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Results for “Environmental Chemistry Letters”

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10 recordsLinked to original sources
USGS2010

The role of sample preparation in interpretation of trace element concentration variability in moss bioindication studies

Trace element concentrations in plant bioindicators are often determined to assess the quality of the environment. Instrumental methods used for trace element determination require digestion of samples. There are different methods of sample preparation for trace element analysis, and the selection of the best method should be fitted for the purpose of a study. Our hypothesis is that the method of sample preparation is important for interpretation of the results. Here we compare the results of 36 element determinations performed by ICP-MS on ashed and on acid-digested (HNO 3 , H 2 O 2 ) samples of two moss species ( Hylocomium splendens and Pleurozium schreberi ) collected in Alaska and in south-central Poland. We found that dry ashing of the moss samples prior to analysis resulted in considerably lower detection limits of all the elements examined. We also show that this sample preparation technique facilitated the determination of interregional and interspecies differences in the chemistry of trace elements. Compared to the Polish mosses, the Alaskan mosses displayed more positive correlations of the major rock-forming elements with ash content, reflecting those elements’ geogenic origin. Of the two moss species, P. schreberi from both Alaska and Poland was also highlighted by a larger number of positive element pair correlations. The cluster analysis suggests that the more uniform element distribution pattern of the Polish mosses primarily reflects regional air pollution sources. Our study has shown that the method of sample preparation is an important factor in statistical interpretation of the results of trace element determinations.

Environmental Chemistry Letters↗
USGS2003

Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada

Northern Nevada is one of the world's foremost regions of gold production. The Humboldt River Basin (HRB) covers 43,500 km2 in northern Nevada (Crompton, 1995), and it is home to approximately 18 active gold and silver mines (Driesner and Coyner, 2001) among at least 55 significant metallic mineral deposits (Long and others, 1998). Many of the gold mines are along the Carlin trend in the east-central portion of the HRB, and together they have produced 50 million ounces of gold from 1962 (when the Carlin mine first opened) through April 2002 (Nevada Mining Association, 2002). Mining is not new to the region, however. Beginning in 1849, mining has taken place in numerous districts that cover 39 percent of the land area in the HRB (Tingley, 1998). In addition to gold and silver, As, Ba, Cu, Fe, Hg, Li, Mn, Mo, Pb, S, Sb, V, W, Zn, and industrial commodities such as barite, limestone, fluorite, sand and gravel, gypsum, gemstones, pumice, zeolites, and building stone, have been extracted from the HRB (McFaul and others, 2000). All papers within this series of investigations can be found as lettered chapters of USGS Bulletin 2210, Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada. Each chapter is available separately online. The data and software utilized in this product (Chapter F) permit the user to view and analyze the geographic relationships among chemistry of stream sediments and surface waters, geology, and various cartographic base information such as but not limited to cities, county boundaries, and land ownership. Data for this product were compiled and or produced as part of a mineral and environmental assessment of the Humboldt River basin conducted by the U.S. Geological Survey between 1995 - 2000.

Bulletin↗
USGS2023

Where the past meets the present: Connecting nitrogen from watersheds to streams through groundwater flowpaths

Groundwater discharge to streams is a nonpoint source of nitrogen (N) that confounds N mitigation efforts and represents a significant portion of the annual N loading to watersheds. However, we lack an understanding of where and how much groundwater N enters streams and watersheds. Nitrogen concentrations at the end of groundwater flowpaths are the culmination of biogeochemical and physical processes from the contributing land area where groundwater recharges, within the aquifer system, and in the near-stream riparian area where groundwater discharges to streams. Our research objectives were to quantify the spatial distribution of N concentrations at groundwater discharges throughout a mixed land-use watershed and to evaluate how relationships among contributing and riparian land cover, modeled aquifer characteristics, and groundwater discharge biogeochemistry explain the spatial variation in groundwater discharge N concentrations. We accomplished this by integrating high-resolution thermal infrared surveys to locate groundwater discharge, biogeochemical sampling of groundwater, and a particle tracking model that links groundwater discharge locations to their contributing area land cover. Groundwater N loading from groundwater discharges within the watershed varied substantially between and within streambank groundwater discharge features. Groundwater nitrate concentrations were spatially heterogeneous ranging from below 0.03–11.45 mg-N/L, varying up to 20-fold within meters. When combined with the particle tracking model results and land cover metrics, we found that groundwater discharge nitrate concentrations were best predicted by a linear mixed-effect model that explained over 60% of the variation in nitrate concentrations, including aquifer chemistry (dissolved oxygen, Cl − , SO 4 2− ), riparian area forested land cover, and modeled physical aquifer characteristics (discharge, Euclidean distance). Our work highlights the significant spatial variability in groundwater discharge nitrate concentrations within mixed land-use watersheds and the need to understand groundwater N processing across the many spatiotemporal scales within groundwater cycling.

