Inter-event and intra-event dynamics of microplastic emissions in an urban river during rainfall episodes.

Urban rivers represent the major conduits for land-sourced microplastics in the global oceans, yet the real-time dynamics of their emissions in rivers during rainfall (and runoff) events are poorly understood. Herein, we report the results of high-frequency sampling of microplastic particles (MPs) and fibers (MPFs) in the surface water of an urban river in Japan over the course of three rainfall events (i.e., light, moderate, and heavy rainfalls). The event mean concentrations (EMCs) of MPs amounted to 35,000 items/m3, 929,000 items/m3, and 331,000 items/m3; and the corresponding total loads were 0.5 kg, 19.8 kg, and 35.0 kg for light, moderate and heavy rainfalls, respectively. The inter-event total loads of MPs correlate well with the total rainfall, while the concentrations were linked with the number of antecedent dry days. The dynamic trends show that <2000 µm MPs displayed first flush effects during light to moderate rainfall events (>50% mass discharged with the initial 20-40% of flow). Small-sized MPs (10-40 µm) mobilized rapidly at lower rainfall intensities, whereas MPs over 2000 µm discharged immediately after the peak rainfall intensity. Moreover, <70 µm MPs depicted a surge following heavy rainfall events due to turbulent flow conditions reverting the deposited MPs into suspension. Overall, the three events increased the loads by 4-110 folds, and EMCs by 10-350 folds compared to the concentrations during dry weather while portraying a significant impact on 300-1000 µm MPs. The dynamics of MPs were correlated with those of suspended solids in river water, and the characteristics were comparable to the same of road dust sampled in Japan. Although the dynamic trends between MPs and MPFs in river water were comparable, MPFs were relatively less impacted by rain, likely due to the intervention of separate sewer systems in the study area.

Fish fauna and environmental factors in river estuaries of small and medium-sized rivers on islands significantly influenced by warm currents.

River estuaries are influenced by terrestrial and marine areas, and have a unique environment that is constantly fluctuating. They are also important habitats for biodiversity conservation. Tanegashima Island is significantly influenced by the Kuroshio Current. Although nearby Yakushima Island has been recognized as a World Natural Heritage site and information on many species has been collected, there is little information on species inhabiting the river estuaries of Tanegashima Island. In this study, the river estuarine ichthyofauna of 26 small and medium-sized rivers on Tanegashima Island was surveyed and a total of 2758 individuals of 29 species and one genus belonging to 15 families were collected. The fish fauna of the river estuaries of Tanegashima Island were classified into three groups, namely the river estuaries where coastal terraces are underdeveloped and drowned valleys are formed, the river group where the riverbed gradient at the mouth is high, and other river groups. Environmental factors selected as being important for ordination of fish fauna were the altitude of the headstreams at the watershed scale, the gradient of the river estuarine area, and the presence or absence of rapids in the estuary. The importance of the geohistorical factor of drowned valley formation, in addition to habitat and watershed scale environmental factors, as a factor on river estuarine fish fauna is an important finding for future conservation of local biota diversity.

Distribution of microplastics in rainfall and their control by a permeable pavement in low-impact development facility.

Microplastics (MPs) released from plastic products in daily life are present in the air and could be transported to freshwater environments along with rain. Recently, low-impact development (LID) facilities, such as permeable pavements, have been used to treat non-point source pollutants, including rainfall runoff. While runoff is treated by LID facilities, the periodic monitoring of MPs in rainfall and the efficiency of removal of MPs through LID facilities have rarely been investigated. Therefore, this case study focused on monitoring MPs in rainwater runoff and permeate from a permeable pavement in Busan, South Korea, thus evaluating the removal efficiency of MPs by a LID system. The initial rainfall runoff and permeate through the LID system were sampled, and the amounts, types, sizes, and shapes of MPs in the samples were analyzed using micro-Fourier Transform Infrared (FTIR) spectroscopy. The results showed that the distribution of MPs in the initial rainfall was affected by population in tested area. Polyethylene was the most common type of MPs in all the samples. Polyamide was only found in the LID samples because of the pollution caused by water flows and pavement materials. Fragment type MPs was most commonly observed and consisted of relatively small-sized (under 100 µm) particles. LID facilities were able to capture approximately 98% of MPs in the rainfall through a filtration process in the permeable pavement.

