Acids In Aquatic Environments Research Articles

Prevalence of Neurotoxin Domoic Acid in Aquatic Environment of Bohai and Northern Yellow Seas in China

Prevalence of Neurotoxin Domoic Acid in Aquatic Environment of Bohai and Northern Yellow Seas in China

Sensitized Photolysis of Thioglycolic Acid in Aquatic Environment

The photochemical transformations of thioglycolic acid using model systems was studied by varying the irradiation sources and the kinetic parameters were determined. It was found that thioglycolic acid undergoes destruction on induced photolysis in the presence of humic substances, and its half-life can be estimated as 10-14 days, depending on weather conditions (cloudiness, time of day, season etc.). Results obtained in the course of this study on model systems were transferred to natural waters, and it was concluded that thioglycolic acid has a positive influence on the chemical self-purification processes of water, in the natural aquatic environment. This is manifested by increasing the self-purification capacity of water, due to the generation of active oxygen species, which lead to the degradation not only of this thiol, but of other pollutants present in aquatic environment, as well. At the same time, the products of the transformations are harmless to the aquatic environment and hydrobionts.

Susceptibility of Aeromonas hydrophila to Medium-Chain Fatty Acids and their Monoesters

Abstract Medium-chain fatty acids (MCFAs) and their monoesters were tested for their antibacterial activity against the Gram-negative pathogen Aeromonas hydrophila. The antimicrobial effect was evaluated at two temperatures (4 °C and 37 °C) using a standardized microdilution method in a 96-well microtitration plate. The minimum inhibitory concentrations of selected MCFAs were determined as the lowest concentration limiting the growth of A. hydrophila in wells compared to a positive control of ≥ 80%. The results indicated that the most effective compound against A. hydrophila was sucrose monocaprate after incubation at 37 °C (0.625 mg ml−1), whereas monocaprylin was the most effective compound after incubation at 4 °C (1.25 mg ml−1). Free MCFAs showed no antibacterial effects towards this bacterium. Low solubility and sensory properties could limit the use of fatty acids in aquatic environment, which should be the subject of further studies.

Occurrence and transformation of phenoxy acids in aquatic environment and photochemical methods of their removal: a review

The article presents the behavior of phenoxy acids in water, the levels in aquatic ecosystems, and their transformations in the water environment. Phenoxy acids are highly soluble in water and weakly absorbed in soil. These highly mobile compounds are readily transported to surface and groundwater. Monitoring studies conducted in Europe and in other parts of the world indicate that the predominant phenoxy acids in the aquatic environment are mecoprop, 4-chloro-2-methylphenoxyacetic acid (MCPA), dichlorprop, 2,4-dichlorophenoxyacetic acid (2,4-D), and their metabolites which are chlorophenol derivatives. In water, the concentrations of phenoxy acids are effectively lowered by hydrolysis, biodegradation, and photodegradation, and a key role is played by microbial decomposition. This process is determined by the qualitative and quantitative composition of microorganisms, oxygen levels in water, and the properties and concentrations of phenoxy acids. In shallow and highly insolated waters, phenoxy acids can be decomposed mainly by photodegradation whose efficiency is determined by the form of the degraded compound. Numerous studies are underway on the use of advanced oxidation processes (AOPs) to remove phenoxy acids. The efficiency of phenoxy acid degradation using AOPs varies depending on the choice of oxidizing system and the conditions optimizing the oxidation process. Most often, methods combining UV radiation with other reagents are used to oxidize phenoxy acids. It has been found that this solution is more effective compared with the oxidation process carried out using only UV.

