Total arsenic, lead, cadmium, copper, and zinc in some salt rivers in the northern Andes of Antofagasta, Chile

Lake Velenje is located in one of the most polluted regions in Slovenia, the Salek Valley. The major source of pollution in the valley is the coal-fired thermal power plant in Sostanj (STPP, capacity 775 MW). It has five separate units. All units have electrostatic precipitators for fly ash removal. Unit 4 also has installed a wet flue gas desulfurisation system (FGD system). Total mercury (THg) concentrations were measured in lignite, slag and ash samples from the STPP. In flue gas, different mercury species (THg, MeHg, Hg2+, Hg0) were determined separately for unit 4 and unit 5 which use different flue gas cleaning technology. Mercury and methyl mercury (MeHg) concentrations were also measured in lake water at different depths, in inflow water, outflow water, rain, snow and lake sediments in order to establish the influence of the power plant on the lake. Most mercury emitted from the power plant is in the elemental form. The ratio between oxidised and elemental Hg depends on the flue gas cleaning technology. Mass balance calculations have been performed for the STPP. The results show that the major sources of mercury in Lake Velenje are wet deposition and lake inflows. Total and MeHg concentrations in the water column are very low and can be compared to other non-contaminated freshwater lakes in the world.     

Mobilization of arsenic by dissolved organic matter from iron oxides, soils and sediments

The arsenic contamination of aquifers has been linked to the input of dissolved organic matter (DOM). In light of this suggestion, the aim of this study was to quantify chemical effects of DOM on desorption and redox transformations of arsenic bound to synthetic iron oxide and natural samples from different geochemical environments (soils, shallow aquifer, lake sediment). In batch experiments, solutions containing 25-50 mg/L of two different types of DOM (purified peat humic acid and DOM from a peat drainage) were used as extractants in comparison to inorganic solutions. DOM solution was able to mobilize arsenic from all solid phases. Mobilization from iron oxides (maximum: 53.3%) was larger than from natural samples (maximum: 2.9%). The mobilization effect of extractants decreased in the order HCl>NaH2PO4>DOM>NaNO3. DOM solutions, therefore, mainly targeted weakly sorbed arsenic. Mobilization was complete within 24-36 h and DOM was sorbed during incubation indicating competition for sorption sites. The same patterns were observed for different DOM types and concentrations. Addition of DOM lead to (a) enhanced reduction (maximum 7.8%) and oxidation (6.4%) of arsenic in aqueous solution and (b) the appearance of arsenite in aqueous phase of soil samples (5.5%). As the primary mechanism for the arsenic release from solid phases we identified the competition between arsenic and organic anions for sorption sites, whereas redox reactions were probably of minor importance. The results of this study demonstrate that sorption of DOM has a strong potential to mobilize arsenic from soils and sediments.     

Total arsenic, lead, and cadmium levels in vegetables cultivated at the Andean villages of northern Chile

Various vegetables (broad beans, corn, potato, alfalfa and onion) were sampled in northern Chile, Antofagasta Region. They are the basis of human nutrition in this region and of great relevance to human health. This region is characterized by volcanic events (eruptions, thermal springs, etc.). Most of the vegetables cultivated in this area enter the local markets for a population of approximately 4000 people, whose ancestors were mainly atacame?os and quechuas (local indigenous people). The cadmium and lead in these foods was determined by differential pulse anodic stripping voltammetry (DPASV). Results indicate that the highest concentration of Pb and Cd are in the potato skin, while the edible part of the potatoes contained a lower concentration of these metals. The INAA analyses of As in the vegetables from Socaire and Talabre, two towns located close to active volcanoes (e.g. Lascar), show a very high As content: 1850 microg/kg in corn (Socaire) and 860 microg/kg in potatoes (+ skin) (Talabre). These values exceed the National Standard for arsenic (500 microg/kg) by approximately 400% and 180%, respectively. In general, the data show a concentration of Pb greater than Cd with the potential for some vegetables to accumulate heavy metals, The values, expressed in fresh weight, vary from 0.2 to 40 microg/g for Cd and from 0.6 to 94 microg/g for Pb. These concentration intervals, except that of arsenic, are within the recommended standards in the Food Sanitary Regulation (Decree 977), which, expressed as fresh weight, must be equal to or smaller than 500 microg/kg for Pb. There is no legal standard for Cd.     

