Plant Gardens 101

Although lead naturally exists on Earth, lead concentrations in the environment have been increasing for several centuries due to human activities including mining and smelting of ores, the combustion of fossil fuels, and the dissemination of lead through industrial processes. Lead has no known essential role in biological sphere serious environmental effects can result from high level of atmospheric lead fallout, leading to detrimental changes in ecosystem and community function. Lead bioaccumulates in plant material and consequently its concentration can be magnified in food chains. Serious toxicological effects can results from high level of lead fallout. Vehicular emission is of concern particularly in urban environment that has low assimilative capacity. The emissions react forming various species in various meteorological conditions interfering with man’s activities. To counter some of these effects like fog and breathing excessive amounts of these gases, researchers are trying to discover new sources of energy and power. There are now vehicles run entirely on natural gas as opposed to petrol. Vehicular emission in typical urban centre constitute over 60% of total pollutant emission compared to industry, power plants, space heating, refuse disposal etc. Hydrocarbons and nitrogen dioxide emitted principally from automobiles are the major ingredients of photochemical smog. This is evidence by the prevalence of smog problems in most down town areas of developed countries. Sizeable quantities of poisons such as aldehyde, lead, etc are also emitted by automobiles. Lead consumption as a gasoline additive peaked during 1970’s in the United States (USBM 1966-1989). After the U.S. congress passed legislation restricting the sale of gasoline with alkyl-lead additives, the amount of lead consumed in gasoline has declined sharply, resulting in lower rates of atmospheric lead deposition. As one of the most persistent metals, lead was estimated to have a soil retention time from 150 to 5000 years. Lead, one of the most important environmental pollutants, has limited availability for plant uptake due to complexation with organic matter and precipitation as carbonates, hydroxides and phosphates. They could get into plants through root systems, and unusual high concentration of heavy metal in plants usually has bad influence on plant growth. However in our ecosystem, there are lots of plants acting as lead accumulator. And sometimes even though there are extremely high concentrations of lead in the soil, the concentration in the plants could be extremely low. But there are also some species which has a linear relationship between the soil lead concentration and the lead concentration in themselves. So they could be used as an indicator of the ecosystem health. And being at the bottom of many natural food chains, metal accumulating plants are directly and indirectly responsible for a large proportion of the dietary uptake of lead by humans and animals. Other sources of lead are mining, smelting, printing, lead paint, flacks, sewage sludge and the use of pesticide containing lead compounds. However these sources account to a little extent. Urban environments in general have received higher depositions of lead from vehicular emissions than have rural areas. A number of studies have been carried out to determine the lead concentration in dust, dirt, particulates and leaf samples in different urban areas around the world. And in our research, we also try to compare the lead contents of soil and plant in this roadside with dense vehicular traffic.

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