Quality Standards For Surface Water Research Articles

Fabrication of FeCu/CC Composite for Efficient Removal of Nitrate for Aqueous Solution Via Electrochemical Reduction Process

AbstractThe electrochemical nitrate reduction (ENR) for the conversion of nitrate to nitrogen gas is a significant strategy to remediate the eutrophication in surface water. However, the exploitations and practical applications of suitable electrocatalysts still face great challenges. In this study, FeCu bimetal microparticles were deposited onto surface of carbon cloth (CC) to fabricate the FeCu/CC electrocatalyst for the removal of nitrate. Among obtained catalysts, the sample with Fe/Cu molar ratio of 1 : 15 (Fe1Cu15/CC) exhibits the excellent electroreduction efficiency for nitrate removal (R(NO3−), >90 %) but an ineffective selectivity of N2 formation (S(N2), ~23 %). After the anchor of reduced graphite oxide (rGO) to surface of Fe1Cu15/CC, at the optimized condition without the assistance of chlorine oxidation, R(NO3−) and S(N2) of rGO/Fe1Cu15/CC catalyst reach 94.2 % and 72.8 %. After 5 day endurance test, the values of R(NO3−) and S(N2) are still 82.9 % and 62.8 %, demonstrating the promising durability of this catalyst electrode. Meanwhile, the potential application of rGO/Fe1Cu15/CC was explored for the treatment of simulated wastewater discharged by urban wastewater treatment plant, the concentration of total nitrogen (TN) decreases from 15–1.17 mg/L, and this value is lower than TN threshold limit in Class IV of Chinese surface water quality standard.

Tracing nitrogen sources and transformation characteristics in a large basin with spatially heterogeneous pollution distribution

This study used dual stable isotopes to examine nitrate sources and geographical distribution in the Liao River Basin (LRB), one of China's seven major river basins. During a normal hydrological season in April 2021, water samples were taken from the main streams of the Liao River (MLR), Shuangtaizi River (STR), Hun River (HR), Taizi River (TZR), and Daliao River (DLR). Monitoring results indicated that 93% of the water samples had a total nitrogen level exceeding the Class IV limit (1.5 mg/L) of the ‘Environmental Quality Standards (EQS) for surface water’, indicating a serious nitrogen pollution status. 71.3% of the total nitrogen on average was in the form of nitrate. The scatterplots of δD-H2O and δ18O-H2O showed that water in TZR and DLR were mainly affected by precipitation, while MLR, STR and HR were additionally impacted by evaporation and groundwater. The overall δ15N and δ18O of NO3− varied from 7.7‰ to 17.9‰ and 0.6‰–11.2‰, respectively. The correlations between δ15N-NO3- and δ18O-NO3-, along with attribution results from the Bayesian isotopic mixing model, indicated a predominant role of manure/sewage (MS) pollution in affecting river nitrate, accounting for 78% of total nitrate in MLR and 72% in DLR. A positive correlation between δ15N-NO3- and δ18O-NO3- in MLR indicated the occurrence of denitrification process. Overall, attribution results showed that the primary nitrate sources varied in different river systems within such a large basin, mainly due to spatially varied land use and human activities. Tailored nitrogen management strategies should be implemented to address the main anthropogenic pressures.

Pollution characteristics of heavy metals, antibiotic and antibiotic resistance genes in the crested ibis and their habitat across different lifestyle and geography

