Contributions anthropogenic

Fig. 12-5 The ammonia-ammonium cycle. Each arrow represents one flux. The magnitude of the flux is given in Tg N/yr Where two numbers are given, the top value is the anthropogenic contribution and the lower is the total flux (natural + anthropogenic).

Finally, some authors have computed metal loading to the enviroranent from specific human activities, such as discharges of waste-water, and compared these with natural release rates. While the details of the computations and conclusions vary, the general observation for many metals is that anthropogenic contributions to metal ion transport rates and environmental burdens are approaching and in many cases have already exceeded natural contributions. A few such comparisons are provided in Tables 15-1-15-4. 

Shotyk W, Goodsite ME, Roos-Barraclough F, Frei R, Heinemeier J, Asmund G, Lohse C, Hansen TS. 2003. Anthropogenic contributions to atmospheric Hg, Pb and As accumulation recorded by peat cores from southern Greenland and Denmark dated using the C bomb pulse curve. Geochim Cosmochim Acta 67 3991 011. 

There are a number of light stable isotope measurements that provide very important data in the study of paleoclimates to better understand and interpret anthropogenic contributions to present-day climate change (Fritz and Fontes 1980). These measurements involve the determination of carbon and oxygen isotopes in fresh-... 

Naturally occurring compounds in sediments (lipids, polysaccharides, lignins, etc.) have also been determined by this method. The compounds generated from non-polluted sediments are completely different and easily discriminated from anthropogenic contributions. 

The isotopic compositions of the industrial sulfur sources are generally so variable, that the assessment of anthropogenic contributions to the atmosphere is extremely difficult. Krouse and Case (1983) were able to give semiquantitative estimates for a unique situation in Alberta where the industrial SO2 had a constant value near 20%c. Generally, situations are much more complicated which limits the fingerprint character of the sulfur isotope composition of atmospheric sulfur to such rare cases. 

Consider ozone production and decomposition in the atmosphere, including anthropogenic contribution to the decomposition. Use the steady-state treatment. 

One particular type of source that should be studied carefully Is entrained soil. As shown above, this Is often the greatest contributor of TSP In urban areas. As there Is so much of It present, we need to know concentrations of all measured elements quite well to make an accurate determination of the residual amounts left to be accounted for by other sources. The composition of selved soil Is often used for the soil component, but there may be considerable fractionation Imposed by entrainment, e.g., preferential selection of very fine clay mineral particles. Such fractionation has been demonstrated In the very limited studies of entrainment of particles from soil of known composition (e.g.. Refs. 21, 49). These studies can probably best be done In controlled environments such as wind tunnels. One cannot simply collect ambient particles In the countryside and consider it to be soil, as there are anthropogenic contributions even at great distances from cities ( ). There Is further confusion betwen clean, "continental" dust and "urban" dust. The latter, which Is usually collected near city streets (21, 50), typically has a composition of soil contaminated by anthropogenic emissions, especially from motor vehicles. 

The following sections focus on the potential indirect effects of aerosol particles due to anthropogenic contributions, which, unlike the natural emissions, are expected to provide a contribution that changes with time. 

Keywords Anthropogenic contribution, Chemical composition, Chemical transport modelling, Natural contribution, North-western Europe, PM10, Source apportionment, Spain... 

The anthropogenic contribution of the unknown part is by definition unknown. Water accounts to some extent for the unknown fraction. As most of that water may be associated with SIA, it is likely that a significant part of the unknown fraction is anthropogenic. It is assumed that the anthropogenic and natural parts of the unknown fraction resemble those of the defined mass. 

Chloromethane is the most abundant organohalogen - anthropogenic or natural - in the atmosphere. The myriad natural sources of CH3C1 dwarf the anthropogenic contribution (Table 3.1). Subsequent to the previous survey (7) a number of new natural sources of CH3C1 have been identified, and other reviews have appeared (42, 246, 247). 

Is a reliable estimation of the anthropogenic contribution to climate change possible ... 

PAHs in soil can be attributed to natural processes and human activities. Individual PAH concentrations in soils produced by natural processes like vegetation fires and volcanic exhalations have been estimated to be in the range of 1-10pgkg-1. Anthropogenic contribution has greatly affected the soil PAH concentrations. At present, even the lowest... 

Fig. 1. The global sulfur budget. (Figures in brackets indicate anthropogenic contributions).

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