Design of a central tool for sustainability evaluation and weighting to decision-making support of contaminated soils remediation.

Sustainable remediation remains unstandardized and ambiguously regulated, thereby limiting its adoption in the management of contaminated areas. Although a considerable number of tools are available for this purpose, numerous shortcomings continue to be detected, especially with regard to the integration of a complete assessment of impact and sustainability into a single framework. In view of these problems, the objective in this study was to develop and validate an integrated tool for assessing the sustainability of remediation techniques for contaminated soils. To support the sustainability analysis, were prepared impact assessment matrices, which list components and criteria for obtaining integrated impact scores for each sustainability dimension/pillar (i.e., social, economic, and environmental), factor, and component. These impact scores were incorporated and fitted into a mathematical model used to ascertain the sustainability of the techniques. The tool was subsequently validated by comparing and analyzing the sustainability with which five techniques: phytoremediation, electrokinetics and excavation/disposal (Case Study I), nanoremediation and soil washing (Case Study II). The techniques' probabilities of sustainability followed the order presented in the preceding statement. The determination of sustainability was supported by the direct interaction between the effects derived under each dimension and technique. These findings led to the conclusion that the proposed tool prioritizes the basic principles of sustainability, which call for harmony among the three pillars, and that it is a favorable instrument for the evaluation and selection of a sustainable remediation technique.

Optimization of biocementation responses by artificial neural network and random forest in comparison to response surface methodology.

In this article, the optimization of the specific urease activity (SUA) and the calcium carbonate (CaCO3) using microbially induced calcite precipitation (MICP) was compared to optimization using three algorithms based on machine learning: random forest regressor, artificial neural networks (ANNs), and multivariate linear regression. This study applied the techniques in two existing response surface method (RSM) experiments involving MICP technique. Random forest-based models and artificial neural network-based models were submitted through the optimization of hyperparameters via cross-validation technique and grid search, to select the best-optimized model. For this study, the random forest-based algorithm is aimed at having the best performance of 0.9381 and 0.9463 in comparison to the original r2 of 0.9021 and 0.8530, respectively. This study is aimed at exploring the capability of using machine learning-based models in small datasets for the purpose of optimization of experimental variables in MICP technique and the meaningfulness of the models by their specificities in the small experimental datasets applied to experimental designs. This study is aimed at exploring the capability of using machine learning-based models in small datasets for experimental variable optimization in MICP technique. The use of these techniques can create prerogatives to scale and mitigate costs in future experiments associated to the field.

Toxicity of nZVI in the growth of bacteria present in contaminated soil.

The use of nano zero-valent iron (nZVI) for the remediation of degraded areas is a consolidated practice. However, the long-term reactions that occur in the environment remain unknown. This study aimed to evaluate the potential toxic effects on the growth of colony-forming units (CFUs) of Bacillus cereus and Pseudomona aeruginosa present in soil contaminated with hexavalent chromium (Cr6+) and pentachlorophenol (PCP) nanoremediated with nZVI. The treatments were natural soil (control), soil contaminated by Cr6+, soil contaminated by PCP, and soil contaminated by Cr6+ and PCP (Cr6+ and PCP), all in duplicate. The concentration of contaminants used was 100 mg/kg of soil. One of the drums of the duplicate received an injection of nZVI solution with a concentration of 50 g/kg. Analysis was performed 7, 15, 21, 30, 60, and 90 days after the nZVI injection. Temporary oscillations in the abundance of the microbiological community were observed, characterizing the adaptation of bacteria to the contaminants. The bacteria showed similar behavior. Ninety days after the injection of nZVI, the averages of the CFUs were statistically equal, with the lowest coefficient of variation and the highest concentration of CFUs occurring. The strains of B. cereus and P. aeruginosa were resistant to the concentrations of nZVI, Cr6+, and PCP. The nanoremediation of nZVI in soil contaminated by Cr6+ and PCP had no toxic effects on the population of the bacteria evaluated and did not present major disturbances in temperature, electrical conductivity, pH, and humidity over time.

