Natural Aquatic Systems Research Articles

Enhanced perchloroethene dechlorination by humic acids via increasing the dehalogenase activity of Dehalococcoides strains.

Perchloroethene (PCE) is a widely used chlorinated solvent. PCE is toxic to humans and has been identified as an environmental contaminant at thousands of sites worldwide. Several Dehalococcoides mccartyi strains can transform PCE to ethene, and thus contribute to bioremediation of contaminated sites. Humic acids (HA) are ubiquitous redox-active compounds of natural aquatic and soil systems and have been intensively studied because of their effect in electron transfer. In this study, we observed the dechlorination of PCE was accelerated by HA in mixed cultures containing Dehalococcoides strains. Anthraquinone-2,6-disulfonic acid (AQDS), a humic acid analogue, inhibited PCE dechlorination in our cultures and thus induced an opposite effect on PCE dehalogenation than HA. We observed the same effect on PCE dechlorination with the pure culture of Dehalococcoides mccartyi strain CBDB1. Not only in mixed cultures but also in pure cultures, growth of Dehalococcoides was not influenced by HA but inhibited by AQDS. Enzymatic activity tests confirmed the dehalogenating activity of strain CBDB1 was increased by HA, especially when using hydrogen as electron donor. We conclude that HA enhanced PCE dechlorination by increasing the reaction speed between hydrogen and the dehalogenase enzyme rather than acting as electron shuttle through its quinone moieties.

Controls on groundwater selenium, arsenic and base metals in groundwater around a selenium-bearing volcanogenic massive sulfide deposit: constraints from stable isotopes, trace elements and redox controls

Understanding the controls on the behaviour of metalloids (Se, As) and metals (Cu, Zn, Pb) in natural aqueous systems is vital to interpreting hydrogeochemical data in environmental and mineral exploration applications. Geochemical, isotopic and redox measurements of a suite of groundwaters sampled from around the ABM zone of the Kudz Ze Kayah (KZK) volcanogenic massive sulfide (VMS) deposit in the Yukon, Canada are presented and contrasted with other case studies from a variety of mineral deposit types. This deposit has atypically high As (up to 4.3 wt%, average 2457 ppm) and Se (up to 2620 ppm, average 157 ppm) contents in the sulfide mineralization. As a relatively undisturbed deposit (unmined), it is an ideal site to study the mobility and solubility of trace metals in groundwaters. Herein we present field measurements (pH, dissolved oxygen, specific conductance, oxidation–reduction potential and temperature), major ion, trace element, anion (Cl, Br, SO 4 , PO 4 ), and stable isotope ( δ 2 H, δ 13 C DIC , δ 18 O, δ 18 O SO4 , δ 34 S) data. Waters are dominantly low-salinity HCO 3 to HCO 3 –SO 4 -type waters with variable sulfate (4.83 to 601 mg l −1 ), Ca (23–235 mg l −1 ) Mg (3.1–96.8 mg l −1 ), Na (0.30–66.9 mg l −1 ) and K (0.55 to 6.25 mg l −1 ) concentrations. These waters also have variable trace element concentrations that include As (0.01 to 148 µg l –1 ), Se (<0.02 to 1.01 µg l –1 ), Fe (0.01 to 3.84 mg l −1 ), Zn (<0.2 to 1070 µg l –1 ), Pb (<0.01 to 8.4 µg l –1 ), Cu (0.03 and 24.5 µg l –1 ) and Sb (0.01 to 54.4 µg l –1 ). Some waters also have elevated concentrations (compared to most meteoric waters) of Nb (up to 0.3 µg l –1 ), Y (up to 1.42 µg l –1 ), Zr (up to 18 µg l –1 ), and the rare-earth elements (REEs) ( Σ REE up to 2.04 µg l –1 ). The δ 18 O (−22.8 to −20.9 ‰) and δ 2 H (−174 to −158 ‰), together with the δ 13 C DIC (−10.6 to +1.9 ‰), δ 34 S (+10 to +12 ‰) and δ 18 O SO4 (15.5 to −4.75 ‰) all suggest that local meteoric water has interacted with massive sulfide mineralization at the ABM zone. Our results demonstrate the requirement for the use of multiple techniques in hydrogeochemical studies, with dissolved concentrations of major and trace elements coupled with a suite of stable isotopes that help define a larger geochemical footprint for the KZK deposit. Water–mineral interaction between groundwater aquifers and VMS deposits like the ABM zone are distinctly different from dispersion halos described from other deposit types (i.e. Cu porphyry, unconformity U). Thematic collection: This article is part of the Hydrochemistry related to exploration and environmental issues collection available at: https://www.lyellcollection.org/cc/hydrochemistry-related-to-exploration-and-environmental-issues

