Paul A. Arp

New Evidence on Variations of Human Body Burden of Methylmercury from Fish Consumption

Epidemiologic studies commonly use mercury (Hg) level in hair as a valid proxy to estimate human exposure to methylmercury (MeHg) through fish consumption. This study presents the results yielded by a complete data set on fish consumption habits, Hg levels in edible fish resources, and corresponding Hg accumulation in hair, gathered in three distinct communities of eastern Canada. For one of these communities, the average hair Hg concentration was 14 times less than the expected value based on calculated daily oral exposure and current knowledge of MeHg metabolism. This finding could be explained by differences in specific genetic characteristics and/or interactive effects of other dietary components.

Mapping wetlands: A comparison of two different approaches for New Brunswick, Canada

Wetlands have an important role in ecosystem function and biodiversity. Effective management of wetlands requires accurate and comprehensive spatial information on location, size, classification, and connectivity in the landscape. Using a GIS, two provincial wetland maps were compared with regard to their areal correspondence across different ecoregions of New Brunswick. The first consisted of discrete wetland units (vector data) derived from aerial photo interpretation. The second consisted of wet areas modeled by a newly developed depth-to-water index with continuous coverage across the landscape (raster data). This index was derived from a digital elevation model and hydrographic data. The relative advantages and disadvantages of the two approaches were assessed. The two maps were generally consistent with most discrete wetland areas (51%–67%) embedded in the 0– 10 cm depth-to-water class, verifying the continuous modeling approach. The continuous model identified a larger wetland area. Much of this additional area consisted of riparian zones and numerous small wetlands (< 1 ha) that were not captured by aerial photo interpretation. Unlike the discrete map, the continuous model showed the hydrological connectivity of wetlands across the landscape. Both approaches revealed that topography was a major control on wetland distribution between ecoregions, with more wetland in ecoregions with flatter topography.

Using the Cartographic Depth-to-Water Index to Locate Small Streams and Associated Wet Areas across Landscapes

With increasing scarcity of natural resources, there is a need to provide resource managers and planners with maps that reliably inform about areas vulnerable to hydrological risks, including areas with ephemeral to intermittent flows. This paper demonstrates that the newly developed Wet-Areas Mapping (WAM) process using LiDAR-based point cloud data addresses some of these needs. This is done by portraying local flow patterns, soil drainage, soil moisture regimes and natural vegetation type across mapped areas in a numerically robust and consistent manner. As a result, WAM-derived maps are useful for surprise-free operations planning in several areas of natural resource planning (forestry, parks and recreation, oil and gas extraction, land reclamation), and also serve as field guides for locating and delineating flow channels, road-stream crossings, wet areas and wetlands.

Gaseous carbon dioxide and methane, as well as dissolved organic carbon losses from a small temperate wetland under a changing climate

Temperate forests can contain large numbers of wetlands located in areas of low relief and poor drainage. These wetlands can make a large contribution to the dissolved organic carbon (DOC) load of streams and rivers draining the forests, as well as the exchange of methane (CH4) and carbon dioxide (CO2) with the atmosphere. We studied the carbon budget of a small wetland, located in Kejimkujik National Park, Nova Scotia, Canada. The study wetland was the Pine Marten Brook site, a poor fen draining a mixed hardwood-softwood forest. We studied the loss of DOC from the wetland via the outlet stream from 1990 to 1999 and related this to climatic and hydrologic variables. We added the DOC export information to information from a previously published model describing CH4 and CO2 fluxes from the wetland as a function of precipitation and temperature, and generated a new synthesis of the major C losses from the wetland. We show that current annual C losses from this wetland amount to 0.6% of its total C mass. We then predicted that under climate changes caused by a doubling of atmospheric CO2 expected between 2040 and 2050, total C loss from the wetland will almost double to 1.1% of total biomass. This may convert this wetland from what we assume is currently a passive C storage area to an active source of greenhouse gases.

