Collected Surface Water Research Articles

The Role of Innovative Technologies in Reducing the Load on Wastewater Treatment Plants in the Cities of the Republic of Kazakhstan

This article highlights an important aspect of modern management of urban wastewater treatment plants in the cities of the Republic of Kazakhstan, focusing on economic assessment of the effectiveness of integrated use of ecosystem solutions for surface (atmospheric) water collection. The study presents an analysis of the impact of such solutions on reducing the burden on wastewater treatment plants and optimizing operating costs. The authors consider different technologies and methods for surface water harvesting, including the use of green spaces, ecosystem elements, and innovative engineering solutions. The paper emphasizes the importance of considering economic aspects when deciding on the implementation of such ecosystem approaches. It presents examples of countries that have implemented, or are currently implementing integrated surface water management and the methods of ecosystem solutions that have shown the most positive ecological and economic effects after their implementation. In addition, the work considers and calculates the main components and concentrations of pollutants entering water bodies from urban areas. The authors conclude that the integrated use of ecosystem solutions for surface water harvesting is a promising approach that will not only reduce the burden on wastewater treatment plants but also contribute to the creation of more sustainable and cost-effective water management systems in the cities of the Republic of Kazakhstan.

The Cooling Effect of Oasis Reservoir‐Riparian Forest Systems in Arid Regions

AbstractIn arid regions with limited water resources, numerous reservoirs have been built to support economic and social development. However, how the construction of reservoirs interacts with the surrounding ecosystem to affect temperature remains unclear. Spanning 2018 to 2022 in the Shiyang River Basin, we collected surface water and precipitation, as well as stem and soil samples. Using isotopic methods, we quantified how evaporation in the oasis reservoir‐riparian forest system affects the local climate. Our findings show that the latent heat released by evapotranspiration from the reservoir and riparian forest system reduces the daily maximum temperature and daily temperature range by 7°C and 6°C respectively, compared to downstream areas with sparse vegetation around artificial lakes. Additionally, it enhances local moisture recycling, increasing precipitation. This study reveals regional cooling effect due to interactions between water bodies, the atmosphere, and vegetation. We propose that establishing reservoir‐riparian forest systems can positively impact local climate regulation and serve as an effective strategy for adapting to global climate warming.

The Influence of Climatic and Geographical Conditions on the Volume and Spatial Solutions of Shopping and Entertainment Centers of the Republic of the Congo

The article examines the main climatic and geographic conditions of the Republic of Congo. It was revealed that design in the Republic of Congo is carried out in a warm and humid climate. Based on examples of analyzed construction experience in humid climates, the author made proposals for architectural techniques for organizing the space of shopping and entertainment centers at three hierarchical levels. At the urban planning level, the author proposed organizing the landscape of streets and park areas in such a way as to organize the natural drainage of water from the surface and from the upper balls of the soil. At the level of building formation, techniques are associated with organizing the collection of rainwater through the shaping of the building. The possibilities of protecting retail spaces from rain using canopies are also considered. At the spatial level, it is proposed to drain the swampy area on the territory of the shopping and entertainment center by creating canals. It is proposed to design public areas of shopping centers in such a way that public areas, using their shape, can collect surface water from rain. Further research by the author will be aimed at creating volumetric-spatial methods for organizing shopping center buildings, taking into account the warm, humid climate of the region. Also, further research will be aimed at studying the ventilation of internal open spaces of shopping and entertainment centers. These studies are aimed at creating comfortable urban hygienic conditions within the boundaries of public centers, which should become shopping and entertainment centers.

