Bioassays prove the suitability of mining debris mixed with sewage sludge for land reclamation purposes

Domene X., Mattana S., Ramírez W., Colón J., Jiménez P., Balanyà T., Alcañiz J.M., Bonmatí M. (2009) Bioassays prove the suitability of mining debris mixed with sewage sludge for land reclamation purposes. Journal of Soils and Sediments. 10: 30-44.
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Doi: 10.1007/s11368-009-0073-1

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Background, aim, and scope: Mining activities disturb land and reduce its capacity to support a complete functional ecosystem. Reclamation activities in this case are not easy due to the large amount of soil required. This is why mining debris are usually used as surrogate of soil, despite their unsuitable physicochemical properties. However, these properties can be improved with the amendment using an organic source, usually sewage sludge. Nevertheless, the use of sludge might lead to impacts on soil and water ecosystems because of its physicochemical properties and pollutant content. The aim of this study is to assess the suitability of the use of mining debris amended with sewage sludge as practice for the reclamation of land degraded by limestone-quarrying activities. Materials and methods: Two different types of mining debris from the same limestone quarry and six different types of composted or thermally dried sewage sludge were studied. A laboratory assessment was carried out by means of standardized bioassays of sludges, together with a field assessment carried out in lysimeters filled with debris-sludge mixtures. The field assessment was carried out using both the soil-waste mixtures, amended with dosages similar to those used for restoration purposes and their corresponding leachates. The variation of physicochemical properties and the outcomes of different bioassays (soil microorganisms biomass and respiration, enzymatic activities, plant emergence and growth, collembolan survival and reproduction, and the Microtox assay) were used as indicators of fertilizing or ecotoxicological effects. Results: The mining debris used in our study showed a poor capacity for biological recovery, as shown by the lower biological outcomes measured in control lysimeters compared to lysimeters amended with sludge. The addition of sludge improved debris just before the sludge application in terms of its physicochemical and biological properties (microorganism's biomass, respiration and enzymatic activities) which, in some cases, persisted after a year. Conversely, in some sludges, an inhibition in soil collembolans was observed just before the amendment, but any inhibitory effect disappeared after a year. Concerning the leachates obtained from field lysimeters after a week and a year, no inhibitory effects were detectable for aquatic bacteria. Discussion: The effects observed on some of the measured biological endpoints, both in laboratory and field assays, were mainly mediated by physicochemical parameters related to a low stability of organic matter, but in the opposite sense depending on the organism considered. Microbial parameters were enhanced when the organic matter added had a low stability (high content in labile organic matter) but, on the other hand, collembolan performance was negatively affected. The lack of toxicity of leachates indicates a low risk for groundwaters of this reclamation practice. Conclusions: The results of this study support the use of mining debris mixed with sludge for land reclamation of degraded land by quarrying. The addition of sludge allowed a quick plant cover re-establishment and provided a suitable habitat for soil biota because no long-term ecotoxicological risks were observed neither for soils nor groundwaters. The results also indicate that the environmental risk of sludges might be reduced using sludges with a high content in stable organic matter. Recommendations and perspectives: The use of mining debris mixed with sewage sludges for mining reclamation purposes is suitable since long-term ecotoxicological risks were not observed. In addition, the results support the suitability of bioassays for the prediction of the success or risk of specific land reclamation practices in order to avoid unsuccessful attempts. © Springer-Verlag 2009.

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Soil pollution by nonylphenol and nonylphenol ethoxylates and their effects to plants and invertebrates

Domene X., Ramírez W., Solà L., Alcañiz J.M., Andrés P. (2009) Soil pollution by nonylphenol and nonylphenol ethoxylates and their effects to plants and invertebrates. Journal of Soils and Sediments. 9: 555-567.
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Doi: 10.1007/s11368-009-0117-6