Onset of Antarctic Circumpolar Current 30 million years ago as Tasmanian Gateway aligned with westerlies.

Earth's mightiest ocean current, the Antarctic Circumpolar Current (ACC), regulates the exchange of heat and carbon between the ocean and the atmosphere, and influences vertical ocean structure, deep-water production and the global distribution of nutrients and chemical tracers. The eastward-flowing ACC occupies a unique circumglobal pathway in the Southern Ocean that was enabled by the tectonic opening of key oceanic gateways during the break-up of Gondwana (for example, by the opening of the Tasmanian Gateway, which connects the Indian and Pacific oceans). Although the ACC is a key component of Earth's present and past climate system, the timing of the appearance of diagnostic features of the ACC (for example, low zonal gradients in water-mass tracer fields) is poorly known and represents a fundamental gap in our understanding of Earth history. Here we show, using geophysically determined positions of continent-ocean boundaries, that the deep Tasmanian Gateway opened 33.5 ± 1.5 million years ago (the errors indicate uncertainty in the boundary positions). Following this opening, sediments from Indian and Pacific cores recorded Pacific-type neodymium isotope ratios, revealing deep westward flow equivalent to the present-day Antarctic Slope Current. We observe onset of the ACC at around 30 million years ago, when Southern Ocean neodymium isotopes record a permanent shift to modern Indian-Atlantic ratios. Our reconstructions of ocean circulation show that massive reorganization and homogenization of Southern Ocean water masses coincided with migration of the northern margin of the Tasmanian Gateway into the mid-latitude westerly wind band, which we reconstruct at 64° S, near to the northern margin. Onset of the ACC about 30 million years ago coincided with major changes in global ocean circulation and probably contributed to the lower atmospheric carbon dioxide levels that appear after this time.

Temporal dynamics of migration-linked genetic variation are driven by streamflows and riverscape permeability.

Landscape permeability is often explored spatially, but may also vary temporally. Landscape permeability, including partial barriers, influences migratory animals that move across the landscape. Partial barriers are common in rivers where barrier passage varies with streamflow. We explore the influence of partial barriers on the spatial and temporal distribution of migration-linked genotypes of Oncorhynchus mykiss, a salmonid fish with co-occurring resident and migratory forms, in tributaries to the South Fork Eel River, California, USA, Elder and Fox Creeks. We genotyped >4,000 individuals using RAD-capture and classified individuals as resident, heterozygous or migratory genotypes using life history-associated loci. Across four years of study (2014-2017), the permeability of partial barriers varied across dry and wet years. In Elder Creek, the largest waterfall was passable for adults migrating up-river 4-39 days each year. In this stream, the overall spatial pattern, with fewer migratory genotypes above the waterfall, remained true across dry and wet years (67%-76% of migratory alleles were downstream of the waterfall). We also observed a strong relationship between distance upstream and proportion of migratory alleles. In Fox Creek, the primary barrier is at the mouth, and we found that the migratory allele frequency varied with the annual timing of high flow events. In years when rain events occurred during the peak breeding season, migratory allele frequency was high (60%-68%), but otherwise it was low (30% in two years). We highlight that partial barriers and landscape permeability can be temporally dynamic, and this effect can be observed through changing genotype frequencies in migratory animals.

Investigation of water and salt flux performances of polyamide coated tubular electrospun nanofiber membrane under pressure.

