The influence of nickel on the bioremediation of multi-component contaminated tropical soil: microcosm and batch bioreactor studies

Abstract

Large petrochemical discharges are responsible for organic and inorganic pollutants in the environment. The purpose of this study was to evaluate the influence of nickel, one of the most abundant inorganic element in crude oil and the main component of hydrogen catalysts for oil refining, on the microbial community structure in artificially petroleum-contaminated microcosms and in solid phase bioreactor studies. In the presence of metals, the oil biodegradation in microcosms was significantly delayed during the first 7 days of operation. Also, increasing amounts of moisture generated a positive influence on the biodegradation processes. The oil concentration, exhibiting the most negative influence at the end of the treatment period. Molecular fingerprinting analyses (denaturing gradient gel electrophoresis--DGGE) indicated that the inclusion of nickel into the contaminated soil promoted direct changes to the microbial community structure. By the end of the experiments, the results of the total petroleum hydrocarbons removal in the bioreactor and the microcosm were similar, but reductions in the treatment times were observed with the bioreactor experiments. An analysis of the microbial community structure by DGGE using various markers showed distinct behaviors between two treatments containing high nickel concentrations. The main conclusion of this study was that Nickel promotes a significant delay in oil biodegradation, despite having only a minor effect over the microbial community.

Effect of nickel in the degradation of oil in soils contaminated with petroleum and nickel

“…In order to mimic the conditions found in an accidental spill of oil on soil samples we have used soil samples from an area of on shore oil extraction in the city of Carmópolis(state of Sergipe) in the northeast of Brazil (10° 38' 44.13"S, 36° 57' 41.81"W) and used crude oil obtained in the area (paraffin oil °API 24.1-average organic composition: 55.00 % saturated, 20.46 % aromatics, 24.72 % asphaltenic compounds)(N. F. Taketani et al, 2015). We have chosen to use nickel as our model heavy metal because it is common constituent of oil and is also widely used during the process of refining as a catalyst..…”

“…The total concentration of hydrocarbons in soil was quantified using infrared spectrometry (Infracal®, model HART-T, Wilks Enterprise, Inc, Connecticut, USA) using hexane as the extractor as described previously (N. F. Taketani et al, 2015).A standard curve was constructed with a serial dilution of the same oil used in the microcosm and was measured each time the analysis was performed. Controls using sterile soil were used to evaluate the loss of hydrocarbons due to chemical and physical processes which was below the limits of detection of the technique and was considered negligible.…”

“…Heavy metals and polycyclic aromatic hydrocarbons (PAH) have an adverse effecton the microbial community of different soils using dehydrogenase activity in relation to varying quantities of organic matter found in each soil type (Irha, Slet, & Petersell, 2003 Taketani et al, 2015).…”

“…In order to explain the inhibition of biodegradation of monoaromatic hydrocarbons by the presence of heavy metals, Amor et al, (2001) tested many heavy metals (zinc, nickel and cadmium) for inhibiting the degradation of toluene in a culture medium and obtained the result that nickel is the metal with the greater negative influence, followed by cadmium and finally zinc. This metal also promotes a delay in the biodegradation of crude oil, but changes on microbial populations suggest an adaptation to the presence of the metal in the environment(N. F. Taketani et al, 2015).…”

“…Li et al, 2015). Since the soil matrix is capable of binding the nickel ions and thus make it less available to the soil microorganisms, microbial communities from different soils respond differently to this stress(Li et al, 2015; N. F Taketani et al, 2015)…”