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USGS2018

Acetylenotrophy: A hidden but ubiquitous microbial metabolism?

Acetylene (IUPAC name: ethyne) is a colorless, gaseous hydrocarbon, composed of two triple bonded carbon atoms attached to hydrogens (C 2 H 2 ). When microbiologists and biogeochemists think of acetylene, they immediately think of its use as an inhibitory compound of certain microbial processes and a tracer for nitrogen fixation. However, what is less widely known is that anaerobic and aerobic microorganisms can degrade acetylene, using it as a sole carbon and energy source and providing the basis of a microbial food web. Here, we review what is known about acetylene degrading organisms and introduce the term 'acetylenotrophs' to refer to the microorganisms that carry out this metabolic pathway. In addition, we review the known environmental sources of acetylene and postulate the presence of an hidden acetylene cycle. The abundance of bacteria capable of using acetylene and other alkynes as an energy and carbon source suggests that there are energy cycles present in the environment that are driven by acetylene and alkyne production and consumption that are isolated from atmospheric exchange. Acetylenotrophs may have developed to leverage the relatively high concentrations of acetylene in the pre-Cambrian atmosphere, evolving later to survive in specialized niches where acetylene and other alkynes were produced.

FEMS Microbiology Ecology↗

USGS2015

Estuarine fish communities respond to climate variability over both river and ocean basins

Estuaries are dynamic environments at the land–sea interface that are strongly affected by interannual climate variability. Ocean–atmosphere processes propagate into estuaries from the sea, and atmospheric processes over land propagate into estuaries from watersheds. We examined the effects of these two separate climate-driven processes on pelagic and demersal fish community structure along the salinity gradient in the San Francisco Estuary, California, USA. A 33-year data set (1980–2012) on pelagic and demersal fishes spanning the freshwater to marine regions of the estuary suggested the existence of five estuarine salinity fish guilds: limnetic (salinity = 0–1), oligohaline (salinity = 1–12), mesohaline (salinity = 6–19), polyhaline (salinity = 19–28), and euhaline (salinity = 29–32). Climatic effects propagating from the adjacent Pacific Ocean, indexed by the North Pacific Gyre Oscillation (NPGO), affected demersal and pelagic fish community structure in the euhaline and polyhaline guilds. Climatic effects propagating over land, indexed as freshwater outflow from the watershed (OUT), affected demersal and pelagic fish community structure in the oligohaline, mesohaline, polyhaline, and euhaline guilds. The effects of OUT propagated further down the estuary salinity gradient than the effects of NPGO that propagated up the estuary salinity gradient, exemplifying the role of variable freshwater outflow as an important driver of biotic communities in river-dominated estuaries. These results illustrate how unique sources of climate variability interact to drive biotic communities and, therefore, that climate change is likely to be an important driver in shaping the future trajectory of biotic communities in estuaries and other transitional habitats.

