Lead in Plants and the Environment

Abstract

Lead (Pb) is a metal utilized by humans for many thousands of years. Metallic Pb globules manufactured in 6400 BC were discovered at Çatalhöyük (presently in Republic of Turkey). Pb is a bluish-white lustrous metal, which is very soft, highly malleable, and ductile, and is a relatively poor electric conductor. Metal is resistant to corrosion but tarnishes upon exposure to air. In nature, it is typically found as minerals, in combination with other elements. A total of 49 isotopes of Pb were recorded till date with four stable isotopes (204,206,207,208 Pb). Among the stable isotopes, only 204 Pb is a primordial nuclide, and not a radiogenic one. The three other stable isotopes, 206,207,208 Pb, are the endpoints of three decay chains, i.e., uranium, actinium, and thorium series, respectively. 205 Pb and 202 Pb are the longest-lived radioisotopes with a half-life of approximately 15.3 million years and 53,000 years, respectively. The radiologically most relevant radioactive nuclide 210 Pb is part of the 238 U series and has a half-life of 22.3 years. 210 Pb is suitable for studying the chronology of sedimentation on time scales shorter than 100 years. Anthropogenic activities, like combustion of coal, are one of the major sources of 210 Pb in the atmosphere, but 210 Pb also occurs naturally since it is a progeny of the radioactive noble gas radon (222 Rn) emanating from soil air due to the omnipresent uranium. Pb is a microelement with no known physiological function but found in trace amounts in all biotic resources, e.g., in soil, water, plants, and animals. Pb is a toxic element, pollution of which may come from various sources. In the environment, nearly 98% of stable Pb originates from paints, petrochemicals, pipes and supply systems, etc. Routes of Pb poisoning may be through consumption of contaminated food and water, breathing contaminated air from cigars and automobile exhausts, and using uncleaned adulterated hands/face where individual health and hygiene issues are compromised. However, usually, Pb is not absorbed through skin. Recent extensive work on 210 Pb radioisotope for examining plant uptake, where, mostly, artificial spiking of the metal in the soil and observing its consequent absorp- tion in plant and soils. Usually, Pb forms complexes with soil particles, and a very small amount or fractions are easily available for plants. Despite its lack of essential function in plants, Pb is taken up mostly through the roots from soil solutions at ronment and its translocation from soil to plants and into the food chain. Chapters 1 and 2 deal with the analytical methods for determining Pb both in environmental and in biological samples and also the effect of radioisotopic lead behavior in plants and environment and distribution of radioactive Pb and its distribution in environ- ment through modelling application. Chapters 3 and 4 focus on Pb exposure to humans via agroecosystem and its consequences. Chapters 5 and 6 focus on how Pb behaves in soil plant system and how it uptakes in plants. Chapters 7 and 8 empha- size on how Pb reacts on physiological and biochemical changes in plants with reference to different plant enzymes and photosynthetic apparatus. Last but not least, Chaps. 9 and 10 present the biological strategies of lichens symbionts, under Pb toxicity, and how Pb pollution is going to remediate via phytoremediation. The material composed in this volume will bring in-depth holistic information on Pb (both stable and radioactive) uptake and translocation and its toxicity in plants and effect on human health and phytoremediation strategies.