Collaborative Research: U.S. GEOTRACES PMT: Dissolved trace metal distributions and size partitioning

国际GEOTRACES项目的目标是了解海洋中微量化学元素及其同位素的分布。根据定义，许多微量金属的含量很低，但它们对生命至关重要，因此被认为是浮游植物生长的营养物。其他元素可以用于追踪其他海洋过程，有些元素（如铅）很重要，因为它们是污染物。该项目的主要目标是测量溶解在海水中的铁、锰、锌、铜、镉、镍、铅和钪的浓度，沿着从阿拉斯加向南延伸到太平洋塔希提岛的全深度海洋站。专门的采样和过滤技术也将使这些研究人员和他们的同事能够确定这些金属在非常小的颗粒上的分布。一名研究生和几名本科生将参加这个项目。美国GEOTRACES太平洋经向样带计划于2018年秋季进行，旨在系统而彻底地确定跨越沉积、大气和热液金属供应带的巡航样带上微量元素和同位素的分布；与几个地带性生物生产和氧化机制相交；穿越复杂的赤道上升流系统；它包含了已知最古老的深海。本提案的主要目标是确定溶解（0.2微米过滤）微量营养素金属Fe， Mn, Zn, Cu， Cd和Ni的浓度，以及示踪剂Pb和Sc，在收集的每个水柱和表面样品上，使用两种完善的多元素分析方法，将在内部相互校准，以最大限度地提高数据质量。其中许多是GEOTRACES巡航分析所需的“关键元素”。还将对所有样品进行超滤，以确定这些元素的“真正可溶”（0.003微米）浓度，并通过差值计算胶体（0.003-0.2微米）分数。拟议研究的总体目标是了解控制微量营养素微量金属分布的海洋通量和过程，微量元素本身调节太平洋的初级生产和海洋二氧化碳吸收。拟议的研究将允许对太平洋中每种金属源通量和过程的经向影响进行估计，由于过去主要是太平洋的地带性巡航横断面，迄今为止对这些影响的限制很少。胶体分布是特别有针对性的，以便获得关于不同溶解金属池的反应性（关于清除和生物利用度）的额外信息，以及提供对金属物理化学形态的基本约束，这对于八种金属中的许多金属来说都是不明确的。

The goal of the international GEOTRACES program is to understand the distributions of trace chemical elements and their isotopes in the oceans. Many trace metals, which are by definition present in very low amounts, are essential for life and thus considered nutrients for phytoplankton growth. Other elements can be useful for tracing other ocean processes, and some (such as lead) are important because they are pollutants. The primary goal of this project is to measure the concentrations of iron, manganese, zinc, copper, cadmium, nickel, lead, and scandium dissolved in seawater along a line of full-depth ocean stations extending south from Alaska to Tahiti in the Pacific Ocean. Specialized sampling and filtration techniques will also enable these investigators and their colleagues to determine the distribution of these metals on very small particles. A graduate student and several undergraduate students will take part in the project.The U.S. GEOTRACES Pacific Meridional Transect, planned for the fall of 2018, aims to systematically and thoroughly determine the distribution of trace elements and isotopes on a cruise transect that spans zonal bands of sedimentary, atmospheric, and hydrothermal metal supplies; intersects several zonal biological production and oxygenation regimes; traverses the complex equatorial upwelling system; and encompasses the oldest known deep waters in the ocean. The primary goal of this proposal is to determine the concentrations of dissolved (0.2 micron-filtered) micronutrient metals Fe, Mn, Zn, Cu, Cd, and Ni, as well as tracers Pb and Sc, on every water column and surface sample collected, using two well-established multi-element analytical methods that will be intercalibrated internally to maximize data quality. Many of these are "key elements" required for analysis on GEOTRACES cruises. Ultrafiltration will also be completed on all samples to determine the "truly soluble" (0.003 micron) concentrations of these elements and to calculate, by difference, the colloidal (0.003-0.2 micron) fraction. The overarching goal of the proposed research is to understand the ocean fluxes and processes that control the distributions of micronutrient trace metals, which themselves modulate primary production and oceanic carbon dioxide uptake, in the Pacific Ocean. The proposed research will allow for an estimate of the meridional influence of each of these metal source fluxes and processes in the Pacific, which is poorly constrained to date due to the mostly zonal Pacific cruise transects in the past. Colloidal distributions are specifically targeted in order to derive additional information on the reactivity (with respect to both scavenging and bioavailability) of distinct dissolved metal pools, as well as to provide a basic constraint on metal physicochemical speciation, which is poorly defined for many of the eight metals.