Measurement of dark, particle-generated superoxide and hydrogen peroxide production and decay in the subtropical and temperate North Pacific Ocean (original) (raw)
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Hydrogen peroxide in deep waters of the North Pacific Ocean
Geophysical Research Letters, 2004
Hydrogen peroxide is a reactive oxygen intermediate that can play a role in a variety of redox cycles. In the ocean, it is generally considered to be dominantly photoproduced with negligible concentrations in deep waters. We have utilized a highly sensitive analytical method to investigate hydrogen peroxide in deep waters of the North Pacific Ocean. We present evidence that hydrogen peroxide exists in low nanomolar concentrations in these deep waters with an apparent minimum in the depth range of the oxygen minimum. A consideration of possible mechanisms and rates suggests both a short ($12 day) residence time as well as a biological origin for this deep hydrogen peroxide. Hydrogen peroxide is probably of minor importance to metal cycling in the deep ocean except in low oxygen environments.
Distribution of hydrogen peroxide in the northwest Pacific Ocean
Geochemistry, Geophysics, Geosystems, 2005
Hydrogen peroxide (H 2 O 2) is a reactive oxygen intermediate involved in the cycling of metals and dissolved organic matter. Because little is known of its distribution in the North Pacific Ocean, we determined H 2 O 2 in surface waters continuously and obtained vertical profiles at nine stations during a cruise from Japan to Hawaii. Surface water H 2 O 2 varied from less than 10 to more than 250 nmol dm À3. A diel cycle in surface water H 2 O 2 ($25 nmol dm À3) was observed only on one day during the monthlong cruise. This is contrary to expectations based on the usual assumption of photo-production as the dominant input of H 2 O 2. Experiments were also conducted during the cruise to examine both photo-production and dark decay. The net rate of photo-production at a station near Hawaii was determined to be 8 nmol dm À3 h À1 , similar to rates reported for the central Atlantic Ocean and Antarctic. However, this maximum estimate of photo-production is also similar to probable rates of H 2 O 2 input by other mechanisms (biological production and rain). The pseudo-first-order rate constant for dark decay varied from 0.1 to 0.2 d À1 , which is toward the low end of previous reports of H 2 O 2 decay rates, and was observed to increase proportionately to the dissolved organic carbon concentration. Taken together, these results suggest that photo-production of H 2 O 2 in open ocean waters may be less important than previously thought and therefore H 2 O 2 is likely less of an indicator of the photo-chemical reactivity of surface waters than hoped for. Furthermore, we observed that the H 2 O 2 inventory for the upper 200 m of the water column has a maximum at midlatitudes. We suggest that this results from diminished inputs at high latitude as well as increased decay rates at low latitudes.
2010
This thesis comprises the following manuscripts: Manuscript 1: Application of a Superoxide (O 2-) thermal source (SOTS-1) for the determination and calibration of O 2 fluxes in seawater Published in Analytica Chimica Acta, 2010 Contribution: Maija I. Heller developed the analytical methods and planned and performed all the experiments, evaluated the data and wrote the paper. The underlying theory for the mathematical description of the data was developed in cooperation with Peter L. Croot who also assisted with the interpretation of the data and the writing of the paper.
The distribution of hydrogen peroxide in the southern and central Atlantic ocean
Deep Sea Research Part II: Topical Studies in Oceanography, 2001
The near-surface distribution and processes controlling the distribution of hydrogen peroxide were examined in the South and central Atlantic Ocean during a transect from Uruguay to Barbados in May and June 1996. Four kinds of field experiments were conducted during the cruise including diel observations, dark decay experiments, photochemical production experiments, and hydrogen peroxide-enrichment experiments. Significant diel variations ($25 nM) of hydrogen peroxide were observed, with surface-water concentrations increasing during the day and decreasing at night. With a dark decay half-life of 5.5 days and a net rate of photochemical production of 8.3 nM/h at local noon, it appears that both decay rate and photo-production rate of hydrogen peroxide are much smaller in oligotrophic seawater than in coastal seawater. The experimental results indicate that: (1) the decay reaction is a second-order reaction over all, first-order with both the concentration of hydrogen peroxide and the concentration of colloidal material; (2) seawater in the study area could restore its ambient levels of hydrogen peroxide in about 4 d after external perturbations. A total of 20 vertical profiles were obtained at 11 stations that can be classified as: surface maximum, surface mixed, and sub-surface maximum. Generally, the concentration of H 2 O 2 decreased with depth to less than 5 nM below 200 m. Hydrogen peroxide also was determined in some water samples from below 200 m, which revealed a slight increase of hydrogen peroxide with depth. In the surface waters of the open ocean, hydrogen peroxide increased with latitude from about 24 nM in the south (33.88S) to about 80 nM in the north (8.98N). This latitudinal variation of hydrogen peroxide correlated with model-calculated solar irradiance, satellite-measured wet deposition, depth of the mixed layer, and possibly total organic carbon. The water-column hydrogen peroxide inventory varied from 1.5 to 6.3 Â 10 À3 mol/m 2. Although the greatest shallow water concentrations were observed at stations in the Amazon plume, these stations showed a dramatic decrease in hydrogen peroxide with depth and integrated-water-column hydrogen peroxide was not significantly higher than at open ocean stations.