Effect of co-existing Co2+ ions on the aggregation of humic acid in aquatic environment: Aggregation kinetics, dynamic properties and fluorescence spectroscopic study

The fate and transport of humic substances in the aquatic environments depend significantly on their interactions with co-existing ions. Herein, we employed dynamic light scattering (DLS) measurement, molecular dynamic (MD) simulation and fluorescence spectrometry to investigate the aggregation of humic acid (HA) in the presence of Co2+ ions. The aggregation kinetics was depicted by hydrodynamic diameter (<Dh>) and the attachment efficiency (α) of HA aggregates. α increases gradually in the reaction-limited (slow) regime due to the decrease of the double layer repulsion, and the energy barrier is eliminated to a certain extent in the diffusion-limited reaction while α close to unity. The complexation between functional groups (i.e. carboxylic and phenolic groups) of HA and Co2+ ions contributes significantly to the aggregation process of HA. MD simulation and density functional theory (DFT) calculation demonstrate that the aggregation process of HA can be promoted by Co2+ through several inter- or intra-molecular interactions between HA and the Co2+ ions. The results provide a pathway for insight into the interactions between HA and metal ions, which is important for deeply understanding the environmental behaviors of HA in natural aqueous systems.

Solubilized Chitosan Biopolymers for Sequestration of Organic Acids in Aquatic Environments after Biodegradation in a Constructed Wetland Treatment System

Solubilized Chitosan Biopolymers for Sequestration of Organic Acids in Aquatic Environments after Biodegradation in a Constructed Wetland Treatment System

The impact of varying abiotic humification conditions and the resultant structural characteristics on the copper complexation ability of synthetic humic-like acids in aquatic environments

Humic acid (HA) has a high complexation ability with metal ions due to its functional groups. In this study, 11 synthetic humic-like acids (SHLAs) were prepared under varying abiotic humification conditions: precursor species (glycine-catechol and glycine-catechol-glucose), precursor concentrations (from 0.25 M:0.25 M to 1 M:1 M), pH (6–8), temperature (25–45 °C) and mass of MnO2 catalyst (1.3–2.5% w/v). The effect of the varying humification conditions on the complexation ability of the SHLA for Cu2+ were investigated together with the relationships between Cu complexation ability and the structure of the SHLAs (elemental composition, type and content of functional groups, AL/AR, E4/E6). Conditional stability constants (log K) of the SHLAs ranged from 6.00 to 6.42 and complexation capacities ranged from 1.76 mmol/g to 2.61 mmol/g. SHLAs synthesized at lower temperature (25 ℃), pH 8, low precursor concentrations (glycine:catechol= 0.25 M:0.25 M) and a larger proportion of catalyst (2.5% w/v) had a larger copper complexation ability. Log K values of SHLAs had significant positive correlations with carboxylic carbon (r = 0.671, p < 0.05), carboxylic group content (r = 0.890, p < 0.01) and O/C ratio (r = 0.618, p < 0.05), and significant negative correlations with aliphatic carbon (r = −0.616, p < 0.05), total C (r = −0.685, p < 0.05) and total H contents (r = −0.654, p < 0.05). Complexation capacities had a significant positive correlation with total N (r = 0.826, p < 0.01) and a significant negative correlation with C/N ratio (r = −0.823, p < 0.01).

Chitosan Biopolymers for Analysis of Organic Acids in Aquatic Environments of Treatment Wetlands

Herein, we report on the use of chitosan-based engineered materials for the sequestration of naphthenic acid fraction compounds (NAFCs) and other species (matrix) in oil sands process-affected water (OSPW) in order to improve monitoring of NAFCs after phytoremediation. Chitosan pellets (CPs) were cross linked with glutaraldehyde (GLU) at variable feed ratios and characterized using thermogravimetric analysis (TGA). Sorption studies at equilibrium and kinetic conditions were carried on OSPW extract, raw and treated wetland samples. The materials were shown to have similar sorption capacity for NAFCs but with variable selectivity of the species in the complex mixture. As well, the matrix uptake varied according to the type of OSPW. Overall, CP in its native form outperformed the cross linked CP pellets, as evidenced by a reduction in matrix effects.

