Genetic adaptation to heavy metals in aquatic organisms: a review

Natural populations in polluted areas are possibly subjected to selective pressures for an increased resistance to toxicants. This can result in the evolution of resistance, which may have important implications for decisions regarding safe ambient toxicant levels. By reviewing the evolution of resistance to heavy metals in aquatic organisms, we aimed to determine if all populations negatively affected by toxicants do adapt to them. If the published literature accurately represents the situation in polluted areas (i.e. negative results having an equal chance of being published), it can be concluded that most, but not all, populations in polluted areas do have an increased resistance. But it can usually not be determined if such an increased resistance has a genetic basis. There is less evidence for the evolution of resistance in metazoans (especially fish) than in micro-organisms. Additional information strongly indicates that many populations fail to survive in polluted environments. It thus seems dangerous to relax water quality criteria on the assumption that all populations in polluted environments will evolve an increased resistance. But the fact that the evolution of resistance to environmental pollutants does seem to occur in some populations in polluted environments warrants taking that possibility into consideration when evaluating the results of bioassays and monitoring programs.     

Prospects in the bioremediation of petroleum hydrocarbon contaminants from hypersaline environments: A review

Hypersaline environments are underappreciated and are frequently exposed to pollution from petroleum hydrocarbons. Unlike other environs, the high salinity conditions present are a deterrent to various remediation techniques. There is also production of hypersaline waters from oil-polluted ecosystems which contain toxic hydrophobic pollutants that are threat to public health, environmental protection, and sustainability. Currently, innovative advances are being proposed for the remediation of oil-contaminated hypersaline regions. Such advancements include the exploration and stimulation of native microbial communities capable of utilizing and degrading petroleum hydrocarbons. However, prevailing salinity in these environments is unfavourable for the growth of non-halophylic microorganisms, thus limiting effective bioremediation options. An in-depth understanding of the potentials of various remediation technologies of hydrocarbon-polluted hypersaline environments is lacking. Thus, we present an overview of petroleum hydrocarbon pollution in hypersaline ecosystems and discuss the challenges and prospects associated with several technologies that may be employed in remediation of hydrocarbon pollution in the presence of delimiting high salinities. The application of biological remediation technologies including the utilization of halophilic and halotolerant microorganisms is also discussed.

     

Insights into conventional and recent technologies for arsenic bioremediation: A systematic review

Environmental Science and Pollution Research - Arsenic (As) bioremediation has been an economical and sustainable approach, being practiced widely under several As-contaminated environments....     

A review of the fate and toxicity of 3,4-dichloroaniline in aquatic environments

The physicochemical properties, fate and toxicity of 3,4-dichloroaniline (3,4-DCA) in aquatic environments are reviewed.     

Presence of heavy metals in drinking water resources of Iran: a systematic review and meta-analysis

Environmental Science and Pollution Research - Water quality is one of the most important indices for public health especially for drinking water consumptions. This study was conducted to survey...     

Small-scale spatial and temporal variance in the concentration of heavy metals in aquatic sediments: a review and some new concepts.

Uncertainty associated with data derived by the analyses of heavy metals in aquatic sediment is due to variance produced in the laboratory (precision), plus 'natural', small-scale spatial variance, (or field variance) at the sampling site. Precision is easily determined and is usually reported in contaminant studies, but field variance is poorly understood and seldom documented. It is important to have an understanding of the field variance because if small-scale spatial variance in the concentration of heavy metals is excessive, regional trends may be limited value. Similarly, if temporal change is large, the results of single synoptic surveys may be questionable and the ability to demonstrate anthropogenic contributions over time will be difficult. However, it is evident from the literature that the information needed to address problems of spatial and temporal variance in the field is beyond the resources of most researchers. Analytical precision of about 5% relative standard deviation (RSD) for heavy metal analysis is typical of a well-managed laboratory. Many studies of small-scale spatial variability made during the current investigation indicate that field variance is related to ambient energy and to the type of sedimentological environment. Total variance (analytical plus field variance) is approximately 10% RSD (mean for a suite of nine trace elements) for depositional parts of estuaries and the marine environment, but increases to about 20-35% RSD for the more dynamic parts of the estuarine environment and the fluvial system. Repeated sampling over periods of up to 7 years undertaken during the present study, indicate a similar order of magnitude for temporal variability in these sedimentological environments. A proposed scheme to provide information on field variance is to undertake small-scale spatial and temporal studies in discrete sedimentological environments in the study area after sediment sampling and characterisation has been completed. The comparatively large proportion of total variance associated with small-scale spatial and temporal variability in the field questions the often excessive cost and effort made in attempting minor reductions in analytical precision in contaminant investigations.     