Assessment of arsenic mobility in the soils of some golf courses in South Florida

High concentrations of arsenic have been detected in soils and underlying groundwater of some South Florida golf courses, indicating the possible impact of the application of arsenic-containing herbicides. The mobility of arsenic in the soils from selected golf courses was studied using a simple two-step sequential extraction procedure. Sodium nitrate (0.1 M), potassium dihydrogen phosphate (0.1 M) and concentrated nitric acid were used to obtain mobile, mobilizable, and pseudo total arsenic fractions. Soils were separated into fine (<0.25 mm) and large (0.25-0.75 mm) particle size fractions. Arsenic contents were correlated with the distribution of iron (R2=0.4827), manganese (R2=0.7674) and aluminum (R2=5459) in the particle size fractions, while such correlation was not observed for soil organic matter, indicating that the oxides/hydroxides of iron, manganese and aluminum control the distribution of arsenic in these soils. Sodium nitrate and potassium dihydrogen phosphate extractants used in this study extracted large portions of arsenic from most soil samples studied. This is especially true for the fine fraction where the extractable arsenic ranged from 9.2 to 51.3% with an average of 28.7 +/- 13.3%, whereas in the large fraction, arsenic ranged from 7.2 to 24.7% with an average of 15.4 +/- 6.4%. These extractants, however, release only small amounts of iron, manganese, and aluminum. It seems likely that arsenic can be released by sodium nitrate and potassium dihydrogen phosphate without significant dissolution of the oxides/hydroxides of iron, manganese, and aluminum in these soil samples.     

智利中北部海岸山脉中生代层控型铜(银)矿床

文章试对智利一个重要的矿床类型——层控型铜(银)矿床做一综合概括和介绍。层控型铜(银)矿床,是智利继斑岩型、IOCG型(铁氧化物铜金型)之后的第三大矿床类型。主要分布于智利中北部海岸山脉,介于南纬21°~34°。矿床赋存于晚侏罗纪至早白垩纪火山和火山沉积岩系中。具体又可分为两条成矿带:即安托法加斯塔海岸山脉侏罗纪成矿带以及中部白垩纪成矿带。此类矿床的成因虽众说纷纭,但火山喷流沉积加后期次火山侵入体热液叠加改造成因观点理论依据最为充分。矿床的形成、就位是安第斯演化初期,即侏罗纪至早白垩纪的板块俯冲事件产物。     

智利第一大区HNX矿区IOCG型铜矿床地质特征

智利共和国第一大区HNX矿区的IOCG型铜矿床位于智利海岸山褶皱带多金属成矿带内,秘鲁-智利北部IOCG成矿带上,该成矿带褶皱构造强烈发育,富含大量的铜、钼、铅、锌、锰、金、铼、硒、碲等矿产,IOCG型铜矿床作为作为该成矿带的典型矿床,探获铜金属量约3万t,平均厚度5. 74 m,平均品位1. 20%。该文系统描述了矿床的地质特征,分析了成矿地质条件,从矿床的成矿规律以及找矿标志等方面,总结了该矿床的成矿特征与开发经验,对进一步开展矿区周边的找矿工作具有一定的意义。     

智利阿塔卡马区斑岩铜矿带遥感战略选区研究

在国外开展地质找矿工作首先遇到的困难就是相关资料难以收集,遥感战略选区可以解决这一难题。利用遥感技术优势,不仅能克服地域、自然环境等方面的限制,而且可以快速地对区域地质背景及成矿条件等进行分析研究,从而为后续地质工作的开展提供基础资料。此次研究利用多光谱卫星遥感数据,在分析所收集的地质矿产资料基础上,对智利阿塔卡马区斑岩铜矿带开展遥感影像特征及成矿地质条件分析、矿化蚀变信息提取、成矿预测等研究,划分了3个成矿亚带,选取了3个战略选区,圈定了6处找矿靶区,并提出了进一步开展地质找矿工作的建议,取得了良好的应用效果。     

