Distribution and enrichment of trace metals in marine sediments of Bay of Bengal,off Ennore,south-east coast of India

In order to avoid the pollution of trace metals in marine environment, it is necessary to establish the data and understand the mechanisms influencing the distribution of trace metals in marine environment. The concentration of heavy metals (Fe, Mn, Cr, Cu, Ni, Pb, Zn, Co and Cd) were studied in sediments of Ennore shelf, to understand the metal contamination due to heavily industrialized area of Ennore, south-east coast of India. Concentration of metals shows significant variability and range from 1.7 to 3.7% for Fe, 284–460 μg g⁻¹ for Mn, 148.6–243.2 μg g⁻¹ for Cr, 385–657 μg g⁻¹ for Cu, 19.8–53.4 μg g⁻¹ for Ni, 5.8–11.8 μg g⁻¹ for Co, 24.9–40 μg g⁻¹ for Pb, 71.3–201 μg g⁻¹ for Zn and 4.6–7.5 μg g⁻¹ for Cd. For various metals the contamination factor (CF) and geoaccumulation index (I _geo) has been calculated to assess the degree of pollution in sediments. The geoaccumulation index shows that Cd, Cr and Cu moderately to extremely pollute the sediments. This study shows that the major sources of metal contamination in the Ennore shelf are land-based anthropogenic ones, such as discharge of industrial wastewater, municipal sewage and run-off through the Ennore estuary. The intermetallic relationship revealed the identical behavior of metals during its transport in the marine environment.     

Mobility and ecological risk assessment of heavy metals in surface sediments of Xiamen Bay and its adjacent areas,China

Xiamen Bay (XMB) has received substantial loadings of pollutants from industrial and municipal wastewater discharged since the 1980s. To assess ecological risks and the current spatial changes of metal contaminants in bottom surface sediments, 12 samples were collected. Samples were subjected to a total digestion technique and analyzed by ICP–OES for Cu, Pb, Zn, Cr, and Cd, and by AFS for Hg and As. Among these metals, Zn had the highest values (68–268 mg kg⁻¹), followed by Pb (27–71 mg kg⁻¹), and lower concentrations were found for Cd (42–1,913 μg kg⁻¹) and Hg (0–442 μg kg⁻¹). In comparison with the average crustal abundance values, the results indicated that nearly half of the sediment samples of XMB and its adjacent areas were contaminated by Cd, Pb, Zn, and As. Furthermore, based on the modified BCR sequential extraction procedure, the chemical speciation of heavy metals (Cd, Cr, Cu, Pb, Zn, Hg, and As) in selected sediment samples were evaluated in this study. Data from BCR sequential extractions indicated that Cd posed a medium ecological risk, whereas, Cr posed low risk since its exchangeable and carbonate fractions were below 4%, and the mobility of heavy metals in XMB decreased in the order Cd > Pb > Cu > Zn > Hg > As > Cr. By applying mean effects range median quotients (mERMQ), the results showed that Yuandang Lagoon with mERMQ value >0.5 would be expected to have the greatest potential toxic risk in amphipod within XMB and its adjacent areas.     

Speciation and phytoavailability of heavy metals in sediments in Nanjing section of Changjiang River

Heavy metal pollution and their fractionations in the sediments of Changjiang River in Nanjing Reach was monitored for cadmium (Cd), lead (Pb), zinc (Zn), chromium (Cr), and copper (Cu). Moreover, the biological enrichment of metals by riverine plants was studied. The results demonstrated there were highly significant variations among different sampling stations for the concentrations of tested metals. The highest range was for Cu (38.8–120.4 mg kg⁻¹), followed by Cr (74.4–120.0 mg kg⁻¹), Zn (80.9–121.1 mg kg⁻¹), Ni (26.0–55.5 mg kg⁻¹), Pb (15.8–46.7 mg kg⁻¹) and Cd (0.28–0.48 mg kg⁻¹). Cd was the element with highest biological enrichment factor (BEF). The highest BEF of Cd in Erigeron bonariensis reached 3.0, indicating a significant Cd enrichment in this aquatic plant. In addition, 60% of Cd was found in reducible fraction and exchangeable and acid-soluble fraction, which was consistent with its high mobility. The consistency of Cd fraction in sediment and suspended particle indicated they came from the same source. Accumulated Cd concentration calculated according to the release curve showed significant relativity with the total Cd concentration in the sediment.     

