Nitrate leaching and its implication for Fe and As mobility in a Southeast Asian aquifer.

The drinking water quality in Southeast Asia is at risk due to arsenic (As) groundwater contamination. Intensive use of fertilizers may lead to nitrate (NO3-) leaching into aquifers, yet very little is known about its effect on iron (Fe) and As mobility in water. We ran a set of microcosm experiments using aquifer sediment from Vietnam supplemented with 15NO3- and 13CH4. To assess the effect of nitrate-dependent anaerobic methane oxidation (N-DAMO) we also inoculated the sediment with two different N-DAMO enrichment cultures. We found that native microorganisms and both N-DAMO enrichments could efficiently consume all NO3- in 5 days. However, CH4 oxidation was observed only in the inoculated microcosms, suggesting that the native microbial community did not perform N-DAMO. In uninoculated microcosms, NO3- was preferentially used over Fe(III) as an electron acceptor and consequently inhibited Fe(III) reduction and As mobilization. The addition of N-DAMO enrichment cultures led to Fe(III) reduction and stimulated As and Mn release into the water. The archaeal community in all treatments was dominated by Ca. Methanoperedens while the bacterial community consisted of various denitrifiers. Our results suggest that input of N fertilizers to the aquifer decreases As mobility and that CH4 cannot serve as an electron donor for NO3- reduction.

Effect of hyperbaric oxygen therapy on blood pressure in patients undergoing treatment.

INTRODUCTION: Hyperbaric oxygen (HBO2) therapy is generally safe and well tolerated. However, known side effects do exist. Elevation in the blood pressure of patients undergoing HBO2 therapy is a less defined potential side effect. We sought to better quantify effects of HBO2 on blood pressure (BP) in patients undergoing HBO2. METHODS: A retrospective chart review was performed on quality assurance data captured on all patients undergoing HBO2 between March 2012 and October 2015 at a large tertiary referral university hospital hyperbaric center. RESULTS: We identified 155 patients who received 3,147 hyperbaric oxygen treatments. For all treatments there was an overall increase in the median systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) following treatment. No statistically significant difference was found when comparing patients with and without hypertension. Calcium channel blockers (CCB) and beta-blockers (BB) were found to have an agonizing effect while ACE inhibitors (ACEI) were found to have a protective effect. The change in SBP was less with each additional treatment in patients undergoing more than one treatment. DISCUSSION: The current study demonstrates that absolute rises in blood pressure do occur as a result of HBO2 therapy. However, the extent of this effect is not large. BB and CCB had agonizing effects while ACEI had a protective effect. Finally, there was a protective effect with more treatments.