The influence of time on lead toxicity and bioaccumulation determined by the OECD earthworm toxicity test

Internationally agreed standard protocols for assessing chemical toxicity of contaminants in soil to worms assume that the test soil does not need to equilibrate with the chemical to be tested prior to the addition of the test organisms and that the chemical will exert any toxic effect upon the test organism within 28 days. Three experiments were carried out to investigate these assumptions. The first experiment was a standard toxicity test where lead nitrate was added to a soil in solution to give a range of concentrations. The mortality of the worms and the concentration of lead in the survivors were determined. The LC50s for 14 and 28 days were 5311 and 5395 microgPb g(-1)soil respectively. The second experiment was a timed lead accumulation study with worms cultivated in soil containing either 3000 or 5000 microgPb g(-1)soil. The concentration of lead in the worms was determined at various sampling times. Uptake at both concentrations was linear with time. Worms in the 5000 microg g(-1) soil accumulated lead at a faster rate (3.16 microg Pb g(-1)tissue day(-1)) than those in the 3000 microg g(-1) soil (2.21 microg Pb g(-1)tissue day(-1)). The third experiment was a timed experiment with worms cultivated in soil containing 7000 microgPb g(-1)soil. Soil and lead nitrate solution were mixed and stored at 20 degrees C. Worms were added at various times over a 35-day period. The time to death increased from 23 h, when worms were added directly after the lead was added to the soil, to 67 h when worms were added after the soil had equilibrated with the lead for 35 days. In artificially Pb-amended soils the worms accumulate Pb over the duration of their exposure to the Pb. Thus time limited toxicity tests may be terminated before worm body load has reached a toxic level. This could result in under-estimates of the toxicity of Pb to worms. As the equilibration time of artificially amended Pb-bearing soils increases the bioavailability of Pb decreases. Thus addition of worms shortly after addition of Pb to soils may result in the over-estimate of Pb toxicity to worms. The current OECD acute worm toxicity test fails to take these two phenomena into account thereby reducing the environmental relevance of the contaminant toxicities it is used to calculate.     

Macrobenthic community in the Douro estuary: relations with trace metals and natural sediment characteristics

The relationship between macrobenthic community structure and natural characteristics of sediment and trace metal contamination were studied in the lower Douro estuary (Portugal, NW, Iberian Peninsula), using an innovative threefold approach (SQG, Sediment Quality Guidelines), metal normalization to Fe, and macrobenthic community structure. This study allowed detection of a clear signature of anthropogenic contamination, in terms of Zn, Cu, Pb, and Cr in the north bank of the estuary, which experiences high urban pressure. Using the SQG approach, metal concentrations above ERM (effects range-median) were observed only at one sampling station, but several stations had levels above ERL (effects range-low). The macrobenthic community had a low diversity, with only 19 species found in the entire estuarine area, dominated by opportunistic species. The granulometric distribution of the sediments (estimated from the combination of organic matter, Fe and Al) seemed to be the major structuring factor for the communities, establishing the natural macrobenthic distribution pattern. The metals (Zn, Cu, Pb, and Cr) seemed to act as a disturbing factor over the natural distribution, with deleterious consequences for the macrobenthic communities.     

Trace metal behaviour in the Conwy estuary,North Wales

The distribution of trace metals Zn, Ni, Mn, Fe, Cu, Pb, Cd and Cr between suspended particulate matter (SPM) and water in the Conwy estuary, North Wales, has been studied in three surveys in 1998. Dissolved Cu and Mn showed some monthly variations. Most of the dissolved trace metals displayed a negative association with salinity, indicating rivers as a major source of inputs for them. Particulate Zn, Mn and Fe showed a decreasing concentration seaward, whilst the levels of Ni, Cu, Cr and Pb increased with salinity. SPM concentration was the most important variable significantly related to trace metal concentrations in SPM, with an inverse relationship between the two parameters. This was explained by the relative enrichment of trace metals in fine particles at low SPM concentrations and relative depletion of trace metals in coarse particles at high SPM concentrations. Particulate Zn, Mn and Pb were dominated by the fraction available to acetic acid (non-detrital), whilst particulate Ni, Fe and Cr were dominated by the fraction available to nitric acid (detrital). The partition coefficient of trace metals between SPM and water declined with increasing SPM concentration, consistent with the so-called "particle concentration effect". Such a phenomenon may be explained by the presence of fine particles (including colloids) enriched with trace metals at low SPM concentrations, and the salinity-induced desorption.     

