Presence Of As Research Articles

Segregation and Fractionation of Magmatic Ni-Cu-PGE Sulfides in the Western Jinchuan Intrusion, Northwestern China: Insights from Platinum Group Element Geochemistry

The Jinchuan Ni-Cu-(PGE) deposit is one of the world’s largest magmatic sulfide deposits. Recent studies have suggested that the Jinchuan intrusion originally comprised two individual intrusions, the Eastern and the Western intrusions. The Western intrusion consists of an Upper and a Lower unit. The Upper unit is largely free of sulfides with weakly disseminated sulfides only at the base of the unit; these sulfides are characterized by moderate Cu/Pd ratios of 5,500 to 14,900 and relatively high PGE tenors (PGE in 100% sulfides) in the range of 510 to 1,000 ppb Irsul, 420 to 1,200 ppb Rusul, and 2,900 to 8,000 ppb Pdsul. Disseminated, net-textured and minor massive sulfides in the Lower unit comprise the No. 24 orebody, the third largest at Jinchuan. The disseminated ores have remarkably high Cu/Pd ratios (24,200–85,600) and low PGE tenors in the range of 120 to 560 ppb Irsul, 100 to 480 ppb Rusul, and 430 to 3,600 ppb Pdsul. The net-textured and massive ores contain high IPGE contents (240–820 ppb Irsul and 170–630 ppb Rusul) and Ni/Cu ratios (1.7–11.3), low Pd/Ru ratios (0.53–3.1), and exhibit significant Pt depletion (<300 ppb Ptsul). Additionally, small Cu-rich orebodies occur at the base of the No. 24 orebody or in small intrusions within footwall schists, marbles, and granites beneath the Western intrusion. The Cu-rich sulfides have very low IPGE tenors (1.9–16 ppb Irsul and 6.4–21 ppb Rusul), and Ni/Cu ratios (0.3–2.8), high Pd/Ru ratios (37.3–378), and highly variable Ptsul between 43 and 11,000 ppb. The PGE geochemistry and model calculations indicate that the disseminated sulfides of the Upper and Lower units segregated from PGE-undepleted and -depleted parental magmas, respectively. The PGE-depleted magma had undergone a minor amount of earlier sulfide liquid extraction at depth. Furthermore, this PGE-depleted parental magma had slightly higher PGE contents than the magma from which the sulfides of the Nos. 1 and 2 orebodies in the Eastern intrusion segregated. The significant variations in base and precious metal ratios of the net-textured and massive sulfide ores are attributed to fractionation of the sulfide melts that formed these ores. This led to both migration of the residual Cu-rich sulfide melts away from the early-formed monosulfide solid solution (mss) to form Cu-rich ores as well as back intrusion of the Cu-rich ores into the mss. The negative Pt anomalies of the net-textured and massive sulfides resulted from preferential extraction of Pt into the Cu-rich residual melts due to the presence of As, Te, and Bi.

The effect of silicon on the uptake and translocation of arsenic in tomato (Solanum lycopersicum L.)

Measuring tomato seed germination on a medium containing either arsenite or arsenate showed that the presence of 0.5mM NaH2AsO4·7H2O reduced germination by between 20% and 40%, depending on cultivar. The inhibitory effect was mitigated by the addition of CaSiO3. However, the presence of both forms of As had a drastic negative effect on seedling shoot elongation, which was not mitigated by the presence of CaSiO3. In a subsequent soil-based pot trial, damage due to the presence of As was visible by 15 days after the initiation of the treatment, and the provision of CaSiO3 was significantly ameliorative; again, the severity of the effects was cultivar-dependent. Analysis of the accumulation and distribution of As showed that some of the cultivars are As excluders, and others accumulators. As was taken up by the latter cultivars whether or not CaSiO3 supplementation was provided. The extent of As entry into the fruit varied from cultivar to cultivar, but never rose above the safety threshold. A survey of stress response-associated genes showed that LeGR was strongly up-regulated by exposure to As.