Arsenic, antimony and other toxic elements in the drinking water of Eastern Thessaly in Greece and its possible effects on human health

Twenty-six groundwater samples were collected from the Eastern Thessaly region and analysed by ICP-ES for these elements: Al, As, P, Pb, Zn, Mn, Fe, Cr, Sb, Cu, Na, Br, Cl, Si, Mg, Ag, Be, Bi, Dy, Er, Eu, Au, Ge, Ho, In, Ir, Os, Pt, Re, Rh, Ru, Lu, Hf, Hg, Tm, Zr and Nb. The objectives of the study were to assess the level of water contamination with respect to the EC and the USEPA health-based drinking water criteria. The geology of the studied area includes schists, amphibolites, marbles of Palaeozoic age, ophiolites, limestones of Triassic and Cretaceous age, Neogene and Quaternary deposits. The element ranges for groundwater samples are: Al 7–56 μg l⁻¹, As 1–125 μg l⁻¹, Br 6–60 μg l⁻¹, Cl 500–25,000 μg l⁻¹, Cr 1–6 μg l⁻¹, Cu 1–15 μg l⁻¹, Fe 10–352 μg l⁻¹, Mg 2,940–40,100 μg l⁻¹, Mn 0–8 μg l⁻¹, Na 3,650–13,740 μg l⁻¹, P 20–48 μg l⁻¹, Pb 0–7 μg l⁻¹, Sb 0–21 μg l⁻¹, Si 3,310–13,240 μg l⁻¹ and Zn 7–994 μg l⁻¹. The results of groundwater analyses from the region of Eastern Thessaly showed elevated concentrations of As and Sb. Factor analysis explained 77.8% of the total variance of the data through five factors. Concentration of Br, Cl, Mg, Na and Si is directly related to the presence of saltwater in the aquifer, so grouping of these variables in factor 1 probably reflects the seawater intrusion. Al, As and Sb are known to form complexes in the environment, so grouping of these elements in factor 2 indicates their similar geochemical behaviour in the environment. The high negative loading of Mn in factor 2 indicates the presence of manganese oxides–hydroxides in the study area. Pb and Zn are associated together in sulphide mineralisation; so grouping of these elements in factor 3 reflects the sulphide mineralization paragenesis in the Melivoia area. P and Cu are associated together in phosphate fertilizers; so grouping of these variables in factor 4 could be related to agricultural practices. Cr, Fe, Mn and Mg are associated together in iron and manganese oxides–hydroxides and the weathering products of the olivine of the ultrabasic rocks; so grouping of these elements in factor 5 reflects the lithology of the area. There is a natural contamination of groundwaters with elevated concentrations of As and Sb due to the presence of the arsenopyrite and stibnite mineralisation in the Melivoia, Sotiritsa and Ano Polydendri areas. Contamination over the health-based drinking water guidelines given by EC and EPA has been investigated from nine sampling sites out of 26 of Eastern Thessaly region.     

Partition of arsenic in soils sediments and the origin of naturally elevated concentrations in groundwater of the southern pampa region (Argentina)

