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At least 109 records · Page 6Linked to original sources

USGS2010

Mg isotope constraints on soil pore-fluid chemistry: Evidence from Santa Cruz, California

Mg isotope ratios ( 26 Mg/ 24 Mg) are reported in soil pore-fluids, rain and seawater, grass and smectite from a 90 kyr old soil, developed on an uplifted marine terrace from Santa Cruz, California. Rain water has an invariant 26 Mg/ 24 Mg ratio (expressed as δ26 Mg> δ26 Mg ) at −0.79 ± 0.05‰, identical to seawater δ26 Mg> δ26 Mg . Detrital smectite (from the base of the soil profile, and therefore unweathered) has a δ26Mg"> δ26Mg value of 0.11‰, potentially enriched in 26 Mg by up to 0.3‰ compared to the bulk silicate Earth Mg isotope composition (although within the range of all terrestrial silicates). The soil pore-waters show a continuous profile with depth for δ26 Mg> δ26 Mg , ranging from −0.99‰ near the surface to −0.43‰ at the base of the profile. Shallow pore-waters (<1 m) have δ26 Mg> δ26 Mg values that are similar to, or slightly lower than the rain waters. This implies that the degree of biological cycling of Mg in the pore-waters is relatively small and is quantified as <32%, calculated using the average Mg isotope enrichment factor between grass and rain ( δ26 Mggrass- δ26 Mgrain> δ26 Mggrass- δ26 Mgrain ) of 0.21‰. The deep pore-waters (1–15 m deep) have δ26 Mg> δ26 Mg values that are intermediate between the smectite and rain, ranging from −0.76‰ to −0.43‰, and show a similar trend with depth compared to Sr isotope ratios. The similarity between Sr and Mg isotope ratios confirms that the Mg in the pore-waters can be explained by a mixture between rain and smectite derived Mg, despite the fact that Mg and Sr concentrations may be buffered by the exchangeable reservoir. However, whilst Sr isotope ratios in the pore-waters span almost the complete range between mineral and rain inputs, Mg isotopes compositions are much closer to the rain inputs. If Mg and Sr isotope ratios are controlled uniquely by a mixture, the data can be used to estimate the mineral weathering inputs to the pore-waters, by correcting for the rain inputs. This isotopic correction is compared to the commonly used chloride correction for precipitation inputs. A consistent interpretation is only possible if Mg isotope ratios are fractionated either by the precipitation of a secondary Mg bearing phase, not detected by conventional methods, or selective leaching of 24 Mg from smectite. There is therefore dual control on the Mg isotopic composition of the pore-waters, mixing of two inputs with distinct isotopic compositions, modified by fractionation. The data provide (1) further evidence for Mg isotope fractionation at the surface of the Earth and (2) the first field evidence of Mg isotope fractionation during uptake by natural plants. The coherent behaviour of Mg isotope ratios in soil environments is encouraging for the development of Mg isotope ratios as a quantitative tracer of both weathering inputs of Mg to waters, and the physicochemical processes that cycle Mg, a major cation linked to the carbon cycle, during continental weathering.

California↗

USGS2025

Occurrence of pesticides in Oregon coastal waters

Pesticides are used globally for a wide range of applications including agricultural, forestry, roadsides, freshwater systems, and personal use. While pesticides have ensured efficient crop production, they are frequently transported away from application sites and are found in almost all terrestrial and aquatic environments. Pesticides are frequently detected in watersheds and rivers, but there is limited research on pesticide presence in United States (U.S.) marine environments. To address these data gaps, this study documents pesticide occurrence in U.S. coastal waters, providing new understanding of pesticide contamination in offshore environments. Polar organic chemical integrative samples (POCIS) were deployed at five sites along the Oregon, U.S. coast to examine the occurrence of pesticides. Between two and seven different pesticides were detected at every site, with herbicides diuron, and atrazine, and fungicides carbendazim, propiconazole, and tebuconazole being the most frequently detected at three sites. The prevalence of herbicides and fungicides in coastal waters indicates a connection between terrestrial pesticide practices and marine contamination. These findings provide new insights into the presence of pesticides in coastal nearshore and offshore waters and suggest that a comprehensive monitoring effort could enhance our understanding of sources, transport, and pesticide risks for marine species both nearshore and offshore.

Oregon↗

USGS1994

Humic and fulvic acids: sink or source in the availability of metals to the marine bivalves Macoma balthica and Potamocorbula amurensis ?

