Environmental health assessment of the benthic habitat adjacent to a pulp mill discharge. I. Acute and chronic toxicity of sediments to benthic macroinvertebrates

How do we take the pulse of an aquatic ecosystem? Current and historical approaches to measuring ecosystem integrity

Global environmental monitoring has indicated that the structure and function of some aquatic ecosystems has been significantly altered by human activities. There are many potential causes for these changes; however, one major concern is the increasing release of anthropogenic contaminants into aquatic environments. Although toxicological responses of individual organisms are typically well characterized, few studies have focused on characterizing toxicity at the ecosystem level. In fact, because of their scale and complexity, changes in ecosystem integrity are rarely considered in assessments of risks to ecosystems. This work attempts to move the conversation forward by defining integrity of ecosystems, reviewing current and historical approaches to measuring ecosystem integrity status (e.g., structural and functional measurements), and highlighting methods that could significantly contribute to the field of ecosystem toxicology (e.g., keystone species, environmental energetics, ecotoxicological modeling, and adverse outcome pathways [AOPs]). Through a critical analysis of current and historical methodologies, the present study offers a comprehensive, conceptual framework for the assessment of risks of contaminant exposure for whole ecosystems and proposes steps to facilitate better diagnoses of the integrity of aquatic systems. Environ Toxicol Chem 2019;38:289-301. © 2018 SETAC.

Comprehensive sediment toxicity assessment of Hessian surface waters using Lumbriculus variegatus and Chironomus riparius

The objective of this study was a sediment assessment of predominantly small rivers in the German federal state of Hesse. For this purpose, sediment samples were taken at 50 study sites with different contamination levels. The benthic invertebrates Chironomus riparius (Diptera) and Lumbriculus variegatus (Oligochaeta) were used as test species and exposed to whole sediments in chronic laboratory experiments. The bioassays were carried out on the basis of OECD guidelines 218 and 225 for the testing of chemicals. For about 50 % of the study sites chemical analytical data for pollutants from environmentally important substance classes like metals, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and organotin compounds were available. These data were used to analyze correlations between effects in the bioassays and measured chemical contaminations at sampling sites. For 22 % of the sediments ecologically relevant adverse effects were observed. In the majority of these cases effects occurred in only one of the biotests, and only one sediment sample exerted a negative effect on both test organisms. There was no significant correlation between biological responses and chemical data considering substance classes. However, there was a weak positive correlation between arsenic concentration and both worm number and worm biomass as well as a weak positive correlation between single PAHs and worm biomass. In some sediment tests elevated ammonia concentrations occurred in the overlying water so that an influence of these partially toxic concentrations on the test results cannot be ruled out.

Reduction of pollutants in pulp paper mill effluent treated by PCP-degrading bacterial strains

Two PCP-degrading bacterial strains, Bacillus cereus (ITRC-S6) and Serratia marcescens (ITRC-S7) were used for the treatment of pulp and paper mill effluent at conditions; 1.0% glucose and 0.5% peptone at 30 +/- 1 degrees C at 120 rpm for 168 h of incubation. These two bacterial strains effectively reduced colour (45-52%), lignin (30-42%), BOD (40-70%), COD (50-60%), total phenol (32-40%) and PCP (85-90%) within 168 h of incubation. However, the highest reduction in colour (62%), lignin (54%), BOD (70%), COD (90%), total phenol (90%) and PCP (100%) was recorded by mixed culture treatment. The bacterial mechanism for the degradation of pulp and paper mill effluent may be explained by an increase in the cells biomass using added co-substrates resulting liberation of significant amount of chloride due to bacterial dechlorination of chlorolignins and chlorophenols this showed reduction in colour, lignin and toxicity in the effluent. Further, GC-MS analysis of ethyl acetate-extractable compounds from treated pulp paper mill effluent reinforces the bacterium capability for the degradation of lignin and pentachlorophenol, as many aromatic compounds such as 2-chlorophenol, 2, 4, 6-trichlorophenol and tetrachlorohydroquinone, 6-chlorohydroxyquinol and tetrachlorohydroquinone detected which were not present in the untreated effluent.

The effectiveness of a biological treatment with Rhizopus oryzae and of a photo-Fenton oxidation in the mitigation of toxicity of a bleached kraft pulp mill effluent

Huge efforts have been made both in adopting more environmental-friendly bleaching processes, and in developing advanced oxidation processes and more effective biological treatments for the reduction of deleterious impacts of paper mill effluents. Even so, the success of such treatments is frequently reported in terms of chemical parameters without a proper evaluation of the effluent's toxicity mitigation. This is the first study reporting an exhaustive evaluation of the toxicity of a secondary bleached kraft pulp mill effluent, after either tertiary treatment with the soft-rot fungi Rhizopus oryzae or with a photo-Fenton oxidation, using a battery of freshwater species. As it has been reported the photo-Fenton/UV treatment has proved to be the most effective in reducing the colour and the COD (chemical oxygen demand) of the effluent. Nevertheless, extremely low EC(50) values were reported for almost all species, after this tertiary treatment. The treatment with R. oryzae was less effective in terms of colour removal and COD reduction, but proved to be the most promising in reducing toxicity.

