Presence of bisphenol S and surfactants in the sediments of Kongsfjorden: a negative impact of human activities in Arctic?

Pollution and fate of pollutants in polar region are important topics of investigation in the last several decades. We have analysed sediment samples from Kongsfjorden and Krossfjorden, two sites from Arctic region, and detected a number of emerging contaminants (ECs) using high-resolution mass spectrometry connected to UPLC (LC-Q-ToF-MS). Out of the seven sampling sites selected, bisphenol S (BPS), an identified pollutant and plasticiser, was detected and quantified in three sediment samples from Kongsfjorden (≈ 0.2 ppm). Four major surfactants (decylbenzenesulphonic acid, undecylbenzenesulphonic acid, 2-dodecylbenzenesulphonic acid and tridecylbenzenesulphonic acid) were also identified. A possible metabolite of BPS (sulphur trioxide derivative of BPS) was identified in one of the samples. It is proposed that the presence of ECs is the result of human activities in the region for a long time. To the best our knowledge, this is the first report on the identification of BPS and surfactants in the Arctic region.

Hydroxyl radical induced oxidation of theophylline in water: a kinetic and mechanistic study.

Oxidative destruction and mineralization of emerging organic pollutants by hydroxyl radicals (˙OH) is a well established area of research. The possibility of generating hazardous by-products in the case of ˙OH reaction demands extensive investigations on the degradation mechanism. A combination of pulse radiolysis and steady state photolysis (H2O2/UV photolysis) followed by high resolution mass spectrometric (HRMS) analysis have been employed to explicate the kinetic and mechanistic features of the destruction of theophylline, a model pharmaceutical compound and an identified pollutant, by ˙OH in the present study. The oxidative destruction of this molecule, for intermediate product studies, was initially achieved by H2O2/UV photolysis. The transient absorption spectrum corresponding to the reaction of ˙OH with theophylline at pH 6, primarily caused by the generation of (T8-OH)˙, was characterised by an absorption band at 330 nm (k2 = (8.22 ± 0.03) × 10(9) dm(3) mol(-1) s(-1)). A significantly different spectrum (λmax: 340 nm) was observed at highly alkaline pH (10.2) due to the deprotonation of this radical (pKa∼ 10.0). Specific one electron oxidants such as sulphate radical anions (SO4˙(-)) and azide radicals (N3˙) produce the deprotonated form (T(-H)˙) of the radical cation (T˙(+)) of theophylline (pKa 3.1) with k2 values of (7.51 ± 0.04) × 10(9) dm(3) mol(-1) s(-1) and (7.61 ± 0.02) × 10(9) dm(3) mol(-1) s(-1) respectively. Conversely, oxide radicals (O˙(-)) react with theophylline via a hydrogen abstraction protocol with a rather slow k2 value of (1.95 ± 0.02) × 10(9) dm(3) mol(-1) s(-1). The transient spectral studies were complemented by the end product profile acquired by HRMS analysis. Various transformation products of theophylline induced by ˙OH were identified by this technique which include derivatives of uric acids (i, iv & v) and xanthines (ii, iii & vi). Further breakdown of the early formed product due to ˙OH attack leads to ring opened compounds (ix-xiv). The kinetic and mechanistic data furnished in the present study serve as a basic frame work for the construction of ˙OH induced water treatment systems as well as to understand the biological implications of compounds of this kind.

Fabrication of switchable protein resistant and adhesive multilayer membranes.

Fabrication of protein adhesive and resistant surfaces based on chitosan/polystyrene sulfonate (CHI/PSS) multilayer membranes is presented. Adsorption behavior of bovine serum albumin (BSA) and lysozyme to CHI/PSS multilayer was studied by simple adsorption method and under pressure driven (ultrafiltration) conditions. The protein incorporated membranes were characterized by FT-IR, UV-vis, SEM and AFM. The loading of proteins to the multilayer was found to be dependent on the nature of protein, pH, number of bilayers, methods of adsorption and time of adsorption. Simple adsorption resulted in BSA adhesive layers with some conformational changes at higher number of bilayers. Ultrafiltration leads to protein repellence at higher number of bilayers which is attributed to the presence of irremovable water. Lysozyme adsorption/sorption varied with pH. Surface coverage dominates at pH close to pI and at pH 5 under ultraflitration condition where as simple adsorption resulted in protein repellence at pI. The secondary structure of adsorbed lysozyme is preserved for a wide pH range (5-11). Desorption study of lysozyme adsorbed membranes at pH 8.8 was carried out to understand the adsorption/sorption of protein. Diffusion of the sorbed lysozyme from the inner layers to the surface is found to take place at lower concentrations of NaCl.

One-electron reduction of S-nitrosothiols in aqueous medium.

One-electron reduction of S-nitrosothiols (RSNO) has been studied using radiolytically produced reducing entity, the hydrated electron (e(aq)(-)), in aqueous medium. Both kinetics of the reaction and the mechanistic aspects of the decomposition of S-nitroso derivatives of glutathione, L-cysteine, N-acetyl-L-cysteine, N-acetyl-D,L-penicillamine, N-acetylcysteamine, L-cysteine methyl ester, and D,L-penicillamine have been investigated at neutral and acidic pH. The second-order rate constants of the reaction of e(aq)(-) with RSNOs were determined using a pulse radiolysis technique and were found to be diffusion controlled (10(10) dm(3) mol(-1) s(-1)) at neutral pH. The product analysis using HPLC, fluorimetry, and MS revealed the formation of thiol and nitric oxide as the major end products. It is therefore proposed that one-electron reduction of RSNO leads to the liberation of NO. There is no intermediacy of a thiyl radical as in the case of oxidation reactions of RSNOs. The radical anion of RSNO (RSN(*)O(-)) is proposed as a possible intermediate. The overall reaction could be written as RSNO + e(aq)(-) --H+--> RSH + (*)NO.

Photochemical production of hydroxyl radical from aqueous iron(III)-hydroxy complex: determination of its reaction rate constants with some substituted benzenes using deoxyribose-thiobartituric acid assay.

Hydroxyl radical (OH) production, mediated by UV light, from aqueous ferric perchlorate was investigated at low pH using a deoxyribose-thiobarbituric acid (-TBA) assay. The rate of production of OH was found to be dependent on the irradiation time. Addition of suitable substrates such as substituted benzenes can compete for the reaction of OH with deoxyribose, leading to a decreased yield of TBA chromogen formed from the deoxyribose-TBA assay. The second-order rate constants of the added substrates can be determined from such a simple competition kinetic method. The second-order rate constants for the reaction of OH with a number of substituted benzenes were determined using this method and the values were compared with the reported rate constants using pulse radiolysis technique. The values determined using the present method (1 to 8 x 10(9) dm3/mols) are in good agreement with those reported by use of the pulse radiolysis technique. It is proposed that the photoproduction of OH from aqueous ferric perchlorate coupled with deoxyribose-TBA assay is a simple and efficient method for determination of rate constants for the reaction of OH with a variety of substituted benzenes that are known to be organic water contaminants.