Excessive arsenic concentrations above the Argentinean and WHO guidelines for drinking water (10 μg L⁻¹) affects shallow aquifers of the southern Pampean Plain (Argentina) hosted in the Pampean and the Post Pampean formations (loess and reworked loess; Plio-Pleistocene–Holocene). Health problems related to high As concentrations in drinking waters are known as Endemic Regional Chronic Hydroarsenicism. Hydrochemistry of shallow groundwaters and soil geochemistry were investigated aiming to (1) understand the partition of As in the solid phase and its relationship with unacceptable As concentrations in waters, (2) identify the provision source of As to groundwaters. Only 5% of the samples had As concentrations <10 μg L⁻¹; in 27% As concentrations ranged from 10 to 50 μg L⁻¹ and in 58% it reached 60–500 μg L⁻¹. The coarse fraction (50–2,000 μm) hosts about 27% of the total As in the solid phase, being positively correlated to Ba (p < 0.01; r ² = 0.93). About 70% is included in the <2 μm fraction and had positive correlations of As–Fe (p < 0.05; r ² = 0.85) and As–Cr (p < 0.05; r ² = 0.68). Soils and sediment sand fractions of vadose zones are the primary sources of As in shallow groundwater while adsorption–desorption processes, codisolution–coprecipitation, and evaporation during the dry seasons raise As concentrations in waters exceeding the guideline value for drinking water.     

Trace Metals (Cd,Cu, Hg,and Pb) Accumulation Recorded in the Intertidal Mudflat Sediments of Three Coastal Lagoons in the Gulf of California,Mexico

²¹⁰Pb geochronologies of Cd, Cu, Hg, and Pb fluxes were obtained from the intertidal mudflat sediments of the coastal lagoons Chiricahueto, Estero de Urías, and Ohuira in the Mexican Pacific. The Cu and Hg sediment concentrations at the three lagoons fell within the ranges of 6–76 μg g⁻¹ and 0.1 to 592 ng g⁻¹, respectively; Chiricahueto and Estero de Urías sediments had comparable Cd and Pb concentrations within the ranges of 0.2–2.1 μg g⁻¹ and 10–67 μg g⁻¹, respectively; whereas in Ohuira lagoon, Cd concentrations were lower (0.1–0.5 μg g⁻¹) and Pb concentrations were higher (115–180 μg g⁻¹) than in the other lagoons. The metal fluxes (μg cm⁻² y⁻¹) for the three lagoons fell within the ranges of 0.02–0.15 for Cd, 0.7–6.0 for Cu, 0.001–0.045 for Hg, and 0.7–20 for Pb. The Hg pollution in Estero de Urías was attributed to the exhausts of the thermoelectric plant of Mazatlan and the metal enrichment in Chiricahueto and Ohuira was related to the agrochemical wastes from the croplands surrounding these lagoons.     

The chemistry of suspended particulate material in a highly contaminated embayment of Port Jackson (Australia) under quiescent,high-wind and heavy-rainfall conditions

This study investigated physico-chemical characteristics of the water column and chemistry of suspended particulate material (SPM) under quiescent, high-wind and high-wind/heavy-rainfall conditions in Homebush Bay, a highly contaminated embayment of Port Jackson (Australia) to distinguish source and possible adverse effects to benthic and pelagic animals. Mean concentrations in surficial sediment were <1, 14, 181, 141, 37, 290 and 685 μg g⁻¹ for Cd, Co, Cr, Cu, Ni, Pb and Zn, respectively. Sediment chemistry indicated these metals had multiple sources, i.e. the estuary, stormwater and industry. Mean total suspended solids (TSS) were 7, 17 and 20 mg L⁻¹ during quiescent, high-rainfall and heavy rainfall/high wind conditions, respectively, whereas SPM Cd, Co, Cr, Cu, Ni, Pb and Zn concentrations varied between 13–25, 166–259, 127–198, 38–82, 236–305 and 605–865 μg g⁻¹, respectively under these conditions. TSS and total water metal concentrations were lowest during quiescent conditions. High TSS and metal loads in surface water characterised high-rainfall events. Wind-induced resuspension contributed the greatest mass of SPM and metals to the water column. Benthic animals may be adversely affected by Pb and Zn in sediment. Total water Cu and Zn concentrations may pose a risk to filter-feeding animals in the water column due to resuspension of contaminated sediment.     

