Mohammad Tahir Shah

Did the Kohistan-Ladakh island arc collide first with India?

The Kohistan-Ladakh block occupies the northwestern corner of the Himalayan mountains and has long been recognized to represent an island arc constructed on ocean floor during Jurassic and Cretaceous times. Because the Kohistan-Ladakh block now lies within the Asian continent, it is important to know how and when it became sandwiched between India and the rest of Asia. We have found from analysis of paleomagnetic data that in Late Cretaceous–early Paleocene times, the Kohistan-Ladakh island arc could not have been far from the equator. India was close to the equator, but the southern margin of Asia was more than 3000 km to the north. Our new U-Pb zircon age results from rocks of the Kohistan-Ladakh block show that calc-alkaline volcanic arc igneous activity ended in the Kohistan-Ladakh arc by 61 Ma. We interpret that cessation to date the collision of Kohistan with India. This new timing is confirmed by evidence that a Southern Hemisphere enriched DUPAL mantle source was involved in the generation of the latest Cretaceous Teru Volcanic Formation rocks of the Kohistan-Ladakh arc. Further confirmation of the collision of the Kohistan arc with India in early Paleocene times comes from evidence of the timing of obduction of ophiolites and from the unconformity of postcollisional sedimentary rocks onto the Indian continental margin in northwestern and western Pakistan. Final incorporation of India, now carrying the Kohistan-Ladakh block in its NW corner, into Asia took place at the Shyok suture. The best evidence for the timing of that suturing ca. 50 Ma comes from two postcollisional granites (ages 47 Ma and 41 Ma) in northern Kohistan, which show in their zircon isotopic compositions evidence of the involvement of ancient Asian continental crust that did not exist under Kohistan before the suture formed. The 50 Ma age for Shyok suturing against the then-active Karakoram Andean arc fits well with the extension of the suture beyond the eastern end of the Kohistan-Ladakh block to join the precisely dated ca. 51 Ma Yarlung–Tsang Po suture between India and the southern (Lhasa block) margin of Tibet, which at that time was also occupied by an Andean arc, the Gangdese arc.

Quantification of inorganic arsenic exposure and cancer risk via consumption of vegetables in southern selected districts of Pakistan

Human exposures to arsenic (As) through different pathways (dietary and non-dietary) are considered to be one of the primary worldwide environmental health risks to humans. This study was conducted to investigate the presence of As in soil and vegetable samples collected from agricultural lands located in selected southern districts of Khyber Pakhtunkhwa (KPK) Province, Pakistan. We examined the concentrations of total arsenic (TAs), organic species of As such as monomethylarsonic acid (MMA) and dimethylarsonic acid (DMA), and inorganic species including arsenite (AsIII) and arsenate (AsV) in both soil and vegetables. The data were used to determine several parameters to evaluate human health risk, including bioconcentration factor (BCF) from soil to plant, average daily intake (ADI), health risk index (HRI), incremental lifetime cancer risk (ILTCR), and hazard quotient (HQ). The total As concentration in soil samples of the five districts ranged from 3.0-3.9mgkg(-1), exhibiting minimal variations from site to site. The mean As concentration in edible portions of vegetable samples ranged from 0.03-1.38mgkg(-1). It was observed that As concentrations in 75% of the vegetable samples exceeded the safe maximum allowable limit (0.1mgkg(-1)) set by WHO/FAO. The highest value of ADI for As was measured for Momordica charantia, while the lowest was for Allium chinense. The results of this study revealed minimal health risk (HI<1) associated with consumption of vegetables for the local inhabitants. The ILTCR values for inorganic As indicated a minimal potential cancer risk through ingestion of vegetables. In addition, the HQ values for total As were <1, indicating minimal non-cancer risk.

Arsenic and Heavy Metal Concentrations in Drinking Water in Pakistan and Risk Assessment: A Case Study

ABSTRACT The present study was performed to assess drinking water quality and potential health risk in the Nowshera District, Khyber Pakhtunkhwa, Pakistan. For this purpose drinking water samples were collected from local available sources and analyzed for physico-chemical characteristics, arsenic (As) and heavy metals. Results revealed high levels of toxic heavy metals such as chromium (Cr), nickel (Ni), lead (Pb), cadmium (Cd), and As contaminations in the drinking water. Results were evaluated for chronic risk including average daily intake (ADI) and hazard quotient (HQ). Among heavy metals the HQ values were highest for Cd (5.80) and As (2.00). Therefore, populations in the study area may be at a low level of chronic toxicity and carcinogenic risk. Statistical analyses showed that contribution of different drinking water sources to the mean contaminant levels in the study area was insignificant (p =.53). Correlation analysis further revealed that anthropogenic activities were the main sources of contamination, rather than geogenic. This study strongly recommends the treatment of urban and industrial wastewater in the vicinity of the study area and provision of safe drinking water.

