Atmospheric processing outside clouds increases soluble iron in mineral dust.
Atmospheric processing outside clouds increases soluble iron in mineral dust.
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DOI：
10.1021/es504623x
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发表时间：
2015-01
影响因子：
11.4
通讯作者：
Zongbo Shi;M. Krom;S. Bonneville;L. Benning
中科院分区：
文献类型：
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作者：
Zongbo Shi;M. Krom;S. Bonneville;L. Benning
铁(Fe)是调节全球海洋许多地区初级生产力的一种关键微量营养素。尘埃沉积是表层海洋铁的重要来源，但其中大部分铁在生物上是不可利用的。大气处理和重新加工尘埃气溶胶中的铁可以增加向海洋的生物可利用铁的输入，但其过程尚不清楚。在这里，我们对含铁尘埃在湿气溶胶和云滴之间的循环进行了实验模拟和模拟。我们的结果表明，在与湿气溶胶相关的酸性条件下，不溶性铁在尘埃颗粒中很容易溶解。相比之下，在通常与云相关的较高pH条件下，铁的溶解倾向于停止，溶解的铁以结晶较差的纳米颗粒的形式沉淀。如果含尘云滴再次蒸发(回到低pH的湿气溶胶阶段)，新形成的铁纳米颗粒迅速重新溶解，而难熔的含铁相继续逐渐溶解。总体而言，酸性、潮湿的气溶胶阶段的持续时间最终会增加向海洋输送的潜在生物可利用铁的量，而云中的条件有利于大气中富铁纳米颗粒的形成。
Iron (Fe) is a key micronutrient regulating primary productivity in many parts of the global ocean. Dust deposition is an important source of Fe to the surface ocean, but most of this Fe is biologically unavailable. Atmospheric processing and reworking of Fe in dust aerosol can increase the bioavailable Fe inputs to the ocean, yet the processes are not well understood. Here, we experimentally simulate and model the cycling of Fe-bearing dust between wet aerosol and cloud droplets. Our results show that insoluble Fe in dust particles readily dissolves under acidic conditions relevant to wet aerosols. By contrast, under the higher pH conditions generally relevant to clouds, Fe dissolution tends to stop, and dissolved Fe precipitates as poorly crystalline nanoparticles. If the dust-bearing cloud droplets evaporated again (returning to the wet aerosol stage with low pH), those neo-formed Fe nanoparticles quickly redissolve, while the refractory Fe-bearing phases continue to dissolve gradually. Overall, the duration of the acidic, wet aerosol stage ultimately increases the amount of potentially bioavailable Fe delivered to oceans, while conditions in clouds favor the formation of Fe-rich nanoparticles in the atmosphere.