日前，最新一期杂志Nature Geoscience刊登了法国和比利时研究人员的一项最新研究成果"Satellite evidence for a large source of formic acid from boreal and tropical forests"，研究人员发现北方森林和热带森林会产生大量甲酸，从而降低这些地区降雨的PH值，带来酸雨污染。
硝酸和硫酸是造成酸雨污染的“元凶”，但偏远地区的酸雨主要由甲酸造成。根据科学家早先的认识，人类活动、森林火灾以及植物的叶子可直接向大气中释放甲酸，此外，有机物的光化学降解也会产生这种物质。
法国和比利时研究人员发现，全球森林每年可制造近1亿吨甲酸，比已知的甲酸产生途径多出两到三倍。研究人员根据欧洲航天局和欧洲气象卫星组织的卫星所携红外线大气探测干涉仪发回的数据建立模型，发现全球每年可产生1亿至1.2亿吨甲酸，其中90%经由生物途径产生，而且大部分集中在北方森林和热带森林地区。
该报告说，森林中的松柏植物会释放出一些不稳定的萜类有机化合物，这些有机物在氧化过程中会释放甲酸，从而降低相应地区降雨的PH值。（生物谷Bioon.com）
doi:10.1038/ngeo1354
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Satellite evidence for a large source of formic acid from boreal and tropical forests
T. Stavrakou,J-F. Müller,J. Peeters,A. Razavi,L. Clarisse,C. Clerbaux,P-F. Coheur,D. Hurtmans,M. De Mazière,C. Vigouroux,N. M. Deutscher,D. W. T. Griffith,N. Jones& C. Paton-Walsh
Formic acid contributes significantly to acid rain in remote environments1, 2. Direct sources of formic acid include human activities, biomass burning and plant leaves. Aside from these direct sources, sunlight-induced oxidation of non-methane hydrocarbons (largely of biogenic origin) is probably the largest source3, 4. However, model simulations substantially underpredict atmospheric formic acid levels5, 6, 7, indicating that not all sources have been included in the models. Here, we use satellite measurements of formic acid concentrations to constrain model simulations of the global formic acid budget. According to our simulations, 100–120?Tg of formic acid is produced annually, which is two to three times more than that estimated from known sources. We show that 90% of the formic acid produced is biogenic in origin, and largely sourced from tropical and boreal forests. We suggest that terpenoids—volatile organic compounds released by plants—are the predominant precursors. Model comparisons with independent observations of formic acid strengthen our conclusions, and provide indirect validation for the satellite measurements. Finally, we show that the larger formic acid emissions have a substantial impact on rainwater acidity, especially over boreal forests in the summer, where formic acid reduces pH by 0.25–0.5.
