DNA damage and biochemical toxicity of antibiotics in soil on the earthworm Eisenia fetida

DNA damage and changes in enzyme activities were used as biomarkers to evaluate the genotoxicity and oxidative stress of tetracycline and chlortetracycline on the earthworm Eisenia fetida. The results showed that both antibiotics induced significant genotoxicity on earthworms in a dose-dependent manner (p < 0.01) with chlortetracycline having a stronger effect than tetracycline in the short term. The tests on the activities of superoxide dismutase (SOD) and catalase (CAT) enzymes further indicated biochemical stresses induced by the antibiotics. An N-shaped activity pattern was noted with the enzyme activities being stimulated first, then inhibited, and stimulated again with increasing concentration. The induced activity of SOD or CAT could scavenge oxygen free radicals and protect the organisms against oxidative stress by alleviating the corresponding DNA damage. Compared to enzyme activities, DNA damage as a biomarker was more sensitive and is thus more suitable for detecting low concentration exposure and diagnosing the genotoxicity of contaminants in terrestrial environment.     

The impact of size on the fate and toxicity of nanoparticulate silver in aquatic systems

The increased use of silver nanomaterials presents a risk to aquatic systems due to the high toxicity of silver. The stability, dissolution rates and toxicity of citrate- and polyvinylpyrrolidone-coated silver nanoparticles (AgNPs) were investigated in synthetic freshwater and natural seawater media, with the effects of natural organic matter investigated in freshwater. When sterically stabilised by the large PVP molecules, AgNPs were more stable than when charge-stabilised using citrate, and were even relatively stable in seawater. In freshwater and seawater, citrate-coated AgNPs (Ag–Cit) had a faster rate of dissolution than PVP-coated AgNPs (Ag–PVP), while micron-sized silver exhibited the slowest dissolution rate. However, similar dissolved silver was measured for both AgNPs after 72 h in freshwater (500–600 μg L⁻¹) and seawater (1300–1500 μg L⁻¹), with higher concentrations in seawater attributed to chloride complexation. When determined on a mass basis, the 72-h IC50 (inhibitory concentration giving 50% reduction in algal growth rate) for Pseudokirchneriella subcapitata and Phaeodactylum tricornutum and the 48-h LC50 for Ceriodaphnia dubia exposure to Ag⁺ (1.1, 400 and 0.11 μg L⁻¹, respectively), Ag–Cit (3.0, 2380 and 0.15 μg L⁻¹, respectively) and Ag–PVP (19.5, 3690 and 2.0 μg L⁻¹, respectively) varied widely, with toxicity in the order Ag⁺ > Ag–Cit > Ag–PVP. Micron-sized silver treatments elicited much lower toxicity than ionic Ag⁺ or AgNP to P. subcapitata. However, when related to the dissolved silver released from the nanoparticles the toxicities were similar to ionic silver treatments. The presence of natural organic matter stabilised the particles and reduced toxicity in freshwater. These results indicate that dissolved silver was responsible for the toxicity and highlight the need to account for matrix components such as chloride and organic matter in natural waters that influence AgNP fate and mitigate toxicity.     

The impact of an industrial effluent on the water quality,submersed macrophytes and benthic macroinvertebrates in a dammed river of Central Spain

This research was conducted in the middle Duratón River (Central Spain), in the vicinity of Burgomillodo Reservoir. An industrial effluent enters the river 300 m downstream from the dam. Fluoride and turbidity levels significantly increased downstream from the effluent, these levels being to some extent affected by differential water releases from the dam. The community of submersed macrophytes exhibited slighter responses and, accordingly, lower discriminatory power than the community of benthic macroinvertebrates, this indicating that metrics and indices based on macroinvertebrates may be more suitable for the biological monitoring of water pollution and habitat degradation in dammed rivers receiving industrial effluents. However, in relation to fluoride bioaccumulation at the organism level, macrophytes (Fontinalis antipyretica and Potamogeton pectinatus) were as suitable bioindicators of fluoride pollution as macroinvertebrates (Ancylus fluviatilis and Pacifastacus leniusculus). Fluoride bioaccumulation in both hard and soft tissues of these aquatic organisms could be used as suitable bioindicator of fluoride pollution (even lower than 1 mg F⁻ L⁻¹) in freshwater ecosystems. Echinogammarus calvus exhibited a great sensitivity to the toxicity of fluoride ions, with a 96 h LC₅₀ of 7.5 mg F⁻ L⁻¹ and an estimated safe concentration of 0.56 mg F⁻ L⁻¹. The great capacity of E. calvus to take up and retain fluoride during exposures to fluoride ions would be a major cause of its great sensitivity to fluoride toxicity. It is concluded that the observed fluoride pollution might be partly responsible for the absence of this native amphipod downstream from the industrial effluent.     

