-
1.
The Complexity of Spills: The Fate of the Deepwater Horizon Oil.
Passow, U, Overton, EB
Annual review of marine science. 2021;:109-136
Abstract
The Deepwater Horizon oil spill was the largest, longest-lasting, and deepest oil accident to date in US waters. As oil and natural gas jetted from release points at 1,500-m depth in the northern Gulf of Mexico, entrainment of the surrounding ocean water into a buoyant plume, rich in soluble hydrocarbons and dispersed microdroplets of oil, created a deep (1,000-m) intrusion layer. Larger droplets of liquid oil rose to the surface, forming a slick of mostly insoluble, hydrocarbon-type compounds. A variety of physical, chemical, and biological mechanisms helped to transform, remove, and redisperse the oil and gas that was released. Biodegradation removed up to 60% of the oil in the intrusion layer but was less efficient in the surface slick, due to nutrient limitation. Photochemical processes altered up to 50% (by mass) of the floating oil. The surface oil expression changed daily due to wind and currents, whereas the intrusion layer flowed southwestward. A portion of the weathered surface oil stranded along shorelines. Oil from both surface and intrusion layers were deposited onto the seafloor via sinking marine oil snow. The biodegradation rates of stranded or sedimented oil were low, with resuspension and redistribution transiently increasing biodegradation. The subsequent research efforts increased our understanding of the fate of spilled oil immensely, with novel insights focusing on the importance of photooxidation, the microbial communities driving biodegradation, and the formation of marine oil snow that transports oil to the seafloor.
-
2.
Effective sequestration of chromium by bacterial biosorption: a review.
John, R, Rajan, AP
Preparative biochemistry & biotechnology. 2021;(8):738-748
Abstract
Bioremediation is an important function of microorganisms in relation to contaminated soils, wastewater and effluent. Microbes have always been demonstrated to be cost-efficient in the treatment of industrial effluents containing heavy metals like chromium(VI). As more and more new and novel isolates are being discovered with having the ability to acclimatize to varying environments. The application of microorganisms, especially that of bacteria, proves to be showing a greater potential as a low costing biotechnological application. The procedure can be adjusted according to the needs and conditional requirements where the bio-absorbents utilized might be either dead or living. Microbial bioabsorption of chromium(VI) stands out to be an alternative for the removal of the toxic contaminant. This review is focused on the different biosorbent features appropriate in the removal of chromium; different types of bioreactors; and the evolution of research with an overview of bioabsorption.
-
3.
Anammox-based processes: How far have we come and what work remains? A review by bibliometric analysis.
Nsenga Kumwimba, M, Lotti, T, Şenel, E, Li, X, Suanon, F
Chemosphere. 2020;:124627
Abstract
Nitrogen contamination remains a severe environmental problem and a major threat to sustainable development worldwide. A systematic analysis of the literature indicates that the partial nitritation-anammox (PN/AMX) process is still actively studied as a viable option for energy-efficient and feasible technology for the sustainable treatment of N- rich wastewaters, since its initial discovery in 1990. Notably, the mainstream PN/AMX process application remains the most challenging bottleneck in AMX technology and fascinates the world's attention in AMX studies. This paper discusses the recent trends and developments of PN/AMX research and analyzes the results of recent years of research on the PN/AMX from lab-to full-scale applications. The findings would deeply improve our understanding of the major challenges under mainstream conditions and next-stage research on the PN/AMX process. A great deal of efforts has been made in the process engineering, PN/AMX bacteria populations, predictive modeling, and the full-scale implementations during the past 22 years. A series of new and excellent experimental findings at lab, pilot and full-scale levels including good nitrogen removal performance even under low temperature (15-10 °C) around the world were achieved. To date, pilot- and full-scale PN/AMX have been successfully used to treat different types of industrial sewage, including black wastewater, sludge digester liquids, landfill leachate, monosodium glutamate wastewater, etc. Supplementing the qualitative analysis, this review also provides a quantitative bibliometrics study and evaluates global perspectives on PN/AMX research published during the past 22 years. Finally, general trends in the development of PN/AMX research are summarized with the aim of conveying potential future trajectories. The current review offers a valuable orientation and global overview for scientists, engineers, readers and decision makers presently focusing on PN/AMX processes.
-
4.
The effects of heavy metals on human metabolism.
