Forecasts using Box-Jenkins models for the ambient air quality data of Delhi City.

The monthly maximum of the 24-h average time-series data of ambient air quality-sulphur dioxide (SO(2)), nitrogen dioxide (NO(2)) and suspended particulate matter (SPM) concentration monitored at the six National Ambient Air Quality Monitoring (NAAQM) stations in Delhi, was analysed using Box-Jenkins modelling approach (Box et al. 1994). Univariate linear stochastic models were developed to examine the degree of prediction possible for situations where only the past record of pollutant data are available. In all, 18 models were developed, three for each station for each of the respective pollutant. The model evaluation statistics suggest that considerably satisfactory real-time forecasts of pollution concentrations can be generated using the Box-Jenkins approach. The developed models can be used to provide short-term, real-time forecasts of extreme air pollution concentrations for the Air Quality Control Region (AQCR) of Delhi City, India.

Long-term impact of manuring and fertilization on enrichment, stability and quality of organic carbon in Inceptisol under two potato-based cropping systems.

Soil organic matter (SOM) stability is a prerequisite for long-term C sequestration. The long-term effect of manuring and fertilization on stability of SOM in rice-potato-wheat (R-P-W) and maize-potato-onion (M-P-O) cropping systems was studied in an Inceptisol of semi-arid subtropical India. Soil samples were collected (0-15 and 15-30cm soil depths) from the following treatments: control, 100% NPK-Fertilizer, 100% N-Vermicompost (VC), 50% NPK-Fertilizer+50%N-Vermicompost (VC), 100%NPK-Fertilizer+crop residue (CR), 100% N-VC+CR. The stability of SOM was studied by correlating the ammonium oxalate extractable Fe, Al and Si with stable soil organic C (SOC). Application of 100% N-VC and 100% N-VC+CR increased the SOC stock by 66% and 32%, respectively over 100% NPK in R-P-W cropping system, while in M-P-O system, the above treatments increased the SOC stock by 28% and 12%. As compared to 100%NPK, the integrated use of 50%NPK+50%N-VC increased the SOC stock by 58% and 35% in R-P-W and M-P-O system, respectively. The extractable Fe, Al and Si significantly correlated with stable OC and the multiple regression model developed between these parameters could well predict the stable OC in soil. Complete or partial substitution of chemical fertilizer N with VC could be a promising nutrient management strategy for enhancing the SOC stock in Inceptisol under potato-based cropping systems of semi-arid sub-tropical India. However, the integrated use of 50%NPK+50%N-VC could be promising due to lowest yield reductions and moderate SOC sequestration potential. The enrichment (47%), as well as quality (81%) of SOC was higher in R-P-W system than in M-P-O system. The organic treatments like 100%NPK+CR and 100%N-VC+CR showed higher stability of SOC in R-P-W (31% and 26%) than in M-P-O cropping system. The stability of SOC could well be predicted by extractable amorphous and poorly crystalline Fe, Al and Si and SOC in both the cropping systems.