Water Flow Research Articles

Experimental and Numerical Study of Newly Assembled Lightweight Radiant Floor Heating System

In this study, the heating capacity of a new prefabricated assembled hot water radiant modular heating system made from a recycled waste building masonry structure is investigated through experimental and numerical simulation methods. The heating capacity of the system in different working conditions (a water supply temperature of 48 °C, 51 °C, 56 °C, and 61 °C; a flow rate of 0.49 m3/h, 0.35 m3/h, and 0.21 m3/h) is analyzed and verified. A three-dimensional steady-state heat transfer numerical model of the floor heat transfer of the module is established, and the accuracy of the model is verified through the measured results to investigate the heating capacity of this system under different water supply temperatures, flow rates and coil spacings. The results show that the new prefabricated hot water radiant module heating system has a 0.9 °C higher air temperature and 2.1 °C higher average floor surface temperature than the traditional wet floor radiant heating system under the same experimental conditions, and the response time is 44% shorter. The water supply temperature can significantly change the heating capacity of the system, while the water supply flow rate has little effect on the system. The established three-dimensional steady-state numerical model can be in good agreement with the measured results. This study can provide an experimental and theoretical basis for the design and application of such systems.

Analisis Sistem Jaringan Tata Air Pada Lahan Rawa Pasang Surut, Desa Telang Karya, P87S, Banyuasin, Sumatera Selatan

The world's growing population is increasing the need for land, prompting the conversion of productive agricultural land into non-agricultural purposes. This has led to a shift in agricultural development to sub-optimal lands, such as tidal swamplands. However, several problems arise along the way, including water management. A good water management network is necessary for supporting efficient water use. This study aims to analyze the water system network on tidal swamps to support agricultural activities. The survey and field observation methods were used to collect data. The results showed that the water system in Telang Karya Village, P87S, Banyuasin, South Sumatra, experienced sedimentation in the tertiary channel. In channel 3, the thickness of sediment reached 72 cm, resulting in silting, which reduces water discharge. Field observations revealed that sedimentation occurs due to the channels being overgrown by wild plants. This hampers the water flow, causing it to slow down or even stop. In some tertiary channels, the watergate operation needs to be carried out optimally. Maintaining the ideal conditions of tertiary channels is crucial, and watergate operations should be performed based on the needs of the plants.

Monitoring dynamics of biocrust rehabilitation in acid-saturated desert soils

The study explores the aftermath of a wastewater reservoir failure in a phosphate fertilizer industry, resulting in the release of acidic water containing phosphorus and sulfate compounds into the Ashalim stream’s Nature Reserve in the Judean desert, which affected the soil surface biological crusts (biocrusts) layer. The study aims to examine contamination effects on biocrusts over 3 years at two research sites along the stream, compare effects between contaminated sites, assess rehabilitation treatments, and examine their impact on soil characteristics. Hypotheses suggest significant damage to biocrusts due to acidic water flow, requiring human intervention for accelerated restoration. The results indicate adverse effects on biocrust properties, risking its key role in the desert ecosystem. The biocrust layer covering the stream’s ground surface suffered significant physical, chemical, and biological damage due to exposure to industrial process effluents. However, soil enrichment treatments, including biocrust components and organic material, show promising effects on biocrust recovery.

Studies on Recovery of Performance of Fouled Nanocomposite Ultrafiltration Membranes on Cleaning after Treatment of Oil–Water Emulsions

Herein, we discussed the pure water flux recovery of carbon based nanofillers embedded polyvinyl chloride nanocomposite membranes after physical cleaning through backwashing & flushing with flow reversal and after chemical cleaning using hydrochloric acid and caustic soda. The water flux recovery by backwashing is more than that by forward flushing for all the membrane but it is more effective in carbon black (CB) & graphitized carbon black (GCB) carbon-based membranes than relatively hydrophilic multiwalled carbon-nanotube (MWCNT) & carboxylated multiwalled carbon-nanotube (CMWCNT) based nanocomposite membranes. The highest water flux recovery was found ~96% for nanocomposite membranes by backwashing and caustic soda cleaning. The combination of backwashing and caustic soda cleaning could be the most effective method of cleaning of oil-water fouled membranes to restore the maximum water flux.