Surfactant suspended multi-wall carbon nanotube stability in artificial water samples of different hydrogeochemical families

We investigated the multiwalled carbon nanotubes (MWCNTs) stability (ability to stay in the water column) in aqueous solutions meant to emulate the ionic nature of the major types of natural waters with the idea of simulating their behavior and possible interactions in natural aqueous systems. Synthesized MWCNTs were suspended in anionic, non-ionic, and cationic surfactants. Subsequently, the MWCNTs were added to: a) solutions containing Ca2+, Mg2+, or Na+, and b) four types of artificial waters (sodium carbonate, calcium carbonate, sodium chloride, and magnesium sulfate). Its stability was determined using UV–Vis spectroscopy and transmission electron microscopy. The MWCNTs stability was found to be a function of the concentration and valence of the major water cations and was higher when suspended in anionic and non-ionic surfactants as compared to a cationic surfactant. The results of this study suggest that MWCNTs suspended in cationic surfactants might sediment independently of the type of water, while MWCNTs suspended in anionic and non-ionic surfactants may remain in the column of a sodium chloride type water. This study helps to better understand the behavior and likely fate of MWCNTs in natural aqueous systems, a topic that gains growing importance as the production and application of these types of nanomaterials are increasing.

Caffeine and canopy cover interact to alter biofilm nutrient content, benthic invertebrates, and insect emergence

AbstractThe addition of trace contaminants to surface waters is recognized as a rising environmental concern and caffeine is among those most commonly detected. Classic toxicological analyses of single organisms have described some of the impacts of caffeine on freshwater organisms, but few have examined ecological interactions, food webs, or aquatic‐terrestrial linkages, especially in natural aquatic systems. This study used an in situ manipulative experiment to effects of caffeine addition on aquatic biofilms and biomass of aquatic and emergent insects. We used chemical diffusing substrata to introduce small concentrations of caffeine to streams and analyzed effects on downstream biofilm nutrient content, benthic macroinvertebrates, and emergent insects. We found that caffeine addition decreased the biomass of emergent insects by 56% and altered biofilm nutrient content in complex ways that interact with canopy cover, with stronger effects of caffeine addition under low canopy cover (higher light). Thus, the impacts of this common aquatic contaminant may influence the linked riparian food web by decreasing emergent insects, an important food source for riparian insectivores.

Occurrence and distribution of Carbapenem-resistant Enterobacterales and carbapenemase genes along a highly polluted hydrographic basin