California↗

USGS1981

Geology and concepts of genesis of important types of uranium deposits

Uranium ore deposits occur in nearly every major rock type in the earth’s crust, and nearly all igneous, metamorphic, and sedimentary processes are capable of concentrating or dispersing uranium. However, only three types of deposits account for more than 70 percent of known Western World Reasonably Assured Resources (WWRAR): Precambrian quartz-pebble conglomerate type, Proterozoic unconformity type, and Phanerozoic sandstone type. Igneous-related processes in plutonic, volcanic, and magmatic-hydrothermal environments, considered important 25 years ago, now account for less than 10 percent of world resources known at present. The oldest known ore deposits were formed in conglomerates by placer processes under unique anoxic conditions. For the last 2.2 b.y., since oxygenation of the atmosphere, the genesis of both high- and low-temperature deposits has been dominated by three general geochemical processes: (1) oxidation of uranium to soluble U(VI) species permitting aqueous transport, perhaps most commonly as uranyl-carbonate complexes; (2) reduction, principally by C, S −2 , or Fe +2 species, to U(IV) to allow precipitation of uraninite (pitchblende), and coffinite, although the specific reductant commonly cannot be determined because these three tend to be associated geologically; and (3) igneous and metamorphic differentiation caused by exclusion of uranium from crystal structure of most rock-forming minerals. The geochemistry of uranium ore-forming processes has changed in time because of the evolution of life forms and their impact on the earth’s oxygen and carbon budgets. This evolution is reflected in changing predominance of ore types in geologic time: (1) pre-2.8 b.y. ago—no known uranium ore deposits; (2) ca. 2.8 to 2.2 b.y. ago—the first intràcratonic basins and anoxic atmosphere permitted accumulation of placer deposits of uraninite in quartz-pebble conglomerates; these deposits contain about 19 percent of the western world’s resources; (3) ca. 2.2 to 0.4 b.y. ago—following oxygenation of the atmosphere uranium was oxidized and transported as soluble U(VI) complexes to sites of reduction, commonly in organic carbon-rich marginal marine environments. Diagenesis, metamorphism, and near-surface redox enrichment subsequently formed unconformity-type, ultrametamorphic-type, and vein-type ore deposits which together contain more than 25 percent of the western world’s resources; (4) ca. 0.4 b.y. ago to present—after development of land plants the most important ore-forming process was redox-controlled deposition from ground water in continental sediments. Sandstone-type deposits, characteristic of this stage, contain about 40 percent of the western world’s resources.

Book chapter↗

USGS2012

Mercury and halogens in coal--Their role in determining mercury emissions from coal combustion

Mercury is a toxic pollutant. In its elemental form, gaseous mercury has a long residence time in the atmosphere, up to a year, allowing it to be transported long distances from emission sources. Mercury can be emitted from natural sources such as volcanoes, or from anthropogenic sources, such as coal-fired powerplants. In addition, all sources of mercury on the Earth's surface can re-emit it from land and sea back to the atmosphere, from which it is then redeposited. Mercury in the atmosphere is present in such low concentrations that it is not considered harmful. Once mercury enters the aquatic environment, however, it can undergo a series of biochemical transformations that convert a portion of the mercury originally present to methylmercury, a highly toxic organic form of mercury that accumulates in fish and birds. Many factors contribute to creation of methylmercury in aquatic ecosystems, including mercury availability, sediment and nutrient load, bacterial influence, and chemical conditions. In the United States, consumption of fish with high levels of methylmercury is the most common pathway for human exposure to mercury, leading the U.S. Environmental Protection Agency (EPA) to issue fish consumption advisories in every State. The EPA estimates that 50 percent of the mercury entering the atmosphere in the United States is emitted from coal-burning utility powerplants. An EPA rule, known as MATS (for Mercury and Air Toxics Standards), to reduce emissions of mercury and other toxic pollutants from powerplants, was signed in December 2011. The rule, which is currently under review, specifies limits for mercury and other toxic elements, such as arsenic, chromium, and nickel. MATS also places limits on emission of harmful acid gases, such as hydrochloric acid and hydrofluoric acid. These standards are the result of a 2010 detailed nationwide program by the EPA to sample stack emissions and thousands of shipments of coal to coal-burning powerplants. The United States is the only nation to have collected such detailed information for mercury in both its coal and its utility emissions.

Fact Sheet↗

USGS2017

Abundant carbon substrates drive extremely high sulfate reduction rates and methane fluxes in Prairie Pothole Wetlands

Inland waters are increasingly recognized as critical sites of methane emissions to the atmosphere, but the biogeochemical reactions driving such fluxes are less well understood. The Prairie Pothole Region (PPR) of North America is one of the largest wetland complexes in the world, containing millions of small, shallow wetlands. The sediment pore waters of PPR wetlands contain some of the highest concentrations of dissolved organic carbon (DOC) and sulfur species ever recorded in terrestrial aquatic environments. Using a suite of geochemical and microbiological analyses, we measured the impact of sedimentary carbon and sulfur transformations in these wetlands on methane fluxes to the atmosphere. This research represents the first study of coupled geochemistry and microbiology within the PPR and demonstrates how the conversion of abundant labile DOC pools into methane results in some of the highest fluxes of this greenhouse gas to the atmosphere ever reported. Abundant DOC and sulfate additionally supported some of the highest sulfate reduction rates ever measured in terrestrial aquatic environments, which we infer to account for a large fraction of carbon mineralization in this system. Methane accumulations in zones of active sulfate reduction may be due to either the transport of free methane gas from deeper locations or the co-occurrence of methanogenesis and sulfate reduction. If both respiratory processes are concurrent, any competitive inhibition of methanogenesis by sulfate-reducing bacteria may be lessened by the presence of large labile DOC pools that yield noncompetitive substrates such as methanol. Our results reveal some of the underlying mechanisms that make PPR wetlands biogeochemical hotspots, which ultimately leads to their critical, but poorly recognized role in regional greenhouse gas emissions.

