Contribution for tier 1 of the ecological risk assessment of Cunha Baixa uranium mine (Central Portugal): II. soil ecotoxicological screening

This study presents the first ecotoxicological data concerning the soils of the area surrounding the Cunha Baixa uranium mine. Our main goal was to categorise soils from the area based on their toxicity profiles using a battery of cost- and time-effective bioassays (elutriate approach - Microtox and Daphnia acute tests; whole-soil approach - Microtox and avoidance assays with Eisenia andrei), as a part of tier 1 of an ongoing Environmental Risk Assessment. No acute toxicity was found for any of the 10 sites/soils using Microtox or Daphnia. On the contrary, the behavioural response of E. andrei was found to be an extremely sensitive endpoint, allowing the discrimination of highly to moderately toxic soils based on their toxicity profiles (as a function of soil concentration). Soils exhibiting highest toxicity corresponded to areas subjected to runoffs or sludge deposition from the aquatic effluent, while non-toxic soils were farthest to the mine. Data obtained in avoidance assays strengthen the previous evaluation of risks based on chemical data and supported decisions about proceeding for tier 2.     

Responses in sediment bioassays used in the Netherlands: can observed toxicity be explained by routinely monitored priority pollutants?

In order to identify the cause of toxicity in sediments and suspended matter, a large number of samples with different degrees of contamination was taken at various locations in The Netherlands. Standard acute bioassays were carried out with the bacterium Vibrio fischeri, the rotifer Brachionus calyciflorus and the anostracan Thamnocephalus platyurus. Chronic standard tests were performed using the water flea Daphnia magna and larvae of the midge Chironomus riparius. Some novel bioassays were performed as well. Most toxic effects observed in standard bioassays with sediments from polluted sediments (class 3 and 4 on a scale of 0-4 according to the Dutch criteria) could be partly explained by toxic concentrations of known persistent priority pollutants, mainly heavy metals and occasionally polycyclic aromatic hydrocarbons. In some of the samples, ammonia toxicity was a confounding factor during testing. Suspended matter from the Meuse river at Eijsden, which may be considered as 'new' sediment (pollution class 2), was moderately to highly toxic in almost all bioassays. This could have been associated with a combination of heavy metals, PAHs and ammonia. At two locations from the Lake IJssel area with no apparent persistent pollution, moderate and strong effects were nonetheless observed in invertebrate tests. This might have been due to agricultural run-off of pesticides, which are not routinely measured in sediments. A few effects on V. fischeri in canals and a small stream could not be explained with standard chemical analysis, but seemed associated with the outlets of sewage water treatment plants and industrial effluents. Additional chemical analysis of pore water samples from five selected sediments yielded more identified substances such as phtalates, decanes, cosanes and fragrances, but it was estimated that their contribution to the effects observed on V. fischeri, D. magna and C. riparius was negligible.     

Selective removal of resin and fatty acids from mechanical pulp effluents by ozone

Fresh chemithermomechanical (CTMP) mill primary clarifier (combined) effluents were treated using a system capable of accurately applying small measured charges of ozone. It was shown that the efficiency of ozone transfer into effluent was much better than into water, and that there was no residual dissolved ozone. Small ozone charges destroyed high proportions of the total resin and fatty acids (RFAs) and juvabiones (JBs) present in the effluents. This effect diminished with increasing ozone charges. Likewise, effluent toxicity, as measured in the Microtox assay, decreased rapidly with the low ozone charges. The low charges of ozone were also shown to be effective in destroying both soluble and particulate RFAs. It was shown that there was a strong positive correlation between the RFA content and the acute toxicity of an effluent sample, and that all the acute toxicity was extractable with methyl-t-butyl ether. Both Microtox and Daphnia magna acute toxicity assays correlated with effluent RFA content, but the Microtox was somewhat more sensitive. Thus, ozone may be a useful economical treatment agent for selectively removing RFAs and toxicity from mill effluent streams.     

