Efficiency of a cleanup technology to remove mercury from natural waters by means of rice husk biowaste: ecotoxicological and chemical approach

In the present work, the efficiency of rice husk to remove Hg(II) from river waters spiked with realistic environmental concentrations of this metal (μg L^?1 range) was evaluated. The residual levels of Hg(II) obtained after the remediation process were compared with the guideline values for effluents discharges and water for human consumption, and the ecotoxicological effects using organisms of different trophic levels were assessed. The rice husk sorbent proved to be useful in decreasing Hg(II) contamination in river waters, by reducing the levels of Hg(II) to values of ca. 8.0 and 34 μg L^?1, for an Hg(II) initial concentration of 50 and 500 μg L^?1, respectively. The remediation process with rice husk biowaste was extremely efficient in river waters spiked with lower levels of Hg(II), being able to eliminate the toxicity to the exposed organisms algae Pseudokirchneriella subcapitata and rotifer Brachionus calyciflorus and ensure the total survival of Daphnia magna species. For concentrations of Hg(II) tenfold higher (500 μg L^?1), the remediation process was not adequate in the detoxification process, still, the rice husk material was able to reduce considerably the toxicity to the bacteria Vibrio fischeri, algae P. subcapitata and rotifer B. calyciflorus, whose responses where fully inhibited during its exposure to the non-remediated river water. The use of a battery of bioassays with organisms from different trophic levels and whose sensitivity revealed to be different and dependent on the levels of Hg(II) contamination proved to be much more accurate in predicting the ecotoxicological hazard assessment of the detoxification process by means of rice husk biowaste.     

Aquatic microcosm assessment of the effects of tylosin on Lemna gibba and Myriophyllum spicatum

Tylosin is a macrolide antibiotic commonly used for therapeutic treatment and prophylaxis in livestock. As part of a larger ecotoxicological study, the potential phytotoxic effects of tylosin on the rooted macrophyte Myriophyllum spicatum and the floating macrophyte Lemna gibba were assessed under semi-field conditions using 15 12 000-L microcosms. Concentrations of 0, 10, 30, 300 microg/L (n = 3), and 600, 1000, and 3000 microg/L (n = 1) were evaluated as part of separate ANOVA and regression analyses over an exposure period of 35 days. Fate of tylosin was monitored over time in the highest three treatments, where dissipation followed pseudo-first order kinetics with associated half-lives ranging from 9 to 10 days. For both M. spicatum and L. gibba, tylosin was found to cause no biologically significant changes to any endpoint assessed compared to controls at a Type I error rate of 0.1. However, subsequent power analyses revealed that there was generally insufficient power to declare that there were no significant differences at a Type II error rate of 0.2. Conclusions concerning biologically significant impacts were therefore further assessed based on other statistical criteria including comparisons of percent differences between replicated treatments and controls, minimum significant and minimum detectable differences, and coefficients of variation. Based on these criteria, at an ecological effect size of >20% change, tylosin was concluded to elicit no biologically or ecologically significant toxicity to M. spicatum or L. gibba. A hazard quotient assessment indicated that tylosin poses little risk to either species of macrophyte, with an HQ value calculated to be nearly three orders of magnitude below 1 (0.002).     

Nitrogen oxide emission calculation for post-Panamax container ships by using engine operation power probability as weighting factor: A slow-steaming case

In this study, the nitrogen oxide (NO_x) emission factors and total NO_x emissions of two groups of post-Panamax container ships operating on a long-term slow-steaming basis along Euro–Asian routes were calculated using both the probability density function of engine power levels and the NO_x emission function. The main engines of the five sister ships in Group I satisfied the Tier I emission limit stipulated in MARPOL (International Convention for the Prevention of Pollution from Ships) Annex VI, and those in Group II satisfied the Tier II limit. The calculated NO_x emission factors of the Group I and Group II ships were 14.73 and 17.85 g/kWhr, respectively. The total NO_x emissions of the Group II ships were determined to be 4.4% greater than those of the Group I ships. When the Tier II certification value was used to calculate the average total NO_x emissions of Group II engines, the result was lower than the actual value by 21.9%. Although fuel consumption and carbon dioxide (CO₂) emissions were increased by 1.76% because of slow steaming, the NO_x emissions were markedly reduced by 17.2%. The proposed method is more effective and accurate than the NO_x Technical Code 2008. Furthermore, it can be more appropriately applied to determine the NO_x emissions of international shipping inventory.