DFT simulation of the occurrences and correlation of gold and arsenic in pyrite

Using density functional theory (DFT) calculations, the occurrences and correlation of gold (Au) and arsenic (As) in pyrite were studied, and the effect of As on the structural stability of Au in pyrite (FeS2) was investigated. The calculated results show that Fe is not likely to be simply substituted with Au under normal circumstances. The presence of As is very conducive to incorporating Au into the pyrite interstitial lattice site along with substitution for the S site. It is predicted that a positive correlation exists between Au and As in pyrite and that higher As concentration facilitates the incorporation of Au in pyrite. Additionally, with increasing As content, Au sits on the Fe site and the Fe is repelled into the hole. The pyrite lattice expands with the incorporation of Au and As. Antibonding interactions are found between the Au, Fe, and As atoms. The reducibility of pyrite is greatly enhanced due to the presence of Au and As. The electronic structure calculations show that substituting Au and As for S atoms does not change the pyrite p-type property and that defect energy levels are present in the conduction band. However, with increasing As concentration, incorporating the interstitial site of Au causes a change from the p-type pyrite to an n-type pyrite, and defect energy levels are mainly located in the energy band gap. The interstitial site of Au causes the pyrite to be spin-polarized at a certain As content. In addition, strong interactions are found between Fe 3d and Au 6p orbitals and between Au 5d and As 4p orbitals.

Cytosolic phospholipase A2α upregulation mediates apoptotic neuronal death induced by aggregated amyloid-β peptide1–42

Increased cytosolic phospholipase A2α (cPLA2α) immunoreactivity and transcript were observed in Alzheimer’s disease (AD) brain associated with amyloid deposits. Thus, the present study examined whether cPLA2α upregulation participate in cortical neuron damage induced by aggregated Aβ1–42 and determined its role in the signaling events leading to damage, using an antisense technology. Exposure of primary cortical neurons to 1μM aggregated Aβ1–42 for 24h induced up-regulation and activation of cPLA2α and apoptotic cell death of about 30% as detected by: cell count, MTT reduction, caspases-3 and -8 activation, DAPI and TUNEL staining, that were prevented by inhibition of cPLA2α up-regulation and activity in the presence of antisense against cPLA2α (AS). cPLA2α was rapidly activated upon addition of aggregated Aβ1–42, as determined by its phosphorylated form on serine 505, and this activity was dependent on NADPH oxidase activity. NOX2- and NOX4-NADPH oxidase upregulation at 24h of aggregated Aβ1–42 exposure was not affected by the presence of AS, but superoxide production was reduced, probably due to NOX2 inhibition. cPLA2α upregulation led to activation of neutral sphingomyelinase (N-SMase) as its activity was inhibited in the presence of AS, and could be restored by addition of arachidonic acid. Addition of ceramide analog induced caspase-8 activation leading to caspase-3 activation and apoptotic neuronal death. In conclusion, our results suggest that cPLA2α activity plays a crucial role in the signaling cascade leading to apoptotic neuronal death by aggregated Aβ1–42 probably via activation of N-SMase, ceramide production and caspases-3 and -8.

The distribution of arsenic in shallow alluvial groundwater under agricultural land in central Portugal: Insights from multivariate geostatistical modeling

In this study multivariate and geostatistical methods are jointly applied to model the spatial and temporal distribution of arsenic (As) concentrations in shallow groundwater as a function of physicochemical, hydrogeological and land use parameters, as well as to assess the related uncertainty. The study site is located in the Mondego River alluvial body in Central Portugal, where maize, rice and some vegetable crops dominate. In a first analysis scatter plots are used, followed by the application of principal component analysis to two different data matrices, of 112 and 200 samples, with the aim of detecting associations between As levels and other quantitative parameters. In the following phase explanatory models of As are created through factorial regression based on correspondence analysis, integrating both quantitative and qualitative parameters. Finally, these are combined with indicator-geostatistical techniques to create maps indicating the predicted probability of As concentrations in groundwater exceeding the current global drinking water guideline of 10μg/l. These maps further allow assessing the uncertainty and representativeness of the monitoring network. A clear effect of the redox state on the presence of As is observed, and together with significant correlations with dissolved oxygen, nitrate, sulfate, iron, manganese and alkalinity, points towards the reductive dissolution of Fe (hydr)oxides as the essential mechanism of As release. The association of high As values with rice crop, known to promote reduced environments due to ponding, further corroborates this hypothesis. An additional source of As from fertilizers cannot be excluded, as the correlation with As is higher where rice is associated with vegetables, normally associated with higher fertilization rates. The best explanatory model of As occurrence integrates the parameters season, crop type, well and water depth, nitrate and Eh, though a model without the last two parameters also gives quite satisfactory results.

