Impact of Long-Term Perfluorooctanoic Acid (PFOA) Exposure on Activated Sludge Process

Poly- and perfluorinated alkyl substances (PFASs) are groups of persistent toxic substances that have been commonly detected in wastewater treatment plants (WWTPs). In some cases, the activated sludge (AS) in WWTPs will encounter special wastewaters containing PFASs up to tens of milligram per liter (mg L^?1). However, under this condition, the potential impacts of PFASs on AS process remain unclear. In the present research, a lab-scale sequencing batch reactor was continuously exposed to perfluorooctanoic acid (PFOA), used as a representation for PFASs, at 20 mg L^?1 to mimic the extreme condition. The objective is to explore the impact of PFOA on AS process in terms of its wastewater treatment performance and evolution of microbial communities. The results indicate that PFOA restrained the microbial growth and affected the dissolved organic carbon removal. These negative impacts could be recovered after long-term adaptation. Besides, 20 mg L^?1 PFOA shows limited inhibition on nitrification and denitrification, suggesting a safe exposure level of PFOA for nitrogen removal. For microbial evolution, PFOA induced changes of communities during long-term exposure. The high abundance of Bacteroidetes, Proteobacteria, and Acidobacteria maintained over time reveals their tolerance towards PFOA. The occurrences of PFOA-resistant species are also observed. The present research provides new insight into the possible impacts of typical PFAS at high concentrations on AS process.     

Manganese (II) Removal from Aqueous Solutions by <Emphasis Type="Italic">Bacillus cereus</Emphasis>: an Optimization Study Using Experimental Design and Response Surface Methodology

The present study was carried out in order to investigate the removal of soluble Mn²⁺ from an aqueous solution using Bacillus cereus. A manganese aqueous solution at 50 mg L^?1 was treated, and the product was less than 1 mg L^?1 of residual concentration, which complied with environmental regulations. Before the optimization, B. cereus was able to remove Mn²⁺ ions from an aqueous solution; however, the residual content was around 2.5 mg L^?1. Screening experiments aiming at defining the effects of the growth medium composition indicated that both casamino acid-peptone and yeast extract contributed to manganese removal. These experiments also showed the interaction between these two components of the culture media, nevertheless the use of glucose did not prove significant. Considering these observations, the Doehlert design was used to generate a response surface. The model was significant with the p value lower than 0.05 and the lack-of-fit not significant (p > 0.05). The optimized composition of the growth medium was defined as 0.5 g L^?1 of casamino acid-peptone and 0.25 g L^?1 of yeast extract, whereas glucose could be removed from the original growth medium. When the optimized condition of the growth medium was used, the time required for manganese removal was reduced from 21 to 8 days. After optimization, B. cereus was capable of producing high manganese removal, reducing the residual concentration to levels below 1.0 mg L^?1.     

Humic acid and biochar as specific sorbents of pesticides

Purpose

The aim of the research was to compare the effect of two types of organic sorbents—humic acid (HA) and biochar (BC)—in sorption-desorption processes of different polar pesticides, which residues are commonly present in arable soils and are potentially harmful for the environment. It also aims to advance the understanding of behavior of both ionizable and nonionizable pesticides in the presence of BC and HA in soils.

Materials and methods

Three different classes of pesticides were investigated: carbamates (carbaryl and carbofuran), phenoxyacetic acids (2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA)), and aniline derivatives (metolachlor). Investigated humic acid was extracted by Shnitzer’s method from topsoil horizon of arable Gleyic Phaeozem. Biochar was produced from wheat straw in gasification process at 550 °C, remaining 30 s in the reactor. To obtain the experimental goal structural properties of both sorbents were determined and sorption-desorption experiments conducted. To the investigated organic matter samples (HA or BC), 10 or 15 mg L^?1 pesticide solutions in 10 mM CaCl₂ were added and the mixtures were shaken for 24 h. Afterwards, the samples were centrifuged and supernatants analyzed by LC-MS/MS for the pesticide content. Analogous experiment was performed for desorption studies (samples refilled with 10 mM CaCl₂).