We determined the distribution and temporal variation of Carbapenem Resistant Enterobacterales (CRE), carbapenemase-encoding genes and other antibiotic resistance genes (ARGs) in a highly polluted river (Lis River; Portugal), also assessing the potential influence of water quality to this distribution.Water samples were collected in two sampling campaigns performed one year apart (2018/2019) from fifteen sites and water quality was analyzed. CRE were isolated and characterized. The abundance of four ARGs (blaNDM, blaKPC, tetA, blaCTX-M), two Microbial Source Tracking (MST) indicators (HF183 and Pig-2-Bac) and the class 1 integrase gene (IntI1) was measured by qPCR. Resultsconfirmed the poor quality of the Lis River water, particularly in sites near pig farms. A collection of 23 CRE was obtained: Klebsiella (n = 19), Enterobacter (n = 2) and Raoultella (n = 2). PFGE analysis revealed a clonal relationship between isolates obtained in different sampling years and sites. All CRE isolates exhibited multidrug resistance profiles. Klebsiella and Raoultella isolates carried blaKPC while Enterobacter harbored blaNDM. Conjugation experiments were successful for only four Klebsiella isolates. All ARGs were detected by qPCR on both sampling campaigns. An increase in ARGs and IntI1 abundances was detected in sites located downstream of wastewater treatment plants. Strong correlations were observed between blaCTX-M, IntI1 and the human-pollution marker HF183, and also between tetA and the pig-pollution marker Pig-2-bac, suggesting that both human- and animal-derived pollution in the Lis River are a potential source of ARGs. Plus, water quality parameters related to eutrophication and land use were significantly correlated with ARGs abundances. Our findings demonstrated that the Lis River encloses high levels of antibiotic resistant bacteria and ARGs, including CRE and carbapenemase-encoding genes. Overall, this study provides a better understanding on the impacts of water pollution resulting from human and animal activities on the resistome of natural aquatic systems.

The curious case of methylparaben: Anthropogenic contaminant or natural origin?

The widespread use of methylparaben as a preservative has caused increased exposure to natural aquatic systems in recent decades. However, current studies have suggested that exposure to this compound can result in endocrine disrupting effects, raising much concern regarding its environmental impact. In contast, methylparaben has also been found to be part of the metabolome of some organisms, prompting the question as to whether this compound may be more natural than previously assumed. Through a combination of field studies investigating the natural presence of methylparaben across different taxa, and a 54-day microcosm experiment examining the bioaccumulation and movement of methylparaben across different life stages of aquatic insects (order Trichoptera), our results offer evidence suggesting the natural origin of methylparaben in aquatic and terrestrial biota. This study improves our understanding of the role and impact this compound has on biota and challenges the current paradigm that methylparaben is exclusively a harmful anthropogenic contaminant. Our findings highlight the need for further research on this topic to fully understand the origin and role of parabens in the environment which will allow for a comprehensive understanding of the extent of environmental contamination and result in a representative assessment of the environmental risk that may pose.

Iron Sulfide Solubility Measurement and Modeling Over Wide Ranges of Temperatures, Ionic Strength, and pH

Summary Iron sulfides constitute a diverse group of solid phases and aqueous complexes, many of which are critical in both natural and industrial processes, such as marine sedimentation, oil and gas productions, metallic equipment corrosion by hydrogen sulfide, and water treatment, to mention a few. As the fundamental basis of related research on iron sulfides, an accurate thermodynamic model for iron sulfide solubility prediction under wide ranges of conditions (e.g., water compositions, temperature, pressure, and pH) is required. In this study, a plug flow reactor was built to measure iron sulfide solubility at various temperatures (25–90°C), pH (5.9–6.9), and ionic strength (0.150–4.27 mol/kg). Using the mackinawite solubility data measured in this study and in literature, a new Pitzer theory-based thermodynamic model with the explicit presence of ion complexes was developed. In this model, a neutral aqueous ion complex, FeSaq, was included explicitly. The mackinawite solubility product constant was fitted with a temperature-dependent equation from 23 to 125°C: pKsp,m=−94.97+4,444TK+14.64×ln(TK), with TK as temperature in Kelvin. This model can accurately predict the mackinawite solubility with standard error of estimate (SEE) of the mean SI = ±0.015 SI units, under wide ranges of temperature (23–125°C), pH (3.16–9.66), ionic strength (0–5 mol/kg water), and Fe(II) to S(-II) molar ratio (from 1:1,000 to 10,000:1). The Gibbs free energy and enthalpy of formation for mackinawite were also derived. This new model could help improve FeS scaling and corrosion control in complicated industrial systems, as well as the sulfide-related heavy metal transport in natural aqueous systems.