Toxicity of chlorpyrifos and TCP alone and in combination to Daphnia carinata: the influence of microbial degradation in natural water

The acute toxicity of chlorpyrifos and its principal metabolite 3,5,6-trichloropyridinol (TCP) alone and in combination to a cladoceran, Daphnia carinata, was studied in both cladoceran culture medium and natural water collected from a local suburban stream. TCP was found to be more toxic than its parent chemical chlorpyrifos to Daphnia survival in cladoceran culture medium. However, TCP in natural water was not toxic to D. carinata up to 2 microgL(-1). The LC(50) values for chlorpyrifos, TCP and chlorpyrifos+TCP were 0.24, 0.20 and 0.08 microgL(-1), respectively, in cladoceran culture medium. Although the parent chemicals and their degradation products co-exist in natural waters, the existing guidelines for water quality are based on individual chemicals. The results of this investigation suggest that chlorpyrifos and TCP can interact synergistically, additively or antagonistically, resulting in an increase or decrease in the overall toxicity of the mixture compared to individual compounds. The indigenous microorganisms in natural water could play a significant role in degradation of these compounds thereby influencing their toxicity in receiving waters. This study clearly suggests that the joint action of pesticides and their degradation products should be considered in the development of water quality guidelines. To our knowledge, this is the first study on the interactive effect of chlorpyrifos and TCP to a cladoceran and suggests that these two compounds are non-toxic when present together at concentrations up to 0.12 microgL(-1). However, these compounds together act additively at and above 0.5 microgL(-1) to fresh water invertebrates and therefore pollution with these compounds may adversely affect natural ecosystems.     

Bioaccumulation of mercury in benthic communities of a river ecosystem affected by mercury mining

The presence of mercury in the river Idrijca (Slovenia) is mainly due to 500 years of mercury mining in this region. In order to understand the cycling of mercury in the Idrijca ecosystem it is crucial to investigate the role of biota. This study is part of an ongoing investigation of mercury biogeochemistry in the river Idrijca, focusing on the accumulation and speciation of mercury in the lower levels of the food chain, namely filamentous algae, periphyton and macroinvertebrates. Mercury analysis and speciation in the biota and in water were performed during the spring, summer and autumn seasons at four locations on the river, representing different degrees of mercury contamination. Total (THg) and methyl mercury (MeHg) were measured. The results showed that the highest THg concentrations in biota correlate well with THg levels in sediments and water. The level of MeHg is spatially and seasonally variable, showing higher values at the most contaminated sites during the summer and autumn periods. The percentage of Hg as MeHg increases with the trophic level from water (0.1-0.8%), algae (0.5-1.3%), periphyton (1.6-8.8%) to macroinvertebrates (0.1-100%), which indicates active transformation, accumulation and magnification of mercury in the benthic organism of this heavily contaminated torrential river.     

Comparative temporal ecotoxicological study in a river basin influenced by petrochemical industries

An approach was developed to evaluate ecotoxicological effects in river basins impacted by anthropic industrial discharges. Genotoxicity was the first level of evaluation of the river water, but when cytotoxicity was associated with genotoxic effects, our research group added chronic assays allowing the assessment of the ontogenic cycle in environmental diagnosis. The genotoxicity of river water sampled during two periods was compared using the microscreen phage-induction and Salmonella/microsome assays. The study assessed the ability of these assays to diagnose environmental quality in an area where petrochemical impacts occur. The study was performed at six sampling sites using the Salmonella/microsome assay for 10 sampling periods and the microscreen phage-induction assay for 15 samplings. The percentage of mutagenic activity was higher at the sites sampled in front of the petrochemical complex in both periods, but there were more significant mutagenic responses in the first assessment. However, comparing the percentages of samples with mutagenic and cytotoxic activity observed during the two periods it becomes clear that there are more cytotoxic samples during the second period throughout the area studied. The genotoxic activity analyzed by the microscreen phage-induction assay was constant in the second period. Chronic toxicity studies with the microcrustacean Daphnia magna confirm the toxic effects observed. The mortality of individuals was higher at the site most influenced by the petrochemical complex, followed by the station located upstream from this area, while the formation of ephippial eggs was uniform at all stations. The rise in the toxic potential of the region detected by cytotoxic and chronic toxicity may interfere and probably impair the use of the Salmonella/microsome assay to determine the potential of the area, showing the importance of assay association to evaluate potentially contaminated areas.     