Social life cycle assessment of the nanoscale zero-valent iron synthesis process for application in contaminated site remediation.

Nanoscale zero-valent iron (nZVI) is the main nanomaterial used in environmental remediation processes. However, as with any remediation technique, the production and the use of nanomaterials can also cause environmental, economic, and social impacts. Thus, the present study investigated the social life cycle analysis (S-LCA) of nZVI production methods applied in environmental remediation. Three production methods of nZVI were selected for analysis: milling, reduction with sodium borohydride, and reduction with hydrogen gas. The social life cycle analysis was developed based on the ISO 14040 standard steps. Limits of the S-LCA system involve the stages of raw material extraction and manufacturing when not considering the use of nZVI postproduction. The analysis of social impact was conducted considering the involved stakeholders, through the application and improvement of an existing methodology and through the following procedures: characterization of social indicators according to a normalized scale, identification of the normalization factor for the indicators, employment of a social questionnaire, calculation of the total points in each impact subcategory (midpoint), calculation of the total points in the impact categories (endpoint), and calculation of the Social Index. The three production methods of nZVI result in significantly equal Social Indices. All methods were classified as socially sustainable according to the implemented methodology. The sensitivity analysis demonstrates the results dependent with the geographic location of the inventory data, while changes in the weighting can affect the Social Index results. Overall, this study significantly contributed to the state-of-the-art application of S-LCA in studies using nanomaterials; however, several limitations were also observed, and thus, steps for future development were suggested to future researches. In addition, this study improved the S-LCA methodology which can be used to assess the social impact of any product.

Global sales and operations planning: A multinational manufacturing company perspective.

The purpose of this paper is to analyse the global Sales and Operations Planning (S&OP) process and investigate the steps to support consolidated business planning in worldwide operations and large-scale supply chains. The paper conducts a case study at a multinational manufacturing company applying an abductive approach. It combines the deductive logic from theory and the inductive logic from field observation in an attempt to elaborate further on theory on global S&OP. The analysis is structured and guided by a novel framework for global S&OP, which is developed based on the theoretical background and the case study findings. The research findings characterise the S&OP process for global operations and identify challenges related to the need to synchronise the subsidiaries' S&OP efforts worldwide to deal with different contingencies of these subsidiaries, and to manage and analyse a large amount of information gathered. The research reveals how the subsidiaries' performance is analysed by top executives along the global S&OP process, feeding strategic initiatives in the organisation and identifying business opportunities like benchmarking among subsidiaries, synergies with other management practices, and global gains. This paper offers a novel investigation of the global steps on S&OP in a real-life setting, offering a well-documented characterisation of the process that goes beyond the traditional local approach. Moreover, it is the first study to reveal challenges and expected outcomes of such a global perspective for S&OP. The theoretical advancements of S&OP research offered herein aid scholars, opening avenues for middle-range theorising, highlighting the cross-disciplinary nature of the domain, and discussing the use of concepts from related disciplines like Economics, Psychology, and Information Systems. The research findings can also assist executives, especially from multinational manufacturers, in their efforts to consolidate global planning.

Improving the Bioremediation and in situ Production of Biocompounds of a Biodiesel-Contaminated Soil.