Humic acids (HA) and fulvic acids (FA) are common forms of organic matter in marine sediments, and are routinely ingested by deposit- and suspension-feeding animals. These compounds may be a sink for metals, implying that once metals are bound to humic substances they are no longer available to food webs. A series of experiments was conducted to quantitatively examine this premise using 2 estuarine bivalves from San Francisco Bay, USA: the suspension feeder Potarnocorbula arnurensis and the facultative deposit feeder Macoma balthica . HA and FA, isolated from marine sediments, were bound as organic coatings to either hydrous ferric oxides (HFO) or silica particles. Cd and Cr(II1) were adsorbed to the organic coatings or directly to uncoated HFO and silica particles. Pulse-chase laboratory feeding expenments using 109 Cd and 51 Cr(III) were then conducted to determine absorption efficiencies of Cd and Cr for individual specimens using each of the particle types. The results demonstrated that: (1) absorption of Cr(I1I) from all types of non-living particles was consistently low (< 11%). Ingested Cd showed greater bioavailability than Cr(IIl), perhaps due to differences in metal chemistry. (2) Bivalves absorbed Cd bound to uncoated HFO or silica particles (i.e. with no HA or FA present). (3) The presence of organic coatings on particles reduced Cd bioavailabhty compared with uncoated particles. (4) Both geochemical and biological conditions affected the food chain transfer of Cd. The data suggest that in marine systems inorganic and organic-coated particles are predominantly a sink for Cr in sediments. In the transfer of Cd to consumer animals, inorganic particles and humic substances can act as a link (although not a highly efficient one) under oxidized conditions.

Marine Ecology Progress Series↗

USGS1998

The chemical evolution of Kurnub Group palcowater in the Sinai-Negev province - A mass balance approach

The chemical evolution of the Kurnub Group paleowater was studied starting from rainwater in recharge areas of the Sinai and along groundwater flowpaths leading to the natural outlets of this regional aquifer. This was achieved by investigating the chemical composition of groundwater, ionic ratios, degrees of saturation with common mineral species, normative analysis of dissolved salts and by modeling of rock/water interaction and mixing processes occurring along groundwater flow paths. The initial groundwater composition used is from the Nakhel well in Sinai. It evolves from desert rainwater percolating through typical Kurnub Group lithology in Sinai. This rainwater dissolves mainly gypsum, halite and dolomite together with smaller amounts of marine aerosol and K-feldspar. At the same time it precipitates calcite, SiO2, smectite and degasses CO2. Between the area of Nakhel and the northern Negev the chemistry of Kurnub Group waters is influenced by dissolution of halite and lesser amounts of gypsum of surficial origin in recharge areas, small amounts of feldspars and of dolomite cement in sandstones eroded from the Arabo-Nubian igneous massif of Sinai and organic degradation-derived CO2. Concomitantly, there is precipitation of calcite, smectite, SiO2 and probably analcime characteristic of sediments in continental closed basins. North of the Negev, the Kurnub Group fluids are diluted and altered by mixing with Judea Group aquifer groundwaters. On the E there is mixing with residual brines from the water body ancestral to the Dead Sea, prior to discharge into the Arava valley. Rock/water interaction indicated by NETPATH and PHREEQC modeling is in agreement with lithology and facies changes previously observed in the Kurnub Group sequence.

Applied Geochemistry↗

USGS2014

USGS Field Activities 12BHM01, 12BHM02, 12BHM03, 12BHM04, and 12BHM05 on the West Florida Shelf, in February, April, May, June, and August 2012