Implications: The usage of operating power probability density function of diesel engines as the weighting factor and the NO_x emission function obtained from test bed for calculating NO_x emissions is more accurate and practical. The proposed method is suitable for all types and purposes of diesel engines, irrespective of their operating power level. The method can be used to effectively determine the NO_x emissions of international shipping and inventory applications and should be considered in determining the carbon tax to be imposed in the future.     

Leaching of terbumeton and terbumeton-desethyl from mini-columns packed with soil aggregates in laboratory conditions

Leaching of terbumeton (TER) and terbumeton-desethyl (TED) from mini-columns packed with natural soil aggregates was investigated. Five soil samples from the Champagne area (France) with different physicochemical parameters were used. The soil samples were hand-packed into a 50 mm column in laboratory conditions. An aqueous solution of TER or TED was percolated through the column and collected effluents were analyzed for TER or TED using HPLC-DAD. The leaching experiments showed that TER and TED were moderately mobile. TED was more mobile than TER, possibly because of its higher polarity. The proportion of organic matter affected the mobility of TER and TED through soil columns (r=0.971) and leaching was lowest for soil having the highest organic matter content (5.9%). TER and TED were not significantly influenced by leaching solution composition (deionized water or CaCl(2) solution), but were strongly affected by soil packing. Packing resulted in less rapid release of compounds suggesting that unpacking may have contributed to preferential pathways through the soil columns. Increasing contact time between TER and soils before leaching decreased the mobility of TER and increased its persistence in soils. Indeed, 76% of TER was released when leaching started after a 15 h contact time whereas it was down to 26% after an aging treatment of 360 h. A proportion of TER (from 8% to 32%) and TED (from 8% to 17%) remained in soil. Associated to its high stability in soils this could in part account for a very slow transfer over the years towards the groundwater.     

Interaction effects of metals and salinity on biodegradation of a complex hydrocarbon waste

The presence of high levels of salts because of produced brine water disposal at flare pits and the presence of metals at sufficient concentrations to impact microbial activity are of concern to bioremediation of flare pit waste in the upstream oil and gas industry. Two slurry-phase biotreatment experiments based on three-level factorial statistical experimental design were conducted with a flare pit waste. The experiments separately studied the primary effect of cadmium [Cd(II)] and interaction effect between Cd(II) and salinity and the primary effect of zinc [Zn(II)] and interaction effect between Zn(II) and salinity on hydrocarbon biodegradation. The results showed 42-52.5% hydrocarbon removal in slurries spiked with Cd and 47-62.5% in the slurries spiked with Zn. The analysis of variance showed that the primary effects of Cd and Cd-salinity interaction were statistically significant on hydrocarbon degradation. The primary effects of Zn and the Zn-salinity interaction were statistically insignificant, whereas the quadratic effect of Zn was highly significant on hydrocarbon degradation. The study on effects of metallic chloro-complexes showed that the total aqueous concentration of Cd or Zn does not give a reliable indication of overall toxicity to the microbial activity in the presence of high salinity levels.     

Interaction Effects of Metals and Salinity on Biodegradation of a Complex Hydrocarbon Waste

Abstract

The presence of high levels of salts because of produced brine water disposal at flare pits and the presence of metals at sufficient concentrations to impact microbial activity are of concern to bioremediation of flare pit waste in the upstream oil and gas industry. Two slurry-phase biotreatment experiments based on three-level factorial statistical experimental design were conducted with a flare pit waste. The experiments separately studied the primary effect of cadmium [Cd(II)] and interaction effect between Cd(II) and salinity and the primary effect of zinc [Zn(II)] and interactioneffect between Zn(II) and salinity on hydrocarbon biodegradation. The results showed 42–52.5% hydrocarbon removal in slurries spiked with Cd and 47–62.5% in the slurries spiked with Zn. The analysis of variance showed that the primary effects of Cd and Cd–salinity interaction were statistically significant on hydrocarbon degradation. The primary effects of Zn and the Zn-salinity interaction were statistically insignificant, whereas the quadratic effect of Zn was highly significant on hydrocarbon degradation. The study on effects of metallic chloro-complexes showed that the total aqueous concentration of Cd or Zn does not give a reliable indication of overall toxicity to the microbial activity in the presence of high salinity levels.     