We aimed to produce simultaneously biosurfactants and lipases in solid state fermentation (SSF) using Aspergillus niger, followed by the use of the fermented media on the bioremediation of oily contaminated soil, in order to valuate agro industrial residuals and reduce the contamination. The biocompounds were produced using wheat bran and corncob (80:20), 5% of soybean oil and 0.5% of sugar cane molasses in SSF for 4 d, producing 4.58 ± 0.69 UE of emulsifying activity and 7.77 ± 1.52 U of lipolytic activity. This fermented media was used in the bioremediation of a 20% biodiesel contaminated soil, evaluating for 90 d microbial growth, contaminant degradation, and production of lipases and biosurfactants in soils. Six experimental strategies (natural attenuation; biostimulation + bioaugmentation + biocompounds; biostimulation + biosurfactant; biocompounds extract; biostimulation; adsorption of contaminant) were realized. The highest degradation of contaminant was verified in 90 d, of 74.40 ± 1.76%, and the production of biosurfactants and lipases in situ in the soil was found in 30 d (6.02 ± 0.24% of reduction in surface tension and 6.62 ± 0.17 UL of lipid activity in soil) for the same experiment (biostimulation + bioaugmentation + biocompounds). The addition of biostimulation + biosurfactant promotes higher biodegradation (66.00 ± 0.92%) of the contaminant than the biocompounds extract (59.58 ± 0.34%). The use of a solid fermented culture medium containing both biocompounds was feasible for the treatment of contaminants, demonstrating the potential for environmental application without the need for purification processes.

Bacterial biosurfactant increases ex situ biodiesel bioremediation in clayey soil.

The contamination of soils by oily compounds has several environmental impacts, which can be reversed through bioremediation, using biosurfactants as auxiliaries in the biodegradation process. In this study, we aimed to perform ex situ bioremediation of biodiesel-contaminated soil using biosurfactants produced by Bacillus methylotrophicus. A crude biosurfactant was produced in a whey-based culture medium supplemented with nutrients and was later added to biodiesel-contaminated clayey soil. The produced lipopeptide biosurfactant could reduce the surface tension of the fermentation broth to 30.2 mN/m. An increase in the microbial population was observed in the contaminated soil; this finding can be corroborated by the finding of increased CO2 release over days of bioremediation. Compared with natural attenuation, the addition of a lower concentration of the biosurfactant (0.5% w/w in relation to the mass of diesel oil) to the soil increased biodiesel removal by about 16% after 90 days. The added biosurfactant did not affect the retention of the contaminant in the soil, which is an important factor to be considered when applying in situ bioremediation technologies.

Life cycle sustainability assessment of the nanoscale zero-valent iron synthesis process for application in contaminated site remediation.

Nanoscale zero-valent iron (nZVI) is the main nanomaterial used in environmental remediation processes. The present study aims to evaluate the life cycle sustainability of nZVI production methods applied in environmental remediation. Three production methods of nZVI were selected for analysis: milling, liquid reduction with sodium borohydride, and chemical reduction with hydrogen gas (in two approaches: considering the goethite and hematite synthesis and after using in nZVI production and, using goethite and hematite particles already synthesized for nZVI production). The life cycle sustainability assessment was carried out based on a multi-criteria and multi-attribute analysis. The multi-criteria analysis was used to determine impact category preferences of different specialists in sustainability and remediation, and calculate the sustainability score through a linear additive model. Finally, a Monte Carlo simulation was used to quantify the results uncertainty. The functional unit considered was 1.00 kg of nZVI produced. The milling method and the hydrogen gas method in approach considering the use goethite and hematite particles already synthesized were the most sustainable. Moreover, the sustainability index was found to be influenced by the considered location scenarios as well as the perspectives of the different specialists, which was essential in producing a more accurate and comprehensive evaluation of the aforementioned sustainability methods. Overall, this study significantly contributed to applications of the state-of-the-art life cycle sustainability assessment in studies regarding nanomaterials, employing a simple methodology that included an analysis of different specialists. In addition, this is the first article that uses life cycle sustainability assessment in nanomaterials.

Nano scale zero valent iron production methods applied to contaminated sites remediation: An overview of production and environmental aspects.