BHC(1,2,3,4,5,6-hexachlorocyclohexane) residue concentrations and their seasonal variation in aquatic environments in the kitakyushu district, Japan, 1970–1973

The BHC (χ-, β-, γ- and δ-isomer of 1,2,3,4,5,6-hexachlorocyclohexane) concentration in river water, reservoir and tap water in the Kitakyushu District was investigated during 1970–1973. The levels in surface water were high in summer and low in autumn, winter and spring. In tap water, little difference was observed compared with the raw water. These results demonstrate that the usual treatment process, rapid sand-filteration and disinfection with chlorine, has little effect on the removal of BHC. The yearly maximum concentration in surface water occurred in summer, the logarithm of these declined linearly over a period of years. The levels of BHC concentration in the bottom sediments were much higher than those in surface water, suggesting that BHC in surface water was concentrated in the bottom sediments.     

Evaluation of water treatment sludges toxicity using the Daphnia bioassay

Alum and ferric chloride sludges from two water treatment plants (WTPs) were analyzed regarding their physicochemical characteristics and toxicity to Daphnia similis. Experiments were carried out in the dry and rainy seasons. Acute and chronic toxicity was measured using survival and reproduction as measurement endpoints. No acute toxicity of the sludge was observed in 48 h exposure. Ferric chloride sludge caused chronic toxicity, demonstrated by low fecundity and some mortality, while alum sludge caused chronic toxicity characterized by low fecundity. Some sludge characteristics varied between samplings, including turbidity, solids contents, N, P and metal (Al and Fe) concentrations. These variables and the increase of chemical oxygen demand (COD) were identified as the main cause of degradation of the receiving waters. However, no relationship was observed between these variables and degree of toxicity. It is apparent from these results that water treatment sludges may be toxic and therefore may impair receiving waters. Alum sludge was less toxic than ferric chloride sludge.     

Acute toxicity of cresols, xylenols, and trimethylphenols to Daphnia magna Straus 1820

Twenty-four-hour IC50 values (50% immobilization concentration) for phenol, o-cresol, m-cresol, p-cresol, six xylenols, and three trimethylphenols were determined for Daphnia magna under static conditions. Our results show that cresols are more toxic than phenol, that xylenols do not exhibit significantly higher toxicity than cresols, and that trimethylphenols are less toxic than cresols. Thus, no direct relationship can be found between the number and position of methyl groups on the phenol nucleus and their acute toxicity to the water flea.     

Application of short-term bioassay guided chemical analysis for water quality of agricultural land run-off.

The effect of agricultural land run-off on the water quality of Lake Kojima, Japan, was investigated using a short-term bioassay-guided chemical analysis. Water samples were collected for 1 year starting from June 1995 to June 1996. Toxicity of the dissolved and adsorbed extracts in the water samples was evaluated using the Daphnia immobilization test and the concentrations of pesticides and putative toxic substance in the extracts were determined by high performance liquid chromatography. Most of the dissolved extracts caused immobilization of the test Daphnia magna at low concentrations during the period of paddy pesticide application. Some extracts were found to contain pesticides such as dymron, mefenacet and flutolanil, but their concentrations were too low to have a toxic effect on the daphnia. An unknown toxic compound, Peak C, was isolated from some river water samples, but it produced only a relatively weak toxicity to Daphnia. To better understand the impact of agricultural run-off on a receiving water body, the relationship between the observed toxicity and the concentrations of pesticides and Peak C in the water samples was studied both temporally and spatially.     