Chemical characterization and source identification of particulate matter PM10 in a rural and urban site in Poland

The measurements of PM10 at two sites in Poland – a typical village and a big city considered urban background – indicated only a small difference in PM10 concentrations. In summer time, the concentrations of PM10 did not exceed the daily limit value of 50 μg/m while in wintertime, the daily limit value was exceeded for almost all sampling days for both sites. Source contributions to ambient PM10 were determined with factor analysis (FA) and multilinear regression analysis (MLRA) based on PM10 composition data including concentrations of K, Ca, Ti, Cr, Mn, Fe, Cu, Zn, Br, Pb and As. In the winter, local combustion sources contributed with 61% and 79% to total mass in the urban and rural sites, respectively, reflecting serious local or even regional problem associated with PM10 pollution. The episodic presence of As, the commonly known toxic element, requires a detailed study for better understanding of its temporal distribution both in the rural and urban atmosphere.

Chemical characterization and source identification of particulate matter PM10 in a rural and urban site in Poland

The measurements of PM10 at two sites in Poland – a typical village and a big city considered urban background – indicated only a small difference in PM10 concentrations. In summer time, the concentrations of PM10 did not exceed the daily limit value of 50 μg/m while in wintertime, the daily limit value was exceeded for almost all sampling days for both sites. Source contributions to ambient PM10 were determined with factor analysis (FA) and multilinear regression analysis (MLRA) based on PM10 composition data including concentrations of K, Ca, Ti, Cr, Mn, Fe, Cu, Zn, Br, Pb and As. In the winter, local combustion sources contributed with 61% and 79% to total mass in the urban and rural sites, respectively, reflecting serious local or even regional problem associated with PM10 pollution. The episodic presence of As, the commonly known toxic element, requires a detailed study for better understanding of its temporal distribution both in the rural and urban atmosphere.

Arsenic effect on the model crop symbiosis Bradyrhizobium–soybean

Soybean (Glycine max) is often being cultivated in soils with moderate to high arsenic (As) concentrations or under irrigation with As contaminated groundwater. The purpose of this study was to determine the effect of As on soybean germination, development and nodulation in soybean-Bradyrhizobium japonicum E109 symbiosis, as a first-step approach to evaluate the impact of As on soybean production. Semi-hydroponic assays were conducted using soybean seedlings inoculated and non-inoculated with B.japonicum E109 and treated with arsenate or arsenite. Soybean germination and development, at early stage of growth, were significantly reduced from 10μM arsenate or arsenite. This also was seen for soybean seedlings inoculated with B.japonicum mainly with arsenite where, in addition, the number of effective nodules was reduced, despite that the microorganism tolerated the metalloid. This minor nodulation could be due to a reduced motility (swarming and swimming) of the microorganism in presence of As. Arsenic concentration in roots was about 250-times higher than in shoots. Transference coefficient values indicated that As translocation to aerial parts was low and As accumulated mainly in roots, without significant differences between inoculated and non-inoculated plants. The presence of As restricted soybean-B. japonicum symbiosis and hence, the efficiency of most used commercial inoculants for soybean. Thus, water and/or soils containing As would negatively impact on soybean production, even in plants inoculated with B.japonicum E109.

Lead in Ancient Peru: the Curamba Smelter and Lead Sling Bullets

Since the 16th century, the Inca site of Curamba, in southern Peru, has been interpreted as a metallurgical center for processing silver ore. Yet, aside from the many shallow pits, interpreted as hornos for smelting silver, there was no physical evidence for the use of huayras or tocochimbos, which were the structures traditionally used for precontact silver smelting in the ancient Andes. Geochemical analyses (inductively coupled plasma) of scoria excavated from the hornos at Curamba indicate low Ag (<0.3 ppm to 0.4 ppm), Au (<2 ppm), and Cu (18 ppm to 31 ppm) contents, whereas Pb (155 ppm to 234 ppm) and Zn (125 ppm to 259 ppm) contents were high. This suggests that nonargentiferous galena (PbS) was smelted to obtain lead. A lead-zinc signature is also indicated by the presence of As, Ba, Fe, Mn, and V, yet no ore minerals such as PbS or sphalerite [(Zn,Fe)S] have been found at the site. Several precontact lead artifacts from ancient Peru have been described as bars (lingotes) or weights (pesos). However, alternatively, these artifacts might be more accurately described as: (a) biconic to ovoid (30 mm to 60 mm, 30 g to 40 g) or (b) spherical (35 mm, 80 g to 160 g); therefore, in composition, dimensions, form, and weight, these ancient Peruvian lead artifacts from the north coast are strikingly similar to ancient Roman and Celtic lead sling ammunition from first-century BC battle sites, and are herein interpreted to have served a similar function in ancient Andean warfare.

