Low Dissolved Oxygen Values Research Articles

Pengaruh Kualitas Air terhadap Keanekaragaman Plankton di Bozem: Analisis Parameter Fisik, Kimia, dan Biologi Ekosistem Perairan

Water quality plays an important role in maintaining the balance of aquatic ecosystems, including the abundance and diversity of plankton. This study aims to analyze the effect of various water quality parameters such as temperature, dissolved oxygen (DO), carbon dioxide (CO2) levels, Biochemical Oxygen Demand (BOD), pH, brightness, and turbidity on plankton diversity in Bozem. Data were obtained from eight observation stations with water quality parameter measurements and plankton sampling. The results showed that the water quality in Bozem was not optimal, with low DO values ​​(1.79 mg/L), high water temperatures (average 31.05°C), and low brightness (0.30 m), which contributed to the decline in plankton abundance. A total of 39 plankton genera were identified, with Synedra as the most dominant genus. Poor water quality inhibits plankton growth, which can impact the balance of the food chain in these waters. This study shows the importance of better water quality management to maintain the sustainability of aquatic ecosystems in Bozem. This study also contributes to the understanding of the multifactorial interactions between water quality parameters and plankton.

Impacts of horticultural environments on Rhinella arenarum (Anura, Bufonidae) populations: exploring genocytotoxic damage and demographic life history traits.

Horticulture poses a significant ecological risk, as agrochemicals are applied more frequently and in larger quantities per unit of production compared to extensive crop fields. The native amphibian Rhinella arenarum serves as a reliable bioindicator of environmental health. This study aimed to assess genocytotoxic damage and demographic life history traits of R. arenarum inhabiting horticultural environments. Sampling was conducted in suburban sites in central Argentina: H1 and H2 (sites associated with horticultural activity) and a reference site, RS. Environmental parameters were recorded, and the frequency of micronuclei (Mn), nuclear abnormalities (ENA), and indicators of cytotoxic damage were determined in tadpoles and adults. Demographic variables (age at maturity, longevity, potential reproductive lifespan, size at maturity, modal lifespan) were calculated. The highest nitrate and phosphate values, along with low dissolved oxygen values, were recorded at sites H1 and H2. Organisms inhabiting horticultural environments exhibited higher frequencies of Mn and ENA, surpassing those recorded in previous studies on tadpoles from sites with extensive crop production. Size at maturity and age at maturity of females, as well as size at maturity, longevity, mean age, and mean adult SVL of males, were lower in horticultural sites. The results support the hypothesis that anuran populations inhabiting horticultural environments demonstrate a diminished health status attributed to subpar environmental quality. Monitoring endpoints at different biological levels provides information on the ecotoxicological risk for amphibians and human populations inhabiting nearby areas.

Evolution of Water Quality in the Una-PE River Basin

The quality of aquatic ecosystems is a concern for society, since the interference of water bodies has been notorious, especially those that border large urban centers. Therefore, several parameters have been used to monitor water quality. In this way, the objective was to evaluate the quality of the waters of the Una River basin, Pernambuco, between the years 2001 and 2019. To this end, the values of water temperature (T), hydrogen potential (pH), dissolved oxygen (DO), biochemical oxygen demand (BOD), electrical conductivity (EC), total amount of phosphorus, turbidity and total rainfall volume, available in water quality monitoring reports from river basins from the state of Pernambuco. It can be seen that none of the verified variables showed normal behavior for the trained period. In this way, the tests proposed by Kruskal-Wallis and Nemenyi were used to evaluate the behavior of each parameter. The high values of T, EC, BOD, phosphorus concentrations and turbidity, together with the low DO values found at various times during the years analyzed, indicate an intrusion of sewage (domestic and/or industrial) into the aquatic ecosystem. After a statistical analysis of the indicators, it was concluded that it was not possible to identify improvements in the quality of water in the Una-PE River basin over the last 15 years.

