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Researchers to study Arctic Spill Response and Clean-up

Researchers from Dalhousie University recently received $523,000 in Canadian federal government funding to investigate strategies to better separate oil from water and examine the risk of spills in the Canadian Arctic Archipeligo.

As climate change accelerates the melting of sea ice in the Arctic, the Northwest Passage could become a significant route between the Pacific and North Atlantic oceans. With the potential of increased Arctic vessel traffic, the Government of Canada is investing in science and research to ensure that we are prepared in an event of a spill.  

One research project funded under this program will test new methods to remove oil from water for greater efficiency during a cleanup. The other project will use advanced technology to help responders locate and identify spills, while minimizing harm to the marine environment. This new science and data will be important to inform decision makers and will help accelerate efficient decision making capacity. 

The two researchers that will be heading the investigation are Dr. Haibo Niu, and Dr. Lei Liu.

Dr. Niu currently works at the Department of Engineering, Dalhousie University. Haibo does research in Civil Engineering, Environmental Engineering and Ocean Engineering. His most recent research paper is entitled A Comprehensive System for Simulating Oil Spill Trajectory and Behaviour in Subsurface and Surface Water Environments.

For the Arctic research project, Dr. Niu is trying to develop a computer model that will predict the movement of an oil spill so responders know where it’s going and what it threatens.

Dr. Liu’s major research interests include coupled simulation-optimization modeling for groundwater management, site remediation system design, modeling of air/water/waste pollution control systems, and environmental risk assessment. He also has exposure to areas of regional environmental systems planning and management, climate-change impact assessment and adaptation planning, GIS and its application to environmental information systems, system dynamics, and uncertainty analysis.

The federal government is funding Dr. Liu’s project that will involve trying to find a way to use existing membrane technology to filter oil from oily waste water collected on board vessels during a spill cleanup. The goal is to create a unit carried on board to remove oil, allowing clean water to be discharged at sea rather than carried back to shore for treatment.

The projects are funded under the $45.5 million Multi-Partner Research Initiative, which aims provide the best scientific advice to respond to spills in Canadian waters. The initiative connects leading researchers both in Canada and around the world. These efforts will improve our knowledge of how spills behave, how to contain them and clean them up, and how to minimize their environmental impacts.

Nanoremediation of soil contaminated with Arsenic and Mercury

Researchers in Spain recently published a paper describing the utilization of nanoremediation technology to clean-up soil at the Brownfield site heavily contaminated with arsenic and mercury.

The research draws on a several lab-scale experiments that have shown the use of nanoscale zero-valent iron (nZVI) to be effective in reducing metal(loid) availability in polluted soils.

The core-shell model of zero-valent iron nanoparticles. The core consists of mainly zero-valent iron and provides the reducing power for reactions with environmental contaminants. The shell is largely iron oxides/hydroxides formed from the oxidation of zero-valent iron. The shell provides sites for chemical complex formation (e.g., chemosorption).

The researchers evaluated the capacity of nZVI for reducing the availability of As and Hg in brownfield soils at a pilot scale, and monitored the stability of the immobilization of these contaminants over a 32 month period. The researchers contend that their study is the first to apply nZVI to metal(loid)-polluted soils under field conditions.

In the study, two sub-areas (A and B) that differed in pollution load were selected, and a 5 m2 plot was treated with 2.5% nZVI (by weight) in each case (Nanofer 25S, NanoIron). In sub-area A, which had a greater degree of pollution, a second application was performed eight months after the first application.

Overall, the treatment significantly reduced the availability of both arsenic and (As) and mercury ((Hg), after only 72 h, although the effectiveness of the treatment was highly dependent on the degree of initial contamination.

Sub-area B (with a lower level of pollution) showed the best and most stable immobilization results, with As and Hg in toxicity characteristics leaching procedure (TCLP) extracts decreasing by 70% and 80%, respectively. In comparison, the concentrations of As and Hg in sub-area A decreased by 65% and 50%, respectively.

Based on the findings, the researchers contend that the use of nZVI at a dose of 2.5% appears to be an effective approach for the remediation of soils at this brownfield site, especially in sub-area B.

New Brunswick Marine Research Centre to study impact on spill clean-up chemicals on aquatic life

The Canadian Ministry of Fisheries, Oceans and the Canadian Coast Guard recently announced that it is investing $2.4 million in scientific research at the Huntsman Marine Science Centre in New Brunswick.

With this investment, the Centre will study how spill response measures, such as the use of dispersant chemicals, affect fish and other aquatic species of interest. The goal of the project is to ensure the use of effective response measures, without harming ocean life in the event of a spill.

The Huntsman Marine Science Centre is located in St. Andrews, New Brunswick. The Centre is engaged in a broad range of marine science and applied research initiatives.

