Concentrations Of Most Metals Research Articles

Bioavailability Studies of Metals in Surface Water of River Challawa, Nigeria

Due to industrialization of Kano City, more industries located within Challawa industrial estate have discharged waste informed of effluents into River Challawa, which is the main source of irrigation water for agricultural land. Hence, this study is aim at assessing the bioavailable fractions of the metals zinc (Zn), lead (Pb), copper (Cu), chromium (Cr) and cadmium (Cd) in surface water of river Challawa, Kano, Nigeria, across seasons. It was found that the concentrations of most metals increased significantly during the dry seasons. Concentrations of Cu and Zn are within the standard limits of EPA and WHO for these metals in drinking water while Pb, Cr, and Cd have their concentrations higher than EPA and WHO standard limits. Analysis of relationship between metals indicated significant positive correlation (P<0.05) between Cr and Zn, in all seasons with exception of warm and dry season. This might explain the consistent variation of these metals in the sites in a particular season. Also, significant negative correlation was observed between Cd and Cu (hot and dry season). The chemical fractionation trends were found to be dominated by particulate fractions of metals studied except Zn (cool and dry season) and Cd. The highest percentages of all metals analysed were found in the particulate fraction with exception of Cd. This could reflect less availability of this metal to the immediate environment. However, availability of metals such as Cd, Cr, and Pb in the dissolved and mobile fractions reflects the greater tendency to become available to the aquatic system and through the food chain to man.

Wetlands as long-term sources of metals to receiving waters in mining-impacted landscapes

Wetlands are prevalent in the Sudbury, Ontario region and often operate at the interface between terrestrial and aquatic ecosystems, modifying water chemistry and potentially affecting the recovery of impacted lakes. The deposition of metals and sulphur in Sudbury in 2010–2012 was far below that reported in the 1970's, but still higher than background values. Wetlands in the area have accumulated large quantities of metals, and high concentrations of these metals in streams occurred primarily in response to SO4-related acidification events or associated with high dissolved organic carbon production in early summer. Concentrations of most metals in streams exceeded provincial guidelines and fluxes of some metals from catchments exceeded deposition inputs to lakes by as much as 12 times. The release of metals long after emissions reductions have been achieved must be considered in ecosystem recovery studies, particularly as dry conditions may become more prevalent in boreal regions affected by mining.

Assessment of exposure to trace metals in a cohort of pregnant women from an urban center by urine analysis in the first and third trimesters of pregnancy

Prenatal exposure to trace metals, whether they are essential, non-essential, or toxic, must be assessed for their potential health effects in the offspring. Herein is reported an approach to this end which involved collection of urine samples during the first and third trimesters of pregnancy from 489 mothers from Sabadell (Catalonia, Spain), a highly industrialized town. These samples were analyzed for cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), selenium (Se), arsenic (As), molybdenum (Mo), cadmium (Cd), antimonium (Sb), cesium (Cs), thallium (Tl), and lead (Pb). An acid digestion method was developed and validated for inductively coupled plasma quadruple mass spectrometry (Q-ICP-MS) analysis of these 12 metals. The median concentrations of metals ranged from 0.13 to 290 μg/g creatinine, the highest levels were found for Zn and the lowest for Th. The mean concentrations of most metals except As, Ni, Th, and Pb showed statistically significant differences between both trimesters. The concentrations of Mo, Se, Cd, Cs, and Sb were higher in the first than in the third trimester, whereas the opposite was found for Co, Cu, and Zn. The concentrations of all metals in both sampling periods showed statistically significant correlations (p<0.01 for Mo and Cu, p<0.001 for the others). The significant correlations of metal urine concentrations in the first and third trimesters of pregnancy suggest that the observed differences between both periods are related to physiological changes. Accordingly, the measured urine concentrations during either the first or third trimesters can be used as estimates of exposure during pregnancy and can serve as markers for prenatal intake of these metals in the studied cohort.