Partitioning and speciation of chromium, copper, and arsenic in CCA-contaminated soils: influence of soil composition

This study focused on the influence of soil composition and physicochemical characteristics on the retention and partitioning of Cu, Cr and As in nine chromated copper arsenate (CCA) artificially contaminated soils. A statistical mixture design was used to set up the number of soils and their respective composition. Sequential extraction and modified solvent extraction were used to assess Cu and Cr partitioning and As speciation [As(III) or As(V)]. It was found that peat had a strong influence on CEC (232 meq/100 g), on buffer capacity and on Cu and Cr retention, whereas kaolinite's contribution to the CEC was minor (38 meq/100 g). Average metal retention in mineral soils was low (58% for Cu and 23% for Cr) but increased dramatically in highly organic soils (96% for Cu and 78% for Cr). However, both organic and mineral soils demonstrated a very high sorption of added As (71-81%). Levels of Cu and Cr in a soluble or exchangeable form (F1) in highly organic soils were very low, whereas the levels strongly bound to organic matter were much higher. Conversely, in mineral soils, 47% of Cu and 18% of Cr were found in F1. As a result, Cr and Cu in moderately and highly organic contaminated soils were present in less mobile and less bioavailable forms, whereas in mineral soils, the labile fraction was higher. The modified method used for selective determination of mineral As species in CCA-contaminated soils was found to be quantitative and reliable. Results revealed that arsenic was principally in the pentavalent state. Nevertheless, in organic soils, arsenite was found in significant proportions (average value of 29% in highly organic soils). This indicates that some reduction of arsenate to arsenite occurred since the original species in CCA is As(V).     

Selenium and its redox speciation in rainwater from sites of Valparaiso region in Chile, impacted by mining activities of copper ores.

The determination of the total concentration of selenium does not provide sufficient information about its toxicity and its bioavailability. The determination of its chemical forms is the basis for understanding the biogeochemical cycle in terrestrial and aquatic ecosystems and for detecting the species which might be toxic to biota. In this work we describe an analytical procedure to carry out the redox speciation of selenium present at ultratrace levels in rainwater from sites of Valparaiso region in Chile, impacted by mining activities of copper ores. A simple preconcentration step of the rainwater sample on a rotavapor system, in vacuum at low temperature permits the concentration of the different redox selenium species until levels quantifiable by sensitive techniques such as differential pulse cathodic stripping voltammetry or by spectrometric techniques, based on the hydride generation and detection by atomic absorption or atomic fluorescence spectrometry. These techniques coupled to redox chemical reactions allow the redox speciation of selenium. The results show that the open evaporation system can be used to concentrate water samples when the aim of the analysis is the determination of the total selenium concentration. On the contrary, to carry out its redox speciation only the preconcentration performed on rotavapor system, in vacuum can be used. When synthetic solutions containing different redox species of selenium, at ultratrace levels, were slowly evaporated on open system, Se(II) and Se(IV) were oxidized. The optimized procedure was then applied to the selenium determination and its redox speciation in rainwater samples collected in sites impacted by mining activities of copper ores. It was found that the amounts of total selenium in rainwater, as copper, from Puchuncavi valley decrease exponentially with the distance from the source, indicating that these elements in this region arise from the industrial complex Las Ventanas. In the redox speciation of selenium, Se(IV) and Se(VI) were the species found in all rainwater samples analyzed, providing selenium in species which are most favorable for their uptake by the vegetation grown in these soils.     

