Ranu Gadi

Levels, Sources, and Toxic Potential of Polycyclic Aromatic Hydrocarbons in Urban Soil of Delhi, India

ABSTRACT This study was done to determine the concentration of PAHs in urban soil of Delhi (India). Surface top soil (up to 10 cm depth) samples were collected from four different sampling sites including industrial, roadside, residential, and agricultural areas of Delhi and 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) were evaluated. Total PAH concentrations at industrial, roadside, residential, and agricultural sites were 11.46 ± 8.39, 6.96 ± 4.82, 2.12 ± 1.12, and 1.55 ± 1.07 mg/kg (dry weight), respectively, with 3–7 times greater concentrations in industrial and roadside soils than that in residential and agricultural soils. The PAH pattern was dominated by 4- and 5-ring PAHs (contributing >50% to the total PAHs) at industrial and roadside sites with greater concentration of fluoranthene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]anthracene, benzo[ghi]perylene, and pyrene, whereas, residential and agricultural sites showed a predominance of low molecular weight 2- and 3-ring PAHs (fluoranthene, acenaphthene, naphthalene, chrysene, and anthracene). Isomeric pair ratios suggested biomass combustion and fossil fuel emissions as the main sources of PAHs. The toxic equivalency factors (TEFs) showed that carcinogenic potency (benzo[a]pyrene-equivalent concentration (B[a]Peq) of PAH load in industrial and roadside soils was ∼10 and ∼6 times greater than the agricultural soil.

Emissions of Polycyclic Aromatic Hydrocarbons in the Atmosphere: An Indian Perspective

ABSTRACT Organic compounds form a major fraction of airborne particles in the atmosphere and hence it is important to measure and identify them, especially the proportion of Polycyclic (Polynuclear) Aromatic Hydrocarbons (PAHs). The control and abatement of PAHs contamination requires the knowledge of the nature, source, and extent of pollution and hence existing literature on Indian studies was reviewed to gather information on the sources and emission rates of PAHs. Based on the results of the present study along with the data available from literature for particular PAHs in the ambient atmosphere, the vehicular and residential sector was identified as a major source of PAHs emission in many major Indian cities including Ahmedabad, Agra, Delhi, Kanpur, Lucknow, Mumbai, and Nagpur. Emissions of total PAHs range from 23–190 ng/m3, 369–1067 ng/m3, 20.8–100.8 ng/m3, and 12.7–206.4 μg/m3 from gasoline, diesel, petroleum refinery, and biomass, respectively, although it is recognized that this will vary from location to location. Additionally, the regulation and control of PAHs emission, and air quality standards for PAHs were also examined. Based on the toxicity assessment, the study highlights the need to include not only benzo[a]pyrene but also other probable human carcinogenic PAHs while developing a new air quality index for India.

Characterization of Gaseous and Particulate Polycyclic Aromatic Hydrocarbons in Ambient Air of Delhi, India

Three seasonal sampling campaigns were undertaken at an urban site of Delhi for collection of PAHs in particulate and gas phase. Sampling was done by using modified Respirable Dust (PM ≤10μm) sampler attached with polyurethane foam (PUF) plugs and compared with conventional Respirable Dust (PM ≤10 μm) sampler. Total 16 EPA PAH (gaseous + particulate) were determined by Gas Chromatograph-Mass Spectrophotometer (GC-MS). The 3-ring PAH constitutes approximately 90% of the gaseous PAHs with phenanthrene, fluoranthene, acenapthylene, and acenaphthene being the most abundant gaseous PAHs. PAHs with 4- to 6- rings accounted for 92%, 87% and 78% in samples collected during winter, summer and monsoon season respectively. Gaseous PAHs, particulate PAHs and total PAHs were higher during winter as compared to summer and monsoon seasons. The contribution of particulate PAHs were 1.4, 2.1, and 2.5 times higher in winter, summer and monsoon, respectively than of gaseous PAHs. Indeno[123-cd]pyrene, benzo[ghi]perylene, dibenzo[ah]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene and chrysene were found to be the most abundant PAH compounds in the particulate PAHs during all the seasons. The result from application of diagnostic ratio suggests that the higher particulate PAHs emissions were predominantly associated with vehicular emissions along with emissions from biomass burning during winter season.

Biological methods for speciation of heavy metals: different approaches

Heavy metals are found in their different forms in the environment. The distribution, mobility, and toxicity of metals are strongly related to these different forms. This necessitates the exploration of different methods for the remediation and speciation of heavy metals. Some direct and indirect physico-chemical methods such as filtration, chemical precipitation, ion-exchange, electro deposition, and membrane systems have been used for the last four decades. However, it is only in last few years that reliable biological methods have also been used. The biological methods include the use of microorganisms (fungi, algae, bacteria), plants (live or dead) and biopolymers. The use of these methods for the speciation of heavy metals is reviewed here.

Removal of Ni (II) and Cu (II) from their Solutions and Waste Water by Nonliving Biomass of Pseudomonas oleovorans

The nonliving biomass of Pseudomonas oleovorans was used for the removal of Nickel and Copper from their single and binary solutions. The optimum conditions such as pH, initial metal ion concentration, contact time and biomass dose were determined experimentally. q max and ‘b’ values for Ni(II) were 95.6 mg/g and 0.010 and for Cu(II) 137.5 mg/g and 0.008 respectively. The removal of the metals was studied in binary metal systems also. The developed method was applied for the removal of the metals from the wastewater samples. The investigations on the speciation of the metals revealed that both Ni and Cu exist as hydrated Ni (II) and Cu (II) ions and precipitates of Ni(OH) 2 and Cu(OH) 2 at different pH ranges.