[pt] A atual situação de inconformidade de grande parte do Brasil em relação às diretrizes ambientais estabelecidas através da Resolução CONAMA número 420/2009 deixa claro os muitos desafios ainda existentes no âmbito do gerenciamento de áreas contaminadas. A análise de um caso real de remediação de uma planta industrial localizada no estado do Rio de Janeiro mostra como técnicas tradicionais de investigação ambiental, hoje consideradas ferramentas limitadas, foram e ainda são a principal base utilizada para a coleta de dados e subsequente tomada de decisões acerca do gerenciamento da área. O site em questão teve sua investigação ambiental iniciada ao final dos anos 90, realizada principalmente através de múltiplas campanhas de amostragem de solo e instalação de poços de monitoramento, identificando NAPLs (Non-aqueous phase liquids) como contaminantes de interesse. A planta industrial permanece sob intervenção há mais de dez anos sem aplicação de novas ferramentas de caracterização ambiental para aprimoração do modelo conceitual da área (CSM). A recente perda de eficiência do sistema de extração bifásica utilizado no local levou à implementação de técnicas de biorremediação estimulada in situ. Relatórios de desempenho mostram eficácia mais lenta do que o previsto, o que pode indicar um CSM deficiente em informações essenciais sobre as características físicas do meio e distribuição dos contaminantes neste. Dessa forma, sugere-se a caracterização em alta-resolução das porções mais impactadas da área de estudo, permitindo um aprimoramento do modelo conceitual da área e a otimização dos processos de remediação utilizados. / [en] Contaminated sites are those in which chemical substances that are potentially harmful to humans or the environment are present in higher concentrations than human established limits or their naturally occurring amounts (Resolução CONAMA number 420, 2009).
Issues related to contaminated areas are deeply related to the fast-growing population on urban centers and the historical expansion of industrial and commercial activities near those (Sánchez, 2004). The importance of managing contaminated sites became clear after events such as the Love Canal disaster exposed how damaging they could be if left unattended, causing huge, permanent impacts both on human health and the environment (IPT, 2004).
The vast array of chemicals used in the many existing industrial, commercial and agricultural activities include many potential contaminants of different physical and chemical nature. One distinct group of contaminants of particular interest are the NAPL (non-aqueous phase liquids), which include substances that when in direct contact with water form a distinct, immiscible phase. Two NAPL subcategories also exist based on their density relatively to water s: LNAPLs (light non-aqueous phase liquids), for those whose density is lower than water s, and DNAPLs (dense non-aqueous phase liquids), for those whose density is higher than water s. Since contaminants are mostly released near surface levels and migrate downwards due to gravity, their density is of great importance since it dictates their behavior when in contact with groundwater. NAPLs can be present in the environment in different physical forms, called phases (Huling and Weaver, 1991). These substances can dynamically change between phases depending on chemical and physical conditions, making them
potential sources of long-term contamination if not correctly addressed (ITRC, 2009a). DNAPLs demand particular attention since they are capable of penetrating further downward after contacting capillary zones and the water table, and will only stop vertical movement when it encounters a material with low enough permeability to block it or it reaches residual saturation levels. This behavior often generates really complex contaminant distribution patterns that are exceptionally hard to map or predict, making targeting them with investigation or remedial actions a difficult task.
Identifying and analyzing a potentially contaminated area usually relies on three main investigation steps: the preliminary, confirmatory and detailed investigations. Each step focuses on obtaining information from distinct sources and of different detail levels. The preliminary investigation focuses on gathering all existing information about a given area, including historical data about previous activities developed on or near it. The confirmatory step takes place if the preliminary analysis suggests that contamination may have happened, and focuses on obtaining more specific signs of it, such as altered fauna or flora, unusual smells and leakage of liquids or gases. This step may already employ basic investigation and analytical tools to gather and analyze samples. Then, if contamination is confirmed, the detailed investigation takes place in order to obtain specific data about physical properties of the affected area and chemical profiles of the contaminants. This step usually employs a variety of tools and techniques to allow collection of samples on the subsurface, as well as modelling the results in maps and 3D schemes.
