Ecological risk assessment of organic waste amendments using the species sensitivity distribution from a soil organisms test battery

Ecotoxicity of oil sludges and residuals from their washing with surfactants: soil dehydrogenase and ryegrass germination tests

Oil sludge washing (OSW) with surfactants and co-solvents is used to recover the oil, and this process leaves some residuals (sediments and surfactant solution). Currently, there are no data on the ecotoxicological effects of these OSW residuals from different sludges. This study evaluated the toxicity of OSW residuals from washing four types of oil sludges with five surfactants (Triton X-100 and X-114, Tween 80, sodium dodecyl sulphate (SDS) and rhamnolipid) and a co-solvent (cyclohexane). The toxicity of the residuals was evaluated with the impact on the soil microbial dehydrogenase activity (DHA) and ryegrass (Lolium perenne) seed germination. There was a high DHA detected directly in the sludges and all OSW residual combinations, but this activity could not be attributed to the DHA itself but to some chemical interferences. The DHA was then tested in the soils amended with the OSW residuals to simulate a bioremediation scenario. There were no chemical interferences in this case. In general, the INTF concentrations were significantly higher at low concentrations, 1 and 5% (p < 0.01). There were no significant differences in the DHA at high concentrations of OSW residuals (10, 25 and 50%) which implied that the concentration of the contaminants is not directly proportional to the levels of ecotoxicity. Unexpectedly, the INTF values of the 10, 25 and 50% rhamnolipid-OSW residuals were significantly lower than the Triton X-100 residuals. The ryegrass germination rates were higher than 70% with no apparent phytotoxicity symptoms in the seedlings. Particularly, there was a highly significant negative effect of the residuals on the germination rates at high concentrations (p < 0.01). Given that the extractable petroleum hydrocarbon (EPH) concentrations in the OSW residual-amended soils in both DHA and germination tests were very low (13-21 ppm), other co-contaminants could be contributing to the toxicity. These findings implied that biotreatment techniques can be applied to treat the OSW residuals if necessary.

Tangerine, banana and pomegranate peels valorisation for sustainable environment: A review

Over the last decade the world has been generating a high quantity of tangerine peel waste (TPW), pomegranate peel waste (PPW) and banana peel waste (BPW). These peels have several economic benefits but there is mismanagement or inappropriate valorisation that could present risks to environment and public health. In the current review, we discussed the use of TPW, PPW and BPW directly for animal feed, soil fertilization, specific compost production and bio-adsorbent. We also discussed the valorisation of these peels for manufacturing the value-added products including enzymes, essential oil and other products that can be used in human food, in medical and cosmetic industry. Additionally, recent studies concerning the valorisation of these peels by biorefinery for bioethanol, biogas and biohydrogen production have been discussed. In the same context some other recent studies about valorisation of microorganisms isolated from these peels for medical, agronomic and industrial interests have been also discussed.

Development of human health ambient water quality criteria of 12 polycyclic aromatic hydrocarbons (PAH) and risk assessment in China

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed in various environmental media and have thus attracted extensive attention worldwide. To prevent and control PAH pollution in China, the study of ambient water quality criteria (AWQC), human health risks, and aquatic ecological risk is critical. There are no reports to date on the human health AWQC of PAHs in China. Therefore, this study first derived the human health AWQC values of 12 PAHs based on exposure data and bioaccumulation factor in China. We found that local exposure parameters and other relevant factors were key during the development of AWQC in different countries and regions, which led to differences with the reference value recommended by USEPA. Based on the incremental life time cancer risk (ILCR), hazard quotients (HQ) and potentially affected fraction (PAF) methods, the health and ecological risks of 16 PAHs were assessed subsequently. And the results are as follows: the non-carcinogenic PAHs' health risks ranged from 1.01 × 10^-10 to 1.60 × 10^-9, and carcinogenic PAH health risks ranged from 5.03 × 10^-7 to 4.74 × 10^-5. The toxic effects of 8 PAHs on aquatic organisms exhibited the following order: benzo (a) pyrene (BaP) > anthracene (Ant) > pyrene (Pye) > phenanthrene (Phe) > fluoranthene (Flua) > acenaphthene (Ace) > fluorene (Flu) > naphthalene (Nap). Among these, the ecological risks posed by Ant and BaP were the highest, according to the HQ and PAF methods.

