Emission of Volatile Organic Compounds and ...

Water Air Soil Pollut (2015) 226:50 DOI 10.1007/s11270-015-2349-y

Emission of Volatile Organic Compounds and Greenhouse Gases from the Aerobic Bioremediation of Soils Contaminated with Diesel Marcio Gonçalves Franco & Sergio Machado Corrêa & Marcia Marques & Daniel Vidal Perez

Received: 4 October 2014 / Accepted: 6 February 2015 # Springer International Publishing Switzerland 2015

Abstract Bioremediation is one of the most frequently used treatments for reducing high levels of organic contaminants from soil. This article complements previous work on the anaerobic bioremediation of soils contaminated with diesel, which has revealed the generation of high levels of greenhouse gases and volatile organic compounds by anaerobic bacteria activation. Unlike anaerobic methods that generate low concentrations of CH4 and CO2 regardless of the pollutant (mainly through the action of anaerobic bacteria), aerobic bioremediation methods yielded high concentrations of greenhouse gases and volatile organic compounds due to the breakdown of long molecular chains during bioremediation. The aim of this study was to characterise the greenhouse gases and volatile organic compound emissions produced during the aerobic bioremediation of diesel-contaminated soils. The soil was contaminated M. G. Franco : S. M. Corrêa (*) Faculty of Technology, Rio de Janeiro State University-UERJ, Rodovia Presidente Dutra, km 298, Resende, RJ 27537-000, Brazil e-mail: [email protected] M. Marques Faculty of Engineering, Rio de Janeiro State University-UERJ, Rua São Francisco Xavier, 524, sala 5024E, Maracanã, Rio de Janeiro, RJ 20559-900, Brazil e-mail: [email protected] D. V. Perez National Centre for Soil Research, Embrapa, Rua Jardim Botânico 1024, Jardim Botânico, Rio de Janeiro, RJ 22460-000, Brazil e-mail: [email protected]

with 0.5, 2.0 and 4.0 % (w/w) diesel oil and stored in glass reactors for 90 days under aerobic conditions under abiotic processes, natural attenuation and biostimulation. The emitted gases were collected with charcoal cartridges and gastight syringes. Chemical analyses were performed by gas chromatography with multiple detectors. The results indicated high concentrations of CO 2 (418.6 mg kg − 1 ) and low levels of CH 4 (2.69 mg kg−1), N2O (0.33 mg kg−1) and volatile organic compounds (VOCs) (0.30 mg kg−1). Keywords Emissions . Diesel . Atmosphere . Bioremediation . VOCs . GHGs

1 Introduction The environmental contamination of air, soil and water has increased over the years, and the main cause of this problem is the industrialisation of developed and developing countries. Contamination may occur by the dispersion of solid, liquid and gaseous pollutants over the soil surface or into the soil. These processes are the result of the rapid industrial development that Brazil has experienced since the second half of the last century, which has only accelerated in the present century. Among the cities in Brazil, 4,572 (CETESB 2013) and 160 (INEA 2013) areas in São Paulo and Rio de Janeiro, respectively, are contaminated due to environmental pollution. The current composition of the Brazilian energy matrix still includes a substantial contribution by fossil

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fuels. Data from the Ministry of Mines and Energy (EPE 2012) indicate that 54 % of the energy consumed in Brazil comes from fossil fuels (petroleum and derivatives, coal and natural gas). This share should increase with the gradual use of the oil pre-salt layer, and there is growing concern about future spill events and soil contamination. Among these risks, those related to atmospheric emissions arising from processes such as SO2, NOx, CO, H2S and hydrocarbons, which have been the subject of relatively little research, are notable (Mariano 2005; Tegmpri 2010). Although bioremediation is widely used, in laboratory scale, pilot studies and industrial scale in several countries on the decay of contaminants in soil, sediment or water (Ausma et al. 2002; Sarkar et al. 2005; Martinez-Soria et al. 2009; Franco et al. 2014; Nammari et al. 2007a; 2007b), there is a lack of information on the atmospheric emissions originating from volatile compounds or others generated during bioremediation treatment. It is common to credit degradation of the contaminants to the microorganisms, and more studies are necessary to quantify the relevance of such processes as volatilisation or breaking of heavy contaminants into lighter compounds (Ward et al. 2003; Fairey and Loehr 2003; Lebkowska et al. 2011). Because of concern about the emissions of volatile organic compounds (VOCs) and greenhouse gases (GHGs), studies have been conducted by ChagasSpinelli et al. (2012), Lebkowska et al. (2011), Dias et al. (2012), Agamuthu et al. (2013) and Taccari et al. (2012). According to these researchers, many VOCs are emitted during different anthropogenic activities related to solid waste, such as its disposal in dumps or landfills (Zou et al. 2003) and its storage for subsequent incineration and energy recovery (Nammari et al. 2007a, b). These studies quantified VOCs and GHGs and found alarming amounts of CH4 and CO2. Nakagawa and Andréa (2006) reported the anaerobic methanogenic character of bioremediation processes. However, little information has been reported about the atmospheric emissions of aerobic bioremediation processes, particularly VOC and GHG emissions, except in the studies of Loehr et al. (2001), Fairey and Loehr (2003), Ausma et al. (2002) and Martinez-Soria et al. (2009). This research focused on the monitoring and quantification of VOC and GHG emissions during the aerobic bioremediation of diesel-contaminated soil in laboratory bioreactors. It is a second step of our previous publication (Franco et al. 2014) on the anaerobic