Validation of a new sampler for radon gas measurements in surface water

Radon gas (Rn-222) in water poses health risks due to radiation exposure, yet it's also an important tracer for studying natural systems. Sampling procedures for Rn-222 analysis are very sensitive to potential losses of the gas to the atmosphere. It requires a well-defined and properly validated protocol to ensure accuracy and reliability. A novel sampler was developed to collect surface water from a distance (e.g. from bridges), addressing logistic challenges posed by topography. The sampler, manually operated, ensures precise depth-specific sampling throughout the water column. A three-stage validation process (technical performance test, uncertainty estimations and preliminary test) was followed to validate the protocol.•The comparison of the technical procedure for analysis and measurement through Liquid Scintillation Counting is statistically robust (one-way ANOVA p-value = 0.96).•For the protocol proposed for Rn-222 determination, the estimated sampling and measurement uncertainties (k = 2) are respectively 5% and 15%. These are compatible with the literature and the laboratory's precision.•Preliminary tests, with meaningful patterns identified and possibly related to the river's hydrodynamics, revealed a very reliable protocol, even in low Rn-222 concentrations.Therefore, the sampler has demonstrated a good analytical reproducibility and was considered validated for Rn-222 determination in surface waters.

A four-season exploration of surface water quality and trophic status in the highly dynamic waters of Karun-4 Dam Lake, SW Iran

This study explores seasonal fluctuations in water quality and phytoplankton communities within Karun-4 Dam Lake, the largest double-arch dam in the Middle East situated in Iran. Employing a systematic approach, 26 sampling stations were strategically selected to collect surface water samples at a depth of 50 cm during the midpoints of each season throughout 2019. Significant seasonal variations in water quality parameters and phytoplankton composition were observed. Predominant species included Chrysophyceae (38%) and Bacillariophyceae (32%), indicative of nutrient-rich conditions, particularly during spring and summer, as evidenced by the eutrophic state (Carlson Trophic State Index: 59.43 and 53.96, respectively). Summer exhibited the highest diversity (Shannon–Wiener Index = 2.27) and lowest evenness (Pielou’s Evenness Index = 0.21). PCA and CCA analyses revealed season-specific preferences for nutrients and ions among phytoplankton species. Water temperature emerged as a crucial factor in spring and summer, while environments with elevated bicarbonate and alkalinity levels were less favorable during winter and fall. This study provides essential insights into Karun-4 Lake's dynamic ecological conditions, underscoring the necessity for ongoing monitoring to discern long-term trends and anthropogenic impacts for effective ecosystem management.

Hydrochemical and Stable Isotopic Characteristics and Transformation Relationship of Water Bodies in the Guohe River Basin, Anhui Province

The Guohe River Basin in Anhui Province was selected as the research area for this study. By collecting surface water, shallow groundwater, and middle-deep groundwater samples, various hydrochemical parameters and stable isotopes of water in different water bodies were analyzed using methods such as the Gibbs diagram, ion ratios, and MixSIAR model to reveal and quantify the transformation relationships between these water bodies. The results indicated that both surface water and groundwater in the study area were predominantly neutral to weakly alkaline. The hydrochemical types of surface water were mainly characterized by Cl·SO4·HCO3-Na and Cl·SO4-Na types, whereas the shallow groundwater exhibited HCO3-Ca·Mg and HCO3-Mg·Na types, and the middle-deep groundwater was of the Cl·HCO3-Na type. The hydrochemical characteristics of various water bodies were influenced by multiple factors such as rock weathering, evaporation concentration, and positive cation exchange. The distribution characteristics of δ18O and δ2H values in surface water and groundwater indicated that atmospheric precipitation was the main water source. The δ18O and δ2H in groundwater were significantly correlated with K+, Na+, Cl-, SO42-, and NO3-. According to the analysis using the MixSIAR model, the contribution of atmospheric precipitation to surface water was 46.5 %, whereas the contribution from shallow groundwater was 53.5 %. The sources of shallow groundwater were identified as atmospheric precipitation (57.4 %) and surface water (42.6 %), and the main source of supply for middle-deep groundwater was lateral flow from upstream groundwater.

