Total Th data from samples collected on 5 cruises at Station ALOHA off Hawaii and Station M off California from 2019 to 2020

The abyssal plains of the oceans cover roughly half of the earth's surface, host enormous reservoirs of biodiversity and mineral resources, and play important roles in nutrient regeneration and carbon sequestration. The most important process controlling the structure and function of these ecosystems is the quantity and quality of food (mostly sinking organic particles) that reaches the deep-sea floor. The goals of this research were to evaluate the relative importance of small and large particles that sink to the deep-sea using the naturally occurring short-lived radionuclide, 234Th. Particulate and dissolved samples were collected throughout the water column (12-17 depths) during 5 cruises in the productive waters off of California (Station M, May and October 2019) within the nutrient-poor central Pacific, north of Hawaii (Station ALOHA, July 2019 and January and July 2020). Total water column (2 L) and particulate 234Th activities collected using in situ pumps (53 um, 1 um, and 0.3 um) have been measured in all of the samples collected from the 5 cruises: April 2019, July 2019, October 2019, January 2020, and July 2020. This dataset includes the Total Th measurements. Particulate Th is available in a separate, related dataset.

海洋深渊平原（abyssal plains）约占地球表面积的一半，蕴藏着规模庞大的生物多样性与矿产资源库，同时在营养盐再生与碳封存过程中发挥着关键作用。调控此类深海生态系统结构与功能的核心过程，是抵达深海床的食物基质（主要为沉降有机颗粒物）的数量与品质。本研究旨在利用天然存在的短寿命放射性核素234Th（钍-234），评估沉降至深海的小粒径与大粒径颗粒物的相对重要性。
研究团队在5个科考航次中，于全水柱（12至17个采样深度）采集了颗粒物与溶解态样品，采样海域涵盖加利福尼亚近海高生产力海域的M站（Station M，2019年5月、10月），以及夏威夷以北营养匮乏的中太平洋海域的ALOHA站（Station ALOHA，2019年7月、2020年1月与7月）。
针对上述5个航次（2019年4月、7月、10月，2020年1月、7月）采集的全部样品，均采用原位泵（in situ pumps，孔径分别为53 μm、1 μm与0.3 μm）完成了全水柱（2 L）与颗粒物态234Th活度的测定。本数据集包含总钍（Total Th）的测定数据，而颗粒物态钍的相关数据收录于另一独立关联数据集。