Results and discussion

Humic acids exhibited strong affinity for the ionic substances, for which high-percentage uptake (74.6 and 67.9% initial dose of 2,4-D and MCPA, respectively) was obtained. Retention of nonionic carbamates on HA was much weaker (35.4% of carbofuran and 10.2% of carbaryl sorbed). Sorption of carbamates to BC was significantly reduced (76.4–84.3%) by the alkaline hydrolysis. Metolachlor was bound comparably strong both by HA (72.9%) and BC (70.2%), although different mechanisms governed its sorption. Noticeable desorption occurred only in the case of 2,4-D bound to HA (over 50%), whereas other studied compounds were released from HA within the range of 4.4–10.8% of the dose sorbed. Oppositely to HA, desorption of all studied pesticides from BC was completely inhibited, except for 2,4-D (3.7% desorbed).

Conclusions

Investigated humic acid has high affinity to polar, ionic pesticides of high water solubility, which are sorbed via specific interactions with HA functional groups. Studied biochar, due to its moderately hydrophobic character, preferentially attracts nonionic pesticides of relatively high logP values and low water solubility. Hydrophobic bonding is postulated as a main mechanism of their attraction to BC. Besides sorbent structural properties, pH is the main factor governing sorption equilibria in the studied mixtures.

     

Biodegradability of Disinfectants in Surface Waters from Buenos Aires: Isolation of an Indigenous Strain Able to Degrade and Detoxify Benzalkonium Chloride

Biodegradability of chlorhexidine (CH), triclosan (TC), and benzalkonium chloride (CBA) has been tested in 18 surface water sampling points in the urban area of Buenos Aires. Sampling points were located in both the Reconquista and the Matanza-Riachuelo basins as well as in the La Plata River. High tolerance to the three disinfectants was found and indigenous strains capable of degrading CBA and TC were isolated. Neither tolerance nor biodegradation were correlated with sewage pollution. A strain that degrades CBA was identified as belonging to the genus Pseudomonas using the API20NE system and 16SRNA sequencing. In batch assays, the strain was capable of degrading 100, 200, and up to 500 mg L^?1 of CBA in 10, 25, and 46 h respectively with specific growth rates (μ) of 0.56, 0.30, and 0.14 h^?1. The efficiency of the process was between 99.5–98.0% in terms of compound removal and between 93.8–89.1% in terms of chemical oxygen demand (COD). The detoxification of the compound as a result of the biodegradation was assessed using Pseudokirchneriella subcapitata, Vibrio fischeri, and Lactuca sativa as test organisms.     

Accumulation of Cadmium and Antioxidant and Hormonal Responses in the Indian Major Carp <Emphasis Type="Italic">Cirrhinus mrigala</Emphasis> During Acute and Sublethal Exposure

Acute (24 h) and sublethal (35 days) effects of cadmium chloride (CdCl₂) were examined in Cirrhinus mrigala using various endpoints (accumulation pattern, thyroid hormones (THs), and antioxidants). The mean concentrations of CdCl₂ for 24 and 96 h were found to be 35.974 and 22.387 mg L^?l, respectively. LC50 concentration of CdCl₂ for 24 h (35.97 mg L^?l) was used for the acute study. For the sublethal studies, fish were exposed to 3.59 mg L^?1 (Treatment I) and 7.19 mg L^?1 (Treatment II) corresponding to 1/10th and 1/5th of 24 h LC50 of the CdCl₂. During acute exposure, higher accumulation of CdCl₂ was noticed in the gill, liver, and kidney of C. mrigala, which is found in the order gill > liver > kidney tissues. Similarly, in sublethal treatments (Treatment I and II), a concentration and time-dependent increase of CdCl₂ accumulation was noticed in the order of gill > liver > kidney. GSH, GST, and GPx activities were found to be relatively lower from the treated groups in both acute and sublethal treatments. However, LPO activity was significantly increased in CdCl₂-treated fish C. mrigala. Further, plasma T₃ reduction was more pronounced than T₄ in acute study. During sublethal treatments, both T₄ and T₃ levels showed a continuous decrease as the exposure period extended. All the values in this study were statically significant (P < 0.01 and P < 0.05).     