Studies on Recovery of Performance of Fouled Nanocomposite Ultrafiltration Membranes on Cleaning after Treatment of Oil–Water Emulsions

Herein, we discussed the pure water flux recovery of carbon based nanofillers embedded polyvinyl chloride nanocomposite membranes after physical cleaning through backwashing & flushing with flow reversal and after chemical cleaning using hydrochloric acid and caustic soda. The water flux recovery by backwashing is more than that by forward flushing for all the membrane but it is more effective in carbon black (CB) & graphitized carbon black (GCB) carbon-based membranes than relatively hydrophilic multiwalled carbon-nanotube (MWCNT) & carboxylated multiwalled carbon-nanotube (CMWCNT) based nanocomposite membranes. The highest water flux recovery was found ~96% for nanocomposite membranes by backwashing and caustic soda cleaning. The combination of backwashing and caustic soda cleaning could be the most effective method of cleaning of oil-water fouled membranes to restore the maximum water flux.

Identification of N, P, and K in Solid Waste from Palm Flour Production and Their Benefits as Organic Compost Fertilizer Ingredients

The palm flour manufacturing industry produces a lot of liquid waste and solid waste. The absence of a waste processing system means the waste is dumped around the production house. The large amount of solid waste that is dumped every day causes a buildup of waste on riverbanks. The flow of river water is disturbed, pollutes the river ecosystem, and the smell is unpleasant. The research aims to identify the content of N, P, and K elements in palm flour solid waste. The data obtained will be used as a basic reference for using palm flour solid waste as an alternative compost material considering that most of the Pucang Miliran village area is an agricultural area. The research was carried out by taking a sample of 1 kg of sugar palm flour solid waste and testing it for the content of N, P, and K. Data from laboratory tests were analyzed descriptively supported by a literature study. The research results showed that palm flour solid waste contained Nitrogen (N) of 194.227 mg/Kg, Phosphorus (P) of 410.270 mg/Kg, and Potassium (K) of 832.382 mg/Kg. The presence of the three nutrients N, P, and K in large enough quantities can be considered that palm flour solid waste can be a good alternative material for making organic fertilizer/compost. Further research is needed to determine the comparison and combination of various compost material compositions to produce the best palm solid waste compost.

Identification of N, P, and K in Solid Waste from Palm Flour Production and Their Benefits as Organic Compost Fertilizer Ingredients

The palm flour manufacturing industry produces a lot of liquid waste and solid waste. The absence of a waste processing system means the waste is dumped around the production house. The large amount of solid waste that is dumped every day causes a buildup of waste on riverbanks. The flow of river water is disturbed, pollutes the river ecosystem, and the smell is unpleasant. The research aims to identify the content of N, P, and K elements in palm flour solid waste. The data obtained will be used as a basic reference for using palm flour solid waste as an alternative compost material considering that most of the Pucang Miliran village area is an agricultural area. The research was carried out by taking a sample of 1 kg of sugar palm flour solid waste and testing it for the content of N, P, and K. Data from laboratory tests were analyzed descriptively supported by a literature study. The research results showed that palm flour solid waste contained Nitrogen (N) of 194.227 mg/Kg, Phosphorus (P) of 410.270 mg/Kg, and Potassium (K) of 832.382 mg/Kg. The presence of the three nutrients N, P, and K in large enough quantities can be considered that palm flour solid waste can be a good alternative material for making organic fertilizer/compost. Further research is needed to determine the comparison and combination of various compost material compositions to produce the best palm solid waste compost.

