ARSENIC MOBILIZATION AND TRANSPORT IN: Weathered LF...Controlled Simulation of Field Weathering...
1
ARSENIC MOBILIZATION AND TRANSPORT IN: HYDROGEOCHEMICALLY DYNAMIC RECHARGE ZONES VERSUS STEADY-STATE DEEP WATER-BEARING CONDUITS IN THE LOCKATONG (LF) AND PASSAIC (PF) FORMATION AQUIFERS IN THE NEWARK BASIN, NEW JERSEY Michael Serfes, Ph.D., PG | Solution Geosciences LLC. | Bethlehem, PA 18018 | [email protected] Problem / Questions Up to 254 μg/l As occurs in potable wells in the Newark Basin: Lockatong (LF) & Passaic (PF) Formations. 1. What are the most biogeochemically significant As mobilization zones in each formation? a. Do surface excavations enhance As mobilization? Arsenic Mobilization Hypotheses LF and PF aquifers are naturally enriched in As: major mobilization zones? 1. LF (pyritic black/gray argillite): pyrite oxidation in GW recharge zone? 2. LF: sulfide-arsenide substitution in pyrite in deeper water-bearing zone? 3. PF (hematite mudstone): adsorption-desorption in GW recharge zone? 4. PF: adsorption-desorption in deeper water-bearing zone? Project Overview The Newark Basin (NB) is a Mesozoic aged half graben that filled upward with non- marine: (1) fluvial deltaic - Stockton Formation, (2) deep lake - LF, and (3) shallow lake playa – PF, now comprising the 3 major aquifers. Only the LF and PF aquifer matrix are enriched in arsenic and have natural aqueous arsenic issues. These formations strike ~ NE and dip ~ 12 degrees NW and the LF and PF are bedding confined, multi-layered, leaky aquifer systems. Much work to evaluate the sources and mobilization mechanisms of arsenic in the LF and PF aquifers has been conducted (Serfes, 2005; Zhu and others 2008; Serfes and others, 2010). Recent concerns about the significance of As mobilization from non-imported backfill to be used in a linear trench excavation transecting the LF and PF have been evaluated. Column leach testing of LF and PF rock particles used EPA Method 1627 (USEPA, 2011; Serfes, 2016). These test results not only provided information addressing the key concern(s), but also indirectly about what the major zones of As mobilization in these aquifers are. The EPA-1627 methodology and an improved biogeochemical model of As mobilization in the NB follows. Geologic Setting / Stratigraphic Column As in Wells / Geology / Trench Transect Procedure: EPA Method 1627 Selected Representative Samples 3-LF from outcrops (microbial active), and, 3- PF from rock core borings (locations mapped above) LF whole As: 5 – 15 mg/kg PF whole As: <5 - 8 mg/kg Step 1 Preparation of Samples for Kinetic Testing using 2-inch columns Crushed 2 kg to method specific particle size distribution (PSD) range: < 0.25 mm to ~ 10 mm Note: 6-inch columns also used with scaled up PSD: (As in leachate < 2-inch) Step 2 Controlled Simulation of Field Weathering Conditions Trench assumptions: (1) humid with intermittent saturations, (2) CO 2 rich Columns: humidified air 6- days (1 Lpm, 10% CO 2 ), 24-hour saturation/week, over 12-weeks Step 3 Leachate Collection and Analysis Volume in-out, pH, alkalinity, acidity Filtered leachate (0.45 micron) samples sent to certified laboratory for analysis: As, Ca, Mg, SO 4 -2 , Fe and Mn Step 4 12-Week Test Results: (2-Inch Columns) FeS 2 / As, SO 4 -2 & Fe in Leachate All leachate: • Circum-neutral pH (6.5- 8.5): (CaCO 3 in LF & PF) • Ambient dissolved O 2 LF Samples: • ML-DUP-2 has highest As leachate concentrations • Pyrite oxidizes, HFO forms • Maximum acidity of 3 mg/l as CaCO 3 • Therefore no ARD PF Samples: • B-50-2 has highest As concentrations