Tracing Biogeochemical Cycles in the Weathering Environment using Mg and Li isotopes.

Project Description: 

Ca and Mg are released from silicate minerals during chemical weathering, react with atmospheric CO2, and are deposited as carbonate in the oceans, regulating global climate on geological time scales. Thus to estimate and predict CO2 consumption rates, it is important to identify and quantify the sources and fluxes of Ca and Mg that are discharged to the world’s oceans via rivers, and the weathering processes that produce those fluxes.

Research Location: 

Weathering Processes on Landslides

Project Description: 

A landslide chronosequence will be instrumented (nested suction lysimeters for collecting soil/saprolite pore waters, rain collectors, runoff collectors) and analyzed (via a suite of geochemical analyses of both solid and aqueous samples) to study the effects of landslides on chemical weathering processes and rates, the spatial and temporal variability of chemical weathering profiles in the LCZO, and to explore hypotheses regarding the establishment and maintenance of steady-state regolith profiles.

Research Location: 

Lithological Influences on Weathering Processes and Rates in the Luquillo Mountains of Puerto Rico

Project Description: 

Rapid weathering and erosion rates in mountainous tropical watersheds lead to highly variable soil and saprolite thicknesses which in turn impact, nutrient fluxes, and biological populations. To understand mineral nutrient cycling in such environments requires tracing nutrients through the entire critical zone: weathering bedrock, saprolite, soil, soil water, precipitation, vegetation, and microorganisms. A thorough understanding of nutrient cycling in tropical uplands is necessary in order to predict the effects of human impacts.

Research Location: 

Effects of riparian zone processes on elemental losses from volcaniclastic and granitic terrains

Project Description: 

Measure shallow groundwater chemistry in riparian well transects (upslope to stream bank) in Icacos and Bisley watersheds. Bisley well field will be installed as an extension of newly installed tension lysimeters in Bisley (H. Buss). Icacos well field will be an expansion of existing well field adjacent to primary well field, which now receives N fertilization. Quarterly sampling of nutrients, organic matter, Si, and major cations and anions will be conducted. Anticipated collaborations with M. Scholl (water isotopes to infer flow paths through well fields), H.

Research Location: 
Core Area(s) and/or Keywords: 

riparian biogeochemistry nitrogen DOC DOM

Elemental inputs and outputs from volcaniclastic and granitic terrains

Project Description: 

Measure elemental inputs in rain, and outputs in streams. Weekly sampling from two bedrock types, with analysis of sediments, particulate carbon and nitrogen, and dissolved nutrients, organic matter, Si, major cations, and major anions. Quarterly sampling of dissolved organic matter quality (fluorescence excitation-emission scans). Sites specific to the CZO project include rain chemistry at East Peak, and stream chemistry in Icacos and Guaba.

Research Location: 
Core Area(s) and/or Keywords: 

rain stream chemistry biogeochemistry input output export

Linkages between redox processes and surface soil carbon cycling

Project Description: 

Humid tropical soils are characterized by fluctuating oxygen (O2) concentrations and periodic anaerobosis caused by high soil moisture and biological O2 demand. Iron (Fe) oxides provide an abundant electron acceptor for microbial metabolism under anaerobic conditions. Here, we explored interactions between Fe redox cycling and carbon (C) pools and fluxes.
Key Questions:
1. Does spatial and temporal variation in moisture, O2 availability, and Fe reduction control soil C pools?
2. Does O2 limitation constrain organic matter decomposition via microbial enzymes?

Research Location: 
Core Area(s) and/or Keywords: 

redox, carbon dioxide, methane, nitrous oxide, extracellular enzyme, iron, sulfur, manganese, nitrogen, soil moisture,

Parent Material and Topography Determine Soil Phosphorus Status in the Luquillo Mountains of Puerto Rico

Project Description: 

We collected soils from both Icacos and Bisley, in different topographic positions, and analyzed them for phosphorus content.

Abstract from the paper listed below Mage & Porder 2013.

Research Location: 
Core Area(s) and/or Keywords: 

Soil, phosphorus, topography, rock type, granodiorite, volcaniclastic, nutrients, parent material

Relevant Tools, Models or Publication Downloads: 

Modelling of soils in Luquillo Mountains

Project Description: 

Sue Brantley, Heather Buss, Katya Bazilevskaya, Lixin Jin

A reactive transport code will be used to model regolith development on one or more of the three relevant lithologies. The model will include flow, diffusion, and chemical reaction.

Research Location: 

Denudation and corestone evolution in the Luquillo mountains

Project Description: 

Sue Brantley, Katya Bazilevskaya, Heather Buss, Arjun Heimsath

Corestone size and distribution will be mapped on the three relevant lithologies, diorite, volcaniclastics, and hornfels. These size and distribution data will be related to denudation of the landscape as measured using cosmogenic isotopes.

Weathering of a chronosequence of landslides

Project Description: 

Sue Brantley, Heather Buss

We will analyze soils on five landslides that constitute a chronosequence of landslide events. These soils were sampled by Art Johnson as published in Zarin et al. (xxx): we will analyze the same samples for chemistry and mineralogy with respect to depth. We will also revisit these same landslides to resample and reanalyze. The goal is to understand how landslides affect weathering and solute fluxes in the Luquillo mountains.

Syndicate content