Synthesis of Responsive Membranes for Water Recovery through Desalination of Saline Industrial Effluents

Polysulfone (PSF) and smart polymers (SRPs)—including polyacrylic acid (AAc), poly N-isopropylacrylamide (NIPA), and sulfonated poly(1,4-phenylene ether-ether-sulfone) (SPEES)—were used in the synthesis of responsive membranes (PSF-SRP) for application in sustainable desalination processes involving food industry effluents for water recovery and recycling. With the inclusion of SRPs, PSF-SRP membranes showed different characteristics when compared to the PSF membrane. AAc caused fibers to occur in the surface structure, increasing the MWCO of the PSF membrane, whereas NIPA and SPEES diminished the MWCO, resulting in ultrafiltration and nanofiltration membranes. Furthermore, NIPA and SPEES provided high mechanical and thermal resistance when incorporated into the PSF membrane. The performance of the membranes also showed important changes. In comparison with only PSF, PSF-SPEES and PSF-NIPA increased the water flux and salt rejection percentage by 20–30%. In addition, the highest membrane fouling resistance was observed with PSF-NIPA, while PSF-AAc and PSF-NIPA-AAc presented the lowest resistances. Therefore, PSF-NIPA and PSF-SPEES resulted in membrane improvement, including stimuli-responsive properties, allowing for effective saline effluent treatment.

Synthesis of Responsive Membranes for Water Recovery through Desalination of Saline Industrial Effluents

Polysulfone (PSF) and smart polymers (SRPs)—including polyacrylic acid (AAc), poly N-isopropylacrylamide (NIPA), and sulfonated poly(1,4-phenylene ether-ether-sulfone) (SPEES)—were used in the synthesis of responsive membranes (PSF-SRP) for application in sustainable desalination processes involving food industry effluents for water recovery and recycling. With the inclusion of SRPs, PSF-SRP membranes showed different characteristics when compared to the PSF membrane. AAc caused fibers to occur in the surface structure, increasing the MWCO of the PSF membrane, whereas NIPA and SPEES diminished the MWCO, resulting in ultrafiltration and nanofiltration membranes. Furthermore, NIPA and SPEES provided high mechanical and thermal resistance when incorporated into the PSF membrane. The performance of the membranes also showed important changes. In comparison with only PSF, PSF-SPEES and PSF-NIPA increased the water flux and salt rejection percentage by 20–30%. In addition, the highest membrane fouling resistance was observed with PSF-NIPA, while PSF-AAc and PSF-NIPA-AAc presented the lowest resistances. Therefore, PSF-NIPA and PSF-SPEES resulted in membrane improvement, including stimuli-responsive properties, allowing for effective saline effluent treatment.

Alcohol-alcohol-based draw solute minimizes the reverse solute flux in forward osmosis desalination.

Recently, alcohol-based draw solute (DS), i.e., alcohol with water, is one of the trending research topics in forward osmosis (FO) because of its performance and ease of regeneration. Nevertheless, the higher reverse solute flux (RSF) of the alcohol-based DS hinders its commercialization in water and wastewater treatment applications. This research aims to minimize the RSF of the alcohol-based DS in FO by investigating the possibility of using alcohol-alcohol-based draw solutes for the first time. Three alcohol-alcohol-based draw solutions, namely, (1) E70 + IPA30 (ethanol: 70% + isopropanol: 30%), (2) E40 + IPA60 (ethanol: 40% + isopropanol: 60%), and (3) E10 + IPA90 (ethanol: 10% + isopropanol: 90%), were prepared and the properties (including osmolality, shear stress, and viscosity) of the DS were first investigated followed by the parametric investigation (concerning temperature and concentration). The results were further analyzed with the fixed-point iterative method in MATLAB to obtain the performance parameters. Results reveal that the E10 + IPA90 mixture yields a lower RSF of 40.62g/m2/h and specific reverse solute flux of3.78g/L with a considerably good water flux and recovery percentage of 11.47 LMH and 26.29%, respectively, as compared to other DS E70 + IPA30 and E40 + IPA60 at 25°C. Thus, E10 + IPA90 is recommended as a potential candidate to be used as a DS in FO.

