Toxic Water Contaminants Research Articles

Duckweed biomarkers for identifying toxic water contaminants?

Surface or ground waters can be contaminated with numerous toxic substances. The duckweeds Lemna minor and Lemna gibba are widely used for assaying waterborne toxicity to higher plants in terms of growth inhibition and photosynthetic pigment reduction. These tests cannot, however, in themselves determine the nature of the agents responsible for toxicity. Morphological, developmental, physiological, biochemical, and genetic responses of duckweeds to exposure to toxic water contaminants constitute biomarkers of toxic effect. In principle, the very detection of these biomarkers should enable the contaminants having elicited them (and being responsible for the toxicity) to be identified. However, in practice, this is severely compromised by insufficient specificity of biomarkers for their corresponding toxicants and by the lack of documentation of biomarker/toxin relationships. The present contribution illustrates the difficulties of using known water contaminant-related duckweed biomarkers to identify toxins, and discusses possibilities for achieving this goal.

Cerium dioxide and composites for the removal of toxic metal ions

The presence of contaminants in potable water is a cause of worldwide concern. In particular, the presence of metals such as arsenic, lead, cadmium, mercury, chromium can affect human health. There is thus a need for advanced techniques of water decontamination. Adsorbents based on cerium dioxide (CeO2), also named ‘ceria,’ have been used to remove contaminants such as arsenic, fluoride, lead and cadmium. Ceria and composites display high surface area, controlled porosity and morphology, and abundance of functional groups. They have already found usage in many applications including optical, semiconductor and catalysis. Exploiting their attractive features for water treatment would unravel their potential. We review the potential of ceria and its composites for the removal of toxic metal ions from aqueous medium. The article discusses toxic contaminants in water and their impact on human health; the synthesis and adsorptive behavior of ceria-based materials including the role of morphology and surface area on the adsorption capacity, best fit adsorption isotherms, kinetic models, possible mechanisms, regeneration of adsorbents; and future perspectives of using metal oxides such as ceria. The focus of the report is the generation of cost-effective oxides of rare-earth metal, cerium, in their standalone and composite forms for contaminant removal.

Ingested Nitrate, Disinfection By-products, and Kidney Cancer Risk in Older Women.

N-nitroso compounds formed endogenously after nitrate/nitrite ingestion are animal renal carcinogens. Previous epidemiologic studies of drinking water nitrate did not evaluate other potentially toxic water contaminants, including the suspected renal carcinogen chloroform. In a cohort of postmenopausal women in Iowa (1986-2010), we used historical measurements to estimate long-term average concentrations of nitrate-nitrogen (NO3-N) and disinfection by-products (DBP) in public water supplies. For NO3-N and the regulated DBP (total trihalomethanes [THM] and the sum of five haloacetic acids [HAA5]), we estimated the number of years of exposure above one-half the current maximum contaminant level (>½-MCL NO3-N; >5 mg/L). Dietary intakes were assessed via food frequency questionnaire. We estimated hazard ratios (HRs) and 95% confidence intervals (CIs) with Cox models, and evaluated interactions with factors influencing N-nitroso compound formation. We identified 125 incident kidney cancers among 15,577 women reporting using water from public supplies >10 years. In multivariable models, risk was higher in the 95th percentile of average NO3-N (HRp95vsQ1 = 2.3; CI: 1.2, 4.3; Ptrend = 0.33) and for any years of exposure >½-MCL; adjustment for total THM did not materially change these associations. There were no independent relationships with total THM, individual THMs chloroform and bromodichloromethane, or with haloacetic acids. Dietary analyses yielded associations with high nitrite intake from processed meats but not nitrate or nitrite overall. We found no interactions. Relatively high nitrate levels in public water supplies were associated with increased risk of renal cancer. Our results also suggest that nitrite from processed meat is a renal cancer risk factor.

Surface Engineered Zeolite: An Active Interface for Rapid Adsorption and Degradation of Toxic Contaminants in Water.

Zeolite has been surface modified to form novel multifunctional materials having capability for simultaneous and facile removal of heavy metals [Pb(II)], organic pollutants [methylene blue dye], and microorganisms [E. Coli, S. Aureus, and Pseudomonas] from contaminated water. The unique concept involves formation of core-shell particles with a functional core of zeolite and a porous shell of ZnO nanoflakes which not only imparts photocatalytic and antibacterial properties but also renders the surface negatively charged, thereby facilitating rapid adsorption of Pb(II) and MB. The uniform formation of ZnO nanoflakes (shell) on the zeolite (core) surface has been confirmed by XRD, DRS, FE-SEM, and TEM studies. Metal ion adsorption studies under varying conditions of time and concentration indicate that the material follows the Langmuir isotherm model and pseudo-second-order kinetics with good correlation to the experimental data. The rapid and high adsorption capacity of the material for both Pb (II) and MB has been established while factors responsible for enhanced adsorption have been discussed. The antibacterial studies against Gram negative bacteria (E. Coli and Pseudomonas) and Gram positive bacteria (S. Aureus) showed good zone inhibition characteristics. The material can be regenerated and reused besides having ease of separation using simple techniques. Being multifunctional, efficient, nontoxic, energy neutral, and recyclable with no effluent generation, the material is an efficient and sustainable alternative for water purification.