Enhanced dissipation of DEHP in soil and simultaneously reduced bioaccumulation of DEHP in vegetable using bioaugmentation with exogenous bacteria

The widely used plastic film containing di(2-ethylhexyl) phthalate (DEHP) in agriculture has caused serious soil pollution and poses risks to human health through the food chain. An effective DEHP degradation bacteria, Microbacterium sp. J-1, was newly isolated from landfill soil. Response surface methodology was successfully employed for optimization resulting in 96% degradation of DEHP (200 mg L^?1) within 5 days. This strain degraded DEHP by hydrolysis of the ester bond and hydroxylation of the aromatic ring to form 2-ethyl hexanol, mono-(2-ethylhexyl) phthalate, phthalate acid, and protocatechuic acid, and subsequently transformed these compounds with a maximum specific degradation rate (q _max), half-saturation constant (K _s ), and inhibition constant (K _i ) of 1.46 day^?1, 180.2 mg L^?1, and 332.8 mg L^?1, respectively. Bioaugmentation of DEHP-contaminated soils with the strain J-1 greatly enhanced the DEHP dissipation rate (~88%). Moreover, this strain could efficiently colonize the rhizosphere soil of inoculated vegetables and further enhanced DEHP degradation (~97%), leading to a significant decrease (>70%) in DEHP accumulation in shoots and roots of the inoculated vegetables compared to uninoculated vegetables. The results highlighted the roles of the inoculated exogenous bacteria in simultaneously bioremediating contaminated soils and reducing bioaccumulation of DEHP in the edible part of the vegetable for food safety.     

Photo-Assisted Degradation,Toxicological Assessment,and Modeling Using Artificial Neural Networks of Reactive Gray BF-2R Dye

This work investigates the degradation of Reactive Gray BF-2R dye (a blend of reactive yellow 145, reactive orange 122 and reactive black 5 dyes) using UV/H₂O₂, Fenton, and photo-Fenton-advanced oxidative processes, with artificial sunlight and UV-C radiations. The photo-Fenton process employing UV-C radiation was the most efficient under the conditions studied. The ideal conditions for the degradation of the dye, determined using a factorial design 2³ and a study of the concentration of hydrogen peroxide ([H₂O₂]), were [H₂O₂] equal to 40 mg L^?1, iron concentration [Fe] of 1 mg L^?1, and pH between 3 and 4. The Chan and Chu non-linear kinetic model predicted the kinetic data with a degradation of over 98% for color and 68% for aromatics after 60 min. The behavior of the chemical oxygen demand fitted the first-order kinetic model well, with a degradation of 64% after 60 min. The Multilayer Perceptron 7-11-2 artificial neural network model enabled to model the degradation process of the aromatics and accurately predict the experimental data. Toxicity tests indicated that the post-treatment samples were non-toxic for Escherichia coli bacteria, and Portulaca grandiflora and Basil sabory seeds. However, they inhibited the growth of Lactuca sativa seeds and Salmonella enteritidis bacteria. The photo-Fenton process with UV-C radiation degraded the dye studied efficiently and the degradation percentages were, on average, 7% and 5% higher for color than those observed when employing the Fenton and UV/H₂O₂ processes, respectively. With the aromatic, however, they were 84% and 62% higher, thus justifying the use of this process.     