Conceptual Model / Conclusions Arrows (left): redox range in LF and PF: surface (top) to deep aquifer Lockatong Formation (LF): shallow recharge area to deep GW flow; 1. Shallow Oxic Zone: Unsaturated, pyrite oxidation, HFO formation, SO 4 -2 released & mobile, circum-neutral pH, As (V) adsorbed has limited mobility. No acid-rock drainage (ARD) issues in this CaCO 3 rich rock. 2. Intermediate Depth Suboxic Zone: Mostly saturated, pyrite somewhat oxidized, HFO formation, SO 4 -2 released & mobile, Mn +2 mobile, circum-neutral pH, As adsorbed as As (V) has limited mobility 3. Deep Anoxic Zone: Pyrite mostly stable, HFO mostly absent, circum-neutral pH, Fe +2 mobile, sulfate-sulfide transition (H 2 S) followed by sulfide-arsenide substitution in pyrite, mostly As (III) very mobile. As (III) > As (V) mostly mobilized in deeper anoxic zone of the LF. Potable wells intersecting As- enriched permeable beds (WBZs) yield high As concentrations. Passaic Formation (PF): shallow recharge area to deep GW flow: • Oxic Zone: dissolved O 2 decreases downward, pH increases, As (V) increases with pH: As (V) mostly mobilized in deeper GW with pH ~ 8.0. Potable wells intersecting As-enriched beds (WBZs) yield high As concentrations in PF. • Suboxic/anoxic only where gray/black beds occur (see stratigraphic section) Unsaturated areas (most): Non-imported LF and PF backfill in this oxic zone will release limited dissolved As (V) during the labile phase. Concentrations quickly return to background levels. The limited initial As (V) release is predictably insignificant to downgradient groundwater quality in both LF and PF (adsorption-dilution). References Borch, T., Kretzshamar, R., Kappler, A., Van Cappellen, P., Ginder-Vogel, M., Voegelin, A., Campbell, K., 2010, Biogeochemical Redox Processes and their Impact on Contaminant Dynamics: Environmental Science and Technology, v. 44, p. 15-23. Olsen, P.E., Kent, D.V., Cornet, B., Witte W.K., and Schlishe, R.W, 1996, High– resolution stratigraphy of the Newark rift basin (early Mesozoic, eastern North America): GSA Bulletin, v. 108, no. 1, p. 40-77. Schlische, R.W., Withjack, M.O., and Olsen, P.E., 2002, Relative timing of CAMP, rifting, continental breakup, and inversion: tectonic significance, in Hames, W.E., McHone, G.C., Renne, P.R., and Ruppel, C.R., eds., The Central Atlantic Magmatic Province: Insights from Fragments of Pangea: American Geophysical Union Monograph 136, p. 33-59. Serfes, M. E., 2005, Arsenic occurrence, sources, mobilization, transport and prediction in the major bedrock aquifers of the Newark Basin: Ph.D. Dissertation, Rutgers University, New Brunswick, NJ, 122 pp. Serfes, M.E., Herman, G.C., Spayd, S.E., and Reinfelder, J., 2010, Sources, Mobilization and Transport of arsenic in groundwater in the Passaic and Lockatong Formations of the Newark Basin: New Jersey Geological Survey Bulletin 77, Chapter E. 44p. Serfes, M.E. 2016. Final Report of U.S. EPA Method 1627 Kinetic and HDD Leach Test Results and Implications for Arsenic Mobilization Related to the Proposed PennEast Pipeline. Prepared for: Hatch Mott MacDonald, Inc. for PennEast Pipeline: Draft EIS: Attachment 2-1 – Arsenic Study Report. USEPA, 2011, Method 1627: Kinetic Test Method for the Prediction of Mine Drainage Quality. Zhu W., Young, L.Y., Yee N., Serfes, M.E., Rhine D. and Reinfelder J.R. , 2008, Sulfide-driven arsenic mobilization from arsenopyrite and black shale pyrite, Geochimica et Cosmochimica Acta, Volume 72, Issue 21, November 2008, Pages 5243-5250. Solution Geosciences, LLC Veteran Owned Small