Spatial modeling of physical and chemical parameters for the evaluation of the Río Puerta Grande stream in Mexico City

The Río Puerta Grande stream is in the Tarango micro-basin ravine in Mexico City and is considered environmental value area (EVA) due to its ecological importance. However, despite this, urban sewage is discharged into the stream. A physical, chemical, and biological characterization of its waters was realized in 2020 during the dry season and after the rainy season. As part of the analytical results, in situ and ex-situ parameter spatial distribution maps of seven sampling sites were obtained using ArcGIS software’s inverse distance weighted (IDW) interpolation tool. The variation in concentration for each parameter during the two seasons is shown on the maps, where red indicates the highest concentration and blue is the lowest. At the residual discharge sites, the concentration increased during the dry season; specific parameters in the period after the rainy season decreased due to a dilution effect, whereas others increased, such as fecal coliform, suspended solids, and biochemical oxygen demand (BOD). BOD revealed high concentrations during the dry season when it was influenced by urban discharge but decreased following the rainy season. Despite the low dissolved oxygen value between 4.39 and 3.80 mg/L, the stream does not currently show anoxia. Regarding the overall water quality index (WQI) during both periods, the stream’s water quality at all sites was “Highly contaminated,” according to Montoya et al. According to León-Dinius, the WQI was “Bad” in both seasons and in the period after the rainy season, it was deemed “Bad” and “Very bad”. The contaminants that should be considered as producing the most risk are organic matter (as reflected by BOD) and bacteriological pollutants.

Drivers behind the diversity and distribution of a widespread midwater narcomedusa

AbstractNarcomedusae play a key role as top‐down regulators in the midwater, the largest and most understudied biome on Earth. Here, we used ecological niche modeling in three‐dimensions (3D), ecomorphology, and phylogeny, to answer evolutionary and ecological questions about the widespread narcomedusan genus Solmissus. Our phylogenetic analyses confirmed that Solmissus incisa represents a complex of several cryptic species. Both the different genetic clades and tentacle morphotypes were widespread and often overlapped geographically‐ the main difference in their distribution and ecological niche being depth. This demonstrated the importance of including the third dimension when modeling the distribution of pelagic species. Contrary to our hypothesis, we found the modeled distribution of the Solmissus genus (n = 1444) and both tentacle morphotypes to be mostly driven by low dissolved oxygen values and a salinity of 34, and slightly by depth and temperature. Solmissus spp. were reproducing all year round, with specimens reproducing in slightly warmer waters (up to 1.25°C warmer). Our results suggest that Solmissus spp. will likely come out as climate change winners by expanding their distribution when facing ocean deoxygenation and by increasing their reproduction due to global warming. However, because most available midwater data comes from the northern Pacific, this sampling bias was undoubtedly reflected in the output of our ecological niche models, which should be assessed carefully. Our study illustrated the value of online databases including imagery and videography records, for studying midwater organisms and treating midwater biogeographic regions as 3D spaces.

Coupling of Carbon and Oxygen in the Pearl River Plume in Summer: Upwelling, Hypoxia, Reoxygenation and Enhanced Acidification

AbstractAcidification and hypoxia are universal environmental issues in coastal seas, especially in large river estuaries such as the Pearl River estuary. In July and August of 2015, two legs of a field survey were conducted in the Pearl River plume. Leg 1 was sampled during the influence of upwelling favorable winds, while Leg 2 was during downwelling favorable winds. During both legs, instead of the typically observed dissolved inorganic carbon (DIC) consumption and dissolved oxygen (DO) over‐saturation, upwelling‐induced high DIC (>2,000 μmol kg−1), low pH (7.7–7.8) and low DO (140–150 μmol kg−1) values were observed in surface waters at the estuary mouth and the area off Hong Kong. In the bottom waters, hypoxia, acidification (pH 7.6–7.8) and DIC accumulation (DIC addition of ∼100–180 μmol kg−1) were observed. Hypoxia was less severe during Leg 2 compared to Leg 1. The stoichiometry of oxygen depletion to DIC addition was 0.89 for bottom water, suggesting remineralization was dominated by marine sourced organic matter. However, a comparison of data from the two legs showed that the stoichiometry of oxygen consumption to DIC accumulation was significantly higher during Leg 2 (0.73 ± 0.03 for Leg 1 vs. 0.80 ± 0.05 for Leg 2), although N/P ratios were the same (13.54 ± 1.93 for Leg 1 vs. 13.51 ± 2.04 for Leg 2). This phenomenon was attributed mainly to enhanced ventilation (re‐oxygenation) under the influence of the downwelling favorable winds during Leg 2. Although ventilation relieves some hypoxia, it might enhance acidification in bottom waters after a short‐term ventilation event. The enhanced acidification after short‐term ventilation is worthy of further study considering that most hypoxia and acidification are found in shallow coastal seas.