On the dissolution of a borosilicate glass with the use of isotopic tracing – Insights into the mechanism for the long-term dissolution rate

An understanding of the mechanisms responsible for controlling the long-term corrosion rate of nuclear waste glass is paramount if reliable glass dissolution models are to be used to calculate the controlled release of radionuclides from nuclear waste glass under geologic disposal conditions. Understanding the mechanism that controls silicate glass dissolution rates is also important for natural glasses to understand the role from the dissolution of these glasses has on the composition of natural aquatic systems. Two general mechanisms appear to be responsible for the elemental release from glass to the surrounding biosphere – ion exchange (release principally of alkalis) and matrix dissolution (release of the structural components of the glass). Key unknowns related to these mechanisms are the impact of surface layers on the altered glass and how these layers participate in corrosion. To better understand the impact of these layers on the long-term glass corrosion rate, we made two glasses of the same elemental composition, but with selected elements enriched in specific isotopes for B (11B), Li (6Li), and Si (29Si). We reacted these glasses for 1 y then the solutions from each were exchanged and the chemistry of the solutions and the solids were followed for another 2 y (a total of 3 y). This allowed us to follow changes in the glasses with respect to these elements and how these elements were transported through the alteration layers with time and, for at least one element, into the glass and to deconvolute some competing kinetic steps, such as matrix dissolution and ion exchange. Results from these experiments demonstrate that the release behavior of different elements is strongly dependent on their structural role in the glass (e.g. network formers and modifiers), but, more importantly, the role of water transport and subsequent ion exchange has in the long-term dissolution of the glass studied here. In this article, we highlight the behavior of four elements: lithium, sodium, silicon, and boron. Lithium and sodium, network modifying elements, have similar chemistries. The behavior of Li could be tracked in more detail by following both 6Li and 7Li; Li penetrates through the gel layer in both directions without hinderance and is released from the glass deeper than Na. Silicon, a network forming element, reacts with the silica-rich alteration layer. Boron, a network forming element, does not accumulate in the gel or the pristine glass and has a very sharp elemental profile between the pristine glass and alteration layer. Boron, lithium, and sodium elemental profiles suggest that there is little if any transport control within the alteration layer. These results are similar to those found for basalt glass. However, the correlation between the Li and Na profiles and that of a water species suggest that the limiting release is not controlled by the formation of the gel but rather is a steady state between the diffusion of a water species and matrix dissolution that results in a low release rate for alkali and this provides a steady driving force for the long-term dissolution of glass.

Efficiency and specificity of CARD-FISH probes in detection of marine vibrios.

Vibrio is a bacterial genus widely distributed in natural aquatic systems. Some Vibrio species can cause severe diseases in both marine organisms and humans. Previous studies revealed a link between the current climate change and increased incidence of the Vibrio-associated diseases recently causing sanitary, economic and/or ecological problems worldwide. The conventional culture-based methods (e.g. selection on TCBS agar) used to monitor the presence of Vibrio spp. in environmental samples are not always straightforward and can underestimate the number of cells, especially in microbial populations containing a fraction of 'dormant' cells (e.g. cells in the Viable but Non Culturable [VBNC] state). This problem can be overcome by using alternative culture-free approaches such as Catalysed Reporter Deposition-Fluorescence In situ Hybridization (CARD-FISH). To select an efficient CARD-FISH probe for detection of Vibrio spp. in environmental samples, we have assessed the most promising probes described in the literature by using both computer-assisted and experimental approaches. Our results demonstrate that the use of the optimized protocol along with a very specific probe, ViB572a, can offer the high sensitivity and selectivity of CARD-FISH detection of marine vibrios in natural seawater.