In this study, a novel osmotic membrane was developed by polyamide (PA) coating on the tubular electrospun nanofiber (TuEN) support membrane. Water and reverse salt flux properties of the obtained membrane were investigated by applying pressure in addition to the osmotic forces. Surface characterization of the membrane was carried out by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) analyses and flux performance tests were performed in both cross flow and submerged membrane setups. Applying pressure from the feed to the concentrate side had significant effects on the water and salt fluxes. Higher pressure differences between the feed and concentrate sides resulted in unexpected high water fluxes up to 500 Lm-2h-1 (LMH). Besides, the pressure helps to transfer the salt content of feed water into the concentrate side, differently from the osmotic process preventing the salinity build-up at the feed side. PA coated TuEN membrane operated under pressure will exhibit a favorable solution in water/wastewater treatment applications, especially for membrane bioreactors (MBR) in terms of preventing salt accumulation in the bioreactor, decreasing the membrane fouling, increasing the volume of product water, and enabling the concentrate management.

Spreading of River Water Guides Migratory Behavior of Homing Chum Salmon Oncorhynchus keta in Otsuchi Bay, a Narrow Inlet with Multiple River Flows.

The Sanriku-ria coast of Japan, a homing area for chum salmon, Oncorhynchus keta, is characterized by a large number of small closed bays into which one or multiple short rivers flow. The present behavioral investigation of chum salmon in this region was designed to gain deeper insight into the migration of chum salmon to their natal rivers. Eighty-three fish caught at the middle part of Otsuchi Bay were tracked using an acoustic transmitter in the narrow inlet into which flow three rivers: the Otsuchi, Koduchi, and Unosumai. The majority of 18 fish that entered the Unosumai River, which flows into the southwest side of the bay, directly approached the river along the southern coast. More than half of fish that entered the Otsuchi and Koduchi Rivers, which flow into the northwest side, also migrated into the inner bay via the southerly route, and then entered these rivers frequently after passing the mouth of the Unosumai River. In the inner bay, the salinity of sea surface water suggested that water from the three rivers circulates in a counterclockwise direction at a depth of less than 1.0 m, flowing eastwardly along the southern coast. The observed migratory paths of homing salmon in Otsuchi Bay thus correspond well with the counterflow of surface river water in the bay. The present results suggest that homing migration of salmon in the Sanriku narrow inlet is guided by natal river flows.

Head width influences flow sensing by the lateral line canal system in fishes.

The architecture of the cephalic lateral line canal system, with distinct lines for the supraorbital, infraorbital and mandibular canals, is highly conserved among fish species. Because these canals lie on a cranial platform, the sensory input they receive is expected to change based on how flow interacts with the head and how the canal pores are spatially distributed. In this study, we explored how head width, a trait that can vary greatly between species and across ontogeny, affects flow sensing. We inserted pressure sensors into physical fish head models of varying widths (narrow, intermediate and wide) and placed these models in steady and vortical flows. We measured sensory performance in terms of detecting flow parameters (flow speed, vortex shedding frequency and cylinder diameter), sensitivity (change in pressure gradient as a function of flow speed) and signal-to-noise ratio (SNR; strength of vortex shedding frequency with respect to background). Our results show that in all model heads the amount of hydrodynamic information was maximized at the anterior region regardless of what metric we used to evaluate the sensory performance. In addition, we discovered that all model heads had the highest SNR for vortices at the intermediate flow speeds but that each head width passively optimized the SNR for different sized vortices, which may have implications for refuge and prey seeking. Our results provide insight into the sensory ecology of fishes and have implications for the design of autonomous underwater vehicles.

Conserved spatio-temporal patterns of suction-feeding flows across aquatic vertebrates: a comparative flow visualization study.

Suction feeding is a widespread prey capture strategy among aquatic vertebrates. It is almost omnipresent across fishes, and has repeatedly evolved in other aquatic vertebrates. By rapidly expanding the mouth cavity, suction feeders generate a fluid flow outside of their mouth, drawing prey inside. Fish and other suction-feeding organisms display remarkable trophic diversity, echoed in the diversity of their skull and mouth morphologies. Yet, it is unclear how variable suction flows are across species, and whether variation in suction flows supports trophic diversity. Using a high-speed flow visualization technique, we characterized the spatio-temporal patterns in the flow fields produced during feeding in 14 species of aquatic suction feeders. We found that suction-feeding hydrodynamics are highly conserved across species. Suction flows affected only a limited volume of ∼1 gape diameter away from the mouth, and peaked around the timing of maximal mouth opening. The magnitude of flow speed increased with increasing mouth diameter and, to a lesser extent, with decreasing time to peak gape opening. Other morphological, kinematic and behavioral variables played a minor role in shaping suction-feeding dynamics. We conclude that the trophic diversity within fishes, and likely other aquatic vertebrates, is not supported by a diversity of mechanisms that modify the characteristics of suction flow. Rather, we suggest that suction feeding supports such trophic diversity owing to the general lack of strong trade-offs with other mechanisms that contribute to prey capture.

