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At least 1,297 records · Page 72Linked to original sources
USGS2020

Compilation of mercury data and associated risk to human and ecosystem health, Bad River Band of Lake Superior Chippewa, Wisconsin

Mercury is an environmentally ubiquitous neurotoxin, and its methylated form presents health risks to humans and other biota, primarily through dietary intake. Because methylmercury bioaccumulates and biomagnifies in living tissue, concentrations progressively increase at higher trophic positions in ecosystem food webs. Therefore, the greatest health risks are for organisms at the highest trophic positions and for humans who consume organisms such as fish from these high trophic positions. Data on environmental mercury concentrations in various media and biota provide a basis for comparison among sites and regions and for evaluating ecosystem health risks. The U.S. Geological Survey, in cooperation with the Natural Resources Department, Bad River Band of Lake Superior Chippewa, have compiled a dataset from analyses of mercury concentrations in surface water, bed sediment, fish tissue, Rana clamitans (green frog) tissue, Haliaeetus leucocephalus (bald eagle) feathers, Lontra canadensis (North American river otter) hair, Zizania palustris (northern wild rice), and litterfall from samples collected in the Bad River watershed, Wisconsin during 2004–18. These data originated from either the Natural Resources Department or another agency based on samples collected within or near to Bad River Tribal lands before transfer to the U.S. Geological Survey for compilation and analysis at the onset of the project. This report describes the compiled mercury dataset, provides comparisons to similar measurements in the region and elsewhere, and evaluates health risks to humans and to the sampled biota. Except for litterfall, data were not collected on a consistent, regular basis over a sufficient period to evaluate temporal patterns. The reported mercury concentrations are generally similar to those reported elsewhere in the upper Great Lakes region. Reported values are consistent with atmospheric deposition as the principal source and reflect a favorable environment for mercury methylation. Fish mercury concentrations increased at higher food web positions and generally increased with length in most species measured. Sander vitreus (walleye) present the greatest risk to humans among fishes considered here because of their high trophic position and associated elevated mercury concentrations in combination with relatively high walleye consumption rates by the Native American community. Methylmercury concentrations in wild rice are generally low and likely pose little health risk. Despite reports of declining atmospheric mercury deposition across eastern North America during the past decade, a downward trend in litterfall mercury deposition was not evident in samples collected during 2012–18. Limitations in this data compilation and analysis were noted due to missing information such as collection dates and site locations for some samples. Regular monitoring of mercury in litterfall and surface waters along with periodic collection of fish would enable evaluation of temporal change in the mercury cycle that might affect future risk to humans and aquatic ecosystem inhabitants.

Wisconsin↗
USGS2026

Early Pliocene (Zanclean) sea surface temperature for PlioMIP3

Paleoclimate researchers have been comparing Pliocene environmental data to paleoclimate model results since the 1980s. The Pliocene Model Intercomparison Project (PlioMIP) began in 2008 with a focus on the Late Pliocene. Here we assess the availability and utility of sea surface temperature (SST) data for verification of Pliocene Model Intercomparison Project (PlioMIP3) Early Pliocene (Zanclean) experiments. We analyze published data in terms of quantity and spatial distribution. Only SST estimates derived using alkenone paleo thermometry are reported, and all estimates are based upon the same temperature calibration. Sea surface temperature data are selected from within three distinct time intervals: The early Zanclean 5.3 Ma – 4.2 Ma time slab, and two time slices within the early Zanclean, chosen by PlioMIP3 at 4.870 Ma and 4.474 Ma. Results show the early Zanclean time slab contains 2055 individual estimates. Approximately ∼ 80% of these estimates come from Sites 609, 642, 846, 847, 882, 907, and 1146. There are 17 sites with a total of 42 estimates within the 4.474 Ma ±10 kyr time slice, and 15 sites with a total of 47 data points within the 4.870 Ma ±10 kyr interval. The sparse spatial and temporal distribution of Zanclean data, relative to the data available for the mid Piacenzian, makes point-by-point data model comparison suspect. We suggest interpreting model output against lower resolution long term trends in proxy data, and comparison of models through temperature gradients, may be the most useful application of currently available data. Integrating Zanclean age coastal plain sequences within data model comparison schemes, for increased understanding of regional climate impacts, also holds great potential.

Global and Planetary Change↗
USGS2021

Effects of climate and irrigation on GRACE-based estimates of water storage changes in major US aquifers

Understanding climate and human impacts on water storage is critical for sustainable water-resources management. Here we assessed climate and human drivers of total water storage (TWS) variability from Gravity Recovery and Climate Experiment (GRACE) satellites compared with drought severity and irrigation water use in 14 major aquifers in the United States. Results show that long-term variability in TWS tracked by GRACE satellites is dominated by interannual variability in most of the 14 major US aquifers. Low TWS trends in the humid eastern U.S. are linked to low drought intensity. Although irrigation pumpage in the humid Mississippi Embayment aquifer exceeded that in the semi-arid California Central Valley, a surprising lack of TWS depletion in the Mississippi Embayment aquifer is attributed to extensive streamflow capture. Marked storage depletion in the semi-arid southwestern Central Valley and south-central High Plains totaled ∼90 km 3 , about three times greater than the capacity of Lake Mead, the largest U.S. reservoir. Depletion in the Central Valley was driven by long-term droughts (⩽5 yr) amplified by switching from mostly surface water to groundwater irrigation. Low or slightly rising TWS trends in the northwestern (Columbia and Snake Basins) US are attributed to dampening drought impacts by mostly surface water irrigation. GRACE satellite data highlight synergies between climate and irrigation, resulting in little impact on TWS in the humid east, amplified TWS depletion in the semi-arid southwest and southcentral US, and dampened TWS deletion in the northwest and north central US Sustainable groundwater management benefits from conjunctive use of surface water and groundwater, inefficient surface water irrigation promoting groundwater recharge, efficient groundwater irrigation minimizing depletion, and increasing managed aquifer recharge. This study has important implications for sustainable water development in many regions globally.

