Susceptibility of epigeic earthworm Eisenia fetida to agricultural application of six insecticides

Ecotoxicological risks of agricultural application of six insecticides to soil organisms were evaluated by acute toxicity tests under laboratory condition following OECD guidelines using the epigeic earthworm Eisenia fetida as the test organism. The organochlorine insecticide endosulfan (LC₅₀ - 0.002 mg kg⁻¹) and the carbamate insecticides aldicarb (LC₅₀ - 9.42 mg kg⁻¹) and carbaryl (LC₅₀ - 14.81 mg kg⁻¹) were found ecologically most dangerous because LC₅₀ values of these insecticides were lower than the respective recommended agricultural dose (RAD). Although E. fetida was found highly susceptible to the pyrethroid insecticide cypermethrin (LC₅₀ - 0.054 mg kg⁻¹), the value was higher than its RAD. The organophosphate insecticides chlorpyrifos (LC₅₀ - 28.58 mg kg⁻¹), and monocrotophos (LC₅₀ - 39.75 mg kg⁻¹) were found less toxic and ecologically safe because the LC₅₀ values were much higher than their respective RAD.     

C60 fullerene: a powerful antioxidant or a damaging agent? The importance of an in-depth material characterization prior to toxicity assays

Since the discovery of fullerenes in 1985, these carbon nanospheres have attracted attention regarding their physico/chemical properties. Despite little knowledge about their impact on the environment and human health, the production of fullerenes has already reached an industrial scale. However, the toxicity of C₆₀ is still controversially discussed.The aim of this study was to clarify the biological effects of tetrahydrofuran (THF) suspended C₆₀ fullerene in comparison to water stirred C₆₀ fullerene suspensions. Beyond that, we analyzed the effects on the Crustacea Daphnia magna an indicator for ecotoxicological effects and the human lung epithelial cell line A549 as a simplified model for the respiratory tract.We could demonstrate that water-soluble side products which were formed in THF nC₆₀ suspension were responsible for the observed acute toxic effects, whereas fullerenes themselves had no negative effect regardless of the preparative route on either A549 cell in vitro or D. magna in vivo.     

Nano-TiO2 enhances the toxicity of copper in natural water to Daphnia magna

The acute toxicity of engineered nanoparticles (NPs) in aquatic environments at high concentrations has been well-established. This study demonstrates that, at a concentration generally considered to be safe in the environment, nano-TiO₂ remarkably enhanced the toxicity of copper to Daphnia magna by increasing the copper bioaccumulation. Specifically, at 2 mg L⁻¹ nano-TiO₂, the (LC₅₀) of Cu²⁺ concentration observed to kill half the population, decreased from 111 μg L⁻¹ to 42 μg L⁻¹. Correspondingly, the level of metallothionein decreased from 135 μg g⁻¹ wet weight to 99 μg g⁻¹ wet weight at a Cu²⁺ level of 100 μg L⁻¹. The copper was found to be adsorbed onto the nano-TiO₂, and ingested and accumulated in the animals, thereby causing toxic injury. The nano-TiO₂ may compete for free copper ions with sulfhydryl groups, causing the inhibition of the detoxification by metallothioneins.     

Effects of carboxylic acids on nC60 aggregate formation

The discovery that negatively charged aggregates of C₆₀ fullerene (nC₆₀) are stable in water has raised concerns regarding the potential environmental and health effects of these aggregates. In this work, we show that nC₆₀ aggregates produced by extended mixing in the presence of environmentally relevant carboxylic acids (acetic acid, tartaric acid, citric acid) have surface charge and morphologic properties that differ from those produced by extended mixing in water alone. In general, aggregates formed in the presence of these acids have a more negative surface charge and are more homogeneous than those produced in water alone. Carboxylic acid identity, solution pH, and sodium ion concentration, which are all intricately coupled, play an important role in setting the measured surface charge. Comparisons between particle sizes determined by analysis of TEM images and those obtained by dynamic light scattering (DLS) indicate that DLS results require careful evaluation when used to describe nC₆₀ aggregates.     

