Rapid deposition of oxidized biogenic compounds to a temperate forest
Rapid deposition of oxidized biogenic compounds to a temperate forest
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DOI：
10.1073/pnas.1418702112
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发表时间：
2015-02-03
影响因子：
11.1
通讯作者：
Wennberg, Paul O.
中科院分区：
文献类型：
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作者：
Nguyen, Tran B.;Crounse, John D.;Wennberg, Paul O.
我们报告的通量和干沉降速度为16个以上的美国东南部森林，包括：过氧化氢（H2 O2），硝酸（HNO 3），氰化氢（HCN），羟甲基过氧化氢，过氧乙酸，有机羟基硝酸盐，和其他多功能物种的异戊二烯和单萜的氧化。这些数据表明，干沉降是占主导地位的白天小，饱和含氧化合物汇。大于6重量%的碳排放的异戊二烯的森林返回干沉积其氧化产物。过氧化物占氧化剂通量的很大一部分，可能使更原始地区的臭氧黯然失色。测得的有机硝酸盐包括相当大的一部分（15%）的氧化氮输入到冠层，与HNO 3组成的平衡。我们观察到水溶性化合物（例如，强酸和氢过氧化物）具有低表面电阻的存款而具有中等溶解度的化合物（例如，有机硝酸盐和羟基羰基化合物）或溶解性差（例如，HCN）在植物表面表现出减少的吸收。水溶性化合物的相对沉积速度受其分子扩散系数的一级约束。从阻力模型，我们推断在冠层水平（类似于1 nmol m（-2）.s（-1））的甲酸的排放通量。GEOS-Chem是一个广泛使用的大气化学传输模型，目前低估了这项工作中研究的大多数分子的干沉降。对GEOS-Chem沉积速度进行观测，导致模拟的痕量气体表面浓度降低了45%。
We report fluxes and dry deposition velocities for 16 atmospheric compounds above a southeastern United States forest, including: hydrogen peroxide (H2O2), nitric acid (HNO3), hydrogen cyanide (HCN), hydroxymethyl hydroperoxide, peroxyacetic acid, organic hydroxy nitrates, and other multifunctional species derived from the oxidation of isoprene and monoterpenes. The data suggest that dry deposition is the dominant daytime sink for small, saturated oxygenates. Greater than 6 wt %C emitted as isoprene by the forest was returned by dry deposition of its oxidized products. Peroxides account for a large fraction of the oxidant flux, possibly eclipsing ozone in more pristine regions. The measured organic nitrates comprise a sizable portion (15%) of the oxidized nitrogen input into the canopy, with HNO3 making up the balance. We observe that water-soluble compounds (e.g., strong acids and hydroperoxides) deposit with low surface resistance whereas compounds with moderate solubility (e.g., organic nitrates and hydroxycarbonyls) or poor solubility (e.g., HCN) exhibited reduced uptake at the surface of plants. To first order, the relative deposition velocities of water-soluble compounds are constrained by their molecular diffusivity. From resistance modeling, we infer a substantial emission flux of formic acid at the canopy level (similar to 1 nmol m(-2).s(-1)). GEOS-Chem, a widely used atmospheric chemical transport model, currently under-estimates dry deposition for most molecules studied in this work. Reconciling GEOS-Chem deposition velocities with observations resulted in up to a 45% decrease in the simulated surface concentration of trace gases.