Guangzhou Institute of Geochemistry
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Dual-carbon isotope analysis of benzene polycarboxylic acids for tracking black carbon across different environments
No full textBlack carbon (BC) is ubiquitous in the environment and is a significant component of the refractory carbon pool. However, its sources, biogeochemical processes, and environmental residence times are poorly understood. One important reason is that the technical protocols for isolating/analyzing BC vary across different matrices, thereby bringing inconsistency among studies on BC in different environment media. Benzene polycarboxylic acids (BPCA), produced by nitric acid oxidation of the condensed aromatic structure that is common in BC and BC-like substances, has been proven to be a useful molecular proxy for tracking BC in the Earth's surface. Here, we introduce a new technical approach for the compound-specific dual-carbon isotope (813C and A14C) analysis of BPCA. The BPCA compounds are isolated using preparative liquid chromatography, in which trifluoroacetic acid is used in the mobile phase instead of phosphoric acid. This allows complete removal of solvent from the isolated BPCA fraction, so that conversion of BPCA isolates into CO2 can be done by conventional oxidation methods for off-line Delta 14C analysis with accelerator mass spectrometry. Liquid chromatography (void column)-stable carbon isotope ratio mass spectrometry is employed to measure 813C of the isolated BPCA, leaving as much BPCA carbon amount as possible for 14C analysis. Blockage of oxidation chamber due to incomplete oxidation of other organic acids in the samples is avoided thanks to preliminary isolation of BPCA. We tested the approach by applying it to solid and dissolved BC species in a suite of environmental reference materials, including maize char, coal, riverine natural organic matter (NOM 2R101N), marine sediment (SRM 1941b), urban dust (SRM 1649b), and coke-polluted soils. We assessed the offsets of BPCA-813C and BPCA-A14C values caused by procedural carbon contaminations to correct measured carbon isotopic values. Paired 813C-A14C data of individual BPCA were plotted to validate and demonstrate the ability of this dual carbon isotope technique in tracking BC across different environmental matrices. We observed slightly different 813C-A14C signatures among individual BPCA, indicating that the less condensed BC may have younger apparent radiocarbon ages
Informal E-waste recycling in nine cities of Pakistan reveals significant impacts on local air and soil quality and associated health risks
No full textThe global increase in electronic waste (e-waste) has led to a rise in informal recycling, emitting hazardous heavy metals (HMs) that threaten human health and ecosystems. This study presents the first comprehensive assessment of HM levels in dry deposition and soils at proximity of forty (40) informal e-waste recycling sites across Pakistan, between September 2020 to December 2021. Findings reveal that Zn (1410), Pb (410) and Mn (231) exhibited the higher mean deposition fluxes (mu g/m2.day), derived from air samples, particularly in Karachi. Similarly, soils showed higher mean concentrations (mu g/g dw) of Mn (477), Cu (514) and Pb (172) in Faisalabad, Lahore, and Karachi, respectively. HMs concentrations were found higher in winter or autumn and lower in summer. In addition, HM levels were significantly (p = 0.05) higher at recycling sites compared to background sites year-round, highlighting the e-waste recycling operations as the major source of their emissions. The Igeo index indicated moderate to extremely contaminated levels of Cu, Pb, Cd, and Ni in Karachi, Lahore and Gujranwala. Ingestion was found as a leading human exposure route, followed by dermal and inhalation exposure, with Pb posing the greatest health risk. The Cumulative Incremental Lifetime Cancer Risk (ILCR) model suggested moderate to low cancer risks for workers. Strategic interventions recommend mitigating health and environmental risks, prioritizing human health and ecosystem integrity in Pakistan's e-waste management
A mechanism of stratospheric O<sub>3 </sub> intrusion into the atmospheric environment: a case study of the North China Plain
