Direct Observation of the Photodegradation of Anthracene and Pyrene Adsorbed onto Mangrove Leaves

Abstract

An established synchronous fluorimetry method was used for in situ investigation of the photodegradation of pyrene (PYR) and anthracene (ANT) adsorbed onto fresh leaves of the seedlings of two mangrove species, Aegiceras corniculatum (L.) Blanco (Ac) and Kandelia obovata (Ko) in multicomponent mixtures (mixture of the ANT and PYR). Experimental results indicated that photodegradation was the main transformation pathway for both ANT and PYR in multicomponent mixtures. The amount of the PAHs volatilizing from the leaf surfaces and entering the inner leaf tissues was negligible. Over a certain period of irradiation time, the photodegradation of both PYR and ANT adsorbed onto the leaves of Ac and Ko followed first-order kinetics, with faster rates being observed on Ac leaves. In addition, the photodegradation rate of PYR on the leaves of the mangrove species in multicomponent mixtures was much slower than that of adsorbed ANT. Compared with the PAHs adsorbed as single component, the photodegradation rate of ANT adsorbed in multicomponent mixtures was slower, while that of PYR was faster. Moreover, the photodegradation of PYR and ANT dissolved in water in multicomponent mixtures was investigated for comparison. The photodegradation rate on leaves was much slower than in water. Therefore, the physical-chemical properties of the substrate may strongly influence the photodegradation rate of adsorbed PAHs.

Organic Composition, Chemistry, and Photochemistry of Urban Film in Leipzig, Germany

“…Since PAH have been shown to undergo photolysis on a variety of laboratory and environmental surfaces, including silica and alumina, soot, fly ash, , and vegetation, , we hypothesized that the PAH abundance profile in light-exposed urban film samples would differ from that in samples grown under dark conditions.…”

The Chemical Landscape of Leaf Surfaces and Its Interaction with the Atmosphere

“…Although there is compelling evidence for the presence of exogenous substances onto plant leaves, information on their multiphase reactivity is scarce and biased toward anthropogenic compounds. To the best of our knowledge, leaf-surface photodegradation of pesticides is the only process that has been investigated in detail (reviewed by Sleiman et al and others , )although primarily in laboratory settings using model surfaces or reconstructed cuticles. ,, Some work has also been performed on the photodegradation of PAHs and their oxidation products on and within leaf cuticles, − while other studies investigated HNO 3 /nitrate photolysis on leaves of various plants. , On the contrary, the reactivity of anthropogenic SVOCs adsorbed on leaves with other gas-phase oxidants has received considerably less attention . An early investigation reported the oxidation of parathion (a pesticide) adsorbed onto lemon tree leaves in the presence of ozone and “foliar dust” (soil organic matter particles) .…”

In situ simultaneous investigation of the transport of phenanthrene and fluoranthene adsorbed onto the root surfaces to tissues of mangrove seedlings

“…17,18 However, these methods cannot be used to investigate the original form of the PAHs adsorbed onto the root surface or those entering the root tissues because these methods destroy the original form of the PAHs in the root. 24,25 Different from the weak autouorescence signal of the leaf surface, the mangrove root surface emits a relatively strong background uorescence signal. 19 In addition, some other methods for the determination of PAHs, such as Fourier transform infrared (FTIR) and UV-vis methods, that have no pre-treatment procedure can only qualitatively analyse the PAHs due to the limitations of the instruments.…”

“…Then, in order to overcome the drawback, synchronous SSF and emission ber-optic uorimetry (FOF) methods were established. 24,25 Different from the weak autouorescence signal of the leaf surface, the mangrove root surface emits a relatively strong background uorescence signal. 26,27 Therefore, the established methods described above can hardly realize in situ determination of PAHs adsorbed onto the root surface.…”