Erum Zahir

Heavy metal toxicity levels in the coastal sediments of the Arabian Sea along the urban Karachi (Pakistan) region

Heavy metals are stable and persistent environmental contam-inants since they cannot be degraded or destroyed. Therefore, theytend to accumulate in the soils and sediments. Excessive levels ofmetals in sediments affect marine biota and pose a risk to humanhealth through the consumption of seafood (Adams et al., 1992;Rowlatt and Lovell, 1994; Mucha et al., 2003; Feng et al., 2004;Zhang et al., 2007). The main anthropogenic sources of heavy met-als are various industrial point sources, including present and for-mer mining activities, foundries and smelters, and diffuse sourcessuch as piping, combustion by-products, traffic, etc. (NRC, 1989;Bryan and Langston, 1992; Long, 2000; Pekey, 2006; Hyun et al.,2007). Relatively volatile heavy metals and those that become at-tached to air-borne particles can be widely dispersed on very largescales. Heavy metals in aqueous and sedimentary transport (e.g.,river run-off) enter the normal coastal biogeochemical cycle andare largely retained within near-shore and shelf regions in propor-tion to geochemical controls (McAlister et al., 2005; Chaparro et al.,2005). Sediment analyses play a crucial role in assessing the degreeof heavy metal pollution and the resulting health risk associatedwith the food chain.Karachi is situated at the southern most part of Pakistan alongthe Arabian Sea and it is the largest business hub and the mostheavily populated urban centre in the vicinity. The coastal zoneof Karachi is about 167 km long. The estimated population of Kar-achiis morethan15 million.The rapidindustrializationandurban-ization of the city has altered the quality of the environment andcreated ecological disturbances and associated problems for the lo-cal community. Pollution in the Karachi coastal region is mainlyattributed to the Lyari and Malir rivers, which are served by vari-ous channels of untreated domestic and industrial waste, carryingmore than 300 million gallons per day (MGD) (1,125,000 m

Aflatoxins in composite spices collected from local markets of Karachi, Pakistan

ABSTRACT This survey was carried out to evaluate the occurrence of total aflatoxins (AFs; B1+B2+G1+G2) in unpacked composite spices. A total of 75 samples of composite spices such as biryani, karhai, tikka, nihari and korma masalas were collected from local markets of Karachi, Pakistan, and analysed using HPLC technique. The results indicated that AFs were detected in 77% (n = 58) samples ranging from 0.68 to 25.74 µg kg−1 with a mean of 4.63 ± 0.95 µg kg−1. In 88% (n = 66) samples, AFs level was below the maximum limits (ML = 10 µg kg−1) as imposed by EU. Furthermore, 61% (n = 46) tested samples contained AFs level between 1 and 10 µg kg−1, 9% (n = 7) exhibited AFs contamination ranged 10−20 µg kg−1 and only 3% (n = 2) of the investigated samples contained AFs levels higher than the ML of 20 µg kg−1 for total aflatoxins as set by the USA. It was concluded that there is need to establish a strict and continuous national monitoring plan to improve safety and quality of spices in Pakistan.

Thermodynamic studies of iron chelation with doxycycline in acidic medium

Doxycycline (DOX) is a broad-spectrum tetracycline antibiotic synthetically derived from oxytetracycline. The complex formation of this drug with iron(III) was studied using spectrophotometry. The thermodynamic parameters of the systems were calculated using the changes in the absorption spectra which occur due to hydrogen bond or complex formation. Thermodynamic parameters of the formation of iron(III) complex with doxycycline (ΔH, ΔG, ΔS, and stability constants) were determined spectrophotometrically at a wavelength corresponding to absorption maximum (374.5 nm) at three different temperatures (22, 35, and 45°C). The obtained data show that the complex has metal to ligand molar ratio of 1: 2 at pH 2–3. The stability constants were calculated to be 13.99 × 106, 7.06 × 105, and 1.29 × 106 by mole ratio method at 22, 35, and 45°C, respectively.

Comparative study of raw and chemically treated mangrove leaf for remediation of 304 Methyl Violet 2B dye from aqueous solution: thermo-kinetics aspect

The adsorption process is the most attractive alternative way for the treatment of industrial effluents. The main objective of the study is to compare the efficacy of adsorption by raw and chemically treated forms of mangrove plant leaf powder. It acts as adsorbent, and would not only be economical but also help to reduce pollution. The adsorbent was characterized by Fourier transform infra-red spectroscopy and scanning electron microscopy. Results showed that percent removal of dye was higher by chemically treated mangrove leaf (98%) than by raw mangrove leaf (75%) under all determined conditions. The equilibrium and kinetics adsorption data were analyzed by the Langmuir isotherm and the pseudo second order model. They were found to be the best fit to interpret the present data. The thermodynamic parameters were calculated by using the Langmuir equilibrium constant. Results suggested that dye adsorption on mangrove leaf was a spontaneous and exothermic process with enthalpy change = -15.26 kJ/mol, and there was decrease in disorder with entropy change = -5.089 kJ/mol K.

Kinetic and Thermodynamic Studies of Antioxidant and Antimicrobial Activities of Essential Oil of Lavendula steochs

Antioxidant, antimicrobial activities of essential oil from plant Lavendula steochs were studies by kinetics and thermodynamic approach. Hydro-distillation was used for the extraction of oil from the flowers of Lavendula steochs . - Antioxidant activity was performed using DPPH method, in which the IC 50 showed that essential oil has good antioxidant activity. Antimicrobial activity has been analyzed against Methicillin-resistant Staphlococcus aureus (MRSA) and Vancomycin-resistant Staphlococcus aureus (VRSA) which shows that Lavendula steochs is found to be effective against MRSA and VRSA. Chemical composition of essential oils were measured by GC-MS and FT-IR techniques and the kinetic & thermodynamic parameters were used for the characterization of essential oils.