Exploring the Use of Species Sensitivity Distributions to Define Protective Limits for the Use of Organic Wastes as Soil Amendments

The use of organic wastes as soil amendments can be an important measure to improve soil quality and reduce waste accumulation and landfilling. However, the potential contaminant loads of such wastes, can be a source of environmental concern. Consequently, legislation has been developed to regulate the use of these wastes in agricultural soils. However, the regulations only consider chemical parameters, which are insufficient to establish the level of environmental risk. A possible solution is the use of species sensitivity distributions (SSDs), employing ecotoxicological data from test batteries that could be incorporated into legislation. In the present study, 2 different hazardous concentrations affecting 5 and 50% of the soil community (HC5 and HC50, respectively) were determined using ecotoxicological data (effect concentrations, 10 and 50% [EC10 and EC50, respectively]) for 5 different wastes. The results demonstrate that, as expected, current legislative thresholds do not translate to environmental risk/protection and that SSDs may be an important tool allowing the simple inclusion and interpretation of ecotoxicological data from test batteries in legislation. On the other hand, SSDs must be used with caution because there are still doubts about their actual value in risk prediction and about which estimates provide adequate protection. For instance, the use of HC50EC10 values is not recommended; these values overlap with the more conservative HC5EC50 data, highlighting the fact that the use of lower effect concentrations may not always provide the most protective approach. Also, hazardous concentrations need to be calibrated at the field or semifield level, to verify environmental protection in different soils/environments and the adequacy of standard test organisms. Environ Toxicol Chem 2019;38:1569-1576. © 2019 SETAC.

A mixture of cellulose production waste with municipal sewage as new material for an ecological management of wastes

Chemical contaminants present in cellulose production waste and municipal sewage sludge condition the necessity to treat these wastes before they are introduced into the environment. Environmental use of the these wastes appears to be justified owing to the content of organic substances as well as the considerable fertilising value. The aim of the study was to assess chemical composition and ecotoxicity of cellulose production waste and municipal sewage sludge in terms of their eco-friendly application. The assessment was done based on the established soil environment according to regulations in Poland. The research on the chemical composition of the wastes was conducted under laboratory conditions, determining the content of macroelements, microelements and heavy metals with respect to using these wastes in the environment. Phytotoxkit and Microtox tests were performed in order to determine the ecotoxicity of the wastes in the aspect of their environmental use. It was established that, compared to the cellulose production waste, the municipal sewage sludge used in the incubation experiment had a higher content of macroelements and microelements. The content of heavy metals in the waste did not exceed the permissible content that conditions their use in agriculture and reclamation. Based on the results of bioassays it was established that the cellulose production waste was toxic, whereas the combination of cellulose production waste and sewage sludge was found to be of low toxicity to test organisms. The applied wastes and their mixtures were ranked according to phytotoxicity in the following order: cellulose production waste > cellulose production waste + soil > cellulose production waste + sewage sludge. The research results indicate that waste mixtures qualify for environmental use. With respect to the variable chemical composition of cellulose production waste and municipal sewage sludge as well as their ecotoxicity, it was established that each batch intended for environmental use must be subjected to chemical analysis and ecotoxicological tests.

Should oral exposure in Hypoaspis aculeifer tests be considered in order to keep them in Tier I test battery for ecological risk assessment of PPPs?

