Geochemical Behavior Of Metals Research Articles

Investigation on metal geochemical cycling in an anthropogenically impacted tidal river in Belgium

The geochemical behavior of metals in water and sediment was investigated in the tidal section of the Zenne River in Belgium. Twelve-hour sampling campaigns were performed in October 2013 and March 2021 at the mouth of the Zenne River, under dry and rainy weather conditions respectively. Water samples were collected every hour while the passive samplers of Diffusive Gradients in Thin-films (DGT) were deployed continuously during a tidal cycle. In addition, bottom sediments were sampled at the tidal station and water samples were taken upstream and downstream of that station to identify the metal sources. The highest concentrations of Fe, Mn, Pb, Cr, Ni and Zn appear at low tide, indicating the Zenner River as a main source. However, for Co, Cd and Cu, other sources including upstream transport may explain their behavior during a tidal cycle. Fe, Pb and Cr are essentially transported in the particulate phase (<10 % dissolved) while the other metals in the dissolved phase (20 to 90 %). Rainfall and wind gust events also play an important role in trace metal distribution, increasing sediment resuspension and metal desorption. A good agreement was found between the time-averaged dissolved and DGT-labile metal concentrations with the exception of Cu and Fe, which form strong organic Cu complexes and Fe colloids respectively. The sediments of the tidal Zenne are contaminated by trace metals, thus acting as a secondary pollution source to the river. The reductive dissolution of Mn and Fe oxyhydroxides and the release of associated trace metals are the main mobilization mechanisms. Knowledge of the upstream and downstream levels in the water column, the benthic fluxes, which are based on turbulent diffusion, and the partitioning between dissolved and particulate phases allow to explain the metal concentration variations during the tidal cycle.

The geochemical behavior of metals during early diagenetic alteration of buried manganese nodules

Marine polymetallic nodules and crusts represent an important resource for numerous metals such as Ni, Co, Cu, Mn and thus may be subject to deep sea mining operations in the future. Manganese nodules have a widespread occurrence on the seafloor of the Clarion-Clipperton Zone (CCZ) in the equatorial North Pacific and have been intensively studied in the past. They consist of hydrogenetic layers formed by precipitation from ambient oxic seawater and diagenetic layers sourced from suboxic pore water. While numerous studies have focused on nodules found on the sediment surface, only a few have dealt with nodules buried at greater sediment depth. In this study, we have thus systematically investigated the diagenetic processes altering the chemical and mineralogical composition of buried nodules in the eastern CCZ down to a sediment depth of around 10 m and assessed the influence of these processes on sediment geochemistry.Our results show that nodules subject to suboxic conditions are not simply reductively dissolved but react with the surrounding sediment and pore water. After burial, the hydrogenetic layers start to dissolve and the associated metals (Mn, Ni, Co, Cu, Mo) are released into the pore water. The remaining Fe oxides react with the surrounding sediment and pore water to form an authigenic Fe-Si-Al-rich layer consisting of nontronite and goethite. The diagenetic layers of buried nodules were found to be highly enriched in Co and Ba and strongly depleted in Mo, Zn and Li compared to surface nodules. The strong, up to 4-fold enrichment of Co during burial under suboxic conditions is noteworthy since the distribution of this element in nodules is commonly used as a proxy for oxic conditions in surface sediments. Here, the Co enrichment is interpreted to result from a redox reaction with Mn. When suboxic conditions in the sediment prevail long enough, the diagenetic Mn oxide phases are also reductively dissolved and only the Fe-oxide component of the former nodule remains.Under the changing redox conditions associated with burial, Mn nodules exert a strong control on the mobility of metals by either fixing them into the crystal lattice of the Mn mineral phases or releasing them into pore water during their reductive dissolution.

Geochemical behavior of metals and metalloids in an estuary affected by acid mine drainage (AMD)

