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USGS1988

Methane hydrate - A major reservoir of carbon in the shallow geosphere?

Methane hydrates are solids composed of rigid cages of water molecules that enclose methane. Sediment containing methane hydrates is found within specific pressure-temperature conditions that occur in regions of permafrost and beneath the sea in outer continental margins. Because methane hydrates are globally widespread and concentrate methane within the gas-hydrate structure, the potential amount of methane present in the shallow geosphere at subsurface depths of < ???2000 m is very large. However, estimates of the amount are speculative and range over about three orders of magnitude, from 2 ?? 103 to 4 ?? 106 Gt (gigatons = 1015 g) of carbon, depending on the assumptions made. The estimate I favor is ??? 1 ?? 104 Gt of carbon. The estimated amount of organic carbon in the methane-hydrate reservoir greatly exceeds that in many other reservoirs of the global carbon cycle - for example, the atmosphere (3.6 Gt); terrestrial biota (830 Gt); terrestrial soil, detritus and peat (1960 Gt); marine biota (3 Gt); and marine dissolved materials (980 Gt). In fact, the amount of carbon may exceed that in all fossil fuel deposits (5 ?? 103 Gt). Because methane hydrates contain so much methane and occur in the shallow geosphere, they are of interest as a potential resource of natural gas and as a possible source of atmospheric methane released by global warming. As a potential resource, methane hydrates pose both engineering and production problems. As a contributor to a changing global climate, destabilized methane hydrates, particularly those in shallow, nearshore regions of the Arctic Ocean, may have some effect, but this effect will probably be minimal, at least during the next 100 years. ?? 1988.

Chemical Geology↗

USGS1979

Effects of oil transferred from incubating gulls to their eggs

No. 2 fuel oil, or water, was applied to the breast feathers of incubating laughing gulls trapped at their nest site on an island colony in Texas. Gulls were released after treatment and allowed to incubate their eggs for 5 days. Oil was transferred from the feathers of incubating adults to their eggs and resulted in 41% embryo mortality compared with 2% in controls.

Texas↗

USGS1978

Embryotoxic effects of crude oil in mallard ducks and chicks

Recent studies in this laboratory have revealed that surface applications of microliter amounts of some crude and fuel oils that coat less than 10% of the egg surface reduce hatching considerably in different avian species. Applications of paraffin compounds that coat equal areas of the egg surface do not reduce hatching suggesting that toxicity is due to causes other than asphyxia. In the present study, 1–10 μl of South Louisiana crude oil, an API reference oil, were applied to the surface of fertile mallard ( Anas platyrhynchos ) and chicken ( Gallus gallus ) eggs. Early embryolethality was greater in mallard embryos than in chick embryos, but later embryolethality that coincided with the time of rapid outgrowth of the chorioallantoic membrane was more prevalent in chick embryos. The overall incidence of embryolethality was similar in both species. Retardation of growth as reflected by embryonic body weight, crown-rump length, beak length, and general appearance was more pronounced in chick than mallard embryos. Teratogenic defects were more frequent in chick embryos, and incomplete or abnormal ossification of the skull was the most common. External application of equivalent amounts of a mixture of paraffin compounds present in crude oil had virtually no embryotoxic effects in either species, suggesting that other components including aromatic hydrocarbons and organometallics may cause the embryotoxicity.

Toxicology and Applied Pharmacology↗

USGS1984

Feasibility of saltwater gradient ponds as a heat supply for hatchery rearing water

Salt gradient solar collector ponds are economically feasible as a source of heat energy for hatchery rearing water. A pond 3 m deep and covering an area of 5000 m 2 will supply approximately 2800 GJ of energy over a three-month period — enough for a one-year smolt program in an Atlantic salmon hatchery. The cost to construct such a pond is approximately $173,000, or the equivalent of seven years' fuel bills using conventional heating equipment. Although the technology is new and not entirely understood, existing ponds have proven to be relatively problem free and require only minimum maintenance.