Green chemistry approach to analysis of formic acid and acetic acid in aquatic environment by headspace water-based liquid-phase microextraction and high-performance liquid chromatography

ABSTRACTA simple and totally organic-free (green) method, viz. headspace water-based liquid-phase microextraction combined with high-performance liquid chromatography-ultraviolet detection has been successfully developed for analysis of formic acid and acetic acid in environmental water samples. A microdrop of an aqueous solution of sodium hydroxide was suspended from the tip of a microsyringe needle over the headspace of the stirred sample solution containing the analytes at pH 1.0 for a given time. The microdrop was then retracted into the microsyringe, diluted with HPLC mobile phase, and injected to HPLC. Optimum efficiency has been achieved for: 3.0 µL NaOH microdrop (0.1 mol L−1) exposed for 15 min over the headspace of an aqueous sample of 6.5 mL at 55 °C, containing 15% w/v of Na2SO4, adjusted to pH = 1.0 and stirred at 750 rpm. Under these conditions, enrichment factors of 162 and 187, limits of detection of 0.3 and 0.1 µg L−1 (S/N = 3) with dynamic linear ranges of 1–500 and 0.5–500 µg L−1 were obtained for formic acid and acetic acid, respectively. A reasonable repeatability (5.8% ≤ RSD ≤ 8.8%, n = 6) and satisfactory linearity (r2 ≥ 0.997) illustrated the performance of the method.

The influence of mechanochemical modification on prevention of toxic ability of humic acids towards phenanthrene in aquatic environment

The aim of the research work is to quantify interaction between phenanthrene with modified humic acids in aquatic environment. The changes in the structure and properties of humic acids after modifications were studied with 1H NMR spectroscopy and potentiometric titration methods. Our research demonstrates that the application of thiourea as a modified agent increases the binding capacity of humic acids towards phenanthrene.

Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Characterization of Tunable Carbohydrate-Based Materials for Sorption of Oil Sands Naphthenic Acids

The potential for sorption and possible degradation of components in oil sands processed water (OSPW) by the use of synthetically engineered co-polymers is receiving growing attention. Recent research has highlighted the sorption of total oil sands naphthenic acid fraction components (NAFCs) by β-cyclodextrin (β-CD) co-polymers. The incorporation of β-CD within co-polymer frameworks represents a novel modular approach with significant potential for controlled tuning of the textural mesoporosity of the sorbents. Herein, we report the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) characterization of aqueous samples containing oil sands NAFCs following sorption with a range of cyclodextrin-based co-polymers. The materials investigated were β-CD cross-linked with three different types of diisocyanates, namely, (i) 4,4′-dicyclohexylmethane diisocyanate, (ii) 4,4′-diphenylmethane diisocyanate, and (iii) 1,4-phenylene diisocyanate. Variable sorption of NAFCs was observed according to the cross-linking density of the co-polymer framework and the nature of the cross-linker unit. Furthermore, the sorption of the NAFCs by the co-polymers was not affected by other parameters, such as metal ions, salinity, and non-oil sands acid fractions present in OSPW. The observation of molecular selective sorption in co-polymer materials containing β-CD represents an important contribution toward the development of sorbent materials for the controlled removal of oil sands acids in aquatic environments. The FT-ICR MS measurements also contribute further to the understanding of the thermodynamic sorption mechanism of such materials.

Photodegradation of salicylic acid in aquatic environment: Effect of different forms of nitrogen

Salicylic acid (SA), as an extensively used compound, can be detected in a great variety of environmental water samples. Photodegradation is important in many ways. The present study concerns the environmental behavior of SA under simulated sunlight. A kinetic model was used for SA degradation in water, and the variations of the photodegradation of SA in the presence of different initial concentrations, different oxygen levels, different forms of nitrogen and different pE values in the aquatic environment were determined. Experiments demonstrated that the photodegradation process had pseudo-first-order reaction kinetics. The photodegradation rate decreased with increasing initial concentration and increased with increasing oxygen level. The NO3− and NO2− ions promoted photodegradation of SA, but increases of NH4+ concentration had no effect. The form of nitrogen depends on pE, which therefore has a significant influence on the photodegradation of SA. When the pE value increased gradually, there was a transformation of NH4+ to NO2− and then to NO3−. The photodegradation rate of SA first increased, then decreased and finally increased again. When NO2− and NH4+ coexisted, the photodegradation rate was almost the same as it was in the presence of NO2− alone. When NO2− and NO3− coexisted, the promoting effect on the photodegradation SA was less than the sum of the partial promoting effects. The results indicated that NO2− had an obvious antagonistic action on NO3− when NO3− and NO2− coexisted in the aquatic environment.