The laboratory reproduction test with the predatory mite Hypoaspis aculeifer is currently a mandatory test in the new EU data requirements for prospective environmental risk assessment of Plant Protection Products (PPPs). However, the low sensitivity often shown by this mite towards PPPs, when compared to other invertebrates (namely Folsomia candida and Eisenia fetida), makes the test with this species not very useful in the lower tier test battery. However, the current test protocol only considers exposure to contaminants via contaminated soil, disregarding exposure via contaminated food and does not take into account the fact that H. aculeifer is a predatory species. Therefore, through this protocol, the toxicity of contaminants to soil mites might be underestimated and, thus, an adaptation of the test performance, by including exposure via contaminated food, may be necessary. With this aim, two reproduction tests with H. aculeifer were performed using copper chloride as model substance, artificial soil as test substrate and cheese mites as food. The OECD guideline was followed but, while in one test cheese mites from normal laboratory breeding cultures (clean prey mites) were provided, in the other test, cheese mites previously exposed to copper (Cu pre-exposed prey mites) were provided. Predatory mites were affected at lower concentrations in tests using Cu pre-exposed prey compared to test with clean-prey (NOEC = 1225 and 1508 mg kg^-1 and EC₁₀ = 1204 and 1903 mg kg^-1 using Cu pre-exposed and clean prey, respectively). However, this higher sensitivity was not detected by EC₅₀ values (EC₅₀ = 2634 and 2814 mg kg^-1 using Cu pre-exposed and clean prey, respectively). Further tests are needed in order to (i) investigate the relevance of oral exposure to different PPPs, (ii) optimize the contamination of prey mites according to the chemical properties of each substance and (iii) substantiate a proposal to adapt the standard protocol.

Organic wastes as soil amendments - Effects assessment towards soil invertebrates

Using organic wastes, as soil amendments, is an important alternative to landfilling with benefits to soil structure, water retention, soil nutrient and organic matter concentrations. However, this practice should be monitored for its environmental risk due to the frequent presence, of noxious substances to soil organisms. To evaluate the potential of eight organic wastes with different origins, as soil amendments, reproduction tests with four soil invertebrate species (Folsomia candida, Enchytraeus crypticus, Hypoaspis aculeifer, Eisenia fetida) were performed using gradients of soil-waste mixtures. Results obtained demonstrated that contaminant concentrations required by current legislation might not be a protective measure for the soil ecosystem, as they do not properly translate the potential toxicity of wastes to soil invertebrates. Some wastes with contaminant loadings below thresholds showed higher toxicity than wastes with contaminants concentrations above legal limits. Also, test organism reproduction was differently sensitive to the selected wastes, which highlights the need to account for different organism sensitivities and routes of exposure when evaluating the toxicity of such complex mixtures. Finally this study shows that when combining chemical and ecotoxicological data, it is possible to postulate on potential sources of toxicity, contributing to better waste management practices and safer soil organic amendment products.

Detoxification of sewage sludge by natural attenuation and implications for its use as a fertilizer on agricultural soils

Sewage Sludges (SS) from wastewater treatment systems constitute a potential alternative to agricultural fertilizers. However, their use is limited by the presence of toxic substances that may represent significant hazards for the environment and for human health. To test the potential of natural processes to attenuate their putative toxic activities, actual SS samples from domestic sewage were buried in holes in a pollution-free environment for different periods of time, up to one year. Aqueous and organic extracts were obtained after each period of natural attenuation, and their respective toxicity was tested for estrogenic and dioxin-like activity by yeast-based bioassays (ER-RYA and AhR-RYA, respectively) and for general toxicity and teratogenicity in zebrafish embryos. Dioxin-like activity was also tested in zebrafish embryos by monitoring the induction of the marker gene cyp1a. Whereas the results showed essentially no estrogenic activity, both dioxin-like activity and embryotoxicity were observed in the initial samples, decreasing significantly after six months of attenuation. Chemical analysis of toxic SS samples showed the presence of low levels of dioxins and furans, and relatively high levels of m- and p-cresol, at concentrations that only partially justify the observed biological effects. Our data indicates the presence of largely uncharacterized hydrophilic compounds with high biological activity in SS, constituting a potential risk of groundwater pollution upon their disposal into the environment. It also shows that this potential impact may be significantly mitigated by attenuation protocols, as the one presented here.