Understanding the effects of periodic freshening and salinization on coastal water quality and aquifer sediments through laboratory-based column experiments

The coastal aquifers experience periodic freshening and salinization events due to frequent changes in hydrological conditions. Such frequent changes have vital effects on the coastal groundwater quality and aquifer properties. This forms the basis of the present study. Laboratory-based column experiments have been conducted to investigate the long-term impact of such periodic events on coastal groundwater quality and aquifer sediment characteristics. Conditions similar to the natural coastal aquifer systems were generated in sediment-filled columns by injecting freshwater and seawater periodically. Changes in pore water chemistry and sediment properties were monitored over a period of one year. It has been observed that periodic injections of freshwater (freshening) and seawater (salinization) caused significant changes in the pore water chemistry, mainly due to sediment-water interactions. In addition to seawater-freshwater mixing, geochemical processes such as ion-exchange, mineral precipitation/dissolution, and adsorption/desorption of elements have been identified to control the pore water chemistry. Trace elements, including barium, boron, bromide, lithium, and strontium, have been identified as effective tracers for monitoring the saltwater intrusion. Further, the changes in pore water chemistry are found to be interlinked with the changes in aquifer properties. It is observed that with the increase in the number of salinization cycles, the effectiveness of the freshening process to bring back the original aquifer pore water chemistry diminishes, and the impact of salinization lasts longer. At the end of the experiment, changes in the porosity and permeability of the sediments have been observed. Such changes in the aquifer properties may affect the specific yield and storativity of the aquifer.

In situ fractionation and redox speciation of arsenic in soda lakes of Nhecolândia (Pantanal, Brazil) using the diffusive gradients in thin films (DGT) technique

In situ fractionation and redox speciation of As in three different saline-alkaline lakes (green, black and crystalline lakes) in the Pantanal of Nhecolândia (Brazil) were performed by using Diffusive Gradients in Thin films (DGT). The results indicated that As is present mainly in dissolved form. Total As concentration was similar when using different filter membranes, demonstrating that the species adsorbed by DGT devices were <10 kDa. Higher concentrations of labile total As were observed in the center of the lakes, indicating that the nature of the organic matter influences the formation of As complexes. Total As concentrations determined by using ZrO2 DGT were consistent with As concentration in ultrafiltered water samples collected in the black lake. However, part of the data about As(III) obtained in grab samples contrasted with DGT results. The differences observed may indicate that alterations in the species occur during the storage period before analysis by ultrafiltration. As(III) concentrations measured by DGT in the black and crystalline lakes were 1-3 μg L-1 and 4-7 μg L-1, respectively, accounting for only 4%–8% of the total DGT inorganic As. In the green lake, As(III) concentrations were significantly higher at the center (217 μg L−1). Both the phytoplankton community and the dissolved organic carbon influence the As speciation and bioavailability in the lakes of Nhecolândia. The DGT approach used in the present work was able to perform As speciation and demonstrates that in situ sampling analytical techniques are essential in understanding As speciation and its behavior in complex natural aquatic systems.

Effects of long-term exposure to silver nanoparticles on the structure and function of microplastic biofilms in eutrophic water

Microplastics are frequently detected in natural aquatic systems proximate to populated areas, such as urban rivers and lakes, and can be rapidly colonized by microbial communities. Microplastics and silver nanoparticles (AgNPs) share similar pathways into natural waters and tend to form heteroaggregations. However, very little is known about the long-term impacts on the structure and function of microplastic biofilms when chronically exposed to silver nanoparticles. Thus, the present study assessed the accumulation property of AgNPs on polymethyl methacrylate (PMMA) microplastics via adsorption tests and studied the chronic effects of AgNPs on the structure and function of microplastic biofilms via 30-day microcosmic experiments in eutrophic water. The adsorption tests showed that the biofilms-colonized PMMA microplastics presented the highest adsorption of 0.98 mg/g in the 1 mg/L AgNPs microcosms. After the 30-day exposure, lactic dehydrogenase release and reactive oxygen species generation of PMMA biofilms increased by 33.23% and 23.98% compared to the MPs-control group with no-AgNPs, indicating that the number of dead cells colonizing microplastics significantly increased. Network analysis suggested that the stabilization of the bacterial community declined with the long-term exposure to AgNPs through the reduction of the modularity and average path length of the network. Compared to the MPs-control group, long-term exposure to AgNPs caused cumulatively inhibitory effects on the nitrogen removal and the N2O emissions in eutrophic water. The isotopomer analysis revealed that the contribution rate of NO2− reduction to N2O emissions was gradually increasing with the AgNPs exposure. Real-time PCR analysis showed that denitrification genes were less sensitive to AgNPs than the nitrification genes, with gene nosZ performed the most negligible response. Overall, our results revealed that long-term exposure to AgNPs could alter biogeochemical cycling involved by microplastic biofilms and cumulatively reduce the self-recovery of the eutrophic ecosystem.