North Dakota↗

USGS2020

Development of a submerged aquatic vegetation growth model in the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST v3.4) model

The coupled biophysical interactions between submerged aquatic vegetation (SAV), hydrodynamics (currents and waves), sediment dynamics, and nutrient cycling have long been of interest in estuarine environments. Recent observational studies have addressed feedbacks between SAV meadows and their role in modifying current velocity, sedimentation, and nutrient cycling. To represent these dynamic processes in a numerical model, the presence of SAV and its effect on hydrodynamics (currents and waves) and sediment dynamics was incorporated into the open-source Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) model. In this study, we extend the COAWST modeling framework to account for dynamic changes of SAV and associated epiphyte biomass. Modeled SAV biomass is represented as a function of temperature, light, and nutrient availability. The modeled SAV community exchanges nutrients, detritus, dissolved inorganic carbon, and dissolved oxygen with the water-column biogeochemistry model. The dynamic simulation of SAV biomass allows the plants to both respond to and cause changes in the water column and sediment bed properties, hydrodynamics, and sediment transport (i.e., a two-way feedback). We demonstrate the behavior of these modeled processes through application to an idealized domain and then apply the model to a eutrophic harbor where SAV dieback is a result of anthropogenic nitrate loading and eutrophication. These cases demonstrate an advance in the deterministic modeling of coupled biophysical processes and will further our understanding of future ecosystem change.

Geoscientific Model Development↗

USGS1992

Contaminant transport in Massachusetts Bay

Construction of a new treatment plant and outfall to clean up Boston Harbor is currently one of the world's largest public works projects, costing about $4 billion. There is concern about the long-term impact of contaminants on Massachusetts Bay and adjacent Gulf of Maine because these areas are used extensively for transportation, recreation, fishing, and tourism, as well as waste disposal. Public concern also focuses on Stellwagen Bank, located on the eastern side of Massachusetts Bay, which is an important habitat for endangered whales. Contaminants reach Massachusetts Bay not only from Boston Harbor, but from other coastal communities on the Gulf of Maine, as well as from the atmosphere. Knowledge of the pathways, mechanisms, and rates at which pollutants are transported throughout these coastal environments is needed to address a wide range of management questions.

Massachusetts↗

USGS1999

Stable isotopes and mineral resource investigations in the United States

The elements oxygen, hydrogen, sulfur, and carbon are important constituents of hydrothermal ore-forming systems and the weathering processes of mineral deposits in the surficial environment. They also play key roles in volcanic activity, ecosystem dynamics, climate change, and hydrologic and atmospheric processes. Therefore, study of the stable isotopes of these elements can provide powerful insights into these processes. This is especially true for ongoing U.S. Geological Survey (USGS) projects in the Eastern United States that are concerned with the origins of base (copper, lead, and zinc) and precious (gold and silver) metal deposits in the Carolina slate belt and northern Maine and with the environmental effects of weathering of mineral deposits (fig. 1).