Attesting the efficiency of monitored natural attenuation in the detoxification of sewage sludge by means of genotoxic and mutagenic bioassays

A viable alternative to the use of sewage sludge (SS) would be using it as a reconditioner of agricultural soils, due to its high content of organic matter and nutrients. However, this solution may contaminate the soil, since SS may contain toxic substances. Monitored natural attenuation is a process that can be used in the decontamination of SS before its disposal into the environment. The effectiveness of the natural attenuation of a domestic SS was evaluated over 12 months by assays of Salmonella/microsome and micronucleus (MN) in human hepatoma cells (HepG2). Mutagenic activity was observed for the Salmonella strain TA 100, with S9, for the extracts from periods 0-6 months of natural attenuation. Genotoxic effects were observed in HepG2 cells, for 0 and 2 months, in almost all tested concentrations. Comparing obtained data by MN test to chemical analyses, it is possible to observe a coincidence between the induction of MN and the quantity of the m- and p-cresol, since these compounds were present in the initial SS and after 2 months of natural attenuation, decreasing their concentrations in samples from 6 to 12 months. The positive results obtained with Salmonella/microsome (from 6 months) suggest a combined action of other substances in SS. These results indicated that this SS, in the earlier periods tested, is potentially genotoxic and mutagenic and that its disposal can lead to severe environmental problems. Thus, the use of the studied SS as reconditioner requires pre-processing for over than 6 months of natural attenuation.

Ecotoxicological assessment of biosolids by microcosms

Biosolids have been applied as soil amendments to improve and maintain the soil fertility and faster plant growth. In spite of its beneficial use, the potential risks of land disposal should be analyzed, considering potential ecological receptors in soil and water. This work describes the use of an early warning laboratory microcosm system to evaluate the integrated ecotoxicological potential of two biosolids: BIO-1 and BIO-2 (18 and 28 months after landfarming, respectively), from an effluent treatment station in a petrochemical and industrial district. The endpoints related to habitat function were: a) germination, growth and biomass of Phaseolus vulgaris; b) survival, biomass and number of cocoons of Eisenia andrei (Oligochaeta) and; c) reproduction of Folsomia candida (Collembola). The retention function was evaluated by testing the leachates using the tropical cladoceran Latonopsis australis (Cladocera) in a 48-h acute toxicity test, and growth of the aquatic plant Lemna minor in a 7-d chronic test. Tropical artificial soil (TAS) and a natural soil (NS) from the region were used as control soils. Results showed no chronic toxicity of BIO-1 and BIO-2 to the soil organisms tested, but acute toxicity of BIO-1 in the leachate for 50% of L. australis, and chronic toxicity of both biosolid leachates to L. minor (inhibition of growth rate), indicating potential risks to aquatic ecosystems. The results confirmed the ability of this microcosm system as a rapid tool to assess biosolid toxicity over time and its potential for hazardous waste characterization in environmental risk assessment, in a screening phase.

Ecotoxicological assessment of the potential impact on soil porewater, surface and groundwater from the use of organic wastes as soil amendments

This study aimed to assess the potential impact on soil porewater, surface and groundwater from the beneficial application of organic wastes to soil, using their eluates and acute bioassays with aquatic organisms and plants: luminescence inhibition of Vibrio fischeri (15 and 30 min), Daphnia magna immobilization (48 h), Thamnocephalus platyurus survival (24 h), and seed germination of Lolium perenne (7 d) and Lactuca sativa (5 d). Some organic wastes' eluates promoted high toxic responses, but that toxicity could not be predicted by their chemical characterization, which is compulsory by regulatory documents. In fact, when organisms were exposed to the water-extractable chemical compounds of the organic wastes, the toxic responses were more connected to the degree of stabilization of the organic wastes, or to the treatment used to achieve that stabilization, than to their contaminant load. That is why the environmental risk assessment of the use of organic wastes as soil amendments should integrate bioassays with eluates, in order to correctly evaluate the effects of the most bioavailable fraction of all the chemical compounds, which can be difficult to predict from the characterization required in regulatory documents. According to our results, some rapid and standardized acute bioassays can be suggested to integrate a Tier 1 ecotoxicological evaluation of organic wastes with potential to be land applied, namely luminescence inhibition of V. fischeri, D. magna immobilization, and the germination of L. perenne and L. sativa.

