spatiotemporal analysis of surface water tetrachloroethene in new jersey n.
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Spatiotemporal Analysis of Surface Water Tetrachloroethene in New Jersey
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  1. Spatiotemporal Analysis ofSurface Water Tetrachloroethene in New Jersey Presentation of the project of Yasuyuki Akita Temporal GIS Fall 2004

  2. Agenda • About Tetrachloroethene • Monitoring Data • Details of BME Method • BME Analysis • Results of BME Analysis • New Criterion • Model Comparison • Conclusion

  3. About Tetrachloroethene

  4. About Tetrachloroethene • Tetrachloroethene: C2Cl4 • Volatile organic compound • Nonflammable colorless liquid at room temperature • Ether-like odor • Synonym: Tetrachloroethylene, Perchloroethylene, and PCE

  5. Use and Production • Mainly Used for dry cleaning, chemical intermediates, and industrial solvent • PCE used in dry cleaning industry has been declining during 90s • Recent Demand: 763 million lb (1980)    318 million lb (1999)

  6. End-Use Pattern in 70s and 90s

  7. Exposure pathway • Primary route • Inhalation • Ingestion of contaminated food and water • Widely distributed in environment • 38% of surface water sampling sites in the U.S. • 771 of the 1430 National Priorities List sites • 154 of 174 surface water samples in N.J. (1977~1979)

  8. Health Effect of Tetrachloroethene • Acute Effect (inhalation exposure) • Dizziness, headache, sleepiness, confusion, nausea, difficulty in speaking and walking, unconsciousness, and death • Chronic Effect (oral/inhalation exposure) • Detrimental effect to kidney and liver

  9. Carcinogenicity • Reasonably anticipated to be a human carcinogen (US DHHS) • Group 2A (Probably carcinogenic to humans) (IARC) • Animal studies: tumors in liver and kidney

  10. Quality Standard for Tetrachloroethene • Maximum Contaminant Level (MCL) in drinking water - 0.005 mg/L • Surface Water Quality Standard in New Jersey - 0.388 μg/L N.J. adopted more stringent standard

  11. Monitoring Data

  12. Monitoring Dataset for New Jersey • Data Source • NJDEP/USGS Water Quality Network Website • EPA STORET database • Data used in this study • 369 measured values • 171 monitoring stations • From 1999 to 2003

  13. Monitoring Data – Histogram Raw Data Log-Transformed Data

  14. Monitoring Data – Statistical Moments

  15. Distribution of Data Points

  16. Distribution of Data Points

  17. Distribution of Data Values

  18. What we want to know is … • Challenge of our research • Assess all river reaches • Taking into account the space/time variability Framework for the space/time estimation Bayesian Maximum Entropy (BME) analysis of TGIS

  19. Details of BME Method

  20. Space/Time Random Field • The concentration field is modeled in terms of Space/Time Random Field (S/TRF) • Collection of random variables S/TRF: Collection of all possible realization • Stochastic characterization of S/TRF is provided by multivariate PDF

  21. Knowledge Base • General Knowledge Base: G • Describe global characteristics of the random field of interest • Expressed as statistical moments • Site-specific knowledge Base: S • Available monitoring data over the space/time domain of interest • Total Knowledge Base: K • K = G∪ S

  22. General Knowledge Base G Mean Trend • Global trend of the S/TRF of interest • Covariance • Measure of dependency between two points • Sill = variance = covariance(r=0) • Range shows the extent that co-variability exists

  23. BME analysis of Temporal GIS • Prior stage • Examine all general knowledge base G and calculate Prior PDF • Integration stage • Update Prior PDF using Bayesian conditionalization on the site-specific knowledge base S and obtain posterior PDF • Interpretive stage • Obtain estimation value from Posterior PDF

  24. BME analysis of Temporal GIS • General KB Prior PDF • Update prior PDF with Site-specific KB • Bayesian conditionalization • Posterior PDF is given by conditional probability

  25. t t Posterior PDF at estimation point long long lati lati fK(ck) Estimation Value Summary of BME analysis of TGIS • General KB • Mean trend • Covariance • Site-Specific KB • Hard Data BME Estimation Point Data Point

  26. BME Analysis

  27. S/TRF for Log-transformed PCE concentration • S/TRF representing Log-tranformed concentration: • Residual field describes purely stochastic aspect of the concentration field Mean Trend Residual Field

  28. Mean Trend of Log-transformed concentration field • Mean trend consist of two components • Purely spatial component • Purely temporal component • Each component is calculated by exponential smoothing

  29. Mean Trend – Temporal Component • Increase from Jan. 1999 to Jan. 2003 • Decrease from Jan. 2003~

  30. Mean Trend – Spatial Component • Contaminated Area • Northeastern region • Southwestern region

  31. Homogeneous/Stationary S/TRF Log-transformed data • Homogeneous/Stationary Random Field • Its mean trend is constant • Its covariance is only function of the spatial lag and temporal lag Removing the mean trend Residual data for S/TRF:

  32. Covariance for Residual S/TRF

  33. Covariance for Residual S/TRF

  34. Experimental Data Covariance Model Covariance Surface

  35. Results of BME Analysis

  36. BME Estimation – Temporal Fluctuation

  37. BME Estimation – Spatial Distribution

  38. BME Estimation – Spatial Distribution

  39. BME Estimation – Spatial Distribution (Apr. 15, 2002)

  40. BME Estimation – Contaminated Area Area above the quality standard: 0.388μg/L (Apr. 15, 2002) • BME mean estimate • Upper bound of the BME 68% confidence interval • Upper bound of the BME 95% confidence interval

  41. BME Estimation – Along River Stream • Equidistance points along river stream • More accurate estimation for surface water

  42. BME Estimation – Along River Stream • Fraction of river miles that does not attain the quality standard

  43. New Criterion

  44. Assessment Criterion • S/TRF is characterized by Posterior PDF • Area under the curve = Probability Prob[PCE>QSTD]=Area under the curve (QSTD<PCE<∞)

  45. Assessment Criterion Prob[Non-Attainment]=Prob[PCE>0.388μg] • Highly Likely in Attainment • Prob[Non-Attainment]<10% • Highly Likely in Non-Attainment • Prob[Non-Attainment]>90% • Non-Assessment • 10%≦Prob[Non-Attainment]≦90% • More Likely Than Not in Non-Attainment • Prob[Non-Attainment]>50%

  46. Fraction of River Miles

  47. Identifying Contaminated WMAs • The state of New Jersey is divided into 20 Watershed Management Area (WMA) • Assess which part of the state is contaminated • Contribution of each WMA to the fraction of river miles assessed as • Highly Likely in Non-Attainment • More Likely Than Not in Non-Attainment

  48. Contribution of WMAs • Highly Likely in Non-Attainment

  49. Contribution of WMAs • More Likely Than Not in Non-Attainment

  50. Fraction of River Miles in WMAs