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Spatiotemporal Analysis of Surface Water Tetrachloroethene in New Jersey

Spatiotemporal Analysis of Surface Water Tetrachloroethene in New Jersey. Presentation of the project of Yasuyuki Akita Temporal GIS Fall 2004. Agenda. About Tetrachloroethene Monitoring Data Details of BME Method BME Analysis Results of BME Analysis New Criterion Model Comparison

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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

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