Inactivation and injury assessment of Escherichia coli during solar and photocatalytic disinfection in LDPE bags

Solar disinfection (SODIS) of Escherichia coli suspensions in low-density polyethylene bag reactors was investigated as a low-cost disinfection method suitable for application in developing countries. The efficiency of a range of SODIS reactor configurations was examined (single skin (SS), double skin, black-backed single skin, silver-backed single skin (SBSS) and composite-backed single skin) using E. coli suspended in model and real surface water. Titanium dioxide was added to the reactors to improve the efficiency of the SODIS process. The effect of turbidity was also assessed. In addition to viable counts, E. coli injury was characterised through spread-plate analysis using selective and non-selective media. The optimal reactor configuration was determined to be the SBSS bag (t₅₀ = 9.0 min) demonstrating the importance of UVA photons, as opposed to infrared in the SODIS disinfection mechanism. Complete inactivation (6.5-log) was achieved in the presence of turbidity (50 NTU) using the SBSS bag within 180 min simulated solar exposure. The addition of titanium dioxide (0.025 g L⁻¹) significantly enhanced E. coli inactivation in the SS reactor, with 6-log inactivation observed within 90 min simulated solar exposure. During the early stages of both SODIS and photocatalytic disinfection, injured E. coli were detected; however, irreversible injury was caused and re-growth was not observed. Experiments under solar conditions were undertaken with total inactivation (6.5-log) observed in the SS reactor within 240 min, incomplete inactivation (4-log) was observed in SODIS bottles exposed to the same solar conditions.     

Photocatalytic removal of organic pollutants in aqueous solution by Bi(4)Nb(x)Ta((1-x))O(8)I

In this work, Bi₄Nb_xTa_(1−x)O₈I photocatalysts have been synthesized by solid state reaction method and characterized by powder X-ray diffraction, scanning electron microscope and UV-Vis near infrared diffuse reflectance spectroscopy. The photocatalytic activity of these photocatalysts was evaluated by the degradation of methyl orange (MO) in aqueous solutions under visible light, UV light and solar irradiation. The effects of catalyst dosage, initial pH and MO concentration on the removal efficiency were studied, and the photocatalytic reaction kinetics of MO degradation as well. The results indicated that Bi₄Nb_xTa_(1−x)O₈I exhibited high photocatalytic activity for the removal of MO in aqueous solutions. For example, the removal efficiency of MO by Bi₄Nb_0.1Ta_0.9O₈I was as high as 92% within 12 h visible light irradiation under the optimal conditions: initial MO concentration of 5-10 mg L⁻¹, catalyst dosage of 6 g L⁻¹ and natural pH (6-8), the MO molecules could be completely degradated by Bi₄Nb_0.1Ta_0.9O₈I within 40 min under UV light irradiation, and the photodegradation efficiency reaches to 60% after 7 h solar irradiation. Furthermore, the photocatalytic degradation of Bisphenol A (BPA) was also investigated under visible light irradiation. It is found that 99% BPA could be mineralized by Bi₄Nb_0.1Ta_0.9O₈I after 16 h visible light irradiation. Through HPLC/MS, BOD, TOC, UV-Vis measurements, we determined possible degradation products of MO and BPA. The results indicated that MO was degradated into products which are easier to be biodegradable and innocuous treated, and BPA could be mineralized completely. Furthermore, the possibility for the photosensitization effect in the degradation process of MO under visible light irradiation has been excluded.     

Atmospheric transport of urban-derived NH(x): Evidence from nitrogen concentration and delta(15)N in epilithic mosses at Guiyang, SW China

Nitrogen concentration and δ¹⁵N in 175 epilithic moss samples were investigated along four directions from urban to rural sites in Guiyang, SW China. The spatial variations of moss N concentration and δ¹⁵N revealed that atmospheric N deposition is dominated by NH_x-N from two major sources (urban sewage NH₃ and agricultural NH₃), the deposition of urban-derived NH_x followed a point source pattern characterized by an exponential decline with distance from the urban center, while the agricultural-derived NH_x was shown to be a non-point source. The relationship between moss N concentration and distance (y = 1.5e^−0.13x + 1.26) indicated that the maximum transporting distance of urban-derived NH_x averaged 41 km from the urban center, and it could be determined from the relationship between moss δ¹⁵N and distance [y = 2.54 ln(x) − 12.227] that urban-derived NH_x was proportionally lower than agricultural-derived NH_x in N deposition at sites beyond 17.2 km from the urban center. Consequently, the variation of urban-derived NH_x with distance from the urban center could be modeled as y = 56.272e^−0.116x − 0.481 in the Guiyang area.     

