Chloroform has been for a long time considered only as an anthropogenic contaminant. The presence of chloroform in forest soil and groundwater has been widely demonstrated. The frequent detection of chloroform in groundwater in absence of other contaminants suggests that chloroform is likely produced naturally. Compound-specific isotope analysis of chloroform was performed on soil-gas and groundwater samples to elucidate whether its source is natural or anthropogenic. The δ 13 C values of chloroform (−22.8 to −26.2‰) present in soil gas collected in a forested area are within the same range as the soil organic matter (−22.6 to −28.2‰) but are more enriched in 13 C compared to industrial chloroform (−43.2 to −63.6‰). The δ 13 C values of chloroform at the water table (−22.0‰) corresponded well to the δ 13 C of soil gas chloroform, demonstrating that the isotope signature of chloroform is maintained during transport through the unsaturated zone. Generally, the isotope signature of chloroform is conserved also during longer range transport in the aquifer. These δ 13 C data support the hypothesis that chloroform is naturally formed in some forest soils. These results may be particularly relevant for authorities' regulation of chloroform which in the case of Denmark was very strict for groundwater (<1 μg/L).
N-Nitrosamines are potent mutagens and carcinogens that can be formed during oxidative water treatment. This study describes a novel method for the determination of total N-nitrosamines by UV-photolysis and subsequent chemiluminescence detection of nitric oxide. Denitrosation of N-nitrosamines was accomplished with a microphotochemical reactor consisting of a knitted reaction coil and a low-pressure mercury lamp. The detection limits for differing N-nitrosamines ranged between 0.07 μM (14 pmol injected) and 0.13 μM (26 pmol injected). The nitric oxide formation from selected N-nitrosamines was linear (R = 0.98-0.99) from 0.1 to 10 μM. The small cross-section and volume of the microphotochemical reactor used in this study was optimal to reach a sensitivity level comparable to chemical denitrosation-based methods. In addition, this method had several advantages over other similar methods: (i) compared to chemical denitrosation with copper monochloride or triiodide, the UV-photolysis does not require chemicals and is not affected by interferences of byproducts (e.g., formation of NOI), (ii) the reproducibility of replicates was enhanced compared to the triiodide-based method, and (iii) a commercially available photoreactor and NO analyzer were used. The application of this method for the determination of the N-nitrosamine formation potential of personal care products demonstrates its utility for assessing whether N-nitrosodimethylamine (NDMA) or other specific nitrosamines of current interest are dominant or minor components, respectively, of the total N-nitrosamine pool in technical aquatic systems or biological samples.
Ocean acidification induced by the increase of anthropogenic CO 2 emissions has a profound impact on marine organisms and biogeochemical processes. 1 The response of marine microbial activities to ocean acidification might play a crucial role in the future evolution of air-sea fluxes of biogenic gases such as nitrous oxide (N 2 O), a strong greenhouse gas and the dominant stratospheric ozone-depleting substance. 2 Here, we examine the response of N 2 O production from nitrification to acidification in a series of incubation experiments conducted in subtropical and subarctic western North Pacific. The experiments show that, when pH was reduced, the N 2 O Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:
Nitrous oxide (N 2 O) is an atmospheric trace gas playing an important role in both radiative forcing and stratospheric ozone depletion. The oceans are the second most important natural source of N 2 O. The magnitude of the flux of this source is poorly constrained. Moreover, the relative importance of the microbial processes leading to the formation or the consumption of N 2 O in oceans remains unclear. We present here fluxes and isotope and isotopomer signatures of N 2 O measured at three stations located along a latitudinal transect in subtropical and subarctic western North Pacific. These results indicate that about 30% to 55% of the oceanic flux of N 2 O to the atmosphere originates from the deep euphotic and shallow aphotic zones. The sea-to-air fluxes of N 2 O calculated using an isotope mass balance model indicate that the emission rate of N 2 O in subarctic waters is about 2 times higher than in oligotrophic subtropical waters suggesting that nutrient-rich water coming from the western subarctic gyre stimulates the N 2 O production. Moreover, isotopomer analysis has revealed that in shallow water N 2 O originates from nitrification and nitrifier denitrification processes, and its distribution in the water column is partly controlled by the incident solar radiation. The results of this study contribute to better constrain the global N 2 O budget and provide important information to better predict the future evolution of the oceanic emissions of N 2 O.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.