Information Handout↗

USGS2015

Analysis of bathymetric surveys to identify coastal vulnerabilities at Cape Canaveral, Florida

Cape Canaveral, Florida, is a prominent feature along the Southeast U.S. coastline. The region includes Merritt Island National Wildlife Refuge, Cape Canaveral Air Force Station, NASA’s Kennedy Space Center, and a large portion of Canaveral National Seashore. The actual promontory of the modern Cape falls within the jurisdictional boundaries of Cape Canaveral Air Force Station. Erosion hazards result from winter and tropical storms, changes in sand resources, sediment budgets, and sea-level rise. Previous work by the USGS has focused on the vulnerability of the dunes to storms, where updated bathymetry and topography have been used for modeling efforts. Existing research indicates that submerged shoals, ridges, and sandbars affect patterns of wave refraction and height, coastal currents, and control sediment transport. These seabed anomalies indicate the availability and movement of sand within the nearshore environment, which may be directly related to the stability of the Cape Canaveral shoreline. Understanding the complex dynamics of the offshore bathymetry and associated sediment pathways can help identify current and future erosion vulnerabilities due to short-term (for example, hurricane and other extreme storms) and long-term (for example, sea-level rise) hazards. The purpose of this work is to describe an updated bathymetric dataset collected in 2014 and compare it to previous datasets. The updated data focus on the bathymetric features and sediment transport pathways that connect the offshore regions to the shoreline and, therefore, are related to the protection of other portions of the coastal environment, such as dunes, that support infrastructure and ecosystems. Previous survey data include National Oceanic and Atmospheric Administration’s (NOAA) National Ocean Service (NOS) hydrographic survey from 1956 and a USGS survey from 2010 that is augmented with NOS surveys from 2006 and 2007. The primary result of this analysis is documentation and quantification of the nature and rates of bathymetric changes that are near (within about 2.5 km) the current Cape Canaveral shoreline and interpretation of the impact of these changes on future erosion vulnerability.

Florida↗

USGS2005

Effects of emission reductions at the Hayden powerplant on precipitation, snowpack, and surface-water chemistry in the Mount Zirkel Wilderness Area, Colorado, 1995-2003

Precipitation, snowpack, and surface-water samples collected during 1995-2003 were analyzed to evaluate the effects of emission reductions at the Hayden powerplant on water chemistry in the Mount Zirkel Wilderness Area. The Hayden powerplant, one of two large coal-fired powerplants in the Yampa Valley, was retrofitted with control systems during late 1998 and 1999 to reduce emissions of sulfur dioxide and nitrogen oxide--the primary precursors of haze and acidic precipitation. The U.S. Geological Survey, in cooperation with the Colorado Department of Public Health and Environment, evaluated three water-chemistry data sets: wet-only precipitation chemistry from the National Atmospheric Deposition Program, snowpack chemistry from the Rocky Mountain snowpack network, and surface-water chemistry from a U.S. Geological Survey long-term lakes monitoring program. Concentrations and deposition rates of selected constituents were compared for the periods before and after emission reductions at the Hayden powerplant. Data collected during 1995-98 were used to represent the pre-control period, and data collected during 2000-2003 were used to represent the post-control period. Ten stations in the National Atmospheric Deposition Program were evaluated including two that were directly downwind from the Hayden powerplant (Dry Lake and Buffalo Pass) and eight that were upwind or more distant (more than 100 kilometers) from the powerplant. Precipitation amount at all 10 precipitation stations was lower in the post-control period than the pre-control period as a result of a regional drought that persisted during the post-control period. In contrast to precipitation amount, there was no consistent pattern of change in sulfate concentrations between periods, indicating that the drought did not have a concentrating effect on sulfate or that trends in regional sulfur dioxide emissions masked its influence. Sulfate concentrations increased at three stations between periods, remained the same at three stations, and decreased at four stations. The largest change in average annual sulfate concentrations occurred at the two precipitation stations downwind from the Hayden powerplant, decreasing by 3.3 microequivalents per liter at Dry Lake and by 2.2 microequivalents per liter at Buffalo Pass. Declines in annual sulfate deposition also were greater at Dry Lake (3.4 kilograms per hectare) and Buffalo Pass (3.3 kilograms per hectare) than at the other stations, which ranged from 0.2 to 1.7 kilograms per hectare. These results indicate that emission reductions at the Hayden powerplant have been a factor in declines in atmospheric deposition of sulfate downwind from the powerplant. Nitrate, ammonium, and base-cation concentrations, in contrast to sulfate, were higher in the post-control period than the pre-control period at all 10 stations, most likely due to a concentrating effect of the drought. Twenty-two snowpack sites in the Rocky Mountain snowpack network were evaluated including 4 sites that were located directly downwind from the Hayden powerplant and 18 sites that were upwind or more distant (as much as 200 kilometers) from the powerplant. The water content of the snowpack at maximum accumulation was lower in the post-control period than the pre-control period, reflecting the regional drought. Although there were small declines in snowpack sulfate concentrations at the downwind stations between the pre- and post-control periods, the difference was not statistically significant, indicating emission reductions had a weaker effect on snowpack chemistry than precipitation chemistry. Sulfate deposition decreased at all four downwind sites in the post-control period, primarily reflecting both lower water content and concentrations in the snowpack. As observed at the precipitation stations, nitrate, ammonium, and base-cation concentrations at all 22 sites were significantly higher in the post-control period than the pre-control period, reflecting drier conditions caused by drought. The chemistry at six surface-water sites in and near the Mount Zirkel Wilderness Area and five control sites in the Flat Tops Wilderness Area was examined. No response to emission reductions was detectable in chemistry of the surface water in the Mount Zirkel Wilderness Area. Detection of a response to changes in emissions and deposition in the lake-chemistry data may have been confounded by drought conditions during the period after emission reductions occurred. The magnitude of reduced sulfate in atmospheric deposition indicates that at some time in the future, a reduction in lake sulfate attributable to Yampa Valley emission reduction should be detectable. The trend of decreasing sulfur dioxide emissions throughout western North America over the past 20 years is reflected in reduced concentrations of sulfate in lakes that were part of this study, as well as other lakes in the Rocky Mountains. However, detection of the surface-water response to changes in deposition requires a sufficiently long record to minimize effects of climate variability and to allow for lag time as sulfate moves through storage in soil, ground water, and lake reservoirs.