Antibacterial resistance in wild animals has been increasingly reported worldwide, even though they are usually not directly exposed to clinically relevant antibiotics. Crested ibis, one of the rarest birds in the world, usually forages in paddy fields and prefer to nest and breed near villages that is greatly influenced by anthropogenic activities. We sampled the feces of crested ibises, as well as their habitat environment samples, to explore the pollution characteristics of heavy metals, antibiotics and antibiotic resistance genes (ARGs). Results showed that the pollution characteristics of heavy metals, antibiotic, ARGs and gut microbiota of crested ibis were more related by host lifestyle and habitats. Captive ibises had higher relative abundances of the total ARGs and tetracycline concentrations compared with feralization and wild ibises, while the heavy metal contents had shown the opposite result. The Characteristics of pollutants in the corresponding environmental samples also exhibited high similarity with the results of fecal samples. The relative abundances of Proteobacteria and Actinobacteria were significantly different between captive and wild individuals, while the abundance of majority bacterial genera was generally higher in wild populations. The concentrations of heavy metals in soil (Cd, Cu and Zn) and water (Cd, Cu, Zn and Cr) were both exceeded the background soil levels or surface water quality standards, suggesting multi-element contamination in the habitat. Ecological risk assessments of soils by Igeo and Er showed that the habitats of wild ibises were heavily and moderately contaminated by Cd, which would possibly pose a threat to the health of ibises. PLS-PM analysis indicated that microbial compositions and residual antibiotics had the most substantial impact on the dynamic changes in ARGs of ibis. Overall, this work provides a comprehensive understanding of the characteristics, risks of those contaminations, and their effects on the ARGs in the habitat of crested ibis.

Analysis of the drought effects on the physicochemical and bacteriological quality of the Inaouene River water (Taza, Morocco)

The Inaouene basin's waters are deeply affected by pollution, which undermines their quality. Indeed, due to the increasing population and industrial development of Taza city, the Inaouene River and its tributaries Larbaa and Lahdar are currently at risk of large quantities of urban discharge, exacerbated by successive drought periods. The objective of this study was to determine the pollution levels and assess the impact of drought on the water quality of the Inaouene River, based on physicochemical, and bacteriological analyses at seven stations over two hydrological cycles (June 2020 to May 2022). The results of physicochemical analyses during the first hydrological cycle revealed averages of 15.93 °C for Temperature, 1434.43 µS cm-1 for electrical conductivity (EC), 0.93 and 0.63 mg L-1 respectively for total phosphorus (TP) and orthophosphate (PO43-), 9 mg L-1 for NTK, 134.23 and 278.43 mg L-1 for BOD5 and COD respectively, 3.99 mg L-1 for Dissolved oxygen (DO) and 203.59 mg L-1 for sulfate (SO42-). For water bacteriological quality, the total coliforms (TC), Escherichia coli (E. coli), and intestinal enterococcus (IE) have shown averages of 3.45, 2.96, and 2.73 Log10 MPN per 100 ml respectively. During the second hydrological cycle, marked by low rainfall, a pronounced degradation in water quality has been observed, affecting all parameters. Notably, water quality went from average to poor or very poor according to the Moroccan surface water quality standards (MSWQS) and from very poor to unsuitable for consumption for the Water Quality Index (WQI) during the drought period. This study confirmed the exacerbation of deterioration in the water quality of the Inaouene River during the drought period, notably evidenced by heightened concentrations of organic matter (increases of 41.53 % and 37.08 % for BOD5 and COD, respectively), fecal contaminants (elevations of 11.48 %, 10.18 %, and 14.7 % for IE, TC, and E. coli, respectively), nutrients (increases of 38.83 % for TP, 48.67 % for PO43-, and 35.82 % for NTK), and mineral content (augmentations of 28.89 % for EC, and 31.73 % for sulfate). Additionally, this degradation in quality is reflected in the elevation of water temperature and the reduction in oxygenation (of 9.39 % for Temperature, and 46,26 % for DO).

Health Risk Assessment of Heavy Metal(loid)s in the Overlying Water of Small Wetlands Based on Monte Carlo Simulation.

Heavy metal(loid) (HM) contamination is a significant threat to wetland ecosystem. However, contamination risks of HMs in overlying water of small wetlands, which are easily ignored because of their minor occupancy in an overall area, are nearly unknown. A total of 36 water samples containing six HMs were collected from the urban and rural small wetlands of Urumqi in China, and the contamination levels and probabilistic health risks caused by HMs were assessed using the Nemerow pollution index (NPI) and the health risk assessment model introduced by the US EPA. The results revealed that the average concentration of Hg in the urban and rural small wetlands surpassed the Class II thresholds of the Environmental Quality Standards for Surface Water (GB 3838-2002) by factors of 3.2 and 5.0 times, respectively. The overall contamination levels of HMs in the small wetlands fall into the high contamination level. Results of a health risk assessment indicated that non-carcinogenic health risk of the investigated HMs are found to be lower than the acceptable range for adults, but higher than the acceptable range for children. Meanwhile, As falls into the low carcinogenic risk level, whereas Cd falls into the very low carcinogenic risk level. Overall, HMs in rural small wetlands showed relatively higher contamination levels and probabilistic health risks than that of urban small wetlands. In addition, As was identified as the dominant health risk factor in the overlying water of small wetlands in the study area. Findings of this study provide scientific support needed for the prevention of HM contamination of small wetlands in arid zones.