In situ aquatic bioassessment of pesticides applied on rice fields using a microalga and daphnids

This study assessed the effects of episodic contamination on a drainage canal adjacent to an area of intensive rice production (Coimbra, Portugal). Four monitoring periods were considered [i) before herbicide application (day -14), ii) at the first application day (day 0), iii) 3 or 5 and iv) 6 days after]. Each one consisted in three complementary evaluation lines: a) physico-chemical analyses, b) whole effluent toxicity (WET) assays with Pseudokirchneriella subcapitata, c) in situ bioassays to assess microalgae (P. subcapitata) growth, and the feeding rate and survival of Daphnia longispina and Daphnia magna. Study sites were located upstream, in a protected wetland (L1), and downstream, in the vicinity of rice fields (L2). Along with the application of agrochemicals, there was a general decrease of the water quality, especially in L2, due to nutrient and herbicide inputs. Herbicide peaks (on days 0, 5 and 6) in L2 water samples were recorded concomitantly or immediately after their application. Regarding the in situ bioassessment, the algae growth decrease from day 0 onwards in L1, whilst in L2 its inhibition was generally coherent with the decline of the water quality. Apparently, WET tests indicated that the limitation of nutrients could be affecting algae growth in L1, however, conclusions should be cautious. The feeding depression of daphnids occurred on days 0 and 5 for D. longispina and only on day 0 for D. magna, while significant reductions on survival were restricted to day 0 for both species. The impairments occurring on day 0 were linked to a potential increased toxicity driven by the ingestion of particle-bound herbicides and suspended particles. The feeding rate of daphnids provided an earlier indication of toxic impairments, though it is prompted the use of complementary endpoints and trophic levels in order to understand the cumulative effects due to various herbicide pulses.     

Ecotoxicological assessment of grey water treatment systems with Daphnia magna and Chironomus riparius

In order to meet environmental quality criteria, grey water was treated in four different ways: 1) aerobic 2) anaerobic + aerobic 3) aerobic + activated carbon 4) aerobic + ozone. Since each treatment has its own specific advantages and disadvantages, the aim of this study was to compare the ecotoxicity of differently treated grey water using Chironomus riparius (96 h test) and Daphnia magna (48 h and 21d test) as test organisms. Grey water exhibited acute toxicity to both test organisms. The aerobic and combined anaerobic + aerobic treatment eliminated mortality in the acute tests, but growth of C. riparius was still affected by these two effluents. Post-treatment by ozone and activated carbon completely removed the acute toxicity from grey water. In the chronic toxicity test the combined anaerobic + aerobic treatment strongly affected D. magna population growth rate (47%), while the aerobic treatment had a small (9%) but significant effect. Hence, aerobic treatment is the best option for biological treatment of grey water, removing most of the toxic effects of grey water. If advanced treatment is required, the treatment with either ozone or GAC were shown to be very effective in complete removal of toxicity from grey water.     

Plasticizer metabolites in the environment

Earlier work with pure cultures had shown that the interaction of microbes with plasticizers leads to the formation of metabolites including 2-ethylhexanoic acid and 2-ethylhexanol that resist further degradation. The presence of these metabolites is now reported in a variety of environmental samples. Thus, even in a complex ecosystem, when plasticizers are degraded, the breakdown is not complete and significant amounts of 2-ethylhexanoic acid and 2-ethylhexanol are observed. These compounds have been shown to exhibit acute toxicity using Microtox, Daphnia, rainbow trout and fathead minnow toxicity assays. Since it is already well established that plasticizers are ubiquitous in the environment, it is expected that their recalcitrant metabolites will also be ubiquitous. This is of concern because, while the plasticizers do not exhibit acute toxicity, their metabolites do.     

Preliminary toxicity assessment of water after treatment with UV-irradiation and UVC/H2O2

Photooxidation (UV radiation) and enhanced photooxidation (UVC/H2O2) are water treatment technologies which remove aquatic natural organic matter (NOM) by photodegradation, producing lower molecular weight components and CO2. Since these technologies are being investigated for the treatment of drinking water, knowledge of the potential toxicity of the photooxidation by-products is vital. The potential toxicity of UVA-, UVB-, UVC-irradiated, and UVC/H2O2-treated aquatic NOM in two spot samples from two Australian reservoirs was analysed in two spot samples using Vibriofischeri in the Microtox test, African green monkey kidney cells (AS/NZS 4020:1999), and Daphnia carinata in an acute immobilisation test. Toxicity was not apparent for both the Microtox procedure and cytotoxicity analyses for the UVC-irradiated and UVC/H2O2-treated NOM samples, while UVA- and UVB-irradiated water samples were non-toxic to D. carinata. In contrast, acute toxicity was observed for UVC- and UVC/H2O2-treated water samples. The observed toxicity was attributed to photooxidative degradation of NOM-metal binding sites, which resulted in the release of bioavailable copper ions, as evidenced by higher concentrations of free copper ions in photooxidised water. As the total copper concentrations of the two raw water samples were well below the Australian Water Quality Guidelines for metals in domestic supplies, the release of copper from photooxidised NOM is unlikely to cause health concerns in these samples.     