Effects of TiO<Subscript>2</Subscript> Nanoparticles on the Neotropical Cladoceran <Emphasis Type="Italic">Ceriodaphnia silvestrii</Emphasis> by Waterborne and Dietary Routes

The impact of nanoparticles (NPs) in zooplankton is poorly studied, particularly when organisms are exposed through diet. Food, constituted mainly by unicellular algae, can act as an important route of contamination for zooplankton. Since unicellular algae have a high surface area in relation to their volume, NPs can interact with their cell membranes and walls, as well as with exopolysaccharides secreted by them. In the present research, we investigated both the acute effects of waterborne titanium dioxide nanoparticles (TiO₂ NPs), and its chronic effects via dietary exposure on the Neotropical freshwater zooplankton Ceriodaphnia silvestrii Daday, 1902 (Crustacea: Cladocera). The observed acute effects served as support for chronic tests, in which we investigated the effects of TiO₂ NPs on survival and life history parameters (body length, numbers of eggs, and neonates produced) of cladoceran adult females, using the freshwater cosmopolitan chlorophycean Raphidocelis subcapitata as source of contamination of TiO₂ NPs for zooplankton. R. subcapitata cells were exposed to concentrations of 0, 0.01, 1, and 10 mg L^?1 of TiO₂ NPs for 96 h, and then provided as food for females of C. silvestrii until the third brood was released. Significant toxic effects were observed in body length and total number of neonates and eggs produced by females of C. silvestrii at concentrations of 1 and 10 mg L^?1 of TiO₂ NPs. Survival was the most sensitive parameter when exposure was given via food. From the concentration of 0.01 mg L^?1 of TiO₂ NPs, there was a decrease in the survival of C. silvestrii females. The quantification of TiO₂ NPs in algae evidenced that they have retained NPs in their cells, being, therefore, an important route of exposure and toxicity of TiO₂ NPs to the studied microcrustacean.     

Evaluation of Mercury,Lead, Arsenic,and Cadmium in Some Species of Fish in the Atrato River Delta,Gulf of Urabá, Colombian Caribbean

The concentrations of mercury, lead, cadmium, and arsenic were evaluated in 96 samples, 12 by each one of the following eight fish species: snook (Centropomus undecimalis), crevalle jack (Caranx hippos), Serra Spanish mackerel (Scomberomorus brasiliensis), southern red snapper (Lutjanus purpureus), blue runner (Caranx crysos), Atlantic tarpon (Megalops atlanticus), ladyfish (Elops saurus), and Atlantic goliath grouper (Epinephelus itajara), which were collected during 1 year in the Atrato River Delta in the Gulf of Urabá, Colombian Caribbean. Three fish were caught from each of the following sites the community usually uses to catch them (known as fishing grounds): Bahía Candelaria, Bahía Marirrío, Bocas del Roto, and Bocas del Atrato. The quantification of metals was performed by microwave-induced plasma-optical emission spectrometry. The Pb concentration fluctuated from 0.672 to 3.110 mg kg^?1, surpassing the maximum permissible limit (MPL?=?0.3 mg kg^?1) for human consumption for all species. The Hg concentration ranged between < Limit of detection and 6.303 mg kg^?1, and in the crevalle jack and Atlantic tarpon, concentrations exceeded the MPL (0.5 mg kg^?1). The levels of Cd and As were not significant in the studied species and did not exceed the MPL (0.05 mg kg^?1).     

Organic Matter Effects on the Cr(VI) Removal Efficiency and Tolerance of <Emphasis Type="Italic">Typha domingensis</Emphasis>

The removal efficiency and tolerance of Typha domingensis to Cr(VI) in treatments with and without organic matter (OM) addition were evaluated in microcosm-scale wetlands. Studied Cr(VI) concentrations were 15 mg L^?1, 30 mg L^?1, and 100 mg L^?1, in treatments with and without OM addition, arranged in triplicate. Controls (without neither metal nor OM addition—without metal with OM addition) were disposed. Cr(VI) was removed efficiently from water in all treatments. OM addition enhanced significantly Cr(VI) and total Cr removals from water. In the treatments with OM addition, significantly higher Cr concentrations were found in sediment than the treatments without OM addition. Plants of the treatments without OM addition showed significantly higher Cr concentrations in tissues but lower biomass increase than the treatments with OM addition. The highest Cr concentrations in tissues were observed in submerged parts of leaves, followed by roots. According to SEM analysis, in the 100 mg L^?1 treatments, the highest Cr accumulation was observed in the epidermis of old leaves. Although Cr(VI) produced changes in root morphology, the OM addition favored the plant growth. In T. domingensis, root morphological plasticity is an important mechanism to improve metal tolerance and Cr uptake in wetland systems minimizing the environmental impact.     