Effect of Water Quality and Temperature on the Efficiency of Two Kinds of Hydrophilic Polymers in Soil.

In this study, evaluation of two-superabsorbent effects, Super-AB-A-300 and Super-AB-A-200 in a sandy soil on the water retention capability and saturated hydraulic conductivity (Ks) at different water quality and soil temperature were done. The Super-AB-A-200 was less effective in water uptake than Super-AB-A-300. The efficiency of these polymers in water retention was negatively influenced by the water quality and temperature. The efficiency of these polymer treatments in water uptake reduced significantly (P < 0.05) with increasing soil temperature. In the control soil, the Ks stayed nearly constant with increasing soil temperature. As compared to the untreated control, the treated soil demonstrated a significant (P < 0.05) linear increase of Ks with increasing soil temperature. In the control soil, the water holding properties curve did not change with increasing soil temperature.

Intraspecific morphological and reproductive trait variation in mouth almighty Glossamia aprion (Apogonidae) across different flow environments.

Intraspecific variability, although comparably less studied than interspecific variation, is an important tool in understanding population responses to environmental gradients. This study investigated intraspecific trait variation across three contrasting aquatic flow habitat types (intermittent creek, billabong and river) in a common mouth-brooding freshwater fish in northern Australia, the mouth almighty Glossamia aprion. Samples of G. aprion were collected at various sites, within the Daly River catchment. It was predicted that a number of morphological and reproductive traits would vary among individuals across the contrasting habitats. Five out of the nine morphological and reproductive traits studied significantly varied across flow habitat types. Significant intraspecific variation in functional traits related to foraging and reproduction, such as relative eye size, eye vertical position and relative maxillary length in males suggest that the inherent characteristics of each flow habitat type could be exerting selective pressure on the morphology of G. aprion. Interestingly, traits related to swimming performance (body lateral shape) and manoeuvrability (pectoral fin ventral position) differed between flow habitat types but showed inconsistent responses to predictions. Whilst this study was temporally and spatially limited, it highlights that intraspecific variability in morphological traits can occur among flow habitat types over relatively small spatial scales.

Combined effects of polyacrylamide and nanomagnetite amendment on soil and water quality, Khorasan Razavi, Iran.

Nanotechnology is increasingly being used to remediate polluted soil and water. However, few studies are available assessing the potential of nanoparticles to bind surface particles, decrease erosion, and minimize the loading of water pollutants from agricultural surface discharge. To investigate this potential, we treated in situ field plots with two practical surface application levels of anionic polyacrylamide (PAM only) with and without nanomagnetite (PAM-NM), examined soil physical properties, and evaluated the impact of this amendment on contaminant sorption and soil erosion control. Polyacrylamide and PAM-NM treatments resulted in 32.2 and 151.9 fold reductions in Mn2+, 1.8 and 2.7 fold for PO43--P, and 2.3 and 1.6 fold for NH4+-N, respectively, compared to the control. Thus, we found that the combination of PAM and NM, had an important inhibitory effect on NH4+-N and PO43--P transport from soil-pollutants which can contribute substantially to the eutrophication of surface water bodies. Additionally, since the treatment, especially at a high concentration of NM, was effective at reducing Mn2+concentrations in the runoff water, the combination of PAM and NM may be important for mitigating potential risks associated with Mn2+ toxicity. Average sediment contents in the runoff monitored during the rainfall simulation were reduced by 3.6 and 4.2 fold for the low and high concentration PAM-NM treatments when compared to a control. This treatment was only slightly less effective than the PAM-only applications (4.9 and 5.9 fold, respectively). We report similar findings for turbidity of the runoff (2.6-3.3 fold for PAM only and 1.8-2.3 fold for PAM-NM) which was caused by the effects of both PAM and NM on the binding of surface particles corresponding to an increase in aggregate size and stability. Findings from this field-based study show that PAM-modified NM adsorbents can be used to both inhibit erosion and control contaminant transport.

