Benthic Flux Chamber Methods Development Update ...
1
Benthic Flux Chamber Methods Development Update October 11, 2007
2
Outline of Discussion Background Results To Date Path Forward
3
BFC Program Objective -
Direct measurement of flux of THg, MeHg, Mn, and Fe from the dominant South River substrates so that their relative contributions of Hg to the surface water can be determined.
4
BFC Methods Development Efforts To Date: - FGCM Deposits (Mud) Study - Five locations were studied - SR-01, RRM-2.0, RRM-3.0, RRM-5.2, and RRM-13.1 - Rock Plate Study - Five locations were studied - SR-01, RRM-2.0, RRM-3.0, RRM-5.2, and RRM-13.1 - Embedded Gravel Study - Methods are being developed
5
Fine Grain Channel Margin (Mud) Study
[MeHg] ng/L
MeHg Flux at Exp. Study Reach RRM-5.2 (Deposit 3) 3.5 3.0 2.5 2.0
2
4.4 ng/m /hr
1.5 1.0 0.5 0.0 0 14:00
Data trends
2
56 ng/m /hr
Opaque Clear 1
2
3 4 Time (Hour)
5
6 18:00
• Data tends to be well behaved • As DO drops Mn & Fe flux generally increase
• MeHg varied by a factor of 10 & THg by 100 • Dissolution of minerals during diurnal cycling may account for some of the THg & MeHg • The BFC methods development for the FGCM deposits appears to be complete.
2
25
269.9 ng/m /hr
20 [THg] ng/L
• As Mn & Fe flux increase, MeHg & THg flux generally increase
THg Flux at Exp. Study Reach RRM-5.2 (Deposit 3)
15
2
23.9 ng/m /hr
10 Opaque 5
Clear
0 0 14:00
1
2
3 Time (Hour)
4
5
6 18:00
6
“Reality Check”: BFC Flux Vs SR Flux
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Rock Plate Study MeHg Flux, Rock Plates, September 2006 100
ng/m2 hr-1
80
Clear Opaque
60 40 20 0 RRM-2.0
Data trends • Data tends to be well behaved (THg?)
• The rock plates appear to effectively simulate the streambed (sediment & flora) • The BFC methods development for the rock plates appears to be complete
RRM-13.1
SR-01
140 120 100
ng/m2 hr-1
• MeHg varied by a factor of 2 & THg by 100
RRM-5.2
THg Flux, Rock Plates, September 2006
• DO was increasing in the Clear BFCs and relatively steady in the Dark BFCs • Dissolution of Fe & Mn was not observed
RRM-3.0
-20
Clear Opaque
80 60 40 20 0 -20
RRM-2.0
RRM-3.0
RRM-5.2
RRM-13.1
SR-01
8
“Reality Check”: Rock Plate Flux Vs SR Flux
9
Embedded Gravel Study
- Hyporheic flow
- The plates were anchored and grouted to the streambed - Rock Plate type BFCs were attached to the plate - A chloride tracer was injected into the BFC - Conductivity was measured using a YSI 556 conductivity probe, a YSI 556 flow through cell, and a peristaltic pump - The tracer was monitored over time to check the integrity of the grouted seal
10
Embedded Gravel Study
Chloride Tracer Results
Data trends: • Chloride data was well behaved • The attapulgite grout appears to effectively seal the plate to the streambed • The grout materials needs to tested for Hg adsorption / desorption – Dr Gill • Method development for the embedded gravel plate is on-going
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BFC Study Summary - BFCs are able to measure low level flux from the various SR substrates
Transparent BFC
- Data tends to be well behaved - Opaque BFCs can effectively shutdown photosynthetic DO production processes. - Diurnal effects and dissolution of mineral phases (Fe & Mn) may account for some of the THg and MeHg in surface water - The rock plates appear to effectively simulate the streambed - MeHg flux from the rock plates varied by a factor of 2 & THg by 100 - MeHg flux from the FGCM deposits varied by a factor of 10 & THg by 100
Opaque BFC
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South River BFC Efforts - Path Forward What? - FGCM (mud), Embedded Gravel, & Wetlands will be studied: - Study will be keyed with the Phase I - Year II Eco Study areas When? - Sampling will be done 3 to 4 times next year - Sampling will be done during the same time frame How? - Transparent and opaque BFCs will be deployed - The FCGM and embedded gravel study, but the wetland study may be separated
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Benthic Flux Chamber Update Questions ?