Molecular and physiological characterization of fluoroquinolone resistance in relation to uropathogenicity among Escherichia coli isolates isolated from Wenyu River, China

Increasing antibacterial resistance and pathogenicity in the environment is of growing concern due to its potential human risk. In the present study, 236 Escherichia coli isolates were collected from Wenyu River in China on drugless (48 isolates) and quinolone-containing plates (189 isolates). Their minimum inhibitory concentrations (MICs) were determined ranging from 0.125 μg mL⁻¹ to 128 μg mL⁻¹. Mutation points related to fluoroquinolone resistance were observed at S83 to L and D87 to N or Y in the GyrA subunit and S80 to R or I and E84 to G in the ParC subunit. Generally, MICs of LEV and GAT are dependent on the patterns of these mutation points. The profile with three mutation points was related to LEV-resistant E. coli isolates, and the (S83L, D87N + S80I) mutation profile was most prevalent (65.7%) in LEV-resistant isolates, while a large proportion of isolates, even those with three mutation points, were susceptive to GAT. The incidence of virulence factors in LEV-resistant isolates (44.7%, 59/132) was much higher than in nonresistant isolates (23.1%, 24/104) (χ² = 11.925, 1° of freedom, p < 0.001) indicating that fluoroquinolone-resistant E. coli would pose a potential risk. A similar distribution was also found in isolates resistant to GAT (χ² = 7.843, 1° of freedom, p = 0.0079).     

Cellular uptake and mutagenic potential of metal oxide nanoparticles in bacterial cells

Extensive production and consumption of nanomaterials such as ZnO and TiO₂ has increased their release and disposal into the environment. The accumulation of nanoparticles (NPs) in ecosystem is likely to pose threat to non-specific targets such as bacteria. The present study explored the effect of ZnO and TiO₂ NPs in a model bacterium, Salmonella typhimurium. The uptake of ZnO and TiO₂ bare NPs in nano range without agglomeration was observed in S. typhimurium. TEM analysis demonstrated the internalization and uniform distribution of NPs inside the cells. Flow cytometry data also demonstrates that both ZnO and TiO₂ NPs were significantly internalized in the S. typhimurium cells in a concentration dependent manner. A significant increase in uptake was observed in the S. typhimurium treated even with 8 and 80 ng mL⁻¹ of ZnO and TiO₂ NPs with S9 after 60 min, possibly the formation of micelles or protein coat facilitated entry of NPs. These NPs exhibited weak mutagenic potential in S. typhimurium strains TA98, TA1537 and Escherichia coli (WP2uvrA) of Ames test underscoring the possible carcinogenic potential similar to certain mutagenic chemicals. Our study reiterates the need for re-evaluating environmental toxicity of ZnO and TiO₂ NPs presumably considered safe in environment.     

Polychlorinated dibenzo-p-dioxin and dibenzofuran in urban air of an Andean city

Particle-bound polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in ambient air were monitored together with particulate matter less than 10 μm (PM₁₀) at three sampling sites of the Andean city of Manizales, Colombia; during September 2009 and July 2010. PCDD/Fs ambient air emissions ranged from 1 fg WHO-TEQ m⁻³ to 52 fg WHO-TEQ m⁻³ in particulate fraction. The PM₁₀ concentrations ranged from 23 μg m⁻³ to 54 μg m⁻³. Concentrations of PM₁₀ and PCDD/Fs in ambient air observed for Manizales - a medium sized city with a population of 380 000 - were comparable to concentrations in larger cities. The highest concentrations of PCDD/Fs and PM₁₀ found in this study were determined at the central zone of the city, characterized by public transportation density, where diesel as principal fuel is used. In addition, hypothetical gas fractions of PCDD/Fs were calculated from theoretical K_p data. Congener profiles of PCDD/Fs exhibited ratios associated with different combustion sources at the different sampling locations, ranging from steel recycling to gasoline and diesel engines. Taking into account particle and gas hypothetical fraction of PCDD/Fs, Manizales exhibited values of PCDD/Fs equivalent to rural and urban-industrial sites in the southeast and center of the city respectively. Poor correlation of PCDDs with PM₁₀ (r = −0.55 and r = 0.52) suggests ambient air PCDDs were derived from various combustion sources. Stronger correlation was observed of PCDFs with PM₁₀. Poor correlation between precipitation and reduced PM₁₀ concentration in ambient air (r = −0.45) suggested low PM₁₀ removal by rainfall.     