The influence of a green roof drainage layer on retention capacity and leakage quality.

The aim of the research was to determine the influence of the substrate and different drainage materials on retention capacity and runoff water quality from three green roof containers. Phosphates were chosen as the water quality indicator based on their potential adverse impact on water quality in urban rainwater collectors. The field experiment was conducted at the Warsaw University of Life Sciences Water Center meteorological station in years 2013-2015. In terms of precipitation, the monitoring period covered a wet (+147.1 mm), average (+42.7 mm) and dry (- 66.3 mm) year. Leakage from the containers was recorded when the substrate moisture exceeded 20% and precipitation exceeded 3.5 mm/d for washed gravel, or 5.0 mm/d for a polypropylene mat and expanded clay. Phosphates were observed in leachates from all containers, with higher values observed in the second year of monitoring. As the result of this study, it can be concluded that the polypropylene mat and aggregates create different conditions for the formation of the leachate, in both volumes and its chemistry. The drainage layer made from a polypropylene mat is the most effective in terms of rainwater retention capacity and the resulting leachate quality.

The effect of land use in the catchment and meteorological conditions on the riverine transport of dissolved organic carbon into the Puck Lagoon (southern Baltic).

Dissolved organic carbon (DOC) concentration and fluxes from four rivers draining the catchment of the Puck Lagoon in southern Baltic are presented. Water samples from rivers and coastal zone close to the rivers' mouth were collected from April 2015 to March 2017. DOC was measured using high temperature catalytic oxidation with an NDIR detection. DOC concentration in rivers as well as area specific load discharged to the lagoon reflected variations of land use along their course. Area specific load of DOC discharged by rivers with high proportion of forests, meadows, and pastures in the catchment was significantly higher as compared to rivers with catchment dominated by arable land. However, the main controlling factor of the total discharged loads of DOC was the water flow. The highest loads were observed during the downpour. That was due to the larger volumes of water transported with rivers and the higher concentration of DOC resulting from increased leaching from the catchment area. The obtained results are especially important in the light of climate change in the southern Baltic region. According to the forecasts, we can expect increased precipitation and flooding and consequently increased leaching from the catchment and transport of DOC to the sea via rivers.

Microfluidic accumulation assay probes attachment of biofilm forming diatom cells.

Testing of fouling release (FR) technologies is of great relevance for discovery of the next generation of protective marine coatings. In this paper, an accumulation assay to test diatom interaction under laminar flow with the model organism Navicula perminuta is introduced. Using time lapse microscopy with large area sampling allows determination of the accumulation kinetics of the diatom on three model surfaces with different surface properties at different wall shear stresses. The hydrodynamic conditions within the flow cell are described and a suitable shear stress range to perform accumulation experiments is identified at which statistically significant discrimination of surfaces is possible. The observed trends compare well to published adhesion preferences of N. perminuta. Also, previously determined trends of critical wall shear stresses required for cell removal from the same set of functionalized interfaces shows consistent trends. Initial attachment mediated by extracellular polymeric substances (EPS) present outside the diatoms leads to the conclusion that the FR potential of the tested coating candidates can be deducted from dynamic accumulation experiments under well-defined hydrodynamic conditions. As well as testing new coating candidates for their FR properties, monitoring of the adhesion process under flow provides additional information on the mechanism and geometry of attachment and the population kinetics.

Elucidation of the tidal influence on bacterial populations in a monsoon influenced estuary through simultaneous observations.

