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.LinkDoi: 10.1007/s11368-009-0073-1
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.
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.LinkDoi: 10.1007/s11368-009-0117-6
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.
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.LinkDoi: 10.1007/978-0-387-88959-7_20
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.
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.
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.
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
Domene X., Alcañiz J.M., Andrés P. (2008) Comparison of solid-phase and eluate assays to gauge the ecotoxicological risk of organic wastes on soil organisms. Environmental Pollution. 151: 549-558.LinkDoi: 10.1016/j.envpol.2007.04.007
Development of methodologies to assess the safety of reusing polluted organic wastes in soil is a priority in Europe. In this study, and coupled with chemical analysis, seven organic wastes were subjected to different aquatic and soil bioassays. Tests were carried out with solid-phase waste and three different waste eluates (water, methanol, and dichloromethane). Solid-phase assays were indicated as the most suitable for waste testing not only in terms of relevance for real situations, but also because toxicity in eluates was generally not representative of the chronic effects in solid-phase. No general correlations were found between toxicity and waste pollutant burden, neither in solid-phase nor in eluate assays, showing the inability of chemical methods to predict the ecotoxicological risks of wastes. On the contrary, several physicochemical parameters reflecting the degree of low organic matter stability in wastes were the main contributors to the acute toxicity seen in collembolans and daphnids. © 2007 Elsevier Ltd. All rights reserved.
Domene X., Ramírez W., Mattana S., Alcañiz J.M., Andrés P. (2008) Ecological risk assessment of organic waste amendments using the species sensitivity distribution from a soil organisms test battery. Environmental Pollution. 155: 227-236.LinkDoi: 10.1016/j.envpol.2007.12.001
Safe amendment rates (the predicted no-effect concentration or PNEC) of seven organic wastes were estimated from the species sensitivity distribution of a battery of soil biota tests and compared with different realistic amendment scenarios (different predicted environmental concentrations or PEC). None of the wastes was expected to exert noxious effects on soil biota if applied according either to the usual maximum amendment rates in Europe or phosphorus demands of crops (below 2 tonnes DM ha-1). However, some of the wastes might be problematic if applied according to nitrogen demands of crops (above 2 tonnes DM ha-1). Ammonium content and organic matter stability of the studied wastes are the most influential determinants of the maximum amendment rates derived in this study, but not pollutant burden. This finding indicates the need to stabilize wastes prior to their reuse in soils in order to avoid short-term impacts on soil communities. © 2007 Elsevier Ltd. All rights reserved.
Ramírez W.A., Domene X., Andrés P., Alcañiz J.M. (2008) Phytotoxic effects of sewage sludge extracts on the germination of three plant species. Ecotoxicology. 17: 834-844.LinkDoi: 10.1007/s10646-008-0246-5
In order to evaluate the ability of three types of extracts to explain the ecotoxicological risk of treated municipal sewage sludges, the OECD 208A germination test was applied using three plants (Lolium perenne L., Brassica rapa L., and Trifolium pratense L.). Three equivalent batches of sludge, remained as dewatered sludge, composted with plant remains and thermally dried, from an anaerobic waste water treatment plant were separated. Samples from these three batches were extracted in water, methanol, and dichloromethane. Plant bioassays were performed and the Germination Index (GI) for the three plants was evaluated once after a period of 10 days. Germination in extracts was always lower than the respective controls. The germination in composted sludge (GI 40.9-86.2) was higher than the dewatered (GI 2.9-45.8), or thermally dried sludges (GI 24.6-64.4). A comparison of the germination between types of extracts showed differences for dewatered sludge with the three plants, where the water and methanol extracts had significantly lower germination than the dichloromethane extract. A higher half maximal effective concentration (EC50) in composted extracts was established, mainly in the water extract (EC 50 431-490 g kg-1). On the contrary, the germination was strongly inhibited in the water extract of the dewatered sludge (EC50 14 g kg-1). The germination was positively correlated with the degree of organic matter stability of the parent sludge, and an inverse correlation was detected for total nitrogen, hydrolysable nitrogen and ammonium content. It is concluded that the phytotoxic effect of the water extract is more closely related to hydrophilic substances rather than lipophilic ones, and care must be taken with dewatered sludge application, especially with their aqueous eluates. Results obtained in this work show the suitability of the use of sludge extracts in ecotoxic assays and emphasize the relevance of sewage sludge stabilization by post-treatment processes. © 2008 Springer Science+Business Media, LLC.
Ramírez W.A., Domene X., Ortiz O., Alcañiz J.M. (2008) Toxic effects of digested, composted and thermally-dried sewage sludge on three plants. Bioresource Technology. 99: 7168-7175.LinkDoi: 10.1016/j.biortech.2007.12.072
In order to evaluate potential toxic effects of stabilized sewage sludge that are currently applied to agricultural soils, three types of municipal sewage sludge and one pig slurry were subjected to phytotoxicity assays using three plants (Brassica rapa, Lolium perenne and Trifolium pratense). Equivalent batches of aerobically and anaerobically-digested sludge (F) from two municipal wastewater treatment plants, were composted (C) or thermally dried (T). In addition, one anaerobically-digested and thermally-dried pig slurry (P) was tested. A seedling growth test was performed in accordance with the OECD Guideline 208A, using seed emergence and shoot length as endpoints to identify the inhibition of plants growing in increasing doses of sludge. A correlation analysis between EC50 and physico-chemical parameters or the pollutant burden of the biosolids was also calculated. In all tests, lower germination rates were observed for T. pratense than for L. perenne and B. rapa. A moderate stimulatory effect on shoot length at low doses was observed for the three plants. In these wastes, a strong positive correlation was found between higher values of EC50 (less toxicity) and the stability degree of their organic matter, and a negative correlation between EC50 and total N, hydrolysable N or NH4-N content. No correlations were found with heavy metal or organic pollutant content in those wastes. Results indicate that digested sludge, thermally-dried sludge and thermally-dried pig slurry have non-negligible short term phytotoxic effects, and confirm that composting is an effective sludge treatment for the reduction of phytotoxicity. © 2008 Elsevier Ltd. All rights reserved.
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