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Papers by Jennifer Parker
Water Air and Soil Pollution, 2002
Recent concerns about climate change and atmospheric greenhousegas concentrations have demonstrat... more Recent concerns about climate change and atmospheric greenhousegas concentrations have demonstrated the importance ofunderstanding ecosystem C source/sink relationships. Soilorganic matter fractionation was carried out in three paired,forested watershed sites where one of each watershed pairrepresented a different ecosystem perturbation. Theperturbations were 8 years of experimental N amendments at theBear Brook Watershed in Maine (BBWM), a 50 year old intensewildfire and
Environmental Monitoring and Assessment, 2006
Page 1. MAINE AGRICULTURAL AND FOREST EXPERIMENT STATION The University of Maine February 2001 Te... more Page 1. MAINE AGRICULTURAL AND FOREST EXPERIMENT STATION The University of Maine February 2001 Technical Bulletin 178 ISSN 10701524 Methods for Evaluating Carbon Fractions in Forest Soils: A Review Jennifer L. Evans Ivan J. Fernandez Lindsey E. Rustad ...
Soil Science Society of America Journal, 2001
Van Wagner (1991) predicted a 50% increase in fire (406 g C kg Ϫ1 soil, 24 Mg C ha Ϫ1 ) than the ... more Van Wagner (1991) predicted a 50% increase in fire (406 g C kg Ϫ1 soil, 24 Mg C ha Ϫ1 ) than the reference (442 g C kg Ϫ1 frequency in the boreal and subboreal forests in Canada soil, 39 Mg C ha Ϫ1 ) after 17 yr. All perturbations studied were associif the concentration of atmospheric CO 2 doubled. Inated with lower forest-floor C pools.
Environmental Monitoring and Assessment, 2007
This paper is an overview of this special issue devoted to watershed research in Acadia National ... more This paper is an overview of this special issue devoted to watershed research in Acadia National Park (Acadia NP). The papers address components of an integrated research program on two upland watersheds at Acadia NP, USA (44°20 0 N latitude; 68°15 0 E longitude). These watersheds were instrumented in 1998 to provide a long-term foundation for regional ecological and watershed research. The address research questions about mercury, acid rain, and nitrogen saturation developed from prior research. The project design was based on natural differences in forests and soils induced by an intense wildfire in one watershed in 1947. There is no evidence of fire in the reference watershed for several hundred years. We are testing hypotheses about controls on surface water chemistry, and bioavailability of contaminants in the contrasting watersheds. The unburned 47-ha Hadlock Brook watershed is 70% spruce-fir mature conifer forest. In contrast, burned 32-ha Cadillac Brook watershed, 4 km northeast of the Hadlock watershed, is 20% regenerating mixed northern hardwoods and 60% shrub/rocky balds. Differences in atmospheric deposition are controlled primarily by forest stand composition and age. The watersheds are gauged and have water chemistry stations at 122 m (Cadillac) and 137 m (Hadlock); watershed maximum elevations are 468 and 380 m, respectively. The stream water chemistry patterns reflect, in part, the legacy of the intense fire, which, in turn, controls differences in forest vegetation and soil characteristics. These factors result in higher nitrogen and mercury flux from the unburned watershed, reflecting differences in atmospheric deposition, contrasting ecosystem pools of nitrogen and mercury, and inferred differences in internal cycling and bioavailabilty.
Although researchers today generally employ appropriate techniques for the storage and preservati... more Although researchers today generally employ appropriate techniques for the storage and preservation of aqueous samples for ambient-level mercury (ppb) speciation, these methods continue to be poorly documented. Numerous experiments were thus conducted to investigate the effects of acidification and bottle type on holding time for various mercury species [elemental mercury (Hg 0 ), ionic mercury (Hg(II)), dimethyl mercury (DMHg), monomethyl mercury (MMHg), and dissolvedto-particulate ratio] as well as total mercury (THg). We documented that THg is stable for at least 300 days when stored at 0.4-0.5% acidity in either Teflon or glass bottles. In cases where THg is adsorbed to bottle walls, the addition of BrCl at least 24 h before analysis allowed all Hg to be quantitatively recovered. Polyethylene bottles allowed diffusion of Hg 0 through the bottle walls to or from the sample, depending on the Hg concentration of the sample and storage atmosphere. MMHg in freshwater samples can be stored refrigerated and unacidified for days to weeks with no observed degradation of MMHg. For long-term storage (at least 250 days), samples should be acidified with 0.4% HCl (v/v) and kept in the dark to avoid photodegradation (approximate t 1/2 =6 months). For saltwater samples, preservation with 0.2% (v/v) H 2 SO 4 is preferred to avoid exceeding the optimal chloride concentration if the distillation procedure is used for MMHg determination. For volatile species (Hg 0 and DMHg), samples should be collected in completely full glass bottles with Teflon-lined caps, as these species are lost rapidly (t 1/2 =10-20 h) from Teflon and polyethylene bottles. Because acids can enhance the rapid oxidation of volatile species, these samples should be stored refrigerated and unacidified and processed within 1-2 days if they cannot be purged and trapped in the field. Hg(II) and the dissolved-to-particulate ratio are more stable and can be stored for a period of days to weeks without preservation. D
Water Air and Soil Pollution, 2002
Recent concerns about climate change and atmospheric greenhousegas concentrations have demonstrat... more Recent concerns about climate change and atmospheric greenhousegas concentrations have demonstrated the importance ofunderstanding ecosystem C source/sink relationships. Soilorganic matter fractionation was carried out in three paired,forested watershed sites where one of each watershed pairrepresented a different ecosystem perturbation. Theperturbations were 8 years of experimental N amendments at theBear Brook Watershed in Maine (BBWM), a 50 year old intensewildfire and
Environmental Monitoring and Assessment, 2006
Page 1. MAINE AGRICULTURAL AND FOREST EXPERIMENT STATION The University of Maine February 2001 Te... more Page 1. MAINE AGRICULTURAL AND FOREST EXPERIMENT STATION The University of Maine February 2001 Technical Bulletin 178 ISSN 10701524 Methods for Evaluating Carbon Fractions in Forest Soils: A Review Jennifer L. Evans Ivan J. Fernandez Lindsey E. Rustad ...