Partitioning behaviour of perfluorinated alkyl contaminants between water, sediment and fish in the Orge River (nearby Paris, France)

This paper reports on the partitioning behaviour of 15 perfluorinated compounds (PFCs), including C₄-C₁₀ sulfonates and C₅-C₁₄ carboxylic acids, between water, sediment and fish (European chub, Leuciscus cephalus) in the Orge River (nearby Paris). Total PFC levels were 73.0 ± 3.0 ng L⁻¹ in water and 8.4 ± 0.5 ng g⁻¹ in sediment. They were in the range 43.1-4997.2 ng g⁻¹ in fish, in which PFC tissue distribution followed the order plasma > liver > gills > gonads > muscle. Sediment-water distribution coefficients (log K_d) and bioaccumulation factors (log BAF) were in the range 0.8-4.3 and 0.9-6.7, respectively. Both distribution coefficients positively correlated with perfluoroalkyl chain length. Field-based biota-sediment accumulation factors (BSAFs) are also reported, for the first time for PFCs other than perfluorooctane sulfonate. log BSAF ranged between −1.3 and 1.5 and was negatively correlated with the perfluoroalkyl chain length in the case of carboxylic acids.     

Bioaccumulation and depuration of anthracene in Penaeus monodon (Fibricius) through food ingestion

Understanding on the bioaccumulation and depuration of PAHs (polycyclic aromatic hydrocarbons) in Penaeus monodon is important in seafood safety because it is one of the most popular seafood consumed worldwide. In this study, we used anthracene as the precursor compound for PAHs accumulation and depuration in the shrimp. Commercial feed pellets spiked with anthracene were fed to P. monodon. At 20 mg kg⁻¹ anthracene, P. monodon accumulated 0.1% of the anthracene from the feed. P. monodon deputed the PAH two times faster than its accumulation. The shrimp reduced its feed consumption when anthracene content in the feed exceeded 20 mg kg⁻¹. At 100 mg kg⁻¹ anthracene, P. monodon started to have necrosis tissues on the posterior end of their thorax. The bioaccumulation factor (BAF), uptake rate constant (k₁) and depuration rate constant (k₂) of anthracene in P. monodon were 1.15 × 10⁻³, 6.80 × 10⁻⁴ d⁻¹ and 6.28 × 10⁻¹ d⁻¹, respectively. The depuration rate constant is about thousand times higher than the uptake rate constant and this indicated that this crustacean is efficient in depurating hydrocarbons from their tissue.     

Trophic transfer of pyrene metabolites and nonextractable fraction from Oligochaete (Lumbriculus variegatus) to juvenile brown trout (Salmo trutta)

Cell lines of Etroplus suratensis established in our laboratory were evaluated for their potential use as screening tools for the ecotoxicological assessment of tannery effluent. The cytotoxic effect of tannery effluent in three cell lines derived from eye, kidney and gill tissue of E. suratensis was assessed using multiple endpoints such as Neutral Red (NR) assay, Coomassie Blue (CB) protein assay and Alamar Blue (AB) assay. Acute toxicity tests on fish were conducted by exposing E. suratensis for 96 h to tannery effluent under static conditions. The toxic effect of tannery effluent on the survival of fish was found to be concentration and time dependent. The tannery effluent at the concentration of 15% caused 100% mortality at 96 h whereas the lower concentration (0.5%) caused 13.33% mortality. The cytotoxicity of tannery effluent was found to be similar in the three cell lines tested, independent of the toxic endpoints employed. EC₅₀ values, the effective concentration of tannery effluent resulting in 50% inhibition of cytotoxicity parameters after 48 h exposure to tannery effluent were calculated for eye, kidney and gill cell lines using NR uptake, AB and cell protein assays. Statistical analysis revealed good correlation with r² = 0.95-0.99 for all combinations between endpoints employed. Linear correlations between each in vitro EC₅₀ and the in vivo LC₅₀ data, were highly significant p < 0.001 with r² = 0.977, 0.968 and 0.906 for AB₅₀, NR₅₀, and CB₅₀, respectively.     