Metals in benthic macrofauna and biogeochemical factors affecting their trophic transfer to wild fish around fish farm cages

Benthic macroinvertebrates and wild fish aggregating in the vicinity of four Mediterranean fish farms were sampled. Concentrations of metals and other elements were measured in macrofaunal taxa and in fish tissues (muscle, liver, gills, bone, gonad, stomach, intestine, and stomach content). Biological and geochemical characteristics play an important role in metal accumulation in benthic invertebrates, and consequently in metal transfer to higher trophic levels. Macroinvertebrates accumulated lower concentrations of most metals and elements than their respective sediment, except As, P, Na, Zn and Cd. Elemental concentrations of benthic organisms increased with increasing sediment metal content, except Cd, and with % silt, refractory organic matter and chlorophyll-a of sediment due to the influence of sediment geochemistry on metal bioavailability. Tolerant species were found to accumulate higher concentrations of most metals and elements, except for Cd, than equilibrium species. The ecological and morphological characteristics of the benthic invertebrates can affect the bioaccumulation of metals and elements in macrobenthos. Hg and P were found to increase their concentrations from zoobenthos to wild fish aggregating around fish cages feeding on macrofauna.

Red bed and basement sourced fluids recorded in hydrothermal Mn–Fe–As veins, Sailauf (Germany): A LA-ICPMS fluid inclusion study

The hydrothermal Mn–Fe–As vein mineralization at Sailauf (Germany) hosts a complex sequence of oxide and carbonate minerals that record a protracted fluid history. The mineralization is related to a major unconformity that separates Permian (Zechstein) sedimentary rocks from underlying Variscan crystalline basement. The hydrothermal veins contain two principal mineralization stages, which are Mn oxides associated with calcite and hematite associated with Mn-calcite. The fluid evolution of the hydrothermal system has been reconstructed from fluid inclusion petrography, microthermometry, and LA-ICPMS microanalysis, coupled with stable isotope geochemistry of carbonate and oxide minerals. The fluid inclusions are high salinity sodic–calcic brines and the bulk fluid properties show no major differences between the Mn oxide and the hematite stage. LA-ICPMS analysis of major and trace elements demonstrates that the mineralization formed from chemically distinct fluid pulses characterized by variations in their K, Li, B, Pb and Zn concentrations. The fluid that precipitated the Mn oxide stage has anomalous Pb/Zn and Li/B ratios, which closely resemble fluids found in fracture fillings in red beds of the Permian Rotliegend basin. By contrast, the fluids associated with the hematite stage have Pb/Zn and Li/B ratios typical of crustal fluids that were derived from interaction with crystalline basement. Both fluids possess characteristic element ratios including Cl/Br, but variable absolute concentrations of most metals. This suggests that both fluids were modified by mixing with a common metal-depleted brine that had a similar Cl/Br ratio, most likely a formation water from the overlying Zechstein sedimentary rocks. The Sailauf mineralization provides insight into the protracted post-Variscan fluid evolution at the basement–cover interface. The compositionally anomalous fluid that precipitated the Mn oxides is comparable to brines derived from interaction with red beds and likely represents the ore fluid of Kupferschiefer-type sediment-hosted Cu deposits. Conversely, the fluid that deposited the hematite mineralization resembles fluids that typically form basement- and sediment-hosted Pb–Zn deposits.

Effects of food limitation on 9 metal concentrations in liver and polycyclic aromatic hydrocarbon metabolites in bile of juvenile turbot (Scophthalmus maximus) previously exposed to contaminated sediments