Anthropogenic impact on environmental variables and macroinvertebrates community of River Eme, South-East, Nigeria

Macroinvertebrates are good bioindicators of water quality and ecosystem health and are often used to study anthropogenic effect on aquatic ecosystems. Consequently, some environmental variables and macroinvertebrates of Eme river were studied to understand the impact of human activities on this socio-economically important ecosystem. Six stations (reflecting different anthropogenic activities) along the reaches of the river were sampled and analyzed monthly from December, 2017 to November, 2018 using standard methods. The results showed that water temperature varied from 22.00, station 1 to 28.5oC, station 6, turbidity (0.50-9.40 NTU, station 4), flow velocity (0.21, station 1-0.85m/s, station 3), pH (4.30, station 2-6.30, station 1), electrical conductivity (45.20, station 2-168.40µS/cm, station 5), dissolved oxygen (1.60, station 4-6.10mg/l, stations 3 and 4), biochemical oxygen demand (0.80-4.30mg/l, station 4), nitrate (1.10, station 3-5.6mg/l, station 4) and phosphate (0.40, station 3-4.6mg/l, station 4). Flow velocity, electrical conductivity, biochemical oxygen demand, nitrate and phosphate varied significantly between stations (p<0.05). A total of 584 individuals from 5 taxonomic groups and 23 species of macroinvertebrates were recorded. Aquarius remigis was the most abundant species (8.7%). The macroinvertebrate community was dominated by tolerant and very tolerant species, such as Aquarius remigis, Caridina africana, Pseudocloen sp. nymph, Hydrometra sp and Belostoma sp. The dominance of tolerant species, high turbidity, biochemical oxygen demand, nitrate and phosphate values and low dissolved oxygen values are strong indications of anthropogenic effect. It is suggested that adequate management attention should be paid to the river in order to prevent further deterioration.

Spatiotemporal variations and influencing factors of river dissolved oxygen in Dongguan section of Dongjiang River, Pearl River Basin

溶解氧是水生生态系统健康程度的重要度量指标，研究溶解氧时空变化及其影响因素对揭示河流溶解氧动态过程和理解水体生物地球化学循环具有重要意义. 当前，许多河流均存在溶解氧偏低问题，严重影响河流水质. 基于此，收集了珠江流域东江(东莞段)上游桥头、中游樟村和下游沙田泗盛3个水质监测站的实测资料，采用折线图和箱型图分析溶解氧在月、季节和年际时间尺度下的变化规律及其空间差异; 采用最大信息系数、交叉小波转换和多元线性回归3种方法解析溶解氧时空变化的影响因素. 结果表明：空间分布上，溶解氧浓度从上游到下游逐渐降低，低值区分布在入海口处的沙田泗盛站，多年平均溶解氧浓度仅为3.11 mg/L. 时间变化上，2011—2019年溶解氧主要在11.64个月的周期下循环变化. 溶解氧展现出明显的季节性. 3个站点丰水期溶解氧浓度比枯水期分别降低1.68、2.03和1.77 mg/L. 驱动因素上，溶解氧的时空变化受到多个因素的综合作用. 桥头站和樟村站水质较好，水温是这两个站点溶解氧时空变化的主要影响因素. 其主要在8~16个月的周期上调控溶解氧变化，在两个站点分别可以解释溶解氧整体变化的70%和57%. 沙田泗盛站受多条支流汇入的影响，水体中硝化和氧化作用耗氧增强，加之悬浮物遮光效应，使得该处的溶解氧浓度降低.;Dissolved oxygen (DO) is a vital metric indicating aquatic ecosystem health. Exploring the spatiotemporal variations and influencing factors of DO is of great significance to reveal the river DO dynamics and to understand the river biogeochemical cycle. Presently many rivers have a problem of low DO, which seriously affects the river water quality. This study collected data of three water quality monitoring stations in the upper reaches of Qiaotou, the middle reaches of Zhangcun and the lower reaches of Shatiansisheng in Dongguan section of Dongjiang River, Pearl River Basin. The DO variations on monthly, seasonal and inter-annual timescales and corresponding spatial heterogeneity were analyzed using broken line and box diagrams. Influencing factors of DO variations were explored by three approaches including maximum information coefficient, cross wavelet transform and multiple linear regression. The results showed that DO concentration gradually decreased from upstream to downstream. The low DO values (3.11 mg/L) appeared in the Shatiansisheng station near the estuary. Temporally, DO changed in a cycle of 11.64 months from 2011 to 2019, exhibiting obvious seasonality. In wet seasons DO concentrations at three stations were 1.68, 2.03 and 1.77 mg/L lower than those in dry seasons, respectively. The water qualities of Qiaotou and Zhangcun stations were better. Water temperature was the main factor affecting the spatiotemporal variations of DO in these two stations. Water temperature regulated DO changes in a cycle of 8-16 months and accounted for 70% and 57% of the total DO changes at these two stations, respectively. Impacted by multiple tributaries inflows, nitrification and oxidation processes, oxygen demands were strengthened in Shatiansisheng station, coupled with the shading effect of suspended solids, resulting in a low DO concentration.

