Determination of total petroleum hydrocarbons in soil from different locations using infrared spectrophotometry and gas chromatography

Total petroleum hydrocarbons (TPH) are important environmental contaminants which are toxic to human and environmental receptors. Several analytical methods have been used to quantify TPH levels in contaminated soils, specifically through infrared spectrometry (IR) and gas chromatography (GC). Despite being two of the most used techniques, some issues remain that have been inadequately studied: a) applicability of both techniques to soils contaminated with two distinct types of fuel (petrol and diesel), b) influence of the soil natural organic matter content on the results achieved by various analytical methods, and c) evaluation of the performance of both techniques in analyses of soils with different levels of contamination (presumably non-contaminated and potentially contaminated). The main objectives of this work were to answer these questions and to provide more complete information about the potentials and limitations of GC and IR techniques. The results led us to the following conclusions: a) IR analysis of soils contaminated with petrol is not suitable due to volatilisation losses, b) there is a significant influence of organic matter in IR analysis, and c) both techniques demonstrated the capacity to accurately quantify TPH in soils, irrespective of their contamination levels

Previsão do tempo de remediação de solos contaminados usando a extracção de vapor

Tese de doutoramento. Engenharia do Ambiente. Faculdade de Engenharia. Universidade do Porto, Departamento de Engenharia Química. Instituto Superior de Engenharia do Porto. 201

Green zero valent iron nanoparticles dispersion through a sandy column using different injection sequences

The contamination of soils is a global environmental problem that urges an increased effort to recover polluted sites. In Europe, there are an estimated 20,000 polluted sites that need to be remediated and around 350,000 sites that are classified as potentially contaminated by the European Environment Agency (EEA). Remediation is a part of the solution to this problem, requiring the most innovative and sustainable technologies. In this context, the use of zero valent iron nanoparticles (nZVI) is a promising, low cost and efficient technology for the remediation of soil and groundwater contaminated with a wide range of organic and inorganic pollutants. Among the nZVIs, the ones produced using Green synthesis methods (green nZVIs (gnZVI)) using natural extracts, such as green tea, are increasingly considered an alternative technology for the future. However, there are issues related to the application of gnZVI in soil that are still not fully understood, requiring further research, among these is the study of their transport in soils. Therefore, this work aims to study the transport of gnZVIs in sandy soils under diverse conditions such as soil particle size, soil saturation level and injection sequence. Several experiments were performed in an acrylic column with two sandy soils with different particle sizes (between 0.5 and 1.0 mm and higher than 1.0 mm), using two distinct water saturation conditions (saturated and dry) and four injection sequences. After these tests the distribution of the gnZVI along the soil column was determined by atomic absorption spectroscopy. This work allowed concluding that the injection sequence might be one of the most important factors influencing the rate of nZVI dispersion through a sandy column. According to the results it was possible to propose, for distinct types of contamination (deep, superficial, hot spot or dispersed), the most appropriate injection sequence.António Soares is grateful to REQUIMTE for his postdoctoral research grant (associated to Project UID/QUI/50006/2013), as well as to FCT/MEC for funding through national funds, co-financed by the Fundo Europeu de Desenvolvimento Regional (FEDER), in the context of the partnership agreement PT2020. The authors also thank “Fundação para a Ciência e a Tecnologia” (Project UID/QUI/50006/2013) for the financial support for this work.info:eu-repo/semantics/publishedVersio

Study on the changes of soil chemical characteristics as result of prescribed fire

Every year, particularly during the summer period, the Portuguese forests are devastated by forest fire that destroys their ecosystems. So in order to prevent these forest fires, public and private authorities frequently use methods for the reduction of combustible mass as the prescribed fire and the mechanical vegetation pruning. All of these methods of prevention of forest fires alter the vegetation layer and/or soil [1-2]. This work aimed the study of the variation of some chemical characteristics of soil that suffered prescribed fire. The studied an area was located in the Serra of Cabreira (Figure 1) with 54.6 ha. Twenty sampling points were randomly selected and samples were collected with a shovel before, just after the prescribed fire, and 125 and 196 days after that event. The parameters that were studied were: pH, soil moisture, organic matter and iron, magnesium and potassium total concentration. All the analysis followed International Standard Methodologies. This work allowed to conclude that: a) after the prescribed fire; i) the pH remained practically equal to the the initial value; ii) occurred a slight increase of the average of the organic matter contents and iron total contents; b) at the end of the sampling period compared to the initial values; i) the pH didn´t change significantly; ii) the average of the contents of organic matter decreased; and iii) the average of the total contents of Fe, Mg and K increased

