Collaborative Research: Sources and Fates of Ecosystem Nutrients Across the Hawaiian Islands

该项目由加州大学圣巴巴拉分校、夏威夷大学和康奈尔大学合作完成。该研究提交给了环境地球化学和生物地球化学项目（EGB），并得到了大气化学、岩石学和地球化学以及水文科学项目的支持。这个跨学科团队包括一位生态系统生态学家、一位土壤学家、一位大气化学家和一位同位素地球化学家。目的是评估沉积到夏威夷生态系统的元素的来源和命运。将利用底物年龄和沉淀的梯度。对其中某些梯度的初步分析表明，大气来源的元素对较老和较湿系统的功能都是至关重要的。该项目将：(1)通过湿、干和云水沉积确定元素在大气中的沉积速率；(2)利用镧系元素，特别是铕异常和钕同位素，追踪大陆尘埃对更多不动元素池的综合贡献；(3)确定各站点土壤的矿物学、元素库和风化状况，测量大陆沙尘输入的矿物学指标；(4)直接分析各站点大气源与风化源对植物和土壤锶库的累积贡献，并评价该锶的来源；(5)综合这些测量来估计大气输入对池的贡献和所有主要元素的可用性，因为这些随基质年龄和气候而变化。大气湿、干和云沉积将在代表夏威夷物理气候系统末端成员的两个地点直接监测。来自亚洲的矿物气溶胶的沉积将通过测量土壤中石英等独特物质的浓度和大陆来源的微量元素模式（稀土元素和Th、Hf）和钕同位素的浓度来推断。此外，将探讨Nd和P之间的关系，以确定是否有可能使用Nd同位素作为矿物气溶胶对夏威夷生态系统P贡献的指标。对土壤的测量将用于确定矿物学和元素库在空间和时间上的模式；因为这些地点排列在明确的梯度上，这些可以用来计算风化的输入。锶同位素测量将利用大多数大气沉积的海洋源与风化的岩石源之间的同位素比值差异；这两者在夏威夷的系统中都有很好的定义和一致。石英和微量元素的测量将允许估计来自高放射性成因的大陆源的Sr输入。

This project is a collaboration between the University of California, Santa Barbara, the University of Hawaii, and Cornell University. It was submitted to the Environmental Geochemistry and Biogeochemistry Program (EGB) and supported by the Atmospheric Chemistry, Petrology and Geochemistry, and Hydrologic Sciences Programs. The interdisciplinary team includes an ecosystem ecologist, a pedologist, an atmospheric chemist, and an isotope geochemist. The objective is to evaluate the sources and fates of elements deposited to Hawaiian ecosystems. Well characterized gradients in substrate age and precipitation will be utilized. Preliminary analyses of certain of these gradients suggest that atmospherically derived elements are crucial to the functioning of both older and wetter systems. This project will: (1) determine rates of atmospheric deposition of elements by wet, dry, and cloudwater deposition; (2) use elements in the lanthanide series, particularly the europium anomaly and neodymium isotopes, to trace the integrated contribution of continental dust to pools of more immobile elements; (3) determine the mineralogy, element pools, and weathering status of soils in all sites, and measure mineralogic indicators of dust inputs from continental sources; (4) analyze directly the cumulative contribution of atmospheric versus weathering sources to plant and soil strontium pools in all sites, and evaluate the sources of that strontium; and (5) integrate these measurements to estimate the contribution of atmospheric inputs to the pools and availability of all major elements, as these vary with substrate age and climate. Atmospheric wet, dry, and cloud deposition will be directly monitored at two sites representing the end members of the Hawaiian physical climate system. Deposition of mineral aerosols derived from Asia will be inferred by measuring the concentration of unique materials such as quartz in soils and the concentration of continentally derived trace element patterns (rare earth elements and Th, Hf) and neodymium isotopes. Further, the relationship between Nd and P will be explored to determine whether it is possible to use Nd isotopes as an indicator of mineral aerosol contributions of P to Hawaiian ecosystems. Measurements of soils will be used to determine patterns of mineralogy and element pools in space and time; because the sites are arrayed on well defined gradients, these can be used to calculate weathering inputs. Strontium isotope measurements will make use of the difference in isotopic ratio between the marine source of most atmospheric deposition and the rock source of weathering; both of these are well defined and consistent in the Hawaiian system. Measurements of quartz and trace elements will allow an estimate of Sr input from highly radiogenic continental sources.