Fu, Z, Xi, S
Toxicology mechanisms and methods. 2020;(3):167-176
Abstract
As technology continues to advance, heavy metals in drinking water have exceeded recommended limits from regulators around the world. The main source of human exposure to heavy metals is from contaminated drinking water. The effects of drinking water contaminated with heavy metals, such as arsenic, lead, nickel, cadmium and mercury, have gradually caught the attention of the relevant departments and personnel. It is well known that occupational exposure to heavy metals occurs as a result of using these metals in a variety of industrial processes in and/or a variety of materials, including color pigments and alloys. A series of adverse effects on human metabolism has resulted from exposure to heavy metal-contaminated drinking water, which has been recorded from around the world. The general mechanism of heavy metal toxicity is through the production of reactive oxygen species, the appearance of oxidative damage, and subsequent adverse effects on health. Therefore, water contaminated with heavy metals causes high morbidity and mortality worldwide. In order to address concern regarding the health effects of different heavy metals, this paper reviews its sources, distribution and effects of heavy metal on human metabolism.HIGHLIGHTSThe accumulation of heavy metals such as lead, arsenic, mercury, cadmium and nickel will destroy the main metabolic process of human body.Redox reactions in biological systems are caused by carcinogenic metal ions such as nickel and arsenic. The free radicals produced by these reactions cause oxidative damage to proteins and DNA.The accumulation of heavy metals eventually produces reactive oxygen species that can cause oxidative stress, which may lead to the production of various diseases.
-
5.
Potential of enzymatic process as an innovative technology to remove anticancer drugs in wastewater.
Pereira, CS, Kelbert, M, Daronch, NA, Michels, C, de Oliveira, D, Soares, HM
Applied microbiology and biotechnology. 2020;(1):23-31
Abstract
Anticancer drugs are a class of pharmaceutical compounds that have been found in hospital, domestic, and industrial wastewaters and also in surface waters. They have been showing recalcitrance to conventional wastewater treatment technologies and present a potential risk to environment and human health, since they exhibit cytotoxic, teratogenic, and carcinogenic among other effects in higher organisms, even at low concentrations. The presence of these compounds in the environment is a recent challenge for wastewater treatment and some alternative strategies to remove them were already studied, such as white-rot fungi (WRF) technologies. Despite promising results, processes involving fungi are complex, have high reaction times, and require nutrient addition for fungus growth and maintenance. Due to this potential, strategies to make the technology feasible were studied, such as the possibility for direct application of enzymes secreted by WRF. Enzymatic processes were studied in the removal of other pharmaceuticals such as antibiotics, anti-inflammatory, and steroid hormones; however, to the best of our knowledge, there is a gap on literature about their direct action on anticancer drugs.
-
6.
Adsorption of heavy metal ions by sodium alginate based adsorbent-a review and new perspectives.
Gao, X, Guo, C, Hao, J, Zhao, Z, Long, H, Li, M
International journal of biological macromolecules. 2020;:4423-4434
Abstract
With the development of modern industry, heavy metal pollution is one of the most important environmental issues. Due to its simplicity and low-cost, adsorption is considered as a green and environmental friendly method to remove heavy metals from industrial effluents. Sodium alginate is a natural polysaccharide, which consists of abundant hydroxyl and carboxyl groups, has been widely reported as the raw material for the adsorption of heavy metals from aqueous solutions. By surface grafting and cross-linking, adsorbents synthesized from sodium alginate have exhibited large uptake capacities as well as high removal rates for heavy metal ions. However, the poor physical strength and plain thermostability have significantly limited the utilization of sodium alginate based materials in industrial applications. Moreover, reductions of specific metal ions were observed in some studies, of which the reduction mechanism is not clearly clarified. In this work, the development of sodium alginate based adsorbents was summarized, including the physicochemical properties of the polymer, the modification of sodium alginate, sodium alginate based composite materials, and the adsorption behaviors as well as the mechanism. Chelation, electrostatic interaction, ion exchange, reduction and photocatalytic reduction were involved in the adsorption process, which can be determined by chemical characterization with further elucidation by density functional theory calculation. Finally, the limitations of sodium alginate based adsorbents were revealed with suggestions for future research.
-
7.
Enzymatic assays for the assessment of toxic effects of halogenated organic contaminants in water and food. A review.