Colorado↗

USGS2024

Aboveground carbon stocks across a hydrological gradient: Ghost forests to non-tidal freshwater forested wetlands

Upper estuarine forested wetlands (UEFWs) play an important role in the sequestration of atmospheric carbon (C), which is facilitated by their position at the boundary of terrestrial and maritime environments but threatened by sea level rise. This study assessed the change in aboveground C stocks along the estuarine–riverine hydrogeomorphic gradient spanning salt-impacted freshwater tidal forested wetlands to freshwater forested wetlands in seasonally tidal and nontidal landscape positions. Standing stocks of C in forested wetlands were measured along two major coastal river systems, the Winyah Bay in South Carolina and the Savannah River in Georgia (USA), replicating and expanding a previous study to allow the assessment of change over time. Aboveground C stocks on these systems averaged 172.9 Mg C ha −1 , comparable to those found in UEFWs across the globe and distinct from the terrestrial forested ecosystems they are often considered to be a part of during large-scale C inventory efforts. Groundwater salinity conditions as low as 1.3 ppt were observed in conjunction with losses of aboveground C. When viewed in context alongside expected sea level rise and corresponding saltwater intrusion estimates, these data suggest a marked decrease in aboveground C stocks in forested wetlands situated in and around tidal estuaries.

Georgia, South Carolina↗

USGS2023

VogCast: A framework for modeling volcanic air pollution and its application to the 2022 eruption of Mauna Loa Volcano, Hawai'i

Volcanic activity and the associated gas emissions into the atmosphere often result in adverse air quality conditions and present a hazard to human health and the environment. Building on a decade-long effort to provide operational surface sulfur dioxide and sulfate aerosol forecasts for the State of Hawai'i, we present an air quality modeling framework called VogCast. VogCast is designed to simplify ensemble air quality prediction on a regional scale by linking together multiple state-of-the-art models of meteorology, emissions, and dispersion. The framework is open-source and introduces a new dynamic plume-rise algorithm for distributing pollutants vertically. Using radar and satellite data, we demonstrate that VogCast reasonably captured the mean injection height, the location, and the general envelope of the vog plume during Mauna Loa's 2022 eruption. The results suggest that during the 12-day eruption period model performance varied between days with trade and non-trade wind conditions. Our findings also highlight the importance of sulfur dioxide emission rate and vent parameter inputs for improving forecast accuracy. The broad goal of this work is to better our understanding of vog dispersion and improve air quality prediction for impacted communities.

