13.1 Plume Hypothesis

If the receptor is within an area source, or if emission rates do not vary markedly from one area source to another over most of the simulation area, the narrow-plume hypothesis can be used to consider only the variation in emission rates from each area source in the alongwind direction. Calculations are made as if from a series of infinite crosswind line sources whose emission rate is assigned from the area source emission rate directly upwind of the receptor at the distance of the line source. The ATDL model (22) accomplishes this for ground-level area sources. The RAM model (8) does this for ground-level or elevated area sources. 

In summary, the following lines of evidence are generally invoked in favour of the plume hypothesis ... 

Finally, the Tyrrhenian Sea (i.e. the focus of the mantle plume ascent) has a considerable depth (3700 m) and magmatism is not particularly voluminous. These characteristics do not fit a plume hypothesis. The suggestion that lack of magmatism is related to the great depth of the plume head is reasonable. However, the idea that such a deep body would be able to induce basin opening of the order of several hundred km, and to generate a collisional chain, is difficult to accept and needs much further refinement to avoid scepticism. 

One of the principal difficulties with the plume hypothesis is that it has been used by a very large number of geoscientists to explain... 

The geochemical arguments used in support of the plume hypothesis are ambiguous and do not require the deep and shallow sources proposed by plume theorists. 

Portions of the material described here are derived from a comprehensive airshed modeling program in which the authors are participating (17). This chapter focuses on urban airshed models however novel models have been proposed for urban air pollution problems of a more restricted scale— particularly, the prediction of concentrations in the vicinity of major local sources, notably freeways, airports, power plants, and refineries. In discussing plume and puff models earlier we pointed out one such class of models. Other work is the model proposed by Eschenroeder (18) to predict concentrations of inert species in the vicinity of roadways and the modeling of chemically reacting plumes, based on the Lagrangian similarity hypothesis, as presented by Friedlander and Seinfeld (19). 

Phosphorus and vanadium, which are typically present in seawater as dissolved oxyanion species, have been shown to exhibit systematic plume-particle P Fe and V Fe variations which differ from one ocean basin to another (e.g., Trefry and Metz, 1989 Feely et al., 1990). This has led to the hypothesis (Feely et al., 1998) that (i) plume P Fe and V Fe ratios may be directly linked to local deep-ocean dissolved phosphate concentrations and (ii) ridge-flank metalliferous sediments, preserved under oxic diagenesis, might faithfully record temporal variations in plume-particle P Fe... 

Hartmaim WK (1984) Moon origin the impact-trigger hypothesis. In Hartmann WK, Philhps RJ, Taylor GJ (eds) Origin of the Moon. Lunar and Planetary Institute, Houston, p 579-608 Hauri EH, Whitehead JA, Hart SR (1994) Fluid dynamic and geochemical aspects of entraimnent in mantle plumes. J Geophys Res 99 24275-24300... 

The hypothesis of plate tectonics attempted to provide an explanation on the hoop movement of the continents on the Earth s spherical surface. But, it also encountered the difficulty of driving force. So, it introduced other mechanisms such as the presence of asthenosphere and/or mantle plumes. 

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