Environmental Research Letters↗
USGS2018

Agriculture

Agricultural production is a fundamental activity conducted on 45% of the U.S. land area, 55% of Mexico’s land area, and 7% of Canada’s land area (World Bank 2016). Because of this vast spatial extent and the strong role that land management plays in how agricultural ecosystems function, agricultural lands and activities represent a large portion of the North American carbon budget. Accordingly, improved quantification of the agricultural carbon cycle, new trends in agriculture, and added opportunities for emissions reductions provide a critical foundation for considering the relationships between agriculture and carbon cycling at local, regional, continental, and global scales. More than 145 countries have specifically included agriculture in their targets and actions for mitigating climate change (FAO 2016), and agriculture has featured particularly prominently in recent target and action commitments made by developing countries to reduce greenhouse gas (GHG) emissions (Richards et al., 2015). Conversion of vast native forest and prairie to agriculture across North America between 1860 and 1960 resulted in carbon dioxide (CO2) fluxes to the atmosphere from biota and soils that exceeded those from fossil fuel emissions over the same period (Houghton et al., 1983). Correspondingly, soil organic carbon (SOC) declined in many soils during the 50 years following conversion from native ecosystems to production agriculture (Huggins et al., 1998; Janzen et al., 1998; Slobodian et al., 2002). Crop yields and corresponding above- and belowground biomass have steadily increased since the 1930s due to genetic and management innovations, which provide more organic input from which to build SOC ( Johnson et al., 2006; Hatfield and Walthall 2015). This, coupled with improved input-use efficiencies may reduce GHG-emissions per unit yield (GHG intensity), with additional improvements possible through management optimization (Grassini and Cassman 2012; Pittelkow et al., 2015). Options include reducing tillage, integrating perennials onto the landscape, reducing or eliminating bare-fallow land (i.e., land without living plants), adding cover crops, and enrolling lands in conservation easement programs. These options, originally proposed to control erosion, have potential co-benefits in terms of increased soil health, plant productivity, and soil carbon stabilization (Lehman et al., 2015). Conversely, returning lands previously enrolled in conservation easements (e.g., the Conservation Reserve Program [CRP] and other land set-aside efforts) to row-crop production, tillage, or aggressive harvesting of crop residues all risk degrading soil quality and exacerbating SOC loss. Of note is that the net results of land use and land management practices in an agricultural setting vary according to many factors, such as crop or production system type, soil type, climate, and the collection of practices at any given site. For example, many traditional practices followed by Indigenous people on tribal lands are based on an integrated approach to natural resource management and response to environmental change that may provide agricultural options uniquely suited to varied environmental settings (see Ch. 7: Tribal Lands, p. 303). Agricultural land in the United States totaled 408.2 million hectares (ha) in 2014, of which 251 million ha were in permanent meadows and pastures, 152.2 million ha were in arable land, and 2.6 million ha were in permanent crops (FAOSTAT 2016). Compared with the distribution in 2007, these numbers reflect a 4.7 million ha decline in total agricultural lands, driven by declines in arable land and permanent crops but partially offset by a modest increase in permanent meadows and pastures. Although arable lands have been declining, the combined acreage of the four major crops (corn, wheat, soybeans, and cotton) has risen slightly, with increases in land planted in corn and soybeans and decreases in cotton and wheat (see Figure 5.1, p. 232). Despite the overall slight decline in agricultural land area, the value of U.S. agricultural production rose over the past decade as a result of increased production efficiency and higher prices (USDA 2017a; see also www.ers.usda.gov). Canada has about 65 million ha of agricultural land, of which about 46 million ha are arable, accounting for only about 7% of the country’s total land area (FAOSTAT 2017). Prominent crops on Canada’s arable lands include cereals (e.g., wheat, barley, and maize), oilseeds (e.g., canola and soybeans), and pulses (e.g., peas and lentils). Natural and seeded pastures available for grazing in Canada make up about 20 million ha (Legesse et al., 2016). Agricultural land in Mexico makes up 107 million ha, of which 23 million ha are arable land, 2.7 million ha are permanent crops, and 81 million ha are permanent meadows and pastures (FAOSTAT 2017). Mexico’s major crops are fruits, corn, grains, vegetables, and sugarcane.

Report↗
USGS2001

All equal-area map projections are created equal, but some are more equal than others

High-resolution regional and global raster databases are currently being generated for a variety of environmental and scientific modeling applications. The projection of these data from geographic coordinates to a plane coordinate system is subject to significant areal error. Sources of error include users selecting an inappropriate projection or incorrect parameters for a given projection, algorithmic errors in commercial geographic information system (GIS) software, and errors resulting from the projection of data in the raster format. To assess the latter type of errors, the accuracy of raster projection was analyzed by two methods. First, a set of 12 one-degree by one-degree quadrilaterals placed at various latitudes was projected at several raster resolutions and compared to the projection of a vector representation of the same quadrilaterals. Second, several different raster resolutions of land cover data for Asia were projected and the total areas of 21 land cover categories were tabulated and compared. While equal-area projections are designed to specifically preserve area, the comparison of the results of the one-degree by one-degree quadrilaterals with the common equal area projections (e.g., the Mollweide) indicates a considerable variance in the one-degree area after projection. Similarly, the empirical comparison of land cover areas for Asia among various projections shows that total areas of land cover vary with projection type, raster resolution, and latitude. No single projection is best for all resolutions and all latitudes. While any of the equal-area projections tested are reasonably accurate for most applications with resolutions of eight-kilometer pixels or smaller, significant variances in accuracies appear at larger pixel sizes.