Photolysis of benzotriazole and formation of its polymerised photoproducts in aqueous solutions under UV irradiation

Environmental contextBenzotriazole is an anti-corrosion agent that is widely applied in various industrial processes and in household products. It has been found persistent in various aquatic environments. Our investigation found that benzotriazole can be rapidly transformed under UV light to form several photoproducts. Photolysis rates decreased with increasing solution pH, whereas salinity had no significant effect. Metal species Cu2+ and Fe3+, and humic acid in aquatic environment could have inhibitory effects on the photolysis of benzotriazole. AbstractBenzotriazole (BT) is an anti-corrosion agent used widely in some industrial processes and household products, and it has been detected in surface water and ground water due to its high mobility and low biodegradability. We have investigated the photolysis of benzotriazole in aqueous solutions under UV radiation at 254 nm and the effect of pH, salinity, metal species and dissolved organic matter on the photo-transformation processes. Benzotriazole was found to undergo rapid transformation to form several photoproducts. The half-lives for the photolysis of benzotriazole ranged from 2.8 to 14.3 h in various aqueous solutions containing metal ions and dissolved organic matter. Photolysis rates decreased with increasing solution pH, whereas salinity had no significant effect. Metal species Cu2+ and Fe3+, and especially humic acid had inhibitory effects on the photolysis of benzotriazole under UV light irradiation at 254 nm. We propose the formation of three major photoproducts via instantaneous polymerisation of small intermediates generated during the photolysis of benzotriazole including 2,6-diethylaniline, phenazine and 1,6-dihydroxyphenazine.

A Review of the Occurrence and Fate of Naphthenic Acids in Aquatic Environments

Naphthenic acids are comprised of a large collection of saturated aliphatic and alicyclic carboxylic acids found in hydrocarbon deposits (petroleum, oil sands bitumen, and crude oils). Naphthenic acids enter surface water systems primarily through effluent discharge, but also through groundwater mixing and erosion of riverbank oil deposits. Of the possible environmental receptors (i.e., air, soil, and water), the most significant is water. Ambient levels of naphthenic acids in northern Alberta rivers in the Athabasca Oil Sands are generally below 1 mg L−1. However, tailings pond waters may contain as high as 110 mg L−1. The complexity of natural naphthenic acids in petroleum deposits poses an analytical challenge as reflected by the several techniques reported for quantitation of naphthenic acids in the environment. Although naphthenic acids are known to be persistent biomarkers used in identification of oil source maturation, little is established regarding their relative degradation pathways in aquatic environments. Published research related to the potential for microbiological degradation and adsorption to typical Athabasca Oil Sands soils reveal that naphthenic acids are likely to persist in the water column and, with prolonged exposure, accumulate in sediments. However, other than a very general knowledge of environmental persistence, the occurrence and fate of naphthenic acids has been sparsely studied. This article brings together some of those environmental persistence results, as well as detailed information regarding the origin of naphthenic acids in tailings ponds, chemistry and toxicological considerations, current analytical methods for aquatic sampling, and areas of future remediation research.

The measurement and distribution of dissolved nucleic acids in aquatic environments

Nucleic acids (DNA and RNA) are ubiquitous components of the dissolved organic matter (DOM) pool of all oceanic, neritic, estuarine, and freshwater habitats studied to date. A new method for the quantitative determination of dissolved nucleic acids (DNA and RNA) in water and sediment samples was developed, evaluated, and utilized in a study of various marine and freshwater ecosystems. Under appropriate reaction conditions, dissolved DNA (D‐DNA) and dissolved RNA (D‐RNA) are efficiently removed from solution with the addition of cetyltrimethylammonium bromide (CTAB) and subsequent formation of insoluble CTA‐nucleic acid salts. The insoluble salts are collected, by filtration, onto glass‐fiber filters and analyzed for DNA and RNA with fluorometric and colorimetric procedures, respectively. The performance of this CTAB method is simple, reliable, and reproducible for measuring dissolved nucleic acids in natural aquatic environments. For the ecosystems investigated herein, D‐DNA and D‐RNA concentrations ranged from 0.56 to 88 µg liter−1 and 4.03 to 871 µg liter−1; the ratio of D‐RNA to D‐DNA ranged from 4.1 to 11.5.