Water Air Soil Pollut (2015) 226:50

bioremediation of diesel-contaminated soil. The specific objectives were (i) to evaluate the conversion of C10 to C25 hydrocarbons to lower-molecular-weight molecules and their volatilisation, (ii) to evaluate GHG emissions (CO2, N2O and CH4) and (iii) to determine the residual levels of hydrocarbons from diesel in the soil after three types of treatment: abiotic processes, natural attenuation and biostimulation.

2 Methodology 2.1 Soil Sampling and Site Description The soil used in the study was collected at the Rio de Janeiro Petrochemical Complex (COMPERJ) during its construction. This facility is located on State Highway 116, 5 km from Itaboraí City in the State of Rio de Janeiro, Brazil (22° 44′ 40″ S and 42° 51′ 34″ W). The soil was characterised according to the methodology used by EMBRAPA (2006), Sara (1994) and Carter and Gregorich (2008). All samples were collected on the same day under the same sampling conditions and subsequently homogenised, sieved, dried and stored in polyethylene bags. 2.2 Experimental Set-up Three different treatments and three levels of contamination were used to evaluate the bioremediation process: Abiotic processes (AP). To assess the emissions from the physical and chemical processes without the participation of microorganisms in the original soil; the soil pH was adjusted to approximately 7.0, as described in the literature (Sarkar et al. 2005). The soil was then treated with a 0.5 % w/w solution of sodium azide for 1 h and autoclaved for 2 h. The water used for moisture correction was also previously autoclaved. Natural attenuation (NA). To assess the contribution of abiotic and biotic processes without external interference; the soil was not treated with chemical reagents or sterilised. Biostimulation (BI). To stimulate the activity of the autochthonous microbiota; the soil pH was adjusted to 7.0, as described in the literature (Sarkar et al. 2005), and no sterilisation was performed. Phosphorus and nitrogen were added as sodium


phosphate and urea, respectively, to achieve a C/P/ N ratio equal to 100:5:1, according to a method reported in the literature (Ausma et al. 2002). The soil had an organic carbon concentration of 8.4 g kg−1; thus, 0.42 g kg−1 of phosphorus and 0.084 g kg−1 of nitrogen were added. Commercial diesel oil with 5 % biodiesel (B5 diesel) was chosen as the contaminant due to its likelihood of being involved in spills; this composition is used in Brazilian territories according to resolution number 4 02/02/2010 of the ANP (2010). Cylindrical borosilicate glass reactors with a total capacity of 2.0 L were used. Each reactor was aerated from the bottom via an air pump (KNF UNMP 850 KNDC) with a flow rate of 400 mL min−1. The air was bubbled in double-distilled water before entering each reactor and was changed daily. The flow rate was monitored continuously by a flowmeter (Dwyer MMA20). Aeration was intermittent, with 1 h on and 2 h off. A total of three treatments (AB, NA and BI) and three diesel concentrations (0.5, 2.0 and 4.0 %) were used in duplicate (18 experimental units). All reactors were kept in the same atmosphere at 25 °C. VOC samples were collected using activated double-bed charcoal cartridges (Supelco 20228 400/200 mg) for 30 days. GHG samples were collected every 30 days using a 10-mL polypropylene container coupled to a 0.2-μm PTFE filter syringe and immediately analysed. The extraction of charcoal cartridges was performed by the addition of 1000 μL of ACS-grade dichloromethane (SigmaAldrich) at −10 °C in an ultrasonic bath for 10 min before chemical analysis to prevent volatilisation due to the exothermic nature of the desorption process. After 90 days of treatment, the soil inside each reactor was homogenised, and a 10-g sample was extracted by Soxhlet using 250 mL of HPLC-grade cyclohexane (Tedia) with 20 extraction cycles. 2.3 Chemical Analysis The VOCs and hydrocarbons in soil were analysed by gas chromatography with mass spectrometry detection (GC-MS) using a Varian 450-GC 220-MS using a Combi PAL automatic injector. A 1.0-μL sample was injected at 300 °C in a splitless mode using helium 5.0 at 1.0 mL min−1 onto a VF-5MS column (30 m, 0.25 μm and 0.25 mm). The temperature of the oven was initially 40 °C, was held for 4 min, was increased to 300 °C at