Cartography and Geographic Information Science↗
USGS2023

Variability in terrestrial characteristics and erosion rates on the Alaskan Beaufort Sea coast

Arctic coastal environments are eroding and rapidly changing. A lack of pan-Arctic observations limits our ability to understand controls on coastal erosion rates across the entire Arctic region. Here, we capitalize on an abundance of geospatial and remotely sensed data, in addition to model output, from the North Slope of Alaska to identify relationships between historical erosion rates and landscape characteristics to guide future modeling and observational efforts across the Arctic. Using existing datasets from the Alaska Beaufort Sea coast and a hierarchical clustering algorithm, we developed a set of 16 coastal typologies that captures the defining characteristics of environments susceptible to coastal erosion. Relationships between landscape characteristics and historical erosion rates show that no single variable alone is a good predictor of erosion rates. Variability in erosion rate decreases with increasing coastal elevation, but erosion rate magnitudes are highest for intermediate elevations. Areas along the Alaskan Beaufort Sea coast (ABSC) protected by barrier islands showed a three times lower erosion rate on average, suggesting that barrier islands are critical to maintaining mainland shore position. Finally, typologies with the highest erosion rates are not broadly representative of the ABSC and are generally associated with low elevation, north- to northeast-facing shorelines, a peaty pebbly silty lithology, and glaciomarine deposits with high ice content. All else being equal, warmer permafrost is also associated with higher erosion rates, suggesting that warming permafrost temperatures may contribute to higher future erosion rates on permafrost coasts. The suite of typologies can be used to guide future modeling and observational efforts by quantifying the distribution of coastlines with specific landscape characteristics and erosion rates.

Alaska↗
USGS2013

Reorganization of vegetation, hydrology and soil carbon after permafrost degradation across heterogeneous boreal landscapes

The diversity of ecosystems across boreal landscapes, successional changes after disturbance and complicated permafrost histories, present enormous challenges for assessing how vegetation, water and soil carbon may respond to climate change in boreal regions. To address this complexity, we used a chronosequence approach to assess changes in vegetation composition, water storage and soil organic carbon (SOC) stocks along successional gradients within four landscapes: (1) rocky uplands on ice-poor hillside colluvium, (2) silty uplands on extremely ice-rich loess, (3) gravelly–sandy lowlands on ice-poor eolian sand and (4) peaty–silty lowlands on thick ice-rich peat deposits over reworked lowland loess. In rocky uplands, after fire permafrost thawed rapidly due to low ice contents, soils became well drained and SOC stocks decreased slightly. In silty uplands, after fire permafrost persisted, soils remained saturated and SOC decreased slightly. In gravelly–sandy lowlands where permafrost persisted in drier forest soils, loss of deeper permafrost around lakes has allowed recent widespread drainage of lakes that has exposed limnic material with high SOC to aerobic decomposition. In peaty–silty lowlands, 2–4 m of thaw settlement led to fragmented drainage patterns in isolated thermokarst bogs and flooding of soils, and surface soils accumulated new bog peat. We were not able to detect SOC changes in deeper soils, however, due to high variability. Complicated soil stratigraphy revealed that permafrost has repeatedly aggraded and degraded in all landscapes during the Holocene, although in silty uplands only the upper permafrost was affected. Overall, permafrost thaw has led to the reorganization of vegetation, water storage and flow paths, and patterns of SOC accumulation. However, changes have occurred over different timescales among landscapes: over decades in rocky uplands and gravelly–sandy lowlands in response to fire and lake drainage, over decades to centuries in peaty–silty lowlands with a legacy of complicated Holocene changes, and over centuries in silty uplands where ice-rich soil and ecological recovery protect permafrost.

Alaska↗
USGS2017

Hydrogeologic and geochemical characterization and evaluation of two arroyos for managed aquifer recharge by surface infiltration in the Pojoaque River Basin, Santa Fe County, New Mexico, 2014–15

In order to provide long-term storage of diverted surface water from the Rio Grande as part of the Aamodt water rights settlement, managed aquifer recharge by surface infiltration in Pojoaque River Basin arroyos was proposed as an option. The initial hydrogeologic and geochemical characterization of two arroyos located within the Pojoaque River Basin was performed in 2014 and 2015 in cooperation with the Bureau of Reclamation to evaluate the potential suitability of these two arroyos as sites for managed aquifer recharge through surface infiltration. The selected reaches were high-gradient (average 3.0–3.5 percent) braided channels filled with unconsolidated sand and gravel-sized deposits that were generally 30–50 feet thick. Saturation was not observed in the unconsolidated channel sands in four subsurface borings but was found at 7–60 feet below the contact between the unconsolidated channel sands and the bedrock. The poorly to well-cemented alluvial deposits that make up the bedrock underlying the unconsolidated channel material is the Tesuque Formation. The individual beds of the Tesuque Formation are reported to be highly heterogeneous and anisotropic, and the bedrock at the site was observed to have variable moisture and large changes in lithology. Surface electrical-resistivity geophysical survey methods showed a sharp contrast between the electrically resistive unconsolidated channel sands and the highly conductive bedrock; however, because of the high conductivity, the resistivity methods were not able to image the water table or preferential flow paths (if they existed) in the bedrock. Infiltration rates measured by double-ring and bulk infiltration tests on a variety of channel morphologies in the study reaches were extremely large (9.7–94.5 feet per day), indicating that the channels could potentially accommodate as much as 6.6 cubic feet per second of applied water without generating surface runoff out of the reach; however, the small volume available for storage in the unconsolidated channel sands (about 410 acre-feet in the east arroyo and about 190 acre-feet in the west arroyo) and the potential for the infiltrating water to preferentially flow over the bedrock contact and out of the reach present a challenge for storing water. Although a detailed assessment of the infiltration rate of the Tesuque Formation is beyond the scope of this investigation, one double-ring infiltrometer test was conducted on an outcrop, resulting in an estimated infiltration rate of about 4 feet per day. The shallow groundwater observed in this investigation was determined to be recharged locally on the basis of groundwater elevations and geochemical and isotopic signatures. The channel sands and shallow bedrock were observed to be weathered, indicating contact with oxic groundwater following deposition. This observation was supported by whole-rock elemental analysis and mineralogy of several core samples. The downward groundwater gradient between the shallow wells and those wells screened at greater depths suggests that the shallow groundwater is recharged by local precipitation and has the potential to migrate to the deeper aquifer units. The two age-dating tracers measured in this investigation, however, demonstrate that the shallow groundwater flow paths are very slow and that the deeper flow paths are likely part of a larger regional system. The composition of the shallow, native groundwater suggests that storing water diverted from the Rio Grande is not likely to leach constituents of concern that would cause the stored water to exceed health-based U.S. Environmental Protection Agency Maximum Contaminant Levels.