Sponge-like europium oxide from hollow carbon sphere as a template for an anode material for Reactive Blue 52 electrochemical degradation

The textile industry is one of the major pollutants of waterbodies with effluents high in biochemical and chemical oxygen demand values, high values of total dissolved solids, total suspended solids, and low dissolved oxygen values along with strong color. The existence of a successful method for its decontamination would be beneficial. In this work, we synthesized sponge-like europium oxide (Eu2O3) using a template-directed route from carbon hollow spheres, obtained from glucose as a carbon source. The material synthesis method was done in an aqueous environment, without using any organic solvents. Electrochemical properties of the synthesized material were investigated using cyclic voltammetry and electrical impedance spectroscopy, while morphological characterization was done using scanning electron microscopy and X-ray powder diffraction analysis. Eu2O3 were successfully immobilized at the surface of a screen-printed carbon electrode (Eu2O3/SPCE) using the drop-casting method. Finally, the prepared electrodes were tested toward the removal of Reactive Blue 52 (RB52) using electrochemical advanced oxidation processes (EAOPs). Important parameters, that is, the supporting electrolyte, its concentration, pH value, and the applied voltage, were optimized for RB52 degradation. The rate of removal was monitored spectrophotometrically and by high-performance liquid chromatography with a diode array detector (HPLC-DAD). It was found that the proposed approach reaches complete decolorization of the RB52 solution after a 60-min treatment, at pH 5.6 of KCl supporting electrolyte at a concentration of 0.05 M. Under optimal parameters, after 3 h of treatment, total organic carbon (TOC) was lowered by ~40%. The obtained results indicate that the proposed method may find potential application in EAOPs, considering electrode stability, durability, and efficiency and simplicity of the method.

Characterization of groundwater dynamics and contamination in an unconfined aquifer using isotope techniques to evaluate domestic supply in an urban area