Distribution and mobility of chromium, copper, and arsenic in soils collected near CCA-treated wood structures in Korea

Chromated copper arsenate (CCA) is currently the most commonly used wood preservative in Korea. Questions, however, have been raised regarding the potential environmental impacts of metal leaching from CCA-treated wood to soil. Although a number of researchers from other countries have reported that chromium, copper, and arsenic do leach from CCA-treated wood over time, to date few field studies have been performed on those metals in soils adjacent to CCA-treated wood structures in Korea. The present study was conducted to determine the lateral and vertical distributions and accumulation of chromium, copper, and arsenic in soils collected from CCA-treated wood structures. A total of fifty-five composite soil samples were collected from four CCA-treated wood structures of approximately one year in age. The samples were analyzed for physicochemical properties as well as for the total chromium, copper, and arsenic concentrations. The chromium, copper, and arsenic concentrations in soil samples adjacent to the structures were as high as 79.0, 98.9, and 128 mg/kg, respectively, compared to background soil samples (48.2, 26.9, and 6.27 mg/kg, respectively). Arsenic was more mobile in soil than chromium and copper. The concentration gradient of arsenic in soil was observed only to the depth of approximately 5 cm in one year of outdoor exposure, whereas chromium and copper apparently remained near the surface (approximately less than 1 cm) after their release. Future efforts should be made to observe seasonal impacts on the release of metals and incorporate metal speciation into determining more detailed mobility and distribution.     

Dislodgeable copper,chromium and arsenic from CCA-treated wood surfaces

Chromated copper arsenate (CCA) is commonly used to preserve wood, but its use poses risk of arsenic exposure. In order to evaluate the extent of exposure to As from physical contact with CCA-treated wood, dislodgeable As from treated wood surfaces (as well as Cu and Cr) was determined as a function of weathering time using dampened polyester wipe materials. Six sets of 2.5-m-long CCA-treated boards, three-four boards per set, were purchased from lumber yards and cut into 30- or 60-cm coupons. A total of 44 such coupons were placed outdoors and the dislodgeable CCA components from the surfaces of the wooden coupons were periodically determined over a 1- or 2-year period by a systematic wipe method followed by nitric acid extraction of the CCA components from the cloth. In all 316 samples, appreciable amounts of the three elements, Cu, Cr and As, were detected. The amounts of surface-dislodgeable As, the most potentially hazardous element and the one of major concern in this study, varied from 5 to 122 microg/100 cm(2) with an average value of 37+/-22 microg/100 cm(2). There was considerable variation in As dislodged among coupons, boards, sets and time. Test coupons that tended to release relatively higher (or lower amounts) over time initially, continued to do so over time. However, the amounts of arsenic dislodged over time did not follow a simple pattern. While the As dislodged tended to decrease with time during the first year, it approached the initial value or increased somewhat during the second year, presumably due to surface rejuvenation effects caused by erosion and weathering. When all the data were normalized to the initial values, no trend emerged, as indicated by the average normalized value of 1.0+/-0.4 for As dislodged over time. Apparently, on installations constructed with CCA-treated wood, arsenic may remain available for a number of years.     

Microbial transformations of arsenic: mobilization from glauconitic sediments to water

In the Inner Coastal Plain of New Jersey, arsenic (As) is released from glauconitic sediment to carbon- and nutrient-rich shallow groundwater. This As-rich groundwater discharges to a major area stream. We hypothesize that microbes play an active role in the mobilization of As from glauconitic subsurface sediments into groundwater in the Inner Coastal Plain of New Jersey. We have examined the potential impact of microbial activity on the mobilization of arsenic from subsurface sediments into the groundwater at a site on Crosswicks Creek in southern New Jersey. The As contents of sediments 33-90 cm below the streambed were found to range from 15 to 26.4 mg/kg, with siderite forming at depth. Groundwater beneath the streambed contains As at concentrations up to 89 μg/L. Microcosms developed from site sediments released 23 μg/L of As, and active microbial reduction of As(V) was observed in microcosms developed from site groundwater. DNA extracted from site sediments was amplified with primers for the 16S rRNA gene and the arsenate respiratory reductase gene, arrA, and indicated the presence of a diverse anaerobic microbial community, as well as the presence of potential arsenic-reducing bacteria. In addition, high iron (Fe) concentrations in groundwater and the presence of iron-reducing microbial genera suggests that Fe reduction in minerals may provide an additional mechanism for release of associated As, while arsenic-reducing microorganisms may serve to enhance the mobility of As in groundwater at this site.     

