Atmospheric polycyclic aromatic hydrocarbons (PAHs) at urban settings in Pakistan: Spatial variations, sources and health risks.

For the first time, this study presents gaseous and particulate-bound (PM2.5) polycyclic aromatic hydrocarbons (PAHs) in ambient air samples collected from eight major cities of Pakistan. Diurnal air samples (gaseous and PM2.5) were collected in summer 2014 on polyurethane foam and quartz fiber filters using high volume-active air sampler. The US-EPA enlisted 16 priority PAHs in particulate and gaseous phase were measured on gas chromatograph equipped with mass spectrometer detector. The total PAHs concentrations ranged between 188 pg m-3 (in Gilgit), and 2340 pg m-3 (in Lahore). The decreasing order of PAHs concentrations in various cities was in the following order: Lahore > Rawalpindi > Multan > Faisalabad > Karachgi > Peshawar > Quetta > Gilgit. Phenanthrene showed the highest concentration, accounted 18% of total PAHs followed by fluoranthene (12% of total PAHs). This study showed that the gaseous fractions were predominant in the ambient air. Source apportionment analysis revealed that biomass combustion, vehicular emissions and diesel combustion in power generators were the potential PAHs emissions sources. The lifetime lungs cancer risk (LLCR) was in the range of 8.28 × 10-7 to 2.09 × 10-5 depicting mild cancer risk to the residents on exposure to atmospheric PAHs. Therefore, it is recommended to monitor atmospheric PAHs throughout the year and also adopt environmentally friendly fuels to reduce PAHs pollution and health risks in the country.

Dietary proxies (δ15N, δ13C) as signature of metals and arsenic exposure in birds from aquatic and terrestrial food chains.

In this study, exposure to arsenic (As), lead (Pb), cadmium (Cd), copper (Cu) and zinc (Zn) was investigated in the blood, pectoral muscles and tail feathers of two terrestrial (spotted owlet; Athena brama and bank myna; Acridotheres ginginianus) and two aquatic (cattle egret; Bubulcus ibis and pond heron; Ardeola grayii) bird species inhabiting Pakistan. Food chain specimens, as well as the dietary proxies δ15N and δ13C, were also analyzed to validate potential trophic and dietary transfers of metals and As in birds. Zn was found to be the most prevalent metal in the tissues of birds followed by Pb, As, Cu, and Cd. The bioaccumulation of metals and As was higher in tail feathers reflecting the combined effect of both endogenous and exogenous contamination. Pectoral muscle and blood harbored lower levels of As and metals, indicating less recent exposure through diet. Aquatic birds feeding at higher trophic levels accumulated significantly higher concentrations of metals and As in their tissues (P < 0.05) and, therefore, may be at a greater risk of metal and As toxicity than terrestrial birds. Linear regression model depicts δ15N as a strong predictor of metals and As levels in the tissues of both aquatic and terrestrial birds, followed by the δ13C dietary proxy. All metals in aquatic species, except for Cd, as well as terrestrial species, except for Cu, exhibit bioaccumulative potential through the food chain (Trophic transfer factor: TTFs > 1) indicating potential harmful consequences for birds. Elevated concentrations of metals and As in tissues may cause harmful effects in birds potentially leading to declines in their populations.

Significance of black carbon in the sediment-water partitioning of organochlorine pesticides (OCPs) in the Indus River, Pakistan.

This study was conducted with the aim of assessing the levels and black carbon mediated sediment-water partitioning of organochlorine pesticides (OCPs) from the Indus River. ∑OCPs ranged between 52-285 ng L(-1) and 5.6-29.2 ng g(-1) in water and sediment samples respectively. However, the ranges of sedimentary fraction of total organic carbon (f(TOC)) and black carbon (f(BC)) were 0.82-2.26% and 0.04-0.5% respectively. Spatially, OCPs concentrations were higher at upstream sites as compared to downstream sites. Source diagnostic ratios indicated the technical usage of HCH (α-HCH/γ-HCH>4) and significant presence of DDT metabolites with fresh inputs into the Indus River as indicated by the ratios of (DDE+DDD)/∑DDTs (0.27-0.96). The partitioning of OCPs between the sediments and water can be explained by two carbon Freundlich adsorption model which included both organic carbon and black carbon pools as partitioning media.