Discovery of novel benzotriazole ultraviolet stabilizers in surface water

The comprehensive understanding of the occurrence of benzotriazole UV stabilizers (BZT-UVs) in environmental surface water is imperative due to their widespread application and potential aquatic toxicity. We conducted an analysis of 13 traditional BZT-UVs in surface water samples collected from Taihu Lake (TL, n = 23) and Qiantang River (QR, n = 22) in China. The results revealed that 5‑chloro-2-(3,5-di-tertbutyl-2-hydroxyphenyl)-benzotriazole (UV-327) was consistently the predominant BZT-UV in water samples from TL (mean 16 ng/L; detection frequency 96 %) and QR (14 ng/L; 91 %). Furthermore, we developed a characteristic fragment ion-based strategy to screen and identify unknown BZT-UVs in collected surface water, utilizing a high-resolution mass spectrometer. A total of seven novel BZT-UVs were discovered in water samples, and their chemical structures were proposed. Four of these novel BZT-UVs were further confirmed with standards provided by industrial manufacturers. Semi-quantitative analysis revealed that among discovered novel BZT-UVs, 2-(2‑hydroxy-3‑tert‑butyl‑5-methylphenyl)-benzotriazole was consistently the predominant novel BZT-UV in TL (mean 4.1 ng/L, detection frequency 70 %) and QR (2.8 ng/L, 77 %) water. In TL water, the second predominant novel BZT-UV was 2-(3-allyl-2‑hydroxy-5-methylphenyl)-2H-benzotriazole (mean 3.9 ng/L, <LOD–11 ng/L), while in QR water, it was 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4‑hydroxy-benzotriazole (mean 2.1 ng/L, <LOD–3.6 ng/L). Subsequent studies are needed to elucidate the environmental source, behaviors, and aquatic toxicity of these newly identified BZT-UVs in surface water.

Risk assessment of China’s Eastern Route of the South-to-north Water Diversion Project from the perspective of Phthalate Esters occurrence in the impounded lakes

Phthalate esters (PAEs) are widely utilized and can accumulate in lacustrine ecosystems, posing significant ecological and human health hazards. Most studies on PAEs focus on individual lakes, lacking a comprehensive and systematic perspective. In response, we have focused our investigation on characteristic lakes situated along the Eastern Route of the South-to-north Water Diversion Project (SNWDP-ER) in China. We have detected 16 PAE compounds in the impounded lakes of the SNWDP-ER by collecting surface water samples using solid-phase extraction followed by gas chromatography analysis. The concentration of PAEs were found to between 0.80 to 12.92 μg L−1. Among them, Bis (2-ethylhexyl) phthalate (DEHP) was the most prevalent, with mean concentration of 1.56 ± 0.62 μg L−1 (48.44%), followed by Diisobutyl phthalate (DIBP), 0.64 ± 1.40 μg L−1 (19.87%). Spatial distribution showed an increasing trend in the direction of water flow. Retention of DEHP and DIBP has led to increased environmental risks. DEHP, Dimethyl phthalate (DMP) etc. determined by agriculture and human activities. Additionally, Dibutyl phthalate (DBP) and DIBP mainly related to the use of agricultural products. To mitigate the PAEs risk, focusing on integrated management of the lakes, along with the implementation of stringent regulations to control the use of plasticizes in products.

Temporal and spatial variations and driving factors of phytoplankton in Yongjiang River estuary

To explore the temporal and spatial variations in phytoplankton community in small estuaries, we collected surface water samples from Yongjiang River estuary during wet, normal, and dry seasons and determined the main driving factors of phytoplankton community. A total of 358 species belonging to nine phyla and 123 genera were identified in all seasons. During wet, normal, and dry seasons, species number was 276, 154 and 151, and the abundance was (170.45±225.43)×103, (51.92±30.28)×103 and (31.65±12.79)×103 cells·L-1, respectively. Diatoms dominated the phytoplankton community, and the main dominant species were Cyclotella meneghiniana, Skeletonema costatum, and Paralia sulcata. Shannon diversity and Pielou evenness indices decreased from inside mouth to outside mouth in wet season, but there was no obvious spatial difference in normal season or dry season. Results of non-metric multidimensional scaling analysis and analysis of similarities showed that phytoplankton community composition differed significantly among different regions (inside, at and outside mouth) and different seasons. In wet season, phytoplankton abundance was significantly positively correlated with temperature, dissolved inorganic nitrogen, and dissolved reactive phosphorus, but significantly negatively correlated with salinity. In normal season, phytoplankton abundance was significantly negatively correlated with temperature. In dry season, it was not significantly correlated with environmental factors. Results of redundancy analysis showed that temperature, salinity, ammonium and dissolved reactive phosphorus explained the variations in phytoplankton community by 19.5%, 11.9%, 9.4% and 8.2%, respectively. These results revealed high dominance of diatoms and the main driving factors (temperature, salinity and nutrients) of phytoplankton community in Yongjiang River estuary.