Biosafety assessment of titanium dioxide nanoparticles in acutely exposed nematode Caenorhabditis elegans with mutations of genes required for oxidative stress or stress response

We used Caenorhabditis elegans to investigate whether acute exposure to TiO₂-NPs at the concentration of 20 μg L⁻¹ reflecting predicted environmental relevant concentration and 25 mg L⁻¹ reflecting concentration in food can cause toxicity on nematodes with mutations of susceptible genes. Among examined mutants associated with oxidative stress and stress response, we found that genes of sod-2, sod-3, mtl-2, and hsp-16.48 might be susceptible for TiO₂-NPs toxicity. Mutations of these genes altered functions of both possible primary and secondary targeted organs in nematodes exposed to 25 mg L⁻¹ of TiO₂-NPs for 24-h. Mutations of these genes caused similar expression patterns of genes required for oxidative stress in TiO₂-NPs exposed mutant nematodes, implying their similar mechanisms to form the susceptible property. Nevertheless, acute exposure to 20 μg L⁻¹ of TiO₂-NPs for 24-h and 25 mg L⁻¹ of TiO₂-NPs for 0.48-h or 5.71-h did not influence functions of both possible primary and secondary targeted organs in sod-2, sod-3, mtl-2, and hsp-16.48 mutants. Therefore, our results suggest the relatively safe property of acute exposure to TiO₂-NPs with certain durations at predicted environmental relevant concentrations or concentrations comparable to those in food in nematodes with mutations of some susceptible genes.     

Cytotoxic and genotoxic effects of metal(oid)s bioactivated in rocket leaves (Eruca vesicaria subsp. sativa Miller)

Rocket is an important source of essential elements. However, it may also accumulate toxic elements such as metal(oids). The objectives of the present work were (i) to study the uptake of arsenic, lead, cadmium and zinc in rocket grown in contaminated soils, (ii) to establish the genotoxic and cytotoxic activities of this vegetable material, and (iii) to study the modulator role of the glucosinolate and metal contents in the genotoxic/cytotoxic activities. Lead, cadmium and zinc leaf concentrations in our study were over the concentrations allowed by the statutory limit set for metal(oid) contents in vegetables. The accessions were non genotoxic at the different concentrations studied, although one of the accessions showed the highest mutation rates doubling those of negative control. The cytotoxicity assays with HL60 human leukaemia cells showed that the tumouricide activities of rocket leaves decreased with the increasing of metal(oid) concentrations and also with the decreasing of glucosinolate concentrations in their tissues. An interaction between metal(oid)s and glucosinolate degradation products contained in rocket leaves is suggested as the main modulator agents of the biological activity of the plants grown in metal-contaminated soils.     

Effects of sub-lethal glyphosate concentrations on growth and photosynthetic performance of non-target species Bolboschoenus maritimus

Glyphosate use has increased over the last decades for the control of invasive plant species in wetland ecosystems. Although glyphosate has been considered ‘environmentally’ safe, its repeated use could increase the toxicological risk derived from diffuse pollution of surface and groundwater on non-target vegetation. A glasshouse study was designed to determine the effect produced by the addition of different sub-lethal doses of glyphosate herbicides (5–30 mg L⁻¹) to the nutrient solution on the growth and photosynthetic apparatus of Bolboschoenus maritimus. Although B. maritimus plants were able to grow and survive after 20 d of exposure to glyphosate, the presence of this herbicide affected their growth, through a direct interaction with the root system. Particularly, at 30 mg L⁻¹ glyphosate, B. maritimus showed ca. 30% of biomass decrease. The reduction in B. maritimus growth was due to a decrease in net photosynthetic rate (A), which ranged between values ca. 11.5 and 5.5 μmol m⁻² s⁻¹ CO₂ for the control and the highest glyphosate treatment, respectively. The response of A to glyphosate could be largely accounted for by non-stomatal limitations, since stomatal conductance was similar in all glyphosate treatments. Thus, A decrease was prompted by the negative impact of herbicide on photochemical (PSII) apparatus, the reduction in the absorption of essential nutrients, the reduction of photosynthetic pigments and possibly the reduction in Rubisco carboxilation capacity. Moreover, glyphosate excess caused photoinhibitory damage. In conclusion, in this study we have shown that herbicide water pollution could be a source of indirect phytotoxicity for B. maritimus.     

