On the photochemical production of new particles in the coastal boundary layer
On the photochemical production of new particles in the coastal boundary layer
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DOI：
10.1029/1999gl900335
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发表时间：
1999-06
影响因子：
5.2
通讯作者：
C. O’Dowd;G. Mcfiggans;D. Creasey;L. Pirjola;C. Hoell;Michael H. Smith;B. Allan;J. Plane
中科院分区：
文献类型：
--
作者：
C. O’Dowd;G. Mcfiggans;D. Creasey;L. Pirjola;C. Hoell;Michael H. Smith;B. Allan;J. Plane
对沿海环境中超细（r<5 nm）颗粒（UFP）形成、OH 和 SO2 浓度的同时测量进行了检查，以进一步阐明导致潮汐相关的均质异分子成核的过程。在几乎每天的成核事件中，在太阳辐射和低潮条件下，UFP 浓度接近约 300,000 cm−3。 OH 的同时测量表明，这些事件不仅发生在低潮期间，而且发生在 OH 浓度峰值的条件下，表明至少一种成核物质是通过光化学方法产生的。尽管 H2SO4 和 H2O 的二元成核可以排除为一种可能的机制，但衍生的 H2SO4 的产生也表现出与 UFP 形成的显着相干性，尽管存在相位滞后，因此表明它的参与。涉及 NH3 的三元成核似乎最有可能是一种触发机制，然而，至少需要第四种可凝聚物质 X 才能生长到可检测的尺寸。由于 UFP 仅在低潮事件期间观察到，因此认为物种 X 或其母体是从海岸生物群中释放出来的 - 没有它，就不会检测到成核。 X 物种仍有待鉴定。模型模拟表明，为了重现观察结果，需要 107 cm−3 s−1 的成核速率和 5 × 107 cm−3 的可冷凝蒸汽浓度。
Concurrent measurements of ultra‐fine (r<5 nm) particle (UFP) formation, OH and SO2 concentrations in the coastal environment are examined to further elucidate the processes leading to tidal‐related homogeneous heteromolecular nucleation. During almost daily nucleation events, UFP concentration approached ≈300,000 cm−3 under conditions of solar radiation and low tide. Simultaneous measurements of OH illustrate that, as well as occurring during low tide, these events occur during conditions of peak OH concentration, suggesting that at least one of the nucleating species is photochemically produced. Derived H2SO4 production also exhibited remarkable coherence, although phase‐lagged, with UFP formation, thus suggesting its involvement, although binary nucleation of H2SO4 and H2O can be ruled out as a plausible mechanism. Ternary nucleation involving NH3 seems most likely as a trigger mechanism, however, at least a fourth condensable species, X, is required for growth to detectable sizes. Since UFP are only observed during low tide events, it is thought that species X, or it's parent, is emitted from the shore biota ‐ without which, no nucleation is detected. Species X remains to be identified. Model simulations indicate that, in order to reproduce the observations, a nucleation rate of 107 cm−3 s−1, and a condensable vapour concentration of 5 × 107 cm−3, are required.