Aquacultural Engineering↗

USGS1984

Stereochemical studies of acyclic isoprenoids—XII. Lipids of methanogenic bacteria and possible contributions to sediments

Abundant volatile lipids of Methanobacterium thermoautotrophicum and Methanosarcina barkeri include isoprenoid hydrocarbons (≤ C 30 ), and C 15 , C 20 and C 25 isoprenoid alcohols. M. barkeri contains 2,6,10,15,19-pentamethyleicosane, whose relative stereochemistry is the same as found in marine sediments, indicating that it is a marker of methanogenic activity. The C 20 , C 30 and C 25 alkenes in M. thermoautotrophicum also have a preferred sterochemistry; the latter have the 2,6,10,14,18-pentamethyleicosanyl skeleton, suggesting that the alkane in marine sediments may derive from methanogens. The stereochemistry of squalane in a marine sediment is also compatible with an origin in methanogens; in contrast, the stereochemistry of pristane in M. thermoautotrophicum indicates a fossil fuel contaminant origin, suggesting that this and certain other alkanes reported in archaebacteria might also be of contaminant origin. There is, therefore, little evidence at present that the pristane in immature marine sediments originates in methanogens. The C 15 and C 20 saturated alcohols in M. thermoautotrophicum have mainly the all-R configuration. If this is generally true for methanogens, the C 20 alcohol in the Messel shale may originate mainly from methanogens, whereas that in the Green River shale may originate mainly from photosynthetic organisms.

Organic Geochemistry↗

USGS1996

Organic geochemistry applied to environmental assessments of Prince William Sound, Alaska, after the Exxon Valdez oil spill—a review

Organic geochemistry played a major role in the environmental assessments conducted following the Exxon Valdez oil spill, which occurred on March 24, 1989, and released about 258,000 bbls (41 million liters) of Alaska North Slope crude oil into Prince William Sound. Geochemical analyses of more than 15,000 sediment, tar, and biological samples and about 5000 water samples provide the largest database yet collected on oil-spill chemistry, and we review the results here. The marine environment of the Sound has a complex background of petrogenic, pyrogenic, and biogenic hydrocarbons from natural and anthropogenic sources. Geochemical evaluation of the fate and effects of the spilled oil required that this oil and its residues be distinguished from the background. A variety of molecular and isotopic techniques were employed to identify various hydrocarbon sources and to distinguish quantitatively among mixed sources in the samples. Although the specific criteria used to distinguish multiple sources in the region affected by the Exxon Valdez spill are not necessarily applicable to all spill situations, the principles that governed their selection are. Distributions of polycyclic aromatic hydrocarbons (PAH) and dibenzothiophenes distinguish Exxon Valdez oil and its weathered residues from background hydrocarbons in benthic sediments. Ratios of C 2 -dibenzothiophene C 2 -phenanthrene "> C 2 -dibenzothiopheneC 2 -phenanthrene and C 3 -dibenzothiophene C 3 -phenanthrene "> C 3 -dibenzothiopheneC 3 -phenanthrene were particularly useful. Carbon isotopes and terpane distributions distinguished Exxon Valdez residues found on shorelines from tars from other sources. Diesel and diesel soot were identified by the absence of alkylated chrysenes and a narrow distribution of n -alkanes, whereas pyrogenic products were distinguished by the dominance of 4- to 6-ring PAH over 2- to 3-ring PAH and by the dominance of non-alkylated over alkylated homologues of each PAH series. The presence of 18α(H)-oleanane in benthic sediments, coupled with its absence in Exxon Valdez oil and its residues, confirm another petrogenic source. Results of geochemical studies suggest that the petrogenic component in the background of benthic sediments is derived from oil seeps in the eastern Gulf of Alaska. In 1990 and 1991, Exxon Valdez residues, generally forming a small increment to the pre-spill background, were found to be only sporadically distributed in some shallow, near shore sediments adjacent to shorelines that had been heavily oiled in 1989. In 1994, occurrences of Exxon Valdez tars on shoreline surfaces were rare, although residues could be found buried in shoreline sediments at some isolated locations along the spill path where they were protected from wave action. Spilled oil residues collected 16 months after the spill were degraded, on average, by nearly 50%. Shoreline residues from sources other than the spill were also identified and are widespread throughout the Sound. These residues include (1) geochemically distinct tars and oils imported from California oil fields to Alaska for fuel and construction purposes prior to the discovery of the Cook Inlet and North Slope oil fields, (2) diesel and diesel soot, and (3) more highly refined products. Of the more than 2700 chemical analyses of biological samples of higher life forms (fish, birds, and mammals) about 150 (6%) indicate recognizable residues of Exxon Valdez oil, which were identified by their distribution of polycyclic aromatic hydrocarbons (PAH). Most of these samples (138) were collected in 1989 and most were associated with external surfaces or the gastrointestinal tract. Rarely do internal tissues or fluids contain recognizable fingerprints of spilled oil. This observation includes samples from marine mammals that were visibly oiled externally. Other hydrocarbon sources, including diesel and a non-petroleum artifact that occurs when concentrations of individual PAH are at or near their method detection limit, are also identified in biological samples.

