Formation of hydroxyl radical (·OH) in illuminated surface waters contaminated with acidic mine drainage

“…Still, the mechanisms underlying • OH formation from non- 3 DOM* species (e.g., excited state oxidants of unknown identity) warrant further investigation. Other pathways of • OH formation, such as photo-Fenton reactions − and NO 3 – photolysis, ,, might be operative apart from direct photolysis of DOM. ,,,, Compared to naturally acidic waters containing elevated [Fe] (e.g., acid mine drainage waters, , coastal rivers, , Arctic streams), Adirondack lake waters featured much lower [Fe] (0.73 ± 1.02 μM) and mildly acidic pH, so the photo-Fenton pathway was less likely a main contributor to Φ app, • OH despite the fact that • OH formation does not necessarily scale proportionally to [Fe] , and could operate at circumneutral pH. ,, On the other hand, the low [NO 3 – ] to [DOC] ratio (0.13 ± 0.17 mg NO 3 – /mg C) in Adirondack lake waters indicated that the contribution of NO 3 – photolysis to Φ app, • OH was minor as this pathway only becomes a competitive source of • OH in surface waters with elevated [NO 3 – ] (e.g., ≥ 2.0 mg NO 3 – /mg C). ,, …”

Section: Results and Discussionmentioning

confidence: 99%

Photochemical Characterization of Surface Waters from Lakes in the Adirondack Region of New York

Wasswa

Driscoll

Zeng

2020

Environ. Sci. Technol.

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The Adirondack Mountain region of New York, a historical hotspot for atmospheric sulfur and nitrogen deposition, features abundant lakes that are experiencing browning associated with recovery from acidification. Yet, much remains unknown about the photoreactivity of Adirondack lake waters. We quantified the apparent quantum yields (Φ app,RI ) of photochemically produced reactive intermediates (RIs), such as excited triplet states of dissolved organic matter ( 3 DOM*), singlet oxygen ( 1 O 2 ), and hydroxyl radicals ( • OH), for surface waters collected from 16 representative Adirondack lakes. Φ app, 3 DOM* and Φ app, 1 O 2 for native Adirondack lake waters fell within ranges reported for whole waters and DOM isolates from various sources, while Φ app, • OH were substantially lower than those measured for other aquatic samples. Orthogonal partial least squares and multiple linear regression analyses identified the spectral slope coefficient from 290 to 400 nm (S 290−400 ) as the most effective predictor of Φ app,RI among measured water chemistry parameters and bulk DOM properties. Φ app,RI also exhibited divergent responses to controlled pH adjustment and aluminum or iron addition simulating hypothetical scenarios relevant to past and future water chemistry conditions of Adirondack lakes. This study highlights the need for continued research on changes in photoreactivity of acid-impacted aquatic ecosystems in response to browning and subsequent impacts on photochemical processes.

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“…Reactive oxygen species ͑ROS͒, which include hydrogen peroxide ͑H 2 O 2 ͒ and hydroxyl radicals ͑ · OH͒ occur in rain 1,2 and surface waters. 3,4 ROS play an important role in natural processes in aquatic systems, including, radiolysis, 5,6 pyrite oxidation, [7][8][9] and photochemical oxidation. 10,11 Hydrogen peroxide also is intentionally added to wastewaters to promote in situ oxidation processes 12,13 by leveraging the extreme reactivity of radicals toward organic pollutants.…”

Section: Introductionmentioning

confidence: 99%

Quantifying hydrogen peroxide in iron-containing solutions using leuco crystal violet

Cohn

2005

Geochem. Trans.

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Hydrogen peroxide is present in many natural waters and wastewaters. In the presence of Fe͑II͒, this species decomposes to form hydroxyl radicals, that are extremely reactive. Hence, in the presence of Fe͑II͒, hydrogen peroxide is difficult to detect because of its short lifetime. Here, we show an expanded use of a hydrogen peroxide quantification technique using leuco crystal violet ͑LCV͒ for solutions of varying pH and iron concentration. In the presence of the biocatalyst peroxidase, LCV is oxidized by hydrogen peroxide, forming a colored crystal violet ion ͑CV + ͒, which is stable for days. The LCV method uses standard equipment and allows for detection at the low microM concentration level. Results show strong pH dependence with maximum LCV oxidation at pH 4.23. By chelating dissolved Fe͑II͒ with EDTA, hydrogen peroxide can be stabilized for analysis. Results are presented for hydrogen peroxide quantification in pyrite-water slurries. Pyrite-water slurries show surface area dependent generation of hydrogen peroxide only in the presence of EDTA, which chelates dissolved Fe͑II͒. Given the stability of CV + , this method is particularly useful for field work that involves the detection of hydrogen peroxide.

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Formation of hydroxyl radical (·OH) in illuminated surface waters contaminated with acidic mine drainage

Cited by 14 publications

References 23 publications

Photostability and photolability of dissolved organic matter upon irradiation of natural water samples under simulated sunlight

Photostability and photolability of dissolved organic matter upon irradiation of natural water samples under simulated sunlight

Photochemical Characterization of Surface Waters from Lakes in the Adirondack Region of New York

Quantifying hydrogen peroxide in iron-containing solutions using leuco crystal violet

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