Heavy metals, atmospheric deposition

HEAVY METALS ATMOSPHERIC DEPOSITION AROUND A MUNICIPAL INCINERATOR PLANT IN BELGIUM... 

Atmospheric Deposition of Heavy Metals and Forest Health. Smith, W.H. Virginia Polytechnic Institute Blaclsburg, VA, 1989. 

Atmospheric contaminants from smelting works or combustion processes eventually enter the natural drainage system as fall out, and are carried into the rivers. It is probable that the deposition of sediments and the higher pH of marine water, which leads to precipitation, results in a build-up of the heavy metal pollutants in the river estuary. An assessment of this build-up is essentially an analytical problem. 

The receptors of interest are soils of agricultural (arable lands, grasslands) and non-agricultural (forests, steppes, heath lands, savanna, etc.) ecosystems. In non-agricultural ecosystems, the atmospheric deposition is the only input of heavy metals. Regarding the Forest ecosystems, a distinction should at least be made between Coniferous and Deciduous Forest ecosystems. When detailed information on the areal distribution of various tree species (e.g., pine, fir, spruce, oak, beech and birch) is available, this should be used since tree species influence the deposition and uptake of heavy metals and the precipitation excess. On a world scale, soil types can be best distinguished on the basis of the FAO-UNESCO Soil Map of the World, climate and ecosystem data from NASA database (1989). 

Apart from anthropogenic emissions, heavy metals enter the atmosphere of Europe due to re-emission of previously deposited substances and from natural sources. These types of sources are taken into account on the basis of expert estimates made in MSC-E (Ryaboshapko and Ilyin, 2001 Travnikov and Ryaboshapko, 2002). 

As a rule, simulations consider emissions of heavy metals from anthropogenic and natural sources, transport in the atmosphere and deposition to the underlying surface (Figure 6). It is assumed that lead and cadmium are transported in the atmosphere only as a part of aerosol particles. Besides, chemical transformations of these metals do not change removal properties of their particles-carriers. On the contrary, mercury enters the atmosphere in different physical and chemical forms and undergoes numerous transformations during its pathway in the atmosphere (Ilyn et al., 2002 2004 Ilyin and Travnikov, 2003). 

Heavy metals are removed from the atmosphere by means of surface uptake and precipitation scavenging. The ecosystem-specific dry deposition scheme is based on the resistance analogy approach and distinguishes 16 land use types. Wet removal by precipitation considers both in-cloud and sub-cloud scavenging. 

Assessments of atmospheric pollution have been made by the regional (MSCE-HM) and the hemispherical (MSCE-HM-Hem) transport models developed in MSC-E (Ilyin et al 2004). The regional model covers the EMEP region (European domain) with the spatial resolution of 50 x 50 km the hemispheric model describes the atmospheric transport within the Northern Hemisphere with the spatial resolution of 2.5 x 2.5 . The main outputs of the modeling include data on heavy metal concentration in the air and precipitation as well as levels of deposition to the surface. Since the negative impact of heavy metals on human health and biota is mainly attributed to their long-term accumulation in environmental media, particular attention has been given to the assessment of their depositions from the atmosphere. 

Annual emissions of heavy metals from the anthropogenic sources of HELCOM countries significantly decreased during the period of 1990-2001. In particular, annual emissions of cadmium decreased by 45%, whereas lead and mercury emissions reduced by 60%. Following this reduction and also due to the changes of heavy metals emissions in other European countries the level of atmospheric depositions to the Baltic Sea has also significantly decreased (Figure 20). Compared to 1990... 

Storm water runoff from cities and villages presents another problem. This runoff contains salts from road deicing, street refuse, animal waste, food litter, residue from atmospheric deposition of sulfuric and nitric acid, metals, asbestos from automobile brakes, rubber from tires, hydrocarbons from motor vehicle exhaust condensates, oil and grease, soil and inorganic nutrients from construction sites, and a variety of other chemicals. Research shows a heavy impact of urban nonpoint pollution on freshwater quality (World Resources Institute, 1988). 