Artabe, AE, Cunha-Silva, H, Barranco, A
Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association. 2020;:111677
Abstract
Halogenated organic compounds are a particular group of contaminants consisting of a large number of substances, and of great concern due to their persistence in the environment, potential for bioaccumulation and toxicity. Some of these compounds have been classified as persistent organic pollutants (POPs) under The Stockholm Convention and many toxicity assessments have been conducted on them previously. In this work we provide an overview of enzymatic assays used in these studies to establish toxic effects and dose-response relationships. Studies in vivo and in vitro have been considered with a particular emphasis on the impact of halogenated compounds on the activity of relevant enzymes to the humans and the environment. Most information available in the literature focuses on chlorinated compounds, but brominated and fluorinated molecules are also the target of increasing numbers of studies. The enzymes identified can be classified as enzymes: i) the activities of which are affected by the presence of halogenated organic compounds, and ii) those involved in their metabolisation/detoxification resulting in increased activities. In both cases the halogen substituent seems to have an important role in the effects observed. Finally, the use of these enzymes in biosensing tools for monitoring of halogenated compounds is described.
-
8.
Scenario, perspectives and mechanism of arsenic and fluoride Co-occurrence in the groundwater: A review.
Kumar, M, Goswami, R, Patel, AK, Srivastava, M, Das, N
Chemosphere. 2020;:126126
Abstract
Arsenic (As) and fluoride (F-) are the two most conspicuous contaminants, in terms of distribution and menace, in aquifers around the world. While the majority of studies focus on the individual accounts of their hydro-geochemistry, the current work is an effort to bring together the past and contemporary works on As and F- co-occurrence. Co-occurrence in the context of As and F- is a broad umbrella term and necessarily does not imply a positive correlation between the two contaminants. In arid oxidized aquifers, healthy relationships between As and F- is reported owing desorption based release from the positively charged (hydr)oxides of metals like iron (Fe) under alkaline pH. In many instances, multiple pathways of release led to little or no correlation between the two, yet there were high concentrations of both at the same time. The key influencer of the strength of the co-occurrence is seasonality, environment, and climatic conditions. Besides, the existing primary ion and dissolved organic matter also affect the release and enrichment of As-F- in the aquifer system. Anthropogenic forcing in the form of mining, irrigation return flow, extraction, recharge, and agrochemicals remains the most significant contributing factor in the co-occurrence. The epidemiological indicate that the interface of these two interacting elements concerning public health is considerably complicated and can be affected by some uncertain factors. The existing explanations of interactions between As-F are indecisive, especially their antagonistic interactions that need further investigation. "Multi-contamination perspectives of groundwater" is an essential consideration for the overarching question of freshwater sustainability.
-
9.
Removal of toxic metals from wastewater in constructed wetlands as a green technology; catalyst role of substrates and chelators.
Batool, A, Saleh, TA
Ecotoxicology and environmental safety. 2020;:109924
Abstract
In recent years knowledge in regard to phytoremediation for removal of metals from wastewater has been extensively developed. Despite advance treatment methods; different plants were widely used for wastewater treatment that may affect the efficiency of plants by stressing their natural ability. Therefore, this paper reviews the catalytic role of constructed wetlands, spiking of chelators and substrates to enhance phytoremediation for removal of metals. Catalytic combination of substrates, chelators with plants helped to remove different metals from wastewater simultaneously without compromising the plant's health. Moreover, this paper summarizes the interaction mechanism of plants with the chelators and substrates within constructed wetlands. In addition, this paper also discusses the potential research needs for this field.
-
10.
A Review of the Effect of Trace Metals on Freshwater Cyanobacterial Growth and Toxin Production.
Facey, JA, Apte, SC, Mitrovic, SM
Toxins. 2019;(11)
Abstract
Cyanobacterial blooms are becoming more common in freshwater systems, causing ecological degradation and human health risks through exposure to cyanotoxins. The role of phosphorus and nitrogen in cyanobacterial bloom formation is well documented and these are regularly the focus of management plans. There is also strong evidence that trace metals are required for a wide range of cellular processes, however their importance as a limiting factor of cyanobacterial growth in ecological systems is unclear. Furthermore, some studies have suggested a direct link between cyanotoxin production and some trace metals. This review synthesises current knowledge on the following: (1) the biochemical role of trace metals (particularly iron, cobalt, copper, manganese, molybdenum and zinc), (2) the growth limitation of cyanobacteria by trace metals, (3) the trace metal regulation of the phytoplankton community structure and (4) the role of trace metals in cyanotoxin production. Iron dominated the literature and regularly influenced bloom formation, with 15 of 18 studies indicating limitation or colimitation of cyanobacterial growth. A range of other trace metals were found to have a demonstrated capacity to limit cyanobacterial growth, and these metals require further study. The effect of trace metals on cyanotoxin production is equivocal and highly variable. Better understanding the role of trace metals in cyanobacterial growth and bloom formation is an essential component of freshwater management and a direction for future research.