No full textStratosphere-to-troposphere transport results in the stratospheric intrusion (SI) of O-3 into the free troposphere through the folding of the tropopause. However, the mechanism of SI that influences the atmospheric environment through the cross-layer transport of O-3 from the stratosphere and free troposphere to the atmospheric boundary layer has not been elucidated thoroughly. In this study, an SI event over the North China Plain (NCP; 33-40 degrees N, 114-121 degrees E) during 19-20 May 2019 was chosen to investigate the mechanism of the cross-layer transport of stratospheric O-3 and its impact on the near-surface O-3 based on multi-source reanalysis, observation data, and air quality modeling. The results revealed a mechanism of stratospheric O-3 intrusion into the atmospheric environment induced by an extratropical cyclone system. The SI with downward transport of stratospheric O-3 to the near-surface layer was driven by the extratropical cyclone system, with vertical coupling of the upper westerly trough, the middle of the northeast cold vortex (NECV), and the lower extratropical cyclone, in the troposphere. The deep trough in the westerly jet aroused the tropopause folding, and the lower-stratospheric O-3 penetrated the folded tropopause into the upper and middle troposphere; the westerly trough was cut off to form a typical cold vortex in the upper and middle troposphere. The compensating downdrafts of the NECV further pushed the downward transport of stratospheric O-3 in the free troposphere; the NECV activated an extratropical cyclone in the lower troposphere; and the vertical cyclonic circulation governed the stratospheric O-3 from the free troposphere across the boundary layer top, invading the near-surface atmosphere. In this SI event, the average contribution of stratospheric O-3 to near-surface O-3 was accounted for at 26.77 %. The proposed meteorological mechanism of the vertical transport of stratospheric O-3 into the near-surface atmosphere, driven by an extratropical cyclone system, could improve the understanding of the influence of stratospheric O-3 on the atmospheric environment, with implications for the coordinated control of atmospheric pollution
Study on the swelling of macromolecular geological organic matter with hydrocarbons and heteroatomic compounds
No full textIn this study, we conducted swelling experiments on eleven macromolecular geological organic materials using five types of organic solvents. Our primary objective was to investigate the absorption capacity of different solid organic materials in organic fluids and analyze the influence of their chemical structures. The samples utilized in this research included solid bitumen, kerogen, and coal samples from various basins. The chemical structure of the samples was assessed using solid-state 13C nuclear magnetic resonance (NMR), while X-ray diffraction (XRD) was employed to monitor any detect the structural changes during the swelling process. Our findings reveal that macromolecular geological organic compounds demonstrate a preferential expulsion of saturated hydrocarbons, followed by polycyclic aromatic hydrocarbons, upon interaction with liquid organic matter. The sulfurcontaining compounds in solid organic matter demonstrated higher solubility than hydrocarbon compounds, while the solubility of oxygen-containing compounds varied based on the structure of the aliphatic chain and the proportion of oxygen atoms. This research, introduces LA [= Lac x Aac] as a new parameter to assess the combination of aliphatic chain length [Lac] and [Aac] abundance in solid organic matter. Furthermore, XRD testing revealed that the chemical structure unit of heteroatom compounds in solid organic matter consists of amorphous carbon, primarily composed of aliphatic chains. In this study, we evaluated the retention capacity of various macromolecular geological organic matter for both hydrocarbons and heteroatomic compounds. Additionally, the extent of swelling was investigated, providing theoretical support to diverse fields including organic petrology, petroleum geology, coal geology, and organic geochemistry
Multiple mineralization events in the Central Borneo metallogenic belt, Indonesia: Insights from the Beruang Kanan orefield
