Particle/gas partitioning behavior of polychlorinated biphenyls (PCBs) in global atmosphere: Equilibrium or steady state?

ABSTRACT Unicellular protozoan grazers represent a size class of organisms where a transition in the mechanism of chlorobiphenyl (CB) introduction, from diffusion through surface membranes to ingestion of contaminated prey, could occur. This study compares the relative importance of these two processes in the overall uptake of polychlorinated biphenyls by protists. Uptake rates and steady-state concentrations were compared in laboratory cultures of grazing and nongrazing protozoa. These experiments were conducted with a 10-μm marine scuticociliate (Uronema sp.), bacterial prey (Halomonas halodurans), and a suite of 21 CB congeners spanning a range of aqueous solubilities. The dominant pathway of CB uptake by both grazing and nongrazing protozoa was diffusion. Organic-carbon-normalized CB concentrations (in the protozoan cell) were equivalent in grazing and nongrazing protozoa for all congeners studied. Rate constants for uptake into and loss from the protozoan cell were independently determined by using [3,3′,4,4′-14C]tetrachlorobiphenyl (IUPAC no. 77), 0.38 ± 0.03 min−1 and (1.1 ± 0.1) × 10−5 (g of organic carbon)−1min−1, respectively. Magnitudes of the uptake and loss processes were calculated and compared by using a numerical model. The model result was consistent with data from the bioaccumulation experiment and supported the hypothesis that diffusive uptake is faster than ingestive uptake in phagotrophic unicellular protozoa.

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Partitioning behavior of polychlorinated biphenyls

Chemosphere ◽

10.1016/0045-6535(85)90111-0 ◽

1985 ◽

Vol 14 (11-12) ◽

pp. 1703-1716 ◽

Cited By ~ 21

Author(s):

Lawrence P. Burkhard ◽

David E. Armstrong ◽

Anders W. Andren

Keyword(s):

Polychlorinated Biphenyls ◽

Partitioning Behavior

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Prediction of gas/particle partitioning of polybrominated diphenyl ethers (PBDEs) in global air: A theoretical study

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-1669-2015 ◽

2015 ◽

Vol 15 (4) ◽

pp. 1669-1681 ◽

Cited By ~ 44

Author(s):

Y.-F. Li ◽

W.-L. Ma ◽

M. Yang

Keyword(s):

Steady State ◽

Equilibrium State ◽

Polybrominated Diphenyl Ethers ◽

Partition Coefficients ◽

Pbde Congener ◽

Threshold Values ◽

Diphenyl Ethers ◽

Special Case ◽

Partitioning Behavior ◽

Non Equilibrium

Abstract. Gas/particle (G/P) partitioning of semi-volatile organic compounds (SVOCs) is an important process that primarily governs their atmospheric fate, long-range atmospheric transport, and their routes of entering the human body. All previous studies on this issue are hypothetically based on equilibrium conditions, the results of which do not predict results from monitoring studies well in most cases. In this study, a steady-state model instead of an equilibrium-state model for the investigation of the G/P partitioning behavior of polybrominated diphenyl ethers (PBDEs) was established, and an equation for calculating the partition coefficients under steady state (KPS) of PBDEs (log KPS = log KPE + logα) was developed in which an equilibrium term (log KPE = log KOA + logfOM −11.91 where fOM is organic matter content of the particles) and a non-equilibrium term (log α, caused by dry and wet depositions of particles), both being functions of log KOA (octanol–air partition coefficient), are included. It was found that the equilibrium is a special case of steady state when the non-equilibrium term equals zero. A criterion to classify the equilibrium and non-equilibrium status of PBDEs was also established using two threshold values of log KOA, log KOA1, and log KOA2, which divide the range of log KOA into three domains: equilibrium, non-equilibrium, and maximum partition domain. Accordingly, two threshold values of temperature t, tTH1 when log KOA = log KOA1 and tTH2 when log KOA = log KOA2, were identified, which divide the range of temperature also into the same three domains for each PBDE congener. We predicted the existence of the maximum partition domain (the values of log KPS reach a maximum constant of −1.53) that every PBDE congener can reach when log KOA ≥ log KOA2, or t ≤ tTH2. The novel equation developed in this study was applied to predict the G/P partition coefficients of PBDEs for our Chinese persistent organic pollutants (POPs) Soil and Air Monitoring Program, Phase 2 (China-SAMP-II) program and other monitoring programs worldwide, including in Asia, Europe, North America, and the Arctic, and the results matched well with all the monitoring data, except those obtained at e-waste sites due to the unpredictable PBDE emissions at these sites. This study provided evidence that the newly developed steady-state-based equation is superior to the equilibrium-state-based equation that has been used in describing the G/P partitioning behavior over decades. We suggest that the investigation on G/P partitioning behavior for PBDEs should be based onsteady-state, not equilibrium state, and equilibrium is just a special case of steady-state when non-equilibrium factors can be ignored. We also believe that our new equation provides a useful tool for environmental scientists in both monitoring and modeling research on G/P partitioning of PBDEs and can be extended to predict G/P partitioning behavior for other SVOCs as well.

