Predicted acid mine drainage impacts to the Buckhannon River,WV, U.S.A.

This study was conducted to determine acid, Al, Cd, Cu, Fe, Mn, and Zn loads originating from coal mines in the Buckhannon River watershed in central West Virginia, U.S.A, and to predict the impacts of those loads should they enter the river as unneutralized acid mine drainage. Net alkaline loads at the river mouth would decrease from 3341 to 1014 and 7488 to 1463 kg day^?1 CaCO₃ during the summer and spring sampling periods, respectively, causing pH decrease below the level required for surviveal of warm water fish species in the affected study area and for a viable trout fishery in a 12 km segment of the river. Aluminum could have major impacts through much of the study area. Zinc could impact the existing cold water fishery and may cause deleterious effects to the warm water fishery. It was not possible to draw accurate conclusions about impacts of Fe because of the uncertainties of toxicity data and rates of oxidation. It appears that Cd and Cu would probably not impact the river. Manganese may cause a water treatment problem for the city of Buckhannon.     

Use of chemistry and stable sulfur isotopes to determine sources of trends in sulfate of Colorado lakes

The chemistry of lakes in the Mt. Zirkel Wilderness Area (MZWA) and the Weminuche Wilderness Area (WWA) of Colorado has been monitored since 1985. The initial results indicate that changes have occurred in the chemistry of some lakes in both areas. Increased concentration of sulfate in lakes may be related to increased atmospheric depositon of sulfate or to changes of sulfate released by weathering and to changing dilution of sulfate by snowmelt. Stable S isotopes seem to be capable of separating the fraction of change in sulfate that is related to atmospheric and watershed sources. Because of the short period of record, it is not possible to determine whether the changes are part of a long-term trend or are merely natural fluctuations about some baseline.     

Assessing Se cycling and toxicity in aquatic ecosystems

Toxic substances exert impacts on ecosystems at several levels: biogeochemical, toxicological, and populations/communities. Integrating exposure (biogeochemistry) and effects (toxicology) into an ecological context requires models as a necessary step to prediction and assessment of effects on populations and their interactions. To this end, research is being conducted to develop techniques for predicting the effects of Se on aquatic ecosystems. The objective is to develop mechanistic models to predict biogeochemical cycling, toxicological processes, and toxic effects on population and community dynamics. Earlier research demonstrated that different chemical forms of Se have different toxicological properties. Biogeochemical research culminated with a dynamic model of the Se cycle. In ongoing research, experiments are being conducted on microorganisms, phytoplankton, microzooplankton, zooplankton, benthic invertebrates, and fish to measure uptake, biotransformation, and depuration kinetics of different chemical forms of Se, transfer through the food web, and effects on growth, reproduction, community interactions, and survival. This information will provide the basis for the ecosystem effects model.     

Effects of Precipitation,Air Temperature,and Land Use on Organic Carbon Discharges from Rhode River Watersheds

We studied discharges of organic carbon from eight contiguous small watersheds on the Atlantic Coastal Plain in Maryland for up to 24 yr. Six of these watersheds were second or third orderwith mixed-land-use, while two were first order (one completely forested and one highly dominated by cropland). These watershedshave perched aquifers, so all groundwater discharges as well assurface runoff were measured at V-notch weirs and flumes, whichincluded volume-integrating flow-proportional samplers. Interannual variations in annual and seasonal precipitation during this study spanned approximately the range of 160 yr weather records in the region. Annual total organic carbon (TOC)area yields from the overall Rhode River watershed varied 8-fold, correlations with precipitation were highly significant,and a power function regression explained 54% of the variance in annual TOC fluxes. TOC fluxes were higher from upland forestthan mixed land use, and highest from the cropland-dominated watershed. The fluxes from first order watersheds were more variable with precipitation. In the spring, TOC fluxes were highest and most correlated with precipitation, compared to other seasons. Precipitation volume also explained much of thevariance in annual and spring TOC concentrations from upland forest and cropland, with concentrations three to five times higher in very wet years than in very dry years. Variation in winter and summer air temperature was correlated with TOC concentrations from forested watersheds, and linear regressionsexplained 19 to 42% of the variance in TOC. A regression modelwas used to construct graphical and tabular summaries. Particulate organic carbon and dissolved organic carbon (DOC)concentrations and the ratio of DOC to TOC were highly correlated with water discharge for a second order, mixed land use watershed, and power function regressions explained 21 to 43% of the variance. For the first order, single-land-use watersheds the ratio of DOC to TOC was also highly correlatedwith discharge.     