Business Bethlehem, PA 18018 Lockatong Formation Samples: pyrite in argillite was oxidized Passaic Formation (B-50-2): highest dissolved As concentrations Middle Lockatong Formation Sample (ML-DUP-2): Leachate has highest dissolved As concentrations (LF) (PF) Labile phase: freshly broken rough surfaces very reactive (active weathering) Pyrite oxidation phase: FeS 2 oxidizes, HFO forms (As sequestered, trapped) Background Phase: LF and PF non-imported fill becomes less reactive. FeS 2 (s) + 15/4 O 2 + 7/2 H 2 O → 4H + + 2(SO) -2 4 + Fe(OH) 3 (s) Left: NJ Private Well Testing Act data shows density of potable wells > 5 µg/l As, NJ MCL (2x2 mile cells with at least 10 PWs per). (Note: As percentiles in 20 shallow monitor wells in area: 25 th = 0.5 µg/l, median = 1.4 µg/l and 75 th = 2.5 µg/l) Stratigraphic column of NB rocks by Olsen and others (1996). Some beds are more As-enriched than others and wells that intersect them, if WBZs, can have unacceptable As concentration. CaCO 3 in LF & PF yield a circum-neutral pH O 2 -rich precipitation Ground Surface General Trench Backfill Range Weathered LF HFO after pyrite PF Un-weathered LF (As-rich pyrite) PF LF SF As Rich Newark Basin (Redox ladder at pH 7.0: Borch and others, 2010) PF LF http://www.nj.gov/dep/watersupply/pw_pwta.htm l ~ Linear trench transect
Transcript of ARSENIC MOBILIZATION AND TRANSPORT IN: Weathered LF...Controlled Simulation of Field Weathering...
ARSENIC MOBILIZATION AND TRANSPORT IN:
HYDROGEOCHEMICALLY DYNAMIC RECHARGE ZONES VERSUS STEADY-STATE DEEP WATER-BEARING CONDUITS IN THE LOCKATONG (LF) AND PASSAIC (PF) FORMATION AQUIFERS IN THE NEWARK BASIN, NEW JERSEY
Michael Serfes, Ph.D., PG | Solution Geosciences LLC. | Bethlehem, PA 18018 | [email protected]
Problem / QuestionsUp to 254 μg/l As occurs in potable wells in the Newark Basin: Lockatong (LF) & Passaic (PF) Formations. 1. What are the most biogeochemically significant As
mobilization zones in each formation?a. Do surface excavations enhance As mobilization?
Arsenic Mobilization HypothesesLF and PF aquifers are naturally enriched in As: major mobilization zones?1. LF (pyritic black/gray argillite): pyrite oxidation in GW recharge zone?2. LF: sulfide-arsenide substitution in pyrite in deeper water-bearing zone?3. PF (hematite mudstone): adsorption-desorption in GW recharge zone?4. PF: adsorption-desorption in deeper water-bearing zone?
Project OverviewThe Newark Basin (NB) is a Mesozoic aged half graben that filled upward with non-marine: (1) fluvial deltaic - Stockton Formation, (2) deep lake - LF, and (3) shallow lake playa – PF, now comprising the 3 major aquifers. Only the LF and PF aquifer matrix are enriched in arsenic and have natural aqueous arsenic issues. These formations strike ~ NE and dip ~ 12 degrees NW and the LF and PF are bedding confined, multi-layered, leaky aquifer systems. Much work to evaluate the sources and mobilization mechanisms of arsenic in the LF and PF aquifers has been conducted (Serfes, 2005; Zhu and others 2008; Serfes and others, 2010). Recent concerns about the significance of As mobilization from non-imported backfill to be used in a linear trench excavation transecting the LF and PF have been evaluated. Column leach testing of LF and PF rock particles used EPA Method 1627 (USEPA, 2011; Serfes, 2016). These test results not only provided information addressing the key concern(s), but also indirectly about what the major zones of As mobilization in these aquifers are. The EPA-1627 methodology and an improved biogeochemical model of As mobilization in the NB follows.