The Tinto and Odiel rivers in southwest Spain drain the world's largest sulfide mineral formation: the Iberian Pyrite Belt which has been worked since 2,500 BC. The Tinto and Odiel estuarine zones include both an extensive area of salt marsh and an intensively industrialized urban area. As a consequence of pyrite oxidation, the Tinto and Odiel rivers are strongly acidic (pH < 3) with unusually high and quite variable metal concentrations. In this study, seasonally varying concentrations of dissolved major and trace elements were determined in the acid mine drainage affected estuary of the Ría de Huelva. During estuarine mixing, ore-derived metal concentrations exhibit excellent correlations with pH as the main controlling parameter. As pH increases, concentrations of dissolved ore-associated elements are attenuated, and this process is enhanced during the summer months. The decrease in Fe and Al concentrations ranged from 80 to 100 % as these elements are converted from dissolved to sediment-associated forms in the estuary. Coprecipitation/adsorption processes also removed between 60 and 90 % of the originally dissolved Co, Cu, Mn, Pb, Zn, and Th; however, Cd and Ni exhibited a greater propensity to remain in solution, with an average removal of approximately 60 %. On the other hand, As and U exhibited a different behavior; it is likely that these elements remain in dissolved forms because of the formation of U carbonates and soluble As species. Concentrations of As remain at elevated levels in the outer estuary (average = 48 μg L(-1)) which exceeds concentrations present in the Tinto River. Nevertheless, the estuary has recently witnessed improvements in water quality, as compared to results of several previous studies reported in the 1990s.

Hydrochemistry, mineralogy and chemical fractionation of mine and processing wastes associated with porphyry copper mines: A case study from the Sarcheshmeh mine, SE Iran

Abstract The Sarcheshmeh is one of the largest Oligo-Miocene porphyry Cu deposits in the world. Comparative hydrochemical, mineralogical and chemical fractionation associated with mining efflorescence salts and processing wastes of this mine are discussed. Hydrochemical results showed that rock waste dumps, reject wastes and old impoundments of tailings are the main sources of acid mine drainage waters (AMD) that contain potentially toxic metals such as Cd, Co, Cu, Mn, Ni and Zn as well as Al. Episodic fluxes of highly contaminated acidic waters were produced in a tailings dam over a short period of time. Secondary soluble minerals provide important controls on the quality of AMD produced, especially in old, dry tailings impoundments. Secondary sulfate minerals such as gypsum, magnesiocopiapite, hydronium jarosite, kornelite and coquimbite were found in rock waste drainages and in old weathered reject wastes. Highly soluble secondary minerals such as gypsum, eriochalcite, and bonattite are also observed in an evaporative layer on old tailings impoundments. Chemical fractionation patterns of potentially toxic elements showed that the geochemical behavior of metals is primarily controlled by the mineralogical composition of waste samples. Elements such as Co, Cr, Cu, Mn, Ni and Zn are readily released into the water soluble fraction from efflorescence salts associated with rock waste drainages, as well as from the evaporative layer of old tailings. Potentially toxic elements, such as As, Mo and Pb, are principally adsorbed or co-precipitated with amorphous and crystalline Fe oxides, but they may also be associated with oxidizing, primary sulfides and residual fractions. Following the development of the dammed tailings pond, the secondary minerals were dissolved, producing acidic waters contaminated by Al (154 mg L −1 ), Cu (150 mg L −1 ), Cd (0.31 m gL −1 ), Co (2.13 mg L −1 ), Mn (73.7 mg L −1 ), Ni (1.74 mg L −1 ), Zn (20.3 mg L −1 ) and Cl (1690 mg L −1 ). Therefore, the potential use of recycled water from the Sarcheshmenh dammed tailings pond is diminished by the presence of corrosive ions like Cl − in highly acidic fluids that promote corrosion of pipes and pumps in the water recycling system.

The influence of colloids on the geochemical behavior of metals in polluted water using as an example Yongdingxin River, Tianjin, China

The role of colloids in estuarine and marine systems has been studied extensively in recent years, whereas less is known about the polluted freshwater system. Yongdingxin River is one of the major recipients of industrial effluents in Tianjin. This article evaluates the role of colloids in controlling geochemical behavior of Cu, Zn, Fe, Mn, Hg and Cr at the confluences between Yongdingxin River and its major tributaries Beijing Drainage River, Jinzhong River and Beitang Drainage River. Based on the distribution of metal partitioning among particulate (>0.22 μm), colloidal (1 kDa to 0.22 μm) and truly dissolved (<1 kDa) fractions, the metals can be assigned to the following groups: Group 1 – organic colloidal pool-borne elements Cu and Cr; Group 2 – inorganic colloidal pool-borne metals Fe and Mn; Group 3 – Zn and Hg characterized by varying complexation patterns. The distribution of metal partitioning among particulate, colloidal and truly dissolved fractions was influenced by anthropogenic input. In addition, the theoretical concentrations of elements in case of conservative mixing between the waters of Yongdingxin River and the waters of its tributaries were compared with the measured values to evaluate the geochemical role of colloids. The result showed that all of the metals presented a non-conservative mixing behavior. Addition of colloids resulted in the removal of metals from the water column to bed sediment during river water mixing, which was furthermore confirmed by the similar partition coefficient of metal concentration between colloid and sediment.

