Effect of Trivalent and Hexavalent Chromium on Carbohydrate Metabolism of a Freshwater Field Crab, Barytelphusa guerini

The in vivo toxic impact of chromium in its two forms(trivalent and hexavalent) on glycogen metabolism in the tissuesof freshwater field crab Barytelphusa guerini was studied.In a sublethal long-term exposure of 30, 60 and 90 days, thedepletion of glycogen and glucose levels reflected in theactivity of glycogenphosphorylases `a' and `ab'. A tissuespecific and time-dependent variation in tissue glucose reservesparelleled the progressive accumulation of haemolymph sugars.Trivalent and hexavalent chromium induced alterations in metabolite levels and in enzyme activities in the tissues. Themagnitude of responses were found more in the hexavalent formthan in trivalent form.     

Disinfection byproducts in chlorinated or brominated swimming pools and spas: Role of brominated DBPs and association with mutagenicity

Although the health benefits of swimming are well-documented, health effects such as asthma and bladder cancer are linked to disinfection by-products (DBPs) in pool water. DBPs are formed from the reaction of disinfectants such as chlorine (Cl) or bromine (Br) with organics in the water. Our previous study (Daiber et al., Environ. Sci. Technol. 50, 6652; 2016) found correlations between the concentrations of classes of DBPs and the mutagenic potencies of waters from chlorinated or brominated swimming pools and spas. We extended this study by identifying significantly different concentrations of 21 individual DBPs in brominated or chlorinated pool and spa waters as well as identifying which DBPs and additional DBP classes were most associated with the mutagenicity of these waters. Using data from our previous study, we found that among 21 DBPs analyzed in 21 pool and spa waters, the concentration of bromoacetic acid was significantly higher in Br-waters versus Cl-waters, whereas the concentration of trichloroacetic acid was significantly higher in Cl-waters. Five Br-DBPs (tribromomethane, dibromochloroacetic acid, dibromoacetonitrile, bromoacetic acid, and tribromoacetic acid) had significantly higher concentrations in Br-spa versus Cl-spa waters. Cl-pools had significantly higher concentrations of Cl-DBPs (trichloroacetaldehyde, trichloromethane, dichloroacetic acid, and chloroacetic acid), whereas Br-pools had significantly higher concentrations of Br-DBPs (tribromomethane, dibromoacetic acid, dibromoacetonitrile, and tribromoacetic acid). The concentrations of the sum of all 4 trihalomethanes, all 11 Br-DBPs, and all 5 nitrogen-containing DBPs were each significantly higher in brominated than in chlorinated pools and spas. The 8 Br-DBPs were the only DBPs whose individual concentrations were significantly correlated with the mutagenic potencies of the pool and spa waters. These results, along with those from our earlier study, highlight the importance of Br-DBPs in the mutagenicity of these recreational waters.     

Unravelling the photoprotective effects of freshwater alga Nostoc commune Vaucher ex Bornet et Flahault against ultraviolet radiations

Environmental Science and Pollution Research - Several studies have suggested the direct relationship between skin complications, air pollution, and UV irradiation. UVB radiations cause various...     

Targeting natural products against SARS-CoV-2

Environmental Science and Pollution Research - The human coronavirus disease (COVID-19) pandemic is caused by a novel coronavirus; the Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2)....     

A balancing act: Optimizing free chlorine contact time to minimize iodo-DBPs, NDMA, and regulated DBPs in chloraminated drinking water

Many drinking water treatment plants in the U.S. have switched from chlorination to chloramination to lower levels of regulated trihalomethane (THM) and haloacetic acid (HAA) disinfection byproducts (DBPs) in drinking water and meet the current regulations. However, chloramination can also produce other highly toxic/carcinogenic, unregulated DBPs: iodo-acids, iodo-THMs, and N-nitrosodimethylamine (NDMA). In practice, chloramines are generated by the addition of chlorine with ammonia, and plants use varying amounts of free chlorine contact time prior to ammonia addition to effectively kill pathogens and meet DBP regulations. However, iodo-DBPs and nitrosamines are generally not considered in this balancing of free chlorine contact time. The goal of our work was to determine whether an optimal free chlorine contact time could be established in which iodo-DBPs and NDMA could be minimized, while keeping regulated THMs and HAAs below their regulatory limits. The effect of free chlorine contact time was evaluated for the formation of six iodo-trihalomethanes (iodo-THMs), six iodo-acids, and NDMA during the chloramination of drinking water. Ten different free chlorine contact times were examined for two source waters with different dissolved organic carbon (DOC) and bromide/iodide. For the low DOC water at pH 7 and 8, an optimized free chlorine contact time of up to 1 h could control regulated THMs and HAAs, as well as iodo-DBPs and NDMA. For the high DOC water, a free chlorine contact time of 5 min could control iodo-DBPs and NDMA at both pHs, but the regulated DBPs could exceed the regulations at pH 7.     

Sonochemical degradation of aromatic organic pollutants

This work examines the use of ultrasound to mineralize 4-chlorophenol, 2,4-dichlorophenol, [aryl-2H3]2,4-dichlorophenol, 4-chloro-3,5-dimethylphenol, 4-fluorophenol, 2,4,6-trinitrotoluene, 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dinitrotoluene in dilute aqueous solution. Mineralization rates were determined as a function of substrate structure and concentration, bulk phase temperature, pH and the presence of co-solutes such as detergents and humic acids. All substrates were found to degrade sonochemically, as evidenced by the release of Cl- and NO3- respectively. Product analyses by GC-MS, HPLC, and micellar electrokinetic capillary chromatography (MECC) indicated mineralization with little formation of organic byproducts, a significant advantage over other remediation methods. Chloride release from chlorophenols was approximately proportional to substrate total chlorine content, irrespective of structural differences, and reached 80% of the theoretical limit. Fluoride release from 4-fluorophenol was ca. 10-fold lower than that of chloride from 4-chlorophenol. Changes in the bulk phase temperature from 9.5 to 34 degrees C, and 12.5 to 30 degrees C, respectively, were of little consequence to observed mineralization rates for nitroaromatics and chlorophenols. A significant mineralization rate increase resulted from sonication of 4-chlorophenol in acidified media. Additions of amphiphilic co-solutes resulted in modest, but statistically significant, sonolysis enhancements.