Helena, P., Franc, B. and Cvetka, R.L. (2004) Monitoring of short-term heavy metal deposition by accumulation in epiphytic lichens (Hypogymnia physodes (L.) Nyl.). Journal of Atmospheric Chemistry, 49, 223-30. 

As a result of their geographical circumstances and these various historical developments, many estuaries appear to be among the most heavily loaded ecosystems in the world in terms of the amount of nitrogen and phosphorus received per unit area (Fig. 5). Even the farm fields of the American corn belt do not receive the fertilization common to many estuaries, and the nutrient inputs to natural terrestrial systems and fresh waters appear to be orders of magnitude lower. There are fewer data available on the inputs of metals and other pollutants to estuaries, but the evidence at hand suggests that the delivery of heavy metals to estuaries may equal or exceed that deposited from the atmosphere on heavily industrialized urban areas and exceed that deposited on rural terrestrial ecosystems by orders of magnitude (Fig. 6). 

Nguyen, V. D., A. G. A. Merks, and P. Valenta. 1990. Atmospheric deposition of acid, heavy metals and dissolved organic carbon and nutrients in the Dutch delta area in 1980—1986. Science of the Total Environment 99 77—91. 

Andersen, A., Hormand, M.F. Johnson, I. (1978) Atmospheric heavy metal deposition in the Copenhagen area. Environmental Pollution, 17, 133-51. 

Han, Y.-J., Holsen, T.M., Hopke, P.K., Cheong, J.-P., Kim, H., Yi, S.-M., 2002. Identification of source locations for atmospheric dry deposition of heavy metals during yellow-sand events in Seoul, Korea in 1998 using hybrid receptor models. Atmos. Environ. 38, 5353-5361. 

The assessment of plant-available soil contents can frequently be achieved and validated by field experiments for nutritionally essential elements, and, for a few potentially toxic elements such as chromium, nickel and molybdenum, at the moderately elevated concentrations that can occur in agricultural situations. The validation of extraction methods, devised for agricultural and nutritional purposes, is much less easy to achieve when they are applied to heavy metals and other potentially toxic elements, especially at the higher concentrations obtained in industrially contaminated land. This is not surprising in view of the fact that for some heavy metals, for example lead, there is an effective root barrier, in many food crop plants, to their uptake and much of the metal enters plants not from the root but by deposition from the atmosphere on to leaves. In these circumstances little direct correlation would be expected between soil extractable contents and plant contents. For heavy metals and other potentially toxic elements, therefore, extraction methods are mainly of value for the assessment of the mobile and potentially mobile species rather than plant-available species. This assessment of mobile species contents may well, however, indicate the risk of plant availability in changing environmental conditions or changes in land use. 

Morselli L, Cecchini M, Grandi E, et al. 1999. Heavy metals in atmospheric surrogate dry deposition. Chemosphere 38(4) 899-907. 

Riihling, A. (Ed.) (1994). Atmospheric Heavy Metal Deposition in Europe—Estimation Based on Moss Analysis. 53 p. Nordic Council ofMinisters, Nord. 

Metal contamination of soils is primarily due to the application of sewage sludge, manure, phosphate fertilizers, atmospheric deposition, and traffic emissions. The most common heavy metal ions found in soils are Zn, Cu, Ni, Pb, Cr, and Cd. As mentioned earlier (see Section 6.3.1.4), sequential extraction techniques can differentiate among the metal forms in a soil, typically the acid soluble fraction (e.g., carbonates), the reducible fraction (e.g., iron/manganese oxides), and the ox-idizable fraction (i.e., metals in low oxidation states). 

Pandey, J., Pandey, U. Accumulation of heavy metals in dietary vegetables and cultivated soil horizon in organic farming system in relation to atmospheric deposition in a seasonally dry tropical region of India. Environ. Monit. Assess. 149, 61-74 (2009)... 

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