Huntsman Marine Science Centre (Source: huntsmanmarine.ca)

Nature based solutions for contaminated land remediation and brownfield redevelopment in cities: A review

A collaboration of researchers from various Universities from around the world recently published a research paper in Science of the Total Environment that reviews nature based solutions for contaminated land remediation. The paper contends that Nature-based solutions (NBS) including phytoremediation and conversion of brownfield sites to public greenspaces, holds much promise in maximizing a sustainable urban renaissance.

The researchers claim that urban industrialization has caused severe land contamination at hundreds of thousands of sites in cities all around the world, posing a serious health risk to millions of people. The also state that many contaminated brownfield sites are being left abandoned due to the high cost of remediation.

Traditional physical and chemical remediation technologies also require high energy and resource input, and can result in loss of land functionality and cause secondary pollution.

NBS is an umbrella concept that can be used to capture nature based, cost effective and eco-friendly treatment technologies, as well as redevelopment strategies that are socially inclusive, economically viable, and with good public acceptance. The NBS concept is novel and in urgent need of new research to better understand the pros and cons, and to enhance its practicality.

The review article summarizes NBS’s main features, key technology choices, case studies, limitations, and future trends for urban contaminated land remediation and brownfield redevelopment.

Pyrolysis makes oil-soaked soil fertile again

As reported by David Ruth in Physics.org, researchers at Rice University in Texas have developed a method of decontaminating soil impacted with heavy oil and making it fertile again. Rice engineers Kyriacos Zygourakis and Pedro Alvarez and their colleagues have fine-tuned their method to remove petroleum contaminants from soil through pyrolysis. The technique gently heats soil while keeping oxygen out, which avoids the damage usually done to fertile soil when burning hydrocarbons cause temperature spikes.

While large-volume marine spills get most of the attention, 98 percent of oil spills occur on land, Alvarez points out, with more than 25,000 spills a year reported to the Environmental Protection Agency. That makes the need for cost-effective remediation clear, he said.

“We saw an opportunity to convert a liability, contaminated soil, into a commodity, fertile soil,” Alvarez said.

The key to retaining fertility is to preserve the soil’s essential clays, Zygourakis said. “Clays retain water, and if you raise the temperature too high, you basically destroy them,” he said. “If you exceed 500 degrees Celsius (900 degrees Fahrenheit), dehydration is irreversible.”

The researchers put soil samples from Hearne, Texas, contaminated in the lab with heavy crude, into a kiln to see what temperature best eliminated the most oil, and how long it took.

Their results showed heating samples in the rotating drum at 420 C (788 F) for 15 minutes eliminated 99.9 percent of total petroleum hydrocarbons (TPH) and 94.5 percent of polycyclic aromatic hydrocarbons (PAH), leaving the treated soils with roughly the same pollutant levels found in natural, uncontaminated soil.

The paper appears in the American Chemical Society journal Environmental Science and Technology. It follows several papers by the same group that detailed the mechanism by which pyrolysis removes contaminants and turns some of the unwanted hydrocarbons into char, while leaving behind soil almost as fertile as the original. “While heating soil to clean it isn’t a new process,” Zygourakis said, “we’ve proved we can do it quickly in a continuous reactor to remove TPH, and we’ve learned how to optimize the pyrolysis conditions to maximize contaminant removal while minimizing soil damage and loss of fertility.

“We also learned we can do it with less energy than other methods, and we have detoxified the soil so that we can safely put it back,” he said.

Heating the soil to about 420 C represents the sweet spot for treatment, Zygourakis said. Heating it to 470 C (878 F) did a marginally better job in removing contaminants, but used more energy and, more importantly, decreased the soil’s fertility to the degree that it could not be reused.

“Between 200 and 300 C (392-572 F), the light volatile compounds evaporate,” he said. “When you get to 350 to 400 C (662-752 F), you start breaking first the heteroatom bonds, and then carbon-carbon and carbon-hydrogen bonds triggering a sequence of radical reactions that convert heavier hydrocarbons to stable, low-reactivity char.”

The true test of the pilot program came when the researchers grew Simpson black-seeded lettuce, a variety for which petroleum is highly toxic, on the original clean soil, some contaminated soil and several pyrolyzed soils. While plants in the treated soils were a bit slower to start, they found that after 21 days, plants grown in pyrolyzed soil with fertilizer or simply water showed the same germination rates and had the same weight as those grown in clean soil.

Lettuce growing in once oil-contaminated soil revived by a process developed by Rice University engineers. The Rice team determined that pyrolyzing oil-soaked soil for 15 minutes at 420 degrees Celsius is sufficient to eliminate contaminants while preserving the soil’s fertility. The lettuce plants shown here, in treated and fertilized soil, showed robust growth over 14 days. Credit: Wen Song/Rice University

“We knew we had a process that effectively cleans up oil-contaminated soil and restores its fertility,” Zygourakis said. “But, had we truly detoxified the soil?”