Environmental implication identification on water quality variation and human health risk assessment in the middle and lower reaches of the Hanjiang River, China

As the longest tributary of the Yangtze River, the Hanjiang River has been a “lifeline” for the “Yangtze River Economic Belt of China”. The water quality of the middle and lower reaches of the Hanjiang River (MLHR) has received considerable attention due to environmental degradation, increasing population, and water diversion project operations during the past decade. In this study, 16 water quality parameters from 14 national water quality monitoring stations along the MLHR were collected monthly from January 2021 to December 2022. Water quality index (WQI) methods coupling multivariate statistical techniques, e.g., seasonal Mann-Kendall test (SKT) and Mantel’s test, were applied to analyze and evaluate the spatiotemporal variations of water quality under different environmental and hydrological conditions. The Hazard Quotients (HQs) were used to assess the non-carcinogenic and carcinogenic risk for adults and children via ingestion and dermal pathways. The results showed that the overall water quality in the MLHR was classified as “excellent”, with the average WQI higher than “91”, and each single water quality indicator met Class I or Class II surface water quality standards of China. Ammonia (NH3-N), Total phosphorus (TP), Permanganate (CODMn), pH, and Arsenic (As) were significantly correlated with water level variations. CODMn and TP were decisive in explaining the WQI variations of the MLHR. NH3-N, water temperature, pH, and dissolved oxygen were key parameters for explaining WQI variations in most regions of the MLHR. As, Cadmium (Cd), and Chromium (Cr) presented potential health risks in the MLHR and should warrant close monitoring due to their significant health implications. Due to the continuous construction and operation of cascade hydro-projects, the synchronous monitoring of water quality and hydrological data of the MLHR should be conducted in the future. This study provides a scientific reference for managing water quality in the MLHR and similar natural riverine water bodies.

Occurrence, transport and sources of metals and metalloids in the Bangpakong River in the eastern economic corridor area of Thailand

The occurrence of elements in river water is affected by various factors, including mobility, weathering and transport processes and anthropogenic contributions. A total of six water sampling campaigns were conducted from 2021 to 2022 to study the factors affecting the occurrence of twelve elements (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn and Se) in the Bangpakong River. The total concentrations of all the elements were within the levels set by the national surface water quality standard. Comparisons of dissolved elemental concentrations in the study area with the global average for dissolved elemental concentrations in pristine rivers indicated contamination with Al, As, Co, Mn, Zn and Se in the river water. Based on the percentage of each element in particulates to the total concentration, Al (80.6 %), Cr (71.9 %), Cu (69.9 %), Fe (95.6 %), Mn (76.6 %), Pb (74.7 %), and Zn (70.6 %) were mainly transported in the particulate phase in both the dry and wet seasons. However, As (65.5 %), Co (60.3 %), and Se (77.6 %) were mainly transported in the dissolved phase in both seasons. The ratios of the dissolved Se concentration in river water to the Se concentration in the Earth's crust indicated significant and high mobility, especially in downstream sites, likely due to Se leaching from alluvial sediments. Seawater intrusion is likely the cause of As and Zn contamination in the dry season. Weathering of rocks and soils likely causes Al, Co, and Mn contamination in the wet season. The anthropogenic sources of contamination include the discharge of Mn and Zn from fertilizers in agriculture and the use of formulated feed in aquaculture. Approximately 52.98, 25.23, 5.68 and 0.63 tons of Fe, Al, Mn and Zn, respectively, are estimated to be transported from the river into the Gulf of Thailand each year.