Geologic Setting / Stratigraphic Column
As in Wells / Geology / Trench Transect
Procedure: EPA Method 1627
Selected Representative Samples
3-LF from outcrops (microbial active), and, 3-PF from rock core borings(locations mapped above)LF whole As: 5 – 15 mg/kgPF whole As: <5 - 8 mg/kg
Step 1
Preparation of Samples for Kinetic Testing using
2-inch columnsCrushed 2 kg to method
specific particle size distribution (PSD) range:
< 0.25 mm to ~ 10 mmNote: 6-inch columns also used with scaled up PSD: (As in leachate < 2-inch)
Step 2
Controlled Simulation of Field Weathering
ConditionsTrench assumptions: (1) humid with intermittent
saturations, (2) CO2 richColumns: humidified air 6-days (1 Lpm, 10% CO2), 24-hour saturation/week,
over 12-weeks
Step 3
Leachate Collection and Analysis
Volume in-out, pH, alkalinity, acidity
Filtered leachate (0.45 micron) samples sent to certified laboratory for analysis: As, Ca, Mg,
SO4-2, Fe and Mn
Step 4
12-Week Test Results: (2-Inch Columns)
FeS2 / As, SO4-2 & Fe in Leachate
All leachate: • Circum-neutral pH (6.5-
8.5): (CaCO3 in LF & PF)• Ambient dissolved O2
LF Samples: • ML-DUP-2 has highest
As leachate concentrations
• Pyrite oxidizes, HFO forms
• Maximum acidity of 3 mg/l as CaCO3
• Therefore no ARDPF Samples: • B-50-2 has highest As
concentrations
Conceptual Model / ConclusionsArrows (left): redox range in LF and PF: surface (top) to deep aquifer
Lockatong Formation (LF): shallow recharge area to deep GW flow;
1. Shallow Oxic Zone: Unsaturated, pyrite oxidation, HFO formation, SO4-2 released
& mobile, circum-neutral pH, As (V) adsorbed has limited mobility. No acid-rock drainage (ARD) issues in this CaCO3 rich rock.
2. Intermediate Depth Suboxic Zone: Mostly saturated, pyrite somewhat oxidized, HFO formation, SO4
-2 released & mobile, Mn+2 mobile, circum-neutral pH, As adsorbed as As (V) has limited mobility
3. Deep Anoxic Zone: Pyrite mostly stable, HFO mostly absent, circum-neutral pH, Fe+2 mobile, sulfate-sulfide transition (H2S) followed by sulfide-arsenide substitution in pyrite, mostly As (III) very mobile. As (III) > As (V) mostly mobilized in deeper anoxic zone of the LF. Potable wells intersecting As-enriched permeable beds (WBZs) yield high As concentrations.
Passaic Formation (PF): shallow recharge area to deep GW flow:
• Oxic Zone: dissolved O2 decreases downward, pH increases, As (V) increases with pH: As (V) mostly mobilized in deeper GW with pH ~ 8.0. Potable wells intersecting As-enriched beds (WBZs) yield high As concentrations in PF.
• Suboxic/anoxic only where gray/black beds occur (see stratigraphic section)
Unsaturated areas (most): Non-imported LF and PF backfill in this oxic zone will release limited dissolved As (V) during the labile phase. Concentrations quickly return to background levels. The limited initial As (V) release is predictably insignificant to downgradient groundwater quality in both LF and PF (adsorption-dilution).
ReferencesBorch, T., Kretzshamar, R., Kappler, A., Van Cappellen, P., Ginder-Vogel, M., Voegelin, A., Campbell, K., 2010, Biogeochemical Redox Processes and their Impact on Contaminant Dynamics: Environmental Science and Technology, v. 44, p. 15-23.