Study of novel Zn-MOF-II modified polymeric membrane in wastewater treatment containing oily waste and humic acid (NOM)

ABSTRACT The prime objective of the present work was to synthesise the polymeric membrane with Zn-MOF-II nanoparticles using the phase inversion method to purify oily wastewater and NOM. The dead-end filtration system was utilised to analyse the performance of fabricated membranes (without and with Zn-MOF-II), various feeds of 100 ppm concentration used, such as organic pollutants and oil effluent at 250 kPa and atmospheric temperature conditions. The following study involves the compaction factor, pure water flux, all mixed matrix membrane permeability, humic acid rejection, and oil–water emulsion rejection, contact angle, and liquid–liquid displacement porosimetry (LLDP). Scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy-attenuated total reflection (FTIR-ATR) goniometer were used to characterise the polymeric membranes. The FTIR-ATR spectra of the modified membrane exhibit a characteristic peak between 2,900 and 3,000 cm−1 associated with the presence of the –COOH group. The nanoparticles and polymer matrix were well compatible, as evidenced by SEM images of the polymeric membrane containing Zn-MOF-II nanoparticles. The maximum value of percentage rejection of oily wastewater (above 88.89%) and humic acid (above 86.88%) was obtained for the polymeric membrane containing Zn-MOF-II nanoparticles.

Alcohol-alcohol-based draw solute minimizes the reverse solute flux in forward osmosis desalination.

Recently, alcohol-based draw solute (DS), i.e., alcohol with water, is one of the trending research topics in forward osmosis (FO) because of its performance and ease of regeneration. Nevertheless, the higher reverse solute flux (RSF) of the alcohol-based DS hinders its commercialization in water and wastewater treatment applications. This research aims to minimize the RSF of the alcohol-based DS in FO by investigating the possibility of using alcohol-alcohol-based draw solutes for the first time. Three alcohol-alcohol-based draw solutions, namely, (1) E70 + IPA30 (ethanol: 70% + isopropanol: 30%), (2) E40 + IPA60 (ethanol: 40% + isopropanol: 60%), and (3) E10 + IPA90 (ethanol: 10% + isopropanol: 90%), were prepared and the properties (including osmolality, shear stress, and viscosity) of the DS were first investigated followed by the parametric investigation (concerning temperature and concentration). The results were further analyzed with the fixed-point iterative method in MATLAB to obtain the performance parameters. Results reveal that the E10 + IPA90 mixture yields a lower RSF of 40.62g/m2/h and specific reverse solute flux of3.78g/L with a considerably good water flux and recovery percentage of 11.47 LMH and 26.29%, respectively, as compared to other DS E70 + IPA30 and E40 + IPA60 at 25°C. Thus, E10 + IPA90 is recommended as a potential candidate to be used as a DS in FO.

A combined linear and sinusoidal empirical model for shale gas wellhead pressure and production rates considering fluctuations in gas–water flow

The relationship between wellhead pressure and gas–water flow rate is an important research topic. Nevertheless, a comprehensive theoretical model has not been developed mainly due to complicated field conditions. Finding data-driven models is therefore another crucial direction of research. Despite the development of data-driven models, existing models are not exhaustive. The main disadvantage of the conventional Gilbert model is that it can be used only when both gas and water are produced. Whereas in shale gas production, it is common that only gas or water is produced. To tackle these problems, this study proposes a different type of empirical model considering choke cross-sectional area, volume factors of gas and water, and nonlinearity apart from gas and water rates. In comparison, the Gilbert model only considers choke diameter. The improvements allow the proposed model to only require the existence of one of gas and water, thus expanding the application scope of Gilbert’s model. The applications using field data from 49 shale gas wells indicate the proposed model has the best accuracy among all models compared. The derivation of the proposed model benefits both theoretical and data-driven studies on the relationship between wellhead pressure and gas–water flow rate for hydrocarbon production wells.