The influence of tides on bacterial populations in a monsoon influenced tropical estuary was assessed through fine resolution sampling (1 to 3 h) during spring and neap tides from mouth to the freshwater end at four stations during pre-monsoon, monsoon and post-monsoon seasons. Higher abundance of total bacterial count (TBC) in surface water near the river mouth, compared to the upstream, during pre-monsoon was followed by an opposite scenario during the monsoon When seasonally compared, it was during the post-monsoon season when TBC in surface water was highest, with simultaneous decrease in their count in the river sediment. The total viable bacterial count (TVC) was influenced by the depth-wise stratification of salinity, which varied with tidal fluctuation, usually high and low during the neap and spring tides respectively. The abundance of both the autochthonous Vibrio spp. and allochthonous coliform bacteria was influenced by the concentrations of dissolved nutrients and suspended particulate matter (SPM). It is concluded that depending on the interplay of riverine discharge and tidal amplitude, sediment re-suspension mediated increase in SPM significantly regulates bacteria populations in the estuarine water, urging the need of systematic regular monitoring for better prediction of related hazards, including those associated with the rise in pathogenic Vibrio spp. in the changing climatic scenarios.

Structure and flow calculation of cake layer on microfiltration membranes.

Submerged membrane bioreactors (SMBR) are widely used in wastewater treatment. The permeability of a membrane declines rapidly because of the formation of a cake layer on the membrane surface. In this paper, a multiple staining protocol was conducted to probe the four major foulants in the cake layer formed on a filtration membrane. Fluorescent images of the foulants were obtained using a confocal laser scanning microscope (CLSM). The three dimensional structure of the cake layer was reconstructed, and the internal flow was calculated using computational fluid dynamics (CFD). Simulation results agreed well with the experimental data on the permeability of the cake layer during filtration and showed better accuracy than the calculation by Kozeny-Carman method. ß-d-Glucopyranose polysaccharides and proteins are the two main foulants with relatively large volume fractions, while α-d-glucopyranose polysaccharides and nucleic acids have relatively large specific surface areas. The fast growth of ß-d-glucopyranose polysaccharides in the volume fraction is mainly responsible for the increase in cake volume fraction and the decrease in permeability. The specific area, or the aggregation/dispersion of foulants, is less important to its permeability compared to its volume fraction.

How does tidal flow affect pattern formation in mussel beds?

In the Wadden Sea, mussel beds self-organise into spatial patterns consisting of bands parallel to the shore. A leading explanation for this phenomenon is that mussel aggregation reduces losses from dislodgement and predation, because of the adherence of mussels to one another. Previous mathematical modelling has shown that this can lead to spatial patterning when it is coupled to the advection from the open sea of algae-the main food source for mussels in the Wadden Sea. A complicating factor in this process is that the advection of algae will actually oscillate with the tidal flow. This has been excluded from previous modelling studies, and the present paper concerns the implications of this oscillation for pattern formation. The authors initially consider piecewise constant ("square-tooth") oscillations in advection, which enables analytical investigation of the conditions for pattern formation. They then build on this to study the more realistic case of sinusoidal oscillations. Their analysis shows that future research on the details of pattern formation in mussel beds will require an in-depth understanding of how the tides affect long-range inhibition among mussels.

Impact of the surface roughness of AISI 316L stainless steel on biofilm adhesion in a seawater-cooled tubular heat exchanger-condenser.

The present study evaluated biofilm growth in AISI 316L stainless steel tubes for seawater-cooled exchanger-condensers that had four different arithmetic mean surface roughness values ranging from 0.14 µm to 1.2 µm. The results of fluid frictional resistance and heat transfer resistance regarding biofilm formation in the roughest surface showed increases of 28.2% and 19.1% respectively, compared with the smoothest surface. The biofilm thickness taken at the end of the experiment showed variations of up to 74% between the smoothest and roughest surfaces. The thermal efficiency of the heat transfer process in the tube with the roughest surface was 17.4% greater than that in the tube with the smoothest surface. The results suggest that the finish of the inner surfaces of the tubes in heat exchanger-condensers is critical for improving energy efficiency and avoiding biofilm adhesion. This may be utilised to reduce biofilm adhesion and growth in the design of heat exchanger-condensers.