quality is first assessed using the heavy metal pollution index and the human health risk index, and then by classifying the pollution and management grade based on cluster analysis and GIS visualization. Three marine reserves in Tianjin were selected and analyzed, namely the Tianjin Ancient Coastal Wetland National Nature Reserve (Qilihai Natural Reserve), the Tianjin DaShentang Oyster Reef National Marine Special Reserve (DaShentang Reserve), and the Tianjin Coastal Wetland National Marine Special Reserve (BinHai Wetland Reserve) which is under construction. The water quality and potential human health risks of 5 heavy metals (Pb, As, Cd, Hg, Cr) in the three reserves were assessed using the Nemerow index and USEPA methods. Moreover, ArcGIS10.2 software was used to visualize the heavy metal index and display their spatial distribution. Cluster analysis enabled classification of the heavy metals into 4 categories, which allowed for identification of the heavy metals whose pollution index and health risks were highest, and, thus, whose control in the reserve is a priority. Results indicate that heavy metal pollution exists in the Qilihai Natural Reserve and in the north and east of the DaShentang Reserve; furthermore, human health risks exist in the Qilihai Natural Reserve and in the BinHai Wetland Reserve. In each reserve, the main factor influencing the pollution and health risk were high concentrations of As and Pb that exceed the corresponding standards. Measures must be adopted to control and remediate the pollutants. Furthermore, to protect the marine reserves, management policies must be implemented to improve water quality, which is an urgent task for both local and national governments.

Arsenic enrichment in groundwater in southern flood plain of Ganga-Son interfluves

Arsenic contamination is extensively present in the Holocene alluvial aquifer of middle plain of Ganga. Arsenic concentration in most of the public supply networks exceeds the maximum allowable limit of 50 μg/l (BIS 2003) for drinking water. The primary purpose of this work is to find out the hydrochemical characteristic of groundwater and identify the process of controlling the arsenic contamination and possible relationship among arsenic and other elements through factor analysis. High concentrations of As, Fe and NO3 are responsible due to the redox process and anthropogenic activity. The depth profile of As shows that As depleted with depth and concentration of NO3 is low associated with higher As. Piper Trilinear diagram shows hydrochemical facies categorize into three groups: (a) Ca–HCO3, (b) Na–Ca–HCO3 and (c) Na–HCO3. Dominance of Ca–HCO3 over SO4 + Cl indicates that high recharge phenomena is operated in groundwater sample of study area. According to the Eh-pH diagram, Arsenate (V) and Arsenite (III) are both type of species present in groundwater sample. The poor relationship between As and Fe indicates that, process of releasing As in groundwater are reduction of arseniferous iron hydroxide coupled to precipitation of Fe as FeCO3 when anoxic conditions develop during microbial oxidation of sedimentary organic matter. Multivariate statistical analysis reveals the relationship between different elements. Correlation matrix suggested that strong positive pair association between As–pH, NO3–Cl and Na–Cl etc. are responsible due to carbonate and silicate weathering with some anthropogenic activity. The present study shows that the As concentration in groundwater sample in the study area does not only make alarm but also calls for the immediate action.

Profiles and Risk Assessment of Heavy Metals in Great Rift Lakes, Kenya

Heavy metal pollution in surface water of four lakes (Naivasha, Elementaita, Nakuru, and Bogoria) of the Great Rift Valley in Kenya, East Africa was investigated in this study. Eight heavy metals including chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), lead (Pb), cadmium (Cd), and mercury (Hg) were determined using inductively coupled plasma‐mass spectrometer (ICP‐MS). Among the tested heavy metals, Cd and Hg were detected in all surface water samples. The concentrations of Cr, Cd, Ni, and Pb were relatively lower than those of other metals in the four lakes. Results of Kohonen self‐organizing map indicated that all the sampling sites in four lakes of the Great Rift Valley in Kenya could be classified into three different groups based on the heavy metal pollution. Lake Naivasha and Nakuru had characteristics of low concentrations of Cr, Ni, Cu, As, and Hg. Lake Bogoria was characterized by high levels of Ni, Cu, Cd, and Hg, and low levels of Pb, Cr, Zn, and As. Lake Elementaita showed characteristics of high concentrations of As and Hg and low concentrations of Pb, Ni, Cu, and Cd. Source identification using principal component analysis (PCA) indicated that anthropogenic factor played an increasingly important role in the heavy metal pollution of four lakes of the Great Rift Valley in Kenya, East Africa. Analysis of non‐carcinogenic health risks of heavy metals indicated Hg and As in Lake Elementaita and Hg in Lake Bogoria may pose adverse health effects to local residents via ingestion route.