Metal fluxes to the sediments of the Moulay Bousselham lagoon,Morocco

The metal content in surface sediments (0–2 cm, 26 samples), in a sediment core (120, 1 cm slices), taken from Moulay Bousselham (Morocco) was investigated. Concentrations of Al, Fe, Mn, Pb, Zn, Cu, Ni, Cr, Cd, As, and Hg were evaluated in surface and cored sediments of Moulay Bousselham lagoon. Significantly high concentrations in μg g⁻¹ dw of Pb (31.7–6.2), Zn (758.9–167), Cu (310.7–22), Ni (96–10.5), Cr (113–18.9), Cd (0.84–0.02), As (1–0.1), and Hg (0.61–0.02) were found in sediment samples from Moulay Bousselham lagoon. Calculated enrichment factors [EF_Me = (Me/Al)_sample/(Me/Al)_background], using Al as a normalizer, and correlation matrices showed that metal pollution in Merja Zerga of Moulay Bousselham lagoon was the product of anthropogenic sources, while the metal content in Merja Kehla was of natural origins. The results suggest that a major change in the sedimentary regime of the lagoon, associated with internal trapping and re-distribution of heavy metal, has been occurring in the past few decades. The cause would appear to be the construction of a Nador Canal at the lagoon. Probable effects concentrations (PEC) were often exceeded for heavy metals in the lagoon sediments, especially for Zn, Cu, Ni, and Cr, and four stations, stations MZ-11, MZ-12, MZ-13, MZ-14, MZ-16, and MZ-17, had multiple metals at presumptively toxic levels. These comparisons suggest that sediment metal levels in the river are clearly high and probably pose an environmental risk at some stations. The levels of most of the metals were not greatly enriched, a consideration that is of the utmost importance when contamination issues are at stake. Metal concentrations found in Moulay Bousselham lagoon were comparable to aquatic systems classified as contaminated from other regions of the world.     

Heavy metals pollution in the soil of an irregular urban settlement built on a former dumpsite in the city of Tijuana, Mexico

The aim of this study was to evaluate soil pollution by heavy metals in an irregular settlement built on a dumpsite. The soil samples were analyzed for Cd, Cr, Cu, Pb and Ni. None of the concentrations found for the heavy metals analyzed were higher than the established Mexican official standards for contaminated soils. The mean concentrations found for the analyzed metals were as follows: 1.4 mg kg⁻¹ for Cd, 4.7 in mg kg⁻¹ for Cr, 304 mg kg⁻¹ for Cu, 74 mg kg⁻¹ for Pb and 6 mg kg⁻¹ for Ni. The results of the geoacummulation index values show that the site was very polluted with Cu and Pb (class 7), polluted to strongly polluted with Ni (class 4); moderately polluted to polluted with Cd (class 3), and moderately polluted with Cr (class 1). The correlation analysis shows a high correlation between Pb and Cu (r ² = 0.98), which would be explained if the main source of the polluting heavy metals was the result of electrical wire burning to recover Copper. Principal component analysis shows three principal components. The first main component (PC1) encompasses Cr, Cd, Pb and Cu. These heavy metals most likely have their origins from the open burning of municipal solid waste, tires and wire. The other two components are encompassed by Cr (PC2) and Ni (PC3). The sources of these pollutants are more likely related to the corrosion of junk metal objects and automobile use.     

Heavy metal concentrations and their possible sources in paddy soils of a modern agricultural zone,southeastern China