Characterization of soil heavy metal pools in paddy fields in Taiwan: chemical extraction and solid-solution partitioning

Characterization of soil heavy metal pools in paddy fields in Taiwan: chemical extraction and solid-solution partitioning

Metals adsorbed to charcoal are not identifiable by sequential extraction

Environmental context. Charcoal is widespread in soils and may be a major component of soil organic matter. Trace metal ions in soils are predominantly associated with solid phase materials, including charcoal, and the identity of the solid phase and the mechanisms of association influence the geochemical behaviour of metals. Metals associated with soil mineral phases are estimated using techniques such as selective sequential extraction, and the sorption reactions of metal ions are well understood. Much less is known about the associations of trace metals with natural charcoal, and metals associated with charcoal in soils are likely to be misidentified in sequential extraction procedures. Abstract. Given that up to 50% of the soil carbon store can consist of charcoal, it is possible that trace elements can become immobilised through their interaction with natural charcoal. Hence, natural charcoal may be a significant sink that has yet to be accounted for in trace element biogeochemical cycles. Testing this hypothesis becomes problematic considering the typically small size (&lt;53 µm) of charcoal particles that occur naturally in Australian soils, making isolation and analysis of natural soil charcoal difficult. Therefore, in this study, we test the robustness of a typical sequential extraction technique by applying it to naturally occurring charcoal that had been spiked with five different concentrations of metal ions (Al3+, Cr3+, Cu2+, Ni2+, Zn2+, Cd2+, Ag+, Pb2+). The method was then applied to contrasting soils mixed with this spiked charcoal. The sequential extraction scheme consisted of the following five extractions the in order: (1) sodium acetate (targeting the adsorbed-exchangeable-carbonate fraction), (2) sodium pyrophosphate (organic fraction), (3) ammonium oxalate (amorphous iron/manganese oxides), (4) hydroxylamine hydrochloride (crystalline iron/manganese oxides) and (5) residual (aqua regia digest). The majority of metals added to the charcoal were extracted in the fractions targeting both the amorphous and crystalline iron and manganese oxides, at low additions of metal ions. At higher additions of metals, the metals were mostly extracted from charcoal in the adsorbed-exchangeable-carbonate fraction. When the spiked charcoal was added to soils, a trend similar to the charcoal-only experiment was observed in the sequential extraction data. Higher concentrations of metals (compared with the control) were extracted for the charcoal-amended soils, in the same fractions as in the charcoal-only extractions. Since the concentration of metals extracted in the various extractants changed with increasing metal loads on charcoal, sequential extractions cannot be used to identify the contribution of metals from the charcoal pool. Therefore, a potentially large pool of trace elements could be misrepresented when sequential extraction techniques are applied, particularly for soils in which there is a large concentration of charcoal. Hence, there is still a large gap in knowledge with regard to the significance of charcoal in ‘real’ soils, particularly with respect to the role of charcoal as a trace element sink.

Geochemical survey and metal bioaccumulation of three bivalve species ( Crassostrea gigas, Cerastoderma edule and Ruditapes philippinarum) in the Nord Médoc salt marshes (Gironde estuary, France)