To answer this final question, the Rice team turned to Bhagavatula Moorthy, a professor of neonatology at Baylor College of Medicine, who studies the effects of airborne contaminants on neonatal development. Moorthy and his lab found that extracts taken from oil-contaminated soils were toxic to human lung cells, while exposing the same cell lines to extracts from treated soils had no adverse effects. The study eased concerns that pyrolyzed soil could release airborne dust particles laced with highly toxic pollutants like PAHs.

”One important lesson we learned is that different treatment objectives for regulatory compliance, detoxification and soil-fertility restoration need not be mutually exclusive and can be simultaneously achieved,” Alvarez said.

Chemical and Biological Remediation Tetrachloroethene – Case Study

Tetrachloroethene is the systematic name for tetrachloroethylene, or perchloroethylene (“perc” or “PERC”), and many other names.  It is a manufactured chemical that is widely used in the dry-cleaning of fabrics, including clothes. It is also used for degreasing metal parts and in manufacturing other chemicals. Tetrachloroethene is found in consumer products, including some paint and spot removers, water repellents, brake and wood cleaners, glues, and suede protectors.

Tetrachloroethene is a common soil contaminant. With a specific gravity greater than 1, tetrachloroethylene will be present as a dense nonaqueous phase liquid(DNAPL) if sufficient quantities are released. Because of its mobility in groundwater, its toxicity at low levels, and its density (which causes it to sink below the water table), cleanup activities are more difficult than for oil spills (which has a specific gravity less than 1).

In the case study, researchers from Manchester Geomicro, a geo-microbiology and molecular environmental science research group affiliated with the University of Manchester, used combined chemical and microbiological contaminant degradation processes to remediate tetrachloroethene at a contaminated site in Germany.

In the study, the researchers used Carbo-Iron®, an applied composite material consisting of colloidal activated carbon and embedded nanoscale zero valent iron (ZVI). In a recent long term study of a field site in Germany, it was injected into an aquifer contaminated with tetrachloroethene (PCE). Carbo-Iron® particles accumulated the pollutants and promoted their reductive dechlorination via a combination of chemical and microbial degradation processes.

Schematic illustrating Carbo-Iron® particle structure and key chemical and microbial dechlorination pathways

The presence of the dominant degradation products ethene and ethane in monitoring wells over the duration of the study indicates the extended life-time of ZVI’s chemical activity in the composite particles. However, the identification of the partial dechlorination product cis-dichlorethene (cis-DCE) at depths between 12.5m and 25m below ground level one year into the study, suggested additional microbially mediated degradation processes were also involved.

Hydrogen produced by the aqueous corrosion of ZVI contributed to a decrease in the redox potential of the groundwater up to 190 days promoting organo-halide reducing conditions that lasted for months after. The long lasting reducing effect of Carbo-Iron® is crucial to efficiently supporting microbial dehalogenation, because growth and activity of these microbes occurs relatively slowly under environmental conditions. Detection of increased levels of cis-DCE in the presence of various organohalide reducing bacteria supported the hypothesis that Carbo-Iron® was able to support microbial dechlorination pathways. Despite the emergence of cis-DCE, it did not accumulate, pointing to the presence of an additional microbial degradation step.

The results of state-of-the-art compound specific isotope analysis in combination with pyrosequencing suggested the oxidative degradation of cis-DCE by microorganism related to Polaromonas sp. Strain JS666. Consequently, the formation of carcinogenic degradation intermediate vinyl chloride was avoided due to the sequential reduction and oxidation processes. Overall, the moderate and slow change of environmental conditions mediated by Carbo-Iron® not only supported organohalide-respiring bacteria, but also created the basis for a subsequent microbial oxidation step.

This study, published in Science of the Total Environment (Vogel et al. 2018, vol. 628-629, 1027-1036) illustrates how microbes and nanomaterials can work in combination for targeted remediation. The work was led by collaborators (Katrin Mackenzie and Maria Vogel) at the Helmholtz Centre for Environmental Research in Leipzig, Germany, and adds to a growing portfolio of research highlighting the potential of Carbo-Iron® as an in situ treatment for contaminated groundwater.

 

Remediation of Trichoroethane (TCE) – contaminated groundwater by persulfate oxidation

Researchers in Taiwan performed field trials on the ability of persulfate to remediate trichloroethane (TCE) contaminated groundwater.  The purpose of the field trial was to (1) evaluate the efficacy of TCE treatment using persulfate with different injection strategies; (2) determine the persistence of persulfate in the aquifer; (3) determine the persulfate radius of influence and transport distance; and (4) determine the impact of persulfate on indigenous microorganisms during remediation.

