Chiwa Masaaki, Miyake Takayuki, Kimura Nobuhito, Sakugawa Hiroshi
Kyushu University Forest, Kyushu Univ., 394 Tsubakuro, Sasaguri 811-2415, Japan.
J Environ Qual. 2008 Oct 23;37(6):2397-402. doi: 10.2134/jeq2007.0559. Print 2008 Nov-Dec.
We analyzed low molecular weight organic acids and aldehydes in throughfall under pine forest, and organic acids in dew on chemically inert surfaces and pine needle surfaces at urban- and mountain-facing sites of pine forest in western Japan. Low molecular weight organic acids and aldehydes accounted for less than 5% of the dissolved organic carbon in throughfall at both sites. Formaldehyde at both sites and formate at the mountain-facing site were found at significantly lower concentrations in throughfall than in rainfall, which may be explained by the degradation and/or retention of these components by the pine canopy as the incident precipitation passed through it. The oxalate concentration in throughfall was significantly higher than those in rainfall at both sites, suggesting that oxalate was derived from leaching from the pine foliage. At both sites, organic acid concentrations were higher in dew on the pine needles than in throughfall or dew on chemically inert surfaces. This could be due to the long contact time of dew on pine needles, during which leached substances from pine needles and dry deposits accumulated on their surfaces can dissolve into the small volume of dew. The role of enhanced concentrations of oxalate in an aqueous phase on the plant surfaces (e.g., dew) is discussed in relation to hydroxyl radical formation via the photo-Fenton reaction.
我们分析了日本西部松林穿透雨中的低分子量有机酸和醛类，以及在城市和山区松林的化学惰性表面和松针表面露水中的有机酸。在两个地点，低分子量有机酸和醛类在穿透雨中占溶解有机碳的比例均不到5%。两个地点穿透雨中的甲醛以及山区穿透雨中的甲酸盐浓度均显著低于降雨中的浓度，这可能是由于入射降水穿过松冠层时这些成分发生了降解和/或滞留。两个地点穿透雨中的草酸盐浓度均显著高于降雨中的浓度，这表明草酸盐来源于松树叶的淋溶。在两个地点，松针上露水的有机酸浓度均高于穿透雨或化学惰性表面上的露水。这可能是由于露水在松针上的接触时间长，在此期间，从松针上淋溶下来的物质以及沉积在其表面的干沉降物会溶解到少量的露水中。本文结合通过光芬顿反应形成羟基自由基，讨论了植物表面（如露水）水相中草酸盐浓度升高的作用。
