Ana Gavina

Lead and PAHs contamination of an old shooting range: A case study with a holistic approach

Soil pollution at firing ranges is an issue of growing importance, due to the accumulation in soils of contaminants derived from ammunition and clay targets. The concentration of Pb and PAHs was determined in five soils of an abandoned shooting range in Galicia (northwest Spain), and an ecotoxicological characterization was performed in order to obtain an assessment of risks. Therefore, the retention capacity of soils was assessed using test organisms of different trophic levels, and the role of soils as habitat for soil invertebrates was assessed by reproduction tests and bioaccumulation assays with earthworms. The sum of 15 PAHs ranged between 38 and 360mgkg-1, which exceed, together with Pb (160-720mgkg-1), the Galician generic reference value for urban and sporting field soils. Bioaccumulation in E. andrei showed contents up to 104,000μgPbkg-1dw, and up to 645μgPAHskg-1fw. High contents of Pb and PAHs in soil samples and in Eisenia andrei whole body, caused a reduction in the number of juveniles produced, whereas, Vibrio fischeri, Raphidocelis subcapitata and Daphnia magna displayed a slight toxic response to the soil elutriates tested. Therefore, the function of these soils to retain contaminants seemed not compromised, probably due to the high organic matter content and pH values, which are weakly acidic. The habitat function was affected, indicating that soil solution is not the only route of exposure to contaminants to E. andrei. The integration of chemical and ecotoxicological lines of evidence give rise to high risks values, restricting the use of these areas, and pointing for risks to surrounding ecosystems due to possible trophic transferences. The calculation of risks using the chemical and ecotoxicological data, required by Spanish legislation, could be a good approach to communicate with those responsible and/or involved in the management of contaminated sites.

Ecotoxicity of titanium silicon oxide (TiSiO4) nanomaterial for terrestrial plants and soil invertebrate species.

The huge evolution of nanotechnology and the commercialization of nanomaterials (NMs) positively contributed for innovation in several industrial sectors. Facing this rapid development and the emergence of NMs in the market, the release of this nanometric sized materials in the environment and the possible impact on different ecosystem components attracted the attention of researchers in the last few years. In our study we aimed to assess the impact of titanium silicon oxide nanomaterial (nano-TiSiO4) on soil biota to estimate a risk limit for this material. In the present research a battery of standardized ecotoxicological assays aimed at evaluating a wide range of endpoints (avoidance and reproduction of earthworms and collembolans, emergence/growth of four selected terrestrial plants) were carried out, using OECD artificial soil as test substrate spiked with aqueous suspension of different concentrations of nano-TiSiO4. The results showed a maximum avoidance percentage of 40% for earthworms (Esenia andrei) at the highest concentration tested (1000mgkg(-1) soildw of nano-TiSiO4). No significant effect on the reproductive function of both invertebrate species was recorded. Nevertheless, significant phytotoxic data was registered at least for the growth of dicotyledonous plant species (Lactuca sativa and Lycopersicon lycopersicum) with EC20 values ranging between 236 and 414 mg kg(-1) soildw of nano-TiSiO4 for L. sativa dry mass and fresh mass, respectively. Further, the characterization of nano-TiSiO4 in suspensions used to spike the soil, performed by Dynamic Light Scattering, showed the formation of aggregates with important average size diameter, thus demonstrating that the toxic effects observed were likely not size dependent. A deterministic PNEC (predicted no effect concentration) for this NM of 10.02mg kg(-1) soildw of nano-TiSiO4, is suggested, while no more ecotoxicological information exists.

Impact of organic nano-vesicles in soil: The case of sodium dodecyl sulphate/didodecyl dimethylammonium bromide.

Aiming at contributing new insights into the effects of nanomaterials (NMs) in the terrestrial ecosystem, this study evaluated the impacts of organic nano-vesicles of sodium dodecyl sulphate/didodecyl dimethylammonium bromide (SDS/DDAB) on the emergence and growth of plant seeds, and on the avoidance and reproduction of soil invertebrates. For this purpose several ecotoxicological assays were performed with different test species (terrestrial plants: Zea mays, Avena sativa, Brassica oleracea and Lycopersicon esculentum; soil invertebrates: Eisenia andrei and Folsomia candida). A wide range of SDS/DDAB concentrations were tested, following standard protocols, and using the standard OECD soil as a test substrate (5% of organic matter). The aqueous suspensions of SDS/DDAB, used to spike the soils, were characterised by light scattering techniques for hydrodynamic size of the vesicles, aggregation index, polydispersity index, zeta potential and surface charge. The SDS/DDAB concentrations in the test soil were analysed by HPLC-UV at the end of the assays. Invertebrate species were revealed to be sensitive to nano-SDS/DDAB upon immediate exposure to freshly spiked soils. However, the degradation of SDS/DDAB nano-vesicles in the soil with time prevented the occurrence of significant reproduction effects on soil invertebrates. Plants were not particularly sensitive to SDS/DDAB, except B. oleracea (at concentrations above 375 mg kg(-1)dw). The results gathered in this study allowed a preliminary determination of a risk limit to nano-SDS/DDAB. The low toxicity of SDS/DDAB nano-vesicles could be explained by its high and fast degradation in the soil. The soil microbial community could have an important role in the fate of this NM, thus it is of remarkable importance to improve this risk limit by taking into account specific data addressing this community.