New Mexico↗
USGS2014

Carbonate margin, slope, and basin facies of the Lisburne Group (Carboniferous-Permian) in northern Alaska

The Lisburne Group (Carboniferous-Permian) consists of a carbonate platform that extends for >1000 km across northern Alaska, and diverse margin, slope, and basin facies that contain world-class deposits of Zn and Ba, notable phosphorites, and petroleum source rocks. Lithologic, paleontologic, isotopic, geochemical, and seismic data gathered from outcrop and subsurface studies during the past 20 years allow us to delineate the distribution, composition, and age of the off-platform facies, and to better understand the physical and chemical conditions under which they formed. The southern edge of the Lisburne platform changed from a gently sloping, homoclinal ramp in the east to a tectonically complex, distally steepened margin in the west that was partly bisected by the extensional Kuna Basin (~200 by 600 km). Carbonate turbidites, black mudrocks, and radiolarian chert accumulated in this basin; turbidites were generated mainly during times of eustatic rise in the late Early and middle Late Mississippian. Interbedded black mudrocks (up to 20 wt% total organic carbon), granular and nodular phosphorite (up to 37 wt% P 2 O 5 ), and fine-grained limestone rich in radiolarians and sponge spicules formed along basin margins during the middle Late Mississippian in response to a nutrient-rich, upwelling regime. Detrital zircons from a turbidite sample in the western Kuna Basin have mainly Neoproterozoic through early Paleozoic U-Pb ages (~900-400 Ma), with subordinate populations of Mesoproterozoic and late Paleoproterozoic grains. This age distribution is similar to that found in slightly older rocks along the northern and western margins of the basin. It also resembles age distributions reported from Carboniferous and older strata elsewhere in northwestern Alaska and on Wrangel Island. Geochemical and isotopic data indicate that suboxic, denitrifying conditions prevailed in the Kuna Basin and along its margins. High V/Mo, Cr/Mo, and Re/Mo ratios (all marine fractions [MF]) and low MnO contents (<0.01 wt%) characterize Lisburne black mudrocks. Low Qmf/Vmf ratios (mostly 0.8-4.0) suggest moderately to strongly denitrifying conditions in suboxic bottom waters during siliciclastic and phosphorite sedimentation. Elevated to high Mo contents (31-135 ppm) in some samples are consistent with seasonal to intermittent sulfidic conditions in bottom waters, developed mainly along the basin margin. High d 15 N values (6-120) imply that the waters supplying nutrients to primary producers in the photic zone had a history of denitrification either in the water column or in underlying sediments. Demise of the Lisburne platform was diachronous and reflects tectonic, eustatic, and environmental drivers. Southwestern, south-central, and northwestern parts of the platform drowned during the Late Mississippian, coincident with Zn and Ba metallogenesis within the Kuna Basin and phosphogenesis along basin margins. This drowning was temporary (except in the southwest) and likely due to eutrophication associated with upwelling and sea-level rise enhanced by regional extension, which allowed suboxic, denitrifying waters to form on platform margins. Final drowning in the southcentral area occurred in the Early Pennsylvanian and also may have been linked to regional extension. In the northwest, platform sedimentation persisted into the Permian; its demise there appears to have been due to increased siliciclastic input. Climatic cooling may have produced additional stress on parts of the Lisburne platform biota during Pennsylvanian and Permian times.

Alaska↗
USGS2015

Human activities cause distinct dissolved organic matter composition across freshwater ecosystems