Connecticut↗
USGS2022

Sensitivity of headwater streamflow to thawing permafrost and vegetation change in a warming Arctic

Climate change has the potential to impact headwater streams in the Arctic by thawing permafrost and subsequently altering hydrologic regimes and vegetation distribution, physiognomy and productivity. Permafrost thaw and increased subsurface flow have been inferred from the chemistry of large rivers, but there is limited empirical evidence of the impacts to headwater streams. Here we demonstrate how changing vegetation cover and soil thaw may alter headwater catchment hydrology using water budgets, stream discharge trends, and chemistry across a gradient of ground temperature in northwestern Alaska. Colder, tundra-dominated catchments shed precipitation through stream discharge, whereas in warmer catchments with greater forest extent, evapotranspiration and infiltration are substantial fluxes. Forest soils thaw earlier, remain thawed longer, and display seasonal water content declines, consistent with greater evapotranspiration and infiltration. Streambed infiltration and water chemistry indicate that even minor warming can lead to increased infiltration and subsurface flow. Additional warming, permafrost loss, and vegetation shifts in the Arctic will deliver water back to the atmosphere and to subsurface aquifers in many regions, with the potential to substantially reduce discharge in headwater streams, if not compensated by increasing precipitation. Decreasing discharge in headwater streamflow will have important implications for aquatic and riparian ecosystems.

Alaska↗
USGS1996

Environmental magnetic implications of greigite (Fe3S4) formation in a 3 m.y. lake sediment record from Butte Valley, northern California Andrew

Authigenic greigite (Fe 3 S 4 ) has been identified in several horizons of lake beds in a 102-m core from Butte Valley, northern California, using mineral magnetic methods and x-ray diffraction analysis. The presence of greigite has several implications for the paleoenvironmental record from Butte Valley. First, its occurrence in 2.5–3.0 Ma strata confirms that greigite can persist in the geological record for long periods of time. Second, the detrital mineral magnetic record may be partially obscured by the presence of authigenic greigite and care must be taken in interpreting magnetic variations in the greigite-bearing zones as paleoclimate proxies. Third, differences in the timing of remanence acquisition for authigenic and detrital phases may compromise studies of high-frequency geomagnetic field variations. Fourth, greigite may also be significant as a paleoenvironmental indicator of lake and sediment chemistry. The magnetic detection of greigite may therefore provide important information about paleolimnological conditions.

Geophysical Research Letters↗
USGS2019

A multidisciplinary framework to derive global river reach classifications at high spatial resolution