A 2-step experimental design was employed in the present study on juvenile turbot (Scophthalmus maximus): 1) juveniles were exposed for 26 d to 2 contaminated sediments and a reference one, and 2) they were transferred in clean seawater with clean sediment for 35 d, feeding fish once a day, twice a week, or once a week. Fish exposed to contaminated sediments presented a significant increase of hepatic Cd, Cu, and Pb concentrations compared with the reference condition after the 26-d exposure. Higher fluorescence signals of polycyclic aromatic hydrocarbon (PAH) metabolites were found in bile from turbot exposed to contaminated sediments for 26 d compared with reference. These signals returned to values similar to reference fish after depuration whatever the food quantity. The metal bioaccumulation of Cd, Cu, and Pb was no longer observed after 35-d depuration with once-a-day feeding but was still found with restricted feeding conditions. Results on reference fish also showed significantly higher concentrations of most metals analyzed in fish fed twice a week and once a week compared with fish fed once a day. These results could be related to a decrease of fish hepatosomatic index with food limitation and, thus, a dilution effect on metal concentrations. The present study clearly demonstrates that changes in feeding status have significant effects on metal concentrations in fish and no observed effect on PAH metabolites.

Partitioning of heavy metals in sub-surface flow treatment wetlands receiving high-strength wastewater

The retention of heavy metals at two pilot-scale treatment wetlands (TWs), consisting of two vertical flow beds (VSSF) followed by a horizontal flow bed (HSSF) was studied. The TWs received high-strength wastewater: reject waters from sewage sludge centrifugation (RW) and landfill leachate (LL). The concentrations of the metals Fe, Mn, Zn, Al, Pb, Cu, Cd, Co, and Ni were measured in treated wastewater, substrate of the beds and in plant material harvested from the beds (separately in above ground (ABG) parts and below ground (BG) parts). The TWs differed in metals retention. In the RW treating TW the metal removal efficiencies varied from 27% for Pb to over 97% for Fe and Al. In the LL treating system the concentrations of most metals decreased after VSSF-1 and VSSF-2 beds; however, in the outflow from the last (HSSF) bed, the concentrations of metals (apart from Al) increased again, probably due to the anaerobic conditions at the bed. A major removal pathway was sedimentation and adsorption onto soil substrate as well as precipitation and co-precipitation. In the LL treating facility the plants contained substantially higher metal concentrations in BG parts, while the upward movement of metals was restricted. In the RW treating facility the BG/ABG ratios were lower, indicating that metals were transported to shoots.

Metal accumulation in wild nine-banded armadillos

Nine-banded armadillos (Dasypus novemcinctus) are widespread and abundant New World mammals with a lifestyle that entails prolonged, intimate contact with soils. Thus, armadillos would seem a promising candidate as a sentinel species to monitor chemical contamination in terrestrial ecosystems. Surprisingly, there have been virtually no toxicology studies on armadillos. Here, we provide the first analysis of metal contaminants for wild armadillos. Liver tissues were obtained from 302 armadillos collected at 6 sites in Georgia and Florida, USA that varied in their extent of human disturbance, from rural pine plantations to highly modified military/space installations. Data were stratified by age (juvenile and adult), sex, and site. Temporal (yearly) variation was examined at two of the sites that were sampled over three consecutive years. Concentrations of aluminum, cadmium, copper, nickel, lead, and zinc were measured in liver samples from each site. Although reference levels are not available for armadillos, accumulated metal concentrations were comparable to those reported for other mammals. We found no evidence of sex or age differences in the concentrations of any metal, except for Cd (age) and Pb (sex and age). However, concentrations of most metals varied substantially across sites and over time. Finally, concentrations of many metals were positively correlated with one another, suggesting that they likely co-occurred in some areas. Collectively, this study indicates the utility of armadillos as a sentinel species for studies of metal contamination in terrestrial systems, and highlights the need for further studies of other toxicants in these animals.

Evaluation of trace metals bioavailability in Japanese river waters using DGT and a chemical equilibrium model

To develop efficient and effective methods of assessing and managing the risk posed by metals to aquatic life, it is important to determine the effects of water chemistry on the bioavailability of metals in surface water. In this study, we employed the diffusive gradients in thin-films (DGT) to determine the bioavailability of metals (Ni, Cu, Zn, and Pb) in Japanese water systems. The DGT results were compared with a chemical equilibrium model (WHAM 7.0) calculation to examine its robustness and utility to predict dynamic metal speciation. The DGT measurements showed that biologically available fractions of metals in the rivers impacted by mine drainage and metal industries were relatively high compared with those in urban rivers. Comparison between the DGT results and the model calculation indicated good agreement for Zn. The model calculation concentrations for Ni and Cu were higher than the DGT concentrations at most sites. As for Pb, the model calculation depended on whether the precipitated iron(III) hydroxide or precipitated aluminum(III) hydroxide was assumed to have an active surface. Our results suggest that the use of WHAM 7.0 combined with the DGT method can predict bioavailable concentrations of most metals (except for Pb) with reasonable accuracy.