Mobile arsenic species in unpolluted and polluted soils

The fate and behaviour of total arsenic (As) and of As species in soils is of concern for the quality of drinking water. To estimate the relevance of organic As species and the mobility of different As species, we evaluated the vertical distribution of organic and inorganic As species in two uncontaminated and two contaminated upland soils. Dimethylarsinic acid (up to 6 ng As g(-1)), trimethylarsine oxide (up to 1.5 ng As g(-1)), 4 unidentified organic As species (up to 3 ng As g(-1)) and arsenobetaine (up to 15 ng As g(-1)), were detected in the forest soils. Arsenobetaine was the dominant organic As species in both unpolluted and polluted forest soils. No organic As species were detected in the contaminated grassland soil. The organic As species may account for up to 30% of the mobile fraction in the unpolluted forest floor, but never exceed 9% in the unpolluted mineral soil. Highest concentrations of organic As species were found in the forest floors. The concentrations of extractable arsenite were highest in the surface horizons of all soils and may represent up to 36% of total extractable As. The concentrations of extractable arsenate were also highest in the Oa layers in the forest soils and decreased steeply in the mineral soil. In conclusion, the investigated forest soils contain a number of organic As species. The organic As species in forest soils seem to result from throughfall and litterfall and are retained mostly in the forest floor. The relative high concentrations of extractable arsenite, one of the most toxic As species, and arsenate in the forest floor point to the risk of their transfer to surface water by superficial flow under heavy rain events.     

Dynamics of arsenic in agricultural soils irrigated with arsenic contaminated groundwater in Bangladesh

Arsenic (As) concentrations in the soil layers of 12 rice fields located in four As affected areas and two unaffected areas in Bangladesh were monitored during 2003. In the unaffected areas, where irrigation water contained little As (<1 microg/L), As concentrations of rice field soils ranged from 1.5 to 3.0 mg/kg and did not vary significantly with either depth or sampling time throughout the irrigation period. In the As affected areas where the irrigation water contained elevated As (79 to 436 microg/L), As concentrations of rice field soils were much higher compared to those in the unaffected areas and varied significantly with both depth and sampling time. For the top 0 to 150 mm of the soil, the As concentration increased significantly at the end of the irrigation season (May-June 2003). About 71% of the As that is applied to the rice field with irrigation water accumulates in the top 0 to 75 mm soil layer by the end of the irrigation season. After the wet season during which the rice fields were inundated with flood/rain water, the As concentrations in the soil layer decreased significantly and were reduced to levels comparable to those found in soil samples collected at the beginning of the irrigation period. The long-term As accumulation in agricultural soil appears to be counteracted by biogeochemical pathways leading to As removal from soil.     