Environmental DNA recovers fish composition turnover of the coral reefs of West Indian Ocean islands.

Islands have been used as model systems to study ecological and evolutionary processes, and they provide an ideal set-up for validating new biodiversity monitoring methods. The application of environmental DNA metabarcoding for monitoring marine biodiversity requires an understanding of the spatial scale of the eDNA signal, which is best tested in island systems. Here, we investigated the variation in Actinopterygii and Elasmobranchii species composition recovered from eDNA metabarcoding along a gradient of distance-to-reef in four of the five French Scattered Islands in the Western Indian Ocean. We collected surface water samples at an increasing distance from reefs (0 m, 250 m, 500 m, 750 m). We used a metabarcoding protocol based on the 'teleo' primers to target marine reef fishes and classified taxa according to their habitat types (benthic or pelagic). We investigated the effect of distance-to-reef on β diversity variation using generalised linear mixed models and estimated species-specific distance-to-reef effects using a model-based approach for community data. Environmental DNA metabarcoding analyses recovered distinct fish species compositions across the four inventoried islands and variations along the distance-to-reef gradient. The analysis of β-diversity variation showed significant taxa turnover between the eDNA samples on and away from the reefs. In agreement with a spatially localised signal from eDNA, benthic species were distributed closer to the reef than pelagic ones. Our findings demonstrate that the combination of eDNA inventories and spatial modelling can provide insights into species habitat preferences related to distance-to-reef gradients at a small scale. As such, eDNA can not only recover large compositional differences among islands but also help understand habitat selection and distribution of marine species at a finer spatial scale.

Contribution of carbonate-derived dissolved inorganic carbon into autochthonous particulate organic carbon in two small temperate Korean rivers (Geum and Seomjin)

In this study, we estimated the contributions of carbonate mineral weathering to dissolved inorganic carbon (DIC) and carbonate-derived DIC to autochthonous particulate organic carbon (POC) in two temperate Korean rivers. We combined stoichiometric and stable carbon isotopic approaches to calculate the contribution of autochthonous POC, considering diverse riverine DIC sources. We collected surface water samples from May 2016 to May 2018 and analyzed the major ion composition of rivers along with the concentrations and stable carbon isotopes of DIC. Our estimates showed that the relative abundances of carbonate mineral weathering (0.41 ± 0.11 in the Geum River and 0.43 ± 0.07 in the Seomjin River) were only slightly lower than those of silicate mineral weathering (0.59 ± 0.1 in the Geum River and 0.57 ± 0.07 in the Seomjin River). The resulting percentage contributions of DIC derived from the carbonate mineral weathering to riverine autochthonous POC, if we consider the additional DIC sources of atmospheric and soil-derived CO2, were 10 ± 3 % in the Geum River and 2 ± 1 % in the Seomjin River. The calculated annual fluxes of carbonate-derived DIC for 2016–2018 were 23.2 ± 0.3 Gg C yr−1 in the Geum River and 1.1 ± 0.4 Gg C yr−1 in the Seomjin River. Moreover, the calculated annual fluxes of carbonate-derived POC were 3.6 ± 0.5 Gg C yr−1 in the Geum River and 0.1 ± 0.7 Gg C yr−1 in the Seomjin River. Accordingly, our study provides the first insight into the contribution of carbonate-derived DIC to riverine autochthonous POC in small temperate Korean river systems, dominated by silicate rocks.