Simulations of pre- and post-harvest soil temperature, soil moisture, and snowpack for jack pine: comparison with field observations.

Quantifying temporal changes in soil temperature and moisture conditions is an important part of characterizing pre- and post-disturbance conditions that influence the health, productivity, and sustainability of forest ecosystems. In this paper, we present an experimental case study that was used to evaluate the ability of the forest hydrology model ForHyM2 to simulate field-observed changes in root-zone soil moisture and temperature, as well as snowpack depth, throughfall volume and forest floor percolate volume, for a jack pine (Pinus banksiana Lamb.) site in northeastern Ontario. The experiment refers to two post-harvest treatment factors, each involving two treatments: (a) blading (removing) or non-blading the forest floor and part of the mineral topsoil, (b) herbiciding or non-herbiciding. It was found that harvesting increased the average daily soil temperature by 4‐68C on all treatment plots during summer (5 cm soil depth). Blading increased the soil temperature further by 1‐28C. Herbiciding did not have significant effects on soil temperature. Eliminating competing forest vegetation significantly increased soil moisture level on the non-bladed treatment plots. The model simulations were based on daily precipitation (snow and rain), air temperature, and a few site descriptors such as longitude and latitude, soil depth, soil texture, and leaf area index. The resulting simulations compared well (graphically) with the pre- and post-harvest field observations regarding soil moisture, soil temperature, and snowpack water equivalents. Good graphical agreements suggest that the approach taken with this case study can be applied to the evaluation of soil moisture and temperature conditions to a variety of pre- and post-disturbance forest conditions. The results from the study would be useful for addressing below ground processes such as root growth, soil respiration, rate of organic matter decomposition, rate of soil weathering, nutrient cycling, etc., all of which strongly influence site productivity. # 2000 Elsevier Science B.V. All rights reserved.

Mercury in freshwater ecosystems of the Canadian Arctic: recent advances on its cycling and fate.

The Canadian Arctic has vast freshwater resources, and fish are important in the diet of many Northerners. Mercury is a contaminant of concern because of its potential toxicity and elevated bioaccumulation in some fish populations. Over the last decade, significant advances have been made in characterizing the cycling and fate of mercury in these freshwater environments. Large amounts of new data on concentrations, speciation and fluxes of Hg are provided and summarized for water and sediment, which were virtually absent for the Canadian Arctic a decade ago. The biogeochemical processes that control the speciation of mercury remain poorly resolved, including the sites and controls of methylmercury production. Food web studies have examined the roles of Hg uptake, trophic transfer, and diet for Hg bioaccumulation in fish, and, in particular, advances have been made in identifying determinants of mercury levels in lake-dwelling and sea-run forms of Arctic char. In a comparison of common freshwater fish species that were sampled across the Canadian Arctic between 2002 and 2009, no geographic patterns or regional hotspots were evident. Over the last two to four decades, Hg concentrations have increased in some monitored populations of fish in the Mackenzie River Basin while other populations from the Yukon and Nunavut showed no change or a slight decline. The different Hg trends indicate that the drivers of temporal change may be regional or habitat-specific. The Canadian Arctic is undergoing profound environmental change, and preliminary evidence suggests that it may be impacting the cycling and bioaccumulation of mercury. Further research is needed to investigate climate change impacts on the Hg cycle as well as biogeochemical controls of methylmercury production and the processes leading to increasing Hg levels in some fish populations in the Canadian Arctic.

