Daily Archives: April 10, 2016

Global Sea Surface Temperatures Decline

“So far, the responses of global sea surface temperatures to the 2015/16 El Niño have fallen short of those experienced during the 1997/98 El Niño. See Figure 2. There has also been a recent downtick in many basins that did not occur in 1997/98. I wouldn’t take those downticks as indicators of things to come, though.  The 2015/16 El Niño released a tremendous about of warm water from below the surface of the western tropical Pacific, and all of that warm water is going to end up somewhere.” click here for a detailed discussion by Bob Tisdale.

Salicylic Acid Transformation via Ozonation

Hu R, Zhang L, Hu J. Study on the kinetics and transformation products of salicylic acid in water via ozonationChemosphere. 2016 Mar 28;153:394-404. doi: 10.1016/j.chemosphere.2016.03.074.

As salicylic acid is one of widely used pharmaceuticals, its residue has been found in various environmental water systems e.g. wastewater, surface water, treated water and drinking water. It has been reported that salicylic acid can be efficiently removed by advanced oxidation processes, but there are few studies on its transformation products and ozonation mechanisms during ozonation process. The objective of this study is to characterize the transformation products, investigate the degradation mechanisms at different pH, and propose the ozonation pathways of salicylic acid. The results showed that the rate of degradation was about 10 times higher at acidic condition than that at alkaline condition in the first 1 min when 1 mg L-1 of ozone solution was added into 1 mg L-1 of salicylic acid solution. It was proposed that ozone direct oxidation mechanism dominates at acidic condition, while indirect OH radical mechanism dominates at alkaline condition. A two stages pseudo-first order reaction was proposed at different pH conditions. Various hydroxylation products, carbonyl compounds and carboxylic acids, such as 2,5-dihydroxylbenzoic acid, 2,3-dihydroxylbenzoic acid, catechol, formaldehyde, glyoxal, acetaldehyde, maleic acid, acetic acid and oxalic acid etc. were identified as ozonation transformation products. In addition, acrylic acid was identified, for the first time, as ozonation transformation products through high resolution liquid chromatography-time of flight mass spectrometer. The information demonstrated in this study will help us to better understand the possible effects of ozonation products on the water quality. The degradation pathways of salicylic acid by ozonation in water sample were proposed. As both O3 and OH radical were important in the reactions, the degradation pathways of salicylic acid by ozonation in water sample were proposed at acidic and basic conditions. To our knowledge, there was no integrated study reported on the ozonation of salicylic acid in water, in terms of transformation products, kinetic, mechanism, as well as degradation pathways.