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Analysis of a major Aeolian dust input event and its impact on element fluxes and inventories at the DYFAMED site (Northwestern Mediterranean)
Marine Chemistry ( IF 3.0 ) Pub Date : 2020-03-27 , DOI: 10.1016/j.marchem.2020.103792
José Luis Mas , Jacobo Martín , Mai Khanh Pham , Elena Chamizo , Juan-Carlos Miquel , Iolanda Osvath , Pavel P. Povinec , Mats Eriksson , María Villa-Alfageme

Continental dust can be suspended and transported by the wind, reaching seawater masses far away from its source. The deposition of the aerosols on the ocean surface can alter the abundance of chemical species in the water column and contribute to element inventories in seafloor sediments. A major Saharan dust intrusion into the Western Mediterranean Sea was recorded at the DYFAMED site (Ligurian Sea) in 20th February 2004. We determined the influence of this dust event on the concentration of 30 minor and trace level elements (TE) in sinking particles collected by sediment traps deployed at 200 m and 1000 m depth, and how a dust flux event like this contributed to the exchange of TE, including Fe, with the water column during major dust events. With coupled sediment traps and aerosol samples, we assessed the short-term implications of dust events in the water column. The event produced a flux of fast (>111 m d−1) and slow (<20 m d−1) sinking dust particles, detected during 3 weeks at 200 m and 4 weeks at 1000 m depth. Additionally, the obtained results of element concentrations and particles flux show that a single dust deposition event can produce a sinking flux equivalent to annual deposition rates of elements relevant to biogeochemical cycles and/or pollution studies: (>60% for Cr and Cu, >70% for Al, >80% for Ni and Zn, >90% for V and Mn, >100% for Fe and Pb). The corresponding Enrichment Factors (EF) for the minor and TE analyzed in the sediment traps during the dust event were calculated. EF was used to determine how minor and trace element concentrations in sinking particles vary. The values ranged between 0.35 and 421 in both 200 m and 1000 m sediment traps. For most of the analyzed elements, the obtained EF values were higher than 1. On the contrary, V, Y, Zr, Nb, and Ce showed EF ~ 1 while Cr, Ni, Cu, Zn, Sn, and Pb showed EF < 1. Despite the variability in the EF values, vertical fluxes integrated during the dust deposition event increased from 200 m to 1000 m, except for I, which decreased. This contrasts strongly with the element fluxes integrated for the complete sampling period, which decrease or increase from 200 m to 1000 m, depending on the element. This suggests that sinking dust particles were acting generally as sinks of the TE. We conclude that, apart from I, a substantial portion of the elements from atmospheric dust input from a single deposition event can reach the mesopelagic layer of the Western Mediterranean basin without increasing the budget of those elements in the water column.



中文翻译:

DYFAMED站点(地中海西北部)的一次重大风尘输入事件及其对元素通量和清单的影响的分析

大陆灰尘可以被风悬挂和运输,到达远离其来源的海水团块。气溶胶在海洋表面的沉积会改变水柱中化学物质的丰度,并有助于海底沉积物中的元素清单。2004年2月20日,在DYFAMED站点(利古里亚海)记录到撒哈拉大沙漠侵入西地中海的情况。我们确定了该扬尘事件对收集到的沉降颗粒中30种微量和痕量水平元素(TE)浓度的影响。通过部署在200 m和1000  m处的沉积物陷阱 深度,以及这样的粉尘通量事件是如何在重大粉尘事件期间与水柱交换TE(包括Fe)的。结合沉积物捕集阱和气溶胶样品,我们评估了水柱中粉尘事件的短期影响。该事件产生了快速(> 111 m d -1)和慢速(<20  m d -1)下沉的尘埃通量,分别 在200 m的3周和1000 m的4周内 检测到 深度。此外,所获得的元素浓度和颗粒通量的结果表明,一次粉尘沉积事件可产生的沉降通量等于与生物地球化学循环和/或污染研究相关的元素的年沉积率:(铬和铜> 60%, Al含量为70%,Ni和Zn含量> 80%,V和Mn含量> 90%,Fe和Pb含量> 100%。计算了尘埃事件期间沉积物捕集阱中分析的微量元素和TE的相应富集因子(EF)。EF用于确定沉降颗粒中微量元素和痕量元素的浓度如何变化。在200 m和1000  m中,值的范围在0.35至421之间 沉积物陷阱。对于大多数分析元素,获得的EF值均大于1。相反,V,Y,Zr,Nb和Ce表示EF〜1,而Cr,Ni,Cu,Zn,Sn和Pb的EF <1。 1.尽管EF值存在变化,但除I值外,在粉尘沉积过程中积分的垂直通量从200  m增加到1000 m。这与整个采样周期内积分的元素通量形成鲜明对比,元素通量从200 m开始减少或增加 到1000 m,取决于元素。这表明下沉的尘埃颗粒通常充当TE的下沉。我们得出的结论是,除I外,来自一次沉积事件的大气尘埃输入中的大部分元素都可以到达西地中海盆地的中弹性层,而不会增加水柱中这些元素的预算。

更新日期:2020-03-27
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