Application of the multiuse encapsulator agent F-500 for environmental remediation.

In the framework of the “Risk Assessment” procedure for the ecotoxicological evaluation of compounds used in the aquatic environment, tests with target species have been carried out. This paper reports the results concerning the evaluation on cladocerans Daphnia magna of the acute toxicity of F-500 micelle encapsulator (Hazard Control Inc., USA), a mixture of ionic and non-ionic surfactants based on fatty acid esters with aliphatic polyalcohols in watery solution, used as fire fighter agent as well as dispersant against hydrocarbon pollution, with the purpose to verify its compatibility for the aquatic environment and its potential usefulness for the remediation of soils polluted with hydrocarbons. F-500 has been indicated to be active for soil remediation; some laboratory studies have shown that F-500 is able to encapsulate hydrocarbons occurring into the soil and to extract and maintain them in watery solution, making them more accessible for the remediation process and consequently decreasing both their toxicity and bio-availability. As a matter of fact, F-500 has high affinity for soil particles and was demonstrated that 0.1% F.500 solutions are adsorbed almost completely (>99%) in soils; furthermore, after elution of soil with water less than 1% of F-500 was found into the eluate. The artificial soil was prepared according to the standardized procedures. Soil constituents were previously dried and subsequently dampened with deionized water in order to obtain 40-60% of the maximum water retention. For ecotoxicological tests the artificial soil was treated with commercial diesel and with F-500 at the concentration (1.5%) known to be non-toxic for the organisms. The artificial soil was packed up in 5 cm diameter glass columns and subsequently eluted with deionized water to obtain the eluate, according to the USEPA method. The elutriate was obtained placing soil aliquots and deionized water (1:4) in glass beakers and maintaining them stirred for 1 hour. For both eluate and elutriate testings the following four samples were prepared and subsequently tested: 1) control (only soil), 2) soil + diesel, 3) soil + 1.5% F-500, 4) soil + diesel + 1.5% F-500. Two different tests were carried out with the eluate using two different amounts of both compounds (Diesel 10 ml; F-500 5 ml in the test A; Diesel 20 ml; F-500 10 ml in the test B), thus maintaining unchanged the Diesel/F-500 rate (2:1). Four different tests were carried out with the elutriate maintaining unchanged the diesel amount and varying the diesel:F-500 rate, namely 2:1 (A), 1:1 (B), 1:2 (C), 1:4(D). Daphnia magna specimens have been obtained from Daphtoxokit ephippia (Microtox, Milano, Italy; batch DM281009) and maintained at 25±2°C in aerated and properly screened mineral water supplemented with 0.45 mm-filtered 1:100 CaCl2 solution and 0.45 mm-filtered 1:100 NaHCO3 solution. Before the test 30 Daphnia magna females were isolated and maintained starved for 24 hours; the offspring born during this period were used in the test and exposed for 24 hours at 20±2°C, 16:8 light:dark period, to eluates and to elutriates in multiwell plates with polyethilene inserts (NetwellTM Corning, NY, USA) provided with 74 mm porosity basal membrane. Five organisms per test in quadruplicate against control test were utilized. The tested F-500 concentrations were chosen considering the results of preliminary assays. The acute toxicity was evaluated estimating as end-point the percent immobilization of treated newborn specimens after 10 sec. according to OECD. The results have been expressed as IC50. The results of the tests are shown in table 1 (a, b). The data confirm that F-500 is not toxic to daphnids and show clearly that mixing F-500 to a soil pollutant (commercial diesel) the acute toxicity induced by eluates and elutriates on cladocerans decreases remarkably. This allows to confirm the ecocompatibility of F-500 and its suitability for soil remediation. F-500 is an easy-to-use compound useful for the remediation of soils and effective particularly under aerobic conditions; it is able to improve the biological degradation of contaminants by natural microbial populations as well as to stimulate the biodegradation reducing the toxicity of the environmental pollutants or making them innocuous. F-500 allows to restore the usage of the treated areas accelerating the self-regeneration of contaminated soils and restoring rapidly the ecological equilibrium (http://www.fctservices.co.uk/F-500-land-application/). The overall ecocompatibility and the low toxicity against marine crustaceans and fish of F-500, evaluated through standardized parameters, are known. The tests carried out in this study have shown an evident decrease of the toxicity in soils treated with diesel + F-500 in comparison to those treated with only diesel. This result is supposed to be due to the power of the compound to encapsulate the hydrocarbon molecules maintaining them in watery solution. Like this, the hydrocarbons could be made less available to the organisms thus resulting less toxic. Therefore, the results show a potential protective effect of F-500 against the damage exerted by pollution on aquatic organisms and the suitability of this compound to counteract the soil pollution.