Bingham and herschel-bulkley fluids flow regimes in rough-walled rock fractures

Flow of typical non-Newtonian fluids such as cement grouts can experience different regimes as the Reynolds number (Re) changes, understanding of which is important for design and operation of rock grouting in various rock engineering applications. Here, flow regimes of representative non-Newtonian fluids, i.e., Bingham and Herschel–Bulkley (H–B) fluids, are numerically investigated with experimental validations. Three tensile rock fracture surfaces originated from a fine-grained sandstone, a medium-grained sandstone and a medium-grained granite samples are used to create rough-walled fracture models with variable aperture structures. Flow of groundwater, Bingham and H–B fluids through these fractures is numerically simulated respectively, by solving the full mass and momentum conservation equations with the Re ranging from 0.01 to 1000. The regimes for these fluids flowing through the fractures are characterized. Laboratory flow tests are conducted in a cylindrical granite fracture sample to verify the characterized flow regimes. The results reveal important differences of flow regimes between Newtonian and non-Newtonian fluids. Specifically, the transmissivity for water flow is constant when Re is relatively small until the Re reaches certain critical values; the transmissivity for Bingham and H–B fluids flow increases with increasing Re until asymptotically reaches certain peak values, followed by a descending stage when Re is relatively large. The critical (water) and peak (Bingham and H–B fluids) values are affected by surface roughness, that is, a rougher surface results in smaller critical and peak values as well as greater discrepancies compared to the analytical solutions based on the smoothed parallel plates model. These results show that a peak or optimum transmissivity is achievable in a specific range of Re (Re = 10–100 for the fractures studied). This new finding can potentially help optimize the injection pressure or flow rate in rock grouting practices.

Impacts of droughts and human activities on water quantity and quality: Remote sensing observations of Lake Qadisiyah, Iraq

Water quantity and quality in lakes are closely linked to the compounding effects of climate change and human activities in their catchments, especially for lakes located in semi-arid and arid regions where water resources are scarce. Whilst knowledge gaps exist for these effects in semi-arid and arid region lakes due mainly to the lack of long-term in situ monitoring data. By using satellite remote sensing data, this study firstly investigated the variations of water level, chlorophyll-a concentration (Chl-a) and turbidity in Lake Qadisiyah, Iraq between 2000 and 2019. Results showed that the average water level was 138.3 m in 2000–2019, it decreased clearly in 2001, 2009, 2015 and 2018 with the lowest value of 120 m in July 2015. The mean Chl-a was 6.3 mg/m3 and it showed an overall increasing trend during 2000 and 2019. Turbidity showed extremely high values (>10 NTU) in 2009 and 2017–2018 compared to the mean value of 3.6 NTU in 2000–2019. The boosted regression tree (BRT) was then used to explore the relationship between those variations and El Niño-Southern Oscillation, droughts, meteorological factors and land use land cover changes in the catchment. Results revealed that water level declines were mainly associated with droughts led by La Niña events. Chl-a increase in the lake were mainly explained by built-up area increase and water area decrease in the catchment, with a relative contribution of 29.2 % and 28.6 % respectively. Water area changes in the catchment were the main factor influencing turbidity explaining 55.3 % of the variation. An exception water level decline in 2014–2016 was also observed when there was no drought, which was most likely caused by the cut off of water flow upstream and the release of water from the dam during periods of war. The findings in this study underscored the impacts of climate and human activities on water quantity and quality in semi-arid region lakes. Actions such as improving water use efficiency, establishing water storages, and enhancing cross-border cooperation are therefore recommended to deal with extreme events. Pollution control measures in the catchment are also suggested to prevent water quality deterioration in the lake.

