The Linkage between Copper Speciation and Nitrogen Cycling in Stratified Lakes

0337201伯努瓦稀有金属通过限制关键的共生物种或组合的生长或功能，对地球化学循环产生不成比例的影响。 众所周知，铁限制了世界海洋中高硝酸盐、低叶绿素区域的初级生产力，对全球碳循环具有潜在的重要影响。 淡水环境中微量营养元素金属的限制问题尚未探讨。 该建议是初步研究，调查溶解铜形态（和随之而来的反应性和生物利用度）的影响，反硝化细菌在分层湖泊。 我们建议研究这个具体的例子作为一个起点，探索更广泛的一般问题的影响，微量金属对主要水生生物地球化学循环。 这一制度的目标是：（1）对Cu的形态及其在某些淡水沃茨中的低生物利用度的充分研究，（2）Cu对于影响反硝化作用的细菌酶的基本性质，（3）分层湖泊作为自然的大规模间歇反应器实验的效用，以及（4）现有的间接证据表明Cu可以限制实验室培养中的反硝化作用，反硝化中间体（特别是N2 O）在许多分层湖泊中积累。 虽然这样的系统代表了一个合乎逻辑的起点，这项研究的结果可能有更广泛的影响，在淡水沃茨，包括湖泊，河流和地下沃茨的微量营养素限制的主题。 (1)促进教学、培训和学习：湖泊特别适合作为教授地球科学原理的范例，因为它们是人们熟悉的系统，在这些系统中，化学和物理过程得到了清晰而简单的表达。 耶鲁大学环境学院拥有大约220名硕士生，他们通常从事环境政策和管理的职业，而不是科学，但他们渴望了解环境科学的基本原理。 本研究为这一群体的教学和培训提供了一个理想的机会。 结果将纳入三门课程的课程：生物地球化学和污染，现场环境分析方法和水生生态学。 此外，两名硕士生从学校接受研究助理将直接参与研究。 (2)扩大代表性不足群体的参与：该项目支持的两名最有可能的博士生候选人都是女性。 如果被选中，这两个人都将在研究中发挥重要作用。 (3)对社会的益处：这项研究解决了两个环境化学问题的公共福利相当重要的可能联系：微量金属和氮循环。 由于金属在湖泊和溪流中可能产生有害影响，因此人们普遍对金属感兴趣。 在这里，我们考虑他们是否也可以作为限制微量营养素。 氮循环涉及许多社会关注的问题，包括富营养化（来自过量的NO3-），N2 O作为温室气体，酸沉降（HNO 3）和人为干预引起的扰动（全球50%的氮固定估计是工业）。

0337201BenoitScarce metals can have a disproportionate influence on biogeochemical cycles by limiting growth or function of key planktonic species or assemblages. It is already known that Fe limits primary productivity in high-nitrate, low-chlorophyll regions of the world's oceans, with potentially important consequences for global carbon cycling. Largely unexplored is the question of limitation in fresh water environments by micronutrient metals. This proposal is for preliminary research to investigate the influence of dissolved Cu speciation (and consequent reactivity and bioavailability) on denitrification by bacteria in stratified lakes. We propose to study this specific example as a starting point to explore the much broader general question of the influence of trace metals on major aquatic biogeochemical cycles. This system is targeted because of: (1) the well-studied speciation of Cu and its low bioavailability in some fresh waters, (2) the essential nature of Cu for bacterial enzymes that effect denitrification, (3) the utility of stratified lakes as natural, large-scale batch reactor experiments, and (4) existing circumstantial evidence that Cu can limit denitrification in lab cultures, and that denitrification intermediaries (esp. N2O) build-up in many stratified lakes. While such systems represent a logical starting point, the results of this research could have much broader implications on the topic of micronutrient limitation in fresh waters, including lakes, rivers, and ground waters.Broader Impacts The proposed research will have broader impacts in three separate ways. (1) Promoting Teaching, Training and Learning: Lakes are especially well-suited as examples for teaching principles of geosciences, because they are familiar systems in which chemical and physical processes are clearly and simply expressed. Yale's Environment School is home to about 220 masters students who are often going on to careers in environmental policy and management, rather than science, but are eager to obtain an understanding of the fundamental principles of environmental science. The proposed research provides an ideal opportunity for teaching and training this group. Results will be incorporated into the curriculum of three courses: Biogeochemistry and Pollution, Methods of Field Environmental Analysis, and Aquatic Ecology. In addition, two master's students receiving Research Assistantships from the School will be directly involved in the research. (2) Broadening Participation of Underrepresented Groups: The two most likely candidates for the PhD student supported by this project are both women. Either would play a major role in the research if selected. (3) Benefits to Society: This research addresses the possible linkage of two environmental chemical issues of considerable importance to public welfare: trace metals and the nitrogen cycle. Metals have generally been of interest because of possible harmful effects in lakes and streams. Here we consider whether they may also function as limiting micronutrients. The nitrogen cycle involves a number of issues of societal concern, including eutrophication (from excess NO3-), N2O as a greenhouse gas, acid deposition (HNO3), and perturbations caused by human intervention (50% of global N fixation is estimated to be industrial).