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Background, aim, and scope Nonylphenol polyethoxylates (NPEOs) are a widely used class of nonionic surfactants known to be toxic and endocrine-disrupting contaminants. Their use and production have been banned in the European Union and substituted by other surfactants considered as environmentally safer. However, their use continues in many countries without any legal control. Discharges of effluents from wastewater treatment plants and the application of sewage sludge application, land-filling, and accidental spillage to soils are the major sources of NPEOs in the environment. The biodegrada-tion of these surfactants is relatively easy, leading to the accumulation of the simplest chemical forms of non-ylphenol ethoxylates (NP, NP1EO, and NP2EO) and nonylphenol carboxy acids (NP2EC or NP1EC). However, these are also the most toxic end-products and have a higher environmental persistence. Compared to aquatic ecosystems, not much is known about the effects of NPEOs in terrestrial organisms, with few studies mainly centered on the effects on plants and soil microorganisms. The main aim of this study is to provide the range of concentrations of NPEOs with ecotoxicological effects on different plants and soil invertebrate species. In addition, we aim to identify the main soil properties influencing their toxicity. Materials and methods Two natural soils collected and OECD artificial soil were used in toxicity bioassays. Two different NPEO formulations were tested. On the one hand, a technical mixture of NPEOs containing chain isomers and oligomers with an average of eight ethoxy units was used for the experiments and is referred to herein as NP8EO. On the other hand, technical-grade 4-nonylphenol 95% purity was also used and called NP in this study. The chemicals were applied and mixed with soil as an acetone solution. The toxicity of NP8EO and NP was assessed in different taxonomical groups (plants, earthworms, enchytraeids, and collembolans) according to their respective standardized methods. The effect on lethal and sublethal endpoints was assessed and, by means of linear and non-linear regression models, the NPEO concentration causing 10% and 50% inhibition was estimated. The influence of soil properties on the toxicity was assessed using generalized linear models (GLM). Results The chemicals tested showed contrasting toxicities, NP being clearly more toxic than NP8EO. There were also substantial differences in the sensitivity of the species and endpoints, together with clearly different toxicities in different soils. Plants were the least affected group compared to soil invertebrates, since plant endpoints were unaffected or only slightly inhibited. In soil invertebrates, reproduction was the most affected endpoint compared to growth or survival. Toxicity was the lowest in OECD artificial soil in comparison to natural soils, with a lower organic matter content. Discussion The higher toxicity of NP, both in plant and soil invertebrate bioassays, is consistent with previously published studies and its relatively high persistence in soil. The low phytotoxicity of NP8EO and NP, unaffected at concentrations over 1 g NP kg-1, also accords with the known low uptake in plants. The effects on soil inverte-brates appeared at lower concentrations than observed in plants, enchytraeids being less affected by NP8EO than earthworms and collembolans. Drastic inhibition in the invertebrate's endpoints generally appeared over 1 g kg-1 for NP8EO and below 1 g kg-1 for NP. The range of concentrations with effects is in agreement with the few similar studies published to date. Generally, the lowest toxicity values were obtained in OECD soil, with the highest organic matter content, while the highest toxicity was found in the PRA soil, with the lowest content. However, few of the models developed by GLM identified organic carbon as a significant factor in decreasing the bioavailability and toxicity of NPEO. The probable explanation for this is the simultaneous contribution of other soil properties and in particular the limited number of soils used in the bioassays. Conclusions A low ecotoxicological risk of NPEOs might be expected for plants and soil invertebrates, since the usual concentrations in soils (below 2.6 mg kg-1) are clearly less than the lowest concentrations reported to be toxic in our study. Recommendations and perspectives Although the apparent risk of NPEOs for soil ecosystems is limited, such risks should not be neglected since significant concentrations in soil could be reached with elevated application rates or when highly polluted sludges are used. More importantly, NPEO concentrations in soils should be maintained low given the extremely high toxicity for aquatic organisms. Despite the reduced leaching of NPEOs, runoff events might transport NP attached to soil particles and affect adjacent aquatic ecosystems. © Springer-Verlag 2009.

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Earthworm avoidance tests

Natal-Da-Luz T., Domene X., Scheffczyk A., Sousa J.P. (2009) Earthworm avoidance tests. Ecotoxicological Characterization of Waste: Results and Experiences of an International Ring Test. : 191-196.
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Doi: 10.1007/978-0-387-88959-7_20

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Based on the fact that organisms have the ability to avoid unfavorable conditions, the avoidance tests with earthworms have been used as an important tool to detect contaminants present in soil. Being ecologically relevant, quick and cost-effective, these bioassays have high sensitivity compared to conventional acute and chronic tests. Earthworm avoidance tests were performed in an inter-laboratory ring test of waste in accordance with ISO guideline No 17512-1 to evaluate the usefulness of this type of bioassays in waste characterization. Concentration gradients of three test wastes (INC, SOI and WOO) were tested using the artificial OECD soil as control. The species Eisenia fetida and Eisenia andrei were used as test organisms. A total of 12 avoidance tests were performed by four laboratories. The results obtained proved the higher sensitivity of this type of bioassay compared to tests using other terrestrial organisms (in particular, the earthworm acute test). Although all three wastes induced an avoidance behavior, the WOO treatments were the most avoided. © 2009 Springer-Verlag New York.

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Earthworm avoidance test. In: Roembke J, Becker R, Moser H. (eds) Ecotoxicological characterization of waste - Results and experiences of an international ring test. Springer Science, New York, USA.

Natal-Da-Luz T, Domene X, Scheffczyk A, Sousa JP (2009) Earthworm avoidance test. In: Roembke J, Becker R, Moser H. (eds) Ecotoxicological characterization of waste - Results and experiences of an international ring test. Springer Science, New York, USA.

¿Como montar un test de ecotoxicidad para lodo de depuradora? In: Barrera-Cataño JI, Contreras-Rodríguez S, Ochoa-Carreño A, Perilla-Castro SC, Garzón-Yepes N, Rondón-Camacho DC. (eds)

Domene X (2009) ¿Como montar un test de ecotoxicidad para lodo de depuradora? In: Barrera-Cataño JI, Contreras-Rodríguez S, Ochoa-Carreño A, Perilla-Castro SC, Garzón-Yepes N, Rondón-Camacho DC. (eds) Restauración ecológica de áreas afectadas por minería a cielo abierto en Colombia. Pontificia Universidad Javeriana, Bogotá

La importancia de los tests de ecotoxicidad en la aplicación de biolsólidos como enmienda orgànica. In: Barrera-Cataño JI, Contreras-Rodríguez S, Ochoa-Carreño A, Perilla-Castro SC, Garzón-Yepes N, Rondón-Camacho DC. (eds).

Domene X (2009) La importancia de los tests de ecotoxicidad en la aplicación de biolsólidos como enmienda orgànica. In: Barrera-Cataño JI, Contreras-Rodríguez S, Ochoa-Carreño A, Perilla-Castro SC, Garzón-Yepes N, Rondón-Camacho DC. (eds). Restauración ecológica de áreas afectadas por minería a cielo abierto en Colombia. Pontificia Universidad Javeriana, Bogotá.