Fertility Deterioration in a Remediated Petroleum-Contaminated Soil

Evaluation of the lipase from castor bean (Ricinus Communis L.) as a potential agent for the remediation of used lubricating oil contaminated soils

Bioremediation of hydrocarbons-contaminated soils, using enzymes, is considered an alternative technology for soil remediation, obtaining shorter remediation times, greater removal efficiencies, and less waste generation. The lipases from invasive plants such as castor bean (Ricinus Communis L.) could represent an opportunity for its application in this purpose. This paper reports the results of evaluating enzymatic treatment at different conditions for the remediation of used lubricating oil-contaminated soils. Four assays were performed for the removal of the contaminant in a soil sample: (1) natural attenuation and (2) biostimulation with urea (10% w/v), both used as blanks, (3) enzymatic treatment with lipases at ambient conditions (room temperature, soil pH) and (4) enzymatic treatment with lipases at ideal conditions (temperature 37 °C, pH 4.5). After seven weeks of treatment, removal percentages of 14.23 ± 1.92%, 35.71 ± 5.17%, 14.11 ± 6.71%, and 94.26 ± 1.91%, respectively, were obtained. The degradation of the contaminant was analyzed by Fourier-transform Infrared spectroscopy (FTIR) for each assay. Results show the potential of the lipases for catalyzing the degradation of this contaminant in the soil at ideal conditions, representing an alternative technology to be applied as treatment ex-situ. This paper is the first study known to show the utilization of castor bean lipase for the remediation of hydrocarbons-contaminated soils.

Trace Element Contents in Petrol-Contaminated Soil Following the Application of Compost and Mineral Materials

The global use of petroleum hydrocarbons as raw materials and an energy source in industry results in serious environmental, health, and ecological problems. Consequently, there is growing interest in the development of technologies for the rehabilitation of contaminated areas. This study was undertaken in order to determine the effect of different phytostabilising materials (compost, bentonite, and CaO) on the trace element content in soil contaminated with unleaded petroleum 95 (0, 2.5, 5, and 10 cm³ kg⁻¹ of soil). The doses of petroleum applied to the soil were based on the previously conducted preliminary experiment. The highest petroleum dose (10 cm³ kg⁻¹ of soil) significantly reduced the chromium, zinc, and cobalt contents in the soil. Petroleum increased the cadmium, lead, nickel, and copper contents in the soil. The materials used for phytostabilisation (compost, bentonite, calcium oxide) had a significant effect on the trace element content in the soil. The application of mineral materials (bentonite and calcium oxide) was more effective than the application of compost, compared to the control series (without soil amendments) as they reduced the contents of cadmium, chromium, nickel, and cobalt in the soil to the greatest extent. The reduction effect of bentonite and calcium oxide on the content of these trace elements in the soil was stronger than compost.

Phytoremediation of crude oil contaminated soil using Sudanese plant species Acacia sieberiana Tausch

Phytoremediation is a new technology for cleaning contaminated soil with crude oil. Oil pollution is a serious problem worldwide; the aim of this study was to use the plant for Phytoremediation. Leguminous plant Acacia seiberiana Tausch was tested for it is efficiency to remediate soil polluted with 0.5, 1, 1.5 and 2% (w/w) crude oil and it is the ability to enhance the activity of soil microorganisms. Plant parameters, degradation percentage, Total Petroleum Hydrocarbon and bacterial count were measured. Results showed that the concentration of the crude oil did not affect plant growth indicating the significant success of the Phytoremediation process. Shoot length and shoot and root weights have not been negatively affected by oil, compared to the control plant, up to a concentration of 1.5% for up to six months. Crude oil degradation percentages were found to be in the range of 49-79%. The highest degradation percentage was recorded for the soil collected from underneath A. sieberiana Tausch seedlings (79%). A total of 81 different hydrocarbons were detected in soil samples at zero time and most of them were found to be of long (≥30 carbon atoms) and moderate (10-29 C) hydrocarbon chains. Fraction analyses were conducted in plant A. sieberiana Tausch seedlings at intervals of 60, 120 and 180 days of incubation, six different hydrocarbons were detected. The most abundant hydrocarbon detected were Heneicosane (21 C), Tetracosane (24 C) and Octacosane (28 C). The viable microorganism's count in oil-contaminated soil at any of the concentrations tested was significantly (P ≤ 0.01) higher than that in oil-free soil at any sampling interval. High efficiency of biodegradation was achieved using A. seiberiana Tausch indicating the unique mechanism of this plant in remediating contaminated soil with crude oil.

Risk Analysis of Heavy Metal Accumulation from Sewage Sludge of Selected Wastewater Treatment Plants in Poland

Sewage sludge (SS) from wastewater treatment plants (WWTPs) has important soil-forming and fertilizing properties. However, it may not always be used for this purpose. One of the main reasons why SS cannot be used for natural purposes is its heavy metal (HM) content. SS from the wastewater treatment plant in Poland was subjected to an analysis of the potential anthropogenic hazard of HMs, especially in terms of their mobility and accumulation in soil. Calculations were made for the concentrations of HMs in SS from the analyzed wastewater treatment plants and in arable soil from measurement points in places of its potential use. The geoaccumulation index (GAI), potential environmental risk index (PERI), risk assessment code (RAC) and environmental risk determinant (ERD) were calculated. Then the values of the indicators were compared with the mobility of HMs, which was the highest risk of soil contamination. It was shown that a high level of potential risk and geoaccumulation indicators did not necessarily disqualify the use of SS, provided that HMs were in immovable fractions.

Soil Odor as An Extra-Official Criterion for Qualifying Remediation Projects of Crude Oil-Contaminated Soil

Unfortunately, many property owners in southeastern Mexico do not trust environmental authorities, and the de facto method they use to evaluate the progress in environmental remediation projects is soil smell. This criterion was evaluated to determine if it was reliable to assess soil fertility and toxicity. Three soils (Fluvisol, Gleysol, and Arenosol), were contaminated with 2% medium or heavy crude oil (30.2, 17.1°API, respectively), and treated for 18 months to simulate bioremediation or natural attenuation. Every two months, field capacity, water repellency, hydrocarbon concentration, acute toxicity and soil odor were measured. Odor was measured in controlled conditions with a group of unexperienced panelists. During remediation, the Fluvisol and Gleysol were perceived to have an odor intensity between slight to low, and were considered acceptable. Meanwhile, in the Arenosol, the odor intensity was between low to medium and was considered unacceptable. After treatment, the hydrocarbon concentration was reduced to low levels, very near Mexican norm, and all the soils, including the Arenosol, were perceived to have an intensity between neutral to slightly agreeable, were considered acceptable, and no toxicity was observed in the earthworm bioassay (no false positives). However, in various soil samples from the Fluvisol and Arenosol, important risks were present with respect to field capacity and water repellency. Due to these observations, even though soil smell may be a trustworthy guide to soil toxicity, it does not ensure that the remediated soil’s fertility has been restored.