Ash Leaching of Forest Species Treated with Phosphate Fire Retardants

Abstract

The chemical, mineralogical, and leaching behavior of three dominant Greek forest species ashes (Pinus halepensis, Pistacia lentiscus, and Olea europaea), before and after treating forest species with diammonium phosphate (DAP) 5% and 10% weight to weight, have been studied using a new five-step shake leaching method at pH=6. For the analysis of ashes (prior and after leaching) and leachants, the following analytical techniques were used: atomic absorption spectroscopy, X-ray diffraction, and scanning electron microscopy with energy dispersive X-ray fluorescence analysis. The presence of DAP obstructs the extraction process of some metal ions (i.e., Na, K) contained in ashes by converting the soluble carbonate salts to the less soluble phosphates (i.e., Na 2 CO 3 → Na 3 PO 4 ). On the contrary, DAP enhances the mobility of some other metals (i.e., Ca) by forming more soluble compounds [i.e., CaCO 3 → Ca 3 (PO 4 ) 2 ]. In addition, the presence of DAP lowers the pH of leachates, causing dissolution of some toxic elements (i.e., Mn, Pb, Zn). Unexpectedly, DAP prevents the leachability of Cr from ash. The above study concerns the environmental effects (soil and ground and underground water streams) caused by the use of chemical retardants on forest fires.

Environmental benefits of using magnesium carbonate minerals as new wildfire retardants instead of commercially available, phosphate-based compounds

“…1). One likely explanation of this finding is that DAP is capable of obstructing the extraction of some metal ions contained in ash by forming phosphate salts (e.g., Na 3 PO 4 , K 3 PO 4 ), which are less soluble than the respective carbonates (Liodakis and Tsoukala 2008;Lide 2007). These compounds reportedly can be formed via the thermal decomposition of DAP to polyphosphates (NH 4 PO 3 ) n and P 2 O 5 (Liodakis et al 2007).…”

Interpretation of the Factors Defining Groundwater Quality of the Site Subjected to the Wildfire of 2007 in Ilia Prefecture, South-Western Greece

“…The concentration of H 2 S was measured in the field using a Hach DR 2400 portable spectrometer (Hach, Loveland, CO, USA), while CO 2 and alkalinity were measured using a Hach Digital Titrator. NO 3 − , NO 2 − , PO 4 3− , SO 4 2− , F − , SiO 2 and NH 4 + concentrations were determined using a Hach DR 4000 spectrometer. The concentration of Cl − was measured using a Hach Digital Titrator.…”

“…There have been several publications over the current decade that report on the impacts of the produced ash on soil and soil water, mentioning the need for the potential impacts on groundwater to be also examined. According to several laboratory-conducted studies that simulated the combustion of biomass, such as P. halepensis, ash is alkaline (pH = 9-13.5), rich in elements, such as Ca, Mg, Na, K, Al, Fe and P, S and trace elements, such as Mn and Zn [2][3][4]. The most prevailing elements after the wildfires were reported to be Ca, Mg, K, Si, P [5], Mn, Zn, V, Pb, Cr, and Cu [6].…”

“…These studies underlined the need for potential impacts to be examined under field conditions [11][12][13]. Long-term fire retardants are the same chemical compounds, nitrogen, phosphorus, and sulfur, found in agricultural fertilizers [2,3]. Laboratory treatments of P. halepensis needles have proven the leaching of ammonium ions and phosphates and the elution of Fe, Cu, Zn, and Mn into soil water, which could end up in groundwater [11].…”

Latest trends for structural steel protection by using intumescent fire protective coatings: a review

“…Li et al. [161] synthesised an intumescent fire resistant coating based on PER, APP, and MEL. Molybdenum trioxide (MoO 3 ) and ferric oxide (Fe 2 O 3 ) were added as inorganic fillers to improve the thermal properties of IC.…”