Dominant Characteristics Between <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> and <Emphasis Type="Italic">Cyclotella</Emphasis> Sp. Accompanying Dilution Process in Eutrophic Lake

Although dilution of lake water has been used for improvement of water quality and algal blooms control, it has not necessarily succeeded to suppress the blooms. We hypothesized that the disappearance of algal blooms by dilution could be explained by flow regime, nutrient concentrations, and their interaction. This study investigated the effects of daily renewal rate (d), nitrogen (N) and phosphorus (P) concentration, and their interaction on the domination between Microcystis aeruginosa and Cyclotella sp. through a monoxenic culture experiment. The simulation model as functions of the N:P mass ratio and dilution rate (D) (calculated from d) was constructed, and the dominant characteristics of both species were predicted based on the model using parameters obtained in a monoculture experiment and our previous study. Results of monoxenic culture experiment revealed that M. aeruginosa dominated in all conditions (d = 5 or 15%; N = 1.0 or 2.5 or 5.0 mg-N L^?1; P = 0.1 or 0.5 mg-P L^?1) and the predicted cell densities were substantially correspondent to experimental data. Under various N:P ratios and D values, characteristics of domination for each species were predicted, indicating that Cyclotella sp. tended to be dominant under high P concentrations (P ≥ 0.36 mg-P L^?1) when the N:P ratio was less than 7.0, and M. aeruginosa could not form algal blooms at the N:P ratio ≤ 7.0 (N ≤ 0.7 mg-N L^?1). It was also suggested that the dilution rate leading to the Cyclotella sp. domination required 0.20 day^?1 or higher regardless of the N:P ratios.

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Graphical Abstract ? M. aeruginosa and Cyclotella sp. could be a superior competitor in nutrient-limited and nutrient-rich conditions, respectively. ? The simulation model in this study indicated that the predicted cell density and nutrient concentration were substantially correspondent to experimental data. ? The model predicted that Cyclotella sp. tended to be dominant at the P ≥ 0.36 mg-P L^?1 when the N:P ratio was less than 7.0, and M. aeruginosa could not form algal blooms at the N:P ratio ≤ 7.0 (N ≤ 0.7 mg-N L^?1).

     

Effect of Cadmium Stress on Growth and Electrical Impedance Spectroscopy Parameters of <Emphasis Type="Italic">Cotinus coggygria</Emphasis> Roots

The use of plants for ecological remediation is an important method of controlling heavy metals in polluted land. Cotinus coggygria is a landscape plant that is used extensively in landscaping and afforestation. In this study, the cadmium tolerance level of C. coggygria was evaluated using electrical impedance spectroscopy (EIS) to lay a theoretical foundation for broad applications of this species in Cd-polluted areas and provide theoretical support to broaden the application range of the EIS technique. Two-year-old potted seedlings of C. coggygria were placed in a greenhouse to analyse the changes in the growth, water content and EIS parameters of the roots following treatment with different Cd concentrations (50, 100, 200, 500, 1000 and 1500 mg kg^?1), and soil without added Cd was used as the control. The roots grew well following Cd treatments of 50 and 100 mg kg^?1. The Cd contents increased with the increase in Cd concentration in the soil. However, the lowest root Cd content was found at 4 months of treatment. The extracellular resistance r_e and the intracellular resistance r_i increased first overall and then decreased with the increasing Cd concentration, and both parameters increased with a longer treatment duration. The water content had a significant negative correlation with the Cd content (P?<?0.01) and the r_e (P?<?0.05). C. coggygria could tolerate a soil Cd concentration of 100 mg kg^?1. There was a turning point in the growth, water content and EIS parameters of the C. coggygria roots when the soil Cd concentration reached 200 mg kg^?1. The root water content and r_e could reflect the level of Cd tolerance in C. coggygria.     