Environmental toxicity and radioactivity assessment of a titanium‐processing residue with potential for environmental use

Thorough examination of the physicochemical characteristics of a Ti-processing residue was undertaken, including mineralogical, geochemical, and radiochemical characterization, and an investigation of the environmental toxicity of soft-water leachate generated from the residue. Concentrations of most metals measured in the leachate were low; thus, the residue is unlikely to leach high levels of potentially toxic elements on exposure to low-ionic strength natural waters. Relative to stringent ecosystem health-based guidelines, only chromium concentrations in the leachate exceeded guideline concentrations for 95% species protection; however, sulfate was present at concentrations known to cause toxicity. It is likely that the high concentration of calcium and extreme water hardness of the leachate reduced the bioavailability of some elements. Geochemical modeling of the leachate indicated that calcium and sulfate concentrations were largely controlled by gypsum mineral dissolution. The leachate was not toxic to the microalga Chlorella sp., the cladoceran Ceriodaphnia dubia, or the estuarine bacterium Vibrio fischeri. The Ti-processing residue exhibited an absorbed dose rate of 186 nGy/h, equivalent to an annual dose of 1.63 mGy and an annual effective dose of 0.326 mGy. In summary, the results indicate that the Ti-processing residue examined is suitable for productive use as an environmental amendment following 10 to 100 times dilution to ameliorate potential toxic effects due to chromium or sulfate.

Dissolved heavy metals in the Tigris River (Turkey): spatial and temporal variations

Multivariate statistical techniques, such as analysis of variance, cluster analysis (CA), correlation analysis, principal component analysis (PCA), and factor analysis (FA), were applied to determine the spatial and temporal variations of dissolved heavy metals in the Tigris River at 7 different sites spread over the river stretch of about 500km during the period of February 2008 to January 2009. The results indicated that Fe, Cr, and Ni were the most abundant elements in the river water, whereas Cd and As were the less abundant. Cu, Fe, Ni, and Zn showed significant spatial variations, reflecting the influence of anthropogenic activities. The lowest total concentration of heavy metals was found at site 2 downstream of the Dicle Dam due to clean water from the dam. The concentrations of most metals were found lower when compared with results of previous studies due to reduction of the activity of the copper mine plant and the construction of two dams on the river. The lowest total concentrations were determined in February due to high precipitation and snow melts. Hierarchical agglomerative CA classified all the sampling sites into three main groups of spatial similarities. Clusters 1 (Maden and Bismil), 2 (Cizre), and 3 (Eğil, Diyarbakır, Batman, and Hasankeyf) corresponded to moderate polluted and relatively low polluted regions, respectively. PCA/FA, CA, and correlation analysis suggest that Cu, Ni, and Zn are controlled by anthropogenic sources.

Seasonal variation of trace metal (Mn, Zn, Cu, Pb, Co, Cd) concentrations in compartments of the seagrass Cymodocea nodosa