Hawaii↗

USGS1994

Degradation of trifluoroacetate in oxic and anoxic sediments

THE deleterious effect of chlorofluorocarbons on stratospheric ozone has led to international cooperation to end their use. The search for acceptable alternatives has focused on hydrofluorocarbons (HFCs) or hydrochlorofluorocarbons (HCFCs) which are attractive because they have relatively short atmospheric residence times. HFCs and HCFCs are attacked by tropospheric hydroxyl radicals, leading to the formation of trifluoroacetate (TFA). Most of the atmospheric TFA is deposited at the Earth's surface, where it is thought to be highly resistant to bacterial attack. Therefore, use of HCFCs and HFCs may lead to accumulation of TFA in soils, where it could prove toxic or inhibitory to plants and soil microbial communities. Although little is known about the toxicity of TFA, monofluoroacetate, which occurs at low levels in some plants and which is susceptible to slow attack by aerobic soil microbes, is known to be acutely toxic. Here we report that TFA can be rapidly degraded microbially under anoxic and oxic conditions. These results imply that significant microbial sinks exist in nature for the elimination of TFA from the environment. We also show that oxic degradation of TFA leads to the formation of fluoroform, a potential ozone-depleting compound with a much longer atmospheric lifetime than the parent compounds.The deleterious effect of chlorofluorcarbons on stratospheric ozone has led to international cooperation to end their use. The search for acceptable alternatives has focused on hydroflnorocarbons (HFCs) or hydrochloroflnorcarbons (HCFs) which are attractive because they have relatively short atmospheric residence times. HFCs and HCFs are attacked by tropospheric hydroxyl radicals, leading to the formation of trifluoroacetate (TFA). Most of the atmospheric TFA is deposited at the Earth's surface, where it is thought to be highly resistant to bacterial attack. Therefore, use of HCFs and HCFs may lead to accummulation of TFA in soils, where it could prove toxic or inhibitory to plants and soil microbial communities. Although little is known about the toxicity of TFA, monofluoracetate, which occurs at low levels in some plants and which is susceptible to slow attack by aerobic soil microbes, is known to be acutely toxic. Here we report that TFA can be rapidly degraded microbially under anoxic and oxic conditions. These results imply that significant microbial sinks exist in nature for the elimination of TFA from the environment. We also show that oxic degradation of TFA leads to the formation of fluoroform, a potential ozone-depleting compound with a much longer atmospheric lifetime than the parent compounds.

Nature↗

USGS2007

The distribution, occurrence and environmental effect of mercury in Chinese coals

Mercury (Hg) is a toxic, persistent, and globally distributed pollutant due to its characteristic properties such as low melting and boiling points, conversion between chemical forms and participation in biological cycles. During combustion mercury in coal is almost totally emitted to the atmosphere. With a huge amount of coal consumed, coal combustion is one of the main anthropogenic sources of this element in the environment. In this study, Hg data of 1699 coal samples of China has been compiled, and the concentration, distribution, modes of occurrence, and the impact of Hg emissions on the environment are investigated. Most Chinese coals have Hg content in the range of 0.1 to 0.3??ppm, with an average of 0.19??ppm, which is slightly higher than the average Hg content of world coals and is close to that of the U.S. coals. The Hg content in coals varies in different coal basins, geological ages and coal ranks. The most likely mode of occurrences of Hg in high-sulfur and high Hg content coals is as solid solution in pyrite. But in low-sulfur coals, modes of occurrence of Hg are variable, and the organic-bound and sulfide-bound Hg may dominate. Silicate-bound Hg may be the main form in some coals because of magmatic intrusion. Mercury emissions during coal combustion have resulted in serious environmental contamination in China, particularly in the northeastern and southwestern China, where a high Hg content in the atmosphere occurs. ?? 2007 Elsevier B.V. All rights reserved.