The nano scale zero valent iron (nZVI) is the most used material in the remediation process. The inclusion of sustainability in the remediation process has also been gaining prominence. Sustainable remediation seeks to consider the environmental, economic and social impacts of remediation. Thus, this article aims to: (i) identify and describe nZVI production methods and (ii) evaluate their environmental aspects. Thus, this research was carried out in two stages. The first consisted of systematic bibliographical research to identify and describe nZVI production methods. In the second stage, an environmental analysis of the methods was performed considering the methodology of life cycle inventory assessment. Based on the inventory analysis, a classification of environmental aspects was performed, which included criteria, icons and a color scale. Nine nZVI production methods were identified, which comprised different technologies and processes. All methods had negative environmental aspects, such as high energy consumption, waste, wastewater generation and atmospheric emissions. In the classification of methods with regard to environmental aspects, the milling method had the best score, and the ultrasonic wave method the worst. Overall, this study contributes significantly to the detailed knowledge of nZVI synthesis methods in relation to production processes and their environmental aspects.

What factors predict length of stay in the intensive care unit? Systematic review and meta-analysis.

PURPOSE: Studies have shown that a small percentage of ICU patients have prolonged length of stay (LoS) and account for a large proportion of resource use. Therefore, the identification of prolonged stay patients can improve unit efficiency. In this study, we performed a systematic review and meta-analysis to understand the risk factors of ICU LoS. MATERIALS AND METHODS: We searched MEDLINE, Embase and Scopus databases from inception to November 2018. The searching process focused on papers presenting risk factors of ICU LoS. A meta-analysis was performed for studies reporting appropriate statistics. RESULTS: From 6906 citations, 113 met the eligibility criteria and were reviewed. A meta-analysis was performed for six factors from 28 papers and concluded that patients with mechanical ventilation, hypomagnesemia, delirium, and malnutrition tend to have longer stay, and that age and gender were not significant factors. CONCLUSIONS: This work suggested a list of risk factors that should be considered in prediction models for ICU LoS, as follows: severity scores, mechanical ventilation, hypomagnesemia, delirium, malnutrition, infection, trauma, red blood cells, and PaO2:FiO2. Our findings can be used by prediction models to improve their predictive capacity of prolonged stay patients, assisting in resource allocation, quality improvement actions, and benchmarking analysis.

Effects of homemade biosurfactant from Bacillus methylotrophicus on bioremediation efficiency of a clay soil contaminated with diesel oil.

Despite constant progress in the understanding of the mechanisms related to the effects of biosurfactants in the bioremediation processes of oily residues, the possibility of antagonist effects on microbial growth and the production in situ of these compounds must be elucidated. The aims of this work were a) to evaluate the effects of the addition of a homemade biosurfactant of Bacillus methylotrophicus on the microbial count in soil in order to determine the possibility of inhibitory effects, and b) to accomplish biostimulation using media prepared with whey and bioaugmentation with B. methylotrophicus, analyzing the effects on the bioremediation of diesel oil and evidencing the in situ production of biosurfactants through effects on surface tension. The homemade bacterial biosurfactant did not present inhibitory effects acting as a biostimulant until 4000 mg biosurfactant/kg of soil. The biostimulation and bioaugmentation presented similar better results (p > 0.05) with the degradation of oil (~60%) than natural attenuation due to the low quantities of biostimulants added. For bioaugmentated and biostimulated soils, a decrease of surface tension between 30 and 60 days was observed, indicating the production of tensoactives in the soil, which was not observed in natural attenuation or a control treatment.

Use of Nanoscale Zero-Valent Iron for Remediation of Clayey Soil Contaminated with Hexavalent Chromium: Batch and Column Tests.

