Soil interactions concentration effect

Proximity to the smokestacks of metal smelters is positively associated with increased levels of lead in the hair (manes) of horses and in tissues of small mammals, and is consistent with the results of soil and vegetation analyses (USEPA 1972). Lead concentrations were comparatively high in the hair of older or chronically impaired horses (USEPA 1972). However, tissues of white-tailed deer (Odocoileus virginianus) collected near a zinc smelter did not contain elevated levels of lead (Sileo and Beyer 1985). Among small mammals near a metal smelter, blood ALAD activity was reduced in the white-footed mouse but normal in others, e.g., the short-tailed shrew (Beyer et al. 1985). The interaction effects of lead components in smelter emissions with other components, such as zinc, cadmium, and arsenic, are unresolved (USEPA 1972) and warrant additional research. 

Malinconico M, Immirzi B, Massenti S, La Mantia FP, Mormile P, Petti L (2002) Blends of poly-vinylalcohol and functionalized polycaprolactone. A study on the melt extrusion and post-cure of films suitable for protected cultivation. J Mat Sci 37 4973 1978 Mallek SB, Prather TS, Stapleton JJ (2007) Interaction effects of Allium spp. residues, concentrations and soil temperature on seed germination of four weedy plant species. Appl Soil Ecol 37 233-239. doi 10.1016/j.apsoil.2007.07.003... 

Mallek SB, Prather TS, Stapleton JJ (2007) Interaction effects of Allium spp. residues, concentrations and soil temperature on seed germination of four weedy plant species. Appl Soil Ecol 37 233-239... 

The values of k were 0.18, 1.98 and 1.16 x 10 (moldm s basis) for Soils A, B and C in Figure 3.15, respectively. These values are more than four times k for the solution system. The values of the inhibition coefficients-a = —1686, = 6.13, c = 3854—were smaller than in the solution system. As a result the concentrations of P and DOC required to halve the rate of precipitation were 10 times those in the solution system. Also the interaction between [Pl] and [Cl] was negligible in the solution system but important in the soils. Figure 3.16 shows plots of Equation (3.54) for different valnes of [Pl] and [Cl] and w = 0.75 gdm. For the values used, which are realistic for submerged-soil solutions, the combined inhibitory effect of P and DOC was snch that an order of magnitude greater degree of supersaturation [(Ca +)(C03 )/A sp] is necessary to produce the same rate of precipitation as in the absence of inhibitors. 

It is also important to understand that most allelopathic effects apparently result from the combined actions of several allelochemicals, often with each below a threshold concentration for impact. In allelopathic situations which implicate phenolic acids, soil concentrations have ranged from below 10 to above 1000 ppm for each compound. The lower end of the spectrum is below a concentration required for an effect in current bioassays. Additive and synergistic effects have been demonstrated, however, for combinations of cinnamic acids (102), benzoic acids (103), benzoic and cinnamic acids (10 ). and -hydroxybenzaldehyde with coumarin (105). It appears that such combined interactions may be very important under field conditions. 

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