Tracking the evolution of particulate organic matter sources during summer storm events via end-member mixing analysis based on spectroscopic proxies.

Despite the growing attention to the effects of hydrological precipitation on organic carbon export along the continuum land-river-ocean, limited effort has been made to understand the export and the reactivity of particulate organic carbon (POC) compared to those of dissolved organic carbon (DOC). Yet, further understanding of the controlling mechanisms on the export of particulate organic matter (POM) from terrestrial systems is fundamental. In this study, we assessed the temporal changes of the source contributions to riverine POM in two adjacent rivers of the same watershed during two summer storm events, which included the early and the late events, using end-member mixing analysis (EMMA) based on spectroscopic proxies.

Do early diagenetic processes affect the applicability of commonly-used organic matter source tracking tools? An assessment through controlled degradation end-member mixing experiments.

In the development of organic matter (OM) source tracking tools, it is critical to validate if (1) the tracers are conservative with source mixing, and (2) they can be conservative under diagenetic processes (e.g., microbial degradation).

Evaluating the contributions of different organic matter sources to urban river water during a storm event via optical indices and molecular composition.

Dissolved organic matter (DOM) in river water dynamically changes with respect to its major sources during heavy rain events. However, there has been no established tool to estimate the relative contributions of different organic sources to river water DOM. In this study, the evolution in the contributions of ten different organic matter (OM) sources to storm water DOM was explored with a selected urban river, the Geumho River in South Korea, during storm events via an end-member mixing analysis (EMMA) based on fluorescence indices and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS).

Biodegradation-induced signatures in sediment pore water dissolved organic matter: Implications from artificial sediments composed of two contrasting sources.

Biodegradation is one of the main processes causing the changes in amount, composition and properties of organic matter in sediment and water-sediment interface. The degradation processes of sediment organic matter lead to a release of dissolved organic matter (DOM) into the pore water via hydrolysis and depolymerization of particulate organic matter (POM). Whereas the pore waters represent a reactive zone in sediment closely linked to biogeochemistry of the substrate, they are still poorly characterized under diagenetic processes.

Characterization of aquatic organic matter: Assessment, perspectives and research priorities.

Organic matter (OM) refers to the largest reactive reservoir of carbon-based compounds on Earth. Aside of its role as a source of carbon, OM is also actively involved in a wide range of ecological functions. It also plays an important role in the solubility, toxicity, bioavailability, mobility and distribution of pollutants.

In-Depth Assessment of the Effect of Sodium Azide on the Optical Properties of Dissolved Organic Matter.

Treatment and preservation of samples are critical issues in measuring the optical properties of dissolved organic matter (DOM) due to their high sensitivity to physical and chemical changes upon sample handling. In this study, we rigorously assessed the potential interferences of sodium azide (NaN) on DOM absorption and fluorescence. A wide range of different samples were poisoned with varying NaN concentrations.

Assessment on applicability of common source tracking tools for particulate organic matter in controlled end member mixing experiments.

In this study, ideal mixing behaviors of the three commonly-used source tracking tools, which include fluorescence spectroscopy, stable isotope ratios, and lipid biomarkers, were evaluated in controlled particular organic matter (POM) mixtures of two contrasting end members e.g., soil and algae.

Faecal biomarkers can distinguish specific mammalian species in modern and past environments.

Identifying the presence of animals based on faecal deposits in modern and ancient environments is of primary importance to archaeologists, ecologists, forensic scientists, and watershed managers, but it has proven difficult to distinguish faecal material to the species level. Until now, four 5β-stanols have been deployed as faecal biomarkers to distinguish between omnivores and herbivores, but they cannot distinguish between species. Here we present a database of faecal signatures from ten omnivore and herbivore species based on eleven 5β-stanol compounds, which enables us to distinguish for the first time the faecal signatures of a wide range of animals.

Optical and molecular characterization of dissolved organic matter (DOM) in the Arctic ice core and the underlying seawater (Cambridge Bay, Canada): Implication for increased autochthonous DOM during ice melting.

Sea ice contains a large amount of dissolved organic matter (DOM), which can be released into the ocean once it melts. In this study, Arctic sea ice DOM was characterized for its optical (fluorescence) properties as well as the molecular sizes and composition via size exclusion chromatography and Fourier transformation ion cyclotron resonance mass spectrometry (FT-ICR MS). Ice cores were collected along with the underlying seawater samples in Cambridge Bay, an Arctic area experiencing seasonal ice formation.