Arsenic uptake, accumulation and toxicity in rice plants: Possible remedies for its detoxification: A review.

Arsenic (As) is a toxic metalloid. Serious concerns have been raised in literature owing to its potential toxicity towards living beings. The metalloid causes various water- and food-borne diseases. Among food crops, rice contains the highest concentrations of As. Consuming As-contaminated rice results in serious health issues. Arsenic concentration in rice is governed by various factors in the rhizosphere such as availability and concentration of various mineral nutrients (iron, phosphate, sulfur and silicon) in soil solution, soil oxidation/reduction status, inter-conversion between organic and inorganic As compounds. Agronomic and civil engineering methods can be adopted to decrease As accumulation in rice. Agronomic methods such as improving soil porosity/aeration by irrigation management or creating the conditions favorable for As-precipitate formation, and decreasing As uptake and translocation by adding a inorganic nutrients that compete with As are easy and cost effective techniques at field scale. This review focuses on the factors regulating and competing As in soil-plant system and As accumulation in rice grains. Therefore, it is suggested that judicious use of water, management of soil, antagonistic effects of various inorganic plant-nutrients to As should be considered in rice cultivated areas to mitigate the building up of As in human food chain and with minimum negative impact to the environment.

Pioneer Mediterranean Shrub Species Revegetating Soils Developed on Mining Soils/Spoils

AbstractSpontaneous and autochthonous species of plants growing on degraded and contaminated soils/spoils that survive in such environments show, in general, no symptoms of toxicity. This study compares concentrations of chemical elements in different leaves maturation and in different seasons of several native species in a massive sulphide in an abandoned mine area. The objective is to evaluate if these species can play an important role on the stabilization of degraded soils and mine spoils. Total concentrations of chemical elements were great in soils. However, in general, only &lt;1% of the total concentration was extracted by DTPA or ammonium acetate solutions. Total and available fraction of the chemical elements has similar behaviour between soil sites. Mature leaves have higher concentrations of As, Cu, Fe, Mn, Pb and Zn than younger ones. An opposite behaviour occurs with S. Winter and spring variations in most chemical elements concentrations in the plant leaves are not significantly different, except for As. Elemental concentrations of plant leaves are independent of the same elements concentrations (total and available fraction) in soils where plants have grown. The concentrations of As, Cu and Pb in plant leaves were below the level of risk to be ingested by grazing animals, although soils are above the reported thresholds. Therefore, all studied plant species can be considered for phytostabilization programmes, but the use of the land for pasture may not be a solution considering that animals ingest soil along with herbage. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Evaluation of remediation techniques in soils affected by residual contamination with heavy metals and arsenic

Residual soil pollution from the Aznalcóllar mine spill is still a problem in some parts of the affected area, today converted in the Guadiamar Green Corridor. Dispersed spots of polluted soils, identified by the absence of vegetation, are characterized by soil acid pH and high concentrations of As, Pb, Cu and Zn. Ex situ remediation techniques were performed with unrecovered soil samples. Landfarming, Composting and Biopiles techniques were tested in order to immobilize pollutants, to improve soil properties and to promote vegetation recovery. The effectiveness of these techniques was assessed by toxicity bioassays: Lactuca sativa L. root elongation test, Vibrio fischeri bioluminescence reduction test, soil induced respiration test, and Eisenia andrei survival and metal bioaccumulation tests. Landfarming and Composting were not effective techniques, mainly due to the poor improvement of soil properties which maintained high soluble concentrations of Zn and Cu after treatments. Biopile technique, using adjacent recovered soils in the area, was the most effective action in the reduction of soil toxicity; the improvement of soil properties and the reduction in pollutants solubility were key to improve the response of the tested organisms. Therefore, the mixture of recovered soils with polluted soils in the areas affected by residual contamination is considered a more suitable technique to reduce the residual pollution and to promote the complete soil recovery in the Guadiamar Green Corridor.

