Impact of CNG implementation on PAHs concentration in the ambient air of Delhi: A comparative assessment of pre- and post-CNG scenario

The use of alternative fuel is considered to be an effective measure to improve the urban air quality. Concerned over deteriorating air quality in Delhi, the Delhi government initiated different measures including stringent emission norms, improved fuel quality and above all introduction of cleaner fuel-CNG in public transport system. The entire city bus fleet was converted to CNG mode by 2002. The present study reports the comparative assessment of the status of air quality with respect to PM(10) and PAH before and after the introduction of CNG in public transport system in Delhi. The study has been carried out for two different time periods: first in the year 1998 and second in the year 2004. Following the total conversion of public transport system to CNG in 2002, Post-CNG data indicate a sharp reduction of 51-74% in the PM(10) concentration and 58-68% in the TPAH concentration as compared to the Pre-CNG data.     

Nickel recovery from spent nickel catalyst.

A process for nickel recovery from a spent catalyst of definite composition has been developed using the hydro-metallurgical route. The processing steps includes direct sulphuric acid leaching followed by separation of iron as well as silica and other impurities. For a 152 microm particle size catalyst, extraction of about 98% nickel was achieved at 363 K in 2 h using a sulphuric acid concentration (v/v) of 8% and a pulp density of 10%. The dissolution of nickel followed diffusion-controlled leaching kinetics. Increase in temperature and sulphuric acid concentration resulted in increase in the nickel recovery. The activation energy for nickel dissolution was calculated to be 62.8 kJ mol(-1). Finally, nickel was recovered as value-added products such as sulphide and oxalate with overall recovery of 90 and 88% of nickel, respectively.     

Assessment of the functionality of a pilot-scale reactor and its potential for electrochemical degradation of calmagite, a sulfonated azo-dye

Electrochemical degradation (ECD) is a promising technology for in situ remediation of diversely contaminated environmental matrices by application of a low level electric potential gradient. This investigation, prompted by successful bench-scale ECD of trichloroethylene, involved development, parametric characterization and evaluation of a pilot-scale electrochemical reactor for degradation of calmagite, a sulfonated azo-dye used as a model contaminant. The reactor has two chambers filled with granulated graphite for electrodes. The system has electrical potential, current, conductivity, pH, temperature, water-level and flow sensors for automated monitoring. The reactor supports outdoor and fail-safe venting, argon purging, temperature regulation and auto-shutdown for safety. Treatment involves recirculating the contaminated solution through the electrode beds at small flow velocities mimicking low fluid-flux in groundwater and submarine sediments. The first phase of the investigation involved testing of the reactor components, its parametric probes and the automated data acquisition system for performance as designed. The results showed hydraulic stability, consistent pH behavior, marginal temperature rise (<5 degrees C) and overall safe and predictable performance under diverse conditions. Near complete removal of calmagite was seen at 3-10V of applied voltage in 8-10h. The effects of voltage and strength of electrolyte on degradation kinetics have been presented. Further, it was observed from the absorption spectra that as calmagite degrades over time, new peaks appear. These peaks were associated with degradation products identified using electrospray ionization mass spectrometry. A reaction mechanism for ECD of calmagite has also been proposed.     

Effect of UV radiation and temperature on mineralization and volatilization of coumaphos in water

This study was undertaken to determine the dissipation and degradation of coumaphos [O-(3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7-yl) O,O-diethyl phosphorothioate] under different sunlight conditions and at different temperatures. The effect of the ultra violet (UV) component of solar radiation was also studied using quartz tubes in addition to other radiation in the visible range using glass tubes and the results were compared with those obtained under the dark light conditions. Water suspensions of coumaphos were incubated at three temperatures viz. 22 degrees C, 37 degrees C and 53 degrees C in closed systems to study the effect of temperature. Volatilization, mineralization and degradation of coumaphos increased with an increase in temperature and exposure to solar radiation, particularly under the UV component of the solar radiation. Major loss of the pesticide occurred through volatilization. The optimum temperature for the degradation of coumaphos was found to be at 37 degrees C. The data obtained from the mineralization and degradation studies indicated that 53 degrees C crosses the biological range for suitable growth of microorganism. UV radiation exposure along with maintaining temperature at 37 degrees C may prove useful in the dissipation and/or degradation of coumaphos prior to its disposal as waste from cattle dipping vats.     