Assessment of Surface Water Quality in the Big Sunflower River Watershed of Mississippi Delta Using Nonparametric Analysis

Assessment of surface water quality in the Mississippi Delta is essential to quantify the eutrophication of the Gulf of Mexico. This study estimated the characteristics and variations of surface water quality at three study sites in the Big Sunflower River Watershed (BSRW) within the Mississippi Delta using Kruskal-Wallis, Dunn, Mann-Kendall, and Pettitt tests. In general, contents of some water quality constituents such as nitrate-nitrogen (NO₃???N) and total phosphorus (TP) in the BSRW varied from site to site each year, whereas variations of other constituents such as pH and dissolved oxygen (DO) each year were basically not significant. The highest median concentrations were found in spring for NO₃???N and total nitrogen (TN); in summer for specific conductance (SC), Na, and Cl; and in winter for DO. Mann-Kendall trend analysis revealed that there was an increasing annual trend at Leland but a decreasing annual trend at Merigold for NO₃???N concentrations even though such changes were very small, whereas there was no annual trend for TP at any of the three study sites. Pettitt’s test further identified that the NO₃???N concentrations had an abrupt increase in February 2009 at the median value of 0.44 mg L^?1 in Leland and an abrupt decrease in June 2012 at the median value of 3.65 mg L^?1 in Merigold. A very good linear correlation existed between total dissolved solid (TDS) and magnesium (Mg) in the BSRW, which could be used to estimate TDS from Mg concentrations for this watershed when the data for TDS are absent.     

Pine Bark Amendment to Promote Sustainability in Cu-Polluted Acid Soils: Effects on <Emphasis Type="Italic">Lolium perenne</Emphasis> Growth and Cu Uptake

The establishment of a complementary grass cover on vineyard soils can promote sustainability of the affected environment. In this work, we used an acid vineyard soil with total Cu concentration 188 mg kg^?1 to study the influence of pine bark amendment on Lolium perenne growth and Cu uptake. The results indicate that the pine bark amendment did not cause a significant increase in the mass of the shoots of Lolium perenne, but favored the root biomass: 0.034 g for control and 0.061 g for soil samples amended with 48 g kg^?1 of pine bark. Moreover, the pine bark amendment decreased Cu concentration in both, shoots (50 mg kg^?1 for control soil and 29 mg kg^?1 for soil amended with 48 g kg^?1 pine bark) and roots (250 mg kg^?1 for control soil and 64 mg kg^?1 for soil amended with 48 g kg^?1 pine bark). The main factor responsible for these results was a significant decrease of the most mobile fractions of Cu in the soil. Those fractions were extracted using ammonium acetate, ammonium chloride, sodium salt of ethylene-diamine-tetraacetic acid (EDTA-Na), and diethylene-triamine-pentaacetic acid (DTPA).     

Study of Heavy Metal Accumulation and Residual Toxicity in Soil Saturated with Phosphate Processing Wastewater

The effects of phosphate processing wastewater (PPWW) on heavy metal accumulation in a Mediterranean soil (Tunisia, North Africa) were investigated. Moreover, the residual toxicities of PPWW-irrigated soils extracts were assessed. Results showed that heavy metal accumulation was significantly higher in PPWW-irrigated soil extracts than in control soil. The heavy metal accumulation increased over time in treated soil samples and their average values followed the following order: Iron (Fe 252.72 mg l^?1) > Zinc (Zn 152.95 mg l^?1) > Lead (Pb 128.35 mg l^?1) > Copper (Cu 116.82 mg l^?1) > Cadmium (Cd 58.03 mg l^?1). The residual microtoxicity and phytotoxicity of the various treated soil samples extracts were evaluated by monitoring the bioluminescence inhibition (BI %) of Vibrio ficheri and the measurement of the germination indexes (GI %) of Lepidium sativum and Medicago sativa seeds. The results showed an important increase of residual toxicities of PPWW-treated soil extracts over time.     

