(Table 1) Characteristics of marine snow and ice samples at Barrow, Alaska@en

We measured light absorption in 42 marine snow, sea ice, seawater, brine, and frost flower samples collected during the OASIS field campaign between February 27 and April 15, 2009. Samples represented multiple sites between landfast ice and open pack ice in coastal areas approximately 5 km west of Barrow, Alaska. The chromophores that are most commonly measured in snow, H2O2, NO3-, and NO2-, on average account for less than 1% of sunlight absorption in our samples. Instead, light absorption is dominated by unidentified \"residual\" species, likely organic compounds. Light absorption coefficients for the frost flowers on first-year sea ice are, on average, 40 times larger than values for terrestrial snow samples at Barrow, suggesting very large rates of photochemical reactions in frost flowers. For our marine samples the calculated rates of sunlight absorption and OH production from known chromophores are (0.1-1.4) x 10**14 (photons/cm**3/s) and (5-70) x 10**-12 (mol/L/s), respectively. Our residual spectra are similar to spectra of marine chromophoric dissolved organic matter (CDOM), suggesting that CDOM is the dominant chromophore in our samples. Based on our light absorption measurements we estimate dissolved organic carbon (DOC) concentrations in Barrow seawater and frost flowers as approximately 130 and 360 µM C, respectively. We expect that CDOM is a major source of OH in our marine samples, and it is likely to have other significant photochemistry as well.本研究于2009年2月27日至4月15日开展的OASIS野外考察（OASIS field campaign）期间，采集了42份样品，涵盖海洋雪（marine snow）、海冰（sea ice）、海水、卤水（brine）与霜花（frost flower），并对其光吸收特性进行了测定。所有样品采集自阿拉斯加巴罗（Barrow）以西约5公里的近岸区域，覆盖固定冰与开阔浮冰群之间的多个采样位点。雪样中最常检测的发色团（chromophore）——过氧化氢（H₂O₂）、硝酸根（NO₃⁻）与亚硝酸根（NO₂⁻）——在本研究样品的太阳光吸收贡献中平均占比不足1%。取而代之的是，未被识别的‘残留’组分（大概率为有机化合物）主导了光吸收过程。一年生海冰（first-year sea ice）上的霜花的光吸收系数，平均而言是巴罗地区陆地雪样的40倍，这表明霜花内的光化学反应速率极高。对于本研究的海洋样品，由已知发色团计算得到的太阳光吸收速率与羟基自由基（OH）生成速率分别为(0.1~1.4)×10¹⁴ 光子/(厘米³·秒)与(5~70)×10⁻¹² 摩尔/(升·秒)。我们的残留光谱与海洋发色溶解有机质（chromophoric dissolved organic matter, CDOM）的光谱特征相似，表明CDOM是本研究样品中的主要发色团。基于本次光吸收测定结果，我们估算得到巴罗海域海水与霜花中的溶解有机碳（dissolved organic carbon, DOC）浓度分别约为130 μM C与360 μM C。我们推测CDOM是本研究海洋样品中羟基自由基（OH）的主要来源，且其大概率还参与其他重要的光化学反应过程。