Atmospheric carbon dioxide (CO 2 ) is absorbed by the ocean’s surface where it combines with seawater to form a weak, naturally occurring acid called carbonic acid (H 2 CO 3 ). Increasing carbon dioxide in the atmosphere results in the absorption of more CO 2 by the ocean and, therefore, increases in the acidity of seawater. This process, known as ocean acidification, has the potential to elicit change in ecosystems and organisms by disrupting biological processes. For example, ocean acidification is a problem for marine organisms such as corals, foraminifera, and algae that precipitate calcium carbonate to form their skeletons and shells (Kleypas and others, 2006). The effects are related to corresponding changes in the carbonate saturation state (Ω), where Ω is the ratio of the ion concentration product (Ca 2+ x CO 3 2- ) to the stoichiometric aragonite solubility product (K*sp) (Langdon and Atkinson, 2005). Because pH and CO 3 2- are strongly interdependent through the inorganic carbon system, the decrease in pH will cause a proportionally greater decrease in CO 3 2- . Globally, ocean acidification is occurring faster than at any time in the last 300 million years (Broeker and others, 1979). Recent evidence indicates that individual oceans are responding at different rates, depending on physical and biological processes. For example in the Arctic Ocean, the rate of saturation state decrease was 2.1 percent per year between 1997 and 2010 (Robbins and others., 2013) in an area as large as Montana, largely because of increases in melt of ice, versus the average rate observed for the Pacific Ocean (0.36 percent per year) (Feely and others, 2012). Unfortunately, comparative data sets over multiyear time frames are often not available because time series baseline carbon information has not been collected in many oceans. Data are needed in subtropical latitudes where carbonate saturation states are already naturally low and fluctuate seasonally. These data will help construct a baseline for the assessment of future changes. As part of the U.S. Geological Survey (USGS) Coastal and Marine Geology Program project "R esponse of Florida Shelf Ecosystems to Climate Change " and in partnership with Kendra Daly, University of South Florida ( USF ), data on surface ocean carbonate chemistry were collected on five cruises along transects on the shallow inner west Florida shelf and northern Gulf of Mexico in 2012. Data from the 2011 cruises were also published (Robbins and others., 2013). The data collected allows the USGS, National Oceanic and Atmospheric Administration ( NOAA ), and USF scientists to map variations in ocean chemistry including carbonate saturation states along designated tracks. The USGS also partners with NOAA and the National Aeronautics and Space Administration ( NASA ) to model air-sea flux as part of a Gulf of Mexico Carbon Synthesis project led by NASA.

Florida↗

USGS2017

Application of molluscan analyses to the reconstruction of past environmental conditions in estuaries

Molluscs possess a number of attributes that make them an excellent source of past environmental conditions in estuaries: they are common in estuarine environments; they typically have hard shells and are usually well preserved in sediments; they are relatively easy to detect in the environment; they have limited mobility as adults; they grow by incremental addition of layers to their shells; and they are found in all the major environments surrounding estuaries—terrestrial, freshwater, brackish, and marine waters. Analysis of molluscan assemblages can contribute information about past changes in sea level, climate, land use patterns, anthropogenic alterations, salinity, and other parameters of the benthic habitat and water chemistry within the estuary. High-resolution (from less than a day to annual) records of changes in environmental parameters can be obtained by analyzing the incremental growth layers in mollusc shells (sclerochronology). The shell layers retain information on changes in water temperature, salinity, seasonality, climate, river discharge, productivity, pollution and human activity. Isotopic analyses of mollusc shell growth layers can be problematic in estuaries where water temperatures and isotopic ratios can vary simultaneously; however, methods are being developed to overcome these problems. In addition to sclerochronology, molluscs are important to Holocene and Pleistocene estuarine palaeoenvironmental studies because of their use in the development of age models through radiocarbon dating, amino acid racemization, uranium-thorium series dating, and electron spin resonance (ESR) dating.

Book chapter↗

USGS2023

The Far-Field imprint of the late Paleozoic Ice Age, its demise, and the onset of a dust-house climate across the Eastern Shelf of the Midland Basin, Texas