Remediation of sandy soils contaminated with hydrocarbons and halogenated hydrocarbons by soil vapour extraction

This paper presents the study of the remediation of sandy soils containing six of the most common contaminants (benzene, toluene, ethylbenzene, xylene, trichloroethylene and perchloroethylene) using soil vapour extraction (SVE). The influence of soil water content on the process efficiency was evaluated considering the soil type and the contaminant. For artificially contaminated soils with negligible clay contents and natural organic matter it was concluded that: (i) all the remediation processes presented efficiencies above 92%; (ii) an increase of the soil water content led to a more time-consuming remediation; (iii) longer remediation periods were observed for contaminants with lower vapour pressures and lower water solubilities due to mass transfer limitations. Based on these results an easy and relatively fast procedure was developed for the prediction of the remediation times of real soils; 83% of the remediation times were predicted with relative deviations below 14%

Multiple Linear Regression and Artificial Neural Networks to Predict Time and Efficiency of Soil Vapor Extraction

The prediction of the time and the efficiency of the remediation of contaminated soils using soil vapor extraction remain a difficult challenge to the scientific community and consultants. This work reports the development of multiple linear regression and artificial neural network models to predict the remediation time and efficiency of soil vapor extractions performed in soils contaminated separately with benzene, toluene, ethylbenzene, xylene, trichloroethylene, and perchloroethylene. The results demonstrated that the artificial neural network approach presents better performances when compared with multiple linear regression models. The artificial neural network model allowed an accurate prediction of remediation time and efficiency based on only soil and pollutants characteristics, and consequently allowing a simple and quick previous evaluation of the process viability

LCA applied to nano scale zero valent iron synthesis

Purpose Application of zero valent iron nanoparticles is an innovative technology for ground water treatment and soil remediation. There are several methods to synthesise nano scale zero valent iron (nZVI), namely through bottom-up methods which consists on chemical reactions using strong reducing agents. In this work, the environmental impacts and costs were determined for two methods, namely the traditional one that uses sodium borohydride and the green method that uses extracts obtained from natural products. Methods The consideration of environment and economic aspects in the earlier stages of the synthesis processes and in the development of new materials is of great importance since it can help to decide if alternative methods are promising and should be further developed aiming more sustainable processes. In this work, life cycle assessment (LCA) was used as an ecodesign strategy evaluating environmental performance of the two synthesis methods, identifying critical stages of the synthesis processes of nZVI. An economic evaluation and a sensitivity analysis considering a different scenario for electricity production were also performed. Results and discussion The results obtained in this study showed that the green synthesis method presents lower environmental impacts than the traditional one, roughly 50% lower in the first scenario. In the second scenario, environmental impact of green synthesis corresponds to 38% of the environmental impact of traditional synthesis. In the green method, the critical stage is the extraction process which is closely related to the electricity production. In the traditional method, the reactant use is the critical stage that is related to the production of sodium borohydride. The economic evaluation indicated that the traditional synthesis method is much more expensive than the green synthesis (roughly eight times higher). Conclusions From the results obtained, it is possible to conclude that the green synthesis method presents lower environmental impacts in both scenarios and lower costs than the traditional synthesis.info:eu-repo/semantics/publishedVersio