In the urban area of Rio Cuarto groundwater is used for domestic supply. The objective of the current research was to investigate the water dynamics and nitrate contamination in an unconfined aquifer system of Rio Cuarto River basin. Stable isotopes of water (δ18O and δ2H) and nitrate (δ15N–NO3 and δ18O–NO3) were used and combined with conventional chemical techniques and mixing modelling approaches to determine the recharge areas and identify the main origin of nitrate pollution. More enriched water isotope values were recorded in Rio Cuarto city than in the piedmont and mountains indicating local recharge for well batteries 2 and 3. The well battery 1 and the infiltration gallery showed more negative isotopic values, demonstrating a strong influence by the recharge from the piedmont sector (impoverished groundwater). The δ15N–NO3 values and the Bayesian modeling showed that the dominant nitrate contamination source in the urban area is the on-site sanitation systems whereas in the peri-urban area nitrate contamination originates mostly from animal wastes. Both sources supply the aquifer with anthropogenic organic matter (>50%). The highest δ15N–NO3 values were correlated with low dissolved oxygen values, indicating the occurrence of denitrification processes in some places. High NO3 ions in the rural sector were attributed to the application of fertilizers and consequent nitrification processes. The samples from Rio Cuarto river located upstream of the Rio Cuarto City and close to the infiltration gallery showed the highest input from fertilizers (~40%), due to surrounding agricultural fields. The municipal well batteries showed good water quality (freshwater of low to extremely low nitrate concentration) which is linked to the high hydraulic conductivity of the aquifer that increases its capacity to dilute the contaminants. These results will be useful for local water administrators to improve water management.

Seasonal Variation on the Hydrochemistry and Height of Brackish-Water from Commodore Channel, Lagos, Nigeria

The current study deals with the evaluation of physicochemical characteristics, nutrient status, and variation in the height of surface water from the commodore channel, and its comparison with the hydrochemical characteristics of the monitoring borehole from the NIOMR Jetty, Lagos, Nigeria. We aim to further improve our understanding of the interrelationship of climate change and hydrological cycle, and its impacts in the Lagos coastal environments. The observed ranges of physicochemical characteristics of the surface water are dissolved oxygen (DO) 3.07-6.05mg/L; pH: 7.99-8.48; temperature 26.97-30.34°C, electrical conductivity (EC) 9680-47800mS/cm; salinity (Sal) 6.51-28.05‰ and water level 1.24-1.79m. The concentration of nutrient range from nitrite 10-36mg/l, nitrate 28-44mg/l, sulphate 38-90mg/l and phosphate 2-78mg/l. The analyzed hydrochemical characteristics from all the stations are within the desired values for healthy marine ecosystems when compared with Federal Ministry of Environment (FMENV) Nigeria permissible limits which are: DO >5 mg/l, pH 6.5-9, temperature <40°C, nitrite 1mg/l, nitrate 20mg/l, phosphate 5mg/l and sulphate 500mg/l; except low DO (<4.5mg/l) in January, November and December, and elevated nitrite, nitrate and phosphate values across the season. The low DO values may be attributed to enhanced transportation of non-biodegradable organic loads that utilize the available DO for chemical oxidation and microbial decomposition. While the enriched nitrite, nitrate and phosphate concentrations suggest enhanced productivity and influx of nutrients rich flood water from the anthropogenic source. Our study showed a coincidence in the highest brackish water height of the surface water (1.24m) from the commodore channel with the highest groundwater level (1.58m) in October. The lowest height of water levels was recorded in February and March at 2.23m and 1.79m for groundwater and surface water respectively. The similarities in the height of water levels were recorded with contrasting hydrochemical variables (e.g., high Ec vs. low Ec; and high Sal vs. low Sal), which confirmed the effect of rainfall/freshwater incursion on the surface water and simultaneous occurrence of subsurface pollution arising from seawater intrusion on the groundwater samples in October. This study had shown that a long term monitoring of rise in water levels and hydrochemical variables of surface and groundwater can be used to understand climate change and early warning predictions of flooding in coastal environments.

A soil microbial fuel cell-based biosensor for dissolved oxygen monitoring in water