Effect of metals on a siderophore producing bacterial isolate and its implications on microbial assisted bioremediation of metal contaminated soils

A bacterial isolate producing siderophore under iron limiting conditions, was isolated from mangroves of Goa. Based on morphological, biochemical, chemotaxonomical and 16S rDNA studies, the isolate was identified as Bacillus amyloliquefaciens NAR38.1. Preliminary characterization of the siderophore indicated it to be catecholate type with dihydroxy benzoate as the core component. Optimum siderophore production was observed at pH 7 in mineral salts medium (MSM) without any added iron with glucose as the carbon source. Addition of NaCl in the growth medium showed considerable decrease in siderophore production above 2% NaCl. Fe⁺² and Fe⁺³ below 2 μM and 40 μM concentrations respectively, induced siderophore production, above which the production was repressed. Binding studies of the siderophore with Fe⁺² and Fe⁺³ indicated its high affinity towards Fe⁺³. The siderophore concentration in the extracellular medium was enhanced when MSM was amended with essential metals Zn, Co, Mo and Mn, however, decreased with Cu, while the concentration was reduced with abiotic metals As, Pb, Al and Cd. Significant increase in extracellular siderophore production was observed with Pb and Al at concentrations of 50 μM and above. The effect of metals on siderophore production was completely mitigated in presence of Fe. The results implicate effect of metals on the efficiency of siderophore production by bacteria for potential application in bioremediation of metal contaminated iron deficient soils especially in the microbial assisted phytoremediation processes.     

Fate of hydrophobic organic pollutants in the aquatic environment: a review

The fate of hydrophobic organic pollutants in the aquatic environment is controlled by a variety of physical, chemical and biological processes. Some of the most important are physical transport, chemical and biological transformations, and distribution of these compounds between the various environmental compartments (atmosphere, water, sediments and biota). The major biogeochemical processes that control the fate of hydrophobic organic compounds in the aquatic environment are reviewed. These processes include evaporation, solubilization, interaction with dissolved organic matter, sediment-water partitioning, bioaccumulation and degradation. Physico-chemical parameters used to predict the aquatic fate of such compounds are also discussed.     

Fluoride toxicity to aquatic organisms: a review

Published data on the toxicity of fluoride (F-) to algae, aquatic plants, invertebrates and fishes are reviewed. Aquatic organisms living in soft waters may be more adversely affected by fluoride pollution than those living in hard or seawaters because the bioavailability of fluoride ions is reduced with increasing water hardness. Fluoride can either inhibit or enhance the population growth of algae, depending upon fluoride concentration, exposure time and algal species. Aquatic plants seem to be effective in removing fluoride from contaminated water under laboratory and field conditions. In aquatic animals, fluoride tends to be accumulated in the exoskeleton of invertebrates and in the bone tissue of fishes. The toxic action of fluoride resides in the fact that fluoride ions act as enzymatic poisons, inhibiting enzyme activity and, ultimately, interrupting metabolic processes such as glycolysis and synthesis of proteins. Fluoride toxicity to aquatic invertebrates and fishes increases with increasing fluoride concentration, exposure time and water temperature, and decreases with increasing intraspecific body size and water content of calcium and chloride. Freshwater invertebrates and fishes, especially net-spinning caddisfly larvae and upstream-migrating adult salmons, appear to be more sensitive to fluoride toxicity than estuarine and marine animals. Because, in soft waters with low ionic content, a fluoride concentration as low as 0.5 mg F-/l can adversely affect invertebrates and fishes, safe levels below this fluoride/l concentration are recommended in order to protect freshwater animals from fluoride pollution.     