Mobility of copper, chromium and arsenic from treated timber into grapevines

The use of chromated copper arsenate (CCA) treated timber posts as support structures in New Zealand vineyards has raised concerns regarding the release of heavy metal(loid)s from the treated timber into the environment. A laboratory experiment was set up to evaluate if post sealing by painting reduces the release rate of CCA metal(loid)s from timber posts. Three posts were painted (Gripset 38, Multi Purpose Bitumen Rubber) on the bottom part, submerged in freshwater, and the concentrations of copper (Cu), chromium (Cr) and arsenic (As) in the water were monitored over a period of 8 months. Three additional, unpainted posts were also used. The CCA contents in the water showed a clear difference between the painted and the unpainted posts, and painting the bottom of the posts reduced the release rate by 50-75%. To monitor the possible mobility of CCA from treated posts into grapevines further, an experiment with four-year-old grapevines planted into sixteen lysimeters was set up in a greenhouse. To half the lysimeters Cu, Cr and As were added to the soil surface at rates of 16, 20, and 12.5 mg/month from 15 November 2005 to 5 May 2006. The other lysimeters acted as a control. Soil solutions were collected at 50, 150 and 300 mm depths using suction cups after seven application of the CCA solution. The results showed that all the elements moved to a depth of 50 mm. Grape fruit, leaves and rachis were analysed for CCA metal(loid)s, but did not show any differences between the CCA-treated and control lysimeters. This indicated either that these metals were not taken up by grapevines or that their translocation from roots to the upper part of the vine was negligible. Further monitoring of CCA metal(loid)s in various parts of the grapevines, including roots, needs to be undertaken.     

Mapping of the orientation of fine-grained minerals in soils and sediments

A technique is described which enables the orientation of fine-grained minerals, which frequently surround larger mineral grains in soils and sediments, to be mapped as regions or domains containing similarly aligned features. Several stages are required, beginning with the digital acquisition of back-scattered electron images and associated elemental maps. Mineral classification provides a means to create an image mask to remove the larger grains before analysis of the fine-grained fraction. Orientation analysis by the intensity gradient method is followed by domain segmentation. Finally, this domain segmented image is combined with the original to highlight both orientation and fine detail. Such a resulting image provides a more objective way of interpreting clay coating features, and enables the size and general orientation of the domains to be assessed.     

A 1500-year record of lead, copper, arsenic, cadmium, zinc level in Antarctic seal hairs and sediments

To reconstruct the profiles of heavy metal levels in the South Ocean ecosystem of Antarctica, the concentrations of lead (Pb), copper (Cu), arsenic (As), cadmium (Cd), and zinc (Zn) in seal hairs and lake sediments spanning the past 1500 years from Fildes Peninsula of King George Island and in weathering lake sediments from Nelson Island of West Antarctica were determined. The lead contents in the seal hairs and the weathering sediments show a sharp increase since the late 1800s, very likely due to anthropogenic contamination from modern industries. After the 1980s, the Pb content in seal hairs dropped by one-third, apparently due to the reduced usage of leaded gasoline in the Southern Hemisphere. Copper arises mainly from the weathering process, and its level may be substantially affected by climatic conditions. The concentrations of Cd, As, and Zn do not show any clear temporal trends.     

Vanadium in particles and sediments of the northern Saronikos Gulf, Greece

This study provides data for total and non-residual vanadium distributions in the northern Saronikos Gulf and shows that close to the Athens sewage outfall (ASO), the combined domestic and industrial wastes have resulted in a considerable increase in concentrations of vanadium in sediments and suspended solids. This appears to be the main vanadium source in the area; a second major source is a fertilizer plant (FP) near the entrance of Piraeus Harbour (PH), the impact of which is also important. Atmospheric inputs from the Piraeus industrial site and frequent crude oil spillages from ships and land-based sources seem to contribute significantly to the observed vanadium distribution, which is clearly affected by the prevailing circulation of surface waters and winds. The high percentage of the 0.5 NHCl-leachable vanadium fraction in the most polluted sediments, together with positive correlation with organic carbon and certain other trace metals (i.e. Ag, Co, Cr, Fe, Zn) and negative correlation coefficients with Al and Sc, indicate that a considerable portion of the vanadium is of "anthropogenic" origin not related to lithogenous particles. It enters the system in association with relatively large organic aggregates, either authigenic or derived from sewage.     

pH与Eh对郑州北郊水源地沉积物中砷溶出的影响

以郑州市北郊水源地富砷区域的地层沉积物(粗砂、细砂、粉土、黏土)为实验材料,研究了pH和氧化还原电位(Eh)对沉积物中砷溶出的影响规律,并分析了两个因素影响沉积物中砷溶出的原因.实验结果表明:碱性环境及还原环境有利于沉积物中砷的溶出.