Freshwater Samples Research Articles

Revolutionizing photocatalytic water treatment: An in-depth exploration of g-C3N4 iron oxide and carbon-mediated upgrading for an optimal decontamination of Vltava river water

Efficient water decontamination and bacterial eradication represent the core objectives of our study. Fresh water samples taken from the Vltava River were used in all experiments. The goal was achieved by synthesis of graphitic carbon nitride (g-C3N4) photocatalyst modified with a combination of carbon (C) and iron oxide (Fe3O4). Carbon and iron oxide nanoparticles with different loadings were incorporated within the g-C3N4 nano-sheets by the wet impregnation method. Heat treatment was applied in order to achieve photocatalyst and nanomaterials cohesion. Photocatalysts and their precursors were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), ultraviolet-visible spectroscopy (UV–vis), photoluminescence, and Raman spectroscopy. The metal and non-metal sample composed of 1 C- 1Fe3O4/g-C3N4 revealed the best catalytic performance by eradicating bacterial species (N/N0 = 99.9%) under 30 min of light irradiation. The photocatalyst also showed a good activity in methylene blue (MB) degradation (C/C0 = 92%) under 180 min of visible light. The high activity of the treated photocatalyst 1 C- 1Fe3O4/g-C3N4 was attributed to an improvement in electrochemical properties and was also attributed to the double synergic mechanism due to the concurrent presence of iron and carbon nanoparticles in the g- C3N4 sheets. Moreover, the photocatalyst maintained a steady 99.9% bacterial degradation efficiency for 3 consecutive runs, proving its reusability. This exceptional catalytic activity, coupled with its stability and non-toxic nature shows the transformative potential of our material in revolutionizing water purification technologies. Our research underscores a significant progress towards addressing contaminants and energy challenges, and holds promise for a new era of sustainable water treatment.

Bioaccumulation of Titanium in diatom Cyclotella atomus Hust.

Diatomaceous earth or diatomite is a fossil rock deposit of diatoms made up of silica and other minerals. A distinguishing feature of diatoms that placed them in the single class of microalgae Bacillariophyceae, is the frustule, a transparent, hard-shelled cell wall. It's interesting to note that the diatom has specific proteins and enzymes for heavy metal detoxification and can intake and store more heavy metals in its frustule. Consequently, an attempt has been made in this study to determine the bioaccumulation of metals in the frustules of the diatom. Hence, a centric diatom was isolated from the freshwater sample collected from the Adyar River, Chennai, Tamil Nadu. The diameter of the cell was 5-7.5µm and 20-23 striations with radial arrangement. A single, dark off-center fultoportula and marginal fultoportula on the striae are found in the diatom. Additionally, one rimoportula between two marginal fultoportula distributed on the striae between the costa was also seen. As a result, the isolated diatom was morphologically identified as Cyclotella atomus Hust. Simultaneously, the bioaccumulation study reveals that the Titanium (Ti) was found accumulated in the frustules of the diatom incubated in the Ti-supplemented culture medium based on the scanning electron microscope-energy-dispersive X-ray analysis (SEM-EDAX). Therefore, the biogenic accumulation and fabrication of Titanium frustules in diatom have advantages in enhancing the efficiency of solar cells.

Evaluating the diversity of the enigmatic fungal phylum Cryptomycota across habitats using 18S rRNA metabarcoding

Fungi in the phylum Cryptomycota have been recovered in numerous environmental DNA (eDNA) surveys but are only known from five described genera of intracellular parasites. These fungi are common in aquatic and soil habitats, but little is known about their relative diversity and specificity among particular habitats. We surveyed Cryptomycota from 80 eDNA samples including freshwater, soil, and marine habitats using Cryptomycota-preferential primers coupled with long-amplicon PacBio sequencing (1.2 kb of the 18S rRNA gene region). We found that freshwater samples were the most diverse, comprising 175 operational taxonomic units (OTUs) of Cryptomycota and also showed a high abundance of the related algae-parasitic group Aphelidiomycota, while marine samples were the least diverse with 25 OTUs. The composition of Cryptomycota communities was influenced by habitat, with freshwater and soil showing statistically distinct communities. Phylogenetic analyses showed that the present survey recovered most previously sampled major clades of Cryptomycota, but most (61%) OTUs were novel to this study, indicative of an extensive diversity of the group that remains largely uncharacterized.

