Filtering by Subject: Biogeochemistry
Published: 2019-03-12
Subjects: Biogeochemistry, Earth Sciences, Hydrology, Physical Sciences and Mathematics, Speleology
Speleothem δ18O values are commonly used to infer past climate variability. However, both non-linear karst hydrological processes and in-cave disequilibrium isotope fractionation are recognised and hinder the interpretation of δ18O values. In recent years, proxy system models (PSMs) have emerged to quantitatively assess the confounding effects of these processes. This study presents the first [...]
Published: 2019-02-22
Subjects: Biogeochemistry, Earth Sciences, Environmental Sciences, Other Earth Sciences, Physical Sciences and Mathematics
Fire regime shifts are driven by climate and natural vegetation changes, but can be strongly affected by human land management. Yet, it is poorly known how exactly humans have influenced fire regimes prior to active wildfire suppression. Among the last 250 years, the human contribution to the global increase in fire occurrence during the mid-19th century is especially unclear, as data sources are [...]
Published: 2019-02-21
Subjects: Biogeochemistry, Earth Sciences, Environmental Sciences, Physical Sciences and Mathematics
Differentiating biotic and abiotic processes in nature remains a persistent challenge, specifically in evaluating microbial contributions to geochemical processes through time. Building on previous work reporting that biologically-influenced systems exhibit stronger long-range correlation than abiotic systems, this study evaluated the relationship between long-range correlation of redox [...]
Published: 2019-01-16
Subjects: Biogeochemistry, Earth Sciences, Physical Sciences and Mathematics
The chemistry of the Early Earth is widely inferred from the elemental and isotopic compositions of sulfidic sedimentary rocks, which are presumed to have formed globally through the reduction of seawater sulfate or locally from hydrothermally supplied sulfide. Here we argue that, in the sulfate-poor ferruginous oceans of the Archean eon, organic sulfur must have played an important and [...]
Published: 2018-12-03
Subjects: Agriculture, Biogeochemistry, Earth Sciences, Environmental Microbiology and Microbial Ecology Life Sciences, Environmental Sciences, Life Sciences, Microbiology, Natural Resources Management and Policy, Physical Sciences and Mathematics, Soil Science, Water Resource Management
Despite ongoing management efforts, phosphorus (P) loading from agricultural landscapes continues to impair water quality. Wastewater treatment plant research has enhanced our knowledge of microbial mechanisms influencing P cycling, especially related to microbes known as polyphosphate accumulating organisms (PAOs) that store P as polyphosphate (polyP) under aerobic conditions and release P under [...]
Published: 2018-10-08
Subjects: Biogeochemistry, Earth Sciences, Geomorphology, Physical Sciences and Mathematics
Organic carbon (OC) in valley bottom downed wood and soil that cycles over short to moderate timescales represents a large, dynamic, and poorly quantified pool of carbon whose distribution and residence time affects global climate. We compare four disparate mountain river basins to show that mountain river valley bottoms store substantial estimated OC stocks in floodplain soil and downed wood. [...]
Published: 2018-09-23
Subjects: Biogeochemistry, Earth Sciences, Geomorphology, Physical Sciences and Mathematics, Sedimentology, Stratigraphy
Technological advances make these exciting times for geoscientists studying Earth surface processes, their depositional products, and interactions with the biosphere, hydrosphere, atmosphere, and lithosphere; from monitoring contemporary sediment transport processes to interpretation of sedimentary archives that record ancient environmental changes. We set out three research challenges: 1) [...]
Published: 2018-06-21
Subjects: Biogeochemistry, Earth Sciences, Environmental Indicators and Impact Assessment, Environmental Monitoring, Environmental Sciences, Life Sciences, Physical Sciences and Mathematics, Systems Biology, Water Resource Management
Addition of nutrients, such as nitrogen, can degrade water quality in lakes, rivers, and estuaries. To predict the fate of nutrient inputs, an understanding of the biogeochemical cycling of nutrients is needed. We develop and employ a novel, parsimonious, process-based model of nitrogen concentrations and stable isotopes that quantifies the competing processes of volatilization, uptake, [...]