Alaska↗

USGS1990

The geology of selected peat-forming environments in temperate and tropical latitudes

We studied peat in several geologic and climatic settings: (1) a glaciated terrain in cold-temperate Maine and Minnesota, U.S.A.; (2) an island in a temperate maritime climate in the Atlantic Ocean off the coast of Maine, U.S.A., where sea level is rising rapidly and changing the environment of peat accumulation; (3) swamps along the warm-temperate U.S. Atlantic and Gulf Coastal Plains, where sea level has changed often, thus creating sites for accumulation; and (4) in a tropical climate along the coast of Sarawak, Malaysia, and the delta of the Batang Hari River, Sumatra, Indonesia (Figs. 1 and 2). With the exception of the deposits on the Atlantic and Gulf Coastal Plains, most of the deposits described are domed bogs in which peat accumulation continued above the surface of the surrounding soil. The bogs of the U.S. Atlantic and Gulf Coastal Plains have almost level surfaces. All domed bogs are not entirely ombrotrophic (watered only from precipitation); multidomed bogs that rise from irregular or hilly surfaces may be crossed by streams that supply water to the bogs. The geologic processes or organic sedimentation, namely terrestrialization and paludification, are similar in all peat deposits considered here. Differences in geomorphology affecting the quantity and that quality of peat that has ash contents of less than 25%, which are desirable for commercial purposes, depend chiefly on: (1) high humidity, which is favorable to luxuriant growth of peat-forming vegetation; (2) a depositional setting that permits extensive accumulation relatively free from inorganic contamination from sea water and streams and from dust and volcanic ash; and (3) a stable regional water table that controls the rate of decomposition under aerobic conditions and protects the deposit against the ravages of fire. Differences in peat textures are due to the type of vegetation and to the degree of decomposition. The rate of decomposition is largely the result of the amount of oxidation and aerobic microbial activity. Stratigraphic distribution of various textures and amounts of inorganic components within a peat deposit is largely determined by the vertical positions occupied by peat-forming environments, such as pond, marsh, swamp and heath where vegetation accumulated, and the depth to zones of unoxygenated water. Peat also differs in the rate of accumulation. On the basis of carbon-14 dating, an estimated 8 m of peat in the tropical Batang Hari River deposit in Sumatra has been accumulating at the rate of about 1.5 m/1,000 yr, whereas peat in the cold-temperate deposit in Maine has been accumulating at the rate of 0.66 m/1,000 yr. Accumulation rates in domed deposits such as these are affected not only by factors controlling volume of biomass and aerobic decay but also by stream erosion and fires that remove peat. Such disconformities (see Fig. 2) within the deposit may be recognized by sudden vertical changes in degree of decomposition and/or the presence of charcoal. The trace-element content of peat deposits is affected by the environments of their settings. Samples of peat that have an ash content of less than 25% dry weight and that are from small, almost level swamp deposits along the Atlantic Coastal Plain of North Carolina were compared with similar samples from small domed bogs in Maine, a glaciated area. Samples from Nort Carolina, which are from deposits in thick fluvial and nearshore marine sediments far from the bedrock source, are generally higher in Ti, Cr and Pb. The Maine samples from deposits in glacial drift close to the bedrock source contain more Zn, Mn, P, Ca, Na and Fe. The kind and amount of trace elements within the deposits appear to relate largely to depositional setting, to kinds of bedrock source, and to the modes of transportation from source to peat swamp. Trace-element concentrations in the extensive Sumatra peat deposit, which represents a potentially commercial coal bed, are similar to those found in Appalachian coals except for As and Au, which are higher in the former. This similarity most likely implies that geochemical controls on mineral matter controlled the concentrations in both. Most peat deposits found in the world today are not precursors of economic coal beds because they are too local in extent, lack beds of commercial-quality peat greater than 6 m thick, and/or are too far from sea level to be rapidly by marine or marginal marine sediments before destruction by erosion and decomposition. However, the two domed deposits in Sarawak and Sumatra described above are parts of extensive, thick, low-sulfur, fuel-quality peat deposits, which have bases below the levels of rivers on coastal deltas. These are likely to be preserved in their lower part and to become precursors of tropical coal seams of potential economic importance. The lenticular and tabular peat deposits of the Atlantic and Gulf Coastal Plains, which have little chance of survival, have features resembling those in Tertiary peat deposits in alluvial settings of western North America. The quality, shape, and extent of modern and ancient peat deposits are controlled by the same factors - humidity, vegetation type, ground- and surface-water regimes, and physiographic and geologic setting. Thus, a study of modern peat deposits may help in studies of the areal distribution and the thickness and quality of ancient coal beds.