Acute and chronic toxicity of effluent water from an abandoned uranium mine

Inactive or abandoned mines represent a significant source of environmental, chemical, physical, and aesthetic impact. Among concerning situations, the occurrence of abandoned or semi-abandoned mine-associated ponds (for sedimentation of solids, for effluent neutralization, or for washing the ore) is a common feature in this type of system. These ponds are a source of contamination for the groundwater resources and adjacent soils, because they lack appropriate impermeabilization. The use of this water for agriculture may also pose chronic risks to humans. In Portugal, these problems have been diagnosed and some remediation projects have been developed. The purpose of our study was to evaluate the acute and chronic toxicity of water samples collected from the aquatic system surrounding an abandoned uranium mine (Cunha Baixa, Mangualde, Central Portugal). The present study focuses on the water compartment, whose toxicity was evaluated by means of standard toxicity assays using two Daphnia species (D. longispina and D. magna). Three different ponds were used in the characterization of the aquatic system from Cunha Baixa mine: a reference pond (Ref), a mine effluent treatment pond (T), and a mine pit pond (M). Metal analyses performed in the water samples from these ponds showed values that, in some cases, were much higher than maximum recommendable values established (especially Al, Mn) by Portuguese legislation for waters for crop irrigation. Acute toxicity was only observed in the mine pit pond, with EC(50) values of 28.4% and 50.4% for D. longispina and D. magna, respectively. The significant impairment of chronic endpoints, translated in reductions in the population growth rate for both species, gives rise to concerns regarding the potential risks for aquatic zooplanktonic communities, from local receiving waters, potentially exposed to point source discharges of the treated and nontreated effluent from Cunha Baixa uranium mine.

Decolourisation and detoxification of synthetic molasses melanoidins by individual and mixed cultures of Bacillus spp

The decolourisation of synthetic melanoidins (i.e., GGA, GAA, SGA, and SAA) by three Bacillus isolates (Bacillus thuringiensis (MTCC 4714), Bacillus brevis (MTCC 4716) and Bacillus sp. (MTCC 6506)) was studied. Significant reduction in the values of physicochemical parameters was noticed alongwith the decolourisation of all four melanoidins (10% v/v). B. thuringiensis (MTCC 4714) caused maximum decolourisation followed by B. brevis (MTCC 4716) and Bacillus sp. (MTCC 6506). A mixed culture comprised of these three strains was capable of decolourising all four melanoidins. The medium that contained glucose as a sole carbon source showed 15% more decolourisation than that containing both carbon and nitrogen sources. Melanoidin SGA was maximally decolourised (50%) while melanoidin GAA was decolourised least ( approximately 06%) in the presence of glucose as a sole energy source. The addition of 1% glucose as a supplementary carbon source was essential for co-metabolism of melanoidin complex. The decolourisation of synthetic melanoidin by three Bacillus spp. significantly reduced the toxicity to the tubificid worm (Tubifex tubifex, Müller).

Is the 1:4 elutriation ratio reliable? Ecotoxicological comparison of four different sediment: water proportions

Methodological research was carried out to evaluate the discriminatory capability of three toxicity bioassays toward different elutriation ratios (1:4, 1:20, 1:50, and 1:200 sediment:water ratios). Samples from six sampling stations of the Lagoon of Venice have been investigated. The toxicity bioassay results (sea urchin Paracentrotus lividus Lmk sperm cell and embryo toxicity bioassays and bivalve mollusk Crassostrea gigas Thunberg embryo toxicity bioassays) have shown that elutriates generated from the widely used 1:4 ratio were less toxic than those from intermediate ratios (1:20 and 1:50).

Effects of pulp and paper mill effluents on the microplankton and microbial self-purification capabilities of the Biobío River, Chile

Most studies focus on the ecotoxicity of pulp and paper mill effluents, rather than on how they affect the physicochemical and biological structure and the intrinsic ecological capabilities of the receiving watercourses. We investigated the impact of such effluents on the water quality, microplankton system and microbial self-purification capacity (degradation of polymeric organic compounds via extracellular enzymes) of the Biobío River in Chile. The physicochemical impact on the water quality was indicated by raised conductivity, by the pollution of the water body with nitrate, nitrite and soluble reactive phosphorus, by the appearance of tannin and lignin, and by the steady accumulation of inorganic and organic suspended matter (SPM) along the river. From the biological structure of the microplankton system, very low and declining concentrations of chlorophyll a and heterotrophic flagellate densities were determined. The pulp and paper mill effluents introduced high bacterial abundances and biomass concentrations into the river water. This reflects the effective use made of the abundantly available inorganic and organic nutrients within this industrial and municipal process water by bacteria adapted to these extreme environments, additionally supported by concomitant low grazing pressure derivable from low heterotrophic flagellate abundances. Indeed, in one section of the river affected by a pulp mill, the plant was found to significantly contribute to the self-cleaning capacity of the river. However, this elevated degradation capacity was not enough to compensate for the additionally discharged organic material which, together with the toxic effects of the paper plant effluents, significantly interferes with the ecological status of the Biobío River.