Effects of 2D hydrodynamic model resolution on habitat estimates for rearing Coho Salmon in contrasting channel forms

AbstractEstimating the impacts of water allocation decisions on fish populations and habitat availability is an important part of environmental flow assessments, especially in locations where water resources are limited. Two‐dimensional hydrodynamic models (2DHMs) are commonly coupled with biological models to estimate fish habitat quality, area, and capacity across a range of proposed streamflows. Increasingly, resource managers are relying on landscape‐scale model domains with coarse model resolutions to maintain feasible computational loads, but this may affect habitat estimates if the mesh element size of the model exceeds the spatial scale relevant to the organism. We investigated how coarsening the resolution of a 2DHM influences the area and spatial distribution of estimated Coho Salmon (Oncorhynchus kisutch) fry habitats. We used an interpolation scheme that upscaled mesh elements from a high‐resolution (0.25 m2) 2DHM to quantify and visualize the effects of 2DHM resolution on estimates of Coho Salmon fry habitat for two contrasting channel morphologies and across a broad range of streamflows. Estimates of Coho Salmon fry habitat at increasingly coarser resolutions led to 20%–50% reductions in weighted usable habitat area (WUA) across several streamflow scenarios for a complex channel type, but did not impact estimates in a confined, flume‐like channel. Additionally, flow‐to‐habitat area relationships were not congruent at a given streamflow when resolution coarsened. Along with almost 500% more high‐quality habitat area estimated in the complex channel type over the confined, discrepancies in habitat area increased with higher flows in areas defined as optimal for rearing Coho Salmon fry. Considering that complex channel types contain critical habitat for Coho Salmon fry, this study suggests coarse 2DHM resolutions may exclude important wetted edge and off‐channel habitats from environmental flow assessments.

Effects of 2D hydrodynamic model resolution on habitat estimates for rearing Coho Salmon in contrasting channel forms

AbstractEstimating the impacts of water allocation decisions on fish populations and habitat availability is an important part of environmental flow assessments, especially in locations where water resources are limited. Two‐dimensional hydrodynamic models (2DHMs) are commonly coupled with biological models to estimate fish habitat quality, area, and capacity across a range of proposed streamflows. Increasingly, resource managers are relying on landscape‐scale model domains with coarse model resolutions to maintain feasible computational loads, but this may affect habitat estimates if the mesh element size of the model exceeds the spatial scale relevant to the organism. We investigated how coarsening the resolution of a 2DHM influences the area and spatial distribution of estimated Coho Salmon (Oncorhynchus kisutch) fry habitats. We used an interpolation scheme that upscaled mesh elements from a high‐resolution (0.25 m2) 2DHM to quantify and visualize the effects of 2DHM resolution on estimates of Coho Salmon fry habitat for two contrasting channel morphologies and across a broad range of streamflows. Estimates of Coho Salmon fry habitat at increasingly coarser resolutions led to 20%–50% reductions in weighted usable habitat area (WUA) across several streamflow scenarios for a complex channel type, but did not impact estimates in a confined, flume‐like channel. Additionally, flow‐to‐habitat area relationships were not congruent at a given streamflow when resolution coarsened. Along with almost 500% more high‐quality habitat area estimated in the complex channel type over the confined, discrepancies in habitat area increased with higher flows in areas defined as optimal for rearing Coho Salmon fry. Considering that complex channel types contain critical habitat for Coho Salmon fry, this study suggests coarse 2DHM resolutions may exclude important wetted edge and off‐channel habitats from environmental flow assessments.

Southwest Pacific Ocean Warming Driven by Circulation Changes

AbstractAn area of ocean centered on 179°E, 46°S has warmed to full depth since 2006, with surface warming around 5 times the global rate. This Subtropical Front area is associated with a confluence of warm, salty, subtropical water from the north carried in a western boundary current and cold, fresh, subantarctic water from the south carried in the northernmost branch of the Antarctic Circumpolar Current. Temperature and salinity changes observed from Argo floats indicate that the Subtropical Frontal Zone has moved west ∼120 km, creating this area of strong warming analogous to changes in extension regions of other western boundary currents. The warming is a result of changes in the local flows of subantarctic water, evident in satellite altimeter data and 1,000 m Argo trajectories, which in turn likely result from changes in meridional ocean heat content and winds. The warming has placed this biologically‐significant region in almost perpetual marine heatwave conditions.