International Journal of Coal Geology↗

USGS1994

US North Slope gas and Asian LNG markets

Prospects for export of liquified natural gas (LNG) from Alaska's North Slope are assessed. Projected market conditions to 2010 show that new LNG capacity beyond announced expansions will be needed to meet regional demand and that supplies will probably come from outside the region. The estimated delivered costs of likely suppliers show that Alaska North Slope gas will not be competitive. The alternative North Slope gas development strategies of transport and sale to the lower 48 states and use on the North Slope for either enhanced oil recovery or conversion to liquids are examined. The alternative options require delaying development until US gas prices increase, exhaustion of certain North Slope oil fields, or advances occur in gas to liquid fuels conversion technology.

Resources Policy↗

USGS1978

Methods for regional assessment of geothermal resources

A consistent, agreed-upon terminology is prerequisite for geothermal resource assessment. Accordingly, we propose a logical, sequential subdivision of the "geothermal resource base", accepting its definition as all the thermal energy in the earth's crust under a given area, measured from mean annual temperature. That part of the resource base which is shallow enough to be tapped by production drilling is termed the "accessible resource base", and it in turn is divided into "useful" and "residual" components. The useful component (i.e. the thermal energy that could reasonably be extracted at costs competitive with other forms of energy at some specified future time) is termed the "geothermal resource". This in turn is divided into "economic" and "subeconomic" components, based on conditions existing at the time of assessment. In the format of a McKelvey diagram, this logic defines the vertical axis (degree of economic feasibility). The horizontal axis (degree of geologic assurance) contains "identified" and "undiscovered" components. "Reserve" is then designated as the identified economic resource. All categories should be expressed in units of thermal energy, with resource and reserve figures calculated at wellhead, prior to the inevitable large losses inherent in any practical thermal use or in conversion to electricity. Methods for assessing geothermal resources can be grouped into 4 classes: (a) surface thermal flux, (b) volume, (c) planar fracture and (d) magmatic heat budget. The volume method appears to be most useful because (1) it is applicable to virtually any geologic environment, (2) the required parameters can in Sprinciple be measured or estimated, (3) the inevitable errors are in part compensated and (4) the major uncertainties (recoverability and resupply) are amenable to resolution in the foreseeable future. The major weakness in all the methods rests in the estimation of how much of the accessible resource base can be extracted at some time in the future. In a manner similar to mineral and fuel assessment, this recoverability is expressed as a "recovery factor". For an ideally permeable hot-water system, the recovery factor may be as much as 50% and seems to be independent of temperature. It must decrease as effective porosity (??e) decreases, but the relation between the two is little more than a guess. On the other hand, for favorable systems like Larderello that produce steam by a mechanism of intergranular vaporization, the recovery factor is probably around 15-20%, decreasing to zero at an effective porosity of zero. According to the anlysis of Bodvarsson (1974), it increases with decreasing reservoir temperature, and as pointed out by Nathenson (1975a) is limited at low temperatures by the need to have sufficient reservoir pressure for extraction and use. The extent to which a geothermal reservoir can be resupplied with heat during "industrial" times of 10-100 yr can be evaluated using simple analytical models. The results, combined with gravity and levelling data of Hunt (1977) for Wairakei and Isherwood (1977) for The Geysers, confirm earlier conclusions by Ramey (1970) and Nathenson (1975a) that resupply to reservoirs producing only steam can be neglected, and the conclusion of Nathenson (1975a) that it may be significant for hot-water systems of high natural discharge. Major subjects that demand continuing investigation include: 1. 1. Determination of recovery factors as functions of temperature and effective porosity, particularly for hot-water systems. 2. 2. Evaluation of fluid recharge and heat resupply by repetitive gravity, levelling and underground temperature surveys in producing geothermal fields. 3. 3. Analysis of the extent to which a recovery factor can be enhanced by stimulation and by use of confined circulation loops. ?? 1979.