Toxicological impact of cadmium-based quantum dots towards aquatic biota: Effect of natural sunlight exposure

Cadmium-based quantum dots (QDs) are increasingly applied in existent and emerging technologies, especially in biological applications due to their exceptional photophysical and functionalization properties. However, they are very toxic compounds due to the high reactive and toxic cadmium core. The present study aimed to determine the toxicity of three different QDs (CdS 380, CdS 480 and CdSeS/ZnS) before and after the exposure of suspensions to sunlight, in order to assess the effect of environmentally relevant irradiation levels in their toxicity, which will act after their release to the environment. Therefore, a battery of ecotoxicological tests was performed with organisms that cover different functional and trophic levels, such as Vibrio fischeri, Raphidocelis subcapitata, Chlorella vulgaris and Daphnia magna. The results showed that core-shell type QDs showed lower toxic effects to V. fischeri in comparison to core type QDs before sunlight exposure. However, after sunlight exposure, there was a decrease of CdS 380 and CdS 480 QD toxicity to bacterium. Also, after sunlight exposure, an effective decrease of CdSeS/ZnS and CdS 480 toxicity for D. magna and R. subcapitata, and an evident increase in CdS 380 QD toxicity, at least for D. magna, were observed. The results of this study suggest that sunlight exposure has an effect in the aggregation and precipitation reactions of larger QDs, causing the degradation of functional groups and formation of larger bulks which may be less prone to photo-oxidation due to their diminished surface area. The same aggregation behaviour after sunlight exposure was observed for bare QDs. These results further emphasize that the shell of QDs seems to make them less harmful to aquatic biota, both under standard environmental conditions and after the exposure to a relevant abiotic factor like sunlight.

Contribution for the Derivation of a Soil Screening Value (SSV) for Uranium, Using a Natural Reference Soil

In order to regulate the management of contaminated land, many countries have been deriving soil screening values (SSV). However, the ecotoxicological data available for uranium is still insufficient and incapable to generate SSVs for European soils. In this sense, and so as to make up for this shortcoming, a battery of ecotoxicological assays focusing on soil functions and organisms, and a wide range of endpoints was carried out, using a natural soil artificially spiked with uranium. In terrestrial ecotoxicology, it is widely recognized that soils have different properties that can influence the bioavailability and the toxicity of chemicals. In this context, SSVs derived for artificial soils or for other types of natural soils, may lead to unfeasible environmental risk assessment. Hence, the use of natural regional representative soils is of great importance in the derivation of SSVs. A Portuguese natural reference soil PTRS1, from a granitic region, was thereby applied as test substrate. This study allowed the determination of NOEC, LOEC, EC20 and EC50 values for uranium. Dehydrogenase and urease enzymes displayed the lowest values (34.9 and <134.5 mg U Kg, respectively). Eisenia andrei and Enchytraeus crypticus revealed to be more sensitive to uranium than Folsomia candida. EC50 values of 631.00, 518.65 and 851.64 mg U Kg were recorded for the three species, respectively. Concerning plants, only Lactuca sativa was affected by U at concentrations up to 1000 mg U kg1. The outcomes of the study may in part be constrained by physical and chemical characteristics of soils, hence contributing to the discrepancy between the toxicity data generated in this study and that available in the literature. Following the assessment factor method, a predicted no effect concentration (PNEC) value of 15.5 mg kg−1 dw was obtained for U. This PNEC value is proposed as a SSV for soils similar to the PTRS1.

Can Physiological Endpoints Improve the Sensitivity of Assays with Plants in the Risk Assessment of Contaminated Soils

Site-specific risk assessment of contaminated areas indicates prior areas for intervention, and provides helpful information for risk managers. This study was conducted in the Ervedosa mine area (Bragança, Portugal), where both underground and open pit exploration of tin and arsenic minerals were performed for about one century (1857 – 1969). We aimed at obtaining ecotoxicological information with terrestrial and aquatic plant species to integrate in the risk assessment of this mine area. Further we also intended to evaluate if the assessment of other parameters, in standard assays with terrestrial plants, can improve the identification of phytotoxic soils. For this purpose, soil samples were collected on 16 sampling sites distributed along four transects, defined within the mine area, and in one reference site. General soil physical and chemical parameters, total and extractable metal contents were analyzed. Assays were performed for soil elutriates and for the whole soil matrix following standard guidelines for growth inhibition assay with Lemna minor and emergence and seedling growth assay with Zea mays. At the end of the Z. mays assay, relative water content, membrane permeability, leaf area, content of photosynthetic pigments (chlorophylls and carotenoids), malondialdehyde levels, proline content, and chlorophyll fluorescence (Fv/Fm and ΦPSII) parameters were evaluated. In general, the soils near the exploration area revealed high levels of Al, Mn, Fe and Cu. Almost all the soils from transepts C, D and F presented total concentrations of arsenic well above soils screening benchmark values available. Elutriates of several soils from sampling sites near the exploration and ore treatment areas were toxic to L. minor, suggesting that the retention function of these soils was seriously compromised. In Z. mays assay, plant performance parameters (other than those recommended by standard protocols), allowed the identification of more phytotoxic soils. The results suggest that these parameters could improve the sensitivity of the standard assays.