The value of human data annotation for machine learning based anomaly detection in environmental systems

Anomaly detection is the process of identifying unexpected data samples in datasets. Automated anomaly detection is either performed using supervised machine learning models, which require a labelled dataset for their calibration, or unsupervised models, which do not require labels. While academic research has produced a vast array of tools and machine learning models for automated anomaly detection, the research community focused on environmental systems still lacks a comparative analysis that is simultaneously comprehensive, objective, and systematic. This knowledge gap is addressed for the first time in this study, where 15 different supervised and unsupervised anomaly detection models are evaluated on 5 different environmental datasets from engineered and natural aquatic systems. To this end, anomaly detection performance, labelling efforts, as well as the impact of model and algorithm tuning are taken into account. As a result, our analysis reveals the relative strengths and weaknesses of the different approaches in an objective manner without bias for any particular paradigm in machine learning. Most importantly, our results show that expert-based data annotation is extremely valuable for anomaly detection based on machine learning.

Selective Separation of Radiocesium from Complex Aqueous Matrices Using Dual Solid-Phase Extraction Systems

The release of radiocesium (r-Cs) into natural aqueous systems is of concern because of its extended solubility as an alkaline metal ion and its facile incorporation into living beings. A technique for the selective separation of Cs from an aqueous matrix using dual solid-phase extraction (SPE) systems in a series is proposed in this paper. The SPEs equipped with chelates (Nobias Chelate-PA1 and Nobias Chelate-PB1), an ion-exchange resin (Nobias Ion SC-1), or macrocycles (MetaSEP AnaLig Cs-01 and MetaSEP AnaLig Cs-02) were evaluated in terms of selectivity and retention/recovery behavior toward Cs and other potentially competing ions (Li, Na, K, Rb, Ba, Ca, Mg, and Sr). The simulated solution of 133Cs, a chemical analog of r-Cs, was used to optimize the separation process. Operating parameters such as pH (3–13), flow rate (0.2–5.0 mL min–1), and elution behavior (HCl, 0.1–5.0 mol L−1) were optimized to ensure maximum removal of Cs from the aqueous matrices. The dual SPE system comprised Nobias Chelate-PB1 that minimized the competing impact of ions, while selective Cs retention was attained with MetaSEP AnaLig Cs-02. The proposed process was verified using real r-Cs-contaminated water from Fukushima, Japan, to observe the quantitative separation and preconcentration of r-Cs from the complex matrices.

Oxygen isotope exchange rates between phosphate and water catalyzed by inorganic pyrophosphatase: Implications for the biogeochemical cycle of phosphorus