Geothermics↗

USGS2007

The geochemistry of pesticides

The mid-1970s marked a major turning point in human history, for it was at that moment that the ability of the Earth’s ecosystems to absorb most of the biological impacts of human activities appears to have been exceeded by the magnitude of those impacts. This conclusion is based partly upon estimates of the rate of carbon dioxide emission during the combustion of fossil fuels, relative to the rate of its uptake by terrestrial ecosystems ( Loh, 2002 ). A very different threshold, however, had already been crossed several decades earlier with the birth of the modern chemical industry, which produced novel substances for which no such natural assimilative capacity existed. Among these new chemical compounds, none has posed a greater challenge to the planet’s ecosystems than synthetic pesticides, compounds that have been intentionally released into the hydrologic system in vast quantities—several hundred million pounds of active ingredient (a.i.) per year in the United States alone ( Donaldson et al. , 2002 )—for many decades. To gauge the extent to which we are currently able to assess the environmental implications of this new development in the Earth’s history, this chapter presents an overview of current understanding regarding the sources, transport, fate, and biological effects of pesticides, their transformation products, and selected adjuvants in the hydrologic system. (Adjuvants are the so-called inert ingredients included in commercial pesticide formulations to enhance the effectiveness of the active ingredients.)

Book chapter↗

USGS2013

Wildfire and landscape change

Wildfire is a worldwide phenomenon that is expected to increase in extent and severity in the future, due to fuel accumulations, shifting land management practices, and climate change. It immediately affects the landscape by removing vegetation, depositing ash, influencing water-repellent soil formation, and physically weathering boulders and bedrock. These changes typically lead to increased erosion through sheetwash, rilling, dry ravel, and increased mass movement in the form of floods, debris flow, rockfall, and landslides. These process changes bring about landform changes as hillslopes are lowered and stream channels aggrade or incise at increased rates. Furthermore, development of alluvial fans, debris fans, and talus cones are enhanced. The window of disturbance to the landscape caused by wildfire is typically on the order of three to four years, with some effects persisting up to 30 years.

Book chapter↗

USGS2019

Lotic freshwater: Rivers

Ecosystems associated with rivers are intricately connected to their entire watershed. The river ecosystem includes the channel of active water flow, floodplain, and riparian and hyporheic zones. This ecosystem is shaped by interactions among the natural flow of water, sediments within the river and entering the river, and large wood regimes within the riparian zone. River integrity describes the ability of a river ecosystem to adjust to changes in these elements and through these adjustments maintain the habitat, disturbance regime, and connectivity necessary to sustain native biotic communities. Riverine food webs conceptualize the coupling between the physical environment and biotic communities and can be used to examine recovery from disturbance, variation in the structure of communities, and sources of energy that fuel metabolism within the ecosystem.

Book chapter↗

USGS2026

The future for reptiles: Advances and challenges in the Anthropocene

The future for the Reptilia will be one of continued discovery of the extant diversity of species in every group and continued challenges for their conservation. Most species will persist, albeit in smaller and increasingly fragmented geographic ranges, and active conservation measures can help to ensure survival of highly vulnerable species. There are more than 12,440 documented species of reptiles, up from 10,500 only seven years ago. Transfer of laboratory techniques, computational resources, and access to literature to herpetologists throughout the world is fueling the increase in systematic studies of reptiles. The bulk of reptiles are the squamates, lizards and snakes, with impressive diversity on most continents. Habitat loss, landscape fragmentation, exploitation, invasive species, environmental contamination, and global warming are persistent challenges to all biodiversity, including reptiles. Endemism, ecological specialization, and restricted ranges generally make species more vulnerable to anthropogenic disturbances. Moreover, the natural history information that is so important for informing conservation aims is lacking for most newly described forms, whether they represent completely novel discoveries or result from taxonomic revisions. The major lineages of reptiles exhibit enormous variation in life history traits, ranging from extremely long-lived species with low fecundity to those with short generation times and high fecundity. Reptiles vary in their degree of ecological specialization, and many live in difficult-to-sample habitats. It is implausible, if not impossible, to gather detailed information on thousands of species of reptiles, many of which are secretive and difficult to study. However, evaluating where species are likely to fit along life history gradients of time to maturity, brood size, and frequency of reproduction reveals much about their abilities to persist in the face of anthropogenic disturbance. Combined with information on geographic distribution and the severity of anthropogenic pressures, consideration of life history strategies reveals important implications for conservation of reptile species. Modern approaches to conservation of reptiles, including conservation translocations, regulation of the international trade in reptiles, management of imperiled species in the context of landscapes, progress in confronting emerging diseases, and resolving human-wildlife conflict in all its forms can help ensure the persistence of the great diversity of the Reptilia in the Anthropocene.