Temporal Trends of Trace Metals in Sediment and Invertebrates from Stormwater Management Ponds

Stormwater ponds are an increasingly common feature in urban landscapes. Because these ponds retain runoff and particulate-bound contaminants from impervious surfaces, organisms inhabiting stormwater ponds may be exposed to elevated metal levels in sediments. This study evaluated temporal changes in sediment and macroinvertebrate Cu, Pb and Zn over an eleven-year period with specific attention to land use in pond watersheds. Sediment and invertebrate metal levels were quantified using atomic absorption spectrophotometry (1993 samples) or inductively coupled plasma mass spectrometry (2003–2004 samples). Sediment trace element levels did not significantly change from 1993 to 2003-2004 with the exception of Zn in ponds receiving runoff from highways, which increased from a mean of 32 mg kg^?1 in 1993 to 344 mg kg^?1 in 2003–2004. Sediment Pb and Cu generally remained below published threshold effects concentrations (TEC) except for two instances of elevated Cu in 2003–2004. Zn remained below the TEC in 1993 but exceeded the TEC in six ponds in 2003–2004. Trace metal body burdens varied among invertebrate groups, and to a lesser extent among land uses, but in both cases this variation was a function of year. In general, trace element body burdens were more similar among invertebrate groups or land use or both during 2003–2004 when compared to levels in 1993. Our results suggest sediment and invertebrate trace metal levels are at steady state in these stormwater management ponds and that risk to organisms inhabiting these ponds does not vary as a function of pond age.     

Effect of temperature and pH on the generation of flavor volatiles in extrusion cooking of wheat flour

Extrusion temperature (120, 135, and 150 degrees C) and quantity of added sodium hydroxide (0, 3, and 6 g/kg feedstock) were used as variables to study flavor generation in extrusion cooking of wheat flour. In total, 127 volatile components were identified in the extrudates, of which 51 contained sulfur. The levels of pyrroles, thiophenes, thiophenones, thiapyrans, and thiazolines increased at higher extrusion temperatures, whereas furans and aldehydes decreased. The addition of sodium hydroxide also affected the formation of volatile compounds. However, thiophenes, thiophenones, polythiacycloalkanes, thiazoles, thiazolines, pyrroles, and some pyrazines tended to increase with the more alkaline extrusion conditions. Some compounds from lipid-Maillard interactions were identified in the extrudates. Analysis of the volatile components by gas chromatography-olfactometry showed sulfur- and nitrogen-sulfur-containing heterocycles as possible contributors to the sulfury and rubbery odors observed in extrudates produced at the higher temperature and more alkaline conditions.     

Microbial community response to nitrogen deposition in northern forest ecosystems