Projected climate and environmental change are expected to increase the pressure on global freshwater resources. To prepare for and cope with the related risks, stakeholders need to devise plans for sustainable management of river systems, which in turn requires the identification of management-appropriate operational units, such as groups of rivers that share similar environmental and biological characteristics. Ideally, these units are of a manageable size, and are biotically or abiotically distinguishable across a variety of river types. Here, we aim to address this need by presenting a new global river classification framework (GloRiC) to establish a common vocabulary and standardized approach to the development of globally comprehensive and integrated river classifications that can be tailored to different goals and requirements. We define the GloRiC conceptual framework based on five categories of variables: (1) hydrology; (2) physiography and climate; (3) fluvial geomorphology; (4) water chemistry; and (5) aquatic biology. We then apply the framework using hydro-environmental attributes provided by a seamless high-resolution river reach database to create initial instances of three sub-classifications (hydrologic, physio-climatic, and geomorphic) which we ultimately combine into 127 river reach types at the global scale. These supervised classifications utilize a mix of statistical analyses and expert interpretation to identify the classifier variables, the number of classes, and their thresholds. In addition, we also present an unsupervised, multivariable k-means statistical clustering of all river reaches into 30 groups. These first-of-their-kind global river reach classifications at high spatial resolution provide baseline information for a total of 35.9 million kilometers of rivers that have been assessed in this study, and are expected to be particularly useful in remote or data-poor river basins. The GloRiC framework and associated data are primarily designed for broad and rapid applicability in assessments that require stratified analyses of river ecosystem conditions at global and regional scales; smaller-scale applications could follow the same conceptual framework yet use more detailed data sources.

Environmental Research Letters↗
USGS2018

Limited nitrate retention capacity in the Upper Mississippi River

The Mississippi River and other large rivers have the potential to regulate nitrogen export from terrestrial landscapes, and thus mitigate eutrophication in downstream aquatic ecosystems. In large rivers, human-constructed impoundments and connected backwaters may facilitate nitrogen removal; however, the capacity of these features is poorly quantified and incompletely incorporated into model frameworks. Using a high-resolution and spatially intensive sampling technique, we assessed the contribution of individual navigation pools, as well as impounded open waters and backwater wetlands within them, to overall nitrate retention by mapping the entire length (1370 km) of the Upper Mississippi River (UMR) main channel. Based on this single spatial survey of water chemistry, the river appeared to act primarily as a passive nitrate transporter, retaining only 12.5% of the incoming load, most of which occurred in the upper 150 km of the river, which includes the largest and only naturally impounded reach of the river. Although reservoirs typically are nitrogen sinks, our data indicate that UMR dams do not impede river flows to the extent necessary to promote substantial changes in water residence times and subsequent nitrogen removal. Backwaters routinely had lower nitrate concentrations than the main channel, but their limited hydrologic connectivity to the through-flowing river channel constrained their influence on downstream export. As a whole, the UMR did not remove a substantial proportion of its nitrate load despite optimal N removal conditions, numerous impoundments, and the presence of extensive backwater habitats. These results suggest that efforts to reduce delivery of nitrogen to the Gulf of Mexico should emphasize mitigation strategies that target upland nutrient sources rather than relying on removal within the Mississippi River.

Upper Mississippi River↗
USGS2026

Opportunities and challenges for incorporating lithium-ion batteries into geophysical power systems

Batteries play a critical role at seismic and other geophysical stations in ensuring that the equipment receives uninterrupted power to make continuous observations of the Earth. Often sited in remote environments under a wide range of environmental conditions, these stations have almost ubiquitously used conventional lead‐acid batteries. However, recent advances in rechargeable lithium‐ion battery technology have led to the development of lithium‐iron phosphate (LFP) batteries that can replace lead‐acid batteries in energy storage systems. In the past three years, LFP battery production has grown over an order of magnitude, reducing their cost and increasing their availability. In this article, we examine the benefits and challenges associated with incorporating several types of LFP batteries into the power systems of geophysical stations. We review how fundamental differences in battery chemistry enable LFP batteries to weigh less than half of comparable lead‐acid batteries and may have longer service lives but have the added complexity of being managed by an integrated battery monitoring system (BMS) microcontroller. Through a controlled heat chamber experiment, we demonstrate that LFP batteries can be ideally suited for use in high‐temperature environments by offering longer service lives than lead‐acid batteries. However, for safety reasons, the BMS prevents most LFP batteries from being charged at temperatures <0°C, which complicates their use in colder regions and can lead to equipment damage if the charging system is not appropriately designed for this battery type. Finally, we address some of the unique challenges associated with adopting lithium batteries, including unexpected substantial (≤14 W) power consumption from the BMS, safety concerns, and shipping restrictions. It is our goal to help inform station operators and geophysicists about potential benefits and issues that can arise from using LFP batteries at seismic and geophysical stations in a range of environments.