Protist taxonomic and functional diversity in aquatic ecosystems of the Brazilian Atlantic Forest.

The Brazilian Atlantic Forest and its associated ecosystems are highly biodiverse but still understudied, especially with respect to eukaryotic microbes. Protists represent the largest proportion of eukaryotic diversity and play important roles in nutrient cycling and maintenance of the ecosystems in which they occur. However, much of protist diversity remains unknown, particularly in the Neotropics. Understanding the taxonomic and functional diversity of these organisms is urgently needed, not only to fill this gap in our knowledge, but also to enable the development of public policies for biological conservation. This is the first study to investigate the taxonomic and trophic diversity of the major protist groups in freshwater systems and brackish coastal lagoons located in fragments of the Brazilian Atlantic Forest by DNA metabarcoding, using high-throughput sequencing of the gene coding for the V4 region of the 18S rRNA gene. We compared α and β diversity for all protist communities and assessed the relative abundance of phototrophic, consumer, and parasitic taxa. We found that the protist communities of coastal lagoons are as diverse as the freshwater systems studied in terms of α diversity, although differed significantly in terms of taxonomic composition. Our results still showed a notable functional homogeneity between the trophic groups in freshwater environments. Beta diversity was higher among freshwater samples, suggesting a greater level of heterogeneity within this group of samples concerning the composition and abundance of OTUs.Ciliophora was the most represented group in freshwater, while Diatomea dominated diversity in coastal lagoons.

Detailed insights in adsorption process of heavy metals on tire wear particles

Road traffic induced tire wear particles (TWP) attracted widespread attention due to their potential environmental impact. Here, the adsorption process of heavy metals like Pb2+ and Cd2+ on tire wear particles produced by filing (TWP-f) is studied to elucidate the underlying kinetics and thermodynamics. This work includes voltammetric experiments to investigate the concentration and temperature dependency of the adsorption. The adsorption kinetics in buffer solution spiked with heavy metals follows a pseudo-second-order rate equation involving rate-controlling boundary layer adsorption and a side-by-side intraparticle diffusion process. Meanwhile, the adsorption tendencies under the studied conditions for TWP-f were Pb2+ > Cd2+. The equilibrium adsorption data were modulated by the Langmuir, Freundlich, and Dubinin-Radushkevich (DR) isotherms. Both the Freundlich and DR isotherms were found to be feasible for describing the adsorption on TWP-f. The adsorption energy obtained from the DR isotherm is 1.6 kJ mol−1 for Pb2+ and 2 kJ mol−1 for Cd2+, indicating physisorption as the dominating force. According to the Freundlich isotherm, multilayer adsorption is proposed. The thermodynamic parameters show that the adsorption of Pb2+ and Cd2+ is endergonic. Due to small Gibbs enthalpy values near the thermodynamic equilibrium, the adsorption process is mainly dependent on the ambient conditions. So, close-to-nature experiments were conducted to verify the received results. Therefore, tire and road wear particles including road sediments (TRWP+RS) were added to prefiltered freshwater samples of the river Freiberger Mulde (having naturally elevated trace element concentrations). The adsorption kinetics were investigated by ICP-MS/MS emphasizing the pseudo-second-order rate equation. Moreover, it is suggested that the tire wear particles in the TRWP+RS sample are majorly responsible for the adsorption of at least Cd2+.

Performance, microbial growth and community interactions of iron-dependent denitrification in freshwaters

Iron-dependent denitrification is a safe and promising technology for nitrogen removal in freshwaters. However, the understanding of microbial physiology and interactions during the process was limited. Denitrifying systems inoculated with freshwater samples were operated with and without iron(II) at a low C/N ratio for 54 days. Iron addition improved nitrogen removal. Batch experiments confirmed that microbially mediated reaction rather than abiotic reaction dominated during the process. Metagenomics recovered genomes of the five most abundant microorganisms, which accounted for over 99% of the community in every triplicate of the iron-based system. Based on codon usage bias, all of them were fast-growing organisms. The total abundance of fast-growing organisms was 38% higher in the system with iron than in the system without iron. Notably, the most abundant organism Diaphorobacter did not have enzymes for asparagine and aspartate biosynthesis, whereas Rhodanobacter could not produce serine and cobalamin. Algoriphagus and Areminomonas lost synthesis enzymes for more amino acids and vitamins. However, they could always obtain these growth-required substances from another microorganism in the community. The two-partner relationship minimized the limitation on microbial reproduction and increased community stability. Our results indicated that iron addition improved nitrogen removal by supplying electron donors, promoting microbial growth, and building up syntrophic interactions among microorganisms with timely communications. The findings provided new insights into the process, with implications for freshwater remediation.

Evaluation of metal pollution related to human health risk in freshwater snail Viviparus contectus (Millet, 1813) as a potential bioindicator species in Lake Habitat (Turkey).

Freshwater mollusks are employed as bioindicators for the assessment of water quality in biomonitoring studies since the water quality of natural resources is crucial for humans. The freshwater snail species known as Viviparus contectus (Viviparidae: Gastropoda) is one that people eat. Here, the levels of heavy metals (Cd, Cr, Pb, As, Zn, and Cu) in water and V. contectus samples were determined. An Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES, Spectro Arcos, vertical plasma) was used for the analysing the heavy metal concentrations in water and freshwater snail samples. The results of the current investigation demonstrated that freshwater snails accumulated metals in their water and soft tissues in the following orders: Pb > Cr = Zn = Cu = Cd = As and Zn > Cu > Pb > Cd > As = Cr. Autumn was the time of year when higher amounts of heavy metals (As, Cr, Cu, Zn, and Hg) were found. Pb content in the freshwater snail samples was strongly impacted by seasonal fluctuations (P 0.05). For adults, the EDI (estimated daily intake) values were lower than the TDI (tolerable daily intake) values, and the HI (hazard index) values were below 1. Freshwater snail samples had Zn and Pb levels that were over the FAO/WHO, Turkish Food Codex, JECFA, and EC limit values. Except for Pb, the water study shows mean metal concentrations below the USEPA, Turkish Pollution Control Regulation, and World Health Organisation maximum allowed levels. Aquatic ecosystems were negatively impacted by anthropogenic activities overall, and this study can provide a helpful data set for investigations on metallic contamination in water bodies and biomonitoring in freshwater ecosystems.

Denitrification fractionates N and O isotopes of nitrate following a ratio independent of carbon sources in freshwaters.

The stable isotope technique has been used in tracking nitrogen cycling processes, but the isotopic characteristics are influenced by environmental conditions. To better understand the variability of nitrate isotopes in nature, we investigated the influence of organic carbon sources on isotope fractionation characteristics during microbial denitrification. Denitrifying cultures were inoculated with freshwater samples and enriched with five forms of organic compounds, that is, acetate, citrate, glucose, cellobiose, and leucine. Though the isotope enrichment factors of nitrogen and oxygen (15 ε and 18 ε) changed with carbon sources, 18 ε/15 ε always followed a proportionality near 1. Genome-centred metagenomics revealed the enrichment of a few populations, such as Pseudomonas, Enterobacter, and Atlantibacter, most of which contained both NapA- and NarG-type nitrate reductases. Metatranscriptome showed that both NapA and NarG were expressed but to different extents in the enrichments. Furthermore, isotopic data collected from a deep reservoir was analysed. The results showed δ18 O- and δ15 N-nitrate did not correlate in the surface water where nitrification was active, but 18 ε/15 ε followed a proportionality of 1.05 ± 011 in deeper waters (≥ 12 m) where denitrification controlled the nitrate isotope. The independence of 18 ε/15 ε from carbon sources provides an opportunity to determine heterotrophic denitrification and helps the interpretation of nitrate isotopes in freshwaters.

FWAlgaeDB, an integrated genome database of freshwater algae

Algal genomics research contributes to a deeper understanding of algal evolution and provides useful genomics inferences correlated with various functions. Published algal genome sequences are very limited owing to genome assembly challenges. Because genome data of freshwater algae are rapidly increasing with the recent boom in next-generation sequencing and bioinformatics, an interface to store, interlink, and display these data is needed. To provide a substantial genomic resource specifically for freshwater algae, we developed the Freshwater Algae Database (FWAlgaeDB), a user-friendly, constantly updated online repository for integrating genomic data and annotation information. This database, which includes information on 204 freshwater algae, allows easy access to gene repertoires and gene clusters of interest and facilitates potential applications. Three functional modules are integrated into FWAlgaeDB: a Basic Local Alignment Search Tool tool for similarity analyses, a Search tool for rapid data retrieval, and a Download function for data downloads. This database tool is freely available at http://www.fwalagedb.com/#/home. To demonstrate the utility of FWAlgaeDB, we also individually mapped metagenomic sequencing reads of 10 water samples to FWAlgaeDB and Nt algae databases we constructed to obtain taxonomic composition information. According to the mapping results, FWAlgaeDB may be a better choice for identifying algal species in freshwater samples, with fewer potential false positives because of its focus on freshwater algal species. FWAlgaeDB can therefore serve as an open-access, sustained platform to provide genomic data and molecular analysis tools specifically for freshwater algae.

Comparative Assessment of Biodegradability Potential of Pseudomonas putida and Bacillus amyloliquefaciens on Oil Spill Dispersant (Aquabreak and Teepol) in Freshwater

To compare and assessment of Biodegradability Potential of Pseudomonas putida and Bacillus amyloliquefaciens on oil spill dispersant (Aquabreak and Teepol) in Freshwater. Fresh water sample were collected from Biara, Gokana L.G.A, and were transported to the Microbiology Laboratory of Rivers State University, Port Harcourt, Nigeria for analyses while Oil spill dispersant (OSD/Aquabreak) was purchased from Barker and Hughes, all in Rivers state. Nine experimental set up were carried out using Bacillus and Pseudomonas species as the bio-augmenting organism. Controls were made without organisms. Its bioremediation potential on the pollutants and two types of test organisms were monitored for 28 days at an interval of 7day period. The setup was aerated twice a week to provide more oxygen for the organisms to thrive. Analysis of samples were carried out using standard analytical procedures. The resultsphysiochemical property of the water shows that as follows: pH 6.5, Temperature 30.0 ºC, Electric conductivity 15 µs/cm, Total dissolved solid 7 mg/l ,Chlorine 0.1 mg/l, Bromine 0.2 mg/l, Salinity (0.01 mg/l), Dissolved oxygen 1.5 mg/l , Biological Oxygen Demand 0.3 mg/l, Nitrate 0.01 mg/l, Sulphate 4.18 mg/l Phosphate 0.10 to 1.5mg/l, Total Hydrocarbon content 24mg/l. Percentage (%) Ultimate biodegradability of the two oil spill dispersant OSD/teepol and OSD/aquabreak revealed that control set-up recorded the 79.3 and 86.7 % , bioremediation set-up augmented with Bacillus amyloliquefaciens recorded 93.7 and 99.1% while the set-up augmented with P. putida had 98.0 and 94.7% respectively . It was observed that P. putida degrade Teepol than Bacillus amyloliquefaciens while aquabreak is more degraded by Bacillus amyloliquefaciens than P. putida. Nevertheless both dispersant shown high level of degradability by the test organisms. Therefore It is recommended that oil companies and government parastatals carrying out remediation in the Niger Delta should be encouraged and OSD/Teepol and OSD/aqubreak due to their high biodegradation potential.

Comparative study of multiple approaches for identifying cultivable microalgae population diversity from freshwater samples.

The vast diversity of microalgae imposes the challenge of identifying them through the most common and economical identification method, morphological identification, or through using the more recent molecular-level identification tools. Here we report an approach combining enrichment and metagenomic molecular techniques to enhance microalgae identification and identify microalgae diversity from environmental water samples. From this perspective, we aimed to identify the most suitable culturing media and molecular approach (using different primer sets and reference databases) for detecting microalgae diversity. Using this approach, we have analyzed three water samples collected from the River Nile on several enrichment media. A total of 37 microalgae were identified morphologically to the genus level. While sequencing the three-primer sets (16S rRNA V1-V3 and V4-V5 and 18S rRNA V4 region) and aligning them to three reference databases (GG, SILVA, and PR2), a total of 87 microalgae were identified to the genus level. The highest eukaryotic microalgae diversity was identified using the 18S rRNA V4 region and alignment to the SILVA database (43 genera). The two 16S rRNA regions sequenced added to the eukaryotic microalgae identification, 26 eukaryotic microalgae. Cyanobacteria were identified through the two sequenced 16S rRNA regions. Alignment to the SILVA database served to identify 14 cyanobacteria to the genera level, followed by Greengenes, 11 cyanobacteria genera. Our multiple-media, primer, and reference database approach revealed a high microalgae diversity that would have been overlooked if a single approach had been used over the other.

The determination of dimethyl sulfoxide in natural waters using electrochemical reduction

AbstractA highly specific electrochemical reduction method has been developed that enables the trace level measurement of dimethyl sulfoxide (DMSO) concentration in natural waters. Following the sparging of native dimethyl sulfide (DMS) from the sample, DMSO is reduced to DMS using a novel electrochemical workflow that relies upon CuSO4 as a redox mediator. The DMS produced through DMSO reduction is collected, concentrated, and detected using a previously described Purge & Trap‐Atmospheric Pressure Chemical Ionization‐Tandem Mass Spectrometry (P&T‐APCI‐MS/MS) analytical workflow. The method provides a 0.5 pM detection limit for the analysis of DMSO in 10 mL sample volumes, with a demonstrated method precision of 5.4% for the analysis of consecutive 10 nM aqueous standards. The method selectivity for DMSO was evaluated using a range of commonly observed marine organosulfur compounds, none of which were found to interfere with the analysis at a reduction potential of 4 V. Method intercomparison confirmed that the electrochemical reduction provides results that are equivalent (at the 95% confidence level) to an established TiCl3 reduction protocol for the analysis of both freshwater and seawater samples. Relative to established methods of DMSO reduction, the electrochemical method provides excellent selectivity and reproducibility, and offers the potential for automated, high‐throughput analysis. In addition, the new electrochemical method does not require expensive, difficult to procure enzymes or hazardous, corrosive chemical reagents. Depth profile measurements of DMSO, DMS, and dimethylsulfoniopropionate (DMSP) for unfiltered seawater samples collected in Saanich Inlet, a coastal fjord in British Columbia, demonstrate the effectiveness of the DMSO reduction method in an oceanographic context.

Physiochemical Analysis of River Sutlej, Sindh and the Arabian Sea to Evaluate the Water Quality

Globally, water pollution is caused primarily by growing populations, urbanization, and modern agricultural techniques. In this study, freshwater samples were collected from Satluj river, Sindh river, and Arabian sea to assess water quality. A variety of physicochemical parameters were measured in these samples, including pH (7.5 to 8.4), color (variable), odor, turbidity (7 NTU to 18 NTU), taste (salty/bitter), total dissolved solids (182 mg/L to 34768 mg/L), total soluble solids (52 mg/L to 1244 mg/L), EC (109 µS/cm to 51488 µS/cm), total hardness/Ca+2+Mg+2 (25 mg/L to 125 mg/L), total alkalinity or CO3 -2 , HCO3 - (80 mg/L to 172 mg/L), exchangeable ions like Cl- (27 mg/L to 19742 mg/L), F- (0.3 mg/L to 1.29 mg/L), SO4 -2 (30 mg/L to 2974 mg/L), PO4 -3 (8 mg/L to 35 mg/L), NO2 -2 (18 mg/L to 43 mg/L), Mn+2 (0.0002 mg/L to 0.63 mg/L), Cu (0.0005 mg/L to 0.08 mg/L), Cd+2 (0.0005 mg/L to 0.88 mg/L), Cr+3 (0.003 mg/L to 0.32 mg/L), Zn+2 (0.001 mg/L to 2.72 mg/L), Fe+2 (0.01 mg/L to 0.9 mg/L), Ni+2 (0.002 mg/L to 0.23 mg/L), Na+ (15 mg/L to 10157 mg/L), K+ (4.4 mg/L to 379 mg/L), Ca+2 (20 mg/L to 380 mg/L), Mg+2 (5.4 mg/L to 1584 mg/L) tested by standard methods reported in Association of Official Analytical Chemists (AOAC) with little modifications. Most of the parameters studied in these water samples were beyond the National Environment Quality Standard of drinking water guidelines for seawater, but within acceptable limits for rivers. Consequently, these trends made seawater unfit for the survival of aquatic plants and marine life as well as for the people who use river water for domestic and agricultural purposes.

Fabrication of graphene oxide-based pretreatment filter and Electrochemical-CRISPR biosensor for the field-ready cyanobacteria monitoring system

Microcystis aeruginosa (M. aeruginosa) cause the eutrophication of lakes and rivers. To effectively control the overgrowth of M. aeruginosa, a suitable measurement method should be required in the aquatic fields. To address this, we developed a field-ready cyanobacterial pretreatment device and an electrochemical clustered regularly interspaced short palindromic repeats (EC-CRISPR) biosensor. The cyanobacterial pretreatment device consists of a syringe, glass bead, and graphene oxide (GO) bead. Then, the M. aeruginosa dissolved in the freshwater sample was added to fabricated filter. After filtration, the purified gene was loaded onto a CRISPR-based electrochemical biosensor chip to detect M. aeruginosa gene fragments. The biosensor was composed of CRISPR/Cpf1 protein conjugated with MXene on an Au microgap electrode (AuMGE) integrated into a printed circuit board (PCB). This AuMGE/PCB system maximizes the signal-to-noise ratio, which controls the working and counter electrode areas requiring only 3 μL samples to obtain high reliability. Using the extracted M. aeruginosa gene with a pre-treatment filter, the CRISPR biosensor showed a limit of detection of 0.089 pg/μl in fresh water. Moreover, selectivity test and matrix condition test carried out using the EC-CRISPR biosensor. These handheld pre-treatment kit and biosensors can enable field-ready detection of CyanoHABs.

The effect of metabarcoding 18S rRNA region choice on diversity of microeukaryotes including phytoplankton.

Metabarcoding using high throughput sequencing of amplicons of the 18S rRNA gene is one of the widely used methods for assessing the diversity of microeukaryotes in various ecosystems. We investigated the effectiveness of the V4 and V8-V9 regions of the 18S rRNA gene by comparing the results of metabarcoding microeukaryotic communities using the DADA2 (ASV), USEARCH-UNOISE3 (ZOTU), and USEARCH-UPARSE (OTU with 97% similarity) algorithms. Both regions showed similar levels of genetic variability and taxa identification accuracy. Richness for DADA2 datasets of both regions was lower than for UNOISE3 and UPARSE datasets, which is due to more accurate error correction in amplicons. Microeukaryotic communities (autotrophs and heterotrophs) structure identified using both regions showed a significant relationship with phytoplankton (autotrophs) communities structure based on microscopy in a seasonal freshwater sample series. The strongest relationship was found between the phytoplankton species and V8-V9 ASVs produced by DADA2.

Degradation of 75 organic micropollutants in fresh human urine and water by UV advanced oxidation process

In household wastewater, a large proportion of organic micropollutants (OMPs) load is attributed to human urine. OMPs could pose a risk to human and environmental health when urine collected in source-separating sanitation systems is recycled as crop fertiliser. This study evaluated degradation of 75 OMPs in human urine treated by a UV-based advanced oxidation process. Fresh urine and water samples were spiked with a broad range of OMPs and fed into a photoreactor equipped with a UV lamp (185 and 254nm) that generated free radicals in situ. Degradation rate constant and the energy required to degrade 90% of all the OMPs in both matrices were determined. At a UV dose of 2060J m-2, average ΣOMP degradation of 99% (±4%) in water and 55% (±36%) in fresh urine was achieved. The energy demand for removal of OMPs in water was <1500J m-2, but for removal of OMPs in urine at least 10-fold more energy was needed. A combination of photolysis and photo-oxidation can explain the degradation of OMPs during UV treatment. Organic substances (e.g. urea, creatinine) likely inhibited degradation of OMPs in urine by competitively absorbing UV-light and scavenging free radicals. There was no reduction in the nitrogen content of urine during treatment. In summary, UV treatment can reduce the load of OMPs to urine recycling sanitation systems.

Experimental assessment the effects of saline discharge on plankton community of the recipient freshwater ecosystem – Inputs to scientific ballast water management of inland ports

Expanding international trade has accelerated the transfer of ballast water worldwide, the change in salinity is expected to be detrimental to recipient areas’ species, especially to freshwater ports’. This study simulated the changes in freshwater plankton community with respect to salinity stress resulting from ballast water discharged. The prepared saline water (simulates ballast water that meets D-2 standards) was discharged into the collected freshwater samples (from natural lake) at different volume ratios, which represented the salinity changes in localized areas of the receiving waters. The samples were counted and identified for ≥ 10–50 µm and ≥ 50 µm organisms with FDA (Florescein Diacetate) & CMFDA (Chloromethylflurescein Diacetate) method and Microscope counting method. From the first day after saline water discharged, it was found that when water salinity reached 12.2 PSU (Practical salinity units), the density of ≥ 50 µm organism was about 0 ind./m3, while only when water salinity reached 24.8 PSU, the density of ≥ 10–50 µm organisms was 0 cells/mL from the sixth day after saline water discharged. When the salinity was less than or equal to 2.1 PSU, the composition of species of ≥ 50 µm organisms in samples were similar to the control group, but for ≥ 10–50 µm organisms, when the salinity was less than or equal to 6.5 PSU, the community structure in samples were similar to the control group. The ≥ 10–50 µm and ≥ 50 µm organisms, these two groups were differently responsive to the changes in salinity. Besides, when the change of water salinity doesn’t exceed 6.5 PSU, the density of plankton first decreased and then increased, but when salinity changes exceed 6.5 PSU, the density of plankton exhibited a great decline during ten days. The results indicated that high-salt ballast water discharge could negatively affect freshwater harbor organisms, the salinity indicators could provide the basis for future studies of actual water samples, pay attention to the impact of ballast water discharge on inland ports is urgent.

Setting up of a sensitivity-modulable ELIMC assay for the determination of microcystins/nodularins in water samples

Herein, a sensitivity-modulable ELIMC (Enzyme-Linked Immuno-Magnetic Colorimetric) assay for the determination of microcystins/nodularins in water samples is presented. Firstly, we revisited a commercial ELISA microcystins/nodularins tube kit using Magnetic Beads as a solid phase of the immuno-complex. All immunological reactions occur in a single short-step procedure, followed by a colorimetric enzymatic reaction. The ELIMC assay showed a detection limit, sensitivity, working range and rapidity similar to those of the commercial kit but, thanks to the use of MBs, the analysis number was increased from 40 to 250, minimizing the use of reagents and therefore the waste generation, facilitating environmental sustainability. Satisfactory recovery and precision, obtained by analyzing controls, drinking and freshwater samples, directly without any pre-treatment, proved the suitability of the assay as a rapid screening method for numerous samples. Then, the analytical performance of the ELIMC assay was improved by making simple changes to the protocol. By doubling the enzyme-substrate reaction time and halving the concentration of the primary antibody a lower detection limit (0.03 ng/mL), an increased sensitivity (0.26 ng/mL) and a wider working range (0.05–2.0 ng/mL) were reached. Recovery from 84 to 120% and precision (RSD) from 7.3 to 16.6% demonstrated the reliability of the enhanced ELIMC assay to measure very low concentrations of MCs/NODs in water samples, allowing the adoption of timely corrective actions in the frame of environmental recovery programs.

Development of an Inexpensive, Rapid Method to Measure Nitrates in Freshwater to Enhance Student Learning

A laboratory experiment was designed and implemented in a STEM teaching laboratory at Michigan State University to engage students in an activity that not only introduced an innovative nitrate detection technique but also addressed one of the negative impacts of climate change, that is, the eutrophication of water bodies. The adverse effects of eutrophication on public health due to the presence of cyanotoxins make it crucial to monitor the trophic state of water bodies, which can be assessed by measuring the nitrate and phosphate concentrations. We developed a rapid method to measure nitrate concentrations in freshwater samples using a Hanna Instruments Checker, which was designed to measure nitrate levels in seawater. We identified the sample matrix that would maximize the accuracy of the Checker instrument for freshwater samples and validated the analytical method via ion chromatography. Students gained knowledge of other aspects of laboratory procedures, such as sample collection, sample storage, and material compatibility, which are often ignored during conventional teaching practices.

Influence of brine on hydration reaction of calcium sulfoaluminate and slag blended cement

A study was conducted to develop an eco-friendly, low-carbon cement and to find new applications for waste brine discharged from seawater desalination plants. As the binder, a binary blended binder of calcium sulfoaluminate type K expanding agent (CSA) classified as ACI 223R-10 and slag was used. The CSA content was 0%, 10%, 20%, and 30% substituted. For mixed water, freshwater and brine were used. The brine promoted the hydration reaction of the CSA to promote the formation of ettringite and increased the pore content of 50 nm or less to form a dense matrix, thereby improving the mechanical performance. The 20% CSA sample exhibited the best strength for freshwater and brine samples. However, for the 30% CSA, a decrease in strength was measured, which is due to the excessive expansion effect. Mixing the CSA–slag-blended cement and brine suggests the possibility of its application as a new construction material.