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This study aimed to improve the traceability of rice-producing areas to address the increasing demand for accurate methods to confirm food quality and safety. Compound-specific δ 13 C of fatty acids, δ 13 C of starch and bulk of rice were measured. PCA, PLS-DA and VIP value analysis of the obtained data were performed to track the source of rice from the six regions. The PLS-DA model established with bulk δ 13 C, starch δ 13 C, and fatty acid δ 13 C, which clearly separated the rice from six regions. The VIP graph showed the value of starch, C18:0 and C18:2 δ 13 C values (VIP > 1) were important to distinguish the origin of rice. Also, according to loading plots the contribution of starch δ 13 C was the largest. The findings indicate that the introduction of starch δ 13 C improves the precision of rice traceability and provides an effective method for identifying rice origin., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Liu Yu has patent pending to Dalian Maritime University., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

As one of the typical brominated flame retardants, decabromodiphenyl ether (BDE-209) has been widely detected in environment. However, scarce information was available on BDE-209 phototransformation mechanisms in various media. In this study, compound-specific stable isotope analysis was first applied to investigate BDE-209 phototransformation in n-hexane, MeOH:H2O (v:v, 8:2), and simulated seawater by simulated sunlight. BDE-209 transformation followed pseudo-first-order kinetic, with degradation rate in the following of n-hexane (2.66 × 10–3 min−1) > simulated seawater (1.83 × 10–3 min−1) > MeOH:H2O (1.41 × 10–3 min−1). Pronounced carbon isotope fractionation was first observed for BDE-209 phototransformation, with carbon isotope enrichment factors (εC) of -1.01 ± 0.14‰, -1.77 ± 0.26‰, -2.94 ± 0.38‰ in n-hexane, MeOH:H2O and simulated seawater, respectively. Combination analysis of products and stable carbon isotope, debromination with cleavage of C–Br bonds as rate-limiting step was the main mechanism for BDE-209 phototransformation in n-hexane, debromination and hydroxylation with cleavage of C–Br bonds as rate-limiting steps in MeOH:H2O, and debromination, hydroxylation and chlorination in simulated seawater. This present study confirmed that stable carbon isotope analysis was a robust method to discovery the underlying phototransformation mechanisms of BDE-209 in various solutions. [ABSTRACT FROM AUTHOR]

Organophosphate esters (OPEs) are widespread in the environment, with high persistence and toxicity. However, the underlying mechanisms of anaerobic microbial degradation of OPEs remain elusive in the field environment. In this study, the natural attenuation mechanisms of tributyl phosphate (TnBP) by indigenous anaerobic microorganisms in soils were investigated by using compound-specific stable isotope analysis (CSIA) and characterization of microbial communities. The results indicated that dibutyl phosphate (DnBP) was the major degradation product of TnBP. Significant carbon isotope fractionation was observed for TnBP during the anaerobic microbial degradation, and the carbon isotope enrichment factor (ε C) was determined to be −2.71 ± 0.13‰. Unlike aerobic degradation with P-O bond cleavage, C-O bond cleavage was verified as the mode to removal a butyl side chain for TnBP to generate DnBP during the anaerobic microbial degradation. Microbial community analysis indicated that Sphingomonans , Nocardioides and Streptomyces were the important contributors to microbial degradation of TnBP in anoxic soils. TnBP altered microbial metabolic functions in anoxic soils, mainly enhancing the biosynthesis of ansamycins, ketone bodies and amino acids, and flagellar assembly, which promoted microbial degradation of TnBP. This study provided a better method to characterize the chemical bond cleavage mode and effect of OPEs on microbial communities, which was a prerequisite for the bioremediation of OPE pollution in soils. [Display omitted] • Natural attenuation of TnBP by indigenous microbes were disclosed in anoxic soils. • Anaerobic microbial degradation led to stable carbon isotope fractionation of TnBP. • Removal of a butyl side chain to generate DnBP was degradation pathway of TnBP. • Cleavage of C-O rather than P-O was key mode to removal a butyl side chain for TnBP. • Sphingomonas and Nocardioides played key roles on microbial degradation of TnBP. [ABSTRACT FROM AUTHOR]