Water quality evaluation based on water quality index and multiple linear regression: A research on Hanyuan Lake in southern Sichuan Province, China.

This study aims to understand the changes in the water quality of Hanyuan Lake and to show these changes over time. In this study, monthly sampling was conducted at three sampling sites in Hanyuan Lake, and water samples were measured for water quality indicators in the laboratory according to the methods specified in the Environmental Quality Standards for Surface Water (GB3838-2002). Based on the monitoring data from January to December 2019, the WQI comprehensive evaluation method was used to conduct multiple linear stepwise regression analysis, extract key indicators, and establish the WQImin model. The results show that according to the WQI comprehensive evaluation method, the WQI values of Hanyuan Lake are all above 90, and the grade is excellent. The overall water quality of Hanyuan Lake is excellent, and most of the water quality indexes reach the Class I standard in the Environmental Quality Standards for Surface Water (GB3838-2002). WQImin1 (R2 = 0.86, p < 0.001, PE = 4.28) as the best WQImin model. In this study, a model with fewer parameters was established by multiple linear regression method, which is conducive to better monitoring of water quality at monitoring stations while saving costs. PRACTITIONER POINTS: According to the WQI comprehensive evaluation method, the WQI values of Hanyuan Lake are all above 90, the rating is excellent. From January 2019 to September 2020, the monthly change trend of each section is roughly the same, showing a trend of first decreasing, then rising, then decreasing, and finally rising and flattening. The WQImin model was developed to completely describe the change in the water body.

An investigation of cyanobacteria, cyanotoxins and environmental variables in selected drinking water treatment plants in New Jersey

Harmful Algal Blooms (HAB) have the potential to impact human health primarily through their possible cyanotoxins production. While conventional water treatments can result in the removal of unlysed cyanobacterial cells and low levels of cyanotoxins, during severe HAB events, cyanotoxins can break through and can be present in the treated water due to a lack of adequate toxin treatment. The objectives of this study were to assess the HAB conditions in drinking water sources in New Jersey and investigate relationships between environmental variables and cyanobacterial communities in these drinking water sources. Source water samples were collected monthly from May to October 2019 and analyzed for phytoplankton and cyanobacterial cell densities, microcystins, cylindrospermopsin, Microcystis 16S rRNA gene, microcystin-producing mcyB gene, Raphidiopsis raciborskii-specific rpoC1 gene, and cylindrospermopsin-producing pks gene. Water quality parameters included water temperature, pH, dissolved oxygen, specific conductance, fluorescence of phycocyanin and chlorophyll, chlorophyll-a, total suspended solids, total dissolved solids, dissolved organic carbon, total nitrogen, ammonia, and total phosphorus. In addition to source waters, microcystins and cylindrospermopsin were analyzed for treated waters. The results showed all five selected New Jersey source waters had high total phosphorus concentrations that exceeded the established New Jersey Surface Water Quality Standards for lakes and rivers. Commonly found cyanobacteria were identified, such as Microcystis and Dolichospermum. Site E was the site most susceptible to HABs with significantly greater HAB variables, such as extracted phycocyanin, fluorescence of phycocyanin, cyanobacterial cell density, microcystins, and Microcystis 16S rRNA gene. All treated waters were undetected with microcystins, indicating treatment processes were effective at removing toxins from source waters. Results also showed that phycocyanin values had a significantly positive relationship with microcystin concentration, copies of Microcystis 16S rRNA and microcystin-producing mcyB genes, suggesting these values can be used as a proxy for HAB monitoring. This study suggests that drinking water sources in New Jersey are vulnerable to forthcoming HAB. Monitoring and management of source waters is crucial to help safeguard public health.