Toxic effect of metal cation binary mixtures to the seaweed Gracilaria domingensis (Gracilariales,Rhodophyta)

The macroalga Gracilaria domingensis is an important resource for the food, pharmaceutical, cosmetic, and biotechnology industries. G. domingensis is at a part of the food web foundation, providing nutrients and microelements to upper levels. As seaweed storage metals in the vacuoles, they are considered the main vectors to magnify these toxic elements. This work describes the evaluation of the toxicity of binary mixtures of available metal cations based on the growth rates of G. domingensis over a 48-h exposure. The interactive effects of each binary mixture were determined using a toxic unit (TU) concept that was the sum of the relative contribution of each toxicant and calculated using the ratio between the toxicant concentration and its endpoint. Mixtures of Cd(II)/Cu(II) and Zn(II)/Ca(II) demonstrated to be additive; Cu(II)/Zn(II), Cu(II)/Mg(II), Cu(II)/Ca(II), Zn(II)/Mg(II), and Ca(II)/Mg(II) mixtures were synergistic, and all interactions studied with Cd(II) were antagonistic. Hypotheses that explain the toxicity of binary mixtures at the molecular level are also suggested. These results represent the first effort to characterize the combined effect of available metal cations, based on the TU concept on seaweed in a total controlled medium. The results presented here are invaluable to the understanding of seaweed metal cation toxicity in the marine environment, the mechanism of toxicity action and how the tolerance of the organism.     

Comparing aquatic risk assessment methods for the photosynthesis-inhibiting herbicides metribuzin and metamitron

Three different risk assessment procedures are described that aim to protect freshwater habitats from risks of the photosynthesis-inhibiting herbicides metribuzin and metamitron. These procedures are (1) the first-tier approach, based on standard toxicity tests and the application of an assessment factor, (2) the Species Sensitivity Distribution (SSD) approach, based on laboratory tests with a wider array of species and the application of a statistical model to calculate the HCx (the Hazardous Concentration for x% of the species), and (3) the model ecosystem approach, based on the evaluation of treatment-related effects in field enclosures. A comparison of the risk assessment procedures reveals that the first-tier approach is the most conservative for metamitron and metribuzin, and that HC5 values (and even HC10 values) based on acute EC50 values of algae and aquatic vascular plants may be used to derive maximum permissible concentrations for single applications. For both compounds these HC5 values were very similar to the ecological threshold concentrations in the enclosure studies. In contrast to model ecosystem experiments, however, HCx values based on lab toxicity tests do not provide information on the recovery potential of sensitive endpoints and on indirect effects, which may be important for regulatory decision-making. In the enclosure study, indirect effects of metribuzin on invertebrate populations were observed at an exposure concentration that was approximately 20 times lower than the corresponding HC5 value based on lab toxicity data for aquatic invertebrates.     

Toxicity evaluation of reactive dyestuffs, auxiliaries and selected effluents in textile finishing industry to luminescent bacteria Vibrio fischeri

The toxicity of 17 selected process effluents, 11 reactive dyestuffs and 8 auxiliaries from a textile dyeing and finishing mill in Ayazaga, Istanbul, Turkey was evaluated by bioluminescence test using bacteria Vibrio fischeri in LUMIStox 300. The EC20 and EC50 for auxiliaries, the EC20 for dyestuffs were determined. For selected process effluents GL-values, the dilution level at which a wastewater sample causes less than 20% inhibition, were examined. Our results demonstrate that the toxicity assessment with luminescent bacteria is effective and of practical use for chemicals applied in textile finishing industry with the limitation of the deep dark-colored dye bath samples and for the related effluents. Inhibition effects of numerous dyestuffs as well as auxiliaries to luminescent bacteria differed considerably with a range 5-600 mg l(-1) for EC20 and 9-6930 mg l(-1) for EC50, respectively. Among 17 effluents, I sample exhibited high toxicity (GL = 100), 7 showed moderate toxicity (GL = 12-32), and 9 had a GL-value <10 indicating a low or no toxicity.     

