SGER: Phosphorus release and metal redox cycling associated with sediment reworking in the Colorado River Delta, Lake Powell, Utah

0621371赫林SGER：美国犹他州鲍威尔湖科罗拉多河三角洲沉积物改造引起的磷释放和金属氧化还原循环。由于2000年开始的干旱和水库的运作，为下游的科罗拉多河流域各州提供了稳定的供水，鲍威尔湖目前只有46%的容量。在这种情况下，河流的流入穿过了以前沉积在科罗拉多河三角洲的沉积物。我们推测，随后的再悬浮ofdeposits可能会导致增强磷释放和金属氧化还原循环。近年来，研究发现，在与三角洲沉积物相交的底层水中，缺氧的发展也可能导致沉积物中氧化铁载体相的还原溶解，从而导致磷的释放。鲍威尔湖的初级生产是磷的限制，磷的有效性变化可能会产生重大的生态后果。由科罗拉多河输送的悬浮沉积物是鲍威尔湖磷的主要来源;随着科罗拉多河流入鲍威尔湖，大部分沉积物沉积下来（即，河-湖边界）。因此，先前沉积的三角洲沉积物代表了磷的大量储存。该项目将研究地球化学和物理过程的耦合及其对磷和痕量金属动力学的影响。磷在固相（特别是悬浮沉积物和三角洲沉积物）中的形态将被确定，并与磷可能从沉积物中释放的条件有关。金属还原溶解的作用（例如，铁）氧化物在磷释放中的作用也将被研究。磷的动态对鲍威尔湖的初级生产力起着关键的控制作用。我们预计，我们的研究结果将显示是否磷和微量金属动力学改变在当前条件下，科罗拉多河流入削减通过先前沉积的三角洲沉积物。如果磷动态受到影响，初级生产模式和从干旱条件下恢复期间底层水缺氧的发展可能与历史模式有很大不同。该SGER项目还将支持加州理工学院环境科学工程三年级研究生理查德·怀尔德曼先生的研究生培训。&除了他的学术研究，怀德曼先生一直积极参与外展和环境宪章高中在劳恩代尔，加利福尼亚州，公立学校位于一个欠发达地区的洛杉矶县。由于目前湖泊水位较低，有一个独特的机会来研究沉积物改造对营养动态的影响，特别是沉积物中磷的释放。目前，以前沉积的沉积物暴露于河流流入。随着湖水水位的上升，这些沉积物将被重新淹没。由于2000 - 2004年的干旱和2005年的径流量超过平均水平，在沉积物三角洲造成了前所未有的物理条件，我们正在请求SGER资助，以研究这个变化系统中的磷和微量金属动态。这项工作的时间安排也与填海局计划的实地取样相一致，填海局将为取样提供后勤支持。

0621371HeringSGER: Phosphorus release and metal redox cycling associated with sediment reworking inthe Colorado River Delta, Lake Powell, UtahAbstract. As a result of the drought that began in 2000 and reservoir operations that provided aconstant water supply to the lower Colorado River basin states, Lake Powell is currently at only46% capacity. Under these conditions, the river inflows cut through sediments previouslydeposited in the Colorado River Delta. We hypothesize that the consequent resuspension ofsediments may result in enhanced phosphorus release and metal redox cycling. In recent years, ithas been observed that anoxia develops in bottom water intersecting the delta sediments, whichcould also result in P release due to reductive dissolution of iron oxide carrier phases in thesediments.Primary production in Lake Powell is phosphorus limited and changes in phosphorusavailability could have significant ecological consequences. Suspended sediment transported bythe Colorado River is the principal source of phosphorus to Lake Powell; much of this sedimentload is deposited as the Colorado River flows in to the lake (i.e., the river-lake boundary). Thuspreviously-deposited delta sediments represent a substantial reservoir of phosphorus.Intellectual Merit. The proposed project will examine the coupling of biogeochemical andphysical processes and their impacts on phosphorus and trace metal dynamics. Speciation ofphosphorus in solid phases (specifically the suspended sediment and delta sediments) will bedetermined and related to the conditions under which phosphorus may be released from thesediments. The role of reductive dissolution of metal (e.g., iron) oxides in phosphorus releasewill also be examined.Broader Impact. Phosphorus dynamics exert a key control on primary production inLake Powell. We anticipate that our results will show whether phosphorus and trace metaldynamics are altered under the current conditions where Colorado Rived inflows cut throughpreviously-deposited delta sediments. If phosphorus dynamics are affected, patterns of primaryproduction and the development of bottom water anoxia during the recovery from droughtconditions may be significantly different from historical patterns.This SGER project will also support the graduate training of Mr. Richard Wildman, athird year graduate student in Environmental Science & Engineering at Caltech. In addition tohis academic studies, Mr. Wildman has been actively engaged in outreach and curriculumdevelopment at the Environmental Charter High School in Lawndale, CA, a public schoollocated in an underserved area of Los Angeles County.SGER Justification. Because of the current low lake level, there is a unique opportunity toexamine the effects of sediment reworking on nutrient dynamics, specifically phosphorus releasefrom sediments. Currently, previously-deposited sediments are exposed to river inflows. As thelake levels rise, these sediments will be resubmerged. Since the extreme drawdown in the 2000-2004 drought and the above-average inflows of the 2005 run-off are creating unprecedentedphysical conditions in the sediment delta, we are requesting SGER funding to examine thephosphorus and trace metal dynamics in this changing system. This work is also timed tocoincide with planned field sampling by the Bureau of Reclamation, which will providelogistical support for sampling.