In a typical modern agricultural Zone of southeastern China, Haining City, 224 topsoil samples were collected from paddy fields to measure the total concentrations of copper (Cu), lead (Pb), zinc (Zn), cadmium (Cd), chromium (Cr), mercury (Hg), arsenic (As) and cobalt (Co). The total concentrations ranged from 15.30 to 78.40 mg kg⁻¹ for Cu, 20.10 to 41.40 mg kg⁻¹ for Pb, 54.98 to 224.4 mg kg⁻¹ for Zn, 0.04 to 0.24 mg kg⁻¹ for Cd, 54.90 to 197.1 mg kg⁻¹ for Cr, 0.03 to 0.61 mg kg⁻¹ for Hg, 3.44 to 15.28 mg kg⁻¹ for As, and 7.17 to 19.00 mg kg⁻¹ for Co. Chemometric techniques and geostatistics were utilized to quantify their spatial characteristics and define their possible sources. All eight metals had a moderate spatial dependency except that Pb had a strong spatial dependency. Both factor analysis and cluster analysis successfully classified the eight metals into three groups or subgroups, the first group included Cu, Zn and Cr, the second group included Cd, As and Co, and the last group included Pb and Hg. The Cu, Zn and Cr concentrations in majority samples were higher than their local background concentrations and they were highly correlated (r > 0.80), indicating that they had similar pollution source and anthropic factor controlled their spatial distribution; the Cd, As and Co concentrations in majority samples were lower than their local background concentrations, indicating that the source of these elements was mainly controlled by natural factors; the mean concentration of Pb exhibited generally low level, close to its local background concentration, the Hg concentration in about half of samples was higher than its local background concentration, and they were poor correlated with the other metals, indicating that the source of Pb and Hg was common controlled by natural factor and anthropic factor.     

Soil heavy-metal speciation and wheat phytotoxicity in the vicinity of an abandoned lead–zinc mine in Shangyu City,eastern China

Sixteen soil samples were collected from the vicinity of an abandoned lead–zinc mine in Shangyu City, eastern China, and the heavy-metal speciation and wheat phytotoxicity in the soils were studied. The results showed that the concentrations of free Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ were highly variable and ranged from <0.01 to 0.32, 0.06 to 10.62, <0.01 to 1.40 and 0.02 to 37.10 μmol l⁻¹, respectively. The concentrations of soluble Cu, Zn, Cd and Pb ranged from 0.38 to 3.24, 0.72 to 78.74, <0.01 to 1.95 and 0.15 to 639.34 μmol l⁻¹, respectively. The general trend of mean solid/liquid partition coefficient and percentage of free metal ion to total soluble metal concentration were Cu > Pb > Zn > Cd and Cd > Zn > Cu > Pb, respectively. Stepwise multiple linear regression with pH, log(total metal) and log(organic matter) showed that log(total metal) was an important factor that controlled log(free metal ion) and log(soluble metal). Of the variability in log(free Cu²⁺), log(free Cd²⁺) and log(free Pb²⁺), 55.2, 58.6 and 64.3% could be explained by log(total Cu), log(total Cd) and log(total Pb) alone, respectively. Of the variability in log(soluble Cu) and log(soluble Cd), 77.1 and 72.5% could be explained by log(total Cu) and log(total Cd) alone, respectively. Wheat root length was controlled by the various metals with different free and soluble concentrations, and 99.2% of the variability in root length could be explained by concentrations of free and soluble Pb, soluble Cu and total Zn in the soils.     

The hydrogeochemistry of a heavily used aquifer in the Mexican wine-producing Guadalupe Valley, Baja California

The Guadalupe Valley aquifer is the only water source for one of the most important wine industries in Mexico, and also the main public water supply for the nearby city of Ensenada. This groundwater is monitored for major ion, N-NO₃, P-PO₄, Fe, As, Se, Mo, Cd, Cu, Pb, Zn and Sb concentrations, as well as TDS, pH, dissolved oxygen and temperature. High concentrations of N-NO₃ (26 mg l⁻¹), Se (70 μg l⁻¹), Mo (18 μg l⁻¹) and Cu (4.3 μg l⁻¹) suggest that groundwater is being polluted by the use of fertilizers only in the western section of the aquifer, known as El Porvenir graben. Unlike the sites located near the main recharge area to the East of the aquifer, the water in El Porvenir graben has low tritium concentrations (<1.9 TU), indicating a pre-modern age, and thus longer water residence time. No significant variations in water quality (generally <10%) were detected throughout 2001–2002 in the aquifer, suggesting that reduced rainfall and recharge during this dry period did not significantly affect water quality. However, the wells nearest to the main recharge area in the Eastern aquifer show a slight but constant increase in TDS with time, probably as a result of the high (∼200 L S⁻¹) uninterrupted extraction of water at this specific recharge site. Relatively high As concentrations for the aquifer (10.5 μg l⁻¹) are only found near the northern limit of the basin associated with a geological fault.     