Ecotoxicity of nanoscale zero-valent iron particles – a review

The use of nanoscale zero-valent iron particles (nZVIs) in the environmental remediation of water and soil is increasing. This increase is related to the higher reactivity and mobility of nZVIs compared with that of macro- or micro-sized iron particles.The introduction of nZVIs into the environment raises concerns related to their fate and effect on aquatic and terrestrial biota. Knowledge of these issues will allow a better understanding not only of the remediation process but also of the long-term effects and impact of nZVIs on ecosystems, leading to a safer and more efficient application of these particles. This paper presents the current state of play concerning the toxic effects of nZVIs on organisms at different stages of the food chain. The majority of studies show that nZVIs have a negative impact on bacteria, aquatic invertebrates, such as Daphnia magna, terrestrial organisms, such as Eisenia fetida, and seed germination. However, the number of published studies related to this issue is clearly insufficient. This reinforces the need for further research in order to specify the toxic concentrations of nZVIs that affect the most important target organisms. Furthermore, an evaluation of the effects of the coating of nanoparticles should also be pursued.Título-PT: Ecotoxicidade de nanopartículas de ferro zerovalente – Uma revisãoA utilização de nanopartículas de ferro zerovalente na remediação ambiental de águas e solos tem vindo a aumentar, suportado na maior reatividade e mobilidade destas partículas quando comparadas com outras de tamanho macro e micrométrico. A introdução destas partículas no ambiente tem levantado preocupações relativas ao destino e ao efeito em ambientes aquáticos e terrestes. Um maior conhecimento destas questões permitirá uma melhor compreensão do processo de remediação e das transformações a longo prazo e o impacto das nanopartículas de ferro zerovalente nos diferentes ecossistemas, permitindo uma aplicação mais segura e eficiente.Este trabalho apresenta o estado atual do conhecimento sobre os efeitos tóxicos das nanopartículas de ferro zerovalente em diferentes organismos nas várias fases da cadeia alimentar. Concluiu-se que os estudos realizados são insuficientes e que na sua maioria apontam no sentido do impacto negativo daquelas nanopartículas em bactérias, invertebrados aquáticos, organismos terrestes e em testes de germinação. Esta informação reforça a necessidade da realização de estudos complementares que especifiquem a concentração das nanopartículas de ferro zerovalente que se tornam tóxicas para organismos-alvo importantes; e a avaliação dos efeitos de nanopartículas revestidas

Dual augmentation for aerobic bioremediation of MTBE and TCE pollution in heavy metal-contaminated soil

In this work we isolated from soil and characterized several bacterial strains capable of either resisting high concentrations of heavy metals (Cd2+ or Hg2+ or Pb2+) or degrading the common soil and groundwater pollutants MTBE (methyl-tertbutyl ether) or TCE (trichloroethylene). We then used soil microcosms exposed to MTBE (50 mg/l) or TCE (50 mg/l) in the presence of one heavy metal (Cd 10 ppm or Hg 5 ppm or Pb 50 or 100 ppm) and two bacterial isolates at a time, a degrader plus a metalresistant strain. Some of these two-membered consortia showed degradation efficiencies well higher (49–182% higher) than those expected under the conditions employed, demonstrating the occurrence of a synergetic relationship between the strains used. Our results show the efficacy of the dual augmentation strategy for MTBE and TCE bioremediation in the presence of heavy metals

Characterization of green zero-valent iron nanoparticles produced with tree leaf extracts

In the last decades nanotechnology has become increasingly important because it offers indisputable advantages to almost every area of expertise, including environmental remediation. In this area the synthesis of highly reactive nanomaterials (e.g. zero-valent iron nanoparticles, nZVI) is gaining the attention of the scientific community, service providers and other stakeholders. The synthesis of nZVI by the recently developed green bottom-up method is extremely promising. However, the lack of information about the characteristics of the synthetized particles hinders a wider and more extensive application. This work aims to evaluate the characteristics of nZVI synthesized through the green method using leaves from different trees. Considering the requirements of a product for environmental remediation the following characteristics were studied: size, shape, reactivity and agglomeration tendency. The mulberry and pomegranate leaf extracts produced the smallest nZVIs (5–10 nm), the peach, pear and vine leaf extracts produced the most reactive nZVIs while the ones produced with passion fruit, medlar and cherry extracts did not settle at high nZVI concentrations (931 and 266 ppm). Considering all tests, the nZVIs obtained from medlar and vine leaf extracts are the ones that could present better performances in the environmental remediation. The information gathered in this paper will be useful to choose the most appropriate leaf extracts and operational conditions for the application of the green nZVIs in environmental remediation