Acetic acid, oxo-, sodium salt, reaction products with ethylenediamine and hydroxybenzenesulfonic acid monosodium salt, iron sodium salts

Phototransformation in water

Description of key information

Fe(Na)EDDHMA, phototransformation in water, OECD Draft Guideline: DT50: 40.66 and 35.4 hours for the two major components at 25 +/- 3 °C and a light intensity of 4.86E20 photons/second in the wavelength range of 290 - 500 nm.
EDDHA/Fe3+, photostability in water and impact on soybean growth by the degradation products: The chelate was progressively degraded along the 30 day period when it was exposed to direct sunlight. The degradation products did not affect biomass production of soybean plants.

Additional information

The degradation of the read-across substance Fe(Na)EDDHMA (for further information, please refer to the separate read-across statement) in water as a result of direct photo-transformation (photolysis) was investigated according to the OECD Draft Guidance document: "Direct Phototransformation of Chemicals in water". Chemical analysis of Fe(Na)EDDHMA resulted in 4 peaks: 2 major peaks at approximately t = 6.5 and t = 19.9 minutes, respectively and two minor peaks at approximately t = 5.5 and t = 18.9 minutes, respectively. So probably, the test substance consists of at least 4 components. For practical reasons, the photochemic degradation of the 2 major components (component A and B) was determined.The half-life time for phototransformation of Fe(Na)EDDHMA at 25 +/- 3 °C is determined to be 40.66 and 35.4 hours for the two major compartments of this UVCB substance, at a light intensity of 4.86E20 photons/second in the wavelength range of 290 - 500 nm.

Supporting information is given by Hernández-Apaolaza and Lucena (2010), who evaluated the impact of sunlight exposure and how the concentration of Ethylenediamine-N,N´-bis(2-hydroxyphenylacetic) acid (EDDHA/Fe3 +) influences the photostability of the chelate at constant pH (pH 7). In the second part of the experimental procedure, the effects of the photodegradation products (Salicylaldehide, salicyclic acid and Salicylaldehyde ethylenediamine diimineon) on soybean growth was investigated. Test concentrations of 0.18, 0.89, 1.79, 8.90 and 17.9 mmol/L (three replicates each) were exposed to sunlight and controls were maintained in the dark. Samples were taken at exposure Days 0, 1, 3, 7, 15 and 30 and analysed by High Performance Liquid Chromatography (HPLC). Sun radiation measurements with a lightmeter were performed as well.

The chelate was progressively degraded along the 30 day period when it was exposed to direct sunlight. Only 33.7 % remained in solution. Most of the photodecomposition was observed during the first 7 days (38 %); another 10.7 % of decomposition was obtained after 8 days and after 30 days, an additional 17.7 % degradation was recorded. In darkness, almost 100 % of the chelate was recovered in solution after 30 days. The iron chelate was found to be more stable at high pH than at low pH values. When the chelate was stored in the dark, only two chromatographic peaks were obtained in the HPLC: one for the racemic isomer and another for the meso isomer of ortho,ortho-EDDHA/Fe3+. Approximately 50 % of the total amout was the racemic isomer, the other 50 % were the meso isomer. When the chelate was exposed to sunlight, the peak areas of both meso and racemic isomers were lower and a third peak appeared; possibly related to the photodecomposition products formed. Salicylaldehide, salicyclic acid and Salicylaldehyde ethylenediamine diimine peaks were also identified. At low chelate concentrations, the degradation increased as sunlight exposure time increased. The EDDHA/Fe3+ photodecomposition was highly correlated with the concentration exposed. Perhaps, at high concentrations, the chelate molecule could act as a screen, thus protecting the remainder of the chelate from photodecomposition.

In order to investigate the impact of the photodegradation products on soybean (Glycine maxL. cv. Oshumi) growth, different treatment groups were applied to 6-day old plants and were grown for further 14 days. Afterwards, Salicyladehide, salicyclic acid and Salicylaldehydeethylenediamine diimine were introduced. SPAD (Soil Plant Analysis Development) readings were performed during the experiment with a chlorophyll meter. The treatment groups were as followed:

T1) 5 µmol/L o,o-EDDHA/Fe3+ (dark)

T2) 5 µmol/L o,o-EDDHA/Fe3+ (light)

T3) 5 µmol/L o,o-EDDHA/Fe3+ + 2.5 µmol/L salicyclic acid (dark)

T4) 5 µmol/L o,o-EDDHA/Fe3+ + 2.5 µmol/L Salicyaldehyde ethylenediamine diimine (dark)

T5) 5 µmol/L o,o-EDDHA/Fe3+ + 2.5 µmol/L salicylaldehide (dark)

After further pretreatment, the plant material was dried at 70 °C. Concentrations of Zn, Mn, Cu and Fe in dried plant material samples were measured by atomic absorption spectrometry (ASS).

No significant differences in micronutrient concentration in leaves were observed between plants grown in a nutrient solution protected or unprotected from light. Plants treated with a mixture of EDDHA/Fe3+ and salicylic acid showed a significantly lower amount of iron in leaves than plants without salicylic acid addition and not exposed to light. The photodecomposition products did not affect biomass production since no biomass reduction was observed.