Reduction of toxicity of antimicrobial compounds by degradation processes using activated sludge,gamma radiation,and UV

The occurrence and persistence of pharmacologically active compounds in the environment has been an increasingly important issue. The objectives of this study were to investigate the decomposition of aqueous antimicrobial compounds using activated sludge, γ-irradiation, and UV treatment, and to evaluate the toxicity towards green algae, Pseudokirchneriella subcapitata, before and after treatment. Tetracycline (TCN), lincomycin (LMC) and sulfamethazine (SMZ) were used as target compounds. Gamma (γ)-irradiation showed the highest removal efficiency for all target compounds, while UV and activated sludge treatment showed compound-dependent removal efficiencies. TCN and SMZ were well degraded by all three treatment methods. However, LMC showed extremely low removal efficiency for UV and activated sludge treatments. Overall, the algal toxicity after degradation processes was significantly decreased, and was closely correlated to removal efficiency. However, in the case of γ-irradiated TCN, UV and activated sludge treated LMC as well as sludge treated SMZ, the observed toxicity was higher than expected, which indicates the substantial generation of byproducts or transformed compounds of a greater toxicity in the treated sample. Consequently, γ-radiation treatment could be an effective method for removal of recalcitrant compounds such as antibiotics.     

Biodegradation kinetics and toxicity of vegetable oil triacylglycerols under aerobic conditions

The aerobic biodegradation of five triacylglycerols (TAGs), three liquids [triolein (OOO), trilinolein (LLL), and trilinolenin (LnLnLn)] and two solids [tripalmitin (PPP) and tristearin (SSS)] was studied in water. Respirometry tests were designed and conducted to determine the biochemical oxygen demand (BOD) parameters of the compounds. In the case of the solid lipids, the degradation process was limited by their extremely non-polar nature. When added to water, PPP and SSS formed irregular clumps or gumballs, not a fine and uniform suspension required for the lipase activity. After 30 days, appreciable mineralization was not achieved; therefore, first-order biodegradation coefficients could not be determined. The bioavailability of the liquid TAGs was restricted due to the presence of double bonds in the fatty acids (FAs). An autoxidation process occurred in the allylic chains, resulting in the production of hydroperoxides. These compounds polymerized and became non-biodegradable. Nevertheless, the non-oxidized fractions were readily mineralized, and BOD rate constants were estimated by non-linear regression: LLL (k = 0.0061 h⁻¹) and LnLnLn (k = 0.0071 h⁻¹) were degraded more rapidly than OOO (k = 0.0025 h⁻¹). Lipids strongly partitioned to the biomass and, therefore, Microtox^® toxicity was not observed in the water column. However, EC₅₀ values (<15% sample volume) were measured in the solid phase.     

Petroleum contaminated soil in Oman: Evaluation of bioremediation treatment and potential for reuse in hot asphalt mix concrete

This paper presents a study that aims at evaluating the leaching characteristics of petroleum contaminated soils as well as their application in hot mix asphalt concrete. Soil samples are environmentally characterized in terms of their total heavy metals and hydrocarbon compounds and leachability. The total petroleum hydrocarbon (TPH) present in the PCS before and after treatment was determined to be 6.8% and 5.3% by dry weight, indicating a reduction of 1% in the TPH of PCS due to the current treatment employed. Results of the total heavy metal analysis on soils indicate that the concentrations of heavy metals are lower when extraction of the soil samples is carried out using hexane in comparison to TCE. The results show that the clean soils present in the vicinity of contaminated sites contain heavy metals in the following decreasing order: nickel (Ni), followed by chromium (Cr), zinc (Zn), copper (Cu), lead (Pb), and vanadium (V). The current treatment practice employed for remediation of the contaminated soil reduces the concentrations of nickel and chromium, but increases the concentrations of all remaining heavy metals.