All the information obtained throughout the investigation steps is used to construct what is called a conceptual site model (CSM). The CSM is a collection of data about a given site, organized in ways that help responsible parties to identify meaningful information about present contaminants and their distribution, the lateral and vertical extent of the affected area, possible pathways to human or animal exposure, underground water flow rates, and many other parameters and pieces of information that may be valuable when it comes to making decisions about the site. The CSM is the primary tool used by decision makers to support their actions.
Building a CSM relies heavily on data collected by different investigation techniques, the most traditional ones being soil sampling and the installation of aquifer monitoring wells. A wide array of high-resolution site characterization (HRSC) techniques has been developed throughout the years in order to allow a more precise definition of parameters, thus helping the CSM be as representative as possible of the actual conditions of a site. It is known that traditional techniques do not offer the necessary means to obtain high levels of detail when gathering data. This, paired with the acknowledgment that contaminated media are mostly heterogeneous by nature, made it even clearer that multiple techniques should be employed and their data used collaboratively for successfully approaching contaminated sites (Ryis, 2012; Suthersan, 2015; Derrite, 2017; Milani, 2017).
In many countries, high-resolution techniques have been used widely in many projects for years now, with proven ability to provide higher levels of detail that is essential to complement traditional techniques. The increased usage of these tools is seen as a cooperative effort between private contractors and public entities and agencies (EPA, 2003b). The development of clear guidelines and legal frameworks are necessary when it comes to shifting from traditional investigation methods to newer, higher-resolution ones. Even whole methodologies such as the Triad have emerged as a much more efficient way of addressing contaminated sites, given that responsible parties have the adequate training and tools available. Triad requires an extensive planning phase in order to identify key decision-making points and possible setbacks during the whole project. It also relies on the usage of HRSC techniques that allow real-time data managing in order to make investigation campaigns as efficient as possible, both cost- and time-wise.
In Brazil, there is still a lot of ground to cover in this matter. Only by 2009 the federal government issued a resolution including basic guidelines and goals for regional agencies for dealing with contaminated areas. Some local agencies, though, such as the Companhia Ambiental do Estado de São Paulo (CETESB), have been developing technical guidelines and legal framework for contaminated areas since the 1990s. A survey undertaken in 2015 with data gathered from local
environmental agencies of each one of the 26 brazilian states showed that most of them were still non-compliant to basic steps such as the creation of contaminated site registries. By 2017, only São Paulo state officially recognized and suggested the use of HRSC in cases with complexities related to the contaminants or physical media. Low levels of demand from local environmental agencies together with scarce technical guidelines and scientific publications ends up limiting the rate at which HRSC is implemented throughout the country. The result is that many complex sites are still mainly addressed by traditional investigation and remediation techniques, leading to long and costly remediation projects that often struggle or fail to meet their goals (IPT, 2014).
This study s goal is to present an overview of the management process of a contaminated site in Resende, a small city in Rio de Janeiro state, Brazil, which has been under intervention for over 10 years now and is still facing difficulties to meet its cleanup goals. The site has complexities associated with both the porous media and contaminants present, and yet hasn t employed any HRSC technique to help refine its original conceptual model. Questions are raised about whether the struggle to meet the established goals is possibly related to a poorly detailed CSM that may need further refinement.
| Identifer | oai:union.ndltd.org:puc-rio.br/oai:MAXWELL.puc-rio.br:55210 |
| Date | 05 October 2021 |
| Creators | MARCELO REITOR DE CASTRO FARIA |
| Contributors | ANA CRISTINA MALHEIROS GONCALVES CARVALHO, ANA CRISTINA MALHEIROS GONCALVES CARVALHO |
| Publisher | MAXWELL |
| Source Sets | PUC Rio |
| Language | Portuguese |
| Detected Language | English |
| Type | TEXTO |
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