The late Paleozoic is a period of pronounced climatic and tectonic change, characterized by the onset and disappearance of continental-scale glaciers across polar Gondwana, the formation of Pangea, and widespread large igneous province volcanism. The low-latitude equatorial tropics are assumed to be places of persistent warm and wet climatic conditions throughout the Phanerozoic, which through intense silicate weathering, exert a major influence on Earth’s climate via the consumption of atmospheric carbon through carbonic hydrolytic weathering, formation of clay minerals and deliverability of alkalinity to ocean basins. Here we investigate the late Paleozoic sedimentary record of the Eastern Shelf of the Midland Basin in order to refine the climatic and provenance record of this region. The Eastern Shelf of the Midland Basin was situated within the equatorial tropics throughout the late Paleozoic and was connected to the open ocean through a network of fluvial systems that drained into the marine Midland Basin. We present new U-Pb zircon geochronology (19 samples, 2591 analyses) and sedimentary petrography (11 samples, 5800 grain counts), which we integrate with previously published paleobotany, paleosol chemistry and clay mineralogy to provide a holistic climate and tectonic record from this region. We observe major changes in sedimentary processes that we attribute to the formation of Pangea, eustatic changes linked to a dynamic high-latitude glaciation and teleconnections with low latitude hydrology, and a long-term shift in the Earth climate system all of which result in a dynamic sediment provenance history. Late Pennsylvanian and earliest Permian deposits are enriched in zircons with local affinity and interpreted to reflect local uplift and repeat incision across the basin margin, the latter a result of glacioeustatic forcing during an “everwet” climate. A major paleoenvironmental shift occurs in the late early Permian, which is reflected by the transition from fluvial to mixed fluvial-aeolian and ultimately aeolian dominant sedimentation by the late Permian. The transition from fluvial to aeolian dominant sedimentation is accompanied by a change in clay chemistry, sedimentary rock textual maturity, paleosol morphology and a threefold increase in Paleozoic zircons in the mid to late Permian strata. Widespread loess deposits across equatorial Pangea during the Permian have been used to argue for the possibility of equatorial glaciers situated in highland settings during the early Permian. Conversely, our data suggest initiation of a substantial component of aeolian deposition across the field areas, which is coincident with widespread ice loss across high latitude Gondwana, and ultimately highlights the teleconnections between high latitude glaciation and the low latitude hydrologic cycle.

Texas↗

USGS2016

Cessation of oil exposure in harlequin ducks after the Exxon Valdez oil spill: Cytochrome P4501A biomarker evidence

The authors quantified hepatic hydrocarbon-inducible cytochrome P4501A (CYP1A) expression, as ethoxyresorufin-O-deethylase (EROD) activity, in wintering harlequin ducks ( Histrionicus histrionicus ) captured in Prince William Sound, Alaska (USA), during 2011, 2013, and 2014 (22–25 yr following the 1989 Exxon Valdez oil spill). Average EROD activity was compared between birds from areas oiled by the spill and those from nearby unoiled areas. The present study replicated studies conducted from 1998 to 2009 demonstrating that harlequin ducks using areas oiled in 1989 had elevated EROD activity, indicative of oil exposure, up to 2 decades post spill. In the present study, it was found that average EROD activity during March 2011 was significantly higher in wintering harlequin ducks captured in oiled areas relative to unoiled areas, which the authors interpret to indicate that harlequin ducks continued to be exposed to residual Exxon Valdez oil up to 22 yr after the original spill. However, the 2011 results also indicated reductions in exposure relative to previous years. Average EROD activity in birds from oiled areas was approximately 2 times that in birds from unoiled areas in 2011, compared with observations from 2005 to 2009, in which EROD activity was 3 to 5 times higher in oiled areas. It was also found that average EROD activity during March 2013 and March 2014 was not elevated in wintering harlequin ducks from oiled areas. The authors interpret these findings to indicate that exposure of harlequin ducks to residual Exxon Valdez oil abated within 24 yr after the original spill. The present study finalizes a timeline of exposure, extending over 2 decades, for a bird species thought to be particularly vulnerable to oil contamination in marine environments

Alaska↗

USGS2016

Walter Rowe Courtenay, Jr. (1933–2014)

WALTER R. COURTENAY, JR., ichthyologist and retired professor, Florida Atlantic University, Boca Raton, Florida, died in Gainesville, Florida, on 30 January 2014 at age 80. Walt was born in Neenah, Wisconsin, on 6 November 1933, son of Walter and Emily Courtenay. Walt's interest in fish began at a young age as evidenced by a childhood diary in which at 13 years of age he wrote about his first catch—a two-and-a-half pound “pike” from Lake Winnebago. When Walt turned ten, the family moved from Wisconsin to Nashville, Tennessee, the move precipitated by his father accepting a position as pastor of the First Presbyterian Church. During those early days in Nashville, Walt's father would take summers off and travel to Michigan to teach at Camp Miniwanca along the shore of Lake Michigan where father and son honed their angling skills. It was also at that time Walt's father had definite views on what his son should be doing in adult life—in Walt's case it was to become a medical doctor. However, his Woods Hole internship in marine biology and oceanography toward the end of his undergraduate years was a transformative experience for him so much so that he abandoned all ideas of becoming a medical doctor and instead specialized in ichthyology and oceanography. Apart from the inherent interest and opportunities Woods Hole opened to him, being back at the shore of a large body of water, in this case the Atlantic Ocean, was far more interesting than sitting in lectures on organic chemistry. With that, Walt completed his B.A. degree at Vanderbilt University in 1956. In 1960 while in graduate school in Miami, Walt met and married Francine Saporito, and over the next several years had two children, Walter III and Catherine. He went on to receive his M.S. in 1961 from The Rosenstiel School of Marine and Atmospheric Science at the University of Miami on the systematics of the genus Haemulon (grunts) and his Ph.D. degree in 1965 working under his advisor C. Richard “Dick” Robins, also at Miami, with his dissertation entitled “Atlantic Fishes of the Genus Rypticus (Grammistidae): Systematics and Osteology.” Dick and wife Catherine Robins, also a fellow biologist, thought of him as a great friend to have. They fondly recalled that those of us who knew Walt in his early grad student days valued his sense of humor and unmistakable laugh, much of which was directed at bureaucratic foolishness and pomposity. However, he also had a very serious side when it came to justice and responsibility.