Hybridization of TiO2 photocatalysis with coagulation and flocculation for 1,4-dioxane removal in drinking water treatment

Photocatalysis is a promising method for degrading toxic water contaminants and has the potential to be utilized for safe drinking water treatment. This study focused on the degradation of 1,4-dioxane via hybridization of TiO2 photocatalysis with coagulation and flocculation processes for emergency water treatment. The system performance was investigated considering three key factors, such as light radiation doses, flocculation conditions, and feedwater qualities. A photocatalytically enhanced water treatment system enabled the removal of 1,4-dioxane under artificial and solar UV irradiation (i.e., ∼100% removal was achieved at a UV dose of <1.0kJ per liter of water). 1,4-Dioxane degradation efficiencies showed a strong linear relationship with the total amount of UV radiation supplied. Clay particles (up to ∼115NTU) did not have a significant impact on photocatalysis, but algae (e.g., Chlororella vulgaris) did. Stronger agitation during flocculation improved 1,4-dioxane degradation, but at the expense of decreased turbidity removal. Although the coagulant added interfered with photocatalysis, proper flocculation achieved suitable 1,4-dioxane removal. Sunlight irradiation appeared to be as effective as artificial UV light regarding 1,4-dioxane removal, which could make this method viable with appropriate light exposure. A steady state model helped predict 1,4-dioxane removal efficiencies as a function of retention times at different light doses, G values, and algal levels.

DNA damage and transcriptional changes in the gills of mytilus galloprovincialis exposed to nanomolar doses of combined metal salts (Cd, Cu, Hg).

Aiming at an integrated and mechanistic view of the early biological effects of selected metals in the marine sentinel organism Mytilus galloprovincialis, we exposed mussels for 48 hours to 50, 100 and 200 nM solutions of equimolar Cd, Cu and Hg salts and measured cytological and molecular biomarkers in parallel. Focusing on the mussel gills, first target of toxic water contaminants and actively proliferating tissue, we detected significant dose-related increases of cells with micronuclei and other nuclear abnormalities in the treated mussels, with differences in the bioconcentration of the three metals determined in the mussel flesh by atomic absorption spectrometry. Gene expression profiles, determined in the same individual gills in parallel, revealed some transcriptional changes at the 50 nM dose, and substantial increases of differentially expressed genes at the 100 and 200 nM doses, with roughly similar amounts of up- and down-regulated genes. The functional annotation of gill transcripts with consistent expression trends and significantly altered at least in one dose point disclosed the complexity of the induced cell response. The most evident transcriptional changes concerned protein synthesis and turnover, ion homeostasis, cell cycle regulation and apoptosis, and intracellular trafficking (transcript sequences denoting heat shock proteins, metal binding thioneins, sequestosome 1 and proteasome subunits, and GADD45 exemplify up-regulated genes while transcript sequences denoting actin, tubulins and the apoptosis inhibitor 1 exemplify down-regulated genes). Overall, nanomolar doses of co-occurring free metal ions have induced significant structural and functional changes in the mussel gills: the intensity of response to the stimulus measured in laboratory supports the additional validation of molecular markers of metal exposure to be used in Mussel Watch programs.

Occurrence and Toxicity of Disinfection Byproducts in European Drinking Waters in Relation with the HIWATE Epidemiology Study

The HIWATE (Health Impacts of long-term exposure to disinfection byproducts in drinking WATEr) project was a systematic analysis that combined the epidemiology on adverse pregnancy outcomes and other health effects with long-term exposure to low levels of drinking water disinfection byproducts (DBPs) in the European Union. The present study focused on the relationship of the occurrence and concentration of DBPs with in vitro mammalian cell toxicity. Eleven drinking water samples were collected from five European countries. Each sampling location corresponded with an epidemiological study for the HIWATE program. Over 90 DBPs were identified; the range in the number of DBPs and their levels reflected the diverse collection sites, different disinfection processes, and the different characteristics of the source waters. For each sampling site, chronic mammalian cell cytotoxicity correlated highly with the numbers of DBPs identified and the levels of DBP chemical classes. Although there was a clear difference in the genotoxic responses among the drinking waters, these data did not correlate as well with the chemical analyses. Thus, the agents responsible for the genomic DNA damage observed in the HIWATE samples may be due to unresolved associations of combinations of identified DBPs, unknown emerging DBPs that were not identified, or other toxic water contaminants. This study represents the first to integrate quantitative in vitro toxicological data with analytical chemistry and human epidemiologic outcomes for drinking water DBPs.