Benthic Flux Chamber Methods Development Update October 11, 2007
2
Outline of Discussion Background Results To Date Path Forward
3
BFC Program Objective -
Direct measurement of flux of THg, MeHg, Mn, and Fe from the dominant South River substrates so that their relative contributions of Hg to the surface water can be determined.
4
BFC Methods Development Efforts To Date: - FGCM Deposits (Mud) Study - Five locations were studied - SR-01, RRM-2.0, RRM-3.0, RRM-5.2, and RRM-13.1 - Rock Plate Study - Five locations were studied - SR-01, RRM-2.0, RRM-3.0, RRM-5.2, and RRM-13.1 - Embedded Gravel Study - Methods are being developed
5
Fine Grain Channel Margin (Mud) Study
[MeHg] ng/L
MeHg Flux at Exp. Study Reach RRM-5.2 (Deposit 3) 3.5 3.0 2.5 2.0
2
4.4 ng/m /hr
1.5 1.0 0.5 0.0 0 14:00
Data trends
2
56 ng/m /hr
Opaque Clear 1
2
3 4 Time (Hour)
5
6 18:00
• Data tends to be well behaved • As DO drops Mn & Fe flux generally increase
• MeHg varied by a factor of 10 & THg by 100 • Dissolution of minerals during diurnal cycling may account for some of the THg & MeHg • The BFC methods development for the FGCM deposits appears to be complete.
2
25
269.9 ng/m /hr
20 [THg] ng/L
• As Mn & Fe flux increase, MeHg & THg flux generally increase
THg Flux at Exp. Study Reach RRM-5.2 (Deposit 3)
15
2
23.9 ng/m /hr
10 Opaque 5
Clear
0 0 14:00
1
2
3 Time (Hour)
4
5
6 18:00
6
“Reality Check”: BFC Flux Vs SR Flux
7
Rock Plate Study MeHg Flux, Rock Plates, September 2006 100
ng/m2 hr-1
80
Clear Opaque
60 40 20 0 RRM-2.0
Data trends • Data tends to be well behaved (THg?)
• The rock plates appear to effectively simulate the streambed (sediment & flora) • The BFC methods development for the rock plates appears to be complete
RRM-13.1
SR-01
140 120 100
ng/m2 hr-1
• MeHg varied by a factor of 2 & THg by 100
RRM-5.2
THg Flux, Rock Plates, September 2006
• DO was increasing in the Clear BFCs and relatively steady in the Dark BFCs • Dissolution of Fe & Mn was not observed
RRM-3.0
-20
Clear Opaque
80 60 40 20 0 -20
RRM-2.0
RRM-3.0
RRM-5.2
RRM-13.1
SR-01
8
“Reality Check”: Rock Plate Flux Vs SR Flux
9
Embedded Gravel Study
- Hyporheic flow
- The plates were anchored and grouted to the streambed - Rock Plate type BFCs were attached to the plate - A chloride tracer was injected into the BFC - Conductivity was measured using a YSI 556 conductivity probe, a YSI 556 flow through cell, and a peristaltic pump - The tracer was monitored over time to check the integrity of the grouted seal
10
Embedded Gravel Study
Chloride Tracer Results
Data trends: • Chloride data was well behaved • The attapulgite grout appears to effectively seal the plate to the streambed • The grout materials needs to tested for Hg adsorption / desorption – Dr Gill • Method development for the embedded gravel plate is on-going
11
BFC Study Summary - BFCs are able to measure low level flux from the various SR substrates
Transparent BFC
- Data tends to be well behaved - Opaque BFCs can effectively shutdown photosynthetic DO production processes. - Diurnal effects and dissolution of mineral phases (Fe & Mn) may account for some of the THg and MeHg in surface water - The rock plates appear to effectively simulate the streambed - MeHg flux from the rock plates varied by a factor of 2 & THg by 100 - MeHg flux from the FGCM deposits varied by a factor of 10 & THg by 100
Opaque BFC
12
South River BFC Efforts - Path Forward What? - FGCM (mud), Embedded Gravel, & Wetlands will be studied: - Study will be keyed with the Phase I - Year II Eco Study areas When? - Sampling will be done 3 to 4 times next year - Sampling will be done during the same time frame How? - Transparent and opaque BFCs will be deployed - The FCGM and embedded gravel study, but the wetland study may be separated
13
Benthic Flux Chamber Update Questions ?