Journal of Geophysical Research, 2010
The decay kinetics of superoxide (O 2 −) reacting with organic matter was examined in oligotrophic waters at, and nearby, the TENATSO ocean observatory adjacent to the Cape Verde archipelago. Superoxide is the short-lived primary photochemical product of colored dissolved organic matter (CDOM) photolysis and also reacts with CDOM or trace metals (Cu, Fe) to form H 2 O 2. In the present work we focused our investigations on reactions between CDOM and superoxide. O 2 − decay kinetics experiments were performed by adding KO 2 to diethylenetriaminepentaacetic acid (DTPA) amended seawater and utilizing an established chemiluminescence technique for the detection of O 2 − at nM levels. In Cape Verdean waters we found a significant reactivity of superoxide with CDOM with maximal rates adjacent to the chlorophyll maximum, presumably from production of new CDOM from bacteria/phytoplankton. This work highlights a poorly understood process which impacts on the biogeochemical cycling of CDOM and trace metals in the open ocean.
Photogeneration and interactive reactions of three reactive species in the Seto Inland Sea, Japan
Environmental Chemistry, 2018
Environmental contextPhotogenerated reactive species play important roles in the degradation of dissolved organic pollutants. Photogeneration and concerted measurements of hydroxyl (·OH), nitric oxide (NO·) and superoxide (O2·−) radicals in samples from the Seto Inland Sea suggest that their interactive reactions could yield peroxynitrite (ONOO−), a secondary reactive species. These results reveal how discrete photochemical reactions synergise to influence the variety and fates of reactive species in a marine environment. Photochemically generated reactive species are involved in photodegradation of dissolved organic pollutants in natural waters. However, there is a dearth of empirical evidence, from each batch of water samples collected, to predict the influence of interactive reactions among several photogenerated reactive species on their variety and fates in natural waters. Concerted photogeneration and measurement of hydroxyl (·OH), nitric oxide (NO·) and superoxide (O2·−) radi...
Marine Pollution Bulletin, 1998
The main aim of this study was to assess the hydrogen peroxide (HP) production rates (HPPR) related to anthropogenic pollution in coastal waters by laboratory and field experiments. HPPR's were assessed by simultaneous measurements of HP concentrations, cumulative solar UV irradiation and dissolved organic matter (DOM) fluorescence in the seawater samples at clean and polluted sites in the Mediterranean, Red and the Baltic Seas. The natural HP concentrations at all sites (8-100nM) fall within the normal range recorded elsewhere, and follows a diurnal pattern. The polluted stations in the Mediterranean and Baltic Seas showed higher HPPR (3.2-16.6 nM m 2 W -1 h -l) than the clean stations, while in the Red Sea no significant differences were found because the station that was considered a priori polluted was actually rather clean (2-3 nM m 2 W-1 h-l). Laboratory experiments demonstrated that HPPR was positively linearly correlated to DOM fluorescence, however, this relationship was not found in the natural seawater samples examined in the field. The lack of relationship between HPPR and DOM in the field was attributed to enzymatic breakdown of HP as observed in dark decay experiments. HP dark decay rates were highest in polluted stations, probably due to larger bacterioplankton populations in these samples. Moreover, the HP dark decay rates were much lower in filtered than in non-filtered samples. Sun incubation of filtered (0.2 gm) seawater samples were performed to assess whether elimination of particles would yield higher HPPRs than in non-filtered samples. In the Baltic Sea (low UV irradiation) HPPR was higher in the filtered samples, while at sites with relatively high UV irradiation (Mediterranean and Red Seas), filtration of seawater did not stimulate HPPRs, probably due to UV-damage to 994 planktonic microorganisms.
Journal of Geophysical Research, 2004
1] The National Aeronautics and Space Administration's Global Tropospheric Experiment program has conducted five sampling programs examining the Pacific troposphere from 1991 to 2001. Flights on two aircraft, a P3-B and DC-8, sampled the Pacific troposphere at altitudes from 0.5 km to 13 km and from 130°E to 115°W and from 65°N to 70°S. Long-term trends in the observed species mixing ratios in different geographic regions are presented. Changes in species mixing ratios are discussed with respect to changes in source, transport, and photochemical production and loss processes over the decade study period. CH 4 and CO 2 exhibited average annual mixing ratio increases of 6.39 ppbv yr À1 and 1.92 ppmv yr À1 , respectively. O 3 , CO, and NO all exhibit significantly higher mixing ratios in the north Pacific troposphere in the spring than in the fall. However, there is no clear annual trend for these species. H 2 O 2 mixing ratios were 38 ± 16% higher (D(fall-spring) 258 ± 34 pptv), and CH 3 OOH was 61 ± 15% higher (D343 ± 76 pptv) throughout the Pacific troposphere in the fall than in the spring. During 2001, SO 2 loading in the North Pacific is 2-3 times larger than during earlier years. Anthropogenic tracer gases, C 2 H 6 , C 3 H 8 , C 2 H 2 , and C 2 Cl 4 , do not exhibit comparable increases in their average mixing ratios during the decade study period. CH 3 I, a tracer for oceanic emission, also does not exhibit an increase in 2001. Sulfur loading characterized by SO 2 also does not exhibit a clear annual trend. The enhanced sulfur loading during 2001 appears to have resulted in a suppression of H 2 O 2 mixing ratios in the lower troposphere throughout the midlatitude North Pacific. ), Long-term and seasonal variations in the levels of hydrogen peroxide, methylhydroperoxide, and selected compounds over the Pacific Ocean,