Impact of Anthropogenic Activities on Sedimentary Records in the Lingdingyang Estuary of the Pearl River Delta, China

High-intensity anthropogenic activities have greatly altered the estuarine-shelf depositional processes of sediments, and the intensity and frequency of the impacts of human interventions have far exceeded the natural development of estuarine systems. Since the reform and opening up, human activities such as dams, sand mining, channel dredging, and reclamation have already caused anomalous changes in the dynamical–sedimentary–geomorphological processes of the Lingdingyang Estuary (LE). Analyzing the impact of high-intensity anthropogenic activities on sedimentary processes and the hydrodynamic environment through sedimentary records can provide a scientific basis for predicting the evolution of the estuary and the sustainable development of the Guangdong–Hongkong–Macao Greater Bay Area. The aims of this study are to reveal the impact of varying intensity human activities across different periods on depositional pattern and conduct a preliminary investigation into the spatial differences in sedimentary characteristic attributed to human activities. Two cores (LD11 and LD13) located in the LE were selected for continuous scanning of high-resolution XRF, grain size, and 210Pbex dating tests, and scrutinized with the previous studies of the historical process of human activities in the LE. The results show the following: (1) The abrupt alterations in 210Pbex, geochemical indices, and grain size in LD13 happened in close proximity to the 95 cm layer, suggesting a shift in the sedimentary environment during 1994. (2) In the context of the continuous reduction in water and sediment flux into the LE after 1994, the large-scale and high-intensity human activities like sand mining, channel dredging, and reclamation are responsible for the sedimentation rate increase rather than decrease, the coarsening of sediment fractions, the frequent fluctuations in Zr/Rb, Zr/Al, Sr/Fe, and Sr/Al ratios, and the increase in anomalous extremes. (3) Sedimentary records found in locations varying in anthropogenic intensities differ greatly. Compared with the nearshore siltation area, the grain size composition in the channel area is noticeably coarser and exhibits a wider range of grain size variations. The 210Pbex is strongly perturbed and the vertical distribution is disturbed; the phenomenon of multiple inversions from the surface downwards is shown, making it impossible to carry out sedimentation rate and dating analysis, and the geochemical indicators have changed drastically without any obvious pattern. The evidence of the human activities can be retrieved in the sedimentary record of the estuary and provide a different angle to examine the impacts of the human activities.

Aqp4a and Trpv4 mediate regulatory cell volume increase for swimming maintenance of marine fish spermatozoa

Volume regulation is essential for cell homeostasis and physiological function. Amongst the sensory molecules that have been associated with volume regulation is the transient receptor potential vanilloid 4 (TRPV4), which is a non-selective cation channel that in conjunction with aquaporins, typically controls regulatory volume decrease (RVD). Here we show that the interaction between orthologous AQP4 (Aqp4a) and TRPV4 (Trpv4) is important for regulatory volume increase (RVI) in post-activated marine fish spermatozoa under high osmotic stress. Based upon electrophysiological, volumetric, and in vivo and ex vivo functional experiments using the pharmacological and immunological inhibition of Aqp4a and Trpv4 our model suggests that upon ejaculation and exposure to the hypertonic seawater, spermatozoon shrinkage is initially mediated by water efflux through Aqp1aa in the flagellar tail. The shrinkage results in an increase in intracellular Ca2+ concentration, and the activation of sperm motility and a Na+/K+/2Cl− (NKCC1) cotransporter. The activity of NKCC1 is required for the initiation of cell swelling, which secondarily activates the Aqp4a-Trpv4 complex to facilitate the influx of water via Aqp4a-M43 and Ca2+ via Trpv4 and L-type channels for the mediation of RVI. The inhibitory experiments show that blocking of each of these events prevents either shrinkage or RVI. Our data thus reveal that post-activated marine fish spermatozoa are capable of initiating RVI under a high hypertonic stress, which is essential for the maintenance of sperm motility.