Copeia↗

USGS2004

CO 2 mitigation via accelerated limestone weathering

We evaluate accelerated weathering of limestone (AWL: CO 2 + CaCO 3 + H 2 O=> Ca 2+ + 2HCO 3 - ) as a low-tech, inexpensive, high-capacity, environmentally-friendly CO 2 capture and sequestration technology. With access to seawater and limestone being essential to this approach, significant limestone resources are close to most CO 2 -emitting power plants along the coastal US. Waste fines, representing more than 20% of current US crushed limestone production (>10 9 tonnes/yr), could be used as an inexpensive source of AWL carbonate. Under such circumstances CO 2 mitigation cost could be as low as $3-$4/tonne. More broadly, 10-20% of US point-source CO 2 emissions could be treated at $20-$30/tonne CO 2 . AWL end-solution disposal in the ocean would significantly reduce effects on ocean pH and carbonate chemistry relative to those caused by direct atmospheric or ocean CO 2 disposal. Indeed, the increase in ocean Ca 2+ and bicarbonate offered by AWL should enhance growth of corals and other calcifying marine organisms.

Conference Paper↗

USGS2009

The Columbia River Basalt Group: from the gorge to the sea

Miocene flood basalts of the Columbia River Basalt Group inundated eastern Washington, Oregon, and adjacent Idaho between 17 and 6 Ma. Some of the more voluminous flows followed the ancestral Columbia River across the Cascade arc, Puget-Willamette trough, and the Coast Range to the Pacific Ocean. We have used field mapping, chemistry, and paleomagnetic directions to trace individual flows and flow packages from the Columbia River Gorge westward into the Astoria Basin, where they form pillow palagonite complexes and mega-invasive bodies into older marine sedimentary rocks. Flows of the Grande Ronde, Wanapum, and Saddle Mountains Basalts all made it to the ocean; at least 33 flows are recognized in the western Columbia River Gorge, 50 in the Willamette Valley, 16 in the lower Columbia River Valley, and at least 12 on the Oregon side of the Astoria Basin. In the Astoria Basin, the basalt flows loaded and invaded the wet marine sediments, producing peperite breccias, soft sediment deformation, and complex invasive relations. Mega-invasive sills up to 500 m thick were emplaced into strata as old as Eocene, and invasive dikes up to 90 m thick can be traced continuously for 25 km near the basin margin. Mega-pillow complexes up to a kilometer thick are interpreted as the remains of lava deltas that prograded onto the shelf and a filled submarine canyon southeast of Astoria, possibly providing the hydraulic head for injection of invasive sills and dikes at depth.

Oregon;Washington↗

USGS2019

A 20-year record of water chemistry in an alpine setting, Mount Emmons, Colorado, USA

From 1997 to the present, the U.S. Geological Survey and other agencies have been collecting water samples for chemical analyses on Mount Emmons in central Colorado, USA. The geology of Mount Emmons is dominated by Upper Cretaceous to Paleogene sediments of marine to continental origin, with felsic intrusive rocks interrupting the sedimentary block. Extensive sulphide-rich alteration accompanied the intrusive events and forms an alteration halo in the sediments. Weathering of these sulphide minerals has led to numerous springs and seeps with a naturally low pH and high concentrations of metals, especially Fe and Zn. Superimposed on the natural geochemical signature are acid, metal-rich drainages from several mines and drill holes. Thus, streams on Mt. Emmons have a mix of natural and anthropogenic metal sources. Nearly 450 samples compose the database, with numerous sample locations replicated from the late 1990s to the present. Although there does not appear to be any temporal pattern in the data, consistent spatial variations are observed that allow us to characterize the natural and anthropogenic water sources.