Abstract The concentrations of six trace metals (Mn, Zn, Cu, Pb, Co and Cd) in five compartments (blades, sheaths, vertical rhizomes, main axis plus additional branches and roots) of the seagrass Cymodocea nodosa from the Gulf of Thessaloniki, Greece were determined monthly, together with potential associated variables (climate variables, sediment metal concentrations, plant compartment biomass, size and age). Uni- and multivariate data analyses were applied. Univariate analyses showed that leaf blades displayed the highest annual mean concentration of most metals (Mn, Zn, Pb, Co, Cd) analyzed, whereas sheaths had the highest Cu concentration; metal concentrations in blades generally showed a wider monthly variability than those in the other plant compartments, and especially roots. The multivariate pattern of metals in leaf blades showed a seasonal periodicity that appeared to be governed by the cumulative effect of plant growth dynamics and sediment metal content. In particular, most metal concentrations increased from April onwards, with enhancement of blade biomass, size and age, and remained high throughout the blade growing season, whereas Cu concentration showed the opposite pattern; an additional increase in blade Zn concentration during early winter coincided with a marked increase in sediment Zn content. The multivariate patterns of metals in the other plant compartments showed no distinct seasonality and were not markedly related to the examined variables. These findings are not consistent with the assumption that metals in seagrass tissues display an overall seasonal trend of markedly higher levels during the cold period. The present study stresses the need for more knowledge on metal seasonality in seagrass compartments and on the associated variables.

A novel fractionation approach for water constituents – distribution of storm event metals

A novel fractionation method, based on both particle size and settling characteristics, was employed to examine metal distributions among five fractions. In-stream and stormwater runoff samples were collected from four land use types: highway, urban, agricultural (storm event and irrigation), and natural. Highway samples contained the highest dissolved concentrations for most metals, and freshwater ambient water quality criteria were exceeded for Cd, Cu, Pb, and Zn in the first storm of the water year. Anthropogenic sources were indicated for Cu, Zn, Cd, and Pb in highway and urban samples, and total metal loadings (mg km(-2)) were observed to be as follows: highway > urban > agricultural storm event ∼ natural > agricultural irrigation. Notably, ∼10-fold higher suspended solids concentration was observed in the agricultural storm event sample, and suspended solids-associated metals were correspondingly elevated. Distribution coefficients revealed the following affinities: Zn, Ni, Cd, and Pb to large dense particles; and Cu, Zn, Cr, Ni, and Pb to colloidal organic matter.

Metal levels in sediments and transplanted mussels in Pagassitikos Gulf (Aegean Sea, Eastern Mediterranean)

Metal concentrations were determined in surface sediments and transplanted mussels in a shallow semi-enclosed bay, Pagassitikos Gulf, Aegean Sea. Cu, Zn, Pb, Hg, and As levels in sediments were enriched close to point sources of pollution, i.e., Volos Port and cement plant. Fe, Mn, Cr, and Ni spatial distributions in sediments were rather uniform with increasing concentrations towards deeper sites, suggesting natural enrichment, whereas levels found in the port, although elevated, were not the highest in the study area. Spatial variations in concentrations of most metals in mussels transplanted nearshore were generally in accordance to those in sediments, with the highest Fe, Mn, Cr, Ni, and Cu levels in the port and the highest Hg levels close to the cement plant. Concentrations of metals in sediments and transplanted mussels were comparable to those reported in Mediterranean areas. Results indicate that pollution point sources contribute to anthropogenic metal enrichment in the study area.

Metal accumulation in fish from different zones of a large, shallow freshwater lake

Metal (Cd, Pb, Cr, Ni, Mn, Cu, and Zn) concentrations in different fish species sampled from two distinct (phytoplankton- and macrophyte-dominated) lake zones of a large, shallow freshwater lake, Taihu Lake, were investigated. Concentrations of most metals in muscle of the small-sized fish (Protosalanx hyalocranius, Pseudorasbora parva, and Rhodeus ocellatus) were always significantly higher than those of the large-sized (Carassius auratus, Cyprinus carpio, and Aristichthys nobilis) and carnivorous fish (Pelteobagrus fulvidraco, Cultrichthys erythropterus, and Erythroculter ilishaeformis). Metal accumulation in the small-sized fish from the phytoplankton-dominated lake zone was always greater than those from the macrophyte-dominated lake zone in summer. However, no significant differences were observed between the two lake zones for most metals in the small-sized fish collected in winter. Metal accumulation in gills, liver, and intestine of the large-sized fish from the phytoplankton-dominated lake zone was generally greater than those from the macrophyte-dominated lake zone in summer. The presence of distinct ecological regions in the lake might affect the metal distribution in the small-sized or large-sized fish. For the carnivorous fish, however, metal concentrations in fish tissues from the two different lake zones were not significantly different, suggesting that metal accumulation in carnivorous fish might be less influenced by the ecological status of the lake.