Biofilm comprising phototrophic, diazotrophic, and hydrocarbon-utilizing bacteria: a promising consortium in the bioremediation of aquatic hydrocarbon pollutants

Biofilms harboring simultaneously anoxygenic and oxygenic phototrophic bacteria, diazotrophic bacteria, and hydrocarbon-utilizing bacteria were established on glass slides suspended in pristine and oily seawater. Via denaturing gradient gel electrophoresis analysis on PCR-amplified rRNA gene sequence fragments from the extracted DNA from biofilms, followed by band amplification, biofilm composition was determined. The biofilms contained anoxygenic phototrophs belonging to alphaproteobacteria; pico- and filamentous cyanobacteria (oxygenic phototrophs); two species of the diazotroph Azospirillum; and two hydrocarbon-utilizing gammaproteobacterial genera, Cycloclasticus and Oleibacter. The coexistence of all these microbial taxa with different physiologies in the biofilm makes the whole community nutritionally self-sufficient and adequately aerated, a condition quite suitable for the microbial biodegradation of aquatic pollutant hydrocarbons.     

Environmental noise in hospitals: a systematic review

Environmental noise has been growing in recent years, causing numerous health problems. Highly sensitive environments such as hospitals deserve special attention, since noise can aggravate patients’ health issues and impair the performance of healthcare professionals. This work consists of a systematic review of scientific articles describing environmental noise measurements taken in hospitals between the years 2015 and 2020. The researchers started with a consultation of three databases, namely, Scopus, Web of Science, and ScienceDirect. The results indicate that for the most part, these studies are published in journals in the fields of medicine, engineering, environmental sciences, acoustics, and nursing and that most of their authors work in the fields of architecture, engineering, medicine, and nursing. These studies, which are concentrated in Europe, the Americas, and Asia, use as reference values sound levels recommended by the World Health Organization. L_eq measured in hospital environments showed daytime values ranging from 37 to 88.6 dB (A) and nighttime values of 38.7 to 68.8 dB (A). L_eq values for outdoor noise were 74.3 and 56.6 dB (A) for daytime and nighttime, respectively. The measurements were taken mainly inside hospitals, prioritizing more sensitive departments such as intensive care units. There is a potential for growth in work carried out in this area, but research should also include discussions about guidelines for improvement measures aimed at reducing noise in hospitals.

Graphical abstract

     

Perspectives of using fungi as bioresource for bioremediation of pesticides in the environment: a critical review

Pesticides are used for controlling the development of various pests in agricultural crops worldwide. Despite their agricultural benefits, pesticides are often considered a serious threat to the environment because of their persistent nature and the anomalies they create. Hence removal of such pesticides from the environment is a topic of interest for the researchers nowadays. During the recent years, use of biological resources to degrade or remove pesticides has emerged as a powerful tool for their in situ degradation and remediation. Fungi are among such bioresources that have been widely characterized and applied for biodegradation and bioremediation of pesticides. This review article presents the perspectives of using fungi for biodegradation and bioremediation of pesticides in liquid and soil media. This review clearly indicates that fungal isolates are an effective bioresource to degrade different pesticides including lindane, methamidophos, endosulfan, chlorpyrifos, atrazine, cypermethrin, dieldrin, methyl parathion, heptachlor, etc. However, rate of fungal degradation of pesticides depends on soil moisture content, nutrient availability, pH, temperature, oxygen level, etc. Fungal strains were found to harbor different processes including hydroxylation, demethylation, dechlorination, dioxygenation, esterification, dehydrochlorination, oxidation, etc during the biodegradation of different pesticides having varying functional groups. Moreover, the biodegradation of different pesticides was found to be mediated by involvement of different enzymes including laccase, hydrolase, peroxidase, esterase, dehydrogenase, manganese peroxidase, lignin peroxidase, etc. The recent advances in understanding the fungal biodegradation of pesticides focusing on the processes, pathways, genes/enzymes and factors affecting the biodegradation have also been presented in this review article.     

Influence of land use and land cover on the spatial variability of dissolved organic matter in multiple aquatic environments

Environmental Science and Pollution Research - Water quality of lakes, estuaries, and coastal areas serves as an indicator of the overall health of aquatic ecosystems as well as the health of the...     

Implementation of a continuous-flow stirred bioreactor system in the bioremediation of heavy metals from industrial waste water

The industrial applicability of immobilized non-viable yeast biomass (Saccharomyces cerivisiae) in continuous-flow stirred bioreactors was tested with respect to metal removal from electroplating effluent solutions containing Cu, Cd, Cr, Ni and Zn in excess of the stipulated water quality criteria. Two systems, a dual bioreactor and triple bioreactor system in series, were tested and compared regarding their efficiency of metal removal. The system containing two bioreactors linked in series provided a more efficient solution to the problem. The introduction of a third bioreactor into the system had a marginal effect on the amount of metal removed. Subsequent to treatment within the bioreactors the levels of Cu, Cr and Ni in the effluent complied with the stipulated drinking water quality criteria and, although in excess of these criteria only 18% of the initial Zn and 17% of the Cd remained in solution.     