Promising membrane photobioreactor for continuous flow treatment of Low C/N wastewater: Treating process, community structure, and cooperation mechanism

Low carbon/nitrogen (C/N) wastewater treatment is an emerging issue for conventional treatment technologies. To achieve this goal, a novel membrane photobioreactor (MPBR), integrating microalgae consortium (MC) and activated sludge (AS) phases, was investigated. The separation of the MC and AS phases could improve the removal of pollutants in low C/N wastewater, which could achieve the rapid denitrogenation through NH4+-N assimilation in MC phase, and effectively reduce organic matter concentration in AS phase, resulting in better nutrient recovery, lower costs, and stable pH. The results in phase I showed that the pollutants, such as chemical oxygen demand (COD), ammonium (NH4+-N), and total phosphorus (TP), met the Environmental Quality Standards for Surface Water (GB3838–2002) by MPBR. The AS phase with low DO, which could enrich heterotrophic bacteria (e.g., Bacteroidetes vadinHA17, Spirochaeta and Ahniella) and nitrogen cycling bacteria (e.g., Mycobacterium, Bacillus and Ellin6067), could promote the removal of COD and NO3--N in the continuous effluent. Based on the co-occurrence pattern analysis, the main influencing factor of MC and AS phases was the reduction of COD, which also illustrated the synergistic removal of organic matter by the cooperative interaction of microalgae and heterotrophic bacteria. From a genetic perspective, the internal circulation mode also enhanced microbial nitrogen metabolism in the MPBRs, with higher abundances of nitrification- and denitrification-related functional genes in the MC phase, and higher abundances of nitrification, dissimilatory nitrate reduction, and denitrification genes in the AS phase. This study provided an experimental and theoretical basis for MPBR in low-C/N wastewater treatment.

Physio-biochemical characteristics of Acrostichum aureum L. In the coir retting areas of Kadinamkulam Estuary, South India

The Kadinamkulam lake a temporary estuary lying in the southern part of Kerala, is the largest of its kind in Thiruvananthapuram district, Kerala. Connected with the Anchuthengu kayal on the north and the Veli kayal on the south, the north and the Veli kayal on the south, the Kadinamkulam kayal remains connected with the Lakshadweep Sea for varying periods depending on rain fall and river discharge. Acrostichum aureum L. is only pteridophyte genus fern in the mangrove ecosystem of Indian coast. So the present study was conducted in the plant Acrostichum aureum L. identified in the selected stations of Kadinamkulam estuary. The major objective of the study is to assess the changes in the physiological and biochemical characteristics of the plant Acrostichum aureum L in coir retting areas. For this, surface water samples and plant samples were collected from the six selected stations of the coir retting areas and one station in the non-retting area of Kadinamkulam estuary. The results show reduction in leaf pigments, total proteins, carbohydrates in the Acrostichum aureum L. plants in polluted stations compared to that of control station/non retting area. The malondialdehyde, antioxidants and proline were increased in the Acrostichum aureum plants in retting stations and it vividly points out the stressful environment in the study area. It may be due to the presence of pollutants in the coir retting effluents and sewage disposed to this lake. The results of the study in lake water samples show that the values of some water quality parameters in coir retting areas were above the permissible limits of surface water quality standards.

Biochar accelerated Fenton process for roxarsone oxidation, inorganic arsenic adsorption and simultaneous immobilization of arsenic-iron sludge

Complete remediation of organoarsenics from environmental matrix hits the bottleneck, that is, the sluggish efficiency of oxidative degradation towards organoarsenics and unsatisfying immobilization performance towards generated inorganic arsenic. Herein, we establish a biochar accelerated Fenton (BA-Fenton) process to decontaminate water from roxarsone (ROX). In comparison with Fe2+/H2O2 process (10 μΜ/0.2 mM), the incorporation of 0.5 g L-1 biochar promoted ROX degradation from 48.2% to 98.2% and total arsenic elimination from 67.6% to 97.3%, respectively. In BA-Fenton process, •OH as the dominant reactive oxygen species (ROS), exhibited a cumulative concentration of 0.42 mM, three times higher than that in classical Fenton process. Crucially, the presence of biochar in Fenton process significantly enhanced the stability of arsenic-iron sludge, whereas the secondary leaching of total arsenic decreased from 433.8 μg-As L-1 to 13.9 μg-As L-1, meeting the prescribed environmental quality standards for surface water in China (50 μg-As L-1, GB 3838-2002). Mechanistic studies unveiled ROX remediation mechanism by BA-Fenton process, highlighting the dual functionality of biochar. On one hand, biochar efficiently reduced Fe3+ to Fe2+ with a rate constant of 0.225 min-1, overcoming the rate-determining step of classical Fenton process for •OH production, consequently promoting the transformation of ROX to As(V). On the other hand, molecular spectroscopy analysis elucidated that in-situ formed As(V) was adsorbed by ferric hydroxides with the formation of arsenic-iron sludge. Subsequently, biochar immobilized arsenic-iron sludge through hydrogen bonds, electrostatic attraction and surface complexation. Furthermore, real water studies demonstrated the effective remediation of organoarsenics by BA-Fenton process in tap water, lake water and chicken manure leachate. This “Two Birds with One Stone” strategy with low-cost, environmental-friendly and sustainable biochar holds great promise for the ultimate disposal of industrial wastewater containing organoarsenics.