With the increasing industrialization and urbanization, the ecological environment is suffering from severe deterioration in Liaohe coastal wetland, and petroleum spill is one of the pollution sources. Suaeda salsa (L.) Pall (S. salsa), one of the predominant plants in Liaohe coastal wetland, is facing the increasing degradation. Terpenes are a class of inherent compounds in plants, and play key role in maintain the growth of plants. However, the environmental stress on the terpene metabolism remained unclear in the plants. In the present study, the influence of petroleum spill on terpene metabolism in S. salsa was systematically investigated by analysis of concentrations, compositions and stable carbon isotope. Under the stress of petroleum spill, terpene concentrations showed the decreasing trend, indicating the inhibition effect of petroleum spill on terpene synthesis in S. salsa. The proportions of Sabinene and A-humulene showed the obviously increased with the influence of petroleum spill, implying that these congeners were more sensitive to petroleum spills. The significant changes in stable carbon isotope compositions were observed for Borneol, Dl-menthol, A-humulene and (-) -@-bisabolol, with the enrichment in heavier isotopes in residual fractions. This result indicated that the heavier 13C was preferentially fixed on terpene by S. salsa under the petroleum stress. The similar change trends along the incubation time was observed for A-humulene and (-) - trans caryophyllene, which might imply that A-humulene was one of the products of (-) - trans caryophyllene in S. salsa. Overall, the findings of present study verified the influence of petroleum spill on terpene metabolism in S. salsa , and were meaningful for protecting the plants in the petroleum-pollution wetlands. [Display omitted] • Terpene contents in S. salsa decreased with increasing petroleum dose. • Proportions of monoterpenes increased under influence of petroleum spill. • Stable carbon isotope analysis confirmed effect of petroleum on terpene metabolism. • A-humulene was evidenced to be one product of (-) - trans caryophyllene in S. salsa. [ABSTRACT FROM AUTHOR]

As a novel brominate flame retardants, 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) has been extensively used in various consumer products, and frequently detected in various environmental matrices. However, the microbial degradation of BTBPE remains unclear in the environment. This study comprehensively investigated the anaerobic microbial degradation of BTBPE and therein stable carbon isotope effect in the wetland soils. BTBPE degradation followed the pseudo-first-order kinetic, with degradation rate of 0.0085 ± 0.0008 day−1. Based on identification of degradation products, stepwise reductive debromination was the main transformation pathway of BTBPE, and tended to keep the stable of 2,4,6-tribromophenoxy group during the microbial degradation. The pronounced carbon isotope fractionation was observed for BTBPE microbial degradation, and carbon isotope enrichment factor (ε C) was determined to be −4.81 ± 0.37‰, indicating cleavage of C–Br bond as the rate-limiting step. Compared to previously reported isotope effects, carbon apparent kinetic isotope effect (AKIE C = 1.072 ± 0.004) suggested that the nucleophilic substitution (S N 2 reaction) was the potential reaction mechanism for reductive debromination of BTBPE in the anaerobic microbial degradation. These findings demonstrated that BTBPE could be degraded by the anaerobic microbes in wetland soils, and the compound-specific stable isotope analysis was a robust method to discover the underlying reaction mechanisms. • Anaerobic microbial degradation of BTBPE was first verified in wetland soils. • Three debromination products were identified for BTBPE microbial degradation. • Significant carbon isotope fractionation was discovered during BTBPE degradation. • Cleavage of C–Br bond was rate-limiting step for BTBPE reductive debromination. • Nucleophilic aromatic substitution was debromination mechanism of BTBPE degradation. [ABSTRACT FROM AUTHOR]