A study of arsenic,iron and other dissolved ion variations in the groundwater of Bishnupur District,Manipur, India

The presence of arsenic (As) in groundwater and its effect on human health has become an issue of serious concern in recent years. The present study assessed the groundwater quality of the Bishnupur District, Manipur, with respect to drinking water standards. Higher concentrations of pH, iron and phosphate were observed at several locations. Phosphate and iron levels were highest in the pre-monsoon, followed by monsoon and post-monsoon seasons. The arsenic concentrations were highest during post-monsoon (1–200 μg L⁻¹) as compared to pre-monsoon (1–108 μg L⁻¹) and monsoon (2–99 μg L⁻¹). Kwakta and Ngakhalawai show higher levels of arsenic concentration as compared to the prescribed World Health Organization (WHO) and Bureau of Indian Standards (BIS) norms. Arsenic showed a strong positive correlation with phosphate and negative correlation with sulphate, suggesting a partial influence of anthropogenic sources. The study suggests that the Bishnupur area has an arsenic contamination problem, which is expected to increase in the near future.     

Dominants and accumulation of rare earth elements in sediments derived from riparian and depressional marshes

The rare earth elements (REEs) in the sediments of the Xianghai wetlands were measured by inductively coupled plasma spectrometry. The REEs accumulation rates in two sedimentation cores derived from the riparian and depressional marshes were determined by ²¹⁰Pb method. The results showed that REEs concentrations in the Xianghai wetland sediments (∑REEs, 116 mg kg⁻¹) were lower than the corresponding values in Chinese soils (181 mg kg⁻¹) and river sediments (∑REEs, 158–191 mg kg⁻¹). Under alkaline conditions (with pH, 8.2–10.3), the light REEs were more enriched than the heavy REEs. Cerium is the predominant element, and accounts for 30–33% of the total REEs. REEs in the depressional marsh sediments were relatively high (∑REEs, 127 vs. 104 mg kg⁻¹), especially light REEs contents. A significantly positive correlation was found between the neighboring elements except Pr and Dy. The different types of vertical distribution of REEs between the riparian and the depressional marsh can partly result from long-term differing hydrological regimes. Generally, depressional marsh had accumulated much more REEs than riparian marsh (the mean accumulation rates of ∑REEs, 102.98 vs. 48.89 μg cm⁻² year⁻¹).     

Trace metals (Cd,Pb, Cu,Zn and Ni) in sediment of the submarine pit Dragon ear (Soline Bay,Rogoznica, Croatia)

Vertical profiles of trace metal (Cd, Pb, Zn, Cu, Ni) concentrations, organic matter content, carbonate content and granulometric composition were determined in two sediment cores from the submarine pit Dragon Ear (Middle Adriatic). Concentrations of the analyzed metals (Cd: 0.06–0.12 mg kg⁻¹, Pb: 28.5–67.3 mg kg⁻¹, Zn: 17.0-65.4 mg kg⁻¹, Cu: 21.1–51.9 mg kg⁻¹, Ni: 27.8–40.2 mg kg⁻¹) were in usual range for Adriatic carbonate marine sediments. Nevertheless, concentrations of Cu, Zn, and especially Pb in the upper layer of sediments (top 12 cm) were higher than in bottom layer, while Cd and Ni concentration profiles were uniform. Regression analysis and principal component analysis were used to interpret distribution of trace metals, organic matter and carbonate content in sediment cores. Results of both analysis showed that concentrations of all trace metals in the core below the entrance to the pit were significantly positively correlated with organic matter and negatively correlated with carbonate, while in the core more distant from the entrance only Pb showed significant positive correlation with organic matter. Obtained results indicated that, except for lead which was enriched in surface sediment, in the time of sampling (before the building of the nautical marina) investigated area belonged to unpolluted areas.     