Efficiency Evaluation of Surface Water Collection Infrastructure during Floods: Information Analysis and Zoning Management

Objective: Flood events, occurring as natural and unexpected phenomena, have become increasingly prevalent in recent decades. Assessing the probability of flood risk and creating flood zoning maps in vulnerable areas, particularly urban regions, are crucial for mitigating flood damages and managing such events. This research aims to determine the flood-prone zones along the Darakeh River, located in Tehran, the capital city of Iran, by integrating the hydraulic model HEC-RAS with Geographic Information System (GIS). Methods: After establishing the physiographic characteristics of the watershed, including area, perimeter, elevation, slope, and time of concentration, influential factors on flood occurrences such as permeability, hydrological soil groups, runoff potential, curve number, land use, and vegetation cover were identified. This information, along with other hydraulic data and flow specifications such as boundary conditions, roughness coefficients, and design discharge, was incorporated into the HEC-RAS model. The model was executed for different return periods of 2, 5, 10, 25, 50, and 100 years. Subsequently, the hydraulic model outputs were transferred to the GIS model to obtain the flood-prone zones along the Darakeh River for the aforementioned return periods. Results: As observed, in the middle section of the Khoshke Channel, which has a lower gradient, the floodplain exhibits a wider extent. Furthermore, along the course of the river and after passing through a stretch of the Khoshke Channel with a reduced gradient, the floodplain's area increases up to the location of the western flood channel. Conclusion: It is concluded that areas with lower river slopes exhibited larger flood-prone zones, highlighting the necessity of increased attention to prevent significant damages in urban areas during flood events.

Filtration of Grey Water Using Herbs in a Columnar Evaluation

Filtration of Grey Water Using Herbs in a Columnar Evaluation

Spatial distributions, behaviors, and sources of PCDD/Fs in surface water and sediment from the Yangtze River Delta

The Yangtze River Delta (YRD), one of the most economically developed and industrialized regions in China, is confronted with challenges arising from rapid urbanization, particularly environmental pollution. The collection of surface water and sediment samples from forty-nine sites in the YRD was conducted to analyze 2378-substituted polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) congeners. The detected concentrations of PCDD/Fs were 0–5.3 pg TEQ/L in water and 0.12–1493 pg TEQ/g dw in sediment. The PCDD/Fs contamination in the sediment was widespread in the YRD. There were variations in the congener characteristics of PCDD/Fs in surface water and sediment. The proportion of OCDD was significantly lower in surface water samples compared to sediment, while the less chlorine-substituted homologs were found in larger proportions. To understand the partitioning and behavior of dioxins within the water-sediment system, we calculated the organic carbon normalized partition coefficients and fugacity fraction (ff) of PCDD/F congeners. The results revealed that the PCDD/Fs had not attained a state of distributional equilibrium, and the non-specific hydrophobic effect seemed minimally influential on their partitioning between sediment and water. The average ff values, which varied between 0.06 and 0.63, indicated differing migration directions for the PCDD/F congeners. Source identification analysis provided evidence that the dioxins in the river water were primarily attributed to industrial thermal processes. Iron and steel smelting, along with pesticide production and use, were likely responsible for the sediment contamination. This comprehensive analysis underscores the complex nature of PCDD/Fs pollution in the YRD and highlights the necessity for targeted environmental management strategies.

Spatial and seasonal variability of picoplankton abundance and growth rates in the southern Bay of Biscay

Autotrophic and heterotrophic picoplankton play fundamental roles in marine food webs and biogeochemical cycles. However, their growth responses have seldom been jointly assessed, including many temperate regions such as the Bay of Biscay. There, previous studies have shown their relevance in carbon fluxes. We describe here the spatio-temporal variability of the abundances and growth rates of the picoplanktonic groups routinely distinguished by flow cytometry (Synechococcus and Prochlorococcus cyanobacteria, two groups of differently sized picoeukaryotes and two groups of heterotrophic bacteria distinguished by their relative nucleic acid content) in the central Cantabrian Sea (S Bay of Biscay). To that end, from February to December 2021 we collected surface water on 5 occasions from 6 stations distributed along the S Bay of Biscay (6-3°W) and incubated it after removing protistan grazers in order to determine their dynamics along the seasonal cycle as well as the inshore-offshore and the west-east gradients. Seasonal variations in initial and maximum abundances generally matched previous knowledge of the region but growth rates were more variable, with Prochlorococcus and high nucleic acid (HNA) bacteria showing the maximum values (up to 2 d−1) while negative growth was observed in one third of Synechococcus incubations. Temporal differences generally overrode differences along the inshore-offshore gradient in trophic status while in situ and maximum abundances of most of the groups generally decreased towards the east following the increase in stratification and lower nutrient availability. Responses to stratification suggest Prochlorococcus and low nucleic acid (LNA) cells may prevail among autotrophic and heterotrophic bacteria, respectively, in a warmer ocean.