Water pollution can cause significant depletions of dissolved oxygen (DO) in water systems with serious environmental and economic consequences. Online and continuous monitoring of DO can help prevent or minimise the risks associated with low DO values in water. Current DO sensors are, however, expensive and not suitable for continuous and autonomous in-field operation. In this study, we propose a novel and affordable Ceramic Soil Microbial Fuel Cell (CSMFC) for in situ, continuous and autonomous monitoring of DO in water. The system consists of a submersible ceramic vessel containing a soil-based anodic chamber, while the cathode, wrapped around the vessel, is used as the DO probe. The sensor signal, in terms of output voltage, correlates with the DO in water up to a saturating value of 4.5 ± 1.2 mg L−1, at a maximum voltage output of 321 ± 29 mV (20 ̊C, pH=7, 1.65 mS cm−1) with a sensitivity in the linear range of 53.3 ± 22.6 mV L mg−1. A factorial Design of Experiments (DoE) on pH, conductivity, DO and temperature, shows that the response of the sensor is mainly affected by temperature and DO, as well as by their mutual interaction. The calibration model is normalised by the output voltage baseline, thus accounting for any variability in performance, within the same device during long-term performance and from one device to another, which is a challenge in microbial-based systems. As such, this work not only reports an innovative microbial fuel cell-based DO sensor, but also demonstrates the necessity of a DoE to effectively calibrate the sensor.

Historical Changes in the Ecological Connectivity of the Seine River for Fish: A Focus on Physical and Chemical Barriers Since the Mid-19th Century

To understand the long-term fate of fish assemblages in the context of global change and to design efficient restoration measures in river management, it is essential to consider the historical component of these ecosystems. The human-impacted Seine River Basin is a relevant case that has experienced the extinction of diadromous fishes over the last two centuries and has recently witnessed the recolonization of some species. One key issue is to understand the historical evolution of habitat accessibility for these migratory species. Thanks to the unique availability of historical, mainly hand-written sources of multiple types (river engineering projects, navigation maps, paper-based databases on oxygen, etc.), we documented and integrated, in a geographic information system-based database, the changes to physical and chemical barriers in the Seine River from the sea to Paris for three time periods (1900s, 1970s, and 2010s). The potential impact of these changes on the runs of three migratory species that have different migratory behaviors—Atlantic salmon, allis shad, and sea lamprey—was evaluated by ecological connectivity modeling, using a least-cost approach that integrates distance, costs, and risks related to barriers. We found that accessibility was contrasted between species, emphasizing the crucial role of the migration type, period, and level of tolerance to low dissolved oxygen values. The highest disruption of ecological connectivity was visible in the 1970s, when the effects of large hypoxic areas were compounded by those of impassable navigation weirs (i.e., without fish passes). As the approach was able to reveal the relative contribution of physical and chemical barriers on overall functional connectivity, it may constitute a model work in assessing the functioning of large river ecosystems.

An improved process-based representation of stream solute transport in the soil and water assessment tools

Hydrological models have long been used to study the interactions between land, surface and groundwater systems, and to predict and manage water quantity and quality. The soil and water assessment tool (SWAT), a widely used hydrological model, can simulate various ecohydrological processes on land and subsequently route the water quality constituents through surface and subsurface waters. So far, in-stream solute transport algorithms of the SWAT model have only been minimally revised, even though it has been acknowledged that an improvement of in-stream process representation can contribute to better model performance with respect to water quality. In this study, we aim to incorporate a new and improved solute transport model into the SWAT model framework. The new process-based model was developed using in-stream process equations from two well established models—the One-dimensional Transport with Inflow and Storage model and the Enhanced Stream Water Quality Model. The modified SWAT model (Mir-SWAT) was tested for water quality predictions in a study watershed in Germany. Compared to the standard SWAT model, Mir-SWAT improved dissolved oxygen (DO) predictions by removing extreme low values of DO (<6 mg/L) simulated by SWAT. Phosphate concentration peaks were reduced during high flows and a better match of daily predicted and measured values was attained using the Mir-SWAT model (R2 = 0.17, NSE = −0.65, RSR = 1.29 with SWAT; R2 = 0.28, NSE = −0.04, RSR = 1.02 with Mir-SWAT). In addition, Mir-SWAT performed better than the SWAT model in terms of Chlorophyll-a content particularly during winter months, improving the NSE and RSR for monthly average Chl-a by 74 and 42%, respectively. With the new model improvements, we aim to increase confidence in the stream solute transport component of the model, improve the understanding of nutrient dynamics in the stream, and to extend the applicability of SWAT for reach-scale analysis and management.