Low Concentrations of Glyphosate-Based Herbicide Affects the Development of <Emphasis Type="Italic">Chironomus xanthus</Emphasis>

Glyphosate is an herbicide commonly used worldwide for weed control and generally applied as part of a formulated product, such as Roundup. Contamination of surface water by glyphosate-based herbicides can cause deleterious effects in organisms, mainly in aquatic systems near to intensive agricultural areas (e.g., transgenic soybean crops). Given the lack of toxicological information concerning effects of glyphosate-based herbicides on tropical aquatic ecosystems, we aimed to evaluate the lethal and sub-lethal effects of Roundup Original® on the dipteran Chironomus xanthus. The endpoints evaluated included survival, growth, and emergence. The results showed that the 48 h LC₅₀ for glyphosate to C. xanthus was 251.5 mg a.e./L. Larval growth of C. xanthus was reduced under glyphosate exposure (LOEC for body length = 12.06 mg/L; LOEC for head capsule width = 0.49 mg/L). No effects were observed in terms of cumulative percentage of imagoes emergence. However, low concentrations of glyphosate caused delayed emergence of females (at 1.53 mg/L) and induced fast emergence of males (at 0.49 mg/L), compared to control treatment. The deleterious effects of environmental relevant concentrations of glyphosate (0.7 mg/L) observed in terms of C. xanthus growth and development suggest that glyphosate-based herbicides can have negative consequences for aquatic non-target invertebrates such as Chironomus. Multigerational assays are needed to assess the long term effects of glyphosate on C. xanthus populations. Finally, our study adds ecotoxicological data on the effects of glyphosate-based herbicides on tropical freshwater invertebrates.     

Biodegradation and Detoxification Efficiency of Azo-Dye Reactive Orange 16 by <Emphasis Type="Italic">Pichia kudriavzevii</Emphasis> CR-Y103

In consideration of the hazards associated with the presence of the textile azo-dye and their biotransformation products in the environment, the goal of this work was to study bioremediation process by the yeast strain Pichia kudriavzevii CR-Y103 related to the ability to degrade and detoxify the sulfonated Reactive Orange 16 azo-dye. In experimental conditions, the optimal inoculum/dye concentration ratio required for complete decolorization (100%) of culture medium and biomass within 24 h has been 1 g L^?1 yeast cell (dry weight)/50 mg L^?1 Reactive Orange 16. In the presence of 400 mg L^?1 of Reactive Orange 16 (RO16), 95% of the dye was removed after 72 h of incubation. Also, the yeast strain could decolorize other eight textile dyes (56.48–99.98% decolorization within 24 h). NADH-DCIP reductase and azo reductase activities were significantly increased (ca. 5.4 times and ca. 37 times, respectively) during the decolorization process. UV-VIS spectra, high-performance liquid chromatography (HPLC), and Fourier transform infrared spectroscopy (FTIR) analysis confirmed the presence of new biotransformation products in extracted metabolites, highlighting the partial biodegradation of the dye by the new yeast isolate. The phytotoxicity evaluation strongly supported the decreased toxicity of biodegraded products as minor inhibition on germination (%), root and shoots elongation of T. pratense L. and T. aestivum L. seedlings. Increasing of mitotic index value and decreasing the frequency of chromosomal aberrations in tested plant meristem cells treated with biodegraded products, compared with RO16 treatment (500 ppm), confirmed their slightly toxic nature. A cell viability assay also confirmed the reduced toxicity of biodegraded products on healthy monkey kidney cells (Vero cells).     