Book chapter↗

USGS2018

Lead and strontium isotopes as monitors of anthropogenic contaminants in the surficial environment

Isotopic discrimination can be an effective tool in establishing a direct link between sources of Pb contamination and the presence of anomalously high concentrations of Pb in waters, soils, and organisms. Residential wells supplying water containing up to 1600 ppb Pb to houses built on the former Mohr orchards commercial site, near Allentown, Pennsylvania, United States, were evaluated to discern anthropogenic from geogenic sources. Pb and Sr isotopic data and REE data were determined for waters from residential wells, test wells (drilled for this study), and surface waters from pond and creeks. Local soils, sediments, bedrock, Zn-Pb mineralization and coal were also analyzed, together with locally used Pb-As pesticide. Pb isotope data for residential wells, test wells, and surface waters show substantial overlap with Pb data reflecting anthropogenic actions (e.g., burning fossil fuels, industrial and urban processing activities). Limited contributions of Pb from bedrock, soils, and pesticides are evident. High Pb concentrations in the residential waters are likely related to Pb in groundwater accumulating in sediment in the residential water tanks. The Pb isotope features of waters in underlying shallow aquifers that supply residential wells in the region are best interpreted as reflecting a legacy of anthropogenic Pb rather than geogenic Pb.

Book chapter↗

USGS2017

Terrestrial subaqueous seafloor dunes: Possible analogs for Venus

Dunes on Venus, first discovered with Magellan Synthetic Aperture Radar (SAR) in the early 1990s, have fueled discussions about the viability of Venusian dunes and aeolian grain transport. Confined to two locations on Venus, the existence of the interpreted dunes provides evidence that there could be transportable material being mobilized into aeolian bedforms at the surface. However, because of the high-pressure high-temperature surface conditions, laboratory analog studies are difficult to conduct and results are difficult to extrapolate to full-sized, aeolian bedforms. Field sites of desert dunes, which are well-studied on Earth and Mars, are not analogous to what is observed on Venus because of the differences in the fluid environments. One potentially underexplored possibility in planetary science for Venus-analog dune fields could be subaqueous, seafloor dune fields on Earth. Known to the marine geology communities since the early 1960s, seafloor dunes are rarely cited in planetary aeolian bedform literature, but could provide a necessary thick-atmosphere extension to the classically studied aeolian dune environment literature for thinner atmospheres. Through discussion of the similarity of the two environments, and examples of dunes and ripples cited in marine literature, we provide evidence that subaqueous seafloor dunes could serve as analogs for dunes on Venus. Furthermore, the evidence presented here demonstrates the usefulness of the marine literature for thick-atmosphere planetary environments and potentially for upcoming habitable worlds and oceanic environment research program opportunities. Such useful cross-disciplinary discussion of dune environments is applicable to many planetary environments (Earth, Mars, Venus, Titan, etc.) and potential future missions.

Aeolian Research↗

USGS2022

Prairie wetlands as sources or sinks of nitrous oxide: Effects of land use and hydrology