Seasonal variations affect the physical and chemical parameters of inland waters: a case study of Warri River in Nigeria

&#x0D; &#x0D; &#x0D; &#x0D; The Niger-Delta area in Nigeria is rich with rivers, swamps and creeks that are often subject to various forms of pollution. The effect of seasonal variations on the physical and chemical conditions of Warri River was studied in 2015. Temperature and pH values across all seasons fell within the optimum range formost aquatic organisms. Meanwhile, total dissolved solids exceeded the World Health Organization (WHO) permissible limit, especially during the dry season; indicating possible pollution from inorganic salts, organic matter and other dissolved materials in the water. The low dissolved oxygen value recorded was expected due to the high levels of dissolved solids recorded in the river. Lastly, phosphate, nitrate and sulphate concentrations recorded were below the WHO permissible limits. The chemical and biological parameters recorded indicate that the Warri River poses minimal threat to human and animal life.&#x0D; &#x0D; &#x0D; &#x0D;

Spatial changes in water and heavy metal contamination in water and sediment of river Ganga in the river belt Haridwar to Kanpur.

Despite heavy investments and a number of government schemes, deterioration in water quality of river Ganga and its tributaries is an issue of serious concern. Among all the cities, thriving on Ganga, Kanpur is considered to add maximum pollution in the river. In the present study, water samples were collected seasonally from nine selected sites within the middle stretch of river Ganga from Haridwar to Kanpur. The velocity, temperature, pH, alkalinity, hardness, dissolved oxygen (DO), biological oxygen demand (BOD) and chemical oxygen demand (COD) were analyzed during winter (November-January), summer (March-June) and monsoon (July-September) season from November 2016 to September 2017 along with heavy metal analysis of water and sediment samples of the winter season. The levels of Cr, Cu, Cd and Pb were analyzed by atomic absorption spectrophotometer. Water quality was evaluated by water quality index (WQI) using BIS and WHO standards. The WQI values showed good water quality at Haridwar site (< 100) while it was very poor at other sites and Kanpur (> 100) which renders it highly unfit for human consumption and survival of some fish species because of low DO value (4.65 ± 1.08mgL-1) and high values of pH (8.82 ± 0.10), alkalinity (187.88 ± 8.88mgL-1), BOD (66.64 ± 2.19mgL-1) and COD (240.00 ± 17.33mgL-1). WQI showed highly unsuitable water quality at all sites except control site, of which S9 (Siddhanath Ghat) was highly polluted. Lead concentration was higher at Kannauj sites while high Cr was observed at Siddhanath Ghat (S9), Kanpur. The examined metals, such as Cr, Cu, and Pb, were far above the prescribed limits of various standards.

Performance Evaluation of Metakaolin as Low Cost Adsorbent for Manganese Removal in Anoxic Groundwater

The recent climate condition and pollution problem related to surface water have led to water scarcity in Malaysia. Huge amount of groundwater has been identified as viable source for drinking water. This paper was aimed to investigate groundwater’s quality at specific location and metakaolin’s potential in the groundwater treatment in the removal of manganese. Groundwater purging was determined to be sufficient at 120 minutes where all three parameters (pH, dissolved oxygen and conductivity) were stabilized. The groundwater studied is classified as both anoxic and reductive due the low dissolved oxygen value. It also can be categorized as brackish due to high value of conductivity and total dissolved solid. Manganese content in groundwater was determined as higher than of that permissible limit for raw water and drinking water which makes it unsuitable for them not suitable for consumption and cleaning purpose. Average manganese concentration in samples was 444.0 ppb where the concentrations of manganese ranged from 229.4 ppb to 760.3 ppb. Manganese developed is not that a strong positive correlation against iron concentration, total dissolved solids and conductivity; whereas has a moderate negative correlation against dissolved oxygen. The capability adsorption of manganese by metakaolin was assessed via batch method which indicated optimum dosage and contact time was 14g that removed average 30.2% and contact time optimum at 120 minutes which removed 33.2% manganese from the sample.