Influence of pH and Oxidation State on the Interaction of Arsenic with Struvite During Mineral Formation

Struvite (MgNH(4)PO(4)·6H(2)O) precipitated from animal and human wastes may be a sustainable source of fertilizer. However, arsenic, present in some wastes, may be removed with struvite. Here the sorption of As with struvite during mineral formation at pH 8-11 was assessed. The yield of struvite increased with pH, and was highest at pH 10. For recovered struvite, XRD indicated reduced crystallinity and particle size, and FT-IR suggested less distortion of phosphate tetrahedra with increased pH. The As impurity did not affect the crystallinity or particle size, but did contribute to phosphate distortion. Sorption of As(V) was observed at all pH values, and was highest at pH 10. As(III) sorption was consistently lower than that of As(V), but increased with pH. XAFS suggested coprecipitation of As(V), and adsorption of As(III) as the potential sorption mechanisms. Solids derived from As(III) solutions exhibited dual mechanisms due to the partial oxidation of As(III) to As(V) in solution prior to sorption. For struvite recovery in the presence of As, optimizing the pH to improve yields may increase the As content. Adsorbed As(III) could be removed prior to fertilizer application, however coprecipitated As(V) will release upon mineral decomposition, linking its cycling to that of phosphorus.

Elemental characterization of some Nigerian gemstones: tourmaline, fluorite and topaz by instrumental neutron activation analysis

Instrumental neutron activation analysis (INAA) was employed in the determination of the major and trace element constituents in tourmaline, fluorite and topaz collected from the gemstone mineralization within a SW–NE trending pegmatite zone, central Nigeria. Cost, turnaround time, high sensitivity for certain elements, the non-destructive nature of analysis and its precision and accuracy have combined to make INAA an indispensable method for multi-element determination in virtually all geological matrices. The major element constituents in tourmaline were Al (119,800 ppm), Mn (4,348 ppm), Na (15,540 ppm) and Fe (34,290 ppm). For fluorite, Ca was the major element with a concentration of 552,000 ppm. In topaz, Al was the major constituent with a concentration of 322,800 ppm. The data suites reveal the presence of As, Br, La, Sc, Co, Hf, Ta and Sb in tourmaline, Na, As, Br, La, Yb, Co, Zn, Eu, Hf, Th in fluorite and Mg, Mn, Na, Br, La, Sc, Co and Ta as trace contaminants. No attempt was made to identify the molecular structure of the gemstones as oxygen, fluorine and silicon contents in any of them were not determined.

Assessment of concentrations of toxic elements in aquaculture food products in Malaysia

Abstract Thirteen species of aquaculture food products, including fresh water and marine fish, prawns, and seaweed were collected from 37 aquaculture farms in Malaysia. Muscle and liver specimens from these species were tested for the presence of As, Cd, Cr, Cu, Hg, Pb, and Zn by using a heat vaporisation atomic absorption spectrophotometer and an inductively coupled plasma atomic emission spectrophotometer. Sea bass from each collected site were comparatively studied, where As concentrations were assumed to be caused by different culture system; and, Hg and Pb concentration were assumed to be due to anthropogenic activities in specific sites. The calculated estimated intake values of Malaysians for total As, Cd, Cr, Cu, Hg, Pb, and Zn in the muscle of the examined species were 3.713, 0.115, 0.113, 4.268, 0.211, 0.738 and 15.863 μg/kg b.w./day. None of the values exceeded the JECFA guideline values and would pose no health hazards for consumers.