Polybrominated diphenyl ethers (PBDEs) are widespread contaminants in the environment. Microbial reductive debromination is one of the important attenuation processes for PBDEs in the anaerobic sediments. This study first investigated the interaction between BDE-47 and BDE-153 during the microbial degradation in wetland sediments by the multiple-line approaches including biodegradation kinetics, microbial community structures and stable isotope composition. BDE-47 and BDE-153 biodegradation fitted pseudo-zero-order kinetics, with the higher degradation rates in single than combined exposure, indicating the mutual inhibition in co-exposure condition. BDE-47 and BDE-153 shared the common dehalogenators (genus Dehalococcoides and Acinetobacter) with enrichment in combined exposure, indicating the potential competition in dehalogenating bacteria during biodegradation. Microbial degradation could lead to the isotopic fractionation of BDE-47 and BDE-153, with the smaller changes in δ 13C in combined than single exposure. The apparent kinetic isotope effect of carbon (AKIE C) was different between BDE-47 and BDE-153 in single exposure, whilst identical in combined exposure, indicating the similar degradation mechanism for BDE-47 and BDE-153 in co-exposure condition. These results revealed that the competition on microbial degradation occurred among PBDEs in co-exposure condition, which was important for the comprehensive risk assessment of simultaneous exposure to multiple PBDE congeners in the environment. [Display omitted] • Competitive microbial degradation among PBDEs was first studied in anaerobic sediment. • Degradation rate of BDE-47 and 153 was higher in single than combined exposure. • Dehalococcoides and Acinetobacter were the common dehalogenators for BDE-47 and 153. • Stable carbon isotope fractionation occurred during BDE-47 and 153 biodegradation. • Changes in δ 13C of BDE-47 and 153 were larger in single than combined exposure. [ABSTRACT FROM AUTHOR]

Microbial degradation is an important pathway for the attenuation of polybrominated diphenyl ethers (PBDEs) in natural soils. In this study, the compound-specific stable isotope analysis (CSIA) was applied to characterize microbial degradation of BDE-153, one of the prevailing and toxic PBDE congeners, in natural wetland soils. During the 45-day incubation, the residual percentages of BDE-153 decreased to 67.9% and 73.6% in non-sterilized soils spiked with 1.0 and 5.0 μ g/g, respectively, which were both much lower than those in sterilized soils (96.0% and 97.2%). This result indicated that microbial degradation could accelerate BDE-153 elimination in wetland soils. Meanwhile, the significant carbon isotope fractionation was observed in non-sterilized soils, with δ 13C of BDE-153 shifting from −29.4‰ to −26.7‰ for 1.0 μ g/g and to −27.2‰ for 5.0 μ g/g, respectively, whilst not in sterilized soils. This phenomenon indicated microbial degradation could induce stable carbon isotope fractionation of BDE-153. The carbon isotope enrichment factor (ε c) for BDE-153 microbial degradation was first determined as −7.58‰, which could be used to assess the microbial degradation and bioavailability of BDE-153 in wetland soils. Based on δ 13C and ε c , the new methods were developed to dynamically and quantitatively estimate degradation degree and bioavailability of BDE-153 during degradation process, respectively, which could exclude interference of physical processes. This work revealed that CSIA was a promising method to investigate in situ microbial degradation of PBDEs in field studies. Image 1 • Microbial degradation of BDE-153 followed first-order kinetic model in soils. • Microbial degradation induced stable carbon isotope fractionation of BDE-153. • Carbon isotope enrichment factor of BDE-153 was −7.58‰. • CSIA was used to dynamically and quantitatively estimate BD and BA of BDE-153. [ABSTRACT FROM AUTHOR]

The eutrophication of water, such as excessive nitrogen and phosphorus, are closely associated with the outbreak of red tide. However, the response of dissolved inorganic phosphorus (DIP) to red tide remained unclear in water. In this study, three species of diatoms capable of causing red tides were cultured in simulated seawater with different concentrations of DIP. The changes of biomass, chlorophyll a concentration and the carbon stable isotope composition of microalgae, the DIP concentration and pH of the culture medium were compared among the experimental groups. In addition, correlation verification was used to test the correlation between the change of DIP concentration and other indicators. The results showed that in the experimental period, the DIP concentration of each experimental group decreased significantly first, and the concentration dropped to less than 40% of the initial level. After that, the pH of the medium, the biomass, chlorophyll a concentration and carbon stable isotope composition of the microalgae showed varying degrees of increase, and then stabilized or decreased. These also marked the outbreak of red tide. Moreover, the correlation test showed that there was a correlation between them and the change of DIP concentration. Therefore, by exploring the relationship between the change of DIP concentration in water and the occurrence of red tide, this study provides a possible direction for the current prediction of red tide, and provides a basis for further investigation of the occurrence mechanism of red tide. [Display omitted] • Outbreak of red tide of different algae species under different eutrophic levels. • The decrease of DIP concentration was earlier than the increase of other indicators of red tide algae. • The outbreak of red tide resulted in the accumulation of 13C in red tide algae. [ABSTRACT FROM AUTHOR]