Trace elements in native and transplanted Fontinalis antipyretica and Platyhypnidium riparioides from rivers polluted by uranium mining

The past uranium/polymetallic mining activities in the Sudety (SW Poland) left abandoned mines, pits, and dumps of waste rocks with trace elements and radionuclides which may erode or leach out and create a potential risk for the aquatic ecosystem, among others. In the present work four rivers affected by effluents from such mines were selected to evaluate the application of aquatic mosses for the bioindication of 56 elements. Naturally growing F. antipyretica and P. riparioides were compared with transplanted samples of the same species. The results demonstrate serious pollution of the examined rivers, especially with As, Ba, Fe, Mn, Pb, Ti, U and Zn, reaching extremely high concentrations in native moss samples. In the most polluted rivers native F. antipyretica and P. riparioides samples showed significantly higher concentrations of As, Ba, Cu, Fe, La, Nd, Ni, Pb, U and Zn than corresponding transplanted samples, whereas at less polluted sites a reverse situation was sometimes observed. Transplanted moss moved from clean to extremely polluted rivers probably protects itself against the accumulation of toxic elements by reducing their uptake. Selection of native or transplanted F. antipyretica and P. riparioides depended on the pollution load.

Assessment of heavy metal contamination zones of biota of Western Uttar Pradesh Terrain, India using atomic absorption spectroscopy

In the present work, heavy metal contamination of water and soil in western Uttar Pradesh terrain, India was assessed. About 16 boreholes and tap water samples and ten soil samples were studied using atomic absorption spectrophotometer (AAS) for arsenic (As) and lead (Pb) content, and the levels were compared with World Health Organization (WHO) specified maximum contaminant level (MCL). According to WHO, the MCL for As and Pb is 0.01 mg/L. From the results obtained, about 75% of biota samples analysed contained As and Pb in concentrations above MCL. The subject of health concern is the increasing concentration of As in Modinagar and Meerut residential area. The effluents from industries, pesticides used in agriculture land and improper waste management are the reasons responsible for heavy metal toxicity in this belt. The deep bore water samples of Muradnagar, Modinagar, Meerut and Mawana showed high concentrations of As.

Assessment of heavy metal contamination zones of biota of Western Uttar Pradesh Terrain, India using atomic absorption spectroscopy

In the present work, heavy metal contamination of water and soil in western Uttar Pradesh terrain, India was assessed. About 16 boreholes and tap water samples and ten soil samples were studied using atomic absorption spectrophotometer (AAS) for arsenic (As) and lead (Pb) content, and the levels were compared with World Health Organization (WHO) specified maximum contaminant level (MCL). According to WHO, the MCL for As and Pb is 0.01 mg/L. From the results obtained, about 75% of biota samples analysed contained As and Pb in concentrations above MCL. The subject of health concern is the increasing concentration of As in Modinagar and Meerut residential area. The effluents from industries, pesticides used in agriculture land and improper waste management are the reasons responsible for heavy metal toxicity in this belt. The deep bore water samples of Muradnagar, Modinagar, Meerut and Mawana showed high concentrations of As.

Tissue Localization and Distribution of As and Al in the Halophyte Tamarix gallica under Controlled Conditions

Information on localization of Al and As in Tamarix gallica is required in order to better understand the detoxification mechanisms that confer tolerance in this halophyte plant species. Plants were subjected to different Al and As concentrations with and without salt supplementation. High concentrations of As and Al have been found in Tamarix gallica leaves and roots without symptoms of toxicity to the plant, which may be related to the particular compartmentation. A sequential extraction was carried out on leaves and roots to determine and compare the metal compartmentation in the plant. In this study, subcellular localization of As and Al was determined for the first time in roots and leaves of T. gallica, and provided evidence of the detoxification mechanisms of high As and Al concentrations. These results suggest that the subcellular distribution of As and Al play important roles in avoidance of metal toxicity. The most part of Al (that has high toxicity to the plant when available forms are present) was immobilized in cell walls, potentially suppressing its transportation to other subcellular compartments more susceptible to Al toxicity. On the other hand, the greater sequestration of As in the vacuole reduces its toxicity to the remaining cell organelles in the roots, but cell wall confinement remains an important tolerant mechanism in the leaves.