No full textThe Beruang Kanan is an important polymetallic orefield in Indonesia and is the first reported example of coexisting Cretaceous and Miocene mineralization on the island of Borneo. This study presents new U-Pb-Hf isotope and pyrite chemistry data to characterize the tectono-magmatic events tied to the ore formation at Beruang Kanan, and to establish the geochronological framework for gold and base metal mineralization across the Central Borneo region. Base metal mineralization (ca. 102-105 Ma) was closely linked to the emplacement of Sepauk tonalite (ca. 120-108 Ma) and its associated volcanism. Gold mineralization (ca. 13.09-9.18 Ma) was associated with the emplacement of Sintang intrusion (ca. 13.94-9.33 Ma). Pyrite grains from the Cretaceous Menunuk volcanics has lower gold content than those from the Miocene Malasan volcanics, reflecting the multiphase nature of the mineralization at Beruang Kanan. The Cretaceous and Miocene magmatism may have mainly formed the base-metal and gold-silver mineralization, respectively. Central Bornean ore deposits from both metallogenic epochs are attributed to calc-alkaline subduction-related magmatism. The metallogenic potential of intra-plate volcanic rocks and granitoids formed in the Jurassic and Plio-Pleistocene period has yet to be explored
Removal and recovery of phosphorus by a long-term stabilized amorphous calcium carbonate
No full textPhosphorus is a non-renewable resource that guarantees food production, while excessive phosphorus discharge leads to water eutrophication. Phosphorus removal/recovery could help improve water quality and ensure food security. In this contribution, silica-stabilized amorphous calcium carbonates (Si-ACC) were prepared and used to remove/recover phosphate in sludge and domestic sewage. The mechanisms were investigated via kinetic and isothermal adsorption studies and XRD, TEM, Raman, and FT-IR characterization. The results showed that the homogeneously distributed silica successfully inhibited ACC transformation and helped Si-ACC keep the amorphous feature within 680 d. During phosphorus adsorption, Si-ACC quickly transformed into calcite within 5 min and reacted with phosphorus to generate polycrystalline hydroxylapatite within 60 min. The recovered product possessed a maximum specific surface area (SSA) of 209 m2/g and available phosphorus content of 18.0 %, suggesting that Si-ACC was a promising phosphorus recovery material and the recovered product could be a potential phosphate fertilizer
Using rice straw-augmented ecological floating beds to enhance nitrogen removal in carbon-limited wastewater
No full textAgricultural biomass used as solid carbon substrates in ecological floating beds (EFBs) has been proven to be applicable in nitrogen removal for carbon-limited wastewater treatment. However, the subtle interactions among plants, rhizosphere microorganisms, and supplementary carbon sources have not been thoroughly studied. This study combined rice straw mats with different aquatic macrophytes in EFBs to investigate denitrification efficiency in carbon-limited eutrophic waters. Results showed that rice straw significantly enhanced the nitrogen removal efficiency of EFBs, while enriching nitrogen-fixing and denitrifying bacteria (such as Rhizobium, Rubrivivax, and Rhodobacter, etc.). Additionally, during the denitrification process in EFBs, rice straw can release humic acid-like fraction as electron donors to support the metabolic activities of microorganisms, while aquatic macrophytes provide a more diverse range of dissolved organic matters, facilitating a sustainable denitrification process. These findings help to understand the synergistic effect of denitrification processes within wetland ecosystems using agricultural biomass
Optimizing In-Situ Measurement of Representative BVOC Emission Factors Considering Intraspecific Variability
No full textAccurately measuring emission factors (Es) of biogenic volatile organic compounds (BVOCs) with consideration of intraspecific variability is vital but often overlooked. This study presents in-situ measurements of BVOC emissions from 114 Eucalyptus urophylla individuals using the LI-6800 portable photosynthesis system. We observed intraspecific variability exceeding an order of magnitude in BVOC Es. Despite this variability, our approach yielded statistically representative Es for E. urophylla, yet challenging the feasibility of extensive field measurements. By quickly screening net photosynthesis rate (Pn) across a broad set of individuals and selecting those within a specific Pn range, such as mean +/- 0.1 x SD (standard deviation) of Pn for all screened individuals, for detailed BVOC emission measurements, we achieved comparable mean Es with approximately 10% of the original sampling effort. This offers a practical solution for efficient and accurate field measurement of representative BVOC Es, significantly reducing required sample size while effectively addressing intraspecific variability.
