Elements natural background

Exposure to elements such as As, U and Rn may represent an increased human health risk, particularly in areas where the natural background concentrations are elevated. 

The country-wide dataset of stream sediment analyses in Austria consists of 36,136 samples analyzed for 34 chemical elements (Fig. 1), (Thalmann et al. 1989). Complemented by local surveys of hydrochemistry, whole rock geochemistry, soil chemistry and mineralogical phase analyses, these data are used to derive natural background levels of different rock units, investigate chemical fluxes between soil, rock and groundwater, and evaluate the emission risks of historical mine waste. 

The long-term uses of lead explain why this element should be so widely dispersed in the environment. In this regards one should answer the question as to what is the natural background level of lead. At present this is a question of controversy. Lead... 

The most generally applied method for determination of an arsenical is by atomic absorption spectrometry (AAS) after reduction of the compound to AsH3. However, this only provides an indication of the presence of the element as against a natural background. Lewisite rapidly hydrolyzes to 2-chlorovinylarsonous acid (CVAA see Figure 7) in an aqueous environment such as blood plasma, and analytical methods have focused mainly on the determination of CVAA (see Chapter 16). 

Europe. Situation is far less favorable in Europe. Fewer data are available in the standard scientific literature and most of the rivers are strongly impacted by pollution. Only the rivers from the northern part of Europe (Kola peninsula) reported by Pokrovski and Schott (2002) are probably close to the natural background. The enhancement of dissolved concentrations for a number of elements due to human activities is apparent from the data on the Seine River. Data for REEs in the Rhine River and streams from the Vosges mountains in Alsace and central Europe have been reported for comparison. All these locations are known to have suffered from acid deposition in the very recent past. 

Geochemical anomaly a concentration above the natural background level (q.v.) of one or more elements in rock, soil or related material. 

Natural background of elements, the concentration of an element in naturally-occurring material that could be regarded as normal as distinct from anomalous . 

Metals eoneentration in sediments show that the Ross Sea and Terra Nova Bay do not suffer from anthropogenic inputs and therefore these values can be assumed to be the natural background levels. The importanee of humic acids as regards mobility, concentration and accumulation of trace metals in marine environment, espeeially of Cu, has been confirmed even for Antarctica. From this point of view, the study of the humie fraetion and eomplexed metals seems to be an interesting opportunity to better understand the role of the sedimentary phase in the biogeochemical eycle of the elements. 

The long-term uses of lead explain why this element should be so widely dispersed in the environment. In this relation we should answer the question as to what is the natural background level of lead. At present this is a question of controversy. Lead levels in modern people are frequently 10% of the toxic level. Some analyses of ancient bones and ancient ice cores seems to suggest that this relatively high level is not new and has been existed in the environment. Accordingly, the assumption was carried out that life has evolved in the presence of this toxic element. 

Human beings depend on soils uncontaminated by toxic elements to produce their food. They need clean drinking water -which is often derived from river water -and they need clean air to breathe. The anthropogenic contamination of soils, waters, and air can only be discovered if the natural background in the abundance of trace metals is known. Therefore, knowledge of the natural cycles of these elements and of the size of the natural reservoirs is required for a better understanding of numerous environmental problems. 

Fig. 11.2 Variation in multi-element profiles of street dust, garden soil, and house dust, sampled from 48 houses in the city of Ottawa, Canada. Total element concentrations in the 100-250 xm size fraction are normalized against natural background concentrations, using the 95 "%ile for all media (modified from Rasmussen et al., 2001).

This work deals on one hand with the normal characteristic trace element input from common rocks to the environment (natural background), but also shows cases of regional natural contamination. In the first section, an overview on the typical chemical variation of the dilferent chemical rock types and general chemical trends of soils, waters, plants and sediments related to them will be given. In the second section, case studies representing typical local background situations of the most important chemical rock types of the lithosphere are discussed. The third section deals with a selected number of naturally contaminated situations at local and regional scale. 

---