Assessment of the mechanisms of detoxification of chemical compounds and antioxidant enzymes in the digestive gland of mussels, Mytilus galloprovincialis, from Mediterranean coastal sites

In this study the effects of the main marine pollutants (metals, PAHs, PCBs and DDTs) were assessed in native mussels from the Mediterranean coast of Spain. For this purpose several biomarkers such as benzo[a]pyrene hydroxylase (BPH), DT-diaphorase (DTD), glutathione S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPs), glutathione reductase (GR), metallothionein (MT) and lipid peroxidation (LPO) were measured in the digestive gland. Results showed increased LPO levels in mussels which accumulated high loads of organic compounds and arsenic in their tissues. BPH levels correlated to the concentrations of organic compounds in mussel tissues, though the range of BPH response was low in relation to the high gradient of accumulation of organic pollutants. Increased BPH levels, concomitant to low DTD and GST activities, were detected in mussels which presented high levels of organic pollutants in their tissues. This suggests that signs of LPO present in these organisms are related to the imbalance between phase I and phase II biotransformation processes. Furthermore, the increased levels of MT and CAT detected in mussels which showed high levels of Cd in their tissues appear to reflect a coordinated response which protects against the toxicity of this metal. The application of these biomarkers in environmental assessment is discussed.     

Growth rate effects, responses of antioxidant enzymes and metabolic fate of the herbicide Propanil in the aquatic plant Lemna minor

Propanil (3,4-dichloropropionanilide) is a selective contact pesticide, recommended for post-emergence use in rice. This herbicide may end up in surface waters and present potential risk for aquatic vascular plants. Therefore, its toxicity was evaluated on Lemna minor L., an aquatic plant regularly used for toxicological studies, during time- and concentration-dependent exposure. Toxicity assessments were based on inhibition of growth of L. minor cultures after 24 days. The obtained results showed that the growth of Lemna was affected by the herbicide. The responses of the guaiacol peroxidase (G-POD) and glutathione S-transferase (GST) involved in the xenobiotic metabolism and antioxidative system were also investigated following Propanil exposure. Our results showed that Propanil has not induced enzymatic antioxidative defenses of L. minor. Both 3,4-dichloroaniline (3,4-DCA) and 3,4-dichloroacetanilide are the major metabolites in this plant. On the contrary, only 3,4-DCA was found in culture media after 4 days. Probably, the enzymatic hydrolysis by acyl acylamidase and the acetylation by acetyl-CoA are the major pathways for these transformation products, respectively. The results of this study showed that the selected aquatic plant has the potential to accumulate and metabolize rice herbicide, like Propanil. Based on these toxicity data this herbicide should impair the establishment of non-target aquatic plants.     

Integrative assessment of marine pollution in Galician estuaries using sediment chemistry,mussel bioaccumulation,and embryo-larval toxicity bioassays

An integrative assessment of environmental quality was carried out in selected sites along the Galician coast (NW Iberian Peninsula) combining analytical chemistry of seawater and sediments, bioaccumulation in the marine mussel, and embryo-larval sediment toxicity bioassays, in order to link biological and chemical criteria for the assessment of coastal pollution. Maximum values of Hg and Cu in seawater, sediment and mussels, were found in the inner part of Ria of Pontevedra, while maximum levels of organics (polychlorinated biphenyls, hexachlorobenzene and aldrin) were found in mussels from A Coru?a. Outstanding values of Cu, Pb and Zn have been found in seawater and sediment from a single site, P3, which also was the most toxic in the embryo-larval bioassays performed with four different phyla of marine organisms: mollusks, echinoderms, arthropods and chordates. Sediment quality effects range-median values provided a valuable reference to predict biological effects from sediment chemistry data, while effects range-low values were too conservative. Sediment toxicity could also be predicted by using a toxic-unit model based on published EC50 values for trace metals and mobilization factors independently obtained from measurements of metal contents in sediments and their elutriates. When chemical and toxicological data are independently used to arrange sampling sites by using non-metric multidimensional scaling, a remarkable degree of concordance between both types of configurations could be observed.     