Uranium transport around the reactor zone at Bangombé and Okélobondo (Oklo): examples of hydrogeological and geochemical model integration and data evaluation

The sites at Bangombé and Okélobondo (Oklo) in Gabon provide a unique opportunity to study the behaviour of products from natural nuclear reactions in the vicinity of reactor zones which were active around two billion years ago. The Commission of the European Communities initiated the Oklo Natural Analogue Programme. One of the principal aims was to study indications of present time migration of elements from the reactor zones under ambient conditions. The hydrogeological and hydrochemical data from the Oklo sites were modelled in order to better understand the geochemical behaviour of radionuclides in the natural system, by using independent models and by comparing the modelling outcome. Two modelling approaches were used: M3 code (hydrochemical mixing and mass balance model), developed by the Swedish Nuclear Fuel and Waste Management Company (SKB) and HYTEC (reactive transport model) developed by Ecole des Mines de Paris. Two different reactor zones were studied: Bangombé, a shallow site, the reactor being at 11 m depth, and OK84 at Okélobondo, situated at about 450 m depth, more comparable with a real repository location. This allowed the validation of modelling tools in two different sedimentary environments: one shallow, with a more homogeneous layering situated in an area of meteoric alteration, and the other offering the opportunity to study radionuclide migration from the reaction zone over a distance of 450 m through very heterogeneous sedimentary layers. The modeling results indicate that the chemical reactions retarding radionuclide transport are very different at the two sites. At Bangombé, the decomposition of organic material consumes oxygen and at Okélobondo the oxygen is consumed by inorganic reactions resulting, in both cases, in uranium retardation. Both modelling approaches (statistic with M3 code and deterministic with HYTEC code) could describe this situation. The goal of this exercise is to test codes which can help to describe and understand the processes taking place at the sites, validate the models with in situ data, and thus build confidence in the tools used for future site characterization. Ultimately, this allows identifying and selecting processes and parameters that can be used as input into repository performance assessment calculations and modelling exercises.     

Effect of pH control at the anode for the electrokinetic removal of phenanthrene from kaolin soil

Polycyclic aromatic hydrocarbon (PAH)-contaminated soils exist at numerous sites, and these sites may threaten public health and the environment because many PAH compounds are toxic, mutagenic, and/or carcinogenic. PAHs are also hydrophobic and persistent, so conventional remediation methods are often costly or inefficient, especially when the contaminants are present in low permeability and/or organic soils. An innovative technique, electrokinetically enhanced in situ flushing, has the potential to increase soil-solution-contaminant interaction and PAH removal efficiency for low permeability soils; however, the electrolysis reaction at the anode may adversely affect the remediation of low acid buffering capacity soils, such as kaolin. Therefore, the objective of this study was to improve the remediation of low acid buffering soils by controlling the pH at the anode to counteract the electrolysis reaction. Six bench-scale electrokinetic experiments were conducted, where each test employed one of three different flushing solutions, deionized water, a surfactant, or a cosolvent. For each of these solutions, tests were performed with and without a 0.01 M NaOH solution at the anode to control the pH. The test using deionized water with pH control generated a higher electroosmotic flow than the equivalent test performed without pH control, but the electroosmotic flow difference between the surfactant and cosolvent tests with and without pH control was minor compared to that observed with the deionized water tests. Controlling the pH was beneficial for increasing contaminant solubilization and migration from the soil region adjacent to the anode, but the high contaminant concentrations that resulted in the middle or cathode soil regions indicates that subsequent changes in the soil and/or solution chemistry caused contaminant deposition and low overall contaminant removal efficiency.     