A 15-month experiment combining a geochemical survey of Cd, Cu, Zn and Hg with a bioaccumulation study for three filter-feeding bivalve species (oysters, Crassostrea gigas; cockles, Cerastoderma edule; and clams, Ruditapes philippinarum) was conducted in a breeding basin of the Nord Médoc salt marshes connected to the Gironde estuary, which is affected by historic polymetallic pollution. Regular manual surface measurements of temperature, salinity, pH and dissolved O 2 concentration and hourly multiprobe in situ measurements throughout several periods for 6–8 weeks were performed. The geochemical behavior of metals in water, suspended particulate matter and sediment and their ecotoxicological impact on the three bivalve species were evaluated by in situ exposure of juvenile oysters (water column) and adult cockles and clams (sediment surface). The physico-chemical parameters reflected seasonal variations and basin management. A distinct daily periodicity (except salinity) indicated intense photosynthesis and respiration. In summer, low dissolved O 2 saturations (∼40–50%) occurred in the early morning at 30 cm above the sediment, whereas in depressions, the water column near the sediment surface was suboxic. Cadmium, Zn and Cu concentrations in suspended particulate matter exceeded typical estuarine values and were much higher than the homogeneously distributed concentrations in different depth ranges of the basin sediment. Particles collected in sediment traps showed intermediate metal concentrations close to sediment values. These results suggest trace metal recycling due to reductive dissolution under suboxic conditions at the sediment surface resulting in trace metal release to the water column and adsorption onto suspended particles. Dissolved Cd, Zn and Hg concentrations (e.g. 13–136 ng l −1; 0.3–25.1 μg l −1 and 0.5–2.0 ng l −1, respectively) in the basin corresponded to the concentration range typically observed in the Gironde estuary, except for some maximum values attributed to metal recycling. In contrast, dissolved Cu concentrations (1.08–6.08 μg l −1) were mostly higher than typical estuarine values, probably due to recycled Cu complexation by dissolved organic matter. Growth, bioaccumulation rates and kinetics in the whole soft body of the bivalves were analyzed every 40 days. Although Cd bioaccumulation of oysters was lower in the basin than in the estuary during the same period (27,000 ng g −1, dry weight and 40,000 ng g −1, respectively) these values are largely above the new human consumption safety level (5000 ng g −1, dw; European Community, 2002). For cockles and clams, Cd bioaccumulation was lower, reaching 1400 ng g −1 and 950 ng g −1, respectively. Similar results were obtained for Zn and Cu suggesting physiological differences between the species and/or differences in the exposure of the organisms due to physico-chemical conditions and metal distribution between dissolved and particulate phases. In contrast, Hg bioaccumulation was highest for cockles reaching bioconcentration factors of ∼200,000, which even exceeded that of Cd in oysters (50,000) for the same exposition period. Nevertheless, Hg concentrations remained relatively low in the three bivalve species.

METAL CONTAMINATION AT DUMP SITES IN MAKURDI, NIGERIA

This study has focused on the investigation of metal contamination by refuse dumps in Makurdi, Nigeria. Soil samples were collected from 17 dump sites and also from a forest to serve as control. Samples were pretreated, digested by aqua regia and the resulting solution analyzed for Fe, Zn, Cu, Pb and Cd using atomic absorption spectrophotometer (AAS). Result shows that the range of iron was 120 –440ppm, zinc 100-260ppm; copper16-201ppm; lead 10-115ppm and cadmium 2-30ppm; in soil from refuse dump sites while forest soil has a range of 120-300ppm for iron, 25 –150ppm for zinc, 20-50ppm for copper, 7-31ppm for lead and 0.5-3.5ppm for cadmium. The significant difference between result obtained for refuse dump sites and the forest soil indicates that refuse dump sites most probably represent point sources of metal contamination to nearby environment. This study also examined metal mobility with 0.1M HCI solution. Result shows that extraction rates (mobility) were in the order Zn>Cd>Cu>Pd> Fe which may be due to differences in geochemical behaviour of metals in the soil. Finally the concept of pollution index (Pl) of soils was applied to determine the extent of multi-element contamination caused by refuse dumps. Keywords: Extraction rate, Makurdi, metal contamination, pollution index, refuse dumps. [Global Jnl Geol. Sci. Vol.1(1) 2003: 85-94]

Laboratory investigation of the geochemical behavior of metals in paddy soils contaminated with mine tailings

The geochemical behavior of metals, including Fe, Mn, Pb and Zn, in contaminated paddy soils was investigated during the cultivation of rice crops through laboratory microcosm experiments. From the two paddy fields contaminated by mine tailings, Siheung and Deokeum in Korea, paddy soils were collected and analyzed for their geochemical characteristics. The Siheung paddy soil showed higher levels of heavy metals, whereas the higher potential for the release of metals was anticipated due to the extremely acidic conditions at Deokeum. In microcosm experiments of flooded paddy soils over 18 weeks, Fe and Mn were released in subsurface pore waters by reductive dissolution, and Pb and Zn were dissolved in high amounts at the surface by oxidation of sulfides. Although amorphous Fe oxide-rich layers were formed at the surface of both paddy soils, the release of Pb and Zn were controlled at the surface by these layers only under slightly alkaline conditions at Siheung. Lead and Zn were associated with the reducible and carbonate fractions at the surface paddy soil of Siheung from the sequential extraction on core samples collected during the flooded period. In the acidic conditions at Deokeum, Pb and Zn were continuously released until the late stage of flooding. A great increase in the exchangeable fraction of metals was observed after the soils had drained. The bioavailability of metals for rice crops would be high under acidic conditions at Deokeum, despite the lower levels of heavy metal contamination.