Dissolved organic matter (DOM) composition in freshwater ecosystems is influenced by interactions between physical, chemical, and biological processes that are controlled, at one level, by watershed landscape, hydrology, and their connections. Against this environmental template, humans may strongly influence DOM composition. Yet, we lack a comprehensive understanding of DOM composition variation across freshwater ecosystems differentially affected by human activity. Using optical properties, we described DOM variation across five ecosystem groups of the Laurentian Great Lakes Region: large lakes, Kawartha Lakes, Experimental Lakes Area, urban stormwater ponds, and rivers (n = 184 sites). We determined how between ecosystem variation in DOM composition related to watershed size, land use and cover, water quality measures (conductivity, dissolved organic carbon (DOC), nutrient concentration, chlorophyll a ), and human population density. The five freshwater ecosystem groups had distinctive DOM composition from each other. These significant differences were not explained completely through differences in watershed size nor spatial autocorrelation. Instead, multivariate partial least squares regression showed that DOM composition was related to differences in human impact across freshwater ecosystems. In particular, urban/developed watersheds with higher human population densities had a unique DOM composition with a clear anthropogenic influence that was distinct from DOM composition in natural land cover and/or agricultural watersheds. This nonagricultural, human developed impact on aquatic DOM was most evident through increased levels of a microbial, humic-like parallel factor analysis component (C6). Lotic and lentic ecosystems with low human population densities had DOM compositions more typical of clear water to humic-rich freshwater ecosystems but C6 was only present at trace to background levels. Consequently, humans are strongly altering the quality of DOM in waters nearby or flowing through highly populated areas, which may alter carbon cycles in anthropogenically disturbed ecosystems at broad scales.

Global Change Biology↗
USGS2024

Prioritizing river basins for nutrient studies

Increases in fluxes of nitrogen (N) and phosphorus (P) in the environment have led to negative impacts affecting drinking water, eutrophication, harmful algal blooms, climate change, and biodiversity loss. Because of the importance, scale, and complexity of these issues, it may be useful to consider methods for prioritizing nutrient research in representative drainage basins within a regional or national context. Two systematic, quantitative approaches were developed to (1) identify basins that geospatial data suggest are most impacted by nutrients and (2) identify basins that have the most variability in factors affecting nutrient sources and transport in order to prioritize basins for studies that seek to understand the key drivers of nutrient impacts. The “impact” approach relied on geospatial variables representing surface-water and groundwater nutrient concentrations, sources of N and P, and potential impacts on receptors (i.e., ecosystems and human health). The “variability” approach relied on geospatial variables representing surface-water nutrient concentrations, factors affecting sources and transport of nutrients, model accuracy, and potential receptor impacts. One hundred and sixty-three drainage basins throughout the contiguous United States were ranked nationally and within 18 hydrologic regions. Nationally, the top-ranked basins from the impact approach were concentrated in the Midwest, while those from the variability approach were dispersed across the nation. Regionally, the top-ranked basin selected by the two approaches differed in 15 of the 18 regions, with top-ranked basins selected by the variability approach having lower minimum concentrations and larger ranges in concentrations than top-ranked basins selected by the impact approach. The highest ranked basins identified using the variability approach may have advantages for exploring how landscape factors affect surface-water quality and how surface-water quality may affect ecosystems. In contrast, the impact approach prioritized basins in terms of human development and nutrient concentrations in both surface water and groundwater, thereby targeting areas where actions to reduce nutrient concentrations could have the largest effect on improving water availability and reducing ecosystem impacts.

Environmental Monitoring and Assessment↗
USGS2013

Modeling the effects of fire severity and climate warming on active layer and soil carbon dynamics of black spruce forests across the landscape in interior Alaska

There is a substantial amount of carbon stored in the permafrost soils of boreal forest ecosystems, where it is currently protected from decomposition. The surface organic horizons insulate the deeper soil from variations in atmospheric temperature. The removal of these insulating horizons through consumption by fire increases the vulnerability of permafrost to thaw, and the carbon stored in permafrost to decomposition. In this study we ask how warming and fire regime may influence spatial and temporal changes in active layer and carbon dynamics across a boreal forest landscape in interior Alaska. To address this question, we (1) developed and tested a predictive model of the effect of fire severity on soil organic horizons that depends on landscape-level conditions and (2) used this model to evaluate the long-term consequences of warming and changes in fire regime on active layer and soil carbon dynamics of black spruce forests across interior Alaska. The predictive model of fire severity, designed from the analysis of field observations, reproduces the effect of local topography (landform category, the slope angle and aspect and flow accumulation), weather conditions (drought index, soil moisture) and fire characteristics (day of year and size of the fire) on the reduction of the organic layer caused by fire. The integration of the fire severity model into an ecosystem process-based model allowed us to document the relative importance and interactions among local topography, fire regime and climate warming on active layer and soil carbon dynamics. Lowlands were more resistant to severe fires and climate warming, showing smaller increases in active layer thickness and soil carbon loss compared to drier flat uplands and slopes. In simulations that included the effects of both warming and fire at the regional scale, fire was primarily responsible for a reduction in organic layer thickness of 0.06 m on average by 2100 that led to an increase in active layer thickness of 1.1 m on average by 2100. The combination of warming and fire led to a simulated cumulative loss of 9.6 kgC m −2 on average by 2100. Our analysis suggests that ecosystem carbon storage in boreal forests in interior Alaska is particularly vulnerable, primarily due to the combustion of organic layer thickness in fire and the related increase in active layer thickness that exposes previously protected permafrost soil carbon to decomposition.

Alaska↗
USGS2022

Simulating burn severity maps at 30 meters in two forested regions in California

Climate change is altering wildfire behavior and vegetation regimes in California’s forested ecosystems. Present day fires are seeing an increase in high burn severity area and high severity patch size. The ability to predict future burn severity patterns would support better policy and land management decisions. Here we demonstrate a methodology to first, statistically estimate individual burn severity classes at 30 meters and second, cluster and smooth high severity patches onto a landscape. Our goal here was not to exactly replicate observed burn severity maps, but rather to utilize observed maps as one realization of a random process dependent on climate, topography, fire weather, and fuels, to inform creation of additional realizations through our simulation technique. We developed two sets of empirical models with two different vegetation datasets to test if coarse vegetation could accurately model for burn severity. While visual acuity can be used to assess the performance of our simulation process, we also employ the Ripley’s K function to compare spatial point processes at different scales to test if the simulation is capturing an appropriate amount of clustering. We utilize FRAGSTATS to obtain high severity patch metrics to test the contiguity of our high severity simulation. Ripley’s K function helped identify the number of clustering iterations and FRAGSTATS showed how different focal window sizes affected our ability to cluster high severity patches. High severity patch simulations was comparable between the coarse and fine resolution vegetation datasets. Improving our ability to simulate burn severity will help advance our understanding of the potential influence of land and fuels management on ecosystem-level response variables that are important for decision-makers. Simulated burn severity maps can support managing habitat and estimating risks of habitat loss, protecting infrastructure and homes, improving future wildfire emissions projections, and better mapping and planning for fuels treatment scenarios.