The productivity of temperate forests is often limited by soil N availability, suggesting that elevated atmospheric N deposition could increase ecosystem C storage. However, the magnitude of this increase is dependent on rates of soil organic matter formation as well as rates of plant production. Nonetheless, we have a limited understanding of the potential for atmospheric N deposition to alter microbial activity in soil, and hence rates of soil organic matter formation. Because high levels of inorganic N suppress lignin oxidation by white rot basidiomycetes and generally enhance cellulose hydrolysis, we hypothesized that atmospheric N deposition would alter microbial decomposition in a manner that was consistent with changes in enzyme activity and shift decomposition from fungi to less efficient bacteria. To test our idea, we experimentally manipulated atmospheric N deposition (0, 30 and 80 kg NO₃⁻-N) in three northern temperate forests (black oak/white oak (BOWO), sugar maple/red oak (SMRO), and sugar maple/basswood (SMBW)). After one year, we measured the activity of ligninolytic and cellulolytic soil enzymes, and traced the fate of lignin and cellulose breakdown products (¹³C-vanillin, catechol and cellobiose).In the BOWO ecosystem, the highest level of N deposition tended to reduce phenol oxidase activity (131±13 versus 104±5 μmol h⁻¹ g⁻¹) and peroxidase activity (210±26 versus 190±21 μmol h⁻¹ g⁻¹) and it reduced ¹³C-vanillin and ¹³C-catechol degradation and the incorporation of ¹³C into fungal phospholipids (p<0.05). Conversely, in the SMRO and SMBW ecosystems, N deposition tended to increase phenol oxidase and peroxidase activities and increased vanillin and catechol degradation and the incorporation of isotope into fungal phospholipids (p<0.05). We observed no effect of experimental N deposition on the degradation of ¹³C-cellulose, although cellulase activity showed a small and marginally significant increase (p<0.10). The ecosystem-specific response of microbial activity and soil C cycling to experimental N addition indicates that accurate prediction of soil C storage requires a better understanding of the physiological response of microbial communities to atmospheric N deposition.     

The role of alkaline materials in precipitation chemistry: A brief review of the issues

The purpose of this paper is to provide a brief overview of the relatively unexplored role of alkaline materials in precipitation chemistry. Clearly, they can play fully as important a role as acidic materials in determining pH. The first major issue concerns sources. Comparison of Ca/K and Ca/Mg ratios in precipitation and dry deposition with those in likely sources indicates that both unpaved roads and soils make important contributions. Elemental emissions fluxes have been derived from literature estimates of mass emissions fluxes and element abundances in the important sources, but are subject to large uncertainties owing to a lack of adequate data. It is quite clear, however, that conventional (smokestack) sources are minor compared to open sources such as those already identified. Another major issue concerns interactions between alkaline aerosols and water in the atmosphere. Reactions involving suspended solids that lead to removal of H-ions from solution include ion exchange and mineral weathering. A simplified model of acid buffering indicates that NH4, Ca, Mg, K, and Na buffer between 25 and 50% of the potential acids in U.S. precipitation everywhere east of the Mississippi River. The third major issue concerns wet and dry deposition fluxes of alkaline materials. Wet deposition fluxes are currently being measured adequately by a nationwide network of weekly samplers. There is no agreed-upon method for monitoring dry deposition, but available information suggests that dry deposition accounts for somewhat more than half of the Ca deposition. A list of research and data needs is also provided.     

Faunal effects on the distribution of gamma emitting radionuclides in four forested soils

Brown trouts, Salmo trutta, were exposed via aquarial water to ²⁰³Hg²⁺ or to CH₃ ⁻²⁰³Hg⁺ alone or together with one of the following S-containing substances: sodium dimethyldithiocarbamate (SMC), sodium diethyldithiocarbamate (SEC), potassium ethylxanthate (PEX), sodium isopropylxanthate (SIX), sodium diethyldithiophospbate (SEP), sodium diisopropyldithiophosphate (SIP) or sodium pyridinethione (SPyr). The distribution of the ²⁰³Hg²⁺ and the CH₃−²⁰³Hg⁺ in the fishes were then studied by whole-body autoradiography and gamma spectrometry. The results showed that the examined complexing substances can induce increased uptake of both ²⁰³Hg²⁺ and CH₃−²⁰³Hg⁺ by the fishes: for ²⁰³Hg²⁺ most of the complexing substances induced a similar increase in various tissues; for CH₃−²⁰³Hg⁺ marked variations were seen for different substances. Determinations of chloroform/water partition coefficients showed that the examined substances are able to form lipophilic complexes both with Hg²⁺ and CH₃−Hg⁺. A facilitated penetration of the lipophilic complexes over the membranes of the gills and other tissues may underly the increments of the tissue-levels of the Hg. It is possible that increased uptake of Hg²⁺ and CH₃−Hg⁺ induced by complexing substances of this type may have toxicological implications for fishes and for other aquatic organisms.