Toxicity evaluation by using intact sediments and sediment extracts

The toxicity of intact sediments and sediment extracts, from both an uncontaminated site and a site contaminated by pulp-mill effluents, was tested in a five months study. The deposit-feeding amphipod Monoporeia affinis was exposed in soft-bottom flow-through water microcosms. To examine potential toxicity a set of reproduction endpoints was used including fecundity and different embryo aberrations such as malformed eggs. Among extracts, the aliphatic/monoaromatic and diaromatic fractions along with the total extract were shown to cause the highest toxicity measured as malformed eggs, while the polyaromatic fraction caused toxicity at background levels. A comparison between sediment extracts and pulp mill contaminated intact sediment, however, showed no toxicity of the intact sediment. Thus, the extraction procedure seems to increase bioavailability and subsequently toxicity as compared to the intact sediments in situ. In toxicity testing using fractionated extracts of sediments in a toxicity identification evaluation (TIE) procedures, caution should therefore be taken when assessing bioavailable contaminants in contaminated areas. This should be taken in account both in determining remediation priorities as well as in ecological risk assessments.

In situ and laboratory bioassays to evaluate the impact of effluent discharges on receiving aquatic ecosystems

Effluents are a main source of direct and often continuous input of pollutants into aquatic ecosystems with long-term implications on ecosystem functioning. Therefore, the study of the effects of effluent exposure on organisms, populations or communities within the framework of impact assessment has a high ecological relevance. The aim of this study was to assess the toxicological impact of two effluents, one household wastewater treatment effluent (Effluent 1) and one industrial effluent (Effluent 2), on the receiving aquatic ecosystem using two test species under both in situ and laboratory conditions. Zebra mussel (Dreissena polymorpha) and common carp (Cyprinus carpio) were exposed under laboratory conditions in an online monitoring flow-through system (receiving different concentrations of Effluent 2) and under in situ conditions along the pollution gradient established by these two effluent discharges. Bioassays focussed on growth and condition related endpoints (i.e. condition, growth, lipid budget), since these are key functional processes within organisms and populations. Under laboratory conditions, increasing concentrations of the industrial effluent (Effluent 2) had a negative effect on both zebra mussel and carp energy reserves and condition. Under in situ conditions, the same negative impact of Effluent 2 was observed for zebra mussels, while Effluent 1 had no apparent effect on exposed zebra mussels. Carp growth and condition, on the other hand, were significantly increased at the discharge sites of both effluents when compared to the reference site, probably due to differences in food availability. The results indicate that a combination of in situ and laboratory exposures can illustrate how ecological processes influence bioassay studies. The incorporation of indirect, ecological effects, like changes in food availability, provides considerable benefit in understanding and predicting effects of effluents on selected species under realistic exposure conditions.

Evaluation of ecological disturbance and intrinsic bioremediation potential of pulp mill-contaminated lake sediment using key enzymes as probes

A rapid protocol was developed to measure 10 different enzymic activities from a large number of 1-cm-sliced freshly collected lake sediments. Layers heavily polluted by organic halogens (4900 mg Cl kg(-1)) revealed severe depression of phosphatase, sulfatase, leucine-aminopeptidase, chitinase, acetate esterase and butyrate esterase activities as compared to layers above and below the most polluted zone. alpha-Glucosidase, beta-glucosidase, beta-xylosidase and palmitate esterase were less affected. Methane oxidation potential was dramatically depressed in the polluted strata whereas tetrachloromethane dehalogenating activity was observed in the polluted sediment only. The sediment layers formed after the chlorine discharges into the lake had diminished to 1/10, and showed restoration of the activities close to those observed in non-recipient sediment, in spite of the persisting presence of >1000 mg of organic chlorine (kg dry wt)(-1). We conclude that certain enzymic activities involved in breakdown or oxidation of organic matter in the sediments are useful probes for assessing the degree of ecological damage and its potential for restoration in recipient lakes of industrial discharges.

Decolorization and detoxification of extraction-stage effluent from chlorine bleaching of kraft pulp by Rhizopus oryzae

Rhizopus oryzae, a zygomycete, was found to decolorize, dechlorinate, and detoxify bleach plant effluent at lower cosubstrate concentrations than the basidiomycetes previously investigated. With glucose at 1 g/liter, this fungus removed 92 to 95% of the color, 50% of the chemical oxygen demand, 72% of the adsorbable organic halide, and 37% of the extractable organic halide in 24 h at temperatures of 25 to 45 degrees C and a pH of 3 to 5. Even without added cosubstrate the fungus removed up to 78% of the color. Monomeric chlorinated aromatic compounds were removed almost completely, and toxicity to zebra fish was eliminated. The fungal mycelium could be immobilized in polyurethane foam and used repeatedly to treat batches of effluent. The residue after treatment was not further improved by exposure to fresh R. oryzae mycelium.