Cyp35a2 gene expression is involved in toxicity of fenitrothion in the soil nematode Caenorhabditis elegans

In this study, the effect of organophosphorous (OP) pesticide, fenitrothion (FT), on the non-target organism was investigated using the soil nematode, Caenorhabditis elegans. Toxicity was investigated on multiple biological levels, from organism to molecular levels, such as, immoblity, growth, fertility, development, acetyl cholinesterase (AChE) activity and stress-response gene expressions. FT may provoke serious consequences on the C. elegans population, as it induced significant developmental disturbance. As expected, FT exposure inhibits AChE activity of C. elegans. The increased expression of the cytochrome p450 family protein 35A2 (cyp35a2) gene was also observed in FT exposed worms. To experimentally demonstrate the relationships between organism-level effects and the cyp35a2 gene expression in FT-exposed C. elegans, the integration of the gene expression with biochemical-, and organism level endpoints were attempted using a C. eleganscyp35a2 RNA interference (RNAi) and cyp35a2 mutant (gk317). The 24 h-EC50s of C. elegans on FT exposure were in the order of cyp35a2 RNAi in cyp35a2 mutant (gk317) > cyp35a2 mutant (gk317) > cyp35a2 RNAi in wildtype (N2) > wildtype (N2). The higher EC50 values of cyp35a2 RNAi and cyp35a2 mutant (gk317) compared to that of wildtypeC. elegans strongly supported that cyp35a2 gene plays an important role in the toxicity of FT towards C. elegans. The experiments with cyp35a2 RNAi also indicated that the development disturbance and decreased AChE activity, which were observed in FT exposed wildtype C. elegans were significantly rescued in the cyp35a2 RNAi C. elegans. Overall results suggest that the cyp35a2 may be an important gene for exerting FT toxicity in C. elegans.     

Toxicity of nanoparticulate and bulk ZnO, Al2O3 and TiO2 to the nematode Caenorhabditis elegans

Limited information is available on the environmental behavior and associated potential risk of manufactured oxide nanoparticles (NPs). In this research, toxicity of nanoparticulate and bulk ZnO, Al₂O₃ and TiO₂ were examined to the nematode Caenorhabditis elegans with Escherichia coli as a food source. Parallel experiments with dissolved metal ions from NPs were also conducted. The 24-h median lethal concentration (LC₅₀) and sublethal endpoints were assessed. Both NPs and their bulk counterparts were toxic, inhibiting growth and especially the reproductive capability of the nematode. The 24-h LC₅₀ for ZnO NPs (2.3 mg L⁻¹) and bulk ZnO was not significantly different, but significantly different between Al₂O₃ NPs (82 mg L⁻¹) and bulk Al₂O₃ (153 mg L⁻¹), and between TiO₂ NPs (80 mg L⁻¹) and bulk TiO₂ (136 mg L⁻¹). Oxide solubility influenced the toxicity of ZnO and Al₂O₃ NPs, but nanoparticle-dependent toxicity was indeed observed for the investigated NPs.     