Effects of genetic polymorphisms of programmed cell death 1 and its ligands on the development of ankylosing spondylitis

There is a known association of imbalanced peripheral tolerance and autoimmune diseases. The binding of programmed cell death 1 (PD-1) with its ligands 1 and 2 (PD-L1 and PD-L2) inhibits T-cell proliferation through a negative signal via recruitment of src homology 2-domain-containing tyrosine phosphatase 2. Therefore we evaluated the effect of the PD-1, PD-L1 and PD-L2 genotypes on the occurrence of AS in a population of Taiwanese patients. Genetic polymorphisms of PD-1 G-536A, PD-L1 A8923C and PD-L2 C47103T were identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for 330 AS patients and 330 healthy controls who were matched by age and gender. Subjects with the PD-1 GG genotype [matched relative risk (RR(m)) 1.78; 95% CI 1.13, 2.81] and the GA genotype (RR(m) 1.59; 95% CI 1.09, 2.31) had significantly greater risk for AS than those with the AA genotype. Subjects with the PD-L2 CT genotype had lower risk for AS than those with the CC genotype (RR(m) 0.01; 95% CI 0.001, 0.06). Interestingly, the combined genotypes of PD-1 G-536A, PD-L1 A8923C and PD-L2 C47103T also appear to be associated with AS development. Our results suggest that PD-1 G-536A, PD-L1 A8923C and PD-L2 C47103T polymorphisms are associated with the presence of AS.

Toxic Metals (As, Cd, Ni and Pb) and PM2.5 in Air Concentration of a Model Ceramic Cluster

The relationship between ambient concentrations of fine particulate matter and detrimental health effects remains a highly controversial issue. Increased incidence of mortality and morbidity due to cardiopulmonary complications has been associated with elevated levels of urban air particles with an aerodynamic of <2.5 μm (PM2.5). The main aim of this paper was to present the assessment of the temporal and spatial variations of the PM2.5 fraction and its contents in arsenic, cadmium, nickel and lead in order to identify possible emission sources of these pollutants. Daily ambient aerosol samples (PM2.5) were taken in the province of Castellon from 2008 to 2009. Particle concentration levels were determined by gravimetry, and the As, Cd, Ni and Pb levels in the samples were determined by inductively coupled plasma mass spectroscopy. The season variation of these pollutants differs according to the emission source and the factors involved in dispersion. In the weekly trend, there were no significant differences in levels among sampling sites in relation to the day activity (working vs. non-working) due to chemical pollutants that are found in fine particulate fractions residing in the atmosphere longer than coarse particles, resulting in a more homogeneous concentration of pollutants over time. In order to identify similar behaviour between chemical pollutants and PM2.5, an assessment of the correlation between them was carried out. This behaviour study shows whether the source of contaminants is the same. A statistical analysis of the levels of PM2.5 and the presence of As, Cd, Ni and Pb in the different sampling sites was performed in order to evaluate the influence of the sampling point on the concentrations of these pollutants.

Surface typochemistry of hydrothermal pyrite: Electron spectroscopic and scanning probe microscopic data. II. Natural pyrite

Techniques of X-ray photoelectron and Auger electron spectroscopy, scanning probe microscopy were used to demonstrate that the natural surface of hydrothermally synthesized pyrite, as well as vacuum fractures, contain a number of sulfide-sulfur species: disulfide, monosulfide, and, more rarely, polysulfide. The natural surface of hydrothermal pyrite is chemically modified compared to the inner volume into a nonautonomous phase film up to ∼500 nm thick, which has a variable composition resembling that of pyrrhotite but with broader variations toward FeS2. Its principal distinctive feature is the presence of a peak at ∼710 eV in the XPS Fe 2p3/2 spectrum, which is often higher than the main peak of bivalent low-spin Fe(II) in the pyrite structure (707 eV). The “basic” structure of the nonautonomous phase is a layer of variable composition Fe2+[S, S2, Sn]2−, whose S/S2 ratio varies from ∼0.5 to ∼2.0, averaging at ∼1.1. This layer may include admixtures of minor elements, as follows from the appearance of a nonautonomous phase in the presence of As, which does not, however, form an individual phase. The polymerization of S at the surface is thereby more significant. The major oxisulfide components of this phase may be the sulfite and thiosulfate ions at a subordinate concentration of sulfate because of the instability of coexisting sulfate and disulfide ions, which results, in the presence of oxygen, in sulfite (thiosulfate) and sulfide ions in the nonautonomous phase. In line with XPS, scanning probe microscopic (SPM) data show that, at a high S activity in the “pure” system, the surface of the crystals contains practically no nanometer-sized phases and is characterized by low roughness (14–17 nm). At a low S fugacity in equilibrium with pyrrhotite and sphalerite, the average roughness of the surface increases to 25–65 nm, with the maximum height of the surface features of ∼100–500 nm. This is consistent with Auger spectroscopic data, obtained after the etching (ion milling) of the surface with Ar+, on the thickness of the nonstoichiometric surface layer. Comparison with analogous data on other sulfides shows that crystals growing in hydrothermal environments have surface layers up to ∼500 nm thick, which are different from the main volume of the crystal in chemistry, stoichiometry, and, possibly, also structure. This is scale of the surface heterogeneity at which the typochemistry of mineral surfaces may be manifested. The typochemistry of pyrite stems from the ability of the nonautonomous phase to “record” the growth conditions of crystals in terms of two major factors: the purity of the system (the occurrence of other phases, including virtual ones, i.e., potentially possible phases of admixture elements) and S fugacity (which influences the S/S2 ratio at the surface). The geochemical role of the surface nonautonomous phase in pyrite may be very significant, particularly when minor elements are captured that are incompatible with the pyrite structure but can be easily accommodated in the less rigid structure of the nonautonomous phase.