California↗
USGS2015

Hydrogeologic framework, hydrology, and refined conceptual model of groundwater flow for Coastal Plain aquifers at the Standard Chlorine of Delaware, Inc. Superfund Site, New Castle County, Delaware, 2005-12

From 1966 to 2002, activities at the Standard Chlorine of Delaware chemical facility in New Castle County, Delaware resulted in the contamination of groundwater, soils, and wetland sediment. In 2005, the U.S. Geological Survey (USGS), in partnership with the U.S. Environmental Protection Agency, Region 3, and the Delaware Department of Natural Resources and Environmental Control began a multi-year investigation of the hydrogeologic framework and hydrology of the confined aquifer system. The goals of the ongoing study at the site (the Potomac Aquifer Study) are to determine the hydraulic connection between the Columbia and Potomac aquifers, determine the direction of groundwater flow in the Potomac aquifer, and identify factors affecting the fate of contaminated groundwater. This report describes progress made towards these goals based on available data collected through September 2012. The regional hydrogeologic framework indicates that the site is underlain by Coastal Plain sediments of the Columbia, Merchantville, and Potomac Formations. Two primary aquifers underlying the site, the Columbia and the upper Potomac, are separated by the Merchantville Formation confining unit. Local groundwater flow in the surficial (Columbia) aquifer is controlled by topography and generally flows northward and discharges to nearby surface water. Regional flow within the Potomac aquifer is towards the southeast, and is strongly influenced by major water withdrawals locally. Previous investigations at the site indicated that contaminants, primarily benzene and chlorinated benzene compounds, were present in the Columbia aquifer in most locations; however, there were only limited detections in the upper Potomac aquifer as of 2004. From 2005 through 2012, the USGS designed a monitoring network, assisted with exploratory drilling, collected data at monitoring wells, conducted geophysical surveys, evaluated water-level responses in wells during pumping of a production well, and evaluated major aquifer withdrawals. Data collected through these efforts were used to refine the local conceptual flow system. The refined conceptual flow system for the site includes: (a) identification of gaps in confining units in the study area, (b) identification and correlation of multiple water-bearing sand intervals within the upper Potomac Formation, (c) connections between groundwater and surface water, (d) connections between shallow and deeper groundwater, (e) new water-level (or potentiometric surface) maps and inferred flow directions, and (f) identification of major local pumping well influences. The implications of the revised conceptual flow system on the occurrence and movement of site contaminants are that the resulting detection of contaminants in the upper Potomac aquifer at specific well locations can be attributed primarily to either advective lateral transport, direct vertical contaminant transport, or a combination of vertical and lateral movement resulting from changes in water withdrawal rates over time.

Delaware↗
USGS1996

The composition of fluid inclusions in ore and gangue minerals from the Silesian-Cracow Mississippi Valley-type Zn-Pb deposits Poland: Genetic and environmental implications

The composition of fluids extracted from ore and gangue sulfide minerals that span most of the paragenesis of the Silesian-Cracow district was determined using a newly developed ion chromatographic (IC) technique. Ionic species determined were Na+, NH+4, Ca2+, Mg2+, K+, Rb+, Sr2+, Ba2+, Cl-, Br-, F-, I-, PO3-4, CO2-3, HS-, S2O2-3, SO2-4, NO-3, and acetate. Mineral samples included six from the Pomorzany mine and one from the Trzebionka mine which are hosted in the Triassic Muschelkalk Formation, and two samples of drill core from mineralized Upper Devonian strata. Nine paragenetically identifiable sulfide minerals occur throughout the Silesian-Cracow district. These include from earliest to latest: early iron sulfides, granular sphalerite, early galena, light-banded sphalerite, galena, dark-banded sphalerite, iron sulfides, late dark-banded sphalerite with late galena, and late iron sulfides. Seven of the minerals were sampled for fluid inclusion analysis in this study. Only the early iron sulfides and the last galena stage were not sampled. Although the number of analyses are limited to nine samples and two replicates and there is uncertainty about the characteristics of the fluid inclusions analyzed, the data show clear temporal trends in the composition of the fluids that deposited these minerals. Fluid inclusions in minerals deposited later in the paragenesis have significantly more K+, Br-, NH+4, and acetate but less Sr2+ than those deposited earlier in the paragenesis. The later minerals are also characterized by isotopically lighter sulfur and significantly more Tl and As in the solid minerals. The change in ore-fluid chemistry is interpreted to reflect a major change in the hydrologic regime of the district. Apparently, the migrational paths of ore fluids from the Upper Silesian basin changed during ore deposition and the fluids which deposited early minerals reacted with aquifers with very different geochemical characteristics than those that deposited late minerals. The early fluids may have reacted primarily with Devonian and Lower Carboniferous carbonate aquifers deeper in the basin, whereas the later fluids appear to have had extensive contact with organic-rich rocks, probably the shallower Middle and Upper Carboniferous flysch associated with coal measures. High concentrations of toxic Tl and As occur in the readily oxidized marcasite and pyrite minerals deposited by the later fluids. In general, the geochemistry of both the early and late fluids may be explained by an evaporite related origin or by water-rock modification of a saline basinal brine. When compared to the composition of fluid inclusions in Mississippi Valley-type (MVT) ore minerals from the Ozark region of the United States, fluid inclusions in minerals from Silesian-Cracow are fundamentally different, containing more Ca2+, Mg2+, NH+4, Br-, Sr2+ and acetate in all mineral stages with significantly more K+ in later stage minerals. The differences in ore fluid chemistry between the two regions are consistent with the lithologic differences of the respective basins thought to be the source of the mineralizing brines.