Oxidative stress and genotoxicity of an organic and an inorganic nanomaterial to Eisenia andrei: SDS/DDAB nano-vesicles and titanium silicon oxide

In the past few years the number of studies on the toxic effects of nanomaterials (NMs) in the environment increased significantly. Nonetheless, the data is still scarce, since there is a large number of NMs and new ones are being developed each day. Soils are extremely important for life, and are easily exposed to the released NMs, thus enhanced efforts are needed to study the impacts on soil biota. The objective of the present work was to determine if different concentrations of two NMs, one inorganic (TiSiO4) and other organic (nano-vesicles of sodium sodecyl sulfate/ didodecyl dimethylammonium bromide - SDS/DDAB), are genotoxic to soil invertebrates. Additionally, it was intended to understand whether, in the event of occurring, genotoxicity was caused by the incapability of the cells to deal with the oxidative stress caused by these NMs. With that purpose, Eisenia andrei were exposed for 30 days to the artificial OECD soil contaminated with different concentrations of the NMs being tested. After the exposure, coelomocytes were extracted from earthworms and DNA damage was measured by the comet assay. The activity of antioxidant enzymes (e.g. glutathione peroxidase, glutathione reductase and glutathione-S-Transferase) and lipid peroxidation were also assessed. The results showed that both NMs were genotoxic, particularly TiSiO4 for which significant DNA damages were recorded for concentrations above 444mg of TiSiO4-NM/kg of soildw. Since no statistically significant differences were found in the tested antioxidant enzymes and in lipid peroxidation, the mechanism of genotoxicity of these NMs seemed to be unrelated with oxidative stress.

Availability of polycyclic aromatic hydrocarbons to earthworms in urban soils and its implications for risk assessment

Polycyclic aromatic hydrocarbons (PAHs) are a global problem, and in urban soils they can be found at potentially hazard levels. Nevertheless, the real risks that these contaminants pose to the environment are not well known, since the bioavailability of PAHs in urban soils has been poorly studied. Therefore, the bioavailability of PAHs in some selected urban soils from Lisbon (Portugal) was evaluated. Moreover, the applicability of a first screening phase based on total contents of PAHs was assessed. Results show that bioavailability of PAHs is reduced (low levels in earthworms, low accumulation percentages, and low biota-to-soil accumulation factors values), especially in more contaminated soils. The aging of these compounds explains this low availability, and confirms the generally accepted assumption that accumulation of PAHs in urban areas is mostly related with a long-term deposition of contaminated particles. The comparison of measured PAHs concentrations in earthworm tissues with the ones predicted based on theoretical models, reinforce that risks based on total levels are overestimated, but it can be a good initial approach for urban soils. This study also highlights the need of more reliable ecotoxicological data.

Deriviation of Terrestrial Predicted No-Effect Concentration (PNEC) for Cobalt Oxide Nanomaterial

Cobalt oxide nanomaterial (nano-Co3O4) is among the least investigated NMs in terms of environmental ecotoxicity. However, nano-Co3O4 was widely used for pigments, catalysis, sensors, electrochemistry, magnetism and energy storage.

Phytotoxicity of natural soils using physiological and biochemical endpoints reveals confounding factors: can a weight of evidence tackle uncertainty?

PurposeStandard assays for phytotoxicity provide a reductionist view on the performance of plants under toxic stress. To address two of the most prominent issues in plant toxicity studies, our aims were (1) to assess how well physiological and biochemical parameters complement standard toxicological endpoints when testing natural soils and (2) to assess the suitability of three commonly used control soils as comparative references.Material and methodsWe compared the performance of Zea mays and Helianthus annuus in three control soils (artificial Organisation for Economic Co-operation and Development (OECD) soil, standard LUFA 2.2 soil, and turf-perlite) against three natural soils representing a gradient of contamination (from a deactivated uranium mine). Standard endpoints (emergence and biomass) were estimated, along with pigment content, photosynthetic parameters, cellular injury, and proline content.Results and discussionThe toxicological profile of natural soils was highly dependent on the control soil used as reference; also, plant physiological performance was influenced by the soils’ properties. We discuss the need to interpret and combine multiple lines of evidence as a way to increase the degree of confidence one classifies soils based on their ecotoxicity, and this is where the integration of physiological and biochemical parameters bring added value.ConclusionsWhen facing large variability in soil characteristics, it is best to collect and integrate as much information possible to strengthen conclusions about phytotoxicity of natural soils. Obviously, this refutes reductionist views and places the final conclusion in the hands of expert judgment.