Electrochemical concentration cell ozone soundings at two sites during the Stratospheric Ozone Intercomparison Campaign

Abstract

The Stratospheric Ozone Intercomparison Campaign (STOIC) was designed to compare proposed instruments for the Network for the Detection of Stratospheric Change (NDSC) with established measurement techniques. Ground‐based measurements were conducted at Table Mountain, California (34.4°N, 117.7°W), and rocket profiles were made at San Nicolas Island, California (33.3°N, 119.5°W). In an effort to estimate site‐to‐site differences during the intercomparison, daily soundings were made with balloon‐borne electrochemical concentration cell (ECC) ozonesondes at the two sites. Comparisons have been made of the mean values for the soundings at each site. The soundings showed small temperature differences between the two sites with the nighttime Table Mountain measurements up to 2°K cooler than the daytime San Nicolas Island temperatures. Day/night temperature corrections based on the emissivity and absorptivity of the thermistors in the balloon instruments can account for these apparent temperature differences. Ozone partial pressure profiles from the ECCs have been used to estimate atmospheric ozone variability during STOIC. Above 20 km, the lowest altitude for the STOIC comparisons, the average data sets from both sites showed standard deviations that were at or below the estimated 5–6% profile‐to‐profile repeatability for the ozonesondes. This indicates that atmospheric ozone variability was only of the order of a few percent above 20 km during the 2 weeks of the STOIC campaign. Above 20 km the ozone partial pressures over the Table Mountain site averaged 2.0% lower than over San Nicolas Island.

Role of Near-Electrode Solution Chemistry on Bacteria Attachment and Poration at Low Applied Potentials

“…Bacteria poration at low potentials has previously been attributed to ROS and Cl 2 production. , Under cathodic polarization conditions, the formation of H 2 O 2 and O 2 •– is possible according to reactions and , respectively In addition, ROS can form under anodic conditions (i.e., OH • , H 2 O 2 , and O 3 ) according to the following overall redox reactions ,− The SECM experiments were conducted to determine the production of ROS under the anodic and cathodic potentials of the poration experiments using a 100 mM NaClO 4 electrolyte to prevent the formation of Cl-based oxidants. To determine the anodic formation rate of ROS on the BDD MEA, the SECM experiment was conducted in a substrate generation tip collection (SG-TC) mode directly above a single 20 μm diameter microelectrode.…”