Colorado↗

USGS2008

Atmospheric Deposition and Surface-Water Chemistry in Mount Rainier and North Cascades National Parks, U.S.A., Water Years 2000 and 2005-2006

High-elevation aquatic ecosystems in Mount Rainier and North Cascades National Parks are highly sensitive to atmospheric deposition of nitrogen and sulfur. Thin, rocky soils promote fast hydrologic flushing rates during snowmelt and rain events, limiting the ability of basins to neutralize acidity and assimilate nitrogen deposited from the atmosphere. Potential effects of nitrogen and sulfur deposition include episodic or chronic acidification of terrestrial and aquatic ecosystems. In addition, nitrogen deposition can cause eutrophication of water bodies and changes in species composition in lakes and streams. This report documents results of a study performed by the U.S. Geological Survey, in cooperation with the National Park Service, of the effects of atmospheric deposition of nitrogen and sulfur on surface-water chemistry in Mount Rainier and North Cascades National Parks. Inorganic nitrogen in wet deposition was highest in the vicinity of North Cascades National Park, perhaps due to emissions from human sources and activities in the Puget Sound area. Sulfur in wet deposition was highest near the Pacific coast, reflecting the influence of marine aerosols. Dry deposition generally accounted for less than 30 percent of wet plus dry inorganic nitrogen and sulfur deposition, but occult deposition (primarily fog) represents a potentially substantial unmeasured component of total deposition. Trend analyses indicate inorganic nitrogen in wet deposition was relatively stable during 1986-2005, but sulfur in wet deposition declined substantially during that time, particularly after 2001, when emissions controls were added to a large powerplant in western Washington. Surface-water sulfate concentrations at the study site nearest the powerplant showed a statistically significant decrease between 2000 and 2005-06, but there was no statistically significant change in alkalinity, indicating a delayed response in surface-water alkalinity. Seasonal patterns in surface-water chemistry and streamflow are strongly influenced by melting of seasonal snowpacks, which release large amounts of dilute, slightly acidic water to terrestrial and aquatic ecosystems during spring snowmelt. Concentrations of sulfate, alkalinity, and base cations in surface water declined rapidly during snowmelt, then gradually recovered during summer and fall. Preferential elution of acidic solutes from the snowpack at the beginning of snowmelt may cause episodic acidification in small alpine streams; evidence is provided by a stream sample collected at one of the sites during spring 2006 that was acidic (pH = 4.8, alkalinity = -18 microequivalents per liter) and had high concentrations of nitrate and sulfate and low concentrations of weathering products. Rain-on-snow events caused sharp declines in specific conductance, which was measured continuously using an in-stream sensor. A strong correlation was observed between measured specific conductance and measured alkalinity (r2 = 0.76), permitting estimation of alkalinity from specific-conductance data using a regression equation. Estimated alkalinity declined by an order of magnitude during the rain-on-snow events, in one case to 8 microequivalents per liter. Actual declines in alkalinity might be greater because the regression equation accounts only for dilution effects; at low concentrations, the relation between specific conductance and alkalinity is likely to be nonlinear and have a negative intercept (negative alkalinity). Thus, episodic acidification is possible during rain-on-snow events. The scale of episodic acidification is unknown, but if it occurs, it could have detrimental effects on aquatic life and amphibians. Historical lake-survey data indicate that most lakes are oligotrophic and have low nitrogen and phosphorus concentrations. Nitrogen limitation is more common in lakes in Mount Rainier National Park than in North Cascades National Park due to higher nitrate concentrations at North Cascades. T

Scientific Investigations Report↗

USGS2012

Atmospheric inputs to watersheds of the Luquillo Mountains in eastern Puerto Rico: Chapter D in Water quality and landscape processes of four watersheds in eastern Puerto Rico