Quantification of Heavy Metals in Mining Affected Soil and Their Bioaccumulation in Native Plant Species

Several anthropogenic and natural sources are considered as the primary sources of toxic metals in the environment. The current study investigates the level of heavy metals contamination in the flora associated with serpentine soil along the Mafic and Ultramafic rocks northern-Pakistan. Soil and wild native plant species were collected from chromites mining affected areas and analyzed for heavy metals (Cr, Ni, Fe, Mn, Co, Cu and Zn) using atomic absorption spectrometer (AAS-PEA-700). The heavy metal concentrations were significantly (p < 0.01) higher in mine affected soil as compared to reference soil, however Cr and Ni exceeded maximum allowable limit (250 and 60 mg kg−1, respectively) set by SEPA for soil. Inter-metal correlations between soil, roots and shoots showed that the sources of contamination of heavy metals were mainly associated with chromites mining. All the plant species accumulated significantly higher concentrations of heavy metals as compared to reference plant. The open dumping of mine wastes can create serious problems (food crops and drinking water contamination with heavy metals) for local community of the study area. The native wild plant species (Nepeta cataria, Impatiens bicolor royle, Tegetis minuta) growing on mining affected sites may be used for soil reclamation contaminated with heavy metals.

Wild Plant Assessment for Heavy Metal Phytoremediation Potential along the Mafic and Ultramafic Terrain in Northern Pakistan

This study investigates the wild plant species for their phytoremediation potential of macro and trace metals (MTM). For this purpose, soil and wild plant species samples were collected along mafic and ultramafic terrain in the Jijal, Dubair, and Alpuri areas of Kohistan region, northern Pakistan. These samples were analyzed for the concentrations of MTM (Na, K, Ca, Mg, Fe, Mn, Pb, Zn, Cd, Cu, Cr, Ni, and Co) using atomic absorption spectrometer (AAS-PEA-700). Soil showed significant (P < .001) contamination level, while plants had greater variability in metal uptake from the contaminated sites. Plant species such as Selaginella jacquemontii, Rumex hastatus, and Plectranthus rugosus showed multifold enrichment factor (EF) of Fe, Mn, Cr, Ni, and Co as compared to background area. Results revealed that these wild plant species have the ability to uptake and accumulate higher metals concentration. Therefore, these plant species may be used for phytoremediation of metals contaminated soil. However, higher MTM concentrations in the wild plant species could cause environmental hazards in the study area, as selected metals (Fe, Mn, Cr, Ni, Co, and Pb) have toxicological concerns.

Lead and cadmium contamination and exposure risk assessment via consumption of vegetables grown in agricultural soils of five-selected regions of Pakistan

Rapid urbanization and industrialization result in serious contamination of soil with toxic metals such as lead (Pb) and cadmium (Cd), which can lead to deleterious health impacts in the exposed population. This study aimed to investigate Pb and Cd contamination in agricultural soils and vegetables in five different agricultural sites in Pakistan. The metal transfer from soil-to-plant, average daily intake of metals, and health risk index (HRI) were also characterized. The Pb concentrations for all soils were below the maximum allowable limits (MAL 350 mg kg-1) set by State Environmental Protection Administration of China (SEPA), for soils in China, while Cd concentrations in the soils were exceeded the MAL (61.7-73.7% and 4.39-34.3%) set by SEPA (0.6 mg kg-), and European Union, (1.5 mg kg-1) respectively. The mean Pb concentration in edible parts of vegetables ranged from 1.8 to 11 mg kg-1. The Pb concentrations for leafy vegetables were higher than the fruiting and pulpy vegetables. The Pb concentrations exceeded the MAL (0.3 mg kg-1) for leafy vegetables and the 0.1 mg kg-1 MAL for fruity and rooty/tuber vegetables set by FAO/WHO-CODEX. Likewise, all vegetables except Pisum sativum (0.12 mg kg-1) contained Cd concentrations that exceeded the MAL set by SEPA. The HRI values for Pb and Cd were <1 for both adults and children for most of the vegetable species except Luffa acutangula, Solanum lycopersicum, Benincasa hispada, Momordi charantia, Aesculantus malvaceae, Cucumis sativus, Praecitrullus fistulosus, Brassica oleracea, and Colocasia esculanta for children. Based on these results, consumption of these Pb and Cd contaminated vegetables poses a potential health risk to the local consumers.