Derivation of Soil Ecological Criteria for Copper in Chinese Soils

Considerable information on copper (Cu) ecotoxicity as affected by biological species and abiotic properties of soils has been collected from the last decade in the present study. The information on bioavailability/ecotoxicity, species sensitivity and differences in laboratory and field ecotoxicity of Cu in different soils was collated and integrated to derive soil ecological criteria for Cu in Chinese soils, which were expressed as predicted no effect concentrations (PNEC). First, all ecotoxicity data of Cu from bioassays based on Chinese soils were collected and screened with given criteria to compile a database. Second, the compiled data were corrected with leaching and aging factors to minimize the differences between laboratory and field conditions. Before Cu ecotoxicity data were entered into a species sensitivity distribution (SSD), they were normalized with Cu ecotoxicity predictive models to modify the effects of soil properties on Cu ecotoxicity. The PNEC value was set equal to the hazardous concentration for x% of the species (HCx), which could be calculated from the SSD curves, without an additional assessment factor. Finally, predictive models for HCx based on soil properties were developed. The soil properties had a significant effect on the magnitude of HCx, with HC5 varying from 13.1 mg/kg in acidic soils to 51.9 mg/kg in alkaline non-calcareous soils. The two-factor predictive models based on soil pH and cation exchange capacity could predict HCx with determination coefficients (R²) of 0.82–0.91. The three-factor predictive models – that took into account the effect of soil organic carbon – were more accurate than two-factor models, with R² of 0.85–0.99. The predictive models obtained here could be used to calculate soil-specific criteria. All results obtained here could provide a scientific basis for revision of current Chinese soil environmental quality standards, and the approach adopted in this study could be used as a pragmatic framework for developing soil ecological criteria for other trace elements in soils.

Lanthanide ecotoxicity: first attempt to measure environmental risk for aquatic organisms

The geochemical cycles of lanthanides are being disrupted by increasing global production and human use, but their ecotoxicity is not fully characterized. In this study, the sensitivity of Aliivibrio fischeri and Pseudokirchneriella subcapitata to lanthanides increased with atomic number, while Daphnia magna, Heterocypris incongruens, Brachionus calyciflorus and Hydra attenuata were equally sensitive to the tested elements. In some cases, a marked decrease in exposure concentrations was observed over test duration and duly considered in calculating effect concentrations and predicted no effect concentrations (PNEC) for hazard and risk assessment. Comparison of PNEC with measured environmental concentrations indicate that, for the present, environmental risks deriving from lanthanides should be limited to some hotspots (e.g., downstream of wastewater treatment plants). However, considering the increasing environmental concentrations of lanthanides, the associated risks could become higher in the future. Ecotoxicological and risk assessment studies, along with monitoring, are required for properly managing these emerging contaminants.

Predicting bioavailability of metals from sludge-amended soils

We attempted to develop a protocol for fixing the maximum permissible limit of sludge in agricultural lands based on transfer of metals from sludge-amended soils to human food chain. For this purpose, spinach was grown as a test crop on acid and alkaline soils with graded doses of sludge (0, 1.12, 2.24, 4.48, 8.96, 17.9, 35.8, 71.6, 142 and 285 g kg(-1) of soil) in a pot experiment. Biomass yield of spinach was increased due to sludge application in both acid and alkaline soils. Among the chemical extractants, EDTA extracted the highest amount of metals from sludge-amended soil followed by diethylenetriaminepentaacetic acid (DTPA) and CaCl2. Elevated levels of Zn, Cu, Fe, Mn, Ni, Cd and Pb in spinach were observed due to sludge application over control. Application of sludge was more effective in increasing metal content in spinach grown on acid soil than alkaline soil. Solubility-free ion activity model as a function of pH, organic carbon and extractable metal was far more effective in predicting metal uptake by spinach grown on sludge-amended soils as compared to that of chemical extractants. Risk in terms of hazard quotient (HQ) for intake of metals through consumption of spinach by humans grown on sludge-treated soils was computed for different metals separately. In a 90-day pot experiment, safe rates of sludge application were worked out as 4.48 and 71.6 g kg(-1) for acid and alkaline soils, respectively.

Physiological and molecular responses of the earthworm (Eisenia fetida) to soil chlortetracycline contamination

This study aims to evaluate toxic effects of exposure to chlortetracycline (CTC) in soil on reproductive endpoints (juvenile counts and cocoon counts), biochemical responses, and genotoxic potentials of the earthworm Eisenia fetida. Results showed that juvenile counts and cocoon counts of the tested earthworms were reduced after exposure to CTC. The effective concentrations (EC(50) values) for juvenile and cocoon counts were 96.1 and 120.3 mg/kg, respectively. Treatment of earthworms with CTC significantly changed the activity of catalase (CAT), superoxide dismutase (SOD) and glutathione S-transferase (GST). An increase in malondialdehyde (MDA) indicated that CTC could cause cellular lipid peroxidation in the tested earthworms. The percentage of DNA in the tail of single-cell gel electrophoresis of coelomocytes as an indication of DNA damage increased after treatment with different doses of CTC, and a dose-dependent DNA damage of coelomocytes was found. In conclusion, CTC induces physiological responses and genotoxicity on earthworms.