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10 °C min−1 and was held for 10 min. The mass spectrometer was operated in a scan mode (m/z 45–360) with a trap temperature of 250 °C and the transfer line and manifold at 280 and 40 °C, respectively. The quantification of the remaining hydrocarbons in soil was performed with a standard mixture (Chemservice TPH6JM Diesel Range Organics Mixture #2). The external standardisation was performed in triplicate with five calibration levels between 0.5 and 10.0 mg L−1 for each component from C10 to C25 with the acceptance criterion of a coefficient of determination (R2) of 0.98. For the VOC analysis, a standard mixture of pentane, hexane, heptane, octane, nonane, decane, undecane and dodecane was employed at concentrations of 0.5 to 5.0 mg L−1 in triplicate with an acceptance criterion of R2 greater than 0.98. The injection temperature was 120 °C, and the conditions were the same as those used for the C10 to C25 analyses. The mass spectrometer was operated between m/z 45 and 200. GHG chemical analyses were also performed by gas chromatography using multiple detectors (Agilent 7890A). CH4 and CO2 were measured with a flame ionisation detector (FID), N2O with an electron capture detector (ECD) and CO2 at high levels by a thermal conductivity detector (TCD). The system uses two channels with 1/8″ (HayeSep Q80/100) packed columns. The first channel used two valves for the TCD and FID in series to measure CO2 using a methaniser to convert CH4 to CO2, which is measured by FID. The other channel used two valves to measure N2O by ECD. Two pre-columns were used to hold the heavy compounds and direct oxygen and water to purge. The sample was charged into a 1.0-mL loop maintained at 60 °C as the chromatographic column. The valves were kept at 100 °C, and FID, ECD and TCD were operated at 250, 350 and 200 °C, respectively. Helium 5.0 was used at 21 mL min−1 in all columns. Calibration was performed using five standard calibration gases (Linde Gas), with concentrations ranging from 351 to 551 μmol CO2 mol−1, 1.510 to 2.010 μmol CH4 mol−1 and 0.250 to 0.350 μmol N2O mol−1. The coefficients of determination for the calibration curves with triplicate injections were higher than 0.99 for CO2 and CH4 and higher than 0.98 for N2O. 2.4 Statistical Treatment of the Data The statistical packages SAS and SAEG were used to perform the Tukey test (comparison of means). A

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randomised factorial analysis was performed with the selected factors: (i) the repair strategy (AP, NA and BI) and (ii) the concentration of B5 diesel in soil (0.5, 2.0 and 4.0 %). The time from the beginning of the emission sampling (30, 60 and 90 days) was analysed separately and independently of the other two factors (recovery strategy and concentration of contaminants) to assess how the emissions changed over time. 2.5 Analysis of Fungi and Bacteria Microbiological analyses were conducted at the end of the treatment. The methodology used Petri plates and vials sterilised in an autoclave. The culture medium was prepared with Sabouraud (64 mg L−1), agar solution (2.5 mg L−1) and NaCl solution (0.085 %w/v). The agarised soil-saline solution was prepared by adding 9.0 mL of NaCl solution to 1.0 g of soil. The following dilutions were prepared: 1:1000 for the BI reactor and 1:100 for the AP and NA reactors. Next, the mixture was poured in the culture medium in Petri plates (inert atmosphere). Incubation was conducted at 28 °C for 48 h. After incubation, the colonies were counted.

instrumental technique (ICP-AES). Microbiological analyses of the soil were conducted, and the biostimulation process for BI reactors and sterilisation for AP reactors were considered satisfactory. Soil characteristics are present in Table 1. 3.2 Temperature The temperature reached by the reactors during treatment showed no significant variation. The highest temperature was observed for BI reactors at the end of the experiment, but these reactors did not exceed 52 °C. This can be explained by the high presence of microorganisms in BI reactors. In other reactors, the temperature did not exceed 32 °C for NA reactors and 24 °C for AP reactors (at room temperature, controlled at 25 °C). 3.3 Analysis of Fungi and Bacteria The microbiota was quantified, and the results can be viewed in Table 2. Some authors, such as Trevors Table 1 Soil physical-chemical characteristics Parameter

3 Results and Discussion 3.1 Soil Characterisation

pH in water

5.30

pH in KCl 1.0 mol L−1

4.41

Grain size

The soil from the COMPERJ area has a sandy texture, with 120 g kg−1 of clay and 798 g kg−1 of sand. It was characterised as Cambisol, with the development of an incipient B horizon surface at 0 to 20 cm. The elemental analysis of this soil indicated a low concentration of organic carbon (8.4 g kg−1), and the C/N ratio was consistent with well-moistened soil organic matter (10). Its acidic pH (5.3), low saturation (8 %), high aluminium saturation (58 %) and low phosphorus content are consistent with the requirements of tropical soil. In this context, the high aluminium concentration found in the sample can facilitate aerobic biodegradation by acting as an electron acceptor (Jones et al. 2001; Brynhildsen and Rosswall 1997). Regarding the extraction of other metals by Mehlich solution (0.05 mol L−1HCl+0.0125 mol L−1H2SO4), the levels of Fe, Mn, Zn and Cu were within the range found in the state of Rio de Janeiro (EMBRAPA 2002), as were the levels of Cr, Cd and Pb (EMBRAPA 2002). The Co and Ni contents were below the detection limit of the

Value

2.0–20 mm (55.8 %) 0.05–2.0 mm (24.0 %) 0.002–0.05 mm (8.20 %)