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Biogeochemical processes in northern peatland ecosystems are influenced by seasonal temperature fluctuations that are changing with the climate. Methylmercury (MeHg), commonly produced in peatlands, affects downstream waters; therefore, it is important to understand how temperature transitions affect mercury (Hg) dynamics. We investigated how the freeze–thaw cycle influences belowground peat pore water total Hg (THg), MeHg, and dissolved organic carbon (DOC). Four large, intact peat columns were removed from an ombrotrophic peat bog and experimentally frozen and thawed. Pore water was sampled across seven depths in the peat columns during the freeze–thaw cycle and analyzed for THg, MeHg, and DOC concentrations. Freezing results showed increased concentrations of THg below the ice layers and limited change in MeHg concentrations. During thawing, THg concentrations significantly increased, whereas MeHg concentrations decreased. Limited bromide movement and depth decreases in THg and DOC concentrations were associated with increased bulk density and degree of humification in the peat. The experiment demonstrates the effects of the freeze–thaw cycle on Hg concentrations in northern peatlands. Changes to freeze–thaw cycles with climate change may exacerbate Hg cycling and transport processes in peatland environments. [ABSTRACT FROM AUTHOR]

Wildland fire can alter mercury (Hg) cycling on land and in adjacent aquatic environments. In addition to enhancing local atmospheric Hg redeposition, fire can influence terrestrial movement of Hg and other elements into lakes via runoff from burned upland soil. However, the impact of fire on water quality and the accumulation of Hg in fish remain equivocal. We investigated the effects of fire--specifically, a low-severity prescribed fire and moderate-severity wildfire--on young-of-the-year yellow perch (Perca flavescens) and lake chemistry in a small remote watershed in the Boundary Waters Canoe Area Wilderness in northeastern Minnesota. We used a paired watershed approach: the fire-affected watershed was compared with an adjacent, unimpacted (reference) watershed. Prior to fire, upland organic horizons in the two study watersheds contained 1549 μg Hg m-2 on average. Despite a 19% decrease in upland organic horizon Hg stocks due to the moderate severity wildfire fire, fish Hg accumulation and lake productivity were not affected by fire in subsequent years. Instead, climate and lake water levels were the strongest predictors of lake chemistry and fish responses in our study lakes over 9 yr. Our results suggest that low- to moderate-severity wildland fire does not alter lake productivity or Hg accumulation in young-of-the-year yellow perch in these small, shallow lakes in the northern deciduous and boreal forest region. [ABSTRACT FROM AUTHOR]

Many carbon dioxide (CO2) emission-reduction strategies currently under consideration rely on terrestrial carbon (C) sequestration to offset substantial proportions of CO2 emissions. We estimated C sequestration rates and potential land areas for a diverse array of land-cover changes in the Upper Midwest of the US, a "best case" region for this study because of its relatively modest CO2 emissions and the large areas of cropland potentially available for conversion. We then developed scenarios that apply some of the most widespread mitigation strategies to the region: the first, which aimed to offset 29% of regional CO2 emissions, required the unrealistic loss of two-thirds of working cropland; the second, which estimated the emission offset attainable by conversion of 10% of harvested croplands (5.8% of the US total), resulted in <5% CO2 emissions reduction for the region (<1.1% of total US emissions). There is limited capacity for terrestrial C sequestration, so strategies should aim to directly reduce CO2 emissions to mitigate rising atmospheric CO2 concentrations. [ABSTRACT FROM AUTHOR]

Evaluates the nutrient supply and neutralizing value of alfalfa stem gasification ash. Increase of soil hydrogen-ion concentration with ash application on soils; Effect of ash application on ammonium acetate-exchangeable nutrients; Recovery on the slopes of cations in plant and soil.

Presents a study which was conducted on the adsorption features of the FD and C Blue no.1 food to characterize the effects of flow velocity. Materials and method used in the study; Results and discussion of the study; Conclusions based on the results.

A response by Cinzia Fissore and his colleagues to a letter to the editor about their article related to the impact of prairie restoration and afforestation on cropland in the Upper Midwest of the U.S., in the October 2010 issue is presented.