Sardar Khan

Bio: Sardar Khan is an academic researcher from University of Peshawar. The author has contributed to research in topics: Soil contamination & Bioaccumulation. The author has an hindex of 45, co-authored 171 publications receiving 9215 citations. Previous affiliations of Sardar Khan include International Islamic University, Islamabad & Centers for Disease Control and Prevention.

The uptake and bioaccumulation of heavy metals by food plants, their effects on plants nutrients, and associated health risk: a review.

Abstract: Heavy metal contamination is a globally recognized environmental issue, threatening human life very seriously. Increasing population and high demand for food resulted in release of various contaminants into environment that finally contaminate the food chain. Edible plants are the major source of diet, and their contamination with toxic metals may result in catastrophic health hazards. Heavy metals affect the human health directly and/or indirectly; one of the indirect effects is the change in plant nutritional values. Previously, a number of review papers have been published on different aspects of heavy metal contamination. However, no related information is available about the effects of heavy metals on the nutritional status of food plants. This review paper is focused upon heavy metal sources, accumulation, transfer, health risk, and effects on protein, amino acids, carbohydrates, fats, and vitamins in plants. The literature about heavy metals in food plants shows that both leafy and nonleafy vegetables are good accumulators of heavy metals. In nonleafy vegetables, the bioaccumulation pattern was leaf > root ≈ stem > tuber. Heavy metals have strong influence on nutritional values; therefore, plants grown on metal-contaminated soil were nutrient deficient and consumption of such vegetables may lead to nutritional deficiency in the population particularly living in developing countries which are already facing the malnutrition problems.

Sewage sludge biochar influence upon rice (Oryza sativa L) yield, metal bioaccumulation and greenhouse gas emissions from acidic paddy soil

Abstract: Biochar addition to soil has been proposed to improve plant growth by increasing soil fertility, minimizing bioaccumulation of toxic metal(liod)s and mitigating climate change. Sewage sludge (SS) is an attractive, though potentially problematic, feedstock of biochar. It is attractive because of its large abundance; however, it contains elevated concentrations of metal(loid)s and other contaminants. The pyrolysis of SS to biochar (SSBC) may be a way to reduce the availability of these contaminants to the soil and plants. Using rice plant pot experiments, we investigated the influence of SSBC upon biomass yield, bioaccumulation of nutrients, and metal(loid)s, and green housegas (GHG) emissions. SSBC amendments increased soil pH, total nitrogen, soil organic carbon and available nutrients and decreased bioavailable As, Cr, Co, Ni, and Pb (but not Cd, Cu, and Zn). Regarding rice plant properties, SSBC amendments significantly (P ≤ 0.01) increased shoot biomass (71.3-92.2%), grain yield (148.8-175.1%), and the bioaccumulation of phosphorus and sodium, though decreased the bioaccumulation of nitrogen (except in grain) and potassium. Amendments of SSBC significantly (P ≤ 0.05) reduced the bioaccumulation of As, Cr, Co, Cu, Ni, and Pb, but increased that of Cd and Zn, though not above limits set by Chinese regulations. Finally regarding GHG emissions, SSBC significantly (P < 0.01) reduced N2O emissions and stimulated the uptake/oxidation of CH4 enough to make both the cultivated and uncultivated paddy soil a CH4 sink. SSBC can be beneficial in rice paddy soil but the actual associated benefits will depend on site-specific conditions and source of SS; long-term effects remain a further unknown.

Heavy Metals in Contaminated Soils: A Review of Sources, Chemistry, Risks and Best Available Strategies for Remediation

Abstract: Scattered literature is harnessed to critically review the possible sources, chemistry, potential biohazards and best available remedial strategies for a number of heavy metals (lead, chromium, arsenic, zinc, cadmium, copper, mercury and nickel) commonly found in contaminated soils. The principles, advantages and disadvantages of immobilization, soil washing and phytoremediation techniques which are frequently listed among the best demonstrated available technologies for cleaning up heavy metal contaminated sites are presented. Remediation of heavy metal contaminated soils is necessary to reduce the associated risks, make the land resource available for agricultural production, enhance food security and scale down land tenure problems arising from changes in the land use pattern.

Soil Contamination in China: Current Status and Mitigation Strategies

Abstract: China faces great challenges in protecting its soil from contamination caused by rapid industrialization and urbanization over the last three decades. Recent nationwide surveys show that 16% of the soil samples, 19% for the agricultural soils, are contaminated based on China’s soil environmental quality limits, mainly with heavy metals and metalloids. Comparisons with other regions of the world show that the current status of soil contamination, based on the total contaminant concentrations, is not worse in China. However, the concentrations of some heavy metals in Chinese soils appear to be increasing at much greater rates. Exceedance of the contaminant limits in food crops is widespread in some areas, especially southern China, due to elevated inputs of contaminants, acidic nature of the soil and crop species or cultivars prone to heavy metal accumulation. Minimizing the transfer of contaminants from soil to the food chain is a top priority. A number of options are proposed, including identification of the sources of contaminants to agricultural systems, minimization of contaminant inputs, reduction of heavy metal phytoavailability in soil with liming or other immobilizing materials, selection and breeding of low accumulating crop cultivars, adoption of appropriate water and fertilizer management, bioremediation, and change of land use to grow nonfood crops. Implementation of these strategies requires not only technological advances, but also social-economic evaluation and effective enforcement of environmental protection law.