Assessment of elemental pollution in soil of Islamabad city using instrumental neutron activation analysis and atomic absorption spectrometry techniques

The soil samples of nine different sites in Islamabad were studied for their elemental composition. Instrumental neutron activation analysis and atomic absorption spectrometry were employed and 33 elements were determined. The acquired data were analyzed using descriptive statistics, principal component analysis, cluster analysis, pollution level index and enrichment factor. A perusal of results shows a distribution of elemental concentration in two major groups, one along the highway and the other in industrial area of Islamabad. The soil along the highway sites was found to be relatively less polluted than at the sites in the industrial area. The enrichment factor indicates the presence of As, Pb, Sb, Se and Sn at higher levels. The method validation was done by analyzing IAEA reference materials SL-1 (lake sediment) and S7 (soil).

Agrobacterium-mediated genetic transformation of mint with E. coli glutathione synthetase gene

Morphologically identical transgenic mint (Mentha arvensis L.) with bacterial glutathione synthetase gene has been developed. Transformed plants were obtained by co-cultivation of leaf disks with Agrobacterium tumefaciens strain LBA 4404 harbouring a binary vector pCAMBIA-CpGS that carried E. coli glutathione synthetase (GS), β-glucuronidase as reporter gene and nptII as selective marker gene for kanamycin resistance. Using a constitutive double CaMV 35S promoter and an rbcS transit peptide, we successfully addressed CpGS to the chloroplasts through pJIT 117 vector. Preculture and the presence of AS in the co-cultivation medium played a significant role in enhancing transformation frequency. The highest transformation frequency was achieved with MS selection medium supplemented with 25% coconut water, 1.12 mg l−1 BAP, 0.2 mg l−1 NAA, 50 mg l−1 kanamycin and 125 mg l−1 cefotaxime. Robust rooting of regenerated shoots was obtained in half-strength liquid MS medium containing 0.2 mg l−1 NAA and 50 mg l−1 kanamycin. The presence and expression of transgenes in transgenics (T0) was evidenced by GUS histoenzymatic assay, PCR and RT-PCR analysis of nptII and the gene of interest, i.e., GS of putative transgenic leaves. Chromosomal integration of GS gene was confirmed by Southern blot analysis. Transgenic plants were successfully acclimatized in the greenhouse. An overall transformation frequency of 15% was achieved in approximately 3 months of time period. These results are discussed in relation to heavy metal trafficking pathways in higher plants and to the interest of using plastid expression of PCS for biotechnological applications.

Joint effects of arsenic and cadmium on plant growth and metal bioaccumulation: A potential Cd-hyperaccumulator and As-excluder Bidens pilosa L

Joint effects of arsenic (As) and cadmium (Cd) on the growth of Bidens pilosa L. and its uptake and accumulation of As and Cd were investigated using the field pot-culture experiment. The results showed that single Cd (≤25 mg kg −1) and As (≤50 mg kg −1) treatments could promote the growth of B. pilosa, resulting in 34.5–104.4% and 21.0–43.0%, respectively, increase in the dry biomass of shoots while compared with that under the control conditions. However, under the co-contamination of As and Cd, there was an antagonistic effect on the growth of the plant. The concentrations of As and Cd accumulated in tissues of the plant increased with an increase of As and Cd in soils. In particular, the levels of Cd in stems and leaves reached 103.0 and 110.0 mg kg −1, respectively, when soil Cd was 10 mg kg −1. Furthermore, the BF and TF values of Cd were greater than 1.0. However, the highest content of As in roots of the plant was only 13.5 mg kg −1 when soil As was at a high level, i.e. 125 mg kg −1, and the TF values of As were less than 0.1, indicating that B. pilosa can be considered as a potential Cd hyperaccumulator and As excluder. The presence of As had inhibitory effects on Cd absorption by the plant, in particular, the accumulation of Cd in stems, leaves and shoots decreased significantly, with 42.8–53.1, 49.3–66.4 and 37.6–59.5%, respectively, reduction when the level of soil As was up to 125 mg kg −1 compared with that under no addition of As. Whereas, when Cd was added to soils, it could facilitate As accumulation in tissues of the plants and the As concentrations in shoots increased with increasing Cd spiked in soils. The interactive effects of Cd and As may be potential for phytoremediation of Cd and/or As contamination soils.