Actively forming Kuroko-type volcanic-hosted massive sulfide (VHMS) mineralization at Iheya North, Okinawa Trough, Japan

Modern seafloor hydrothermal systems provide important insights into the formation and discovery of ancient volcanic-hosted massive sulfide (VHMS) deposits. In 2010, Integrated Ocean Drilling Program (IODP) Expedition 331 drilled five sites in the Iheya North hydrothermal field in the middle Okinawa Trough back-arc basin, Japan. Hydrothermal alteration and sulfide mineralization is hosted in a geologically complex, mixed sequence of coarse pumiceous volcaniclastic and fine hemipelagic sediments, overlying a dacitic to rhyolitic volcanic substrate. At site C0016, located adjacent to the foot of the actively venting North Big Chimney massive sulfide mound, massive sphalerite-(pyrite-chalcopyrite±galena)-rich sulfides were intersected (to 30.2% Zn, 12.3% Pb, 2.68% Cu, 33.1ppm Ag and 0.07ppm Au) that strongly resemble the black ore of the Miocene-age Kuroko deposits of Japan. Sulfide mineralization shows clear evidence of formation through a combination of surface detrital and subsurface chemical processes, with at least some sphalerite precipitating into void space in the rock. Volcanic rocks beneath massive sulfides exhibit quartz-muscovite/illite and quartz-Mg-chlorite alteration reminiscent of VHMS proximal footwall alteration associated with Kuroko-type deposits, characterized by increasing MgO, Fe/Zn and Cu/Zn with depth. Recovered felsic footwall rocks are of FII to FIII affinity with well-developed negative Eu anomalies, consistent with VHMS-hosting felsic rocks in Phanerozoic ensialic arc/back-arc settings worldwide.Site C0013, ∼100m east of North Big Chimney, represents a likely location of recent high temperature discharge, preserved as surficial coarse-grained sulfidic sediments (43.2% Zn, 4.4% Pb, 5.4% Cu, 42ppm Ag and 0.02ppm Au) containing high concentrations of As, Cd, Mo, Sb, and W. Near surface hydrothermal alteration is dominated by kaolinite and muscovite with locally abundant native sulfur, indicative of acidic hydrothermal fluids. Alteration grades to Mg-chlorite dominated assemblages at depths of >5mbsf (metres below sea floor). Late coarse-grained anhydrite veining overprints earlier alteration and is interpreted to have precipitated from down welling seawater as hydrothermal activity waned. At site C0014, ∼350m farther east, hydrothermal assemblages are characterized by illite/montmorillonite, with Mg-chlorite present at depths below ∼30mbsf. Recovered lithologies from distal, recharge site C0017 are unaltered, with low MgO, Fe2O3 and base metal concentrations.Mineralization and alteration assemblages are consistent with the Iheya North system representing a modern analogue for Kuroko-type VHMS mineralization. Fluid flow is focussed laterally along pumiceous volcaniclastic strata (compartmentalized between impermeable hemipelagic sediments), and vertically along faults. The abundance of Fe-poor sphalerite and Mg-rich chlorite (clinochlore/penninite) is consistent with the lower Fe budget, temperature and higher oxidation state of felsic volcanic-hosted hydrothermal systems worldwide compared to Mid Ocean Ridge black smoker systems.

Seasonal Variations and Sources of 17 Aerosol Metal Elements in Suburban Nanjing, China

In this work, the seasonal variations and sources of trace metal elements in atmospheric fine aerosols (PM2.5) were investigated for a year-long field campaign from July 2012 to June 2013, conducted in suburban Nanjing, eastern China, at a site adjacent to an industry zone. The PM2.5 samples collected across four seasons were analyzed for 17 metal elements, namely, Sodium (Na), Magnesium (Mg), Aluminum (Al), Vanadium (V), Chromium (Cr), Manganese (Mn), Nickel (Ni), Copper (Cu), Zinc (Zn), Arsenic (As), Selenium (Se), Strontium (Sr), Cadmium (Cd), Barium (Ba), Lead (Pb), Molybdenum (Mo), and Antimony (Sb) using an inductively coupled plasma mass spectrometry (ICP-MS). We found that the total concentration of all 17 metal elements was 1.23 μg/m3, on average accounting for 1.0% of the total PM2.5 mass. For our data, mass concentrations of Al, Cd, Ba were highest in summer, Mg, Cu, Zn, Se, Pb peaked in autumn, Cr, Mn, Ni, As, Sr, Sb increased significantly in winter, while the concentrations of Na, V, Mo were at their highest levels in spring. Air mass back trajectory analysis suggested that air parcels that arrived at the site originated from four dominant regions (Japan, yellow sea and bohai; Southeast of China, the Pacific Ocean; Southwest of Jiangsu and Anhui province; Northern Asia inland and Mongolia region), in particular, the one from Northern Asia inland and Mongolia contained the highest concentrations of As, Sb, Sr, and was predominant in winter. Positive matrix factorization (PMF) analyses revealed that the industrial emission is the largest contributor (34%) of the observed metal elements, followed by traffic (25%), soil dust (19%), coal combustion (10%), incineration of electronic waste (9%), and a minor unknown source (3%). In addition, we have also investigated the morphology and composition of particles by using the scanning electron microscopy (SEM)/energy-dispersive spectrometry (EDS) techniques, and identified particles from coal burning sources, etc., similar to the PMF results.

