Space and Time Distribution of Antifouling Agent in Aquatic - - PowerPoint PPT Presentation

▶
space and time distribution of antifouling agent in
SMART_READER_LITE
LIVE PREVIEW

Space and Time Distribution of Antifouling Agent in Aquatic - - PowerPoint PPT Presentation

Jan 04, 2024 369 likes •572 views

Space and Time Distribution of Antifouling Agent in Aquatic Environment Kiyoshi Shibata 1),2) , Shinobu Sugasawa 1) , Yoshitaka Yamaguchi 1) , Vasileios A.Sakkas 3) , Fumitoshi Kitamura 1 ) , Tetsuya Senda 1 ) 1) National Maritime Research

slide-1
SLIDE 1

Space and Time Distribution of Antifouling Agent in Aquatic Environment

Kiyoshi Shibata1),2), Shinobu Sugasawa1), Yoshitaka Yamaguchi1), Vasileios A.Sakkas3), Fumitoshi Kitamura1 ), Tetsuya Senda1 ) 1) National Maritime Research Institute, 2) Now; Chiba Institute of Technology, Japan 3) University of Ioannina, Greece

ISST2007 7 September, 2007 Osaka

slide-2
SLIDE 2

Background

  • Some of the “alternative” antifouling agents

are toxic, and their actual degradation performance in the environment is still not clear.

  • It is a general practice to compare PEC and

PNEC of the substance to evaluate environmental risk.

  • The PEC calculation is made by simulating all

relating fate processes.

  • The photo-degradation is an unique one

among the fate processes..

slide-3
SLIDE 3

Background

  • The light intensity changes drastically

with time or depth.

  • If the anti-faulant is sensitive to light, its

concentration changes with time and location.

  • The environmental risk can vary with

time and space.

slide-4
SLIDE 4

Purpose

  • To investigate the possibility of

concentration fluctuation/change.

  • A simple 2D unsteady state model has

been developed, simulating the leaching, diffusion and degradation process of the antifouling agent in the environment.

slide-5
SLIDE 5

Two dimensional unsteady state model

Leaching Diffusion Photodegradation

３ｍ 25m

slide-6
SLIDE 6

Release Rate

200 400 600 800 1000 10 20 30 時間（hr) 濃度（ppb) 0rpm 30rpm 60rpm 180rpm 200 400 600 800 1000 10 20 30 時間(hr) 濃度（ppb) 0rpm 30rpm 60rpm 180rpm

dC/dｔ ＝ k （Csat－C）

slide-7
SLIDE 7

Diffusion

  • Diffusion

Jx = Deff,x dC/dx Jz = Deff,z dC/dz

Jx :Flux in horizontal direction, Deff,x :Effective diffusion constant in horizontal direction x : horizontal distance Jz : Flux in vertical direction Deff,z: Effective diffusion constant in vertical direction z : vertical distance

slide-8
SLIDE 8

Photodegradation Model

  • Rate constant：proportional to sunlight

k ＝α I

I : Light irradiation intensity (Permeability, Wave length, Suspended/Dissolved Matter, Latitude, Season, Time, Weather ）

Photodegradation Kinetics

  • First order kinetics

dC/dt＝－kC

K.Shibata NMRI

C:Concentration, t:Time, k:Rate Constant

slide-9
SLIDE 9

Sun Light Irradiation Intensity

IZ=0=0 0 < t < 6 I Z=0= I Z=0, t=12 [1－cos{π ( t－6 ) / 6}]/2 6 < t < 18 I Z=0=0 18 < t < 24

0.2 0.4 0.6 0.8 1 1.2 6 12 18 24 Time (hour)

Dimensionless Sun Light Intensity (-)

slide-10
SLIDE 10
  • 2
  • 1

1 2 3 20 40 60 80 100 120 Depth (m) Log[Intensity/(10-6W/cm2/nm)]

400nm 500nm 600nm 700nm

  • Conc. Of Chlorophyll-α

(10-6g/L) 21.5 @Tokyo Bay 0.66 @ Sagami Bay 0.0813 @Pacific Ocean after Kishino(1994) K.Shibata NMRI

Decrease in light irradiation intensity in water column

I = I0×10-βZ

slide-11
SLIDE 11

Concentration Change along Time and Space

5 10 15 20 50 100 150 200 Time (hr) Concentration (mg/m3)

Z=0.05m Z=1.45m Z=2.95m

1m from coating surface

slide-12
SLIDE 12

Concentration Change along Time and Space

5 10 15 20 50 100 150 200 TIme (hr) Concnetration (mg/m3)

Z=0.05m Z=1.45m Z=2.95m

5 10 15 20 50 100 150 200 Time (hr) Concentration (mg/m3)

Z=0.05m Z=1.45m Z=2.95m

5m from coating surface 20m from coating surface

slide-13
SLIDE 13

Effects of the Diffusion Coefficients

Deff,x:3.6x10-2 m2/hr, Deff,z: 3.6x10-4m2/hr Deff,x:3.6x10-3 m2/hr Deff,z: 3.6x10-5m2/hr

Concentration Change in the day 7 at the point 1m from the painted surface

10 20 30 40 50 6 12 18 24 Time (hr) Concnetration (mg/m3) 0.05 0.85 1.75 2.65 10 20 30 40 50 6 12 18 24 Time (hr) Concentration (mg/m3) 0.05 0.85 1.75 2.65

slide-14
SLIDE 14

Discussions

  • Importance of the sensitivity of the

photolysis rate to the depth in water column.

  • It might be worth while to examine the

concentration distribution along the depth of water column , or at night.

slide-15
SLIDE 15

Discussions / Questions

  • PEC ; How to make average?

The highest concentration in a short time period and narrow space, or averaged one in a long time period and large area?

  • What is adequate or proper end point to

assess the environmental risk?

slide-16
SLIDE 16

Conclusion

  • A simple model to predict the concentration

distribution of antifouling agent in aquatic environment was developed to look into the effect of photodegradation on the concentration distribution.

  • The model clearly indicats that the effect of the

change in sun light irradiation intensity and penetration of the light in the water column is significant in accumulation of the antifouling agent in water column. The concentration may be seriously high at deep water or at night.

  • If the concentration distribution is steep and changing

rapidly, special care has to be paid to select the end point for the environmental risk assessment.

slide-17
SLIDE 17

Future Task

  • Evaluation of the parameters
  • Introduction of water flow model
  • Evaluation of hydrolysis and biolysis, as

well as adsorption, as fate processes

  • Discussion on the end point
slide-18
SLIDE 18

Acknowledgement

  • Ministry of Environment
  • Japanese Society for the Promotion
  • f Science
  • Chugoku Marine Paint
slide-19
SLIDE 19

Apologize by KS

Any questions and comments, to Kiyoshi SHIBATA

  • f Chiba Institute of Technology

kyshibt@sky.it-chiba.ac.jp