Science of the Total Environment↗

USGS1992

Spectral ratio method for measuring emissivity

The spectral ratio method is based on the concept that although the spectral radiances are very sensitive to small changes in temperature the ratios are not. Only an approximate estimate of temperature is required thus, for example, we can determine the emissivity ratio to an accuracy of 1% with a temperature estimate that is only accurate to 12.5 K. Selecting the maximum value of the channel brightness temperatures is an unbiased estimate. Laboratory and field spectral data are easily converted into spectral ratio plots. The ratio method is limited by system signal:noise and spectral band-width. The images can appear quite noisy because ratios enhance high frequencies and may require spatial filtering. Atmospheric effects tend to rescale the ratios and require using an atmospheric model or a calibration site.

Colorado↗

USGS2011

The high life: Transport of microbes in the atmosphere

Microbes (bacteria, fungi, algae, and viruses) are the most successful types of life on Earth because of their ability to adapt to new environments, reproduce quickly, and disperse globally. Dispersal occurs through a number of vectors, such as migrating animals or the hydrological cycle, but transport by wind may be the most common way microbes spread. General awareness of airborne microbes predates the science of microbiology. People took advantage of wild airborne yeasts to cultivate lighter, more desirable bread as far back as ancient Egypt by simply leaving a mixture of grain and liquids near an open window. In 1862, Louis Pasteur's quest to disprove spontaneous generation resulted in the discovery that microbes were actually single-celled, living creatures, prevalent in the environment and easily killed with heat (pasteurization). His rudimentary experiments determined that any nutrient medium left open to the air would eventually teem with microbial life because of free-floating, colonizing cells. The same can happen in a kitchen: Opportunistic fungal and bacterial cells cause food items exposed to the air to eventually spoil.

Eos, Transactions, American Geophysical Union↗

USGS2026

Across-track tilt concept for sun glint mitigation in future Earth-observing missions

Sun glint is a major limitation for spaceborne optical remote sensing of aquatic environments, particularly in tropical and subtropical regions. By dominating the at-sensor radiance, sun glint complicates atmospheric correction and reduces the quality of aquatic reflectance products derived across Earth observation missions. This study presents a machine learning framework to quantify sun glint probability and evaluates the across-track tilt observational concept as a potential sun glint mitigation approach for satellite remote sensing missions. More than 14,000 cloud-free Landsat 8 and 9 scenes were analyzed to quantify glint occurrence as a function of sun-sensor geometry, latitude, and season. Logistic regression and machine learning models identified solar zenith angle (SZA), wind speed, and viewing zenith angle (VZA) as the primary predictors of sun glint probability, achieving >98% classification accuracy. Sun glint contamination was found to be negligible for SZA > 40° but frequent at SZA <35°, particularly in forward-scattering geometries. Introducing a 3° across-track westward tilt reduces the proportion of glint-contaminated pixels by ~21% in tropical and subtropical regions, while larger tilts of 6°, 9°, and 12° yield reductions of 43%, 59%, and 74%, respectively. These findings underscore the value of incorporating glint mitigation strategies in future Earth observing mission designs. A modest across-track tilt, combined with post-acquisition glint detection and correction, offers a practical pathway to increasing the availability of high-quality aquatic observations for monitoring inland and coastal water quality and ecosystems.

IEEE Transactions on Geoscience and Remote Sensing↗

USGS1984

Acid precipitation; an annotated bibliography

This collection of 1660 bibliographies references on the causes and environmental effects of acidic atmospheric deposition was compiled from computerized literature searches of earth-science and chemistry data bases. Categories of information are (1) atmospheric chemistry (gases and aerosols), (2) precipitation chemistry, (3) transport and deposition (wet and dry), (4) aquatic environments (biological and hydrological), (5) terrestrial environments, (6) effects on materials and structures, (7) air and precipitation monitoring and data collection, and (8) modeling studies. References date from the late 1800 's through December 1981. The bibliography includes short summaries of most documents. Omitted are unpublished manuscripts, publications in press, master 's theses and doctoral dissertations, newspaper articles, and book reviews. Coauthors and subject indexes are included. (USGS)

Circular↗