Temporal Constraints on the Delivery of Terrestrial Organic Carbon to Marine Sediments

在这个项目中，伍兹霍尔海洋研究所的研究人员将尝试量化陆生维管植物生物标志物在陆地上合成和在海洋沉积物中沉积之间的停留时间。该方法将包括对缺氧、每年分层的沉积物进行超高分辨率采样，并对叶蜡和木质素酚类进行化合物特异性的AMS 14c测年。地面上的核武器试验在1963年达到顶峰，在大气中产生了一个巨大而突然的14C浓度峰值，这远远超过了化合物专用的AMS 14C测量的不确定度。放射性碳“炸弹峰值”单个生物标记化合物（或化合物类别）将以接近每年的采样分辨率进行鉴定。将生物标志物化合物中鉴定的14c峰的日历年龄与来自四个不同海洋站点的年层状沉积物中已知的1963年龄层进行比较，以获得生物标志物的居住和运输时间，精度高达1-2年。将使用一种建模方法来检查炸弹尖峰曲线的特征，以便区分风成和河流运输途径，以及水库（例如森林凋落物、土壤、河床、洪泛平原和湖泊）的储存期。除了确定爆炸峰值的时间外，高分辨率采样还可以识别曲线的大小和形状的细节，对储层储存时间以及古代有机化合物的污染进行关键诊断。研究地点将包括一个气候带的样带，从热带的卡里亚科盆地（委内瑞拉），横跨温带的美国（佩塔夸姆斯库特河，RI；圣巴巴拉盆地，CA；鳗鱼河盆地，CA），直到北方的萨尼奇湾（不列颠哥伦比亚省，加拿大）。这些研究地点根据流域（面积、地形）、气候（年平均温度、降水）、植被覆盖（热带雨林、半干旱灌丛、温带落叶林、北方常绿林）和人类土地利用影响程度而有所不同。这项拟议的工作将提供对陆地有机碳停留时间的广泛环境和人为影响的见解，使结果能够在全球范围内进行扩展。此外，准确量化陆地生物标志物的停留时间将有助于这些化合物作为地质年代学和古气候代用物的发展。

ABSTRACTOCE-0137005In this project, researchers at the Woods Hole Oceanographic Institution will attempt to quantify the residence times of terrestrial vascular plant biomarkers between their synthesis on land and deposition in marine sediments. The approach will involve ultra-high resolution sampling of anoxic, annually laminated sediments and compound-specific AMS 14 C dating of leaf waxes and lignin phenols. Above-ground nuclear weapons testing peaked in 1963, creating a large and abrupt peak in atmospheric 14C concentration that is discernable well above the uncertainty in compound- specific AMS 14 C measurements. The radiocarbon "bomb spike" individual biomarker compounds (or compound classes) will be identified with near-annual sampling resolution. The calendar age of the 14 C peak identified in the biomarker compounds will be compared to the known 1963 age layer in annually laminated sediments from four different marine sites to derive biomarker residence and transport times with precision as high as 1-2 years.A modeling approach will be used to examine the characteristics of the bomb spike curve, in order to distinguish between eolian and riverine transport pathways, as well as periods of storage in reservoirs (e.g., forest litter, soils, river beds, floodplains and lakes). In addition to timing of the bomb spike, the high-resolution sampling will permit identification of details of the magnitude and shape of the curves, key diagnostics for reservoir storage time as well as contamination with ancient organic compounds. The study locations will encompass a transect of climatic zones from the tropical Cariaco Basin (Venezuela), across the temperate United States (Pettaquamscutt River, RI; Santa Barbara Basin, CA; Eel River basin, CA), up to the boreal Saanich Inlet (British Columbia, Canada). These study sites vary according to drainage basin (area, topography), climate (mean annual temperature, precipitation), vegetation cover (tropical rainforest, semi-arid scrubland, temperate deciduous forest, boreal evergreen forest), and degree of human land-use impact. This proposed work should provide insights into a wide range of environmental and anthropogenic impacts on the residence times of terrestrial organic carbon, allowing results to be scaled globally. In addition, accurately quantifying terrestrial biomarker residence times will contribute greatly to the development of these compounds as geochronological and paleoclimatic proxies.