Sorption of As(V) ions by akaganéite-type nanocrystals

A priority pollution problem, the removal of arsenate oxyanions from dilute aqueous solutions by sorption onto synthetic akaganéite (beta-FeO(OH)) was the aim of the present study. This is an innovative inorganic adsorbent material prepared in the laboratory, following a new method of preparation. The effect of akaganéite and arsenate concentration, the contact time, temperature, solution pH value, and ionic strength variation on the treatment process was mainly investigated during this study. Typical adsorption isotherms were determined, which were found to fit sufficiently the typical Langmuir equation. The mechanism of sorption was examined by electrokinetic, X-ray diffraction, Fourier transmission infrared and scanning electron microscopy measurements. Promising results were obtained, due to the favourite characteristics of the adsorbent applied.     

Metal ion removal from water by sorption on paper mill sludge

Chromatographic columns packed with paper mill sludge are employed for metal ion recovery from water. The breakthrough curves show that cadmium, copper, lead and silver are removed from acid solutions (pH 2, 4); the affinity series is Pb(II)>Cu(II)>Ag(I)>Cd(II). Both the amount of metal retained and the metal-matrix interaction are pH dependent; the sorptive capacity increases with increasing pH. When the metals are present together at the same initial concentrations a competition among the different ions occurs although the affinity order remains unchanged. In metal recovery from the paper mill sludge column, the total amount of the cadmium and copper is displaced by HCl 1.0 M, 65% of the lead by HCl 0.1 M and 75% of the silver by HNO(3) 0.1 M. More than 95% of copper and lead and less than 20% of cadmium were recovered with HCl 0.1 M when the metals were present at the same time.     

Congener-specific accumulation of polychlorinated biphenyls in ovarian follicular wall follows repeated exposure to PCB 126 and PCB 153. Comparison of tissue levels of PCB and biological changes

OBJECTIVE: Small (SF), medium (MF) and large (LF) preovulatory porcine follicles were isolated and incubated in an Erlenmeyer flask containing 5 ml of medium with addition of PCB 126 or PCB 153 to test differences in their accumulation in the follicular wall. METHODS; The follicles were incubated in M199 medium at 37 degrees C with constant shaking at 70 rpm, for 6 days. The media were changed every day and repeated dose 25 pg/ml of PCB 126 or 25 ng/ml of PCB 153 was added each day till 6 days of culture. Media were collected every day and frozen for steroid analysis by RIA. 24 h after the last treatment follicles were frozen for further polychlorinated biphenyls (PCB) content analysis. PCB concentrations in the follicular wall were analysed by mass spectrometry. RESULTS: 3.3%; 3.6% and 5.6% of total PCB 126 dose, and 71%; 71.4% and 30.4% of total PCB 153 dose accumulated in SF, MF and LF follicles, respectively. The accumulative effect of PCB was manifested by the disruption of estradiol (E2) secretion. In SF antiestrogenic action of PCB 126 was observed during the whole time of exposure while PCB 153 decreased E2 till 4 days of culture and then estrogenic action was observed. In MF, both these congeners decreased E2 till 5 days of exposure and then estrogenic actions were noted with the highest magnification in the case of PCB 126. In LF both PCB studied increased E2 till 3 days of exposure with the highest magnification of PCB 126, then antiestrogenic action was noted. Testosterone secretion was generally affected in a pattern oposite to that of E2 suggesting action on P450arom activity. CONCLUSION: The results of these studies demonstrated that disruption of aromatization process in the follicles following repeated exposure to both congeners is not directly correlated with the bioaccumulation or amount of PCB within the follicular wall.     