Published: 2018-05-24
Subjects: Biogeochemistry, Earth Sciences, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics
Subsurface chlorophyll maximum layers (SCMLs) are nearly ubiquitous in stratified water columns and exist at horizontal scales ranging from the submesoscale to the extent of oligotrophic gyres. These layers of heightened chlorophyll and/or phytoplankton concentrations are generally thought to be a consequence of a balance between light energy from above and a limiting nutrient flux from below, [...]
Published: 2018-05-22
Subjects: Biogeochemistry, Earth Sciences, Environmental Indicators and Impact Assessment, Environmental Sciences, Physical Sciences and Mathematics, Water Resource Management
Modern anthropogenic activities have significantly increased nitrate (NO3-) concentrations in surface waters. Stable isotopes (δ15N and δ18O) in NO3- offer a tool to deconvolute some of the human-made changes in the nitrogen cycle. They are often graphically illustrated on a template designed to identify different sources of NO3- and denitrification. In the two decades since this template was [...]
Published: 2018-05-16
Subjects: Biogeochemistry, Earth Sciences, Environmental Sciences, Geochemistry, Physical Sciences and Mathematics
Geophysical surveys add value to biogeochemical studies because of their ability to characterize systems remotely, and their precise time resolution. One limitation, however, is their lack of biogeochemical process specificity. Here, electrochemical time series from an oxic-anoxic cyclical bioreactor experiment were reanalyzed with detrended fluctuation analysis (DFA) to distinguish dominant [...]
Published: 2018-05-03
Subjects: Biogeochemistry, Earth Sciences, Physical Sciences and Mathematics
The amount of nitrogen in the atmosphere, oceans, crust, and mantle have important ramifications for Earth’s biologic and geologic history. Despite this importance, the history and cycling of nitrogen in the Earth system is poorly constrained over time. For example, various models and proxies contrastingly support atmospheric mass stasis, net outgassing, or net ingassing over time. In addition, [...]
Published: 2018-02-26
Subjects: Biogeochemistry, Biology, Chemistry, Earth Sciences, Environmental Chemistry, Environmental Indicators and Impact Assessment, Environmental Sciences, Geology, Life Sciences, Paleobiology, Paleontology, Physical Sciences and Mathematics, Sedimentology
The discovery of a Permian-Triassic boundary section in northeastern Utah reveals a detailed record of events that led to one of the greatest mass extinctions on the planet. From 83% to 97% of the species living on the planet went extinct during this relatively short interval of geological time, which defines the major geological boundary between the Paleozoic and Mesozoic Eras. The cause and [...]
Published: 2018-02-04
Subjects: Biogeochemistry, Chemistry, Earth Sciences, Environmental Sciences, Geochemistry, Other Physical Sciences and Mathematics, Physical Sciences and Mathematics
Hopanoids are pentacyclic triterpenoids produced by a wide range of bacteria. Within modern settings, hopanoids mostly occur in the biological 17β,21β(H) configuration. However, in some modern peatlands, the C31 hopane is present as the thermally-mature 17α,21β(H) stereoisomer. This has traditionally been ascribed to isomerisation at the C-17 position catalysed by the acidic environment. However, [...]
Published: 2018-01-27
Subjects: Biogeochemistry, Earth Sciences, Geology, Paleobiology, Physical Sciences and Mathematics, Sedimentology, Stratigraphy
Characterizing the lithology, age, and physical-chemical properties of rocks and sediments in the Earths upper crust is necessary to fully assess energy, water, and mineral resources and to address many fundamental questions in the Earth sciences. Although a large number of geological maps, regional geological syntheses, and sample-based measurements have been produced, there is no openly [...]