Trace element and sulfur isotopic evidence for redox changes during formation of the Wallaby Gold Deposit, Western Australia

Wallaby is a major gold deposit of the St Ives Gold field of Western Australia, with an estimated resource of 8 million ounces of gold. It has a well-established paragenesis across five vein sets that displays macroscopic evidence of changing redox through time; from hematite to magnetite. Micro-analysis of pyrite from each vein generation shows a progressive and gradual change in redox conditions. The sulfur isotope composition has a δ34S range of −7.7 to +9.8‰ using 3μm spots on the Sensitive High Resolution Iron Micro Probe-Stable Isotope (SHRIMP-SI). Negative values indicative of an oxidized sulfur signature are found in the earliest generation of pyrite (which coexists with hematite) that also contains high concentrations of As, Ni, Zn, Ag, Sb, Cu and Pb. Conversely, positive values representative of reduced sulfur are found in later generations of pyrite, with lower concentrations of As, Ni, Sb, Cu, Zn and Pb. These later pyrite crystals display higher As/Ni, As/Sb, and As/Bi, and lower Cu/Te. These geochemical trends are the result of redox controlled transport and partitioning into pyrite of minor and trace elements now within the pyrite structure. Previous studies suggested a single orogenic event formed the Wallaby Deposit. This is not supported by the present study. Trace element ratios such as As/Ni clearly delineate the high Au generations and could be used as an exploration tool. It is suggested that pyrite from the Wallaby Gold Deposit formed via desulfidation and a gradual change in redox conditions within an evolving fluid and did not result from mixing of two separate fluids as previously advocated. Utilizing pyrite to link the entire fluid history of Wallaby demonstrates the general use of pyrite as a valuable mineral tracer in gold-bearing fluid systems.

Isotopic evidence of nitrogen sources and nitrogen transformation in arsenic-contaminated groundwater

High concentrations of naturally occurring arsenic (As) are typically found in young alluvial and deltaic deposits, and high concentrations of ammonium (NH4+) and nitrate (NO3−) are often present in groundwater affected by anthropogenic activities. In this study, on the basis of physicochemical characteristics of groundwater and the nitrogen and oxygen isotope composition of NO3−, it was inferred that the main sources of NO3− in the proximal fan of the Choushui River alluvial fan are likely to be ammonium fertilizers, manure, and septic waste; that in the mid-fan and the distal fan, the possible sources are nitrate fertilizers and marine nitrate. In the proximal fan, the oxidative state obviously promotes microbial nitrification. Denitrification occurs from the upstream region to the downstream region of the Choushui River, and therefore, the decrease in NO3− concentration along streams connecting the Choushui River to the ocean appears plausible. High DO concentrations and relatively low values of δ18ONO3 in the deeper aquifer of the proximal fan may be attributed to unconfined granular nature and groundwater pumping by agricultural activities. In the mid-fan, NO3− assimilation is the dominant response to NO3− attenuation, and denitrification is insignificant; however, high concentrations of As, NH4+ and Fe and depletion of δ15NNO3 imply the occurrence of feammox process. By contrast, denitrification evidently occurs in the distal fan, through assimilation, mineralization, and dissimilatory NO3− reduction to NH4+, resulting in depletion of NO3− and increase in NH4+ in groundwater. Feammox in the mid-fan and denitrification in the distal fan may be the main processes leading to the release of As from As-bearing Fe oxyhydroxides into groundwater.