Evaluation of fungal permeated lignocellulosic filter for remediation of water pollutants

The use of biological techniques to remove pollutants from the environment has been long advocated. In this study, we assessed the efficacy of a fungal permeated lignocellulosic filter (mycofilter) in the removal of water pollutants using surface water as the test sample. A wild macrofungus was collected from a field within Osun State University, Oke-Baale, Osogbo, and cultured on potato dextrose agar. Identification was achieved using morphological and PCR techniques. Mycofilters (FCCs) were developed from pure macrofungus mycelium and diced pasteurized corncob (CC). Collected surface water (RW) was passedthrough three mycofilters, each with flow rates of 0.2, 0.5, and 1.0 ml/min. Diced pasteurized corncob (CC) was used as the negative control. Physicochemical parameters including pH, temperature, turbidity, cadmium, copper, iron, zinc, and lead, and microbial parameters i.e. total bacterial count (TBC) and Escherichia coli counts (ECC) of RW, CC, and FCC treated waters were determined. Phenotypically, the fungus was identified as Macrolepiota procera and yielded 650 bp by PCR product assessment on gel electrophoresis. Remarkably, FCC reduced the levels of turbidity, chemical, and microbial contaminants significantly at p = 0.001, &lt; 0.05, and ≤ 0.002 respectively compared to CC. The flow rate of 0.2 ml/min was the most efficient in reducing contaminants in the RW. This study reveals the potential of the Macrolepiota procera permeated filter in reducing water contaminants.

Analysis of the Potential of Watersheds as a Source of Raw Water in the Batang Integrated Industrial Area (KITB) in Cluster 1

The Batang Integrated Industrial Area (KITB) is located in Banyuputih District, Batang Regency, Central Java, with a total area of 4,300 Ha and currently what has been developed is cluster 1 covering an area of 3100 Ha. Water has a central role in human and industrial activities, with potential impacts on health, worker safety, and the environment. The main problem is the uncertainty of raw water supply which poses a risk to Environment Health Safety (EHS). Therefore, this research aims to identify and analyze water sources, by EHS objectives, because safe water supply is key to environmental and worker safety. The water balance method is used to analyze water needs and availability. Analyze water needs in industrial areas by taking into account data for each type of industry. Water availability analysis includes the identification of raw water sources, including groundwater and surface water, taking into account that excessive exploitation of groundwater can hurt EHS. In contrast, surface water and rainwater collection are sustainable alternatives that are relevant to environmental and safety concerns. The research involved calculations using rainfall data from the Subah Rain Station and climatology data from the Central Java Climatology Station during the 2021-2022 period, as well as discharge analysis using the Mock Method. The research results display the potential of the river basin and show that rainwater collection can effectively overcome EHS challenges related to water availability in the Batang Integrated Industrial Area.

Re-Engineering Dew-Harvesting Cactus Macrostructures to Enhance Water Collection as an Adaptive Climate Change Strategy: An Experimental Comparison

The spinal structures found on Copiapoa cinerea var. haseltoniana, an efficient dew-harvesting cactus, were fabricated and evaluated both in a climate chamber and outdoors in dewy conditions. A mix of aluminium and steel was used to fabricate these surfaces, with aluminium being used for everything but the replicated spine features, which were constructed from steel. Each surface was entirely coated with a highly emissive paint containing an alumina–silicate OPUR additive. Three replica versions (stem only, spine only, and stem &amp; spine) were compared to a flat planar reference surface. Experimental results demonstrated that all three biomimetic macro-structured surfaces significantly enhanced dew harvesting compared to the reference surface. It was established that the stem &amp; spine replica, spine replica, and stem replica all demonstrated significantly more dew harvesting, with mean efficiency ratios in respect of the reference surface of 1.08 ± 0.03, 1.08 ± 0.02, and 1.02 ± 0.01, respectively. Furthermore, the method of surface water collection was found to influence the water collection rate. The diagonal run-off flow across a flat planar surface was 34% more efficient than the parallel run-off flow on the same surface. These findings provide valuable insights for the construction and installation of biomimetic-inspired dew-harvesting devices, particularly in regions that are most challenged by decreasing dew yields as a result of climate change.

