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Estimation of SO_2 and NO_2 Concentrations in Jakarta-Indonesia Using Cokriging Method

Devy Setiyowati , Sutikno

Abstract



The increased of population activities in Jakarta, demonstrates trends in lowering air quality. Air pollutants Sulpher Dioxide (SO2) as well as Nitrogen Dioxide (NO2) is commonly due to motorized vehicle and industrial activity. The direct measurement of SO2 and NO2 concentration are costly and require a long process, thus the measurement of both emissions is only conducted in a certain area of Jakarta. Indirect measurement of both emissions of SO2 and NO2 for other areas of Jakarta can be conducted by interpolation using cokriging method. Cokriging is the estimation method for minimizing variance of error estimation using cross-correlation between primary and secondary variables. By applying 12-month data measurement in 2012, the estimated results of SO2 for January, February, March, May, and July are produced using cokriging with variogram isotropy. Meanwhile, for other months, concentrations of NO2 as a secondary variable are less able to estimate the result for SO2 concentration using cokriging with minimum value of R2. The best result using cokriging method by variogram isotropy was in January with the estimated value of SO2 between 4.9 and 17.6 g/m3. The standard deviation of estimated SO2 were very small, between 0.00 to 3.35 g/m3. The value of R2 from cross validation is 100 percent. In other words, the result is estimated accurately from actual value or without any deviation from the original value.

Keywords


cokriging, interpolation, variogram, cross variogram, air pollutans.

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