Removal of congo red from aqueous solution by bagasse fly ash and activated carbon: kinetic study and equilibrium isotherm analyses

Present investigation deals with the utilisation of bagasse fly ash (BFA) (generated as a waste material from bagasse fired boilers) and the use of activated carbons-commercial grade (ACC) and laboratory grade (ACL), as adsorbents for the removal of congo red (CR) from aqueous solutions. Batch studies were conducted to evaluate the adsorption capacity of BFA, ACC and ACL and the effects of initial pH (pH(0)), contact time and initial dye concentration on adsorption. The pH(0) of the dye solution strongly affected the chemistry of both the dye molecules and BFA in an aqueous solution. The effective pH(0) was 7.0 for adsorption on BFA. Kinetic studies showed that the adsorption of CR on all the adsorbents was a gradual process. Equilibrium reached in about 4h contact time. Optimum BFA, ACC and ACL dosages were found to be 1, 20 and 2 g l(-1), respectively. CR uptake by the adsorbents followed pseudo-second-order kinetics. Equilibrium isotherms for the adsorption of CR on BFA, ACC and ACL were analysed by the Freundlich, Langmuir, Redlich-Peterson, and Temkin isotherm equations. Error analysis showed that the R-P isotherm best-fits the CR adsorption isotherm data on all adsorbents. The Freundlich isotherm also shows comparable fit. Thermodynamics showed that the adsorption of CR on BFA was most favourable in comparison to activated carbons.     

Contrasting temporal trends and relationships of total organic carbon, black carbon, and polycyclic aromatic hydrocarbons in rural low-altitude and remote high-altitude lakes

Historical records of total organic carbon (TOC), black carbon (BC), and polycyclic aromatic hydrocarbons (PAHs) were reconstructed in dated sediment cores from four nearby lakes in central Switzerland. In the sub-Alpine Lake Thun, located at 558 m a.s.l., the proximity to anthropogenic emission sources is reflected in higher input of BC and PAHs into sediments with fluxes only slightly decreasing during the last decades. PAH/BC ratios are relatively high and correlation between levels of total PAHs and BC is almost inexistent in Lake Thun, probably due to the presence of less condensed forms of the BC spectrum (char BC) that is underestimated with the chemothermal oxidation method applied in this study. The sediment profiles of TOC, BC, and PAHs are noticeably different in the mountain lakes located around 2000 m a.s.l. In Lake Engstlen, the PAH/BC ratios, as well as the correlation between PAHs and BC, point towards appreciable amounts of predominantly light soot particles. Light soot particles have higher mobility and can, therefore, be efficiently transported to this remote site. The proglacial Lake Oberaar is shown to be a receptor of BC and PAHs released by the fast melting adjacent glacier acting as a secondary source for these conservative species temporarily stored in the glacier ice. Finally, Lake Stein is in strong contrast to all other lakes. High flux of BC into Lake Stein, combined with constant temporal evolutions of BC and PAHs, and in particular BC/TOC ratios approaching 100% are all strong indications for a geogenic presence of graphite in its catchment area.     

Evaluation of a fluorometric method for measuring low concentrations of ammonia in ambient air

A fluorometric method developed for measuring low concentrations of ammonium in marine and freshwater ecosystems was adapted for the analysis of ammonia in ambient air. The modified method entails collection of samples on an acid-treated solid adsorbent followed by analysis using a fluorometer. Optimal results were obtained using a commercially available sorbent tube containing 100 mg of acid-treated silica gel for sample collection, and an analytical protocol consisting of sample desorption in DI water, addition of orthopthaldialdehyde (OPA) working reagent, and room temperature incubation. Method accuracy and precision were evaluated by comparing experimentally determined quantities of ammonia to expected levels for sample loadings ranging from 0.16 [micro sign]g to 550 [micro sign]g-accuracy was generally within +/-20%. The estimated LOQ for the method is 0.08 [micro sign]g ammonia per sample which represents a 25-375-fold improvement in sensitivity compared to current NIOSH and OSHA methods for the measurement of ammonia in ambient air. The new method should be useful for applications requiring measurement of low concentrations of ammonia using personal sampling equipment or in the characterization of short-term fluctuations of ammonia concentrations in air.     

Study of size and mass distribution of particulate matter due to crop residue burning with seasonal variation in rural area of Punjab, India

Emission from field burning of agricultural crop residue is a common environmental hazard observed in northern India. It has a significant potential health risk for the rural population due to respirable suspended particulate matter (RSPM). A study on eight stage size segregated mass distribution of RSPM was done for 2 wheat and 3 rice crop seasons. The study was undertaken at rural and agricultural sites of Patiala (India) where the RSPM levels remained close to the National Ambient Air quality standards (NAAQS). Fine particulate matter (PM(2.5)) contributed almost 55% to 64% of the RSPM, showing that, in general, the smaller particles dominated during the whole study period with more contribution during the rice crop as compared to that of wheat crop residue burning. Fine particulate matter content in the total RSPM increased with decrease in temperature. Concentration levels of PM(10) and PM(2.5) were higher during the winter months as compared to that in the summer months. Background concentration levels of PM(10), PM(2.5) and PM(10-2.5) were found to be around 97 ± 21, 57 ± 15 and 40 ± 6 μg m(-3), respectively. The levels increased up to 66, 78 and 71% during rice season and 51, 43 and 61% during wheat crop residue burning, respectively. Extensive statistical analysis of the data was done by using pair t-test. Overall results show that the concentration levels of different size particulate matter are greatly affected by agricultural crop residue burning but the total distribution of the particulate matter remains almost constant.