The oxygen isotope composition of phosphate (δ18OPO4) has been widely used as (paleo)temperature and bio-signature proxies and a tracer of biogeochemical cycling of phosphorus (P). In natural aqueous systems, reactive inorganic phosphorus is dominantly present as dissolved inorganic phosphate (DIP), and reactions involving DIP are primarily carried out by microorganisms and catalyzed by enzymes. One enzyme suggested to dominate P-cycling in nature is inorganic pyrophosphatase (PPase), a ubiquitous intracellular enzyme that catalyzes oxygen (O) isotope exchange between DIP and water. Herein, we determined PPase-catalyzed O-isotope exchange rates between DIP and water over the range of typical Earth surface temperatures (3 - 37°C) using isotope ratio mass spectrometry (IRMS). Exchange rates determined at pH 7.4 and between 3 and 37°C, were described by first-order reaction kinetics (rate constant k = 1.51E-05 to 3.13E-04 sec−1; half-life of reaction t1/2 = 37 to 765 minutes), and strongly dependent on temperature. The temperature dependence of the exchange reaction was fitted by the Arrhenius equation, with an activation energy of 61.8 kJ/mole. The rate of PPase-catalyzed O-isotope exchange is ca. 7 - 8 orders of magnitude faster than the rate of abiotic reactions (pH 5) at 37°C calculated by the extrapolation of high-temperature rate data. The results of this study can be used to improve the interpretation of measured δ18O values of phosphate preserved in the rock record or during biogeochemical reactions (e.g., deconvolution of simultaneous abiotic and enzymatic/microbial processes).

Rates of Abiotic MnII Oxidation by O2: Influence of Various Multidentate Ligands at High pH

Oxidation of manganous manganese (MnII) is an important process driving manganese cycles in natural aquatic systems and leading to the formation of solid-phase MnIII,IV (hydr)oxide products. Previous research has shown that some simple ligands (e.g., phosphate, sulfate, chloride, fluoride) can bind with MnII to make it unreactive to oxidation by dissolved oxygen. However, there is little to no understanding of the role played by stronger, complex-forming ligands in MnII oxidation reactions. The objective of this study was to evaluate the rates of abiotic MnII oxidation by O2 in the presence of low concentrations of several complex-forming model ligands (pyrophosphate, tripolyphosphate, ethylenediaminetetraacetic acid, oxalate) in bicarbonate-carbonate buffered laboratory solutions of pH 9.42, 9.65, and 10.19. The influence of increasing ligand concentrations on observed autocatalytic profiles of MnII oxidation was investigated, and initial oxidation rates were linked quantitatively to the initial MnII speciation in experimental solutions. Observed rates of MnII oxidation decreased with increasing ligand concentration for all four ligands tested. However, the profiles observed with time and the magnitudes of decrease in initial oxidation rates were different for the different ligands. Likely explanations for these observations include the denticity of the tested ligands, the relative strength of the ligands to complex MnII versus MnIII, and the ability of some ligands to enhance the reduction of MnIII back to MnII on a time scale comparable to the forward homogeneous MnII oxidation reaction.

Effect of mixing Nano-silica and Perlite with pervious concrete for nitrate removal from the contaminated water

Nitrogen and phosphorus contained in storm water runoff contaminate both surface and ground waters, causing problems for natural aquatic systems and human health. Pervious concrete particularly developed for pollutant removal might be a novel notion to remove nitrate from runoff. In this research, three aggregates were used in pervious concrete as Nano silica, perlite (Pe) and zeolite (Z) which are able to adsorb pollutants. The water absorption, compressive strength, porosity, permeability of aggregate and nitrate removal of concrete samples were evaluated in tests. While adding Nano silica, perlite and zeolite, experiments have shown that addition of fine grains enhances runoff efficiency and compressive strength, but reduces permeability and porosity. Both adsorbents improved the runoff quality while increasing the additives' ratio. The mechanical properties were density of 879 (Kg/m3), permeability of 1.06 (cm/s), the void rate of 19.7(%), compressive strength of 3.6 (MPa), and nitrate removal of about 75%. While adding perlite with the highest (40%) water absorption, the results showed no reactivity of aggregates in terms of alkali-silica reaction. Considering the Permeability tests, perlite has the minimum (1.4 cm/s) permeability, and then adding perlite to previous concrete brought the nitrate absorption capacity about 70 ml/g (60%). The best results belonged to samples containing zeolite treatments (with 15% adsorbent and 0, 10, 20% fine-grains) with a maximum pollution decline and improved Chemical Oxygen Demand (COD) (87.1, 82.6 and 89.3%), Biochemical oxygen demand (BOD) (88.1, 87.3 and 90.7%) and Total suspended solids (TSS) (75.8, 79.1 and 84.6%). Thus, zeolite has shown effective mechanical characteristics and runoff quality, while perlite and Nano silica has shown a poor and moderate performance among the adsorbents in all tests, respectively.

