pH- and Temperature-Dependent Kinetics of the Oxidation Reactions of OH with Succinic and Pimelic Acid in Aqueous Solution

Rate constants for the aqueous-phase reactions of the hydroxyl radical with the dicarboxylic acids, succinic acid and pimelic acid were determined using the relative rate technique over the temperature range 287 K ≤ T ≤ 318 K and at pH = 2.0, 4.6 or 4.9 and 8.0. OH radicals were generated by H2O2 laser flash photolysis while thiocyanate was used as a competitor. The pH values were adjusted to obtain the different speciation of the dicarboxylic acids. The following Arrhenius expressions were determined (in units of L mol-1 s-1): succinic acid, k(T, AH2) (2.1 x 0.1) ± 1010 exp[(-1530 x 250 K)/T], k(T, AH-) (1.8 x 0.1) ± 1010 exp[(-1070 x 370 K)/T], k(T, A2-) (2.9 x 0.2) ± 1011 exp[(-1830 x 350 K)/T] and pimelic acid, k(T, AH2) (7.3 x 0.2) ± 1010 exp[(-1040 x 140 K)/T], k(T, AH-) (1.8 x 0.1) ± 1011 exp[(-1200 x 240 K)/T], k(T, A2-) (1.4 x 0.1) ± 1012 exp[(-1830 x 110 K)/T]. A general OH radical reactivity trend for dicarboxylic acids was found as k(AH2) < k(AH-) < k(A2-). By using the pH and temperature dependent rate constants, source and sinking processes in the tropospheric aqueous phase can be described precisely. © 2020 by the authors

Physical oceanography during POSEIDON cruise POS501 in Madeira basin in June 2016

During the cruise POS501 on board the German R/V Poseidon, we measured temperature, salinity, dissolved oxygen, fluorescence, and turbidity on 35 stations in the Madeira Basin, Northeast Atlantic in June 2016. We aimed to study the physical and biogeochemical conditions in the upper 2000 m of the water column in the catchment area of Kiel 276. The CTD stations are distributed along three meridians (23°W, 22°W, 21°W, and 20°W) and between 30° and 37°N to locate the Azores Front. The dissolved oxygen data is noisy below 1700 m Since there was no measurement of dissolved oxygen (Winkler titration) during the cruise, the data cannot be calibrated

Biological and chemical water properties measured during POSEIDON cruise POS501 in Madeira basin in June 2016

During the cruise POS501 on board the German R/V Poseidon, we collected water with a CTD SBE9plus equipped with 14 Hydrobios free flow bottles of 5 L each in 24 stations (resulting in more than 300 samples) and during transect time in the Madeira basin region, Northeast Atlantic. We aimed to study the physical and biogeochemical conditions in the upper 2000 m of the water column around the catchment area of Kiel 276 in June 2016. We measured concentrations of chlorophyll a, phaeopigments, suspended particulate material (SPM) and nutrients as nitrate, nitrite, phosphate and silicate. Also, we determined concentrations of particulate organic carbon (POC) and particulate organic nitrogen (PON) as well as dissolved organic carbon (DOC) and dissolved nitrogen (DN). The physical oceanography during the survey is available at PANGAEA (https://doi.org/10.1594/PANGAEA.949134). Brief description of the methodology used: - Nitrate, nitrite, phosphate and silicate were measured by continuous flow analysis. - Oxygen was measured on one sample at each station by potentiometric Winkler titration. - DOC and DN were measured by catalytic oxidation after filtered with GF/F-filters. - POC and PON were measured by means of an elemental analyser after filtered with pre-combusted GF/F-filters. - Suspended particulate material (SPM) was determined gravimetrically after pre-combusted and weighted GF/F-filters filtration. - Chlorophyll a and phaeopigments were measured using a fluorometer after ethanol extraction of the GF/F-filters