Aerosol and seawater beryllium-7 concentrations from the US GEOTRACES GP17-OCE cruise on R/V Roger Revelle (RR2214) in the South Pacific and Southern Oceans from December 2022 to January 2023

Beryllium-7, a radioactive isotope with a half-life of 53.3 days, is formed in the atmosphere, attaches to aerosol particles, and is deposited on the earth’s surface through wet and dry processes. In this project, we measured Be-7 concentrations in aerosol particles and in seawater samples (depths < 200 meters) collected on the GEOTRACES GP17-OCE cruise aboard R/V Roger Revelle. The cruise originated in Papeete, Tahiti, French Polynesia on 1 December 2022 and concluded on 25 January 2023 in Punta Arenas, Chile. Sixteen aerosol samples and seawater from twelve stations in the South Pacific and Southern Oceans were collected. The dataset will be used to study the deposition of trace elements and isotopes (TEIs) and upper ocean mixing processes. Aerosol deposition is an important source of TE micronutrients to open ocean areas that are far removed from riverine sources. But, while the collection aerosol of samples for TEI analysis is straightforward, estimating the deposition flux also requires an appropriate deposition velocity (i.e. deposition flux is the product of the aerosol concentration and deposition velocity). Because Be-7 is supplied to the open ocean exclusively through aerosol deposition and it is removed through radioactive decay, the water column inventory and aerosol concentration of Be-7 can be used to derive the deposition velocity applicable to aerosol TEIs. The penetration of dissolved Be-7 below the ocean mixed layer is limited by the isotope's half-life and the rate of vertical diffusive mixing. Through modeling, the shape of the Be-7 profile below the mixed layer provides an estimate for the vertical diffusivity coefficient (Kz), which can be used to calculate fluxes of chemical species (e.g. oxygen) and physical properties (e.g. heat).

铍-7（Beryllium-7）是一种半衰期为53.3天的放射性同位素，在大气中生成后附着于气溶胶颗粒，并通过干湿沉降过程抵达地球表面。本项目依托"罗杰·雷维尔号"（R/V Roger Revelle）科考船执行的GEOTRACES GP17-OCE航次，对采集的气溶胶颗粒与水深小于200米的海水样本中的铍-7浓度进行了测定。该航次于2022年12月1日从法属波利尼西亚塔希提岛帕皮提港启航，2023年1月25日于智利蓬塔阿雷纳斯港结束。本次航次在南太平洋与南大洋的12个站位共采集16份气溶胶样本与海水样本。本数据集将用于研究微量元素与同位素（Trace Elements and Isotopes, TEIs）的沉降过程以及上层海洋混合机制。气溶胶沉降是远离陆源径流输入的开阔大洋区域微量营养元素的重要来源。然而，尽管用于微量元素与同位素分析的气溶胶样本采集流程相对简便，但估算沉降通量还需确定合适的沉降速度（deposition velocity）——即沉降通量等于气溶胶浓度与沉降速度的乘积。由于铍-7仅通过气溶胶沉降输入开阔大洋，并通过放射性衰变被清除，因此可通过水柱储量与大气气溶胶浓度推导适用于气溶胶微量元素与同位素的沉降速度。溶解态铍-7在海洋混合层（ocean mixed layer）下方的渗透过程受同位素半衰期与垂直扩散混合速率的双重限制。通过建模分析，混合层下方铍-7的剖面形态可用于估算垂直扩散系数（Kz），而该系数可用于计算各类化学物质（如氧气）与物理属性（如热量）的通量。