Significance of urinary arsenic speciation in assessment of seafood ingestion as the main source of organic and inorganic arsenic in a population resident near a coastal area

In order to characterize the different sources of exposure to arsenic (As), urinary excretion of total As, the sum of inorganic As + MMA + DMA determined by the hydride generation-atomic absorption spectrophotometry technique, and the species As 3, As 5, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and arsenobetaine were determined in 49 workers at a steel foundry, with presumed occupational exposure to As, and 50 subjects from the general population, all males. No evidence of occupational exposure to As resulted from environmental monitoring performed in the foundry, although the analysis of minerals used as raw materials showed the presence of As, particularly in fossils and fine ores. The urinary concentrations of As 3, MMA, DMA, the sum of inorganic As + MMA + DMA and total As were not different in the two groups, while arsenobetaine appeared significantly higher in the controls than in the workers. The different species of urinary As were all significantly correlated. Urinary excretion of As 3 was associated with the consumption of mineral water and with residence in an industrial zone, while MMA, DMA, arsenobetaine, the sum of inorganic As + MMA + DMA and total As urinary excretion were associated with the consumption of crustaceans and/or shellfish 3 days or less before urine collection. Multiple regression analysis confirmed these results. In conclusion, in populations with a high consumption of seafood, living in areas characterized by coastal/marine As pollution, only speciation of As can identify a prevalent role of environmental sources, like the consumption of seafood contaminated by As, in determining urinary As excretion, and exclude an occupational origin of the exposure.

Critical Toxicity Level of Arsenic and Elemental Composition of Arsenic-Induced Chlorosis in Hydroponic Sorghum

Physiological and mineralogical responses of sorghum (Sorghum bicolor L. cv. Fast sorghum) in hydroponic culture at elevated concentrations of arsenic (As) were evaluated. Seedlings were grown in the presence of 0, 6.7, 33.5 and 67 µM As levels (0, 0.5, 2.5 and 5 mg As l−1) up to 14 days after treatments (DAT). Shoot and root dry matter yield were repressed by higher As levels. At low As level (6.7 µM) shoot dry matter yield was enhanced by 2.3% but at 33.5 and 67 µM As levels, the yield decreased by 52 and 79%, respectively. The root growth was similarly enhanced (8%) at the lower As level while the growth decrement at the higher As levels were 33 and 68%, respectively for the two treatments. Considering 10% dry weight (DW) reduction, the critical toxicity level of As was calculated to be 11.7 µg g−1 DW for shoot and 367 µg g−1 DW for root, indicating that shoot was more sensitive to As-toxicity than root. A whitish chlorotic symptom was observed in the fully developed young leaves at the 67 µM As level. The lowest chlorophyll content was also observed at this As level. Arsenic concentration increased both in shoot and in root with increase in solution As concentration. The concentrations of As and Fe were about 16, 28 and 17 times; and 2, 25 and 144 times higher in root than shoot at 6.7, 33.5 and 67 µM As levels, respectively. The concentrations of K, Fe and Cu were significantly lower while Ca, Mg and Mn concentrations were higher in the shoot at the 67 µM As level compared to the control plants. On the other hand, Fe, Mn, Zn and Cu concentrations were higher in root at the 67 µM As level. In the shoot, accumulation and translocation of metal micronutrients, particularly that of Fe, decreased significantly because of the presence of As. The present observations suggested that As might induce a toxic effect on sorghum by hampering the translocation of the metal micronutrients. It is suggested that “As-induced Fe-deficiency” caused chlorotic symptoms in the hydroponically grown sorghum.