Evolution of bacterial community during bioremediation of PAHs in a coal tar contaminated soil

The monitoring of a windrow treatment applied to soil contaminated by mostly 2-, 3- and 4-ring PAHs produced by coal tar distillation was performed by following the evolution of both PAH concentration and the bacterial community. Total and PAH-degrading bacterial community structures were followed by 16S rRNA PCR-DGGE in parallel with quantification by bacterial counts and 16 PAH measurements. Six months of biological treatment led to a strong decrease in 2-, 3- and 4-ring PAH concentrations (98, 97 and 82% respectively). This result was associated with the activity of bacterial PAH-degraders belonging mainly to the Gamma-proteobacteria, in particular, the Enterobacteria and Pseudomonas genera, which were detected over the course of the treatment. This group was considered to be a good bioindicator to determine the potential PAH biodegradation of contaminated soil. Conversely, other species, like the Beta-proteobacteria, were detected after 3months, when 2-, 3- and 4-ring PAHs were almost completely degraded. Thus, presence of the Beta-proteobacteria group could be considered a good candidate indicator to estimate the endpoint of biotreatment of this type of PAH-contaminated soil.     

Toxicological aspects of trihalomethanes: a systematic review

Environmental Science and Pollution Research - Chlorine is considered the most used chemical agent for water disinfection worldwide. However, water chlorination can lead to by-product generation...     

Isolation of mesotrione-degrading bacteria from aquatic environments in Brazil

Mesotrione is a benzoylcyclohexane-1,3-dione herbicide that inhibits 4-hydroxyphenyl pyruvate dioxygenase in target plants. Although it has been used since 2000, only a limited number of degrading microorganisms have been reported. Mesotrione-degrading bacteria were selected among strains isolated from Brazilian aquatic environments, located near corn fields treated with this herbicide. Pantoea ananatis was found to rapidly and completely degrade mesotrione. Mesotrione did not serve as a sole C, N, or S source for growth of P. ananatis, and mesotrione catabolism required glucose supplementation to minimal media. LC-MS/MS analyses indicated that mesotrione degradation produced intermediates other than 2-amino-4-methylsulfonyl benzoic acid or 4-methylsulfonyl-2-nitrobenzoic acid, two metabolites previously identified in a mesotrione-degrading Bacillus strain. Since P. ananatis rapidly degraded mesotrione, this strain might be useful for bioremediation purposes.     

The use of chelating agents in the remediation of metal-contaminated soils: a review

This paper reviews current remediation technologies that use chelating agents for the mobilization and removal of potentially toxic metals from contaminated soils. These processes can be done in situ as enhanced phytoextraction, chelant enhanced electrokinetic extraction and soil flushing, or ex situ as the extraction of soil slurry and soil heap/column leaching. Current proposals on how to treat and recycle waste washing solutions after soil is washed are discussed. The major controlling factors in phytoextraction and possible strategies for reducing the leaching of metals associated with the application of chelants are also reviewed. Finally, the possible impact of abiotic and biotic soil factors on the toxicity of metals left after the washing of soil and enhanced phytoextraction are briefly addressed.     

Aquatic environments polluted with antibiotics and heavy metals: a human health hazard

Aquatic environments often receive wastewater containing pollutants such as antibiotics and heavy metals from hospital sewage, as well as contaminants from soil. The presence of these pollutants can increase the rate of exchange of resistant genes between environmental and pathogenic bacteria, which can make the treatment of various types of bacterial infections in humans and animals difficult, in addition to causing environmental problems such as ecological risk. In this study, two tetracycline-resistant Pseudomonas aeruginosa (EW32 and EW33), isolated from aquatic environments close to industries and a hospital in southeastern Brazil, were investigated regarding the possible association between tetracycline and heavy metal resistance. The isolate EW32 presented a conjugative plasmid with coresistance to tetracycline and copper, reinforcing the concern that antibiotic resistance by acquisition of plasmids can be induced by the selective pressure of heavy metals in the environment.