Soil Science Society of America Journal, 2001
Van Wagner (1991) predicted a 50% increase in fire (406 g C kg Ϫ1 soil, 24 Mg C ha Ϫ1 ) than the ... more Van Wagner (1991) predicted a 50% increase in fire (406 g C kg Ϫ1 soil, 24 Mg C ha Ϫ1 ) than the reference (442 g C kg Ϫ1 frequency in the boreal and subboreal forests in Canada soil, 39 Mg C ha Ϫ1 ) after 17 yr. All perturbations studied were associif the concentration of atmospheric CO 2 doubled. Inated with lower forest-floor C pools.
Environmental Monitoring and Assessment, 2007
This paper is an overview of this special issue devoted to watershed research in Acadia National ... more This paper is an overview of this special issue devoted to watershed research in Acadia National Park (Acadia NP). The papers address components of an integrated research program on two upland watersheds at Acadia NP, USA (44°20 0 N latitude; 68°15 0 E longitude). These watersheds were instrumented in 1998 to provide a long-term foundation for regional ecological and watershed research. The address research questions about mercury, acid rain, and nitrogen saturation developed from prior research. The project design was based on natural differences in forests and soils induced by an intense wildfire in one watershed in 1947. There is no evidence of fire in the reference watershed for several hundred years. We are testing hypotheses about controls on surface water chemistry, and bioavailability of contaminants in the contrasting watersheds. The unburned 47-ha Hadlock Brook watershed is 70% spruce-fir mature conifer forest. In contrast, burned 32-ha Cadillac Brook watershed, 4 km northeast of the Hadlock watershed, is 20% regenerating mixed northern hardwoods and 60% shrub/rocky balds. Differences in atmospheric deposition are controlled primarily by forest stand composition and age. The watersheds are gauged and have water chemistry stations at 122 m (Cadillac) and 137 m (Hadlock); watershed maximum elevations are 468 and 380 m, respectively. The stream water chemistry patterns reflect, in part, the legacy of the intense fire, which, in turn, controls differences in forest vegetation and soil characteristics. These factors result in higher nitrogen and mercury flux from the unburned watershed, reflecting differences in atmospheric deposition, contrasting ecosystem pools of nitrogen and mercury, and inferred differences in internal cycling and bioavailabilty.
Although researchers today generally employ appropriate techniques for the storage and preservati... more Although researchers today generally employ appropriate techniques for the storage and preservation of aqueous samples for ambient-level mercury (ppb) speciation, these methods continue to be poorly documented. Numerous experiments were thus conducted to investigate the effects of acidification and bottle type on holding time for various mercury species [elemental mercury (Hg 0 ), ionic mercury (Hg(II)), dimethyl mercury (DMHg), monomethyl mercury (MMHg), and dissolvedto-particulate ratio] as well as total mercury (THg). We documented that THg is stable for at least 300 days when stored at 0.4-0.5% acidity in either Teflon or glass bottles. In cases where THg is adsorbed to bottle walls, the addition of BrCl at least 24 h before analysis allowed all Hg to be quantitatively recovered. Polyethylene bottles allowed diffusion of Hg 0 through the bottle walls to or from the sample, depending on the Hg concentration of the sample and storage atmosphere. MMHg in freshwater samples can be stored refrigerated and unacidified for days to weeks with no observed degradation of MMHg. For long-term storage (at least 250 days), samples should be acidified with 0.4% HCl (v/v) and kept in the dark to avoid photodegradation (approximate t 1/2 =6 months). For saltwater samples, preservation with 0.2% (v/v) H 2 SO 4 is preferred to avoid exceeding the optimal chloride concentration if the distillation procedure is used for MMHg determination. For volatile species (Hg 0 and DMHg), samples should be collected in completely full glass bottles with Teflon-lined caps, as these species are lost rapidly (t 1/2 =10-20 h) from Teflon and polyethylene bottles. Because acids can enhance the rapid oxidation of volatile species, these samples should be stored refrigerated and unacidified and processed within 1-2 days if they cannot be purged and trapped in the field. Hg(II) and the dissolved-to-particulate ratio are more stable and can be stored for a period of days to weeks without preservation. D