This study investigated the reduction of hexavalent chromium (Cr(VI)) in a clayey residual soil using nanoscale zero-valent iron (nZVI). Five different ratios between nZVI and Cr(VI) were tested in batch tests (1000/11; 1000/23; 1000/35; 1000/70, and 1000/140 mg/mg) with the soil. With the selected proportion resulting best efficiency, the column tests were conducted, with molded specimens of 5 cm in diameter and 5 cm in height, with different nZVI injection pressures (10, 30, and 100 kPa). The soil was contaminated with 800 mg/kg of Cr(VI). The Cr(VI) and Cr(III) analyses were performed following the USEPA 3060A and USEPA 7196A standards. The results show that the reduction of Cr(VI) is dependent on the ratio between nZVI and Cr(VI), reaching 98% of efficiency. In column tests, the pressure of 30 kPa was the most efficient. As pressure increased, contaminant leaching increased. The permeability decreased over time due to the gradual increase in filtration and formation of oxyhydroxides, limiting nZVI mobility. Overall, nZVI is efficient for soil remediation with Cr(VI), but the injection process can spread the contaminated if not properly controlled during in situ application.

Influence of nanoscale zero-valent iron on hydraulic conductivity of a residual clayey soil and modeling of the filtration parameter.

Contaminated clay soils pose problems to public health and the environment in several parts of the world. Very little is known about the transport of decontaminating agents used in remediation process under natural, undisturbed conditions. Nanomaterials, especially those made of nanoscale zero-valent iron (nZVI), have been most frequently used for remediation of contaminated soils because of their higher reactivity, lower toxicity, and lower cost than other metallic nanoparticles. Even though the nanoparticle size is smaller than soil pores, clogging may occur over time due to agglomeration of nanoparticles, which could reduce the soil's natural permeability and thereby cause filtration of the nanoparticles. The use of a stabilizer in the nanoparticles can modify the reactivity but improves their mobility in the soil system. Thus, the objective of this work was to evaluate the hydraulic conductivity of residual clay soil under the injection of different types and concentrations of nZVI with and without surfactant stabilizer (NANOFER 25, NANOFER 25S, and NANOFER STAR in powder at 1 g/L, 4 g/L, 7 g/L, and 10 g/L concentrations), and to model transport of these nZVI suspensions in this soil system. Undisturbed cylindrical soil samples collected from the field were used, and hydraulic conductivity tests were performed using a column apparatus. The results showed that the presence of the stabilizer in the nZVI influenced the nanoparticles' mobility. The nZVI concentrations of 1 and 4 g/L did not affect the natural soil hydraulic conductivity. However, higher concentrations reduced the hydraulic conductivity value, which retarded the migration of nZVI as reflected in the value of filtration parameter.

Proposal for an optimized method for sustainable remediation evaluation and application: implementation of a multi-criteria process.

As sustainable remediation methods do not yet have a consolidated approach, a detailed assessment of the level of satisfaction for sustainability prospects is necessary. So, this study aims to evaluate the sustainability level of sustainable remediation methods according to the visions of decision makers in this field, in order to propose an optimized method that best represents its approach. We considered eight methods applied to sustainable remediation and nine decision criteria for evaluation. The analytical hierarchy process (AHP) of multi-criteria decision analysis (MCDA) was applied to judge and weigh the criteria by stakeholders. These weights were used to calculate the degrees of sustainability for all the methods, to classify these within a ranking, and to optimize the one that obtained the best performance. The results indicated that when the criteria were weighted, the criterion (C7), protection of human health and the environment in general, obtained the best placement, and the degree of sustainability achieved by each method indicates that ITRC (Interstate Technology and Regulatory Council) had the best performance. Finally, the proposal method resulted in an explicit approach of all the considered criteria. This article presents a new approach compared with those already applied in this context and provides more robust resources to examine to what extent the methods integrate the premises of sustainable remediation. Graphical Abstract .

Sustainable remediation through the risk management perspective and stakeholder involvement: A systematic and bibliometric view of the literature.