Twentieth century overview of heavy metals in the Galician Rias (NW Iberian Peninsula)

The 18 Galician Rias, comprising 25% of the Iberian Peninsula coastline, form a unique system within the European continental Atlantic coast and provide a useful reference area for studies of metals. These rias are sensitive to anthropogenic influence due to the socioeconomic importance generated in these areas by industry, aquaculture, port activities, fishing, tourism and, accordingly, several islands lying within close proximity to the rias have recently been declared natural parks. Aquaculture in the Galician Rias is a growth industry and in 2000 the rias supported 3386 mussel rafts producing 2.5 x 10(8) kg year(-1), i.e. 40% of European Union total seafood production. The Galician Rias are partially stratified estuaries with positive residual circulation with fresh (runoff lower than 100 m3 s(-1) and salt water mixing inside the basins. This behaviour has direct consequences on metal fluxes whereby the rias behave as a barrier and accumulate metals in the sediments. Metals tend to deposit close to point sources and remobilization occurs inside the ria, leading to a seaward decrease in metal concentration. With the exception of the Ulla (Arosa Ria) and Eume (Ares-Betanzos Ria) head rivers and the Lagares river (Vigo Ria) the available data suggest that riverine freshwater inputs are not the main source of contamination. Metal studies reported in the literature mainly relate to Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn, and to a lesser extent Hg and Sn. Studies of other harmful metals such as Ag, Se and As are notably lacking. In addition, the studies have been localized and mainly restricted to the surface sediment. Data of heavy metals in the dissolved phase, suspended particulate matter and biota is scarce in the mainstream literature and should be considered in the future research. From the entire Galician coast, data from seven rias of socio-economic importance form the bulk of the published work. There is an urgent need to standardize procedures, employ 'clean' procedures to avoid contamination of samples and regular assessment of analytical accuracy with CRMs in order that results can be compared among the scientific community and produce reliable results. The continuation of coastal environmental studies requires an enlargement of the sampling locations as well as systematic and periodic analysis of known pollution sources in order to decide whether coastal regeneration action is needed. Studies dedicated to metals in the water column are lacking and need more attention in future research. The majority of the available data correspond to the fluvial front (30%) at ria head and, to a lesser extent, to the oceanic front (3%), under summer upwelling events. Current awareness of the rias suggests that they are not contaminated although there is some evidence of important localized anthropogenically induced enrichments at the outflow of the Lagares River (Pb, Zn), the San Simón inlet (Pb) and near to the harbor (Pb, Zn, Cu) in the Vigo Ria, the inner part (Cu, Zn, Hg, Pb) of the Pontevedra Ria, the Ulla River estuary (Cu, Cr, Mn, Ni; Zn) in the Arosa Ria, the inner zone (Cu, Pb, Zn) of the Coru?a Ria, the Ferrol Ria (Zn) and the Eume Estuary (Zn, Mn, Ni, Co) in the Ares-Betanzos Ria. In addition, TBT enrichment has been found along the Galician coast, being highest in the industrial bays (Vigo, Coru?a and Ferrol). Nevertheless, it is important to point out the lack of information concerning the relationship between metal concentrations in different fractions of sediments and/or water and their bioavailability and toxicity on biota in order to confirm metal contamination dangers. The present paper reviews all the information published on metals in the rias up to the year 2000 and takes a biogeochemical standpoint, i.e. metal presence in the ria reservoirs: water column, suspended particulate matter, sediments and biota, as well as the fluvial and oceanic frontiers.     

AFLP analysis as biomarker of exposure to organic and inorganic genotoxic substances in plants

In recent years several plant species have been in use as bioindicators and several tests have been developed to evaluate the toxicity of environmental pollutants in vegetal organisms. In the present paper Arabidopsis thaliana (L.) Heynh. (ecotype Wassilewskija) was used as bioindicators of two genotoxic substances: potassium dichromate and dihydrophenanthrene. Inhibition of seed germination was observed with both pollutants. AFLP analysis (i) indicated that both substances are genotoxic, (ii) showed that dihydrophenanthrene induces DNA changes in different target sequences than potassium dichromate, (iii) quantified the genotoxic effect using cluster analysis by comparing DNA from treated plants with that of control plants. On the basis of these considerations we suggest that AFLP method is a powerful tool for measuring qualitative and quantitative genotoxic activity due to environmental pollutants. AFLP method can be applied to a wide range of bioindicator organisms and may become a universal methodology to identify target genes for specific genotoxic agents. This could open up possibilities for designing specifically targeted assays and new approaches to risk assessment.