Seismological Research Letters↗
USGS2016

Multi-decadal increases in dissolved organic carbon and alkalinity flux from the Mackenzie drainage basin to the Arctic Ocean

Riverine exports of organic and inorganic carbon (OC, IC) to oceans are intricately linked to processes occurring on land. Across high latitudes, thawing permafrost, alteration of hydrologic flow paths, and changes in vegetation may all affect this flux, with subsequent implications for regional and global carbon (C) budgets. Using a unique, multi-decadal dataset of continuous discharge coupled with water chemistry measurements for the Mackenzie River, we show major increases in dissolved OC (DOC) and IC (as alkalinity) fluxes since the early 1970s, for a watershed that covers 1.8 M km 2 of northwestern Canada, and provides substantial inputs of freshwater and biogeochemical constituents to the Arctic Ocean. Over a 39-year period of record, DOC flux at the Mackenzie mouth increased by 39.3% (44.5 ± 22.6 Gmol), while alkalinity flux increased by 12.5% (61.5 ± 60.1 Gmol). Isotopic analyses and substantial increases in sulfate flux indicate that increases in alkalinity are driven by accelerating sulfide oxidation, a process that liberates IC from rock and soils in the absence of CO 2 consumption. Seasonal and sub-catchment trends suggest that permafrost thaw plays an important role in the observed increases in DOC and alkalinity: sub-catchment increases for all constituents are confined to northern, permafrost-affected regions, while observed increases in autumn to winter are consistent with documented landscape-scale changes that have resulted from changing thaw dynamics. This increase in DOC and sulfide-derived alkalinity represents a substantial intensification of land-to-ocean C mobilization, at a level that is significant within the regional C budget. The change we observe, for example, is similar to current and projected future rates of CO 2 consumption by weathering in the Mackenzie basin.

Environmental Research Letters↗
USGS2018

Carboniferous climate teleconnections archived in coupled bioapatite δ18OPO4 and 87Sr/86Sr records from the epicontinental Donets Basin, Ukraine

Reconstructions of paleo-seawater chemistry are largely inferred from biogenic records of epicontinental seas. Recent studies provide considerable evidence for large-scale spatial and temporal variability in the environmental dynamics of these semi-restricted seas that leads to the decoupling of epicontinental isotopic records from those of the open ocean. We present conodont apatite δ 18 O PO4 and 87 Sr/ 86 Sr records spanning 24 Myr of the late Mississippian through Pennsylvanian derived from the U–Pb calibrated cyclothemic succession of the Donets Basin, eastern Ukraine. On a 2 to 6 Myr-scale, systematic fluctuations in bioapatite δ 18 O PO4 and 87 Sr/ 86 Sr broadly follow major shifts in the Donets onlap–offlap history and inferred regional climate, but are distinct from contemporaneous more open-water δ 18 O PO4 and global seawater Sr isotope trends. A −1 to −6‰ offset in Donets δ 18 O PO4 values from those of more open-water conodonts and greater temporal variability in δ 18 O PO4 and 87 Sr/ 86 Sr records are interpreted to primarily record climatically driven changes in local environmental processes in the Donets sea. Systematic isotopic shifts associated with Myr-scale sea-level fluctuations, however, indicate an extrabasinal driver. We propose a mechanistic link to glacioeustasy through a teleconnection between high-latitude ice changes and atmospheric p CO 2 and regional monsoonal circulation in the Donets region. Inferred large-magnitude changes in Donets seawater salinity and temperature, not archived in the more open-water or global contemporaneous records, indicate a modification of the global climate signal in the epicontinental sea through amplification or dampening of the climate signal by local and regional environmental processes. This finding of global climate change filtered through local processes has implications for the use of conodont δ 18 O PO4 and 87 Sr/ 86 Sr values as proxies of paleo-seawater composition, mean temperature, and glacioeustasy.

Donets Basin↗