Concentration profiles of per- and polyfluoroalkyl substances in major sources to the environment

Perfluoroalkyl and Polyfluoroalkyl Substances (PFASs) pose a substantial threat as endocrine disruptors, and thus early identification of those that may interact with steroid hormone receptors, such as the androgen receptor (AR), is critical. In this study we screened 5,206 PFASs from the CompTox database against the different binding sites on the AR using both molecular docking and machine learning techniques. We developed support vector machine models trained on Tox21 data to classify the active and inactive PFASs for AR using different chemical fingerprints as features. The maximum accuracy was 95.01% and Matthew’s correlation coefficient (MCC) was 0.76 respectively, based on MACCS fingerprints (MACCSFP). The combination of docking-based screening and machine learning models identified 29 PFASs that have strong potential for activity against the AR and should be considered priority chemicals for biological toxicity testing.

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Measured and Modelled Chlorinated Contaminant Distributions in the St. Clair River Water

Water Quality Research Journal ◽

10.2166/wqrj.1986.029 ◽

1986 ◽

Vol 21 (3) ◽

pp. 332-343 ◽

Cited By ~ 4

Author(s):

C.H. Chan ◽

Y.L. Lau ◽

B.G. Oliver

Keyword(s):

River Water ◽

Suspended Sediment ◽

Water Samples ◽

Concentration Distribution ◽

Suspended Solids ◽

Industrial Area ◽

Concentration Profiles ◽

Detroit River ◽

Chemical Partitioning ◽

Transverse Mixing

Abstract The concentration distribution of hexachlorobutadiene (HCBD), pentachloro-benzene (QCB), hexachlorobenzene (HCB) and octachlorostyrene (OCS) in water samples from transects across the upper and lower St. Clair River and the upper Detroit River were determined on four occasions in 1985. The data show a plume of these contaminants from the Sarnia industrial area. The fluxes and concentration profiles of the contaminants at Port Lambton have been modelled success fully using a simple transverse mixing model. A study on the chemical partitioning between the “dissolved” and “suspended sediment” phases shows that an important contaminant fraction is carried in the river by the suspended solids, particularly for lipophilie compounds such as HCB and OCS,

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A Stationary Packer System for Layerwise Groundwater Sampling in Monitoring Wells – Technique and Results

Water Science & Technology ◽

10.2166/wst.1991.0454 ◽

1991 ◽

Vol 23 (1-3) ◽

pp. 545-553

Author(s):

M. Rödelsperger ◽

U. Rohmann ◽

F. Frimmel

Keyword(s):

Groundwater Discharge ◽

Groundwater Table ◽

Experimental Results ◽

Concentration Profiles ◽

Sampling Device ◽

Local Conditions ◽

Monitoring Wells ◽

Deep Aquifers ◽

Groundwater Sampling ◽

Groundwater Samples

A sampling device was designed as a stationary equipment for deep monitoring wells in order to obtain representative groundwater samples from different layers of the aquifer. The device consists of several packer units which can be combined at variable distances, allowing adaption to the local conditions of the aquifer and of the well. The pumps are situated below the groundwater table. Each of the drawing tubes ends between two packers at the concerning depth. Experimental results demonstrate the importance of the application of a stationary packer system instead of a mobile doublepacker in deep aquifers of inhomogeneous structure. Examples of concentration profiles obtained from layerwise groundwater sampling are given and a technique for selective groundwater discharge is described.

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Selection of one-dimensional sedimentation: models for on-line use

Water Science & Technology ◽

10.2166/wst.1995.0100 ◽

1995 ◽

Vol 31 (2) ◽

pp. 193-204 ◽

Cited By ~ 7

Author(s):

Koen Grijspeerdt ◽

Peter Vanrolleghem ◽

Willy Verstraete

Keyword(s):

Steady State ◽

Selection Criteria ◽

Data Sets ◽

Concentration Profiles ◽

A Posteriori ◽

One Dimensional ◽

On Line ◽

Dynamic Concentration ◽

Selection Of ◽

Modelling Task

A comparative study of several recently proposed one-dimensional sedimentation models has been made. This has been achieved by fitting these models to steady-state and dynamic concentration profiles obtained in a down-scaled secondary decanter. The models were evaluated with several a posteriori model selection criteria. Since the purpose of the modelling task is to do on-line simulations, the calculation time was used as one of the selection criteria. Finally, the practical identifiability of the models for the available data sets was also investigated. It could be concluded that the model of Takács et al. (1991) gave the most reliable results.