Bioaccumulation and toxicity of copper as affected by interactions between humic acid and water hardness

This study evaluated the effects of water hardness and humic acid (HA) on the acute and chronic toxicity of copper to Daphnia pulex and on its accumulation by D. magna. Hardness had little effect on either the acute (3-day) or the chronic (42-day) toxicity of copper. Humic acid significantly reduced both the acute and chronic toxicity of copper when added to waters having hardnesses of 58, 115 and 230 mg l^?1 as CaCO₃. The effect, per unit of HA, on chronic toxicity was very similar for soft and medium water but less in hard water. At each of two HA concentrations, copper was chronically more toxic in hard water than in either medium or soft water. Bioaccumulation of copper varied with relative hardness and HA concentration and this was further affected by age at exposure. For 1-day-old animals, an increase in either hardness or HA- or any combination of the two, tended to decrease bioaccumulation. Results for 7-day-old animals were in general agreement except for animals exposed to copper in hard water at an intermediate HA concentration. These animals accumulated significantly more copper in the presence of HA. This agrees with the fact that this concentration of HA also increased the chronic toxicity of copper in hard water. Both of those phenomena are probably due to the displacement of Cu²⁺ from HA by competition from the increased concentrations of Ca²⁺ and Mg²⁺. The fact that HA had the opposite effect on copper accumulation by young animals in hard water could not be explained.     

Phenolic removal in a model olive oil mill wastewater using Pleurotus ostreatus in bioreactor cultures and biological evaluation of the process

Pleurotus ostreatus grown in bioreactor batch cultures in a model phenolic wastewater (diluted and sterilized olive oil mill wastewater-OMW), caused significant phenolic removal. Laccase, the sole ligninolytic enzyme detected in the growth environment, was produced during primary metabolic growth. The bioprocess was simulated with the aid of a mathematical model and the parameters of growth were determined. When the fungal biomass was increased in the reactor (during repeated batch experiments) the rate of reducing sugars consumption progressively increased, but a phenolic fraction seemed of being strongly resistant to oxidation. The toxicity of OMW against the seeds of Lepidium sativum and the marine Branchiopoda Artemia sp. was significantly decreased after biotreatment. On the contrary, the toxicity against the freshwater Branchiopoda Daphnia magna was not affected by the treatment, whereas on the soil and freshwater sediments Ostracoda Heterocypris incongruens was slightly decreased. Both treated and untreated OMWs, used as water for irrigation of lettuce and tomato plants, did not significantly affect the uptake of several nutrients by the cultivated plants, but resulted in a decrease in the plant yields, which was minimized when high OMW dilutions were used. As a conclusion, P. ostreatus is able to reduce phenolic content and toxicity of sterilized OMW, in bioreactor cultures. However, high OMW dilutions should be used, and/or additional treatment should be applied before use of the OMW in the environment, e.g. as water for irrigation. Further research should be done in order to transfer this technology under industrial conditions (e.g. by using unsterilized OMW).     

The impact of increased oxygen conditions on metal-contaminated sediments part II: effects on metal accumulation and toxicity in aquatic invertebrates

