Effect of Natural and Artificial Light on Fe(III) Organic Complexes Photolysis: Case of Fe (III)-Malonate and Fe(III)-Malate

The photolysis of iron(III) organic complexes in the presence of natural and simulated light was a concern for the role it plays within the environment in terms of producing hydroxyl radicals able to degrade organic products. In the present work, the study focused on two iron(III) organic complexes. The characterization of these complexes by spectrometry allowed to show their stability in environment with a stability constant equal to Log β = 13.13 for the complex Fe(III)-malonate, and Log β = 20.85 for the Fe(III)-malate complex. Photolysis of these complexes was carried out using a lamp at 365 nm at different pHs, and followed by several assay Fe(II), H2O2 and •OH. The complexes present different photo-reactivities, in the case of Fe(III)-malate, the photolysis is favored by the Fenton process and generates hydroxyl radicals, contrarily to Fe(III)-malonate photolysis which generates an oxidizing •CH2COOH radical without formation of H2O2 nor of •OH. The presence of oxygen and the addition of isopropanol and chloroform show different effects on the complex photolysis. Complexes mineralization at natural irradiation was also studied using chemical oxygen demand (COD).

Degradation of atrazine photoinduced by Fe(III)-pyruvate complexes in the aqueous solution

The composition and photochemical properties of the Fe(III)-Pyr complexes in the aqueous solution was studied in this work. Fe(III) was complexed by Pyr in the ratio of 1:3. The photochemical processes occurred in the Fe(III)-Pyr system was studied in detail. Fe(II) was the main intermediate product. DMPO was used as scavenger to determine the active radicals, such as *OH, CO3*-, CO2*-, H and RCO2* by ESR. Photodegradation of atrazine induced by the photolysis of Fe(III)-Pyr was studied and the reaction kinetics fitted the first order reaction. Parameters such as pH, the initial concentrations of Fe(III), pyruvate (Pyr) and atrazine were all investigated. Photoproducts were detected by the LC-MS and the photodegradation scheme was proposed. *OH radical was the main pathway of atrazine degradation.

Measurements of atmospheric carboxylic acids and carbonyl compounds in São Paulo City, Brazil

Winter atmospheric measurements of gaseous lower carbonyl and carboxylic acids were carried out simultaneously (in 1999) at two distinct urban sites located in the city of São Paulo, Brazil. The greater metropolitan area of São Paulo is the largest industrialized region of Latin America and has a highly polluted atmosphere. It has an unconventional mix of vehicle types in that a variety of gasoline blends, including oxygenated ones, are used. Mixing ratios of formic and acetic acids ranged, respectively, from 0.6 to 19.4 and from 0.1 to 10.6 ppbv in one of the sites studied and from 1.4 to 18.4 and from 0.4 to 6.7 ppbv in the other site. High values of formic to acetic ratios were found, especially in the latter site (average = 4.3), suggesting that photochemical production was the predominant source of the formic and acetic acid during the afternoon. Differing from the acids, levels of carbonyls were similar at both sites. Higher average mixing ratios of acetaldehyde and formaldehyde were found in the morning (18.9 and 17.2 ppbv) and gradually decreased from midday (9.5 and 11.8 ppbv) to evening (7.2 and 10.2 ppbv). In the morning, vehicular direct emission seemed to be the main primary source of formaldehyde and acetaldehyde, whereas at midday and evening these compounds appeared to be mainly formed by photochemistry. Secondary photochemical production of organic acids and aldehydes (rather than primary emissions from vehicles) was shown to be more important in São Paulo's atmosphere from midday to evening, particularly on days with strong solar radiation.