Highly stable removal of low concentration phosphorus by mechanically activated FeCO3: In situ synergistic mechanisms

Excess phosphorus (P) in surface water poses a serious threat to ecological safety. However, current methods for effectively removing low concentrations of phosphorus are complicated and expensive. Herein, we used one-step mechanical activation to enhance the release of alkalinity from carbonates and to stimulate ferrous activity in situ, thus achieving efficient and stable removal of phosphorus at low concentrations. The resultant activated FeCO3 was demonstrated to be a high-performance material, which can remove more than 92 % of the actual low concentration of phosphorus pollution within 30 min, and the concentration of the effluent steadily met the requirements of Chinese Class I environmental quality standards for surface water (0.02 mg/L). In addition, mechanistic investigation showed that mechanical activation significantly enhanced the reactivity and phosphorus removal performance of MgCO3. Moreover, one-step mechanical activation simultaneously stimulates the release of alkaline and ferrous ionic groups from iron-rich FeCO3, which can produce highly active trivalent iron oxides in situ, leading to efficient and stable phosphorus removal at low concentrations. The present work provides a new insight and direction for developing high-performance materials to remediate low concentration phosphorus polluted waters.

Water Resource Impacts of Irrigation: The Case of the Main Irrigation Canal from the M’Pourie Plain to Rosso in Mauritania

An important factor in determining agricultural production is the availability of irrigation water in the main canal of the M’Pourie plain. This factor affects both the intensification of crops and the size of the irrigation areas. The main Senegal River canal in Rosso, Mauritania, runs across the Plaine of M’Pourie. This study aims to assess the physicochemical quality of the water used for irrigation and agriculture in the main irrigation canal on the M’Pourie plain. The measurements were made from 2021 to 2022, and the following physical and chemical parameters were monitored: pH, temperature, electrical conductivity, salt content, calcium, magnesium, sodium, and potassium; ammonium bicarbonate; chloride; nitrite; nitrate; nitrogen; sulfate; and sodium adsorption ratio (SAR). These measurements were analyzed using volumetric, spectroscopic, and spectrophotometric methods. After conducting statistical analysis and comparing the results with Moroccan quality standards for surface water utilized in irrigation, it has been discovered that the average pH value is 7.51, indicating a neutral state. However, the average nitrite and ammonium values exceed Moroccan standards at 5.16 mg.L-1 and 0.41 mg.L-1, respectively. The water’s low mineralization is attributed to its low electrical conductivity, with an average of 52.2 μS.cm-1. Based on the analysis of the Senegal River water used for irrigation in the M’Pourie plain, it has been determined that its sodium adsorption ratio and electrical conductivity classify it as belonging to class C1S1. This indicates that the water has low salinity and is excellent for irrigation, with a low risk of alkalinization.