Twenty years of precipitation-chemistry data from the National Atmospheric Deposition Program site at El Verde, Puerto Rico, demonstrate that three major sources control the composition of solutes in rain in eastern Puerto Rico. In order of importance, these sources are marine salts, temperate contamination from the Northern Hemisphere, and Sahara Desert dust. Marine salts are a source of roughly 82 percent of the ionic charge in precipitation; marine salt inputs are greatest in January. Evaluation of 15 years of U.S. Geological Survey data for four watersheds in eastern Puerto Rico suggests that large storms, including hurricanes, are associated with exceptionally high chloride concentrations in stream waters. Some of these storms were missed in sampling by the National Atmospheric Deposition Program, and therefore its data on the marine contribution likely underestimate chloride. The marine contribution is a weak source of acidity. Temperate contamination contributes about 10 percent of the ionic charge in precipitation; contaminants are primarily nitrate, ammonia, and sulfate derived from various manmade and natural sources. Peak deposition of temperate contaminants is during January, April, and May, months in which strong weather fronts arrive from the north. Temperate contamination, a strong source of acidity, is the only component that is increasing through time. Sahara Desert dust provides 5 percent of the ionic charge in precipitation; it is strongly seasonal, peaking in June and July during times of maximum dust transport from the Sahara and sub-Saharan regions. This dust contributes, on average, enough alkalinity to neutralize the acidity in June and July rains.

Professional Paper↗

USGS2000

Development and evaluation of consensus-based sediment effect concentrations for polychlorinated biphenyls

Sediment-quality guidelines (SQGs) have been published for polychlorinated biphenyls (PCBs) using both empirical and theoretical approaches. Empirically based guidelines have been developed using the screening-level concentration, effects range, effects level, and apparent effects threshold approaches. Theoretically based guidelines have been developed using the equilibrium-partitioning approach. Empirically-based guidelines were classified into three general categories, in accordance with their original narrative intents, and used to develop three consensus-based sediment effect concentrations (SECs) for total PCBs (tPCBs), including a threshold effect concentration, a midrange effect concentration, and an extreme effect concentration. Consensus-based SECs were derived because they estimate the central tendency of the published SQGs and, thus, reconcile the guidance values that have been derived using various approaches. Initially, consensus-based SECs for tPCBs were developed separately for freshwater sediments and for marine and estuarine sediments. Because the respective SECs were statistically similar, the underlying SQGs were subsequently merged and used to formulate more generally applicable SECs. The three consensus-based SECs were then evaluated for reliability using matching sediment chemistry and toxicity data from field studies, dose-response data from spiked-sediment toxicity tests, and SQGs derived from the equilibrium-partitioning approach. The results of this evaluation demonstrated that the consensus-based SECs can accurately predict both the presence and absence of toxicity in field-collected sediments. Importantly, the incidence of toxicity increases incrementally with increasing concentrations of tPCBs. Moreover, the consensus-based SECs are comparable to the chronic toxicity thresholds that have been estimated from dose-response data and equilibrium-partitioning models. Therefore, consensus-based SECs provide a unifying synthesis of existing SQGs, reflect causal rather than correlative effects, and accurately predict sediment toxicity in PCB-contaminated sediments.