Olsen, P.E., Kent, D.V., Cornet, B., Witte W.K., and Schlishe, R.W, 1996, High– resolution stratigraphy of the Newark rift basin (early Mesozoic, eastern North America): GSA Bulletin, v. 108, no. 1, p. 40-77.
Schlische, R.W., Withjack, M.O., and Olsen, P.E., 2002, Relative timing of CAMP, rifting, continental breakup, and inversion: tectonic significance, in Hames, W.E., McHone, G.C., Renne, P.R., and Ruppel, C.R., eds., The Central Atlantic Magmatic Province: Insights from Fragments of Pangea: American Geophysical Union Monograph 136, p. 33-59.
Serfes, M. E., 2005, Arsenic occurrence, sources, mobilization, transport and prediction in the major bedrock aquifers of the Newark Basin: Ph.D. Dissertation, Rutgers University, New Brunswick, NJ, 122 pp.
Serfes, M.E., Herman, G.C., Spayd, S.E., and Reinfelder, J., 2010, Sources, Mobilization and Transport of arsenic in groundwater in the Passaic and LockatongFormations of the Newark Basin: New Jersey Geological Survey Bulletin 77, Chapter E. 44p.
Serfes, M.E. 2016. Final Report of U.S. EPA Method 1627 Kinetic and HDD Leach Test Results and Implications for Arsenic Mobilization Related to the Proposed PennEast Pipeline. Prepared for: Hatch Mott MacDonald, Inc. for PennEast Pipeline: Draft EIS: Attachment 2-1 – Arsenic Study Report.
USEPA, 2011, Method 1627: Kinetic Test Method for the Prediction of Mine Drainage Quality.
Zhu W., Young, L.Y., Yee N., Serfes, M.E., Rhine D. and Reinfelder J.R. , 2008, Sulfide-driven arsenic mobilization from arsenopyrite and black shale pyrite, Geochimica et Cosmochimica Acta, Volume 72, Issue 21, November 2008, Pages 5243-5250.
Solution Geosciences, LLC Veteran Owned Small Business Bethlehem, PA 18018
Lockatong Formation Samples: pyrite in argillite was oxidized
Passaic Formation (B-50-2): highest dissolved As concentrations
Middle Lockatong Formation Sample (ML-DUP-2):Leachate has highest dissolved As concentrations
(LF) (PF)
Labile phase: freshly broken rough surfaces very reactive (active weathering)Pyrite oxidation phase: FeS2 oxidizes, HFO forms (As sequestered, trapped)Background Phase: LF and PF non-imported fill becomes less reactive.
FeS2 (s) + 15/4 O2 + 7/2 H2O → 4H+ + 2(SO) -24 + Fe(OH)3 (s)
Left: NJ Private Well Testing Act data shows density of potable wells > 5 µg/l As, NJ MCL (2x2 mile cells with at least 10 PWs per). (Note: As percentiles in 20 shallow monitor wells in area: 25th = 0.5 µg/l, median = 1.4 µg/l and 75th = 2.5 µg/l)
Stratigraphic column of NB rocks by Olsen and others (1996). Some beds are more As-enriched than others and wells that intersect them, if WBZs, can have unacceptable As concentration. CaCO3 in LF & PF yield a circum-neutral pH
O2-rich precipitation
Ground Surface
GeneralTrenchBackfillRange
Weathered LFHFO after pyrite
PFUn-weathered LF(As-rich pyrite)
PF
LF
SF
AsRich
Newark Basin
(Redox ladder at pH 7.0: Borch and others, 2010)
PFLF
http://www.nj.gov/dep/watersupply/pw_pwta.html
~ Linear trench transect
![Lim et al, Supplemental Figure S1. 01.55.07.0105010015020030040050000 Arsenic Plant height (Cm) As[μM] b/c g f e d c/d a/b a c/d a a/b Cadmium 01.55.07.0105010015020030040050000.](https://static.fdocument.org/doc/165x107/56649da95503460f94a9763a/lim-et-al-supplemental-figure-s1-0155070105010015020030040050000-arsenic.jpg)
