Chemical characterization of ambient aerosol collected during the southwest monsoon and intermonsoon seasons over the Arabian Sea: Labile-Fe(II) and other trace metals
Chemical characterization of ambient aerosol collected during the southwest monsoon and intermonsoon seasons over the Arabian Sea: Labile-Fe(II) and other trace metals
复制标题
阿拉伯海西南季风和季风间期间收集的环境气溶胶的化学特征：不稳定铁 (II) 和其他微量金属
DOI：
10.1029/1998jd100067
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发表时间：
1999
影响因子：
--
通讯作者：
M. Hoffmann
中科院分区：
文献类型：
--
作者：
R. Siefert;A. Johansen;M. Hoffmann
铁（Fe）在海洋某些区域的大气沉降是生物群铁的重要营养源，生物群吸收铁的能力取决于铁的形态。因此，了解大气中铁的形态对于理解铁作为表层海水营养源的作用至关重要。1995年期间，在阿拉伯海上非连续的两个月测定了不稳定亚铁（Fe(II)）浓度以及铁和其他重要微量金属、阳离子和阴离子的总浓度。在阿拉伯海的印度洋季风间歇期和西南季风季节采集了环境气溶胶样本。采样是在德国“流星号”研究船5月（M32/3航段；季风间歇期）和7月/8月（M32/5航段；西南季风）进行的。两条航迹都沿着东经65度，每次航行30天（M32/3航段从北向南，M32/5航段从南向北）。使用空气动力学截止尺寸为3μm的大容量二分虚拟撞击器收集用于金属分析的细颗粒和粗颗粒气溶胶组分。使用小容量收集器收集用于阴离子和阳离子分析的气溶胶样本。在样本采集后立即对不稳定 - Fe(II)进行分析，以尽量减少样本储存期间可能发生的任何铁氧化还原反应。分析过程包括在pH值为4.2的甲酸盐/甲酸缓冲溶液中对过滤器进行萃取，然后对可溶性Fe(II)进行比色定量。金属、阴离子和阳离子在航次结束后进行分析。季风间歇期大气中水溶性不稳定 - Fe(II)总浓度在4.75到80%之间，存在于细颗粒组分（<3.0μm）中。在西南季风期间，大气中水溶性不稳定 - Fe(II)浓度始终低于检测限（<0.34到<0.089 ng m⁻³，取决于采样空气体积）。气团后向轨迹（5天，三维）显示，西南季风期间采样的气团平流经过开阔的印度洋，而季风间歇期采样的气团平流经过非洲东北部、沙特阿拉伯半岛和南亚。这些计算结果与对数据集进行的统计分析结果一致，统计分析表明季风间歇期样本中地壳物质引起的方差大于西南季风期间地壳物质引起的方差。当后向轨迹平流经过附近大陆块时，地壳成分的因子得分也更高。还对不稳定Fe(II)高于检测限的季风间歇期样本进行了主成分分析。水溶性不稳定Fe(II)与其他物质相关性不佳，表明在平流过程中铁可能发生了大气过程。
Atmospheric deposition of iron (Fe) to certain regions of the oceans is an important nutrient source of Fe to the biota, and the ability of the biota to uptake Fe is dependent on the speciation of the Fe. Therefore understanding the speciation of Fe in the atmosphere is critical to understanding the role of Fe as a nutrient source in surface ocean waters. Labile ferrous iron (Fe(II)) concentrations as well as total concentrations for Fe and other important trace metals, cations, and anions were determined over the Arabian Sea for two nonconsecutive months during 1995. Ambient aerosol samples were collected during the Indian Ocean intermonsoon and southwest monsoon seasons over the Arabian Sea. Sampling took place aboard the German research vessel Meteor in the months of May (leg M32/3; intermonsoon) and July/August (leg M32/5; southwest monsoon). Both cruise tracks followed the 65th east meridian, traveling for 30 days each (from north to south during leg M32/3 and from south to north during leg M32/5). A high-volume dichotomous virtual impactor with an aerodynamic cutoff size of 3 μm was used to collect the fine and coarse aerosol fractions for metal analysis. A low volume collector was used to collect aerosol samples for anion and cation analysis. The analysis for labile-Fe(II) was done immediately after sample collection to minimize any possible Fe redox reactions which might occur during sample storage. The analytical procedure involved filter extraction in a formate/formic acid buffered solution at pH 4.2 followed by colorimetric quantification of soluble Fe(II). Metals, anions, and cations were analyzed after the cruise. Total atmospheric aqueous-labile-Fe(II) concentrations during the intermonsoon were between 4.75 and 80%) was present in the fine fraction (<3.0 μm). During the southwest monsoon, atmospheric aqueous-labile-Fe(II) concentrations were consistently below the detection limit (<0.34 to <0.089 ng m^(−3), depending on the volume of air sampled). Air mass back trajectories (5 day, three dimensional) showed that air masses sampled during the southwest monsoon had advected over the open Indian Ocean, while air masses sampled during the intermonsoon had advected over northeast Africa, the Saudi Arabian peninsula, and southern Asia. These calculations were consistent with the results of the statistical analysis performed on the data set which showed that the variance due to crustal species during the intermonsoon samples was greater than the variance due to crustal species during the southwest monsoon. The factor scores for the crustal components were also greater when the back trajectories had advected over the nearby continental masses. Principal component analysis was also performed with the intermonsoon samples where aqueous labile Fe(II) was above the detection limit. Aqueous labile Fe(II) did not correlate well with other species indicating possible atmospheric processing of the iron during advection.