Prace - Panstwowego Instytutu Geologicznego↗
USGS1964

Water quality of the Swatara Creek Basin, PA

The Swatara Creek of the Susquehanna River Basin is the farthest downstream sub-basin that drains acid water (pH of 4.5 or less) from anthracite coal mines. The Swatara Creek drainage area includes 567 square miles of parts of Schuylkill, Berks, Lebanon, and Dauphin Counties in Pennsylvania. To learn what environmental factors and dissolved constituents in water were influencing the quality of Swatara Creek, a reconnaissance of the basin was begun during the summer of 1958. Most of the surface streams and the wells adjacent to the principal tributaries of the Creek were sampled for chemical analysis. Effluents from aquifers underlying the basin were chemically analyzed because ground water is the basic source of supply to surface streams in the Swatara Creek basin. When there is little runoff during droughts, ground water has a dominating influence on the quality of surface water. Field tests showed that all ground water in the basin was non-acidic. However, several streams were acidic. Sources of acidity in these streams were traced to the overflow of impounded water in unworked coal mines. Acidic mine effluents and washings from coal breakers were detected downstream in Swatara Creek as far as Harper Tavern, although the pH at Harper Tavern infrequently went below 6.0. Suspended-sediment sampling at this location showed the mean daily concentration ranged from 2 to 500 ppm. The concentration of suspended sediment is influenced by runoff and land use, and at Harper Tavern it consisted of natural sediments and coal wastes. The average daily suspended-sediment discharge there during the period May 8 to September 30, 1959, was 109 tons per day, and the computed annual suspended-sediment load, 450 tons per square mile. Only moderate treatment would be required to restore the quality of Swatara Creek at Harper Tavern for many uses. Above Ravine, however, the quality of the Creek is generally acidic and, therefore, of limited usefulness to public supplies, industries and recreation. In general, the quality of Swatara Creek improves after it mixes with water from the Upper Little and Lower Little Swatara Creeks, which converge with the main stream near Pine Grove. Jonestown is the first downstream location where Swatara Creek contains bicarbonate ion most of the time, and for the remaining downstream length of the stream, the concentration of bicarbonate progressively increases. Before the stream enters the Susquehanna River, chemical and diluting processes contributed by tributaries change the acidic calcium sulfate water, which characterizes the upper Swatara, to a calcium bicarbonate water. A major tributary to Swatara Creek is Quittapahilla Creek, which drains a limestone region and has alkaline characteristics. Effluents from a sewage treatment plant are discharged into this stream west of Lebanon. Adjacent to the Creek are limestone quarries and during the recovery of limestone, ground water seeps into the mining areas. This water is pumped to upper levels and flows over the land surface into Quittapahilla Creek. As compared with the 1940's, the quality of Swatara Creek is better today, and the water is suitable for more uses. In large part, this improvement is due to curtailment of anthracite coal mining and because of the controls imposed on new mines, stripping mines, and the related coal mining operations, by the Pennsylvania Sanitary Water Board. Thus, today (1962) smaller amounts of coal mine wastes are more effectively flushed and scoured away with each successive runoff during storms that affect the drainage basin. Natural processes neutralizing acid water in the stream by infiltration of alkaline ground water through springs and through the streambed are also indicated.

Pennsylvania↗
USGS2019

Modeling long-term effects of fuel treatments on fuel loads and fire regimes in the Great Basin