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Modeling mass transfer and substrate utilization in the boundary layer of biofilm systems

Water Science & Technology ◽

10.2166/wst.1998.0603 ◽

1998 ◽

Vol 37 (4-5) ◽

pp. 139-147 ◽

Cited By ~ 6

Author(s):

Harald Horn ◽

Dietmar C. Hempel

Keyword(s):

Boundary Layer ◽

Mass Transfer ◽

Reynolds Number ◽

Film Theory ◽

Substrate Utilization ◽

The Other ◽

Concentration Profiles ◽

Hydrodynamic Conditions ◽

Time Axis ◽

Transfer Coefficients

The use of microelectrodes in biofilm research allows a better understanding of intrinsic biofilm processes. Little is known about mass transfer and substrate utilization in the boundary layer of biofilm systems. One possible description of mass transfer can be obtained by mass transfer coefficients, both on the basis of the stagnant film theory or with the Sherwood number. This approach is rather formal and not quite correct when the heterogeneity of the biofilm surface structure is taken into account. It could be shown that substrate loading is a major factor in the description of the development of the density. On the other hand, the time axis is an important factor which has to be considered when concentration profiles in biofilm systems are discussed. Finally, hydrodynamic conditions become important for the development of the biofilm surface when the Reynolds number increases above the range of 3000-4000.

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Electrochemical Oxidation of Perfluorooctanesulfonate by Magnéli Phase Ti4O7 Electrode in the Presence of Trichloroethylene

10.21926/aeer.2004006 ◽

2020 ◽

Vol 1 (4) ◽

Author(s):

Peizeng Yang ◽

Yaye Wang ◽

Junhe Lu ◽

Viktor Tishchenko ◽

Qingguo Huang ◽

...

Keyword(s):

Electrochemical Oxidation ◽

Current Density ◽

First Order ◽

Degradation Rates ◽

Oxidation Technology ◽

Magnéli Phase ◽

Polyfluoroalkyl Substances ◽

Titanium Suboxide ◽

Gas Tight ◽

Magneli Phase

This study examined the degradation of perfluorooctanesulfonate (PFOS) in electrochemical oxidation (EO) processes in the presence of trichloroethylene (TCE). The EO experiment was performed in a gas-tight reactor using Magnéli phase titanium suboxide (Ti4O7) as the anode. The experimental data demonstrated that 75% of PFOS (2 μM) was degraded at 10 mA/cm2 current density in 30 min without TCE present in the solution, while the presence of 76 μM TCE apparently inhibited the degradation of PFOS, reducing its removal down to 53%. Defluorination ratio suggested that PFOS was significantly mineralized upon EO treatment, and it appeared to be not influenced by the presence of TCE. The respective pseudo-first order rate constants (kobs) of PFOS removal were 0.0471 and 0.0254 min-1 in the absence and presence of TCE. The degradation rates of both PFOS and TCE increased with current density rising from 2.5 to 20 mA/cm2. In the presence of TCE, chloride, chlorate, and perchlorate were formed that accounted for 79.7 %, 5.53%, and 1.51% of the total chlorine at 60 min. This work illustrates the promise of the Magnéli phase Ti4O7 electrode based electrochemical oxidation technology for degrading per- and polyfluoroalkyl substances (PFASs) and co-contaminants in groundwaters.

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The calculation of mass transfer coefficients and of axial dispersion coefficients from concentration profiles

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19653822 ◽

1965 ◽

Vol 30 (11) ◽

pp. 3822-3833 ◽

Cited By ~ 9

Author(s):

V. Rod

Keyword(s):

Mass Transfer ◽

Axial Dispersion ◽

Concentration Profiles ◽

Transfer Coefficients ◽

Dispersion Coefficients ◽

Mass Transfer Coefficients

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An experimental study of gas phase back mixing under the counter-current gas-liquid flow on a vertical expanded metal sheet packing by static tracer technique

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19800214 ◽

1980 ◽

Vol 45 (1) ◽

pp. 214-221

Author(s):

Jan Červenka ◽

Mirko Endršt ◽

Václav Kolář

Keyword(s):

Gas Phase ◽

Flow Model ◽

Plug Flow ◽

Packed Bed ◽

Metal Sheet ◽

Concentration Profiles ◽

Expanded Metal ◽

Gas Liquid Flow ◽

Counter Current ◽

Back Mixing

Gas phase back mixing has been measured in a column packed with vertical expanded metal sheet under the counter-current flow of gas and liquid by the static method using a tracer. The observed experimental concentration profiles has not confirmed our earlier proposed model of back mixing, based on the concentration profiles in absorption runs. These profiles do not even conform with the axially dispersed plug flow model currently used to describe axial mixing in packed bed columns. The concentration profiles may be described by a combination of the axially dispersed plug flow model with back flow.

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