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Prediction of gas/particle partitioning of polybrominated diphenyl ethers (PBDEs) in global air: a theoretical study

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-23415-2014 ◽

2014 ◽

Vol 14 (16) ◽

pp. 23415-23451 ◽

Cited By ~ 2

Author(s):

Y.-F. Li ◽

W.-L. Ma ◽

M. Yang

Keyword(s):

Steady State ◽

Equilibrium State ◽

Polybrominated Diphenyl Ethers ◽

Partition Coefficients ◽

State Model ◽

Monitoring Data ◽

Threshold Values ◽

Diphenyl Ethers ◽

Special Case ◽

Partitioning Behavior

Abstract. Gas/particle (G / P) partitioning for most semivolatile organic compounds (SVOCs) is an important process that primarily governs their atmospheric fate, long-range atmospheric transport potential, and their routs to enter human body. All previous studies on this issue have been hypothetically derived from equilibrium conditions, the results of which do not predict results from monitoring studies well in most cases. In this study, a steady-state model instead of an equilibrium-state model for the investigation of the G / P partitioning behavior for polybrominated diphenyl ethers (PBDEs) was established, and an equation for calculating the partition coefficients under steady state (KPS) for PBDE congeners (log KPS = log KPE + logα) was developed, in which an equilibrium term (log KPE = log KOA + logfOM −11.91, where fOM is organic matter content of the particles) and a nonequilibrium term (logα, mainly caused by dry and wet depositions of particles), both being functions of log KOA (octanol-air partition coefficient), are included, and the equilibrium is a special case of steady state when the nonequilibrium term equals to zero. A criterion to classify the equilibrium and nonequilibrium status for PBDEs was also established using two threshold values of log KOA, log KOA1 and log KOA2, which divide the range of log KOA into 3 domains: equilibrium, nonequilibrium, and maximum partition domains; and accordingly, two threshold values of temperature t, tTH1 when log KOA = log KOA1 and tTH2 when log KOA = log KOA2, were identified, which divide the range of temperature also into the same 3 domains for each BDE congener. We predicted the existence of the maximum partition domain (the values of log KPS reach a maximum constant of −1.53) that every PBDE congener can reach when log KOA ≥ log KOA2, or t ≤ tTH2. The novel equation developed in this study was applied to predict the G / P partition coefficients of PBDEs for the published monitoring data worldwide, including Asia, Europe, North America, and the Arctic, and the results matched well with all the monitoring data, except those obtained at e-waste sites due to the unpredictable PBDE emissions at these sites. This study provided evidence that, the new developed steady-state-based equation is superior to the equilibrium-state-based equation that has been used in describing the G / P partitioning behavior in decades. We suggest that, the investigation on G / P partitioning behavior for PBDEs should be based on steady state, not equilibrium state, and equilibrium is just a special case of steady state when nonequilibrium factors can be ignored. We also believe that our new equation provides a useful tool for environmental scientists in both monitoring and modeling research on G / P partitioning for PBDEs and can be extended to predict G / P partitioning behavior for other SVOCs as well.