The principal motivation for this study is that sagebrush-steppe ecosystems are undergoing significant state changes, and land managers are challenged with optimizing their resources for both short- and long-term use. Yet, limited knowledge is available regarding how the sagebrush-steppe will respond to environmental changes related to precipitation and temperature regimes, and disturbance such as fire. Furthermore, there is a lack of understanding on how fuels reduction and other fuel management activities will impact these ecosystems over the long-term. We addressed these challenges by adapting and testing a vegetation dynamics model, the Ecosystem Demography v2.2 model (EDv2.2), for the sagebrush-steppe. Vegetation dynamics models can provide estimations of ecosystem productivity in their natural and disturbance states, and thus serve as a tool to understand and predict potential changes in various processes and properties of vegetation communities. Yet, there is no vegetation dynamics model that is well-developed for the sagebrush-steppe, and thus significant effort is needed to test EDv2.2 for its application. As part of our efforts to develop the EDv2.2 model into a useful tool for the sagebrush-steppe, we developed a sagebrush plant functional type (PFT) as part of this study, and then performed sensitivity analyses, model calibration, and finally model evaluation. Furthermore, we developed several model scenarios under natural (undisturbed) and disturbed (fire) environments. We compared our model outputs with ground-based data (field and eddy covariance) and remote sensing observations. The results of our project include a sagebrush PFT that can be used in both future EDv2.2 modeling efforts and other vegetation dynamic models. Our results from the model sensitivity analysis indicate that specific leaf area (SLA), stomatal slope (STO_S), cuticular conductance (CUT_C), and carboxylase rate constant (VM0) are sensitive parameters to vegetation productivity in the model (based on gross primary production, GPP), and future modeling efforts will benefit from both lab and field studies of these parameters and sensitivity analyses. Through calibration, we found that the EDv2.2 model estimates of GPP were modeled well at our lowest elevation field site in Reynolds Creek Experimental Watershed (RCEW), which is dominated by Wyoming big sagebrush. On the contrary, we found poorer results at higher elevation site shrub sites. These sites are characterized by either low sagebrush or mountain big sagebrush, and have more forb cover than the low elevation site. In this project we also implemented the fire model in EDv2.2 to explore how shrub and C3 grasses respond to fire by analyzing post-fire GPP. We ran both point and regional model runs with fire introduced. In most fire scenarios, fire substantially reduced shrub GPP and it took several decades for shrub GPP to return to pre-fire conditions. Grass GPP responded more quickly in post-fire conditions. While these processes are representative of what other studies have found, significant efforts to improve the fire processes in EDv2.2 are needed. For example, nuances associated with the fire subroutine in the model (running periodic fire events versus instantaneous fires and fire intensity) will need to be expanded. Another significant contribution to our knowledge gap is that additional PFTs to represent the sagebrush-steppe (e.g. annual grasses such cheatgrass) are needed for EDv2.2. Regardless, this project made significant advances in PFT development and model testing. Moreover, the EDv2.2 provides a useful framework to conceptualize vegetation dynamics, project future conditions, and consider fire as a disturbance. With additional parameterizations, PFTs, and fire routines, EDv2.2 will evolve as a tool for which to better understand future ecosystem dynamics of the sagebrush-steppe.

Idaho↗
USGS2004

Chapter 14 Rex Chert member of the Permian Phosphoria Formation: Composition, with emphasis on elements of environmental concern

We present bulk chemical and mineralogical compositions, as well as petrographic and outcrop descriptions, of rocks collected from three measured outcrop sections of the Rex Chert Member of the Phosphoria Formation in southeast Idaho. The three measured sections were chosen from 10 outcrops of Rex Chert that were described in the field. The Rex Chert overlies the Meade Peak Phosphatic Shale Member of the Phosphoria Formation, the source of phosphate ore in the region. Rex Chert removed as overburden constitutes part of the material transferred to waste-rock piles during phosphate mining. It is also used to surface roads in the mining district. It has been proposed that the chert be used to cap and isolate waste piles, thereby inhibiting the leaching of potentially toxic elements into the environment. The rock samples studied here are from individual chert beds representative of each stratigraphic section sampled. The Cherty Shale Member of the Phosphoria Formation that overlies the Rex Chert in measured section 1 and the upper Meade Peak and the transition zone to the Rex Chert in section 7 were also described and sampled. The cherts are predominantly spiculite composed of granular and mosaic quartz, and sponge spicules, with various but minor amounts of other fossils and detrital grains. The Cherty Shale Member and transition rocks between the Meade Peak and Rex Chert are siliceous siltstones and argillaceous cherts with ghosts of sponge spicules and somewhat more detrital grains than the chert. The dominant mineral is quartz. Carbonate beds are rare in each section and are composed predominantly of calcite and dolomite in addition to quartz. Feldspar, mica, clay minerals, calcite, dolomite, and carbonate fluorapatite are minor to trace minerals in the chert. The concentration of SiO 2 in the chert averages 94.6 wt.%. Organic-carbon content is generally very low, but can be as much as 1.8% in Cherty Shale Member samples and as much as 3.3% in samples from the transition between the Meade Peak and Rex Chert. Likewise, phosphate (P 2 O 5 ) is generally low in the chert, but can be as much as 3.1% in individual chert beds. Selenium concentrations in Rex Chert and Cherty Shale Member samples vary from <0.2 to 138 ppm, with a mean concentration of 7.0 ppm. This mean Se content is heavily dependent on two values of 101 and 138 ppm for siliceous siltstone from the lower part of the Rex Chert, which contains rocks that are transitional in character between the Meade Peak and Rex Chert Members. Without those two samples, the mean Se concentration is < 1.0 ppm. Other elements of environmental interest, As, Cr, V, Zn, Hg, and Cd, generally occur in concentrations near or below that in average continental shale. Stratigraphic changes, equivalent to temporal changes in the depositional basin, in chemical composition of rocks are notable either as uniform changes through the sections or as distinct differences in the mean composition of rocks that comprise the upper and lower halves of the sections. Q-mode factors are interpreted to represent the following rock and mineral components: chert-silica component consisting of Si (±Ba); phosphorite-carbonate fluorapatite component composed of P, Ca, As, Y, V, Cr, Sr, and La (± Fe, Zn, Cu, Ni, Li, Se, Nd, Hg); shale component composed of Al, Na, Zr, K, Ba, Li, and organic C (± Ti, Mg, Se, Ni, Fe, Sr, V, Mn, Zn); carbonate component (dolomite, calcite, silicified carbonates) composed of carbonate C, Mg, Ca, and Si (±Mn); and, tentatively, organic matter-hosted elements (and/or sulfide-sulfate phases) composed of Cu (± organic C, Zn, Mn, Si, Ni, Hg, Li). Selenium shows a dominant association with organic matter and to lesser degrees associations with other shale components and carbonate fluorapatite. Consideration of larger numbers of factors in Q-mode analysis indicates that native Se (a factor containing Se (± Ba)) may also comprise a minor component of the Se complement. Comparison of our data with those from newly exposed outcrops in active phosphate mines indicates that weathering of typical Rex Chert outcrops likely plays an important role in removing environmentally sensitive elements.

Idaho↗