Effects of tidal cycles on the variability of microbial communities in a semiclosed bay

Shallow sediment-water plays an important role in transforming organic matter in estuaries. As a shallow bay often flanks a large estuary, the estuarine water enters the shallow bay during flood tides and exits during ebb tides. The inundation between flood and ebb tides in the shallow bay serves as an incubation of the bay water and sediment. However, little is known about the effects of tidal cycles on microbial diversity and biogeochemical processes. In Tangjiawan Bay, which is a small bay located on the west side of the Pearl River estuary, we examined changes in microbial diversity and environmental factors by collecting surface water samples between floods and ebbs. Using high-throughput sequencing targeting 16S and 18S rRNA genes, the results indicated that between floods and ebbs, the community composition of bacteria and eukaryotes differed significantly, the alpha diversity of bacteria and eukaryotes differed significantly, with floods harboring higher diversity. The analysis of RDA suggested that salinity and TOC were important in explaining community variation in both bacteria and eukaryotes. Moreover, the co-occurrence networks between bacteria and eukaryotes showed higher negative relationships in ebbs (83.87%) than in floods (64.29%), suggesting increased interactions between bacteria and eukaryotes during ebbs as the water was incubated in the bay. These findings demonstrated the dynamics of biogeochemical processes of nutrients and plankton communities in the shallow bay and tidal cycles are a dominant driving force in regulating variability in phytoplankton and bacterial community and the sediment-water interface exchange. The results indicate that we should not overlook at the importance of shallow water column fringing the shore lines.

Spatial distribution and partition of polycyclic aromatic hydrocarbons (PAHs) in the water and sediment of the southern Bohai Sea: Yellow River and PAH property influences

The marginal Bohai Sea, connected to the northwestern Pacific Ocean, is threatened by human activity. The Yellow River, the second largest river in China, drains large amounts of water, silts, and polycyclic aromatic hydrocarbons (PAHs) into the southern Bohai Sea; however, to what extent the Yellow River inputs influence the spatial distributions and partitions of PAHs in the southern Bohai Sea is not well known. Therefore, this study collected surface water, bottom water, and sediment samples from the southern Bohai Sea and analyzed them to examine the spatial distributions and partitions of 15 priority PAHs. The results showed that PAH concentrations ranged from 26.9 to 50.1 ng L–1 in surface water, 18.8 to 44.1 ng L–1 in bottom water, and 7.4 to 143.9 ng g–1 in sediment, with higher proportions of four-, five-, and six-ring PAHs in sediment than in water. PAH inputs from the Yellow River and sea coastal currents determined the spatial distribution of PAH concentrations in water and sediment, with an overall decrease from the estuary to the southeast. However, the solid dilution effect of input silts from the Yellow River and the liquid dilution effect of water from the Yellow River and Yellow Sea led to lower PAH concentrations in the water and sediment of the southern Bohai Sea than those in other areas of the Bohai Sea. PAH exchange between the atmosphere and seawater led to significantly higher individual PAH concentrations (except for acenaphthylene) in the surface water than in the bottom water, with ratios significantly related to the PAH n-octanol-water partition coefficient, organic carbon-water partition coefficient, and Henry's law constants. These parameters also determined PAH partitioning between the bottom water and sediment. Individual and total PAH concentrations in the sediment were significantly correlated with organic matter, clay, and silt contents. Therefore, the partitions and spatial distributions of PAHs in the southern Bohai Sea comprehensively depend on PAH properties, PAH inputs from the Yellow River and the atmosphere, sea currents, and seawater and sediment properties. The ecological risks posed by individual PAHs in both water and sediment were negligible or acceptable.