Wednesday, July 24, 2013

LANL Synoptic Survey Team July 8th-17th, 2013

The LANL team (Jeff Heikoop, Heather Throckmorton, Garrett Altmann, Lily Cohen and Michael Hudak) continues its synoptic survey of water isotopes and chemistry to understand hydrologic pathways and transport in the BEO and surroundings.  This year, our focus has shifted from the polygon scale to larger drainage systems with particular emphasis on outlets from interlake areas and different aged drain thaw lake basins.  We are taking samples from surface water, the uppermost part of the active layer (0-4” from surface), and the active layer at the frost table (~11-16”) at 15 locations.  Sampling at the frost table has proven particularly difficult so we have employed arrays of rhizons to obtain sufficient water while minimizing disturbance (rhizons make a hole only about a finger’s width wide and can be removed immediately after sampling) (Photo 1).  The team also got to try out a system for filtering water samples through syringe filters (as small as 0.2 microns) aided by an electric caulking gun.  This has saved us hours of tedious and tiresome effort.  Our thanks to Marvin Gard whose ingenuity continues to amaze us!

The team is also testing Iron Reduction in Sediment (IRIS) probes to see if these might be a simple and cost-effective way to monitor redox changes on the broader landscape when collection of subsurface water samples may not be practical.  These probes consist of PVC coated with a ferrihydrite paint (photo 2).  Under reducing conditions iron on these probes will partially dissolve.  The amount of dissolution can be quantified by image analysis and related in a semi-quantitative fashion to redox conditions in the sediment.  IRIS probes have been approved by the EPA for demonstrating the presence of reducing soils for wetlands delineation. We are deploying these probes adjacent to our rhizon arrays so that we can compare out chemical results (a snapshot in time) to the time integrated signals provided by the IRIS probes, which will be pulled in September.  Image analysis will employ LANL’s GENIE technology.

In addition to synoptic survey activities, Liz Miller of LANL has also joined the team to perform a high-resolution differential GPS survey of troughs and flooded low-centered polygons to fill in gaps in LIDAR data.  This data will provide sub-centimeter elevation profiles for improved hydrologic modeling of the site (photo 3).

After rigorous days in the field, field team leader Heikoop was particularly impressed that his younger colleagues decided rooms in the Herman House should be segregated based on age with no doubt as to which room he belonged.  He also wants to thank Cathy Wilson for arranging to have high caliber athletes, including a champion ironwoman and world-class skier on the trip for him to keep pace with.  Fortunately everyone has provided plenty of calorie replenishment back home at ‘camp’ with their array of culinary talents. 

Photo 1: Rhizon array in ancient DTLB.

Photo 2: Mike Hudak holding IRIS probes prior to deployment in a young DTLB to the south of the BEO.

Photo 3: Liz Miller performing high-resolution GPS surveying.