The researchers discovered that persulfate removed up to 100% TCE under specific conditions.  Overall, they found a single, higher does of persulfate was more effective at destroying TCE than two separate, smaller doses.

Results show that sequential injections of a large amount of persulfate are suggested to maintain good long-term performance for TCE treatment. This paper is available at http://pubs.rsc.org/en/content/articlehtml/2018/ra/c7ra10860e.

Arsenic found to control uranium contamination

As reported by World Nuclear News, an international team led by the University of Sheffield has discovered that the toxic element arsenic prevents uranium from an abandoned mine in the UK migrating into rivers and groundwater.  The discovery could help in the remediation of former uranium mines and other radioactively contaminated areas around the world, the scientists believe.

The team of scientists – led by the Department of Materials Science and Engineering at the University of Sheffield – studied the uranium and arsenic in the topsoil at the abandoned South Terras uranium mine in Cornwall, England.

The researchers used some of the world’s brightest synchrotron X-ray microscopes – the Swiss Light Source and the USA’s National Synchrotron Light Source – to unearth what is believed to be the first example of arsenic controlling uranium migration in the environment.  These microscopes use intense X-ray beams to focus on a spot just one-millionth of a metre in diameter.

“We use synchrotron X-rays to identify and isolate the microscopic uranium particles within the soils and determine their chemical composition and mineral species,” said co-author of the study, Neil Hyatt.  “It’s like being able to find tiny uranium needles in a soil haystack with a very sensitive metal detector.”

Source: © Claire Corkhill
The abandoned South Terras mine in Cornwall where uranium was mined until 1930

According to the study – published on 14 December in Nature Materials Degradation – ore extraction processes and natural weathering of rock at the South Terras mine has led to the proliferation of other elements during degradation, particularly arsenic and beryllium, which were found in significant concentrations.  The arsenic and uranium were found to have formed the highly insoluble secondary mineral metazeunerite.

“Significantly, our data indicate that metazeunerite and metatorbernite were found to occur in solid solution, which has not been previously observed at other uranium-contaminated sites where uranyl-micas are present,” the study says.

Claire Corkhill, lead author of the study, said: “Locking up the uranium in this mineral structure means that it cannot migrate in the environment.”

The researchers concluded that this process at South Terras – which operated between 1873 and 1930, producing a total of 736 tonnes of uranium – is the result of a set of “rather unique” geological conditions.  “To identify this remediation mechanism at other sites, where arsenic and uranium are key co-contaminants, further detailed mineralogical assessments are required,” they said.  “These should be considered as an essential input to understand the ultimate environmental fate of degraded uranium ore.”

“The study has far-reaching implications, from the remediation of abandoned uranium mines across the world, to the environmental clean-up of nuclear accidents and historic nuclear weapons test sites,” according to the scientists.  “It also shows the importance of local geology on uranium behavior, which can be applied to develop efficient clean-up strategies.”

Performance Assessment of Pump and Treat Systems

Researchers at the U.S. Department of Energy’s Pacific Northwest National Library recently released a paper on the Performance Assessment of Pump-and-Treat Systems.

The pump-and-treat (P&T) remediation technology is comprised of three main aspects:  groundwater extraction for hydraulic control and contaminant removal, above-ground treatment, and groundwater monitoring to assess performance.

Pump-and-treat (P&T) is a widely applied remedy for groundwater remediation at many types of sites for multiple types of contaminants. Decisions regarding major changes in the remediation approach are an important element of environmental remediation management for a site using P&T. Performance assessment during P&T remedy implementation may be needed because of diminishing returns, the complex nature of the site and contamination, or other factors.

While existing guidance documents for the performance assessment of pump-and-treat systems provide information on design, operation, and optimization for P&T systems, these documents do not provide specific technical guidance to support remedy decisions regarding when to transition to a new remedy or to initiate closure of the P&T remedy.

In the paper, the researchers describe a structured approach for P&T performance assessment that was developed  using analysis of three example P&T systems. These examples highlight key aspects of the performance assessment decision logic and represent assessment outcomes associated with optimizing the P&T system, transitioning from P&T to natural attenuation, and supplementing P&T with another technology to hasten transition to natural attenuation.

Decision elements for the P&T performance assessment include:

  • Contaminant concentrations and trends
  • Contaminant mass discharge from source areas or at selected plume locations
  • The attenuation capacity of the aquifer
  • Estimated future plume behavior and time to reach remedial action objectives for the site
  • P&T system design, operational, and cost information

Categories of decision outcomes for the P&T assessment include:

  • Initiate P&T remedy closure
  • Continue with existing or optimized P&T
  • Transition to Monitored Natural Attenuation
  • Supplement P&T with other treatment technologies
  • Transition to a new remedy approach