Impact of slate quarrying on soil properties in semi-arid Mahendragarh in India

Slate quarrying in Mahendragarh district of Haryana state has resulted in changes in soil properties. Most of the mining area is devoid of vegetation. The soil in and around the mining area (0–1 km) is alkaline (pH 11.2–11.7) but non-saline (electrical conductivity < 4). The alkaline nature of the soil was attributed to the high concentrations of hydroxyl (OH⁻), carbonate (CO₃²⁻) and bicarbonate (HCO₃ ⁻) present in minerals of mined materials. Biotite, limonite, kaolinite, gibbsite, muscovite, geothite, dolomite and so on were the chief minerals added to soil through mining. The physical properties of soil, i.e. porosity, water-holding capacity (WHC), bulk density and particle density represented poor soil health in mining area (34.4, 29.8%, 1.636, 2.496 g/cc, respectively) and they improved with distance away from it (46.4, 38.3%, 1.070, 2.180 g/cc, respectively, at a distance of 1 km). Porosity and WHC were found to be a function of increased organic matter away from the mining area. CO₃²⁻, HCO₃⁻, phosphate (PO₄³⁻), lead (Pb) and iron (Fe) were more in mining area and decreased with distance. On the other hand, sodium (Na⁺), potassium (K⁺), chloride (Cl⁻), sulphate (SO₄²⁻), organic carbon, total Kjeldahl’s nitrogen, cation exchange capacity, chromium (Cr) and cadmium (Cd) increased with distance from mining area. High concentration of heavy metals in mining area was a cause of concern (0.93 μg/g Cd, 22.35 μg/g Cr, 26.25 μg/g Pb, 1,383.75 μg/g Fe). The change in physico-chemical properties could be because of the addition of chemical constituents that are a part of major minerals present in mined material. The soil away from mining area represented comparatively better properties.     

Interaction of acid mine drainage with waters and sediments at the Corona stream, Lousal mine (Iberian Pyrite Belt, Southern Portugal)

This study investigates the geochemical characteristics of the acid mine drainage discharged from the abandoned mine adits and tailing piles in the vicinity of the Lousal mine and evaluates the extent of pollution on water and on the stream sediments of the Corona stream. Atmospheric precipitation interacting with sulphide minerals in exposed tailings produces runoff water with pH values as low as 1.9–2.9 and high concentrations of (9,249–20,700 mg l⁻¹), Fe (959–4,830 mg l⁻¹) and Al (136–624 mg l⁻¹). The acidic effluents and mixed stream water carry elevated Cu, Pb, Zn, Cd and As concentrations that exceed the water quality standards. However, the severity of contamination generally decreases 4 km downstream of the source due to mixing with fresh waters, which causes the dilution of dissolved toxic metals and neutralization of acidity. Some natural attenuation of the contaminants also occurs due to the general reduced solubility of most trace metals, which may be removed from solution, by either co-precipitation or adsorption to the iron and aluminium precipitates.     

Geo-chemical Behavior of Uranium in the Sambhar Salt Lake, Rajasthan (India): Implications to "Source" of Salt and Uranium "Sink"

