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Environmental effects of fire retardants applications on soil and groundwater: a laboratory study

By Σοφία Κουφοπούλου


Wildfires during summer season occur frequently throughout the Mediterranean basin. Forest fires in the last 30 years were recognized as a major environmental problem for Greece (a Mediterranean country). Agencies which apply millions of gallons of fire suppression chemicals worldwide, suggest the use of chemical retardants as effective firefighting tools. The question is what about the toxicological or ecological effects for the specific ecosystem? A part of these complicate ecological problem consist in the adverse effects on groundwater quality. In this work it was studied the impact of a widely used Long Term fire Retardant (LTR), on the leaching of a range of physico-chemical parameters on a Mediterranean forest soil in a short term lab scale study, before and after fire conditions with and without forest vegetation. LTRs are mixtures of water, ammonium and phosphates salts, clays and gums which on the field come in contact with specific soil, water, plant (pinus halepensis) and fire conditions. There are many reports about the effects of fire on soils, water bodies and aquatic life whereas, studies that concerning the environmental impact of LTRs in Mediterranean ecosystems - areas are still lacking (Angeler et al.2004). The effects of fire retardant (fire troll 931) application on leachate quality from a typical Mediterranean forest soil is the subject of this work. The next procedure was followed. After a simulated annual precipitation on treated and control flowerpots which contained forest soil alone or with pinus halepensis before and after fire conditions the leachates were collected and analysed. The samples were coded as soil samples (S samples), soil retardant samples (SR), soil tree samples (ST), soil tree retardant (STR). In the case where leachates were collected after fire conditions the samples were coded as soil tree fire (STF), soil tree retardant fire (STRF). Leachates conservation and analysis were realised according to international standard methods. Also a certain number of analysis were realised with short alternative methods. The influence of vegetation on the quality of the leachates and the influence of retardant on vegetation growth were examined. The leaching profiles of conductivity, hardness, total dissolved solids Ca and Mg during the simulated annual precipitation were similar. The above parameters in samples treated with retardant were higher than in their controls, whereas the differences among the leaching profile of samples of the treated and control ones are not significant. The leaching of P, under the conditions used, was found to be a small percentage of the initially applied P (below 2,4%) quantities in the case of (SR) samples. However, it was different among treated samples affected by both plant (STR) and fire conditions (STRF). Up to 30% of the total N in the retardant was lost to leachate, primarily as NO3--N. In the case of SR the vegetation seems to decrease to some extent the N leaching. The N leaching from treated pots with a burnt tree is lower compared with that from treated pots with a living tree, due to the partial N volatilization during the fire. The leaching of Na, K, Fe, Si from samples treated, were significantly higher than in their controls. The rates of Fe and Si leached are less than 6% to the quantities applied, major are the rates of Na leached (30%). Cloride ions total quantities appeared higher for samples treated with retardant, to their controls. Although this is a laboratory study, these results may be considered as rough indications of LTR environmental implications, due to the leaching of a significant part of the retardant’s costituents into groundwater.

Topics: Επιβραδυντές δασικών πυρκαγιών, Ποιότητα υπόγειων υδάτων, Δασικά εδάφη, Πεύκα, Εργαστηριακή τεχνική, Επίδραση φωτιάς, Επίδραση βλάστησης, Fire retardants, Groundwater quality, Forest soil, Pinus halepensis, Laboratory study, Post fire effects, Vegetation impacts, Πεντέλη, Όρος, Greece
Publisher: National Technical University of Athens (NTUA)
Year: 2008
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