Sources of lead in soil

Sources of lead in soils and uptake by plants Lower Guadiana River basin, south Portugal and Spain... 

Gulson BL, Davis JJ, Mixon KJ, Dorsch MJ and Bawden-Smith j (1995) Sources of lead in soil and dust and the use of dust fallout as a sampling medium. Sci Total Environ 166 245-262. 

Gulson BL, Davis JJ, Mizon KJ et al (1995a) Sources of lead in soil and dust and the use of dust fallout as a sampling medium. Sci Total Environ 166 245-262 Gulson BL, Mahaffey KR, Mizon KJ et al (1995b) Contribution of tissue lead to blood lead in adult female subjects based on stable lead isotope methods. J Lab Clin Med 125 703-712 Hageman KJ, Simonich SL, Campbell DH et al (2006) Atmospheric deposition of current-use and historic-use pesticides in snow at national parks in the western United States. Environ Sci Technol 40 3174-3180... 

Sources of lead in dust and soil include lead that falls to the ground from the air, and weathering and chipping of lead-based paint from buildings and other structures. Lead in dust may also come from windblown soil. Disposal of lead in municipal and hazardous waste dump sites may also add lead to soil. Mining wastes that have been used for sandlots, driveways, and roadbeds can also be sources of lead. 

The primary source of lead in the environment has historically been anthropogenic emissions to the atmosphere. In 1984, combustion of leaded gasoline was responsible for approximately 90% of all anthropogenic lead emissions. EPA phased out the use of lead alkyls in gasoline, however, and by 1990, auto emissions accounted for only 33% of the annual lead emissions (EPA 1996h). Use of lead additives in motor fuels was totally banned after December 31, 1995 (EPA 1996f). The ban went into effect on February 2, 1996. Atmospheric deposition is the largest source of lead found in soils. Lead is transferred... 

A.J. Friedland Dartmouth College, Hanover, NH Identifying sources and determining mobility of lead in soil, groundwater, and vegetation... 

Lead, particularly from the use of leaded gas in vehicles, is often the more important metal of anthropogenic origin deposited in soils. It is usually retained as coordination complexes because in general, these are not soluble, the transfer of lead from soil to plants is relatively difficult, although in some cases it might be of importance. In Mexico, despite the multiple sources of lead and its importance, the presence of lead in soils has not been adequately studied, as is evident from the following sparse data. 

If the extension of the country is considered, as well as the importance and the number of the sources that might contribute to the levels of lead in soils, it will be evident that the studies described above are altogether insufficient to reach even a preliminary conclusion with regard to the state of lead pollution in soils in the agricultural and other regions of Mexico. 

Since soils are strong accumulators of lead, the analysis of lead in soil is an excellent indicator of accumulated deposition in the vicinity of a source of the metal. In one survey around a secondary smelter [12], concentrations of lead up to 21 000 mg kg" (dry weight) were found in the upper 5 cm of soil adjacent to the smelter with the levels decreasing exponentially with distance from the source. Mean concentrations of lead in soil around the Silver Valley lead smelter [13] (air lead concentrations in Fig. 2.3) are shown in Fig. 4.2. Changes in soil lead between the 1974 and 1975 surveys presumably arise mainly from random errors introduced by minor spatial variability in the lead concentration. 

Lead in soils, dusts and paints represents a potentially highly important source of lead intake.This is especially so for young children who frequently lick and chew contaminated objects. The source of high concentrations of lead in soils and dusts has been discussed previously (Section 4.3). Paints also exhibit high lead concentrations, for instance primers may contain 30 000-600 000 mg kg [5]. Painted surfaces wliich show high concentrations of lead, in particular those that are flaking, are known to result in enhanced lead intake in certain children. A limit of 2500 mg kg is now imposed on lead in paint applied to children s toys, [4] whilst a limit of 5000 mg kg" is applied in the US on paint used for residential surfaces accessible to children [5]. 

Guidelines for soil (see Testing Soil ) suggest that dust above 500 pg/g should be abated. In the context of total exposure to lead fi om all sources, it is possible that a level below 500 pg/g is reasonable to reduce exposure. Based on the assumption that most dust comes fl-om soil and given that the natural concentration of lead in soil is 10-25 pg/g, it is unreasonable to expect household dust levels below this level. When there is no apparent source of dust, typical household dust concentrations are about 100 pg/g. 

The United States Public Health Services drinking water standards specify a 50 mg/1 maximum for lead, EPA [73] has shown that this limit is only infrequently exceeded in larger United States cities. The presence of lead in drinking water may result from the use of lead materials in the water distribution system. Naturally occurring lead in rocks and soils may be an important source of contamination in isolated instances but lead from industrial wastes represent a local and not a widespread problem. The disposition of lead compounds from gasoline is a major source of lead in water systems [73]. 

House dust. Houses are enclosed spaces and tend to accumulate dust from the outside. There are also internal sources of house dust. The concentration ratio [MJhouse dust/[M]soil has a mean of 0.33 (standard deviation = 0.09) for the ten elements Mn, Fe, La, Sm, Hf, Th, V, Al, Sc and Ce suggesting that around 33% of house dust is soil (93). The concentration ratio for the two surface dusts, [M]house dust/[M]street dust is >1 for the elements Cu, Co, As, Sb, Zn, Cd, Au, Cl and C suggesting these elements also have an internal component. All of these elements, as well as Pb and Br, are enriched in house dust relative to their concentrations in soil. Lead and bromine originate mainly from outside the house, and probably from street dust and motor vehicle emissions and, in the case of lead, from paint. When the concentrations of lead in house dust are very high this generally signifies an internal source of lead paint, especially in older houses. 

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