Direct soil contact values for ecological receptors exposed to weathered petroleum hydrocarbon (PHC) fraction 2

Ecological tier 1 Canada-wide standards (CWS) for petroleum hydrocarbon (PHC) fraction 2 (F2; >nC10-C16) in soil were derived using ecotoxicological assessment endpoints (effective concentrations [ECs]/lethal concentrations [LCs]/inhibitory concentrations, 25% [IC25s]) with freshly spiked (fresh) fine- and coarse-grained soils. These soil standards might be needlessly conservative when applied to field samples with weathered hydrocarbons. The purpose of the present study was to assess the degradation and toxicity of weathered PHC F2 in a fine-grained soil and to derive direct soil contact values for ecological receptors. Fine-grained reference soils were spiked with distilled F2 and weathered for 183 d. Toxicity tests using plants and invertebrates were conducted with the weathered F2-spiked soils. Endpoint EC/IC25s were calculated and used to derive soil standards for weathered F2 in fine-grained soil protective of ecological receptors exposed via direct soil contact. The values derived for weathered F2 were less restrictive than current ecological tier 1 CWS for F2 in soil.

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.

Chlorobenzenes and organochlorinated pesticides in vegetable soils from an industrial site, China

Organochlorinated compounds are ubiquitous contaminants in the environment, especially in industrial sites. The objective of the work was to investigate whether a vegetable field near an industrial site is safe for vegetable production. The residues of chlorobenzenes (CBs), hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) in a vegetable field which was near a chemical plant in China were characterized. Point estimate quotient was used for ecological risk assessment of the investigated site. The results showed that all CBs except monochlorobenzene (MCB) were detected in soils. The total concentrations of sigmaCBs ranged from 71.06 to 716.57 ng/g, with a mean concentration of 434.93 ng/g. The main components of CBs in soil samples were dichlorobenzenes (DCBs), trichlorobenzenes (TCBs) and tetrachlorobenzenes (TeCBs), while for single congeners, 1,2,4-TCB had the highest concentration, which ranged from 13.21 to 210.35 ng/g with a mean concentration of 111.89 ng/g. Residues of hexachlorobenzene (HCB) in soil samples ranged from 0.9 to 11.79 ng/g, significantly lower than sigmaDCB, sigmaTCB and sigmaTeCB. Concentrations of sigmaHCHs and sigmaDDTs in soils ranged from 11.32 to 55.24 ng/g and from 195.63 to 465.58 ng/g, respectively, of which the main components were alpha-HCH and p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE). Ecological risk assessment for the investigated site showed that the most potential risks were from TCBs and TeCBs, based on the hazard quotients. The higher residues of CBs and DDTs compared to the target values and the higher than 1 hazard quotients indicated that this area is not safe for vegetable production and thus soil remediation is needed.

Soil bioassays as tools for sludge compost quality assessment

Composting is a waste management technology that is becoming more widespread as a response to the increasing production of sewage sludge and the pressure for its reuse in soil. In this study, different bioassays (plant germination, earthworm survival, biomass and reproduction, and collembolan survival and reproduction) were assessed for their usefulness in the compost quality assessment. Compost samples, from two different composting plants, were taken along the composting process, which were characterized and submitted to bioassays (plant germination and collembolan and earthworm performance). Results from our study indicate that the noxious effects of some of the compost samples observed in bioassays are related to the low organic matter stability of composts and the enhanced release of decomposition endproducts, with the exception of earthworms, which are favored. Plant germination and collembolan reproduction inhibition was generally associated with uncomposted sludge, while earthworm total biomass and reproduction were enhanced by these materials. On the other hand, earthworm and collembolan survival were unaffected by the degree of composting of the wastes. However, this pattern was clear in one of the composting procedures assessed, but less in the other, where the release of decomposition endproducts was lower due to its higher stability, indicating the sensitivity and usefulness of bioassays for the quality assessment of composts.