Distribution and Bioavailability of Metals in Subsidence Land in a Coal Mine China

Land subsidence in coal mine would change the type of soil so that it influences the distribution and bioavailability of metals. The results show that the total metal concentration was in the range from 0.41 ± 0.26 mg/kg (Cd) to 94.16 ± 12.06 mg/kg (Zn) and Cd was the serious pollution metal. In spatial, the concentration of most metals (except Sb) was highest in perennial waterlogged zone while was lowest in no waterlogged zone, which implied that the perennial waterlogged zone was a sink of metals in coal mine area. However, the bio-available fraction of metals was lowest in perennial waterlogged zone.

The chemistry of trace elements in surface geothermal waters and steam, Iceland

The geochemistry of trace elements in surface geothermal fluids in Iceland was studied. The sampled fluids included hot springs, mud pots, steam vents and soil solutions with temperatures ranging from 4 to 100°C, pH between 2.01 and 9.10 and total dissolved solids between 86 and 4375ppm. The surface geothermal waters may be categorized into three groups based on their chemical composition, namely NaCl waters, steam-heated acid-sulfate waters and mixed waters. NaCl waters with pH >8 are considered to represent aquifer geothermal fluids that have undergone boiling in the upflow. They contained only low concentrations of most metals, <0.1ppb of Cd and Co, <1ppb of Ni, Pb, Cr and Cu and <10ppb of Zr, V and Zn, whereas somewhat higher concentrations of Ba (0.06–15ppb), Sr (1.2–107ppb), Cs (0.08–19ppb), Rb (7.1–163ppb), Li (18–380ppb), As (<0.2–252ppb), Sb (0.05–40ppb), Mo (0.16–50ppb), W (2.4–88ppb), Mn (0.1–163ppb), Fe (1.8–157ppb) and Al (21–1510ppb) were found. Steam-heated acid-sulfate waters typically had a pH <4. They form by condensation and mixing of steam in shallow non-thermal water. Compared to NaCl waters, steam-heated acid-sulfate waters typically had high concentrations of Al (0.02–267ppm), Fe (0.66–360ppm), Mn (44–4231ppb), V (1.1–1120ppb), Cr (0.15–660ppb), Zn (3.1–633ppb), Ni (0.20–192ppb), Cu (0.09–121ppb), Co (0.02–90ppb), Ba (1.0–60ppb) and Sr (2.8–316ppb), whereas concentrations of Li (<0.03–57ppb), Cs (<0.01–0.77ppb), Rb (0.12–24ppb), As (<0.1–61ppb), Mo (<0.01–14ppb), Sb (<0.01–25ppb) and W (<0.01–6.9ppb) were lower. Mixed waters are mixtures between NaCl waters, steam-heated acid-sulfate waters and non-thermal water, and showed chemical characteristics of these end-member waters. The steam discharged by the steam vents was found to carry trace elements including B, As, Cu and Cd in the ppt to ppb concentration range. The geochemistry of Li, Cs, Rb, As, Mo, Sb and W in surface geothermal waters was dominated by rock leaching, together with mixing of condensed steam and non-thermal surface waters at a low pH and with incorporation into secondary minerals including aluminum silicates and sulfides under alkaline conditions. In contrast, aqueous Ba and Sr concentrations were largely influenced by the formation of secondary minerals including sulfates, carbonates and Ca-minerals in all water types. At a low pH, the behavior of Al, Fe, Mn, Co, Ni, Zn, Cd, Cu, Pb, Cr and V was generally dominated by rock leaching, though occasionally by mineral precipitation in the case of Fe, Al, Cu, Co and Zr. With increasing pH, these metals became immobile due to their incorporation into secondary sulfide (Fe, Co, Ni, Zn, Cd, Cu, Pb), (hydr)oxide (Al, Fe, Cr, V, Zr) and aluminum- silicate (Al) minerals limiting their aqueous concentrations.