Among several salt lakes in the Thar Desert of western India, the Sambhar is the largest lake producing about 2 × 10⁵ tons of salt (NaCl) annually. The “lake system” (lake waters, inflowing river waters, and sub-surface brines) provides a unique setting to study the geo-chemical behavior of uranium isotopes (²³⁸U, ²³⁴U) in conjunction with the evolution of brines over the annual wetting and evaporation cycles. The concentration of ²³⁸U and the total dissolved solids (TDS) in lake water increase from ~8 μg L⁻¹ and ~8 g L⁻¹ in monsoon to ~1,400 μg L⁻¹ and 370 g L⁻¹, respectively, during summer time. The U/TDS ratio (~1 μg g⁻¹ salt) and the ²³⁴U/²³⁸U activity ratio (1.65 ± 0.05), however, remain almost unchanged throughout the year, except when U/TDS ratio approaches to 3.8 at/or beyond halite crystallization. These observations suggest that uranium behaves conservatively in the lake waters during the annual cycle of evaporation. Also, uranium and salt content (TDS) are intimately coupled, which has been used to infer the origin and source of salt in the lake basin. Furthermore, near uniform ratios in evaporating lake waters, when compared to the ratio in seawater (~0.1 μg g⁻¹ salt and 1.14 ± 0.02, respectively), imply that aeolian transport of marine salts is unlikely to be significant source of salt to the lake in the present-day hydrologic conditions. This inference is further consistent with the chemical composition of wet-precipitation occurring in and around the Sambhar lake. The seasonal streams feeding the lake and groundwaters (within the lake’s periphery) have distinctly different ratios of U/TDS (2–69 μg g⁻¹ salt) and ²³⁴U/²³⁸U (1.15–2.26) compared to those in the lake. The average U/TDS ratio of ~1 μg g⁻¹ salt in lake waters and ~19 μg g⁻¹ salt in river waters suggest dilution of the uranium content by the recycled salt and/or removal processes presently operating in the lake during the extraction of salt for commercial use. Based on mass-balance calculations, a conservative estimate of "uranium sink" (in the form of bittern crust) accounts for ~5 tons year⁻¹ from the lake basin, an estimate similar to its input flux from rivers, i.e., 4.4 tons year⁻¹.     

High cadmium concentrations in Jurassic limestone as the cause for elevated cadmium levels in deriving soils: a case study in Lower Burgundy,France

Cadmium (Cd) is a highly toxic element and its presence in the environment needs to be closely monitored. Recent systematic surveys in French soils have revealed the existence of areas in eastern and central France, which show systematically high cadmium concentrations. It has been suggested that at least part of these anomalous levels are of natural origin. For the Lower Burgundy area in particular, a direct heritage from the Jurassic limestone bedrock is highly suspected. This potential relationship has been studied in several localities around Avallon and this study reports new evidence for a direct link between anomalously elevated cadmium contents of Bajocian and Oxfordian limestone and high cadmium concentrations in deriving soils. Soils in this area show cadmium concentrations generally above the average national population values, with contents frequently higher than the ‘upper whisker’ value of 0.8 μg g⁻¹ determined by statistical evaluation. In parallel, limestone rocks studied in the same area exhibit cadmium concentrations frequently exceeding the mean value of 0.030–0.065 μg g⁻¹ previously given for similar rocks by one order of magnitude, with a maximum of 2.6 μg g⁻¹. Mean ratios between the cadmium concentrations of limestone bedrock and deriving soils (Cd_soil/Cd_rock), calculated for different areas, range from 4.6 to 5.7. Calculations based on the analyses of both soils from a restricted area and fragments of bedrock sampled in the immediate vicinity of high-concentration soils are around 5.5–5.7. Cd_soil/Cd_rock is useful in determining the potential of soils in Lower Burgundy to reflect and exacerbate the high concentrations of cadmium present in parent bedrocks.     

Sorption Model for Dissolved and Leachable Particulate Aluminium in the Great Ouse Estuary, England

The behaviour of dissolved Al in the Great Ouse estuary, in particular with respect to salinity, is complex. There is, however, evidence from field data as well as laboratory mixing experiments to suggest that flocculation and sorption mechanisms play important roles affecting the concentrations of dissolved Al during the early stages of estuarine mixing. In contrast, a near-buffering of dissolved Al occurs in the entire stretch of the estuary (salinity >0.2) with concentrations varying around 1.4 μg l⁻¹. This distribution and lack of variation with salinity is attributable to sorption processes which might dominate over other processes in these turbid estuarine waters (suspended particulate load 48–888 mg l⁻¹) impacting dissolved Al levels. Sorption models have been developed for both dissolved and leachable particulate Al concentrations in these waters. These observations provide compelling evidence of sorption processes that might be important in the geochemistry of Al in estuarine waters.