Dissolved Oxygen Concentration Research Articles

Effect of Nitrification Inhibitors on Soil Nitrogen Dynamics and Microbial Community Structure in Aerated Paddy Field

The aim of this study was to clarify the effects of nitrification inhibitors on the dynamic changes in the nitrogen and microbial community in paddy soil under aerated irrