Unfiltered Samples Research Articles

Dynamics, distribution, and transformations of mercury species from pyrenean high-altitude lakes

While mercury (Hg) is a major concern in all aquatic environments because of its methylation and biomagnification pathways, very few studies consider Hg cycling in remote alpine lakes which are sensitive ecosystems. Nineteen high-altitude pristine lakes from Western/Central Pyrenees were investigated on both northern (France) and southern (Spain) slopes (1620–2600 m asl.). Subsurface water samples were collected in June 2017/2018/2019 and October 2017/2018 for Hg speciation analysis of inorganic mercury (iHg(II)), monomethylmercury (MMHg), and dissolved gaseous mercury (DGM) to investigate spatial and seasonal variations. In June 2018/2019 and October 2018, more comprehensive studies were performed in four lakes by taking water column depth profiles. Besides, in-situ incubation experiments using isotopically enriched Hg species (199iHg(II), 201MMHg) were conducted to investigate Hg transformation mechanisms in the water column. While iHg(II) (0.08–1.10 ng L−1 in filtered samples; 0.11–1.19 ng L−1 in unfiltered samples) did not show significant seasonal variations in the subsurface water samples, MMHg (<0.03–0.035 ng L−1 in filtered samples; <0.03–0.062 ng L−1 in unfiltered samples) was significantly higher in October 2018, mainly because of in-situ methylation. DGM (0.02–0.68 ng L−1) varies strongly and can exhibit higher levels in comparison with other pristine areas. Depth profiles and incubation experiments highlighted the importance of in-situ biotic methylation triggered by anoxic conditions in bottom waters. In-situ incubations confirm that significant methylation, demethylation and photoreduction extents are taking place in the water columns. Overall, drastic environmental changes occurring daily and seasonally in alpine lakes are providing conditions that can both promote Hg methylation (stratified anoxic waters) and MMHg photodemethylation (intense UV light). In addition, light induced photoreduction is a major pathway controlling significant gaseous Hg evasion. Global warming and potential eutrophication may thus have direct implications on Hg turnover and MMHg burden in those remote ecosystems.

Методика экспресс определения численности культур микроводорослей рода Tetraselmis

The article presents an algorithm for using spectrophotometric measurement to determine the number of cells of cultures of microalgae of the genus Tetraselmis filtered and unfiltered samples. The dependence "density – number of cells" is approximated by a linear equation with a high correlation coefficient, more than 75%, which confirms the high reliability of the method. The ability to measure the density of unfiltered culture samples on a spectrophotometer allows you to quickly estimate the number of cells both in the field and on an industrial scale.

Differential Behavior of Metal Sulfides in Hydrothermal Plumes and Diffuse Flows

Extensive sampling of high-temperature hydrothermal fluids and diffuse flows within <2 m of the vent orifices at the 9°50′N East Pacific Rise (EPR) hydrothermal vent field reveals formation of nanoparticulate phases and rapid precipitation/aggregation of metal sulfide minerals upon mixing of vent fluid with ambient seawater. Here, we characterize metal sulfide phases via scanning and transmission electron microscopy (SEM, TEM) in addition to quantifying the concentrations of major and trace metals in filtered and unfiltered fluid samples. Analyses demonstrate that, despite coprecipitation in phases such as chalcopyrite, iron speciation and transport is decoupled from that of copper and zinc. We observe the formation of ∼10–500 nm diameter (nano)particulate Zn and Cu sulfide phases that are near-quantitatively removed by filtration. Iron sulfides, conversely, are typically present in SEM images as larger particles up to tens of microns in diameter. Few small nanoparticles (20–100 nm diameter) are captured on the filter, but determination of nitric-acid-soluble iron in 0.2 μm filtered samples indicates the presence of pyrite nanoparticles. Physical mixing and temperature play a larger role in determining the extent of nanoparticulate pyrite formation than fluid chemistry. In diffuse flow environments, Fe and Cu more commonly co-occur as aggregates of very small crystallites, with the Zn sulfide phases occurring separately. Sample pH and the ZPC (zero point of charge) of metal sulfides exhibit chemical control on nanoparticle and large particle formation versus aggregation. The concentrations of the additional trace metals analyzed vary between vent sites, despite the short distances between the sites and likely similar magmatic sources. Measured trace metal concentrations highlight the importance of diffuse flow systems in hydrothermal metal emissions. These near-vent behavioral differences have implications for the long-distance transport of metals away from vent fields in buoyant and nonbuoyant plumes.

Removal of Extended-Spectrum Beta-Lactamase-Producing Escherichia coli, ST98, in Water for Human Consumption by Black Ceramic Water Filters in Low-Income Ecuadorian Highlands.

Fecal contamination in natural water sources is a common problem in low-income countries. Several health risks are associated with unprotected water sources, such as gastrointestinal infections caused by parasites, viruses, and bacteria. Moreover, antibiotic-resistant bacteria in water sources have become an increasing problem worldwide. This study aimed to evaluate the bacterial pathogens present in water within a rural context in Ecuador, along with the efficiency of black ceramic water filters (BCWFs) as a sustainable household water treatment. We monitored five natural water sources that were used for human consumption in the highlands of Ecuador and analyzed the total coliforms and E. coli before and after BCWF installation. The results indicated a variable bacterial contamination (29–300 colony-forming units/100mL) in all unfiltered samples, and they were considered as high risk for human consumption, but after filtration, no bacteria were present. Moreover, extended-spectrum beta-lactamase-producing E. coli with blaTEM, blaCTX-M9, and blaCTX-M1 genes, and two E. coli classified in the clonal complex ST10 (ST98) were detected in two of the locations sampled; these strains can severely impact public health. The clonal complex ST10, found in the E. coli isolates, possesses the potential to spread bacteria-resistant genes to humans and animals. The results of the use of BCWFs, however, argue for the filters’ potential impact within those contexts, as the BCWFs completely removed even antibiotic-resistant contaminants from the water.

High-Energy Electron Scattering in Thick Samples Evaluated by Bright-Field Transmission Electron Microscopy, Energy-Filtering Transmission Electron Microscopy, and Electron Tomography.

Energy-filtering transmission electron microscopy (TEM) and bright-field TEM can be used to extract local sample thickness $t$ and to generate two-dimensional sample thickness maps. Electron tomography can be used to accurately verify the local $t$. The relations of log-ratio of zero-loss filtered energy-filtering TEM beam intensity ($I_{{\rm ZLP}}$) and unfiltered beam intensity ($I_{\rm u}$) versus sample thickness $t$ were measured for five values of collection angle in a microscope equipped with an energy filter. Furthermore, log-ratio of the incident (primary) beam intensity ($I_{\rm p}$) and the transmitted beam $I_{{\rm tr}}$ versus $t$ in bright-field TEM was measured utilizing a camera before the energy filter. The measurements were performed on a multilayer sample containing eight materials and thickness $t$ up to 800 nm. Local thickness $t$ was verified by electron tomography. The following results are reported:•The maximum thickness $t_{{\rm max}}$ yielding a linear relation of log-ratio, $\ln ( {I_{\rm u}}/{I_{{\rm ZLP}}})$ and $\ln ( {I_{\rm p}}/{I_{{\rm tr}}} )$, versus $t$.•Inelastic mean free path ($\lambda _{{\rm in}}$) for five values of collection angle.•Total mean free path ($\lambda _{{\rm total}}$) of electrons excluded by an angle-limiting aperture.•$\lambda _{{\rm in}}$ and $\lambda _{{\rm total}}$ are evaluated for the eight materials with atomic number from $\approx$10 to 79.The results can be utilized as a guide for upper limit of $t$ evaluation in energy-filtering TEM and bright-field TEM and for optimizing electron tomography experiments.

5WBF: a low-cost and straightforward whole blood filtration method suitable for whole-genome sequencing of Plasmodium falciparum clinical isolates

BackgroundWhole-genome sequencing (WGS) is becoming increasingly helpful to assist malaria control programmes. A major drawback of this approach is the large amount of human DNA compared to parasite DNA extracted from unprocessed whole blood. As red blood cells (RBCs) have a diameter of about 7–8 µm and exhibit some deformability, it was hypothesized that cheap and commercially available 5 µm filters might retain leukocytes but much less of Plasmodium falciparum-infected RBCs. This study aimed to test the hypothesis that such a filtration method, named 5WBF (for 5 µm Whole Blood Filtration), may provide highly enriched parasite material suitable for P. falciparum WGS.MethodsWhole blood was collected from five patients experiencing a P. falciparum malaria episode (ring-stage parasitaemia range: 0.04–5.5%) and from mock samples obtained by mixing synchronized, ring-stage cultured P. falciparum 3D7 parasites with uninfected human whole blood (final parasitaemia range: 0.02–1.1%). These whole blood samples (50 to 400 µL) were diluted in RPMI 1640 medium or PBS 1× buffer and filtered with a syringe connected to a 5 µm commercial filter. DNA was extracted from 5WBF-treated and unfiltered counterpart blood samples using a commercial kit. The 5WBF method was evaluated on the ratios of parasite:human DNA assessed by qPCR and by sequencing depth and percentages of coverage from WGS data (Illumina NextSeq 500). As a comparison, the popular selective whole-genome amplification (sWGA) method, which does not rely on blood filtration, was applied to the unfiltered counterpart blood samples.ResultsAfter applying 5WBF, qPCR indicated an average of twofold loss in the amount of parasite template DNA (Pf ARN18S gene) and from 4096- to 65,536-fold loss of human template DNA (human β actin gene). WGS analyses revealed that > 95% of the parasite nuclear and organellar genomes were all covered at ≥ 10× depth for all samples tested. In sWGA counterparts, the organellar genomes were poorly covered and from 47.7 to 82.1% of the nuclear genome was covered at ≥ 10× depth depending on parasitaemia. Sequence reads were homogeneously distributed across gene sequences for 5WBF-treated samples (n = 5460 genes; mean coverage: 91×; median coverage: 93×; 5th percentile: 70×; 95th percentile: 103×), allowing the identification of gene copy number variations such as for gch1. This later analysis was not possible for sWGA-treated samples, as a much more heterogeneous distribution of reads across gene sequences was observed (mean coverage: 80×; median coverage: 51×; 5th percentile: 7×; 95th percentile: 245×).ConclusionsThe novel 5WBF leucodepletion method is simple to implement and based on commercially available, standardized 5 µm filters which cost from 1.0 to 1.7€ per unit depending on suppliers. 5WBF permits extensive genome-wide analysis of P. falciparum ring-stage isolates from minute amounts of whole blood even with parasitaemias as low as 0.02%.

Distribution of rare earth elements in groundwater resources from sedimentary rocks of Eastern Crete, Greece

ABSTRACT This study aimed to investigate the REEs’ presence in the rocks and groundwaters of three different aquifers in eastern Crete. The first developsin carbonate rocks, and is a typical unconfined karst aquifer. The second, developsin Miocene conglomerates and sandstones, and is confined by marly formations, whilethe third in the Pliocene conglomerates overlying the Phyllites Formation. Theyare all formed by minerals such as calcite, dolomite, aragonite, anhydride,halite and sylvite, display neutral to slightly alkaline pH and positive to slightlypositive redox values. The karst aquifer is of Ca-Mg-HCO3 water type, while near the coast Na+ and Cl− are also involved due to seawater intrusion. In the other two aquifers, complex hydrochemical types prevail suchas, Ca-Mg-Na-HCO3-Cl for the second or Na-Ca-Mg-Cl-HCO3 for the third one. ΣREEs concentrations range between 64 and 1,671 ppm for rocks, 45 and 120 pptfor 0.45 μm filtered, and 219 and 1,087 ppt for unfiltered groundwater. Thedifferences between filtered and unfiltered samples were attributed to the greatertendency of REEs to be adsorbed on surfaces such as Fe-Mn oxides andhydroxides, some organic substances or particles, colloids, clay minerals, andmicroorganisms, which were removed during filtration. Furthermore, an evidentnegative Ce anomaly in the filtered samples was attributed to the Ce oxidationand removal from the dissolved phase. The Japanese and European shales normalised REE diagrams of all groundwater samples show great similarities attributed to the presence of common major minerals such as calcite, dolomite and gypsum. The positive Eu anomalies were attributed to the dissolution of these common minerals from the aquifers’ bedrock. Finally, the increased concentrations in the unfiltered samples of the porous aquifers were associated with ion exchange processes, while the lower values in certain brackish samples were attributed to colloidal precipitation processes due to the increased salinity.

Occurrence and sources of lead in private wells, Sturbridge, Massachusetts

Lead (Pb) occurrence and sources and aqueous geochemistry were assessed in private wellhead and tap water at a targeted area of concern for possible exceedances and at a control area in the same geologic formation, and in wells at a nearby landfill in south-central Massachusetts (MA). Total Pb concentrations were below the U.S. Environmental Protection Agency (USEPA) Action Level of 15 μg/L in all samples, and about 6% of unfiltered samples contained Pb concentrations that exceeded 1.0 μg/L. Pb concentrations were higher under conditions that are acidic and oxic (pH ≤ 6.5 and dissolved oxygen [DO] ≥ 2 mg/L), in which minerals that could sequester lead or manganese typically are undersaturated, and adsorption by hydrous ferric oxide is limited. Under more neutral to alkaline conditions, the precipitation of Pb in solid solution series minerals such as (Ca,Pb)CO3 and (Ba,Pb)SO4−2, and adsorption by amorphous ferric hydroxides, could limit Pb solubility in the bedrock aquifer or in the plumbing. The low Pb concentrations and the absence of distinctive Pb and strontium (Sr) isotope ratio patterns in samples indicate that a nearby landfill is not likely a significant Pb source. Dissolved concentrations of Pb, copper (Cu), and zinc (Zn) in tap samples were significantly greater than those in wellhead samples, indicating that some Pb is derived from plumbing. Wellhead or tap samples with the highest Pb concentrations also had the greatest corrosivity potential based on the calcite saturation index and the PPGC (Potential to Promote Galvanic Corrosion) and supports the premise that Pb concentrations in tap samples were derived partly from corrosion of plumbing. Concentrations of other constituents, including arsenic (As), uranium (U), Sr, boron (B), and lithium (Li) were not statistically different between the tap and wellhead samples but, apart from Sr, all were statistically higher in the control area than in the target area. This variation in constituent concentrations suggests geochemical variation within the host Paxton Formation, possibly related to faulting and contact with the Ayer granite east of the control area.

New Insights Into the Non‐Conservative Behaviors of Nutrients Triggering Phytoplankton Blooms in the Changjiang (Yangtze) River Estuary

AbstractFour research cruises were carried out during March and July in 2015 and 2016 in the Changjiang (Yangtze) River Estuary and the adjacent shelf. Nutrient concentrations (regarded as static parameters) were measured in the surface and bottom waters collected at 86–99 stations over the course of these cruises. In addition, unfiltered seawater samples were incubated onboard for 48 hr to measure the potential change rates of nutrients (regarded as dynamic parameters). These parameters can help directly elucidate non‐conservative behaviors of nutrients in order to determine whether seawater serves as a source or a sink. Large nutrient sinks (with more negative variation rates) were consistently found at the surface during the two July cruises at the stations just along the outside edge of the turbidity maximum zone near the mouth of the river. Negative rates, although with much smaller magnitudes, were also found in most bottom water samples in July and at both the surface and bottom in March. The high net nutrient uptake rates at the surface in the summer triggered bloom events later at the seaward stations, showing that high net nutrient uptake is the cause and high chlorophyll‐a is the consequence of the bloom. Such information about biogeochemical cycling of nutrients and the mechanisms and development of bloom events occurring in large river estuarine and coastal areas could not have been obtained if these static and dynamic parameters had not been studied together.

Influence of point-of-use filters and stagnation on water quality at a preschool and under laboratory conditions

A local preschool installed NSF/ANSI 42 and 53 certified point-of-use (POU) filters in its classroom sinks and drinking fountains to protect children from the possibility of elevated lead (Pb) levels in drinking water. We examined the effects of these filters during flowing water and immediately following stagnation periods on Pb, chlorine, and bacterial concentrations in the field and the laboratory. Before and after typical school stagnation periods, we collected samples from filtered classroom sinks, a filtered drinking fountain and nearby unfiltered sinks for a year. No unfiltered samples exceeded Illinois State limits of 5 µg/L for Pb in pre-K through 5th grade schools. However, following stagnation periods as short as overnight (14.5 h), over half of post-stagnation filtered samples from classroom sinks exceeded 5 µg/L while post-stagnation unfiltered samples remained below 5 µg/L. Laboratory testing showed no significant increases in Pb with stagnation, suggesting that the preschool classrooms may have had Pb-bearing plumbing downstream of the filters which released Pb into the filtered drinking water. The filters effectively removed free chlorine (99% decrease) in both the preschool and laboratory. Installing the filters had the unintended consequence of significantly increasing the bacterial concentrations (as measured by qPCR) in the preschool's drinking water and in laboratory filter effluent. Legionella pneumophila, Pseudomonas aeruginosa, and Mycobacterium spp. were not detected in pre-stagnation unfiltered and post-stagnation filtered samples. These results suggest that the installation of POU filters be considered as one component of an overall strategy to decrease Pb concentrations in school drinking water that holistically considers the premise plumbing system. A 5-minute flush significantly decreased concentrations of Pb and bacteria in filtered sinks. Replacing Pb-bearing plumbing components downstream of a POU filter may also be needed to combat Pb levels in drinking water.

Microbiological Analysis of Drinking Water from Different Areas of Lahore

Access to safe drinking water and its regular monitoring is essential to ensure the health and safety of the public. This study aimed to analyze the microbiological quality of drinking water supplies (filtered and unfiltered) from various towns of Lahore, Pakistan. In total, 135 water samples, with and without filtration (n=90) and additional 45 bottled drinking water samples of different brands from the local market were collected from 9 towns of Lahore. To determine the microbiological quality, all samples were subjected to total plate count, total coliform, E. coli, Streptococci and Salmonella detection. According to the findings, the total plate count from various water supplies was significantly higher as compared to bottled drinking water samples. Drinking water from supplies with filtration and without filtration was found to be contaminated with total coliform (51%), E. coli (51%) and total coliform (84.5%), E. coli (84.5%), faecal Streptococci (15.5%), and Salmonella (11.1%) respectively. In total, 22 (49%) of the filtered and 7 (15.5%) of the unfiltered water samples were found to be microbiologically safe for drinking, whereas 41 (91.1%) bottled drinking water samples met the WHO criteria. To summarize, bottled drinking water is safer than both filtered and unfiltered drinking water. However, all bottled water should not be assumed to be safe for use. The microbial contamination in drinking water supplies, as well as bottled water samples, insinuates for strict monitoring of drinking water by regulatory authorities, and immediate action is required to avoid public health hazards.

Population-level interest and trends in meditation and yoga during lockdown imposed due to coronavirus disease 2019 pandemic In India

Introduction: Yoga and meditation have a potential to give mental peace and calm. The present coronavirus disease 2019 (COVID-19) has forced countries to impose lockdown due to its infectious nature, thus restricting people in their homes posing psychosocial impact which can be reduced through yoga. Google Trends (GT) is a proxy indicator for population-level interests, which is used instead of traditional survey methods during pandemic. The objective of this study was to monitor population-level interest and trends in yoga and meditation during lockdown imposed due to COVID-19 in India through GT. Material &amp; Methods: GT is an open-access, web-based tool which provides unfiltered sample of active search requests made to Google. Various keywords related to yoga and meditation were used to retrieve web-based search volume from January 30, 2020, to June 7, 2020, for India. These data were correlated with number of cases and deaths reported due to COVID-19 as an increase in cases and death might lead to stress among masses. Results: The search trends and daily number of confirmed cases were fairly correlated (r = 0.647, P = 0.000). The relative search volume for the search trends was also fairly correlated (r = 0.665, P = 0.000) with number of daily deaths due to COVID-19. States such as Uttarakhand and Goa had a higher share of search whereas Meghalaya and West Bengal searched the least. Conclusion: GT showed an increase in population-level interest in yoga and meditation during COVID-19 lockdown which is a positive indicator for population. This indicates the need for continuity of trend so as to make it a routine habit even after the situation becomes normal.

Quantifying 210Po/210Pb Disequilibrium in Seawater: A Comparison of Two Precipitation Methods With Differing Results

The disequilibrium between lead-210 (210Pb) and polonium-210 (210Po) is increasingly used in oceanography to quantify particulate organic carbon (POC) export from the upper ocean. This proxy is based on the deficits of 210Po typically observed in the upper water column due to the preferential removal of 210Po relative to 210Pb by sinking particles. Yet, a number of studies have reported unexpected large 210Po deficits in the deep ocean indicating scavenging of 210Po despite its radioactive mean life of ∼ 200 days. Two precipitation methods, Fe(OH)3 and Co-APDC, are typically used to concentrate Pb and Po from seawater samples, and deep 210Po deficits raise the question whether this feature is biogeochemically consistent or there is a methodological issue. Here, we present a compilation of 210Pb and 210Po studies that suggests that 210Po deficits at depths &amp;gt;300 m are more often observed in studies where Fe(OH)3 is used to precipitate Pb and Po from seawater, than in those using Co-APDC (in 68 versus 33% of the profiles analyzed for each method, respectively). In order to test whether 210Po/210Pb disequilibrium can be partly related to a methodological artifact, we directly compared the total activities of 210Pb and 210Po in four duplicate ocean depth-profiles determined by using Fe(OH)3 and Co-APDC on unfiltered seawater samples. While both methods produced the same 210Pb activities, results from the Co-APDC method showed equilibrium between 210Pb and 210Po below 100 m, whereas the Fe(OH)3 method resulted in activities of 210Po significantly lower than 210Pb throughout the entire water column. These results show that 210Po deficits in deep waters, but also in the upper ocean, may be greater when calculated using a commonly used Fe(OH)3 protocol. This finding has potential implications for the use of the 210Po/210Pb pair as a tracer of particle export in the oceans because 210Po (and thus POC) fluxes calculated using Fe(OH)3 on unfiltered seawater samples may be overestimated. Recommendations for future research are provided based on the possible reasons for the discrepancy in 210Po activities between both analytical methods.

Characterizing bioavailable phosphorus concentrations in an agricultural stream during hydrologic and streambed disturbances.

In freshwater ecosystems, phosphorus (P) is often considered a growth-limiting nutrient. The use of fertilizers on agricultural fields has led to runoff-driven increases in P availability in streams, and the subsequent eutrophication of downstream ecosystems. Isolated storms and periodic streambed dredging are examples of two common disturbances that contribute dissolved and particulate P to agricultural streams, which can be quantified as soluble reactive P (SRP) using the molybdate-blue method on filtered water samples, or total P (TP) measured using digestions on unfiltered water reflecting all forms of P. While SRP is often considered an approximation of bioavailable P (BAP), research has shown that this is not always the case. Current methods used to estimate BAP do not account for the role of biology (e.g., NaOH extractions) or require specialized platforms (e.g., algal bioassays). Here, in addition to routine analysis of SRP and TP, we used a novel yeast-based bioassay with unfiltered sample water to estimate BAP concentrations during two storms (top 80% and > 95% flow quantiles), and downstream of a reach where management-associated dredging disturbed the streambed. We found that the BAP concentrations were often greater than SRP, suggesting that SRP is not fully representative of P bioavailability. The SRP concentrations were similarly elevated during the two storms, but remained consistently low during streambed disturbance. In contrast, turbidity and TP were elevated during all events. The BAP concentrations were significantly related to turbidity during all disturbance events, but with TP only during storms. The novel yeast assay suggests that BAP export can exceed SRP, particularly when streams are not in equilibrium, such as the rising limb of storms or during active dredging.

Geochemistry of natural acid rock drainage in the Judith Mountains, Montana, part 2: Seasonal and spatial trends in Chicago Gulch

Three streams radially draining Red Mountain, a prominent peak in the Judith Mountains of central Montana, are naturally acidic in their headwaters and experience a rise in pH as they transition from hydrothermally altered quartz monzonite to sedimentary bedrock in their lower reaches. A previous study (Williams et al., 2015) examined the geochemistry of two of these streams, Armells Creek and Collar Gulch, using detailed synoptic sampling with continuous tracer-injection. Here we present results of two synoptic sampling events in the third stream, Chicago Gulch. Data are compared between the three watersheds, and estimates of solute flux (load divided by watershed area) are presented.Filtered and unfiltered metal concentrations and loads are quantified with distance downstream in Chicago Gulch under low-flow (August) and high-flow (May) conditions. Headwater streams in the watershed have pH < 4 and extensive deposits of ferricrete and Fe-bog deposits. Weakly acidic springs (pH > 4) contain >10 mg/L of Fe2+ which quickly oxidizes and precipitates as hydrous ferric oxide (HFO), releasing protons that lower the pH of the stream. Geochemical modeling suggests the actively forming HFO is a mix of schwertmannite and ferrihydrite, both of which are slowly converting to goethite which cements the ferricrete deposits. White, hydrous aluminum oxide (HAO) flocs form where stream pH transitions from <5 to >5, and a comparison of filtered and unfiltered samples indicates strong partitioning of Cu and Pb into the suspended particles. Dissolved loads of Zn, Cd, Mn, and Tl (thallium) diminish slightly in the lower reaches of Chicago Gulch where pH rises above 7.All water samples collected in the upper reaches of Chicago Gulch exceed the US-EPA water quality standards for protection of aquatic life for Pb, Cd, Zn, and Cu, and human health standards for Tl. Lead concentrations are especially high in the headwaters of Chicago Gulch, indicating the possible presence of an unmined Pb-sulfide deposit. Estimates of the load of dissolved sulfate at baseflow conditions in each stream on Red Mountain, normalized to their respective surface areas of hydrothermally altered bedrock, are remarkably similar, and indicate a steady state pyrite oxidation rate of 11.9 mol FeS2/h/km2. Prediction of pre-modern pH using the methods of Nimick et al. (2009) indicates that the current pH regimes of all three streams draining Red Mountain are broadly similar to conditions when ancient ferricretes were deposited. Because the Judith Mountains were never glaciated in the Pleistocene, it is possible that similar hydro-geochemical conditions have existed in the area for 10's to 100's of thousands of years.

Phosphorus Transport in a Lowland Stream Derived from a Tracer Test with 32P

Small streams in urbanized rural areas receive loads of P from various, often episodic, sources. This paper addresses, through a tracer test with 32P, retention and transport of a pulse input of phosphorus in a 2.6 km long stretch of a channelized second-order lowland stream. Tritiated water was introduced alongside the 32P-labelled ortophosphate in order to isolate the influence of the hydrodynamic factors on P behavior. Tracer concentrations in unfiltered water samples were measured by liquid scintillation counting. Four in-stream and five hyporheic breakthrough curves were collected at four points along the stream, two of which encompass a beaver dam impoundment. The overall retention efficiency of 32P along the studied reach was 46%. The transient storage transport model OTIS-P provided reasonable fits for in-stream breakthrough curves (BTCs) but failed at reproducing the hyporheic BTCs. The overall small effect of transient storage on solute transport was higher in the stretch with a more pronounced surface storage. Transient storage and phosphorus retention were not enhanced in the beaver dam impoundment.

The synergistic fouling of ceramic membranes by particles and natural organic matter fractions using different surface waters in South Africa

This study demonstrates the fundamental differences in fouling development and mechanisms of unfiltered and 0.45 µm pre-filtered water samples on ceramic membranes. Robust characterization of the feed waters was conducted using gravimetric analysis, optical methods and modeling techniques. UV254 removal and suspended solids (SS) for the unfiltered samples presented a strong correlation (R2 = 0.87). Further, SS exhibited strong correlations with fluorescent fractions (R2 = 0.82; 0.81 and 0.74 for C1; C2 and C3, respectively). This observation confirmed the significance of inorganic particles in the development of a combined fouling layer with fluorescent organic components. The fouling development rate for water sampled from Plattenburg Bay (PL) was higher than the rest of the 0.45 µm pre-filtered samples. This was attributed to the low conductivity (175 µS.m-1) of the water sample, translating to a low ionic strength environment. Samples collected from Hermanus River (HL) and Lepelle River (OL) had similar SS quantity (87.6 mg/L and 88.4 mg/L, respectively), and modified fouling index (MFI) values for raw samples were 6625 and 8060 s/L2 , respectively, despite a very large difference in the content of organic matter (22.67 mg/L.C and 9.81 mg/L.C). This could be due to organic matter attaching onto the surface of particles and reducing the adsorption of NOM within membrane pores and/or onto the membrane active layer. This study demonstrated the extent of in situ background electrolytes, foulant concentration, foulant-foulant interactions, foulant-membrane interaction and physicochemical properties of feed stream on fouling development and mechanisms.

The degradation of acetaldehyde in estuary waters in Southern California, USA.

Acetaldehyde plays an important role in oxidative cycles in the troposphere. Estimates of its air-water flux are important in global models. Biological degradation is believed to be the dominant loss process in water, but there have been few measurements, none in estuaries. Acetaldehyde degradation rates were measured in surface waters at the inflow to the Upper Newport Back Bay estuary in Orange County, Southern California, USA, over a 6-month period including the rainy winter season. Deuterated acetaldehyde was added to filtered and unfiltered water samples incubated in glass syringes, and its loss analyzed by purge and trap gas chromatography mass spectrometry. Filtered samples showed no significant degradation, suggesting that particle-mediated degradation is the dominant removal process. Correlation between measured degradation rate constants in unfiltered incubations and bacteria counts suggests the loss is due to microorganisms. Degradation in unfiltered samples followed first-order kinetics, with rate constants ranging from 0.0006 to 0.025 min-1 (k; average 0.0043 ± 0.006 min-1). Turnover (1/k) ranged from 40 to 1667 min, consistent with prior studies in coastal waters. Acetaldehyde concentrations in the estuary are estimated to range from 30 to ~500 nM (average ~250 nM). Results suggest the estuary is a source of acetaldehyde to the atmosphere.

Viability of SARS-CoV-2 in river water and wastewater at different temperatures and solids content

COVID-19 patients can excrete viable SARS-CoV-2 virus via urine and faeces, which has raised concerns over the possibility of COVID-19 transmission via aerosolized contaminated water or via the faecal-oral route. These concerns are especially exacerbated in many low- and middle-income countries, where untreated sewage is frequently discharged to surface waters. SARS-CoV-2 RNA has been detected in river water (RW) and raw wastewater (WW) samples. However, little is known about SARS-CoV-2 viability in these environmental matrices. Determining the persistence of SARS-CoV-2 in water under different environmental conditions is of great importance for basic assumptions in quantitative microbial risk assessment (QMRA). In this study, the persistence of SARS-CoV-2 was assessed using plaque assays following spiking of RW and WW samples with infectious SARS-CoV-2 that was previously isolated from a COVID-19 patient. These assays were carried out on autoclaved RW and WW samples, filtered (0.22 µm) and unfiltered, at 4 °C and 24 °C. Linear and nonlinear regression models were adjusted to the data. The Weibull regression model achieved the lowest root mean square error (RMSE) and was hence chosen to estimate T90 and T99 (time required for 1 log and 2 log reductions, respectively). SARS-CoV-2 remained viable longer in filtered compared with unfiltered samples. RW and WW showed T90 values of 1.9 and 1.2 day and T99 values of 6.4 and 4.0 days, respectively. When samples were filtered through 0.22 µm pore size membranes, T90 values increased to 3.3 and 1.5 days, and T99 increased to 8.5 and 4.5 days, for RW and WW samples, respectively. Remarkable increases in SARS-CoV-2 persistence were observed in assays at 4 °C, which showed T90 values of 7.7 and 5.5 days, and T99 values of 18.7 and 17.5 days for RW and WW, respectively. These results highlight the variability of SARS-CoV-2 persistence in water and wastewater matrices and can be highly relevant to efforts aimed at quantifying water-related risks, which could be valuable for understanding and controlling the pandemic.

Effects of preservation strategies on environmental DNA detection and quantification using ddPCR

AbstractMolecular‐based monitoring relying on environmental DNA (eDNA) detection became routinely used around the world in the last few years, especially in aquatic environments. The large potential and increasing applications of this technique calls for technical improvements to optimize the reliability of these surveys. An important technical aspect in the eDNA workflow is the appropriate preservation of samples taken in the field, as it can significantly affect eDNA recovery and ultimately false negative rates. In this study, we explored the efficiency of five different preservation strategies by using a controlled mesocosm experiment in which we included three fish communities of different composition. Specifically, we compared eDNA recovery in DNA extractions (a) performed immediately following collection, or after eight months storage from (b) frozen filters, (c) unfiltered water samples stored at −20°C, and filters preserved at room temperature with (d) Longmire and (e) Sarkosyl buffer. Effects of different preservation strategies were quantified using ddPCR measurements of three fish species (Neogobius melanostomus, Rutilus rutilus, and Lota lota) and total fish DNA content using group‐specific primers for Teleostei. Samples extracted immediately following collection without any further preservation yielded significantly less DNA compared to the other approaches. Overall, Longmire's buffer facilitated the best eDNA recovery across all fish species although approaches such as filter freezing or the use of Sarkosyl buffer yielded similar recovery results. Relative measurement variability, an important indicator for reliable eDNA quantification, was lowest when using Longmire's and Sarkosyl buffers and generally decreased when increasing eDNA quantity. Overall, our results clearly highlight the significant impact of sample preservation and how this can substantially affect the performance and reliability of eDNA‐based approaches.