system. Another problem with this design was that winter freeze-thaw cycles
caused the PVC tubes to crack and leak.
To remedy the dual problems of isotopic fractionation due to evaporation in the
tubes and the cracking of the tubes in the winter, the precipitation collector system
was retrofitted in 2011. The new system still relied on the funnels at the surface to
collect the precipitation, but the funnels were drained into the cave via tubing to a
carboy fitted with an airlock. This system also included an isotopic control (Fig. 3,
bottom). Because the cave air temperature remains relatively constant (12–13
C)
over the year, the vessels did not experience freeze-thaw cycles. In addition, the
narrow range in temperature of the cave reduced sample evaporation.
3.3 Soil Water Monitoring
Soil water data were collected from 2009 to 2012 to examine the chemical characteristics of water entering the epikarst. Samples were collected from porous cup
tension lysimeters, installed at 1 m depths in three locations: the bottom of the
sinkhole containing the cave entrance, the surface overlying MS2, and the surface
overlying MS3. Lysimeters were sampled monthly by applying a vacuum to the
lysimeter using a handheld pump, waiting 2 h, then purging the lysimeter sample
with positive pressure applied using a handheld bicycle pump.
3.4 Cave Monitoring
Within the cave, instrumentation has been installed to collect nearly continuous
(10 min) measurements of dripwater rates, specific conductance, and temperature;
cave air temperature and relative humidity; and cave stream discharge, specific
conductance, and temperature. Dripwater rates and stream discharge data provide
critical information about recharge to the karst system, which is one of the focal
points of the James Cave research project. In addition to hydrologic characteristics,
the experimental apparatus was designed to allow for collection of dripwater and
stream samples for geochemical analysis.
Dripwater monitoring sites were installed where cave ceilings are within 15 m of
the cave surface, which is within the known vertical range of the epikarst observed
in most karst regions [28]. Data from a survey (see Fig. 3) was used to locate the
three dripwater sites (MS1, MS2, and MS3) and to determine the thickness of the
epikarst overlying the stations. Results show that MS1 and MS2 are 15 m apart,
located ~50 m west of the cave entrance. MS3 is ~60 m east of the cave entrance.
The sites are located far enough from the cave entrance that the influence of surface
environmental conditions is minimized. Depths of drip monitoring stations below
ground surface are 8 m (597 m above mean sea level (AMSL)) at MS1, 10.7 m
(595.1 m AMSL) at MS2, and 7 m (593 m AMSL) at MS3.
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M.E. Schreiber et al.
caused the PVC tubes to crack and leak.
To remedy the dual problems of isotopic fractionation due to evaporation in the
tubes and the cracking of the tubes in the winter, the precipitation collector system
was retrofitted in 2011. The new system still relied on the funnels at the surface to
collect the precipitation, but the funnels were drained into the cave via tubing to a
carboy fitted with an airlock. This system also included an isotopic control (Fig. 3,
bottom). Because the cave air temperature remains relatively constant (12–13
C)
over the year, the vessels did not experience freeze-thaw cycles. In addition, the
narrow range in temperature of the cave reduced sample evaporation.
3.3 Soil Water Monitoring
Soil water data were collected from 2009 to 2012 to examine the chemical characteristics of water entering the epikarst. Samples were collected from porous cup
tension lysimeters, installed at 1 m depths in three locations: the bottom of the
sinkhole containing the cave entrance, the surface overlying MS2, and the surface
overlying MS3. Lysimeters were sampled monthly by applying a vacuum to the
lysimeter using a handheld pump, waiting 2 h, then purging the lysimeter sample
with positive pressure applied using a handheld bicycle pump.
3.4 Cave Monitoring
Within the cave, instrumentation has been installed to collect nearly continuous
(10 min) measurements of dripwater rates, specific conductance, and temperature;
cave air temperature and relative humidity; and cave stream discharge, specific
conductance, and temperature. Dripwater rates and stream discharge data provide
critical information about recharge to the karst system, which is one of the focal
points of the James Cave research project. In addition to hydrologic characteristics,
the experimental apparatus was designed to allow for collection of dripwater and
stream samples for geochemical analysis.
Dripwater monitoring sites were installed where cave ceilings are within 15 m of
the cave surface, which is within the known vertical range of the epikarst observed
in most karst regions [28]. Data from a survey (see Fig. 3) was used to locate the
three dripwater sites (MS1, MS2, and MS3) and to determine the thickness of the
epikarst overlying the stations. Results show that MS1 and MS2 are 15 m apart,
located ~50 m west of the cave entrance. MS3 is ~60 m east of the cave entrance.
The sites are located far enough from the cave entrance that the influence of surface
environmental conditions is minimized. Depths of drip monitoring stations below
ground surface are 8 m (597 m above mean sea level (AMSL)) at MS1, 10.7 m
(595.1 m AMSL) at MS2, and 7 m (593 m AMSL) at MS3.
216
M.E. Schreiber et al.