Methodology for conducting screening-level ecological risk assessments for hazardous waste sites. Part III: exposure and effects assessment

The Idaho National Engineering and Environmental Laboratory (INEEL) has implemented a phased approach to ecological risk assessment (ERA). The first step in this process is a screening-level ERA at each facility. Basic to this approach was the development of ecologically based screening levels (EBSLs), defined as concentrations of chemicals in soil (or other media) that are not expected to produce any adverse effects on selected ecological receptors under chronic exposure conditions (analogous to preliminary remediation goals or soil screening levels). EBSLs are calculated by rearrangement of standard exposure equations to solve for soil concentration when chemical intake rate is set at a developed toxicity reference value (TRV). A TRV is defined as a chronic dose that is likely to be without appreciable risk of deleterious effects. This definition was extended to define TRVs and ultimately EBSLs for the functional groups used in the INEEL screening-level ERAS.     

Effects of As levels on radial oxygen loss and As speciation in rice

Greenhouse experiment was conducted to examine effects of arsenic (As) on iron plaque formation, radial oxygen loss, As accumulation, and speciation in rice. Three genotypes were grown in soil with three different concentrations of As. The stress of As caused a slight increase of iron plaque formation (P?>?0.05) and a decrease in the rates of radial oxygen loss (ROL; P?<?0.01). The results of As speciation showed that the percentages of DMA increased from 19–28 % to 53–58 %, while the percentages of inorganic As decreased from 53–58 % to 36–42 % with the increasing soil As concentrations, indicating a strong environmental influence on As species in rice grain. The present study showed that elevated soil As may induce As toxicity towards rice plants, leading to the decrease of ROL; environmental factors could influence As methylation or As species transportation. Our study provided useful information on As tolerance and accumulation in rice which may contribute to reducing the health risk posed by As contamination in rice.     

Biosorption of heavy metals using rice milling by-products. Characterisation and application for removal of metals from aqueous effluents

The morphological characteristics as well as chemical composition of rice husks were evaluated by different techniques such as spectroscopy and thermogravimetry. The material, which is considered a by-product obtained from rice milling, was then investigated as a potential decontaminant of toxic heavy metals present in laboratory effluents. Studies using glass columns were carried out at room temperature employing 100 ml of synthetic solutions containing Cd(II) and Pb(II) at 100 mg l(-1) in order to study the effects of pH, flow rate and particle size on Cd(II) and Pb(II) adsorption. After establishing the optimised conditions, the potentiality of rice husks for removing Cd(II) and Pb(II) ions from 100 ml of laboratory effluent, presenting concentrations before treatment of 22 and 12 mg l(-1), respectively, was evaluated. The ability to take up other metals species, such as Al(III), Cu(II) and Zn(II), present in this effluent was also studied. According to the data obtained, under the optimised conditions (pH=4.0, flow rate of 8.0 ml min(-1) and < or =355 microm rice husk particle size), 30 g of husks were necessary to attain the permissible limits for effluent release, as recommend by the EPA, for those species evolved in this work (Al, Cd, Cu, Pb and Zn).     

Evaluation of the cytotoxic effects of glyphosate herbicides in human liver,lung, and nerve

Glyphosate-based herbicides are broad-spectrum pesticides widely used in the world, which is considered a highly safe pesticide due to their target specificity, but recently, there has been an ongoing controversy regarding their carcinogenicity and possible side effects of glyphosate on human health. Commercial glyphosate-based herbicides (GBHs) consist of declared active ingredient (glyphosate salts) and a number of formulants such as ethoxylated formulants (4130®, 3780^®, and A-178^®). The aim of our study is to investigate whether the toxicity of GBHs is related to formulants. The effects of GBHs on human health were studied at the cellular level based on their toxicity to liver, lungs and nerve tissue. The inhibitory toxicity to cell viability by GBHs was examined with cell-based systems using three human cell lines: HepG2, A549, and SH-SY5Y. Data obtained showed that all tested ethoxylated formulants and their mixtures with declared active ingredient glyphosate isopropylamine salt (GP) have significant inhibitory effect on cell proliferation, while the declared active ingredient has no significant toxicity. Our study demonstrates that the toxic effect of GBH is primarily due to the use of formulants. This result suggests that GP is relatively safe and a new approach for the assessment of toxicity should be made.     

Hydraulic residence time effects on performance of an activated sludge unit treating wastewater containing dichlorophenol.