The present study evaluated the effect of increasing oxygen concentrations in overlying surface water on the accumulation and toxicity of sediment-bound metals in the aquatic invertebrates Lumbriculus variegatus, Asellus aquaticus and Daphnia magna. A 54 days experiment using three experimental treatments (90% O₂ in overlying surface water, 40% O₂ and a non-polluted control) was conducted. At 6 different time points (after 0, 2, 5, 12, 32 and 54 days) acid volatile sulfides (AVS), simultaneously extracted metals (SEM) and total organic carbon (TOC) were measured in the superficial sediment layer (0-1 cm). At each time point, accumulated metal levels as well as the available energy stores were measured in L. variegatus and A. aquaticus and each time D. magna was exposed to surface water in a 24 h toxicity test. Additionally metallothionein-like protein (MTLP) induction was quantified in L. variegatus. Oxygen induced changes in sediment AVS resulted in faster accumulation of metals from contaminated sediments in A. aquaticus, while no differences in toxicity in this species were observed. Ag, Cr, As and Co accumulation as well as toxicity in water exposed D. magna were clearly enhanced after 54 days, caused by oxidation of metal-sulfide complexes. Due to their feeding and burrowing behaviour, metal accumulation and toxicity in L. variegatus was not influenced by geochemical characteristics. Nevertheless, a rapid induction of MTLP was observed in both the 90% O₂ and the 40% O₂ treatment. The present study showed that elevated oxygen concentrations in overlying surface water can directly enhance metal accumulation and toxicity in aquatic invertebrates, however this is highly dependent on the organisms ecology and most dominant metal exposure route (water vs. sediment).     

Acute toxicity removal in textile finishing wastewater by Fenton's oxidation, ozone and coagulation-flocculation processes

This study evaluates the effectiveness of Fenton's oxidation (FO) process and ozone (O3) oxidation compared with a coagulation-flocculation (CF) process to remove effluent toxicity as well as colour and COD from a textile industry wastewater. Daphnia magna was used to test acute toxicity in raw and pre-treated wastewater. The operational parameters for each process were determined on the basis of complete toxicity removal. The FO process removed COD at a higher rate (59%) than O3 (33%) while colour removal was similar (89% and 91%, respectively). The CF process removed both COD and colour at rates similar to the FO process. A colour range of 150-250 platin-cobalt (Pt-Co) unit was assessed for toxicity.     

Toxicity to Daphnia magna and Vibrio fischeri of Kraft bleach plant effluents treated by catalytic wet-air oxidation

Two Kraft-pulp bleaching effluents from a sequence of treatments which include chlorine dioxide and caustic soda were treated by catalytic wet-air oxidation (CWAO) at T=463 K in trickle-bed and batch-recycle reactors packed with either TiO2 extrudates or Ru(3 wt%)/TiO2 catalyst. Chemical analyses (TOC removal, color, HPLC) and bioassays (48-h and 30-min acute toxicity tests using Daphnia magna and Vibrio fischeri, respectively) were used to get information about the toxicity impact of the starting effluents and of the treated solutions. Under the operating conditions, complex organic compounds are mostly oxidized into carbon dioxide and water, along with short-chain carboxylic acids. Bioassays were found as a complement to chemical analyses for ensuring the toxicological impact on the ecosystem. In spite of a large decrease of TOC, the solutions of end products were all more toxic to Daphnia magna than the starting effluents by factors ranging from 2 to 33. This observation is attributed to the synergistic effects of acetic acid and salts present in the solutions. On the other hand, toxicity reduction with respect to Vibrio fischeri was achieved: detoxification factors greater than unity were measured for end-product solutions treated in the presence of the Ru(3 wt%)/TiO2 catalyst, suggesting the absence of cumulative effect for this bacteria, or a lower sensitivity to the organic acids and salts. Bleach plant effluents treated by the CWAO process over the Ru/TiO2 catalyst were completely biodegradable.     

PCB pollution behaviour in the River Seine

The contamination of the River Seine (France) and its main tributaries (Yonne, Marne, Oise) have been studied, under different hydrological conditions, at the end of spring before the low watermark and at the beginning of autumn after the first swelling of flow.The sector under study consists of the Seine basin, centered on the Paris area; the variability of PCB concentration in water, apart from flow dependence, shows that important lateral discharges are involved. The pollution level is particularly noticeable at Paris and downstream from Paris and the median concentration in sediments reaches 3800 ng l⁻¹ (ppb). Data on particulate organic carbon and various grain size fractions show the PCB to be preferentially adsorbed on organic-rich sedimentary particles.Partition coefficients between particulate matter and liquid phase have been computed and show that the liquid phase has the main role in micropollutant transport.