Estimation of different source contributions to sediment organic matter in an agricultural-forested watershed using end member mixing analyses based on stable isotope ratios and fluorescence spectroscopy.

The two popular source tracing tools of stable isotope ratios (δC and δN) and fluorescence spectroscopy were used to estimate the relative source contributions to sediment organic matter (SeOM) at five different river sites in an agricultural-forested watershed (Soyang Lake watershed), and their capabilities for the source assignment were compared. Bulk sediments were used for the stable isotopes, while alkaline extractable organic matter (AEOM) from sediments was used to obtain fluorescent indices for SeOM. Several source discrimination indices were fully compiled for a range of the SeOM sources distributed in the catchments of the watershed, which included soils, forest leaves, crop (C3 and C4) and riparian plants, periphyton, and organic fertilizers.

Comparing discrimination capabilities of fluorescence spectroscopy versus FT-ICR-MS for sources and hydrophobicity of sediment organic matter.

Characterizing the chemical and molecular composition of sediment organic matter (SeOM) provides critical information for a complete picture of global carbon and nutrient cycles, and helps to track the sources and the fate of organic carbon in aquatic environments. In this study, we examined fluorescence properties and the molecular composition of the alkaline-extractable organic matter (AEOM) of sediments in a coastal lake (Lake Sihwa) and its surrounding creeks (rural, urban, wetland, and industrial areas). Five fluorescence-based indices and 20 molecular parameters were selected from fluorescence spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), respectively, and utilized to discriminate the AEOM among five different sources as well as the chemical composition of hydrophobic acid (HoA) and hydrophilic (Hi) fractions.

Spectroscopic and molecular characterization of humic substances (HS) from soils and sediments in a watershed: comparative study of HS chemical fractions and the origins.

Optical properties and molecular composition of humic substances (HS) can provide valuable information on the sources and the history of the associated biogeochemical processes. In this study, many well-known spectral and molecular characteristics were examined in eight different HS samples, which were extracted from soils and sediments located in a forested watershed, via two advanced tools including fluorescence excitation emission matrix-parallel factor analysis (EEM-PARAFAC) and high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Two humic-like (C1 and C2) and one protein-like (C3) components were identified from EEM-PARAFAC.

Lipid biomarkers and spectroscopic indices for identifying organic matter sources in aquatic environments: A review.

Understanding the dynamics of organic matter (OM) and the roles in global and local carbon cycles is challenging to the fields of environmental sciences and biogeochemistry. The accurate identification of OM is an essential element to achieve this goal. Lipids, due to their ubiquitous presence and diagenetic and chemical stability, have long and successfully been used as molecular makers in assessing the sources and the fate of OM in natural environments.

Sources and distribution of organic matter along the Ring of Cenotes, Yucatan, Mexico: sterol markers and statistical approaches.

The Yucatan Peninsula is a large low lying platform of limestone, dolomite and evaporite deposits, forming an extensive and mature karst aquifer with many sinkholes locally called cenotes. In Yucatan, the only source of drinking water is groundwater and its quality could be impaired by: (i) infiltration of contaminants and (ii) saltwater intrusion. To investigate the sources of organic matter in this aquifer, sediment samples (46) were collected from cenotes and analysed using gas chromatography-mass spectrometry.

Mixing and reaction kinetics in porous media: an experimental pore scale quantification.

We propose a new experimental set up to characterize mixing and reactive transport in porous media with a high spatial resolution at the pore scale. The analogous porous medium consists of a Hele-Shaw cell containing a single layer of cylindrical solid grains built by soft lithography. On the one hand, the measurement of the local, intrapore, conservative concentration field is done using a fluorescent tracer.

Extreme variability of steroid profiles in cow feces and pig slurries at the regional scale: implications for the use of steroids to specify fecal pollution sources in waters.

Thirty-five samples of cow feces (cowpat and cow manure) and pig slurries subjected to different treatment processes and different storage times before land spreading were extracted and analyzed by gas chromatography-mass spectrometry to determine their fecal stanol profiles. The fresh pig slurry data presented here increase considerably the classical range of values obtained for steroid ratios, resulting in an overlap with the range for cow feces. These results lead to the inability to distinguish species source of feces on the basis of steroid ratios alone.

Microbial and chemical markers: runoff transfer in animal manure-amended soils.

Fecal contamination of water resources is evaluated by the enumeration of the fecal coliforms and Enterococci. However, the enumeration of these indicators does not allow us to differentiate between the sources of fecal contamination. Therefore, it is important to use alternative indicators of fecal contamination to identify livestock contamination in surface waters.