Collaborative Research: Investigating tree rings as archives for atmospheric Hg concentrations using Hg, carbon isotopes, and comparisons to other proxies

除了记录大气状况，树木还吸收大气污染物，如汞，并将它们储存在它们每年生产的木材中。因此，树木年轮是一个有希望的历史汞污染档案，然而，关于树木如何吸收汞并将汞储存在年轮中，仍有许多未知之处。这项研究项目旨在通过研究树木生理如何影响树木从空气中捕捉汞的方式来解决这个问题。其他汞档案(如冰芯)的年代测定和汞沉积记录往往具有很高的不确定性。比较树木年轮和其他记录将有助于加深对历史上汞污染的理解。环境中存在几百年以上的汞的记录很少。该项目的目标之一是建立长达2000年的大气汞记录，提高我们对自然大气汞的了解，包括汞如何受到火山活动、野火和过去气候变化的影响。该项目产生的知识和数据将对未来与历史工业实践和土地利用变化有关的汞污染研究项目具有巨大价值，并将有助于我们对工业时代汞污染的性质和规模的研究，并为寻求进一步减少大气汞的人提供新的见解。工业化前大气汞的新的可靠记录对于目前监测和评估作为《联合国水稻田公约》一部分的汞排放变化的努力也极其重要。在这个项目中开发的信息、见解和方法将用于为本科生和研究生提供令人兴奋的教育和培训机会，包括那些来自服务不足群体的学生，并将用于K-12教育工作者的实践科学模块。尽管树木年轮是重建大气汞(汞)过去浓度的一个有前途的高分辨率档案，但仍有一些因素需要进一步研究。这一研究项目旨在通过以下方式提高年轮作为汞档案的利用率：1)使用同时稳定的碳同位素测量，以更好地了解与气孔传导相关的树内过程如何影响汞进入树轮；2)将树轮中的汞浓度与小流域湖泊沉积物和冰芯的测量结果进行比较，以测试观测到的汞信号的保真度；以及3)开发来自树轮的汞浓度的长期记录，以调查大气汞的重要自然驱动因素(如火山活动、野火和气候)。通过汞浓度和稳定碳同位素测量的独特组合，将更好地了解生物对汞进入树轮的影响。通过比较树木年轮中汞的浓度与小流域湖泊沉积物和冰芯中汞沉积的测量结果，这两种类型记录之间的差异和相似之处将有助于理解汞是如何保存在这些不同的档案中的，从而提供关于沉积档案中沉积后过程的重要信息。最后，树木年轮汞浓度的长期(至2000年)记录将提高我们对大气汞自然变异性的理解。该项目由地球生物学和低温地球化学计划以及既定的激励竞争研究计划(EPSCoR)共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

In addition to recording atmospheric conditions, trees also take up atmospheric pollutants, such as mercury, and store them in the wood they produce each year. Thus, tree rings are a promising archive of historic mercury pollution, however there remains a lot unknown about how trees take up and then store mercury in their rings. This research project aims to address this by studying how tree physiology influences how trees capture mercury from the air. Other archives of mercury (e.g. ice cores) often have high uncertainty in their dating and record mercury deposition. Comparing tree rings and other records will improve understanding of historic mercury pollution. There are very few records of mercury in the environment that are older than a few hundred years. One of the aims of this project is to develop records of up to 2000 years of atmospheric mercury, improving our understanding of natural atmospheric mercury, including how mercury is influenced by volcanic activity, wildfire and past climate changes. The knowledge and data generated in this project will be of immense value to future research projects on mercury pollution related to historic industrial practices and land-use changes, and will assist in our research into the nature and scale of industrial era mercury pollution and provide new insights to those seeking to further reduce atmospheric mercury. New reliable records of pre-industrial atmospheric mercury are also extremely important for current efforts to monitor and assess changes in mercury emissions as part of the United Nations Minamata Convention. Information, insights and approaches developed in this project will be used in exciting education and training opportunities for undergraduate and graduate students, including those from underserved groups, and in hands-on science modules for K-12 educators. Although tree-rings are a promising high-resolution archive for reconstructing past concentrations of atmospheric mercury (Hg) there remain factors that need to be further investigated. This research project aims to improve the utility of tree-rings as an Hg archive by 1) using concurrent stable carbon isotope measurements to better understand how within-tree processes related to stomatal conductance influence the incorporation of Hg into tree rings; 2) comparing concentrations of Hg in tree rings to measurements from small-catchment lake sediment and ice cores to test the fidelity of the Hg signals observed; and 3) develop long-term records of Hg concentrations derived from tree rings to investigate important natural drivers of atmospheric Hg (e.g. volcanic activity, wildfire & climate). Through the unique combination of Hg concentrations and stable carbon isotope measurements, the biotic influences on the incorporation of Hg into tree rings will be better understood. By comparing concentrations of Hg in tree rings to Hg deposition measurements from small-catchment lake sediment and ice cores, the differences and similarities between these two types of records will improve understanding of how Hg is preserved in these different archives, providing important information on post-depositional processes in depositional archives. Finally, a long-term (up to 2000 year) record of Hg concentration from tree rings will improve our understanding of natural variability in atmospheric Hg.This project is jointly funded by the Geobiology and Low-Temperature Geochemistry Program, and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.