Synthesis, characterization, and assessment of novel sulfonated polynorbornene dicarboximides as adsorbents for the removal of heavy metals from water.

The occurrence of heavy metals in the natural aquatic systems arising from anthropogenic sources is an issue of global and environmental concern because of their extremely harmful effects to living beings even in rather low concentrations. The synthesis and ring-opening metathesis polymerization (ROMP) of novel norbornene dicarboximides bearing highly aromatic pendant groups, specifically, N-4-tritylphenyl-norbornene-5,6-dicarboximide (2a) and N-2,4,6-(triphenyl)phenyl-norbornene-5,6-dicarboximide (2b), their hydrogenation and further polymer sulfonation to render them adsorbents for the uptake of heavy metal ions from water is reported in this study. The macromolecules were characterized by means of FT-IR, 1H NMR, and thermal analysis, among others. A thoroughly kinetic and isothermal study of adsorption in single and ternary aqueous solutions of Pb2+, Cd2+, and Ni2+ was performed considering several experimental variables for instance initial metal concentration, contact time and solution pH. In general, the experimental data were adjusted more efficiently to the pseudo-second order kinetic model and to the Freundlich isotherm model, respectively. The maximum removal amounts were found to be 55.7 mg/g for Pb2+, 33.9 mg/g for Cd2+, and 10.2 mg/g for Ni2+ in the sulfonated trityl-bearing polymer 5a while those found for the sulfonated triphenyl-bearing polymer 5b were 31.5 mg/g for Pb2+, 26.6 mg/g for Cd2+, and 7.0 mg/g for Ni2+, respectively. The higher heavy metal removal capacity of polymer 5a was attributed to its also higher degree of sulfonation. The outcomes indicate that these novel sulfonic acid containing polymer-based adsorbents are effective for the uptake of heavy metallic elements from water.

Suckermouth armoured catfish (Pterygoplichthys spp.) menace in freshwater aquaculture and natural aquatic systems in Andhra Pradesh, India

Suckermouth armoured catfish (Pterygoplichthys spp.) which is popularly called “Devil fish” in Andhra Pradesh, was recorded in 93.33% of fish ponds out of 600 ha surveyed in Krishna and West Godavari districts including mesohaline ponds wherein salinity ranges from 2 to 20‰. Pterygoplichthys spp. have ranged from 150 to 600 kg/ha that accounts to 2.01-7.50% of total biomass of fish harvested in aquaculture ponds leading to escalation of feed conversion ratio by 25.76%. Consequently, carp production has diminished by 18.88% to 22.92% leading to economic losses to fish farmers up to 13.40%. Food chain disruption by this alien fish is not only confined to benthic algae and periphyton but also foraging on supplementary feeds leaving primary fishes deprived from availing feed. Abundance of Pterygoplichthys spp populations in culture ponds as also in canals was high in monsoon season when compared to winter. Invasion and abundance of Pterygoplichthys spp in various river systems in Andhra Pradesh has become major concern for fishers causing extensive damage to nets and gears as also retarded catch per unit effort resulting in minimization of their income by 30%. Efforts to extract fish hydrolysate from Pterygoplichthys spp were futile due to intense bony skeleton and poor recovery rate which projected utilization of this fish for allied activities to minimum. Abundance of Pterygoplichthys spp is increasing in confined and open water bodies due to their tolerance and ability to grow and breed in variety of aquatic habitats including polluted environments as also lack of effective predators thus poses a high risk and threat to native freshwater species in any ecosystem in which they get established.

Emerging investigator series: could the superoxide radical be implemented in decontamination processes?

The superoxide radical (O2˙−) is an important reactive oxygen species (ROS) in diverse natural aquatic systems and engineered water treatment processes.