Validation of a New Geochemical Approach to Constrain Deep Sea Porewater Residence Times and Advection Rates: Applications to Biogeochemical Cycling at Guaymas Basin

该项目建议验证一种新的方法，使用生物上保守的、自然产生的示踪剂Re 224来测量深海沉积物中的孔隙水流动动力学，这种示踪剂不断地由孔隙水产生。这项技术将在前往加利福尼亚州海湾瓜伊马斯盆地的邮轮期间使用独立的孔隙水通量测量(即热梯度和镁剖面)进行验证，该邮轮已由美国国家科学基金会资助。一旦得到验证，该技术将广泛适用于所有沉积环境，包括海洋、河流/溪流、湿地和湖泊。了解孔隙水流动动力学对于了解海洋和其他水生系统的化学平衡、微生物生态和全球热流具有重要意义。这一提议假设，无论渗漏的类型或组成如何，短暂的镭同位素Ra 224都可以作为深海系统中孔隙水流动的有效示踪剂，因为它的源和汇可以受到唯一的限制。该方法将在瓜伊马斯盆地进行测试，该盆地由不同渗漏率的地区组成，并提供热液系统产生的孔隙水温度梯度。因此，受高温水/岩石相互作用影响的镁和其他阳离子中的热通量和梯度可以用来独立验证Ra224测量的孔隙水流量。

This project proposes to validate a new approach to measure porewater flow dynamics from deep sea sediments using a biologically conservative, naturally-occurring tracer, Radium 224, which is constantly produced by porewaters. The technique will be validated using independent measures of porewater fluxes (i.e. heat gradients and magnesium profiles) during a cruise to the Guaymas Basin in the Gulf of California that is already funded by NSF. Once validated the technique will be broadly applicable to all sedimentary environments including oceans, rivers/streams, wetlands and lakes. Understanding porewater flow dynamics is important to understanding ocean and other aquatic system chemical budgets, microbial ecology and global heat flow. This proposal hypothesizes that the short-lived radium isotope Ra 224 may serve as an effective tracer of porewater flows in deep ocean systems, regardless of the type or composition of seepages, because its sources and sinks can be uniquely constrained. The method will be tested in the Guaymas Basin which is comprised of areas undergoing a range of seepage rates and offers porewater thermal gradients resulting from the hydrothermal system. As a result heat fluxes and gradients in magnesium and other cations affected by high-temperature water/rock interactions can be used to independently validate the porewater flows measured by Ra 224.