Organic compounds are produced in vast quantities for industrial and agricultural use, as well as for human and animal healthcare [1]. These chemicals and their metabolites are frequently detected at trace levels in fresh water environments where they undergo degradation via different reaction pathways. Compound specific stable isotope analysis (CSIA) is a valuable tool to identify such degrada...

The intramolecular (13)C kinetic isotope effects for the ring-opening of cyclopropylcarbinyl radical were determined over a broad temperature range. The observed isotope effects are unprecedentedly large, ranging from 1.062 at 80 degrees C to 1.163 at -100 degrees C. Semiclassical calculations employing canonical variational transition-state theory drastically underpredict the observed isotope ...

The interpretation of stable isotope values hinges on precise, accurate estimates of kinetic isotope effects ( ), which are equal to k/k, where k and k are the reaction rate constants for the two isotopes. Kinetic isotope effects are commonly determined by monitoring the reactant concentration (C) and isotope ratio (R) relative to their initial values (C1 and R1, respectively). Values of are es...

the lut block (eastern iran) extends over 900 km in a north-south direction and is only 200 km wide in an east-west direction. it is confined by the nayband fault and shotori range on the west. the eastern edge is bordered by the sistan suture zone and nehbandan fault. the northern termination of lut block is the depression of kavir-e-namak and the great kavir fault. the makran arc, including t...

Orotidine-5'-monophosphate decarboxylase (OMP decarboxylase, ODCase) catalyzes the decarboxylation of orotidine-5'-monophosphate (OMP) to uridine-5'-monophosphate (UMP). Despite extensive enzymological, structural, and computational studies, the mechanism of ODCase remains incompletely characterized. Herein, carbon kinetic isotope effects were measured for both the natural abundance substrate a...

Mass-independent sulfur isotope signatures are observed in Archean and early Paleoproterozoic sedimentary sulfate and sulfide minerals, and provide the most robust constraints on early atmospheric oxygen levels. Smaller mass-independent sulfur isotope anomalies are observed in ice cores and interpreted as a tracer of stratospheric volcanic loading. Photochemistry of sulfur dioxide (SO 2) has be...

[1] Longitudinal and diel measurements of dual isotope composition (dN and dO) in nitrate (NO3-N) were made in the Ichetucknee River, a large ( 8 m s ), entirely spring-fed river in North Florida, to determine whether isotopic variation can deconvolve assimilatory and dissimilatory removal. Comparing nitrate concentrations and isotope composition during the day and night we predicted (1) daytim...

Stable isotope analysis has been utilized in archaeology since the 1970s, yet standardized protocols for terminology, sampling, pretreatment evaluation, calibration, quality assurance and control, data presentation, and graphical or statistical treatment still remain lacking in archaeological applications. Here, we present recommendations and requirements for each of these in the archaeological...

Vertebrate fossils and continental sediments provide a rich record of variations in the isotopic composition of surface environments. To interpret these records, a greater understanding of isotopic sources, as well as fractionations associated with animal physiology, soil geochemistry, and diagenesis, has been essential. Tooth enamel and fish otoliths yield subannual records of surface environm...

Multiple sulfur isotope measurements of sulfur compounds associated with dissimilatory sulfate reduction, elemental sulfur disproportionation and sulfite disproportionation indicate that different types of metabolic processes impart different multiple isotope signatures. An established network for sulfate reduction was used previously to explain the multiple isotope variability. Here, we revisi...