Comparison of solid-phase bioassays and ecoscores to evaluate the toxicity of contaminated soils

Five bioassays (inhibition of lettuce germination and growth, earthworm mortality, inhibition of springtail population growth, avoidance by springtails) were compared, using four coke factory soils contaminated by PAHs and trace elements, before and after biotreatment. For each bioassay, several endpoints were combined in an 'ecoscore', a measure of test sensitivity. Ecoscores pooled over all tested bioassays revealed that most organisms were highly sensitive to the concentration of 3-ring PAHs. When four soils were combined, behavioural tests using the springtail Folsomia candida showed higher ecoscores, i.e. they were most sensitive to soil contamination. However, despite overall higher sensitivity of behavioural tests, which could be used for cheap and rapid assessment of soil toxicity, especially at low levels of contamination, some test endpoints were more sensitive than others, and this may differ from a soil to another, pointing to the need for a battery of bioassays when more itemized results are expected.

Testing of different plants to determine influence of physico-chemical properties and contaminants content on municipal sewage sludges phytotoxicity

This study attempts to evaluate the Phytotoxkit as a tool for measuring the toxicity of municipal sewage sludges using 10 common plants: mustard, turnip, cress, red clover, cucumber, tomato, radish, sorrel, and spinach. The results were used to determine a germination index (GI) and a median effective concentration (EC) value for each plant. The trace metal and polycyclic aromatic hydrocarbon (PAH) contaminant content and the physical-chemical properties were examined. Most sewage sludges were characterized by an unfavorable electrical conductivity value of about 5.2 mS/cm(-1). The most abundant trace metals were zinc (Zn) at 871-1680 mg kg(-1), manganese (Mn) at 245-661 mg kg(-1), and copper (Cu) at 88.2-161.0 mg kg(-1). The lowest values were determined for cobalt (Co) at 2.9-3.8 mg kg(-1) and cadmium (Cd) at 0.7-3.7 mg kg(-1). The PAH sum was based on 10 individual compounds (USE EPA), and the PAH content ranged from 4.76 to 27.95 mg kg(-1), most of the sewage sludges showing a predomination by carcinogenic PAHs. The GI values, based on seed germination and root growth inhibition bioassays, showed increasing plant sensitivity to the tested sewage sludges in the following order: cress > turnip > mustard > sorrel > tomato > sorgo > red clover > radish > cucumber > spinach. The EC50 sewage sludge values lay in the range 31-404 g/kg of soil, and significant relationships were found for most of the plants between EC50 and the magnesium content (Mg(2+): alpha = 0.888-0.924, P = 0.05), calcium content (Ca(2+): alpha = 0.813-0.911, P < or = 0.05), and pH (alpha = -0.913-0.948, P = 0.05). In the case of sewage sludge pollutants, significant relationships were found for trace metals such as: strontium (Sr: alpha = 0.851-0.948, P < or = 0.05), chromium (Cr: alpha = 0.858, P < or = 0.05), and nickel (Ni: alpha = 0.955, P = 0.05), as well as pyrene (PAHs).

The Tenax fraction of PAHs relates to effects in sewage sludges

In the present study a toxicity evaluation (Heterocypris incongruens, OstracodToxKit FTM Test) was carried out for ten municipal sewage sludges in relation to polycyclic aromatic hydrocarbon (PAH) contents in these sludges. PAHs content in the sewage sludges was determined by a vigorous extraction method and solid phase extraction with Tenax-TA. The main aim of the evaluation was establishing whether it was possible to determine the negative influence of PAHs in the sewage sludges on H. incongruens mortality and growth inhibition using the Tenax-TA method. H. inconguens showed increased growth inhibition and mortality when exposed to all sewage sludges. Significant relationships were noted between the content of some Tenax-TA PAH fractions and the total organic carbon content, cation exchange capacity and concentration of Ca(2+) ions. The toxicity was proportional to Tenax-TA concentrations and was not governed by the total concentration found in the sewage sludge.