Environmental Toxicology and Chemistry↗

USGS2026

Metalloporphyrins in the Eagle Ford Shale

Using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), Zheng et al. (2018, Energy & Fuels 32, 10382) reported abundant iron and vanadyl porphyrins and minor amounts of gallium and nickel porphyrins in asphaltenes extracted from a single lower Eagle Ford Shale sample. This finding is most unusual as iron and gallium porphyrins have been previously found only in coal. In this study, petroporphyrins in samples of the Eagle Ford Shale previously studied by French et al. (2020, Marine Petrol. Geol. 118, 104459), were examined using atmospheric pressure photoionization (APPI) FT-ICR-MS. Vanadyl porphyrins (N4VO) dominated the asphaltenes in thermally immature (VRo < 0.56%) samples decreasing in relative abundance with increasing maturity. Only minor amounts of nickel porphyrins were detected in the immature and early oil samples. The distribution of the vanadyl porphyrins is comparable to those reported for marine oils at varying levels of maturity. Immature samples contained porphyrins that were predominantly deoxophylloerythroetio- (DPEP: DBE = 18) and di- deoxophylloerythroetio (di-DPEP: DBE = 19) porphyrins, while ETIO- (DBE = 17), rhodo- (DBE = 20, 21, and 22) and higher condensed (DBE ≥ 23) porphyrins increased with increasing maturity. The vanadyl porphyrins included species with additional one to three oxygen atoms (N4VOx, x= 1 to 4) and one sulfur atom with one to two oxygen atoms (S1N4VOx, x=1 to 3). The degree of additional oxygen and sulfur atoms is consistent with O/C and Sorg/C of associated kerogen. No iron or gallium porphyrins were detected, showing that they are not a ubiquitous feature of the Eagle Ford. We hypothesize that the previously reported iron and gallium porphyrins (Zheng et al., 2018) were present because the specific sample that was analyzed in detail was from the early onset of the Cenomanian–Turonian oceanic anoxic event (OAE-2) in contrast to the samples investigated in this study that are primarily from the lower part of the Eagle Ford pre-dating OAE-2. Submarine volcanism, associated with eruption of large igneous provinces, occurred pre-OAE-2, injecting iron and other inorganic nutrients, giving rise to algal blooms and the acidification of the seawater. At the onset of OAE-2, boreal water masses flowed into the southern Western Interior Seaway, shifting the water column to more oxygenated conditions. Low pH-high Eh (oxic) conditions enhance the availability of iron and gallium such that these events abruptly changed the seawater chemistry, specifically enriching iron and gallium relative to vanadium and nickel. These pH-Eh conditions are similar to the depositional conditions associated with coals, which are known to contain iron and gallium porphyrins, suggesting similar conditions resulted in iron and gallium metalation of porphyrins in the marine setting of the Western Interior Seaway.

Texas↗

USGS1995

K1-95-HW: Cruise report 1995 - Preliminary results, phase III: Sediment chemistry and biological sampling survey

Mamala Bay, off the south shore of the island of Oahu, has been used as a repository of dredged material primarily from Pearl and Honolulu Harbors for over a century. The U.S. Geological Survey, U.S. Army Corps of Engineers, and the U.S. Environmental Protection Agency are conducting an integrated study on the distribution and character of dredged materials as well as the effects of dredged material on the marine environment. A three phase study is providing information to evaluate the effects on seafloor substrate and the benthic fauna. The studies include geophysical profiling and imaging, bottom photography, sampling, chemical and physical analyses of sediment, and evaluations of the benthic population, population density, and adverse impacts to the benthic fauna. Phase 1, conducted in 1993, inventoried the seafloor via remote sensing. Sidescan sonar and subbottom profilers characterized the seafloor in and around the disposal sites, and the resulting products reveal the character and extent of the dredged material. These data were used to plan Phase 2 in 1994, a sampling program that employed subbottom profilers, video and still photography, and seafloor sampling to ground truth the sonar mosaic and identify the seafloor substrates responsible for the various acoustic signatures on the sonar images and subbottom profiles. Box coring provided the samples necessary to distinguish dredged material from native sediment, and for the chemical analyses used to determine contaminant concentrations. Phase 3 studies conducted in June of 1995 consisted of box core sampling for chemical and biological analyses. Specific studies include: infaunal taxonomy and population density, bioassay/bioaccumulation, sediment chemistry, and post-disposal resuspension and transport. The 1995 survey, conducted June 14 through 17, resulted in the collection of 39 box cores from 20 different stations. Multiple box cores were composited at 7 different locations occupied in 1994, to provide the material required for the 7 bioassay and bioaccumulation analyses currently underway (Figure 1). Seventeen of the 20 stations occupied provided the biological samples for the benthic infaunal identification and population density study conducted by Dr. Julie Brock of the University of Hawaii, and the sediment chemistry analyses conducted (and completed) by Quanterra Environmental Laboratories (Figure 1). Seven of the 20 stations occupied in 1995 were occupied in 1994, and provide the data for direct comparison of sediment chemistry at the same sites from two consecutive years. The sum total of the data collected from all three phases of the monitoring program will provide the U.S. Army Corps of Engineers and the U.S. Environmental Protection Agency with the information required to make informed decisions as to the management of the South Oahu disposal site in Mamala Bay.

Hawai'i↗

USGS1977

Occurrence of bloedite and related minerals in marine shale of Diablo and Temblor Ranges, California

Bloedite, epsomite, and related minerals occur in small amounts throughout the arid eastern foothills of the Diablo and Temblor Ranges, as efflorescences on siliceous shale and as deposits around small springs and a brine pond. These minerals ultimately are products of weathering of underlying organic shale, and they are reminders that the chemistry of weathering of reduced organic shale is largely a reversal of the chemistry of its early diagenesis.

California↗