Effects of Single,Binary and Quinary Mixtures of Phenanthrene and Its N-PAHs on <Emphasis Type="Italic">Eisenia fetida</Emphasis> in Soil

It is now acknowledged that aromatic hydrocarbons present in contaminated soils occur in mixtures. The effect of single, binary and quinary mixtures of phenanthrene and selected nitrogen-containing polycyclic aromatic hydrocarbons (N-PAHs) were investigated on the survival, growth and behavioural index of earthworms (Eisenia fetida) over a 21-day incubation in soil. The results showed that the LC₅₀ values ranged from (not detected) ND–329.3 mg kg^?1 (single mixture), ND–219.8 mg kg^?1 (binary mixtures) to 148.4 mg kg^?1 (quinary mixture), while the EC₅₀ values (based on weight loss) ranged from 13.3–148.4 mg kg^?1 (single mixture), 63.8–148.4 mg kg^?1 (binary mixture) to 24.2 mg kg^?1 (quinary mixture). Greater impacts were recorded where N-PAHs are present with phenanthrene. Further, behavioural index of E. fetida was affected after 24-h exposure to N-PAH-amended soils. Among the N-PAHs however, benzo[h]quinoline recorded the greatest impact on the survival, growth and behavioural index of E. fetida in soil. Findings from this study showed that three ring-N-PAHs are more toxic than phenanthrene as expected from their physico-chemical properties. The binary and quinary mixtures of phenanthrene and N-PAHs in soil intensified toxicity, suggesting that PAHs-N-PAHs mixtures represent greater risk to soil biota.     

Effect of Metals on Decolorization of Reactive Blue HERD by <Emphasis Type="Italic">Comamonas</Emphasis> sp. UVS

Comamonas sp. UVS was able to decolorize Reactive Blue HERD (RBHERD) dye (50 mg L^?1) within 6 h under static condition. The maximum dye concentration degraded was 1,200 mg L^?1 within 210 h. A numerical simulation with the model gives an optimal value of 35.71?±?0.696 mg dye g^?1 cell h^?1 for maximum rate (V_max) and 112.35?±?0.34 mg L^?1 for the Michaelis constant (K_m). Comamonas sp. UVS has capability of decolorization of RBHERD in the presence of Mg²⁺, Ca²⁺, Cd²⁺, and Zn²⁺, whereas decolorization was completely inhibited by Cu²⁺. Metal ions also affected the levels of biotransformation enzymes during decolorization of RBHERD. Comamonas sp. UVS was also able to decolorize textile effluent with significant reduction in COD. The biodegradation of RBHERD dye was monitored by UV–vis spectroscopy, FTIR spectroscopy, and HPLC.     

Chemical Behavior of U(VI) in the Presence of Soil Components

Soil components from different environments (forest (OF), semiarid (SZ), and sand (AS)) were separated from fulvic and humic substances, characterized by DRX, EDS(SEM), and zero-charge points were determined. The sorption of U(VI) by these materials was determined considering contact time, concentration of U(VI), pH, ionic strength, and presence of sodium chloride and humic acids. The time to reach the kinetic sorption equilibrium was ca. 1 min for the components of the SZ and AS soils, whereas those from OF required longer times. The zero-charge points of the materials indicate that in the experimental conditions, the surfaces of the materials are positively charged, as are uranyl ions. The sorption kinetic data were well fitted to the pseudo-second-order model, which indicates chemical sorption. The maximum sorption capacities for U(VI) obtained from data fitted to the Langmuir model of OF and SZ were 49 and 19.8 mg g^?1 respectively. Sorption isotherm data for AS were best fitted to the Freundlich model (q_e?=?5.4 mg g^?1). The maximum values of distribution coefficients (K_d) were 23?±?7 L kg^?1, 545?±?64 L kg^?1, and 1178?±?229 L kg^?1 for AS, SZ, and OF, respectively; these values may depend on pH, contact time, initial concentration of U(VI), and the composition of the materials. Sodium chloride in the aqueous solutions affects U(VI) sorption by the materials SZ and AS. The effect of humic acids depends on pH, only in acid media soluble humate complexes may be formed.