National and global greenhouse gas (GHG) budgets are continually being refined as data become available. Primary sources of the potent GHG nitrous oxide (N 2 O) include agricultural soil management and burning of fossil fuels, but comprehensive N 2 O budgets also incorporate less prominent factors such as wetlands. Freshwater wetland GHG flux estimates, however, have high uncertainty, and wetlands have been identified as both sources and sinks. Here, we analyzed a regional database of >26,000 N 2 O chamber flux measurements sampled across >150 wetlands from the Prairie Pothole Region (PPR) in the Great Plains of North America. Our goal was to identify important land use and hydrologic drivers of N 2 O flux to help reduce uncertainty in N 2 O models, and to incorporate these drivers into an upscaled estimate of wetland N 2 O emissions from the U.S. portion of the PPR. Within individual wetlands, exposed soils with no standing water, such as along wetland edges, were hotspots that accounted for greater than 90% of wetland N 2 O emissions. In contrast wet (i.e., ponded) areas had minimal or negative N 2 O flux. N 2 O flux from wetlands nested within croplands (16.3–17.3 μg N 2 O m −2 hr −1 ) was, in some instances, nearly double that from wetlands within grasslands (9.2–14.4 μg N 2 O m −2 h −1 ). We estimated that seasonal N 2 O flux from PPR wetlands equated to roughly 0.2% (1.04 Tg CO 2 equivalents) of the U.S. N 2 O budget (c. 2019). Overall, even though PPR wetlands are a small net source of N 2 O to the atmosphere, their emissions are negligible relative to agricultural soil management. Policy and management to restore wetland hydrology and surrounding uplands from cropland to grasslands can reduce landscape N 2 O fluxes. Future activities focused on wetland N 2 O flux would benefit from inclusion of adjacent land use and hydrologic factors, as well as from incorporation of temporally dynamic ponded wetland areas.

Iowa, Minnesota, Montana, North Dakota, South Dako↗

USGS2009

Soil geochemical signature of urbanization and industrialization – Chicago, Illinois, USA

The concentrations of 45 elements in ambient (not obviously disturbed) surface soils were determined for 57 sites distributed throughout the city of Chicago, Illinois in the upper Midwestern United States. These concentrations were compared to soils from 105 sites from a largely agricultural region within a 500-km radius surrounding the city and to soils collected from 90 sites across the state of Illinois. Although the bulk composition of the Chicago urban soils reflects largely natural sources, the soils are significantly enriched in many trace elements, apparently from anthropogenic sources. The median concentration of Pb in Chicago soils is 198 mg/kg, a 13-fold enrichment compared to regional concentrations. Zinc (median 235 mg/kg), Cu (59 mg/kg), and Ni (31 mg/kg) are also enriched from 2- to 4-fold in Chicago soils and all four elements show strong mutual correlations. These elevated concentrations are most likely related to vehicular and roadway sources and represent uneven distribution across the city as airborne material. Other airborne particulate material from a combination of fossil fuel combustion, waste incineration, and steel production may contribute to apparent elevated concentrations in Chicago soil of Fe (median 2.9%), Mo (5 mg/kg), V (82 mg/kg) and S (0.09%). Chicago soils are enriched from about 1.6- to 3-fold in these elements. Enrichments in P and Se may be caused by direct addition of phosphate fertilizer to parklands, lawns and gardens. The density of the sampling (1 site per 10 km 2 ) is inadequate to define the distribution of the observed enrichments within the city or to predict soil compositions for most of the areas between sample sites, but does provide a statistically significant signature of the history of urban and industrial activity within the city in contrast to the surrounding agricultural lands.

Illinois↗

USGS2012

Acidification of Earth: An assessment across mechanisms and scales

In this review article, anthropogenic activities that cause acidification of Earth’s air, waters, and soils are examined. Although there are many mechanisms of acidification, the focus is on the major ones, including emissions from combustion of fossil fuels and smelting of ores, mining of coal and metal ores, and application of nitrogen fertilizer to soils, by elucidating the underlying biogeochemical reactions as well as assessing the magnitude of the effects. These widespread activities have resulted in (1) increased CO 2 concentration in the atmosphere that acidifies the oceans; (2) acidic atmospheric deposition that acidifies soils and bodies of freshwater; (3) acid mine drainage that acidifies bodies of freshwater and groundwaters; and (4) nitrification that acidifies soils. Although natural geochemical reactions of mineral weathering and ion exchange work to buffer acidification, the slow reaction rates or the limited abundance of reactant phases are overwhelmed by the onslaught of anthropogenic acid loading. Relatively recent modifications of resource extraction and usage in some regions of the world have begun to ameliorate local acidification, but expanding use of resources in other regions is causing environmental acidification in previously unnoticed places. World maps of coal consumption, Cu mining and smelting, and N fertilizer application are presented to demonstrate the complex spatial heterogeneity of resource consumption as well as the overlap in acidifying potential derived from distinctly different phenomena. Projected population increase by country over the next four decades indicates areas with the highest potential for acidification, so enabling anticipation and planning to offset or mitigate the deleterious environmental effects associated with these global shifts in the consumption of energy, mineral, and food resources.

Applied Geochemistry↗