Mineralogy, geochemistry and genesis of the ferromanganese ores from Hazara area, NW Himalayas, northern Pakistan

Abstract Ferromanganese ores occur in Hazara area near Abbottabad within the Hazira Formation of the Kalachitta-Margala thrust belt of the NW Himalayas of the Indo-Pakistan plate in Pakistan. The Hazira formation of Cambrian age is a relatively thin unit (up to 150 m thick), which consists of either thin ferruginous siltstone, with variable amounts of clay, shale, ferromanganese ores, phosphorite and barite, or thicker, evenly bedded, reddish-brown siltstone. It has a conformable lower contact with the Abbottabad Formation (Cambrian) and an unconformable upper contact with the Samana Suk limestone (Jurassic). The ferromanganese ores of the Hazara area were studied in terms of their mineral and geochemical composition. Mineralogically, a variety of Mn and Fe-phases have been noticed in Kakul, Galdanian and Chura Gali ferromanganese ores. Bixbyite is the principal Mn-phase while pyrolusite, hollandite, partridgeite and braunite occur in lesser amounts. Hematite, however, is the only Fe-phase in these ores. Gangue minerals include carbonates, cryptocrystalline quartz, iron-clay and variable amounts of apatite, plumbogummite and barite. Glauconite occurs in traces. Textural features suggest remobilization and subsequent precipitation of early diagenetic Mn and Fe-phases along the fractures and interstices of the gangue minerals during later metamorphism. Chemical analyses show that the Mn/Fe ratio in the ores is highly variable and ranges from 0.46 to 5.25. These ores exhibit a line of descent from LREE to HREE with a small positive Ce anomaly. Their ΣREE is higher than the hydrothermal Mn deposits and lower than the hydrogenous crust. The petrochemical characteristics suggest a mixed hydrothermal-hydrogenetic source for the ferromanganese ores which have formed in shallow water or continental shelf environment due to the upwelling of anoxic deep seated water.

Arsenic and heavy metals contamination, risk assessment and their source in drinking water of the Mardan District, Khyber Pakhtunkhwa, Pakistan.

The present study was conducted to investigate the physico-chemical characteristics in drinking water of Mardan District, Pakistan. Furthermore, water quality was evaluated for the risk assessment of arsenic and heavy metals (HMs) and their contamination sources. Representative groundwater samples of shallow and deep sources were collected in the study area. These samples were analyzed for physical parameters, anions, light metals (LMs) and HMs. Results were compared with the drinking water guideline values set by the World Health Organization and the US Environmental Protection Agency. Average concentrations of anions, LMs and HMs were found within the maximum allowable contaminant levels except for bicarbonates, Fe, Cu, and Pb. Results revealed that hazard quotients >1 were observed for shallow groundwater for 10% samples only, suggesting potential health risk from water consumption. Correlation analysis and principal component analysis showed a relationship among various physico-chemical parameters in both shallow and deep groundwater. Statistical analyses suggested the geogenic and anthropogenic sources for possible enhancement of various physico-chemical parameters in the aquifer system of the study area.

Role of mafic and ultramafic rocks in drinking water quality and its potential health risk assessment, Northern Pakistan

This study investigates the drinking water (groundwater and surface water) quality and potential risk assessment along mafic and ultramafic rocks in the Swat district of Khyber Pakhtunkhwa Provence, Pakistan. For this purpose, 82 groundwater and 33 surface water samples were collected and analyzed for physico-chemical parameters. Results showed that the majority of the physico-chemical parameters were found to be within the drinking water guidelines set by the World Health Organization. However, major cationic metals such as magnesium (Mg), and trace metals (TM) including iron (Fe), manganese (Mn), nickel (Ni), chromium (Cr) and cobalt (Co) showed exceeded concentrations in 13%, 4%, 2%, 20%, 20% and 55% of water samples, respectively. Health risk assessment revealed that the non-carcinogenic effects or hazard quotient values through the oral ingestion pathway of water consumption for the TM (viz., Fe, Cr and Mn) were found to be greater than 1, could result in chronic risk to the exposed population. Results of statistical analyses revealed that mafic and ultramafic rocks are the main sources of metal contamination in drinking water, especially Ni and Cr. Both Ni and Cr have toxic health effects and therefore this study suggests that contaminated sites should be avoided or treated for drinking and domestic purposes.

QUANTIFICATION OF THE HEAVY METALS IN THE AGRICULTURAL SOILS OF MARDAN DISTRICT, KHYBER PAKHTUNKHWA, PAKISTAN

*Soil samples were collected from Mardan district, Khyber Pakhtunkhwa, Pakistan and were analyzed for physico-chemical parameters (pH, EC, SOM), major cations (Na, K, Ca, Mg, Fe, Mn) and heavy metals (Cu, Pb, Zn, Ni, Cr, Cd, As) concentrations using atomic absorption spectrometer. Based on concentration values, the major cations was found in order of Na> Ca >Fe> K > Mg >Mn. Increasing order of the heavy metal concentrations were as Zn > Cr > Ni > Cu >Pb> As > Cd. The enhanced values of heavy metals in the studied soils could be due to sulfide and mafic minerals in the soils of the study area. Metal concentrations were used to quantify pollution contamination factors (CFs) and pollution load index (PLI). It can be concluded from this classification that soils of the study area are polluted with some of the heavy metals.