Quantifying the emission of volatile organic compounds, such as isoprene, by trees is important yet poses significant challenges, particularly due to the variability observed within a single species. In our study, we used a portable devise to measure these emissions from 114 Eucalyptus urophylla trees within the same plantation, uncovering variances that spanned more than tenfold. Given the impracticality of measuring such a large number of trees to obtain statistically representative emissions data that accounts for intraspecific variability, we proposed a simpler way to get accurate measurements by strategically selecting a smaller subset of trees. This method drastically cuts down the effort and time needed for such studies, making it easier to gather reliable data in natural environments.
Biogenic volatile organic compound (BVOC) emission factors (Es) for 114 Eucalyptus urophylla individuals were measured in situ Intraspecific variation in Es of BVOC exceeded an order of magnitude, with average Es statistically representative A novel method was introduced for fast, accurate and efficient measurement of representative Es of BVOC with reduced sample siz
Optimizing In-Situ Measurement of Representative BVOC Emission Factors Considering Intraspecific Variability
No full textAccurately measuring emission factors (Es) of biogenic volatile organic compounds (BVOCs) with consideration of intraspecific variability is vital but often overlooked. This study presents in-situ measurements of BVOC emissions from 114 Eucalyptus urophylla individuals using the LI-6800 portable photosynthesis system. We observed intraspecific variability exceeding an order of magnitude in BVOC Es. Despite this variability, our approach yielded statistically representative Es for E. urophylla, yet challenging the feasibility of extensive field measurements. By quickly screening net photosynthesis rate (Pn) across a broad set of individuals and selecting those within a specific Pn range, such as mean +/- 0.1 x SD (standard deviation) of Pn for all screened individuals, for detailed BVOC emission measurements, we achieved comparable mean Es with approximately 10% of the original sampling effort. This offers a practical solution for efficient and accurate field measurement of representative BVOC Es, significantly reducing required sample size while effectively addressing intraspecific variability.
Quantifying the emission of volatile organic compounds, such as isoprene, by trees is important yet poses significant challenges, particularly due to the variability observed within a single species. In our study, we used a portable devise to measure these emissions from 114 Eucalyptus urophylla trees within the same plantation, uncovering variances that spanned more than tenfold. Given the impracticality of measuring such a large number of trees to obtain statistically representative emissions data that accounts for intraspecific variability, we proposed a simpler way to get accurate measurements by strategically selecting a smaller subset of trees. This method drastically cuts down the effort and time needed for such studies, making it easier to gather reliable data in natural environments.
Biogenic volatile organic compound (BVOC) emission factors (Es) for 114 Eucalyptus urophylla individuals were measured in situ Intraspecific variation in Es of BVOC exceeded an order of magnitude, with average Es statistically representative A novel method was introduced for fast, accurate and efficient measurement of representative Es of BVOC with reduced sample siz
Tetrabromobisphenol-A/S and their derivatives in surface particulates from workshop floors of three representative e-waste recycling sites in China
No full textSurface particulates collected from the workshop floors of three major e-waste recycling sites (Taizhou, Qingyuan, and Guiyu) in China were analyzed for tetrabromobisphenol A/S (TBBPA/S) and their derivatives to investigate the environmental pollution caused by e-waste recycling activities. Mean concentrations of total TBBPA/S analogs in surface particulates were 31,471-116,059 ng/g dry weight (dw). TBBPA, TBBPA-BGE, and TBBPA-BDBPE were the most frequently detected in particulates with average concentration ranges of 17,929-78,406, 5601-15,842, and 5929-21,383 ng/g dw, respectively. Meanwhile, TBBPA, TBBPA-BGE, and TBBPA-BDBPE were the most abundant TBBPA/S analogs, accounting for around 96% of the total. The composition profiles of TBBPA/S analogs differed significantly among three e-waste sites. Similarly, principal component analysis uncovered different pollution patterns among different sites. The discrepancy in the profiles of TBBPA/S analogs largely relied on the e-waste types recycled in different areas. E-waste recycling led to the release of TBBPA/S analogs, and TBBPA/S analogs produced differentiation during migration from source (surface particulates) to nearby soil. More researches are necessary to find a definite relationship between pollution status and e-waste types and study differentiation behavior of TBBPA/S analogs in migration and diffusion from source to environmental medium