Use of water quality parameters to assess the ecological health of Atlantic coastal areas in the northwestern Morocco

Coastal waters are confronted with multiple stressors, including chemical contamination/pollution and climate change. Water quality along the Atlantic coast of Morocco was assessed, in this study, at six stations over four seasons, including three heavily industrialized stations (S2, S4, and S6) and three clean stations (S1, S3, and S5), spreading over a distance of ∼300 km from Azemmour to Essaouira cities. The physicochemical characteristics (temperature, salinity, pH, dissolved oxygen, suspended matter, and sulfate), and chlorophyll-a, as well as nutrients (nitrite, nitrate, ammonium, total phosphorus, orthophosphate, and silicate) were analyzed to investigate their spatial and seasonal trends in the study areas. The results revealed significant spatiotemporal variations in the distribution of the hydrological characteristics across the sampling sites. In addition, the observed sulfate and nutrient concentrations showed significant spatial and seasonal differences. The disturbed stations showed the highest concentrations of nutrients, while the clean stations exhibited the highest concentrations of chlorophyll-a, particularly in the spring season. As expected, the compressive pollution index (CPI) and water pollution index (WPi) results supported the pollution status of stations. Accordingly, the surface seawater quality was better in the clean stations compared to the polluted stations. According to the CPI and WPi values, the sampling stations were classified in the following descending order of pollution, from strongly and moderately polluted stations to slightly or unpolluted stations (S4 > S2 > S6 > S1> S3 > S5). The total phosphorus, orthophosphate, sulfate, and chlorophyll-a concentrations were substantially higher than the surface water quality standards of Morocco, especially at the most industrialized stations in the winter.The physicochemical, biological, and nutrient data obtained in this study provide a valuable reference for assessing the ecological quality status of the Atlantic coastal environments in the study areas.

Review on mechanism and remediation strategies of dissolved oxygen abnormal in surface water.

Dissolved oxygen (DO) is an important index to evaluate the quality of surface water environments. In recent years, anomalies in DO level have emerged as a major contributor to the decline of surface water quality. These anomalies have triggered several ecological and environmental challenges such as biodiversity loss, the degradation of water environmental quality, intensification of eutrophication, and an exacerbation of the greenhouse effect. Understanding the mechanisms underlying DO anomalies and devising targeted remediation strategies holds paramount importance in the scientific pursuit of water pollution control and aquatic ecosystem restoration. We explored and summarized the fluctuations and abnormal mechanism of DO concentration in surface water, focusing on factors like oxygen solubility, reoxygenation rates, and oxygen consumption by water bodies. We compiled a range of approaches for addressing DO anomalies, including pollution source management, artificial oxygenation, and the reconfiguration of aquatic ecosystems. Ultimately, we underscored the emerging significance of monitoring and regulating DO level in surface waters. Future research in this realm should encompass the establishment of distinct quality standards for surface water, the development of a comprehensive real-time spatial monitoring system for DO levels across watersheds, and the formulation of standardized procedures and technical norms.

Chemical characteristics, distribution patterns, and source apportionment of particulate elements and inorganic ions in snowpack in Harbin, China

Snowpack, which serves as a natural archive of atmospheric deposition of multiple pollutants, is a practical environmental media that can be used for assessing atmospheric records and input of the pollutants to the surface environments and ecosystems. A total of 29 snowpack samples were collected at 20 sampling sites covering three different functional areas of a major city (Harbin) in Northeast China. Two samples at the “snow layer” and one or two samples at the “particulate layer” were collected at each sampling site in the industrial areas characterized by multi-layer snowpack, and only one sample at the “snow layer” was collected at each sampling site in the cultural and recreational as well as agricultural areas. The snow contents of 31 elements (Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Y, Cd, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Pb) and six major water-soluble inorganic ions (WSIIs, NH4+, K+, Ca2+, NO2−, NO3−, and SO42−) were analyzed. The total mass of the measured elements is dominated (95.8%–99.2%) by crustal elements. Heavy metals only account for 0.77%–4.07% of the total mass of the elements, but are occasionally close to or even above the standard limit in the “Environmental Quality Standards for Surface Water” of China (GB3838-2002). SO42− and Ca2+ are the main anion and cation, accounting for 34.9%–81.1% and 1.43%–29.9%, respectively, of the measured total ions. Total atmospheric deposition of crustal elements and heavy metals is dominated by wet deposition in areas near the petrochemical plant and by dry deposition in areas near the cement plant. Coal combustion, industrial emissions, and traffic-related activities lead to the enrichment of heavy metals in the snowpacks of urban and suburban areas, while coal combustion and biomass burning contribute to pollution in rural areas. The cities and regions situated in the western, northwestern, northern, and northeastern directions from Harbin are potential source regions of these pollutant species.