Wastewaters containing chlorophenol compounds are difficult to treat by biological means because of the toxic effects of those compounds on microorganisms. To investigate the adverse effects of chlorophenols on microorganisms, synthetic wastewater containing 2,4 dichlorophenol (DCP) was biologically treated in an activated sludge unit at different hydraulic residence times (HRTs) between 5 and 40 hours, whereas the feed chemical oxygen demand (COD), DCP concentrations, and sludge age were kept constant at 2500 +/- 50 mg/L, 150 mg/L, and 20 days, respectively. The resazurin method based on dehydrogenase activity was used for assessment of the feed and effluent wastewater toxicity. Percent COD, DCP, and toxicity removals increased, and the effluent COD, DCP, and toxicity levels decreased with increasing HRT. Biomass concentration in the aeration tank increased with increasing HRT because of low levels of DCP at high HRT levels, resulting in high COD, DCP, and toxicity removals. The sludge volume index decreased with increasing HRT, yielding well-settling organisms as a result of low levels of toxicity and high concentrations of active cells. Percent DCP and COD removals decreased with increasing specific DCP loading rate. The rates of DCP and COD removals showed a maximum at a low DCP concentration of 6 mg/L in the aeration tank, corresponding to a 25-hour HRT.     

A mathematical algorithm to identify toxicity and prioritize pollutants in field sediments

In order to evaluate sediment toxicity, a mathematical algorithm was developed to compute the toxicity of multiple component mixtures acting in an additive manner. A statistical approach was devised to determine the presence of potential interactive effects among mixture components. The algorithm uses three kinds of data to obtain an integrative approach to sediment toxicity assessment: Microtox toxicity data (EC50 values), sediment pollutant concentration measurements, and sequential extraction (SEQ) data to investigate metal partitioning. To simplify the analysis of complex mixtures using a prioritization scheme based on intrinsic toxicity and relative abundance, a toxicity index (TI) was employed as an indicator of adverse ecological impact. In general, the ranking of contaminants using the TI approach was found to be most efficient in reducing computational time, and concentrations using bioavailability data from SEQ was found to be the best theoretical predictor of the experimental mixture toxicity value. Only a few pollutants that were present at the greatest abundance were needed to provide a good approximation of the calculated EC50 found when all components were included. Not only does this substantially reduce the computational time needed to determine the EC50, it could in some cases dramatically reduce the pollutant monitoring effort required to track toxicity effectively. This approach would have substantial implications for both risk assessment and for remediation strategies, making them more efficient by focusing on the priority pollutants identified.     

Human health risk assessment case study: an abandoned metal smelter site in Poland

United States Environmental Protection Agency methodologies for human health risk assessment (HRA) were applied in a Brownfields Demonstration Project on the Warynski smelter site (WSS), an abandoned industrial site at Piekary Slaskie town, Upper Silesia, Poland. The HRA included the baseline risk assessment (BRA) and the development of risk-based preliminary remedial goals (RBPRGs). The HRA focused on surface area covered with waste materials, which were evaluated with regard to the potential risks they may pose to humans. Cadmium, copper, iron, manganese, lead, and zinc were proposed as the contaminants of potential concern (COPCs) at WSS based on archive data on chemical composition of waste located on WSS. For the defined future land use patterns, the industrial (I) and recreational (II) exposure scenarios were assumed and evaluated. The combined hazard index for all COPCs was 3.1E+00 for Scenario I and 3.2E+00 for Scenario II. Regarding potential carcinogenic risks associated with the inhalation route, only cadmium was a contributor, with risks of 1.6E-06 and 2.6E-07 for Scenario I and Scenario II, respectively. The results of the BRA indicated that the potential health risks at WSS were mainly associated with waste material exposure to cadmium (industrial and recreational scenarios) and lead (industrial scenario). RBPRGs calculated under the industrial scenario were 1.17E+03 and 1.62E+03 mg/kg for cadmium and lead, respectively. The RBPRG for cadmium was 1.18E+03 mg/kg under the recreational scenario. The BRA results, as well as RBCs, are comparable for both scenarios, so it is impossible to prioritize land use patterns for WSS based on these results. For choosing a future land use pattern or an appropriate redevelopment option, different factors would be decisive in the decision-making process, e.g., social, market needs, technical feasibility and costs of redevelopment actions or acceptance of local community.