Soil, lead anthropogenic activity

Thanks to the movement of water and the diffusion of dissolved substances different geochemical processes take place in the Earth s crust. To a great extent they are responsible for the redistribution of chemical elements in soil and further on to the biosphere. The anthropogenic activity leads to disposal of a lot of wastes to water basins which slowly accumulate in the oceans. This is one of the reasons that makes the determination of metals and toxic elements in water as one of the important tasks in environmental pollution control. 

The last two forms include up to 2% of the total metal content but they are considered as most important for plant nutrition. Until recently in agrochemical, nutrient and ecological investigations attention has been paid mostly to these two forms and analysis has been performed after extraction with water, buffer solutions or other weak extraction media. However the anthropogenic activity leads among other things to increase in soil pH. The result is slow transition from the silicate to the aluminium buffer region where heavy and toxic metals are released from the minerals. Therefore it is very useful to know more about the content of soils than the usual available quantities. 

Natural emissions include lead released from volcanoes, seawater sprays, forest fires, and wind-bome soil particles in remote areas. These releases are typically to the atmosphere and are set forth in Table 4.2. Cumulative atmospheric releases in the natural source category average 19,000 MT/year and a median of 12,000 MT/year (Nriagu, 1989). It should be noted that one has to distinguish between tme natural sources and emissions and those which are more inclusive, i.e., background lead estimates. Such background levels can represent releases to the atmosphere and subsequent deposition of reentrained dusts contaminated with lead from past anthropogenic activities. 

Anthropogenic activities involved in the production, distribution, consumption, and disposal of lead and lead products produce estimates of lead emissions that are many times the amount assigned to natural emission rates. The rates in prior years would have been higher and the ratios of anthropogenic to natural emissions are much higher, but the retention of those past emissions in soil and sediment environmental compartments means that the amounts of anthropogenic lead in the human and ecological environments... 

Soils can have characteristics due to human activity (anthropogenic soils). The forensic examination of soil is therefore not only concerned with the analysis of naturally occurring rocks, minerals, plant, and animal matter it also includes the detection of such manufactured materials as ions from synthetic fertilizers and from different environments (e.g., nitrate, phosphate, sulfate) and environmental artifacts (e.g., lead or objects such as glass, paint chips, asphalt, brick fragments, and cinders). Each of these materials can represent distinct soil characteristics. When unique particles are found in soil evidence, more precise and rapid discrimination can be achieved even if the amount of evidence recovered is microscopic (Sugita and Marumo 2004). For this reason, microscopy is often considered the most useful technique for the detection of such characteristic particles. 

Figures 6.3 and 6.4 show preindustrial and present-day circulation of S in earth s surface environment. Sulfur supply to the atmosphere by industrial activities (e.g., burning of fossil fuels, smelting) is 113 x lO g year that is about eight times of flux by volcanism (14 x lO g year" ) (Kimura 1989). Riverine sulfur flux to ocean is 208 x lO g year. A half of this flux is considered to be of anthropogenic source (Holland 1978). Sulfur in environment (atmosphere, river water) is the element that is significantly affected by human activity, the greatest among elements. According to previous estimates most of sulfur in acid rain transfer to river water. However, acid rain containing sulfur reacts with soil and evaporite, leading to the formation of sulfate minerals and fixation of sulfur in soil. If we take into accotmt the amount of sulfur fixation as sulfates in soil, previously obtained...

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