Preservation Artifacts and Loss Pattern of Arsenic: A Case Study from Highly Contaminated Location in Central-East India

Arsenic is the focus of public attention because of its wider prevalence and toxicity. Proper sampling is important in characterizing toxic water contaminants in the groundwater. The present paper studies aspects of sampling, preservation artifacts, analytical issues etc. in a natural arsenic contaminated groundwater. The samples were collected from arsenic contaminated groundwater at three locations of village Kaudikasa in Rajnandgaon (Chhattisgarh). The standard method of sampling and preservation of arsenic was examined. The permitted sample holding time in this state is 180 days which has been found to be unrealistic on examination. The communication also compares the loss pattern of arsenic in unpreserved samples with samples preserved and kept at 4?C. It was found that about As losses during hold- ing after preservation were about 0% in one day, 35% in seven day, 70% in fifteen day, and 65% in thirty days time. Hence, the present recommended method of preservation leads to huge under reporting of As in natural samples. If the pattern of losses observed at the present location exists at other locations then the actual As levels could be much higher than the reported ones.

Cyclodextrin-ionic liquid polyurethanes for application in drinking water treatment

The prevalence of toxic contaminants in water remains a huge challenge for water-supplying companies and municipalities. Both organic and inorganic (especially heavy metals) pollutants are often present in water distribution networks. The presence of these contaminants in drinking water poses a major risk to human health. Organic and inorganic pollutants often co-occur in drinking water networks. However, at present there is no water treatment intervention that simultaneously removes both organic and inorganic pollutants from water to desirable levels. In our laboratories, recent studies have shown that both functionalised and un-functionalised cyclodextrin (CD) polymers are capable of removing organic pollutants from water, with the functionalised CD polymers showing an enhanced absorption capability. Ionic liquids (ILs), on the other hand, have been reported to absorb heavy metals from aqueous media. In this paper, we report on the synthesis of several cyclodextrin-ionic liquid (CD-IL) polymers, a dual system capable of removing both organic and inorganic pollutants from water. This system has been tested and has proved to possess excellent capabilities for the removal of model pollutants such as p-nitrophenol (PNP), 2,4,6-trichlorophenol (TCP) and chromium (Cr6+) from aqueous media.Keywords: organic and inorganic pollutants, CD polymers, ionic liquids, CD-IL polymers

Organic/inorganic hybrid nanospheres based on hyperbranched poly(ethylene imine) encapsulated into silica for the sorption of toxic metal ions and polycyclic aromatic hydrocarbons from water

Organic–inorganic hybrid silica nanospheres were prepared through a biomimetic silicification process in water at ambient conditions by the interaction of low cost poly(ethylene imine) hyperbranched polymer with silicic acid. The characterization of these nanoparticles by FTIR spectroscopy, scanning electron microscopy (SEM), zeta-potential and dynamic light scattering (DLS) experiments confirmed that the dendritic polymer was incorporated into the silica network. Preliminary experiments show that these hybrid nanoparticles can be employed for the removal of toxic water contaminants. Hybrid nanospheres’ sorption of two completely different categories of pollutants, i.e. metal ions such as Pb 2+, Cd 2+, Hg 2+, Cr 2O 7 2−, and polycyclic aromatic hydrocarbons such as pyrene and phenanthrene, was largely enhanced in comparison with the corresponding polymer-free silica nanospheres. This was attributed to the to the formation of conventional metal-ligand and charge-transfer complexes proving that although integrated into the silica network poly(ethylene imine) retains its chemical properties.

An Overview of Toxic Contaminants in Water and Sediments of the Great Lakes Part I

An Overview of Toxic Contaminants in Water and Sediments of the Great Lakes Part I

An Indexed Bibliography of Toxic Contaminants in Water, Sediments and Biota of the Great Lakes Part II

An Indexed Bibliography of Toxic Contaminants in Water, Sediments and Biota of the Great Lakes Part II

Aquatic bioassay of 11 pesticides using larvae of the mosquito, Wyeomyia smithii (Diptera: Culicidae).

One of the uses of aquatic bioassays is to determine the presence or absence of toxic contaminants in water from the field. Our Laboratory has developed a bioassay system for this purpose using larvae of the pitcher-plant mosquito, W eom ia smithii (Coquillett) (Strickman 1984). V The major app lcation of this system is the investigation of minor fish kills which may occur at any U.S. Air Force base. The system was developed around a number of requirements, including: (1) Simplicity so that it may be taught to technicians who rotate from their jobs frequently; (2) Economy of space and time; (3) Tolerance to uncontaminated water from a wide variety of sources; (4) Capability of testing small samples of water in order to reduce shipping costs; and (5) Capability of detecting toxicants at levels at or below the LC50 for common species of fish. The Wyeomyia bioassay proved to be a practical tool in the investigation of over 20 fish kills during 1983 and 1984. Toxicants detected by the bioassay were later identified as engine lubricating oil, copper, paint stripper, and high levels of free ammonia. Water from the sites of many of the fish kills produced no effect on larvae, indicating that the fish kills had not involved toxic contaminants or that contaminants had dissipated by the time of sampling or bioassay. Such negative results were important because they indicated that chemical analysis would probably not have been productive. Elimination of unnecessary analyses saved over $15,000 during a single year.