La degradación ambiental y sus efectos en la contaminación de las aguas superficiales en la cuenca del río Conchos (Chihuahua - México)

El desarrollo de las actividades humanas ha provocado un notable deterioro ambiental en la cuenca del río Conchos. La deforestación, los cambios de uso del suelo, el sobrepastoreo y la contaminación química de las aguas originada por las actividades agrícolas han contribuido a esta degradación, pero el principal factor de deterioro ambiental lo constituye la contaminación de las aguas superficiales provocada por los vertidos de aguas residuales urbanas y de desechos industriales. Los resultados más relevantes obtenidos en los análisis de agua ofrecen unos valores de oxígeno disuelto muy bajos, con niveles medios de 4.06 mg L-1. También se han constatado elevadas tasas de turbidez, que en algunos casos han superado los 980 NTU. El estudio concluye poniendo de manifiesto la necesidad de adoptar cambios sustanciales en los usos y prácticas agrícolas, y de reformar los sistemas de gestión integral relacionados con el tratamiento de los efluentes urbanos e industriales, con el fin de mejorar la calidad de las aguas y evitar posibles riesgos para la salud pública.

Nitrous oxide emissions from biofilm processes for wastewater treatment.

This paper discusses the microbial basis and the latest research on nitrous oxide (N2O) emissions from biofilms processes for wastewater treatment. Conditions that generally promote N2O formation in biofilms include (1) low DO values, or spatial DO transitions from high to low within the biofilm; (2) DO fluctuations within biofilm due to varying bulk DO concentrations or varying substrate concentrations; (3) conditions with high reaction rates, which lead to greater formation of intermediates, e.g., hydroxylamine (NH2OH) and nitrite (NO2-), that promote N2O formation; and (4) electron donor limitation for denitrification. Formation of N2O directly results from the activities of ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA), and heterotrophic denitrifying bacteria. More research is needed on the roles of AOA, comammox, and specialized denitrifying microorganisms. In nitrifying biofilms, higher bulk ammonia (NH3) concentrations, higher nitrite (NO2-) concentrations, lower dissolved oxygen (DO), and greater biofilm thicknesses result in higher N2O emissions. In denitrifying biofilms, N2O accumulates at low levels as an intermediate and at higher levels at the oxic/anoxic transition regions of the biofilms and where COD becomes limiting. N2O formed in the outer regions can be consumed in the inner regions if COD penetrates sufficiently. In membrane-aerated biofilms, where nitrification takes place in the inner, aerobic biofilm region, the exterior anoxic biofilm can serve as a N2O sink. Reactors that include variable aeration or air scouring, such as denitrifying filters, trickling filters, or rotating biological contactors (RBCs), can form peaks of N2O emissions during or following a scouring or aeration event. N2O emissions from biofilm processes depend on the microbial composition, biofilm thickness, substrate concentrations and variability, and reactor type and operation. Given the complexity and difficulty in quantifying many of these factors, it may be difficult to accurately predict emissions for full-scale treatment plants. However, a better understanding of the mechanisms and the impacts of process configurations can help minimize N2O emission from biofilm processes for wastewater treatment.

The temporal-spatial distribution and changes of dissolved oxygen in the Changjiang Estuary and its adjacent waters for the last 50 a

The Changjiang Estuary and its adjacent waters form one of the most important estuarine and coastal areas in China. Multi source and long-term data are assembled to examine the temporal-spatial distribution features of dissolved oxygen (DO) in the Changjiang Estuary and its adjacent waters for the past 50 a. The results show that the DO concentration in the surface of different seasons generally stays stable, while the DO concentration in winter displays a slight increase for the last 50 a. The DO average concentration in winter and spring varies from 7 to 11 mg/L, and in summer and autumn from 6 to 8 mg/L. Hypoxic values first appear in May, and low DO value plume can be observed on the bottom in spring along coastal areas of Zhejiang and Fujian Provinces, China. In summer, the plume advances northward, and the hypoxic intensity of northern transects is much higher than southern transects. Until autumn, hypoxia areas fade away little by little, and completely disappear in winter. Within last 50 a, hypoxia in the Changjiang Estuary and its adjacent waters starts to appear in the 1980s. Since 2000, the degree of hypoxia has increased seriously and the distribution depth has become smaller. It is performed based on a large amount of historical data, and the research results will be of great significance to further study on the dynamic development of hypoxia around the Changjiang Estuary.