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Application of steady-state kinetics to explain partitioning behavior of hydrophobic organic chemicals: A critique of “particle-induced” desorption

Chemosphere ◽

10.1016/0045-6535(88)90174-9 ◽

1988 ◽

Vol 17 (6) ◽

pp. 1085-1088 ◽

Cited By ~ 3

Author(s):

Sheldon S. Lande

Keyword(s):

Steady State ◽

Organic Chemicals ◽

Hydrophobic Organic Chemicals ◽

Steady State Kinetics ◽

Partitioning Behavior

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Comparative Specificities of Two Evolutionarily Divergent Hydrolases Involved in Microbial Degradation of Polychlorinated Biphenyls

Journal of Bacteriology ◽

10.1128/jb.183.5.1511-1516.2001 ◽

2001 ◽

Vol 183 (5) ◽

pp. 1511-1516 ◽

Cited By ~ 37

Author(s):

Stephen Y. K. Seah ◽

Geneviève Labbé ◽

Stefan R. Kaschabek ◽

Frank Reifenrath ◽

Walter Reineke ◽

...

Keyword(s):

Steady State ◽

Polychlorinated Biphenyls ◽

Microbial Degradation ◽

Apparent Homogeneity ◽

Steady State Kinetics ◽

Hydrolysis Of ◽

Phenyl Moiety

ABSTRACT 2-Hydroxy-6-oxo-6-phenylhexa-2,4-dienoate (HOPDA) hydrolase (BphD) is a key determinant in the aerobic transformation of polychlorinated biphenyls (PCBs) by Burkholderia sp. strain LB400 (S. Y. K. Seah, G. Labbé, S. Nerdinger, M. Johnson, V. Snieckus, and L. D. Eltis, J. Biol. Chem. 275:15701–15708, 2000). To determine whether this is also true in divergent biphenyl degraders, the homologous hydrolase of Rhodococcus globerulus P6, BphDP6, was hyperexpressed, purified to apparent homogeneity, and studied by steady-state kinetics. BphDP6hydrolyzed HOPDA with ak cat/Km of 1.62 (± 0.03) × 107 M−1 s−1 (100 mM phosphate [pH 7.5], 25°C), which is within 70% of that of BphDLB400. BphDP6 was also similar to BphDLB400 in that it catalyzed the hydrolysis of HOPDAs bearing chloro substituents on the phenyl moiety at least 25 times more specifically than those bearing chloro substituents on the dienoate moiety. However, the rhodococcal enzyme was significantly more specific for 9-Cl and 10-Cl HOPDAs, catalyzing the hydrolysis of 9-Cl, 10-Cl, and 9,10-diCl HOPDAs two- to threefold respectively, more specifically than HOPDA. Moreover, 4-Cl HOPDA competitively inhibited BphDP6 more effectively than 3-Cl HOPDA, which is the inverse of what was observed in BphDLB400. These results demonstrate that BphD is a key determinant in the aerobic transformation of PCBs by divergent biphenyl degraders, but that there exists significant diversity in the specificity of these biphenyl hydrolases.

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Studies on Water in the Hydration Chamber of a Modified Electron Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069715 ◽

1970 ◽

Vol 28 ◽

pp. 544-545

Author(s):

R. C. Moretz ◽

G. G. Hausner ◽

D. F. Parsons

Keyword(s):

Thin Film ◽

Thin Films ◽

Electron Microscope ◽

Steady State ◽

Room Temperature ◽

Small Mass ◽

Equilibrium Pressure ◽

Biological Objects ◽

Mechanical Pump ◽

Differential Pumping

Use of the electron microscope to examine wet objects is possible due to the small mass thickness of the equilibrium pressure of water vapor at room temperature. Previous attempts to examine hydrated biological objects and water itself used a chamber consisting of two small apertures sealed by two thin films. Extensive work in our laboratory showed that such films have an 80% failure rate when wet. Using the principle of differential pumping of the microscope column, we can use open apertures in place of thin film windows.Fig. 1 shows the modified Siemens la specimen chamber with the connections to the water supply and the auxiliary pumping station. A mechanical pump is connected to the vapor supply via a 100μ aperture to maintain steady-state conditions.

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Continuous hydrogenolysis of acetal-stabilized lignin in flow

Green Chemistry ◽

10.1039/d0gc02928a ◽

2021 ◽

Author(s):

Wu Lan ◽

Yuan Peng Du ◽

Songlan Sun ◽

Jean Behaghel de Bueren ◽

Florent Héroguel ◽

...

Keyword(s):

Steady State ◽

Challenges And Opportunities

We performed a steady state high-yielding depolymerization of soluble acetal-stabilized lignin in flow, which offered a window into challenges and opportunities that will be faced when continuously processing this feedstock.

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