Rapid and clean dewatering of dredged sediment via coupling of a two-step flocculation and geotextile filtration

The use of flocculation processes coupled with geotextile technology for dredged sediment dewatering is promising in recent years. However, two main issues are encountered: firstly, the occurrence of clogging resulting in reduced dewatering rate, and secondly, contamination of the residual water, necessitating additional treatment, consequently leading to an increase in operational costs. Therefore, this study proposed an innovative approach employing a two-step flocculation combined with geotextile filtration method to achieve rapid and clean dewatering of dredged sediment. The jar test implementation of a two-step flocculation process at the optimal flocculation dosages resulted in a dewatering rate that was about 16.7 times compared to commercial flocculant (APAM) conditioning. The increased dewatering rate is mainly attributed to the formation of large and compact flocs aggregates (d50 > 160 μm) formed through the two-step flocculation. These aggregates facilitate the formation of a filter cake with a high porosity of 45 %, a low tortuosity of 1.53, a uniform pore-throat structure, and excellent connectivity of pore space. Compared with APAM, the value of turbidity, COD, NH4+-N, and phosphorus in the residual water can be decreased from 36.4 to 3.8 NTU, 28.6 to 8.3 mg/L, 2.3 to 1.6 mg/L, 0.15 to 0.04 mg/L, respectively, which meet the environmental quality standards for surface water (type V) in China. In addition, the technology is proven to be economical as the cost of flocculants is less than half the cost of other reported flocculants. Overall, this work presents a new and cost-effective approach for achieving both rapid and clean dewatering of dredged sediments, which is very promising for practical applications.

Research on Advanced Treatment Technology of Fluorine Containing Wastewater from Graphite Production

With the gradual improvement of environmental emission requirements in China, the graphite industry is facing environmental pressure from advanced treatment. This article first conducted a study on the current status of advanced treatment technology for fluorinated wastewater. Subsequently, a single defluorination agent experiment was conducted, and it was found that compared to several agents used in the experiment, such as PAC, PAFS, and CaCl2, PAC had the best defluorination effect. The optimization of PAC conditions showed that its optimal reaction pH was 7, and equilibrium could be achieved after 3 minutes of reaction. The study also conducted orthogonal experiments with mixed salts, and the best conditions for the combination of fluoride removal agents were found to be PAC adding 400 mg/L, CaCl2 adding 400 mg/L, PAFS adding 200 mg/L, which can remove fluoride to 0.92 mg/L, below 1 mg/L, meeting the Class III water standard in the " Environmental quality standards for surface water ".The SEM image of the sludge generated by the reaction between the composite fluoride removal agent and fluoride containing wastewater shows a larger particle size of up to 50 μm which is beneficial for the separation and removal of sludge. The generated sediment sludge is mainly composed of Al, Fe, Ca, O, and Si according to EDS results, and belongs to general industrial solid waste.

Crab-Aquatic Plant System: A Model for Taking Ecological and Economical Care of the Lakes in Yellow River Delta, China

The lakes, including reservoirs and ponds in the Yellow River Delta, are characterized by many fragile ecosystems and low economic values. How to take into account both ecology restoration and the economic benefits of the lakes in this region is a complex problem. The Chinese mitten crab (Eriocheir sinensis)-aquatic plant system may have this potential. In this study, we planted aquatic plants, e.g., Elodea nuttallii, Hydrilla verticillate, and Vallisneria natans, with the crabs and investigated geochemical parameters in the ponds. The concentration of NH4+-N was lower than 0.5 mg/L, the pH of the breeding peiponds was 8.274-9.365, and the dissolved oxygen was 3.554-6.048mg/L, which was better than the class II environmental quality standards for surface water. The more extensive specifications ( &gt; 150g/pcs) of the crab growth with the aquatic plants account for &gt;35% of the total production. This model is significant to the ecological utilization of reservoirs in the Yellow River Delta but has low promotion. Therefore, some compulsory breeding policies and breeding standards must be proposed. It is the current ecological needs of the ecological protection Yellow River Delta.