Sustainable remediation is a new way of thinking and acting in the management of contaminated sites. This research aims to identify and structure the state-of-the-art of sustainable remediation from the risk management and stakeholder involvement perspective. A systematic and bibliometric study of scientific production was performed on scientific papers indexed in the Scopus and Web of Science databases with the objectives: 1) to select a bibliographic portfolio that is aligned with the perception of the researchers in regard to theme, 2) to perform a bibliometric analysis of the selected bibliographic portfolio, and 3) to conduct a thematic synthesis and identify the integration of sustainable remediation from the risk management and stakeholder involvement perspective. The results indicated that although sustainable remediation is a recent theme it presents a promising field for development worldwide, verified by the growing number of publications in recent years. A change is observed in the way risk management is considered with the rise of sustainable remediation, demonstrated by different approaches in publications. Likewise, the involvement of stakeholders is widely discussed, and the importance of their participation in decision-making processes in the field of sustainable remediation is identified. This research brings several and new contributions as it provides with a detailed overview and guidance about the main characteristics and peculiarities as well as what already exists, the form to approach, the advances and what still needs to be improved so that the perception of stakeholders and risk management are better understood within the context of sustainable remediation.

Quantitative Assessment of Life Cycle Sustainability (QUALICS): Framework and its application to assess electrokinetic remediation.

In recent years, the broader environmental impacts of remediation that arise from different remediation activities has drawn attention of practitioners, remediation design professionals and academicians to evaluate the net environmental benefit of environmental remediation projects. The main objective of this paper is to describe the Quantitative Assessment of Life Cycle Sustainability (QUALICS) framework, a new tool developed to strengthen decision-making in the selection of sustainable remedial technologies for the clean-up of contaminated sites. The proposed framework is a combination of two multi-criteria evaluation methods namely, the Integrated Value Model for Sustainable Assessment (MIVES) and Analytic Hierarchy Process (AHP). The QUALICS uses a multi-criteria assessment framework to support decision-making in remediation projects. A description of the methodology adopted for sustainability assessment of alternative remedial strategies using QUALICS framework is presented in this study. In addition, a case study is discussed to demonstrate the application of the QUALICS framework for the sustainability assessment of different remediation options for clean-up of a contaminated site. The case study involves sustainability assessment of different remediation options namely, electrokinetic remediation (EKR), excavation/disposal, and phytoremediation for remediation of a contaminated site. A sensitivity analysis was also performed for the EKR option by varying different parameters including electrode materials, energy source, electrolyte used, to analyze their influence on the sustainability of the alternative remedial options. The proposed framework can also be applied to any project in general to quantify and compare the sustainability indices of each of the alternative options considered and thereby identify the most sustainable option.

Bibliometric study of the toxicology of nanoescale zero valent iron used in soil remediation.

The application of nanoscale zero-valent iron is one of the most widely used remediation technologies; however, the potential environmental risks of this technology are largely unknown. In order to broaden the knowledge on this subject, the present work consists of a bibliometric study of all of publications related to the toxicity of zero-valent iron nanoparticles used in soil remediation available from the Scopus (Elsevier) and Web of Science (Thompson Reuters) databases. This study presents a temporal distribution of the publications, the most cited articles, the authors who have made the greatest contribution to the theme, and the institutions, countries, and scientific journals that have published the most on this subject. The use of bibliometrics has allowed for the visualization of a panorama of the publications, providing an appropriate analysis to guide new research towards an effective contribution to science by filling the existing gaps. In particular, the lack of studies in several countries reveals a promising area for the development of further research on this topic.

Application of life cycle assessment as a tool for evaluating the sustainability of contaminated sites remediation: A systematic and bibliographic analysis.