Quantitative relationships among giant deposits of metals

Metallogenic studies that try to identify the geochemical fluxes of metals in the lithosphere leading to ore formation have a higher sensitivity when the traditional mining data, based on grades and tonnages, are normalized to crustal element abundances, and derivative units such as clarke of concentration and tonnage accumulation index are used. This technique has been applied to the world-class deposits of all industrial metals, i.e., to 34 metals plus the rare earth elements and platinoid groups. The lower magnitude limits for inclusion in the giant and supergiant categories (ore metal content in a deposit/metal clarke > i X 1011 metric tons (t) and 101.2 t of average crustal material, respectively) have been established for each metal. There are, presently, 486 giant and 61 supergiant metal accumulations of the various metals in 446 deposits and districts. A single deposit and/or district, such as the Olympic Dam Cu-U-Au-REE-Fe deposit, could be the site of a giant accumulation of more than one metal. Cu with 103 giant accumulations followed by Au (99), Pb (55), Mo (41), Sb (24), and Sn (22) are the most superaccumulated metals, whereas 11 metals entirely lack giant deposits. Although this is partly influenced by economic factors, such as low demand and price, the main cause is the geochemical behavior of metals, especially the trace metals compatibilities at the various stages of crustal evolution. Porphyry Cu-Mo deposits have the greatest number of giant accumulations among the popular ore deposit types (90), followed by sedimentary exhalative Zn-Pb-Ag (23), volcanogenic massive sulfides (22), stockwork Mo (17), epithermal Au-Ag veins (13), and Broken Hill-type Pb-Zn-Ag (12). In terms of origin, the greatest number of giant deposits is among the mesothermal Cu deposits (67), which reflect the porphyry Cu-Mo preeminence, followed by mesothermal Au (61), mesothermal Mo (39), mesothermal Sb (22), mesothermal Pb (19), and sediment-hosted Cu deposits at redox interfaces (19). As a class, the mesothermal epigenetic deposits account for 271 giant metal accumulations, which represents 52 percent of the entire database. Hydrothermal deposits including exhalative and epithermal deposits possess 333 giant representatives, or 63.5 percent. Other genetic families of ore deposits, including precipitates from less than 150oC hot hydrous fluids (59 giant deposits), orthomagmatic deposits (40), sedimentary deposits (39), and weathering-generated deposits (14), are less significant. An astonishing 446 giant metal accumulations (92.5%) thus relied on water as the principal agent of formation. Of the giant deposits genetically associated with magmatism, the metaluminous granodiorite-quartz monzonite suite at subductive margins is related to most giant deposits (98, or 19%). Second in importance is the high potassium granite suite (23 giant deposits). Carbonatites, with only about 350 occurrences known worldwide, are the most striking rare magmatic hosts to giant deposits. Five carbonatites host giant or supergiant deposits and an additional 11 carbonatites host large deposits (i.e., tonnage accumulation index > ix 101o t), so there is a 4.5 percent chance that any newly discovered carbonatite will host a large or giant deposit. The major period of preserved giant deposit accumulation occurred during lower-middle Tertiary (103 giant deposits or 20% of the total), followed by middle-upper Tertiary (59 giant deposits), Jurassic (39 giant deposits), Carboniferous (37 giant deposits), and Paleoproterozoic (33 giant deposits). The predominantly young age of mineralization indicates that shallow crustal depths or subsiding subaqueous and subaerial depositories provide the most favorable milieu for superaccumulation

Topography, weather and human activity effects on the behavior of metallic elements in a tropical catchment

The geochemical behavior of metals in 11 rivers of the Lake Valencia drainage system, north-central Venezuela, was investigated by repeated sampling. Pb, Zn, Ni, Cu and Cr discharges from domestic and industrial activities have resulted in concentration increases of 2–16× above background levels, depending on the metal, as well as an increase of 13–27% of the labile fraction (% LF). No apparent effect on the metals' grain-size distribution was observed. Evidence suggests that chemical reactions, coupled with transport of sediments from the mountainous areas to lowland areas, produce: (1) an increase in metal concentration and % LF, which are concomitant with the pollution effect; and (2) a metals' grain-size redistribution toward fine fractions. Analysis of major elements, i.e. Na, K, Mg, Ca, Al and Fe, provides a suitable approach to discriminate the two effects mentioned above. The wet-dry season variability in metal concentration appeared to be controlled mainly by the input of flushed material from soil. This process can explain the large areal variability of concentrations compared with sampling and analytical variability. A physical dilution of Zn with less contaminated, flushed soil material was also observed.