Effects of simulated acid rain on uptake, accumulation, and retention of fluoride in forage crops

Abstract

Forage crops accumulate F from exposures to the air pollutant HF and the rate and amount taken up can be affected by a number of external factors, one of which is precipitation. To assess how precipitation, including acidic precipitation, alters F uptake and retention in forage, alfalfa (Medicago sativa L. var. Saranac) and tall fescue (Festuca arundinacea Schreb. var. Kentucky 31) were subjected to extended exposures to HF and were treated periodically with various solutions (pH 5.6, 4.0, and 3.0) supplied as simulated rain or, for comparisons, as soil amendments. None of the treatments affected growth, but precipitation treatments significantly reduced the F content of both species relative to plants that received the same volumes of the same solutions added to the soil. Analyses of washed and unwashed foliage indicated that this loss of F was primarily due to the removal of F from foliar surfaces. There was no effect ofpH of rain on the F content of tall fescue, but for alfalfa an increase in acidity from pH 4.0 to 3.0 resulted in a further decrease in the F content of foliage, suggesting that in addition to removing superficial F, the more acidic simulated rain resulted in the leaching of F from within foliage was well. Materials and Methods PLANT CULTURESeed of alfalfa (Medicago sativa L. var. Saranae) and tall fescue (Festuca arundinacea Schreb. var. Kentucky 31) were shown in 9 × 9 cm pots containing peat-perlite (1 : 1) (Boodley and Sheldrake, 1973) and placed in a filtered, air conditioned greenhouse providing day/night temperatures of 24/18 °C and 16-hr photoperiods supplied by Water, Air, and Soil Pollution 43:191-198, 1989.

Use of Fluoride-Containing Water for the Irrigation of Soil–Plant Systems

“…The finding that overhead irrigation with good-quality water reduced foliar F concentrations (at least somewhat) is similar to the observation of Maclean et al, who, in a study of lucerne and tall fescue grass (Festuca arundinacea) exposed to atmospheric F, also found that rainfall (or washing with detergent) reduced the foliar concentration of F. Several mechanisms may result in a decrease in tissue F concentrations, including growth dilution, leaf death, translocation, or volatilization, with the last mechanism considered a major contributor of F removal from plants . Therefore, to investigate this possibility, plants were grown without overhead irrigation for another 2 weeks following the irrigation with deionized water.…”

Hemerocallis as bioindicator of fluoride pollution in tropical countries

“…In any case, the derivation of dose-effect relationships from field data has been proved to be extremely difficult as a great number of internal and external factors as light intensity, air and soil temperature, relative humidity, winds and precipitation do not only affect fluoride accumulation but also symptom expression (Weinstein, 1977;O'Connor and Horsman, 1982;VDI, 1989). Furthermore, in the Cubat~o region gaseous fluoride compounds do not occur all by themselves but in combination with other pollutants as SO2, 03, NOx and hydrocarbons etc., which may affect fluoride accumulation as well as physiological reactions leading to less than additive, additive or synergistic effects (Mc Cune, 1982;Wilson, 1988, 1990;MacLean et al, 1989;Davieson et al, 1990;MacLean, 1990). Nevertheless, the dependence of plant response from all these factors underlines the main advantage of bioindicators as integrators of the various concentrations and conditions to which plants are exposed in the field (Guderian and Reidl, 1982;Weinstein and Laurence, 1989) thereby facilitating risk prognosis.…”

Accumulation of airborne fluorides in forest trees and vegetation

“…The extensive literature on this topic has been reviewed several times (see, e.g. Following uptake, fluorides may be leached, evaporated and possibly translocated out of the leaf (BENEDICT et al 1964;HITCHCOCK et al 1971;KRONBERGER 1981;DAVISON 1982;TAKMAZ-NISANCIOGLU and DAVISON 1982;GARREC and CHOPIN 1983;MACLEAN et al 1989), and so the net accumulation under field conditions is generally lower than the total uptake. The uptake depends on the concentration and composition of fluoride in ambient air and the duration of exposure, but it also varies with vegetation structure, plant species and growth conditions (JACOBSON et al 1966;McCUNE and HiTCHCOCK 1971;DAVISON and BLAKEMORE 1976).…”

“…The uptake depends on the concentration and composition of fluoride in ambient air and the duration of exposure, but it also varies with vegetation structure, plant species and growth conditions (JACOBSON et al 1966;McCUNE and HiTCHCOCK 1971;DAVISON and BLAKEMORE 1976). Following uptake, fluorides may be leached, evaporated and possibly translocated out of the leaf (BENEDICT et al 1964;HITCHCOCK et al 1971;KRONBERGER 1981;DAVISON 1982;TAKMAZ-NISANCIOGLU and DAVISON 1982;GARREC and CHOPIN 1983;MACLEAN et al 1989), and so the net accumulation under field conditions is generally lower than the total uptake.…”