As the discussion surrounding sustainable remediation has advanced, numerous tools have been developed to evaluate the sustainability of remediation technologies, including life cycle assessment (LCA). In the present study, a systematic and bibliometric analysis of scientific articles indexed in the databases of Scopus and the Web of Science in the field of LCA was performed, particularly studies relating to the remediation of contaminated sites from a sustainability perspective. We selected a bibliographic portfolio (BP) of papers related to sustainable remediation using LCA. Then, we performed a bibliometric analysis of the selected BP, presenting theoretical development, highlighting the authors, journals, and countries associated with these publications. Finally, we conducted a thematic synthesis and reviewed the prospects for future research. The BP was composed of 44 papers from 2007 to 2018. In 2018 there was the highest number of publications, corresponding to 27% of the total BP. The results showed that developed countries have generated the largest number of publications, whereas developing countries had lower representation in the BP. However, China stands out as the second country with the highest number of publications. The thematic analysis showed that most articles have aimed to assess the environmental impacts of remediation techniques. However, several publications have performed a broader analysis considering the economic and social pillars of sustainability through using LCA in conjunction with other tools. The study also highlights the main application of LCA in decision-making on the remediation processes in the context of sustainable remediation. The present research study makes several new contributions, providing academics and practitioners with an overview of the implementation of LCA in the field of sustainable remediation of contaminated sites through sorting published data according to scientific indexes and bibliometrics, describing the main research approaches, and highlighting prospects for new research.

Biosurfactants during in situ bioremediation: factors that influence the production and challenges in evalution.

Research on the influence of biosurfactants on the efficiency of in situ bioremediation of contaminated soil is continuously growing. Despite the constant progress in understanding the mechanisms involved in the effects of biosurfactants, there are still many factors that are not sufficiently elucidated. There is a lack of research on autochthonous or exogenous microbial metabolism when biostimulation or bioaugmentation is carried out to produce biosurfactants at contaminated sites. In addition, studies on the application of techniques that measure the biosurfactants produced in situ are needed. This is important because, although the positive influence of biosurfactants is often reported, there are also studies where no effect or negative effects have been observed. This review aimed to examine some studies on factors that can improve the production of biosurfactants in soils during in situ bioremediation. Moreover, this work reviews the methodologies that can be used for measuring the production of these biocomposts. We reviewed studies on the potential of biosurfactants to improve the bioremediation of hydrocarbons, as well as the limitations of methods for the production of these biomolecules by microorganisms in soil.

Biostimulation and rainfall infiltration: influence on retention of biodiesel in residual clayey soil.

This study investigates the retention of biodiesel in residual clayey soil during biostimulation by nutrients (nitrogen, phosphorus, and potassium) under conditions of rainfall infiltration. Several column tests were conducted in a laboratory under different void ratios (1.14, 1.24, and 1.34), varying moisture contents (15, 25, and 35%), and in both the presence and absence of biostimulation. The volume of biodiesel (which was equivalent to the volume of voids in the soil) was placed atop the soil and allowed to percolate for a period of 15 days. The soil was subjected to different rainfall infiltration conditions (0.30 or 60 mm). The greatest reductions in residual contaminants occurred after 60 mm of rain simulation, at values of up to 74% less than in samples with the same conditions but no precipitation. However, the residual contamination decay rate was greater with 0-30 mm (0.29 g/mm) of precipitation than with 30-60 mm (0.075 g/mm). Statistical assessment revealed that increased moisture and the presence of nutrients were the factors with the most powerful effect on contaminant retention in the soil. The residual contaminant level was 21 g/kg at a moisture content of 15% and no precipitation, decreasing to 12 g/kg at 35% moisture and no precipitation. Accordingly, it is possible to conclude that biostimulation and rainfall infiltration conditions can decrease the retention of contaminants in soil and allow a greater leaching or spreading of the contamination. All of these phenomena are worthy of careful examination for the in situ bioremediation of organic contamination. HIGHLIGHTS: • The higher moisture in the soil, due to a high initial moisture content and/or infiltration of rainfall, can reduce contaminant retention, • The use of biostimulation through the addition of nutrients to accelerate the biodegradation of toxic organic contaminants may induce inadvertent undesirable interactions between the soil and the contaminant. • When adopting biostimulation for bioremediation, the effects of rainfall should be addressed; ideally, it should be prevented from entering the affected site, in order to avoid increased contaminant leaching and potential spreading.