Effect of 3 years' free-air exposure to elevated ozone on mature Norway spruce (Picea abies (L.) Karst.) needle epicuticular wax physicochemical characteristics

We examined the effect of ozone (O₃) on Norway spruce (Picea abies) needle epicuticular wax over three seasons at the Kranzberg Ozone Fumigation Experiment. Exposure to 2× ambient O₃ ranged from 64.5 to 74.2 μl O₃ l⁻¹ h AOT40, and 117.1 to 123.2 nl O₃ l⁻¹ 4th highest daily maximum 8-h average O₃ concentration. The proportion of current-year needle surface covered by wax tubes, tube aggregates, and plates decreased (P = 0.011) under 2× O₃. Epistomatal chambers had increased deposits of amorphous wax. Proportion of secondary alcohols varied due to year (P = 0.004) and O₃ treatment (P = 0.029). Secondary alcohols were reduced by 9.1% under 2× O₃. Exposure to 2× O₃ increased (P = 0.037) proportions of fatty acids by 29%. Opposing trends in secondary alcohols and fatty acids indicate a direct action of O₃ on wax biosynthesis. These results demonstrate O₃-induced changes in biologically important needle surface characteristics of 50-year-old field-grown trees.     

Effects of endosulfan exposure and Taura Syndrome Virus infection on the survival and molting of the marine penaeid shrimp, Litopenaeus vannamei

Molting in crustaceans is an important endocrine-controlled biological process that plays a critical role in growth and reproduction. Many factors can affect this physiological cycle in crustaceans including environmental stressors and disease agents. For example the pathology of Taura Syndrome Virus (TSV) of shrimp is closely related to molting cycle. Similarly, endosulfan, a commonly used pesticide is a potential endocrine disruptor. This study explores interrelationships between pesticide exposure, virus infection and their interactions with physiology and susceptibility of the shrimp. Litopenaeus vannamei (Pacific white shrimp) were challenged with increasing doses of endosulfan and TSV (TSV-C, a Belize reference strain) to determine the respective median lethal concentrations (LC₅₀s). The 96-h endosulfan LC₅₀ was 5.32 μg L⁻¹, while the 7-d TSV LC₅₀ was 54.74 mg L⁻¹. Subsequently, based on their respective LC₅₀ values, a 20-d interaction experiment with sublethal concentrations of endosulfan (2 μg L⁻¹) and TSV (30 mg L⁻¹) confirmed a significant interaction (p < 0.05, χ² = 5.29), and thereby the susceptibility of the shrimp. Concurrently, molt-stage of animals, both at the time of exposure and death, was compared with mortality. For animals challenged with TSV, no strong correlation between molt-stage and mortality was observed (p > 0.05). For animals exposed to endosulfan, animals in the postmolt stage were shown to be more susceptible to acute toxicity (p < 0.05). For animals exposed to both TSV and endosulfan, interference of endosulfan-associated stress lead to increasingly higher susceptibility at postmolt (p < 0.05) during the acute phase of the TSV disease cycle.     

Toxicity and metabolism of copper pyrithione and its degradation product, 2,2'-dipyridyldisulfide in a marine polychaete

We conducted acute toxicity tests and sediment toxicity tests for copper pyrithione (CuPT) and a metal pyrithione degradation product, 2,2′-dipyridyldisulfide [(PS)₂], using a marine polychaete Perinereis nuntia. The acute toxicity tests yielded 14-d LC₅₀ concentrations for CuPT and (PS)₂ of 0.06 mg L⁻¹ and 7.9 mg L⁻¹, respectively. Sediment toxicity tests resulted in 14-d LC₅₀ concentrations for CuPT and (PS)₂ of 1.1 mg kg⁻¹ dry wt. and 14 mg kg⁻¹ dry wt., respectively. In addition to mortality, sediment avoidance behavior and decreases in animal growth rate were observed; growth rate was the most susceptible endpoint in the sediment toxicity tests of both toxicants. Thus, we propose lowest observed effect concentrations of 0.3 mg kg⁻¹ dry wt. and 0.2 mg kg⁻¹ dry wt. for CuPT and (PS)₂, respectively, and no observed effect concentrations of 0.1 mg kg⁻¹ dry wt. for both CuPT and (PS)₂. The difference in the toxicity values between CuPT and (PS)₂ observed in the acute toxicity test was greater than the difference in these values in the sediment toxicity test, and we attribute this to (PS)₂ being more hydrophilic than CuPT. In addition to the toxicity tests, we analyzed conjugation activity of several polychaete enzymes to the toxicants and marked activity of palmitoyl coenzyme-A:biocides acyltransferase and UDP-glucuronosyl transferase was observed.