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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Heterogeneous Freezing of Aqueous Particles Induced by Crystallized (NH_4)_2SO_4, Ice, and Letovicite
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Heterogeneous Freezing of Aqueous Particles Induced by Crystallized (NH_4)_2SO_4, Ice, and Letovicite

机译：结晶（NH_4）_2SO_4，冰和Letovicite引起的水颗粒的非均质冻结

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摘要

Heterogeneous freezing of aqueous particles with solid inclusions of crystallized (NH_4)_2SO_4, ice, and letovicite were studied using optical microscopy and differential scanning calorimetry. For (NH_4)_2SO_4-H_2O particles, the heterogeneous freezing temperature was found to be dependent on the morphology of the (NH_4)_2SO_4 solid. If the crystallized solid was in the form of microcrystals, the heterogeneous ice-freezing temperature was close to the eutectic temperature and the critical saturation with respect to ice was close to 1. However, if the solid was in the form of one or two large crystals, the heterogeneous freezing temperature was close to the homogeneous freezing temperature. For particles with one or two large (NH_4)_2SO_4 crystals in equilibrium with (NH_4)_2SO_4-H_2O solution, we have estimated an upper limit of 1.5 x 10~(-5) s~(-1) #mu#m~(-2) for J_(het) (heterogeneous nucleation rate of ice, immersion freezing mode). Our results for NH_4HSO_4-H_2O particles show that when one or two large crystals of either ice or letovicite are present in the solution, the freezing temperature does not deviate significantly from the homogeneous freezing temperature, consistent with the (NH_4)_2SO_4-H_2O experiments. Our work shows that the surface area and surface microstructure of crystalline solids present in aqueous aerosols can significantly change the heterogeneous freezing temperature and critical ice saturations and that heterogeneous ice nucleation induced by crystalline salts may be very important in the formation of upper tropospheric clouds.
机译：使用光学显微镜和差示扫描量热法研究了具有结晶的（NH_4）_2SO_4，冰和锂云母的固体包裹体的水性颗粒的非均质冻结。对于（NH_4）_2SO_4-H_2O颗粒，发现异质冻结温度取决于（NH_4）_2SO_4固体的形态。如果结晶的固体为微晶形式，则非均质的冰冻温度接近共晶温度，相对于冰的临界饱和度接近1。但是，如果固体为一或两个大的形式对于晶体，非均质冷冻温度接近均质冷冻温度。对于具有（NH_4）_2SO_4-H_2O溶液平衡的一个或两个大（NH_4）_2SO_4晶体的粒子，我们估计其上限为1.5 x 10〜（-5）s〜（-1）＃mu＃m〜（ -2）表示J_（het）（冰的非均相成核速率，浸没冷冻模式）。我们对NH_4HSO_4-H_2O颗粒的研究结果表明，当溶液中存在一个或两个冰或白云母的大晶体时，冷冻温度与均质冷冻温度没有明显偏离，这与（NH_4）_2SO_4-H_2O实验一致。我们的工作表明，存在于水性气溶胶中的结晶固体的表面积和表面微观结构可以显着改变非均质的冻结温度和临界冰饱和度，并且由结晶盐诱导的非均质冰核化在对流层上层云的形成中可能非常重要。

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