Modeling snowpack and soil temperature and moisture conditions in a jack pine, black spruce and aspen forest stand in central Saskatchewan (BOREAS SSA)

Impacts of climate change on above- and below-ground heat and moisture conditions were modeled so that other impacts on, e.g., local carbon (C) and C-based pools for nutrients and pollutants such as Hg can be predicted reliably. This paper shows how the 199–-2003 data for the jack pine (jp; Pinus banksiana Lamb.), black spruce (bs; Picea mariana) and aspen (ta; Populus tremuloides) sites of the Southern Study Area of the BOREAS project were used to estimate some of the hydrothermal soil responses at these locations to daily variations in precipitation and air temperature. This was done by initializing and calibrating a forest hydrology model that has the capacity to simulate flow and retention of moisture and heat, as modified by canopy closure, ground cover, forest-floor depth, and soil composition. The calculations and data revealed strong but predictable site-specific differences in soil temperature and frost penetration (jp: 1–2 m > ta: 0.5–1 m > bs: 0–0.5 m), in soil moisture freezing (ta < bs < jp),...

Fog contributions to the water budget of forested watersheds in the Canadian Maritime Provinces: A generalized algorithm for low elevations

Abstract Fog contributes to the water budget of forested watersheds directly by water deposition, and indirectly by reducing potential and actual evapotranspiration. This study was designed to deve...

Modeling mass and nitrogen remaining in litterbags for Canadian forest and climate conditions

A new Forest Litter Decomposition Model (FLDM) is presented to simulate mass, N and carbon/nitrogen ratios (C/N) according to the 1992–1998 leaf litterbag data of the Canadian Intersite Decomposition Experiment (CIDET). This experiment involved 10 litter types, with litterbags placed on the ground of 18 upland and 3 wetland sites across Canada. The calibrated model based on first-order reaction kinetics calculates total mass, N concentration and C/N for each litter type and location using: three compartments (fast, slow, and very slow), four parameters for compartment initialization; three for compartment-based decay; three to assess the climate influence on decay; and one each to determine the rate o f N-mineralization and the final C/N ratio. With FLDM, the initial fast fraction is determined from the initial water-extractable and acid-hydrolyzable or acid-unhydrolyzable portions of the litter; the initial ash content determines the ratio between the slow and very slow fractions. Mean July and January a...

Methane and soil and plant community respiration from wetlands, Kejimkujik National Park, Nova Scotia: Measurements, predictions, and climatic change

A static, dark chamber technique was used weekly from mid-July to mid-November in 1995 and biweekly from mid-May to late November in 1996, to measure methane (CH4) flux and soil and plant community respiration of CO2 from 36 sites in two wetlands in Kejimkujik National Park in south-central Nova Scotia, Canada. Overall mean fluxes of CH4 were 43 mg m−2 d−1 in 1995 and 20 mg m−2 d−1 in 1996. Respiration rates were 5.1 g CO2 m−2 d−1 in 1995 and 3.2 g CO2 m−2 d−1 in 1996. Fluxes of CH4 and CO2 were related to microtopography and ecological grouping, depth to water table, and air and peat temperatures. Edge and hummock sites showed the lowest CH4 flux and the highest respiration rate, while pools showed the highest CH4 and lowest respiration rate. Gas emissions displayed a strong seasonal pattern with highest values occurring during the summer (June to August) and with a marked reduction in late fall. Depth to water table and air temperature explained 34 to 43% of the variance in CH4 flux and respiration from the sites over the 2 years (n = 666 to 824). We developed algorithms relating the daily mean flux of CH4 and respiration from the wetlands to an aspatial soil moisture, water table, and temperature model (ForHyM2) applied to the wetland basins. We then applied this model to calculated May to October fluxes of CH4 and CO2 from 1966 to 1998. We estimated that CH4 fluxes ranged from 2.8 to 7.4 g m−2, with a mean of 3.7 g m−2 and a standard deviation of 1.2 g m−2 over the 1966–1998 period. Respiration estimates ranged from 0.60 to 1.16 kg CO2 m−2, with a mean of 0.74 kg CO2 m−2 and a standard deviation of 0.11 kg CO2 m−2. Application of a 2xCO2 General Circulation Model scenario to temperature and precipitation for this part of eastern Canada resulted in increases of growing season CH4 emissions from 4.7 to 11.4 g m−2 and respiration from 0.77 to 1.32 kg CO2 m−2.