Distribution of heavy metals in tidal flat sediments and their bioaccumulation in the crab Macrophthalmus japonicas in the coastal areas of Korea

Levels of heavy metal concentrations in crab, Macrophthalmus japonicas, and in surface sediments from tidal flats in the western and southern coastal area of the Korean Peninsula were assessed in terms of metal pollution and bioaccumulation. Metal concentrations in tidal flat sediments varied considerably at various sites, mostly because of the high variability of pollutants commonly found in the area. Levels of some metals in the sediments exceeded the minimum concentration guidelines effects-range, leading to the expectation of adverse biological effects. The pollution index associated with different metals varied greatly and indicated that As, Cr, Cu and Pb contamination is relatively high in the coastal areas of Korea. The combined pollution index ranged from 0.49 to 2.88 and spatial distribution analysis indicated that runoff from an abandoned metal mine and from a variety of other industries are the main sources of metal pollution. Bulk metal concentrations in crabs showed no significant relationship with size but significant differences with sex: levels of most non-essential metals were significantly higher in females than in males, but levels of essential metals such as Cu and Zn showed no significant difference associated with sex. The concentrations of most metals in crabs were significantly positively related to those in sediments, indicating the usefulness of crabs as a bioindicator for metal pollution assessments in tidal flats. Bioaccumulation factors (BAF) were in the order of Cu>Cd>Zn>As>Ni>Pb>Cr and tended to be significantly inversely related to exposure concentrations. This indicates that other factors, besides BAF, also need to be taken into account when assessing the hazard potential of particular metals.

Relationship between pollutant content and ecotoxicity of sewage sludges from Spanish wastewater treatment plants

Chemical and ecotoxicological properties of 28 sewage sludge samples from Spanish wastewater treatment plants were studied in order to assess their suitability for agricultural purposes. Sludge samples were classified into five categories according to specific treatment processes in terms of digestion (aerobic/anaerobic) and drying (mechanical/thermal). Composted samples, as indicative of the most refined process, were also considered. Sludges were subjected to physical–chemical characterization, being the sludge stabilization degree respirometrically assessed. The concentrations of seven metals (Cd, Cr, Cu, Pb, Zn, Ni, Hg) and organic substances (phenolic compounds, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polychlorinated naphthalenes, polybrominated diphenyl ethers, and perfluorinated compounds) were determined. Finally, two ecotoxicological tests were performed: i) Microtox® toxicity test with Vibrio fischeri, and ii) root elongation test with Allium cepa, Lolium perenne and Raphanus sativus seeds. Significant differences were found in the following parameters: dry matter, electrical conductivity, nitrogen, organic matter and its stability, phytotoxicity and ecotoxicity, depending on the sludge treatment. In turn, no significant differences were found between categories in the concentrations of most metals and organic pollutants, with the exception of free phenolic compounds. Furthermore, no correlation between total heavy metal burden and ecotoxicity was observed. However, a good correlation was found between phenolic compounds and most ecotoxicological tests. These results suggest that sludge stability (conditioned by sludge treatment) might have a greater influence on sludge ecotoxicity than the pollutant load. Composting was identified as the treatment resulting in the lowest toxicity.

A Preliminary Assessment of Metal Bioaccumulation in the Blue Crab, Callinectes danae S., from the Sao Vicente Channel, Sao Paulo State, Brazil

The concentrations of metals in tissues of Callinectes danae were evaluated, aiming to determine the bioaccumulation process of this species. Gills presented the highest mean concentrations for most metals, except for Hg (<LOD) and Zn (13.293μgg(-1)). According to results of the principal component analysis, the type of tissue was distinguished due to the concentrations of metals. An evaluation of individuals from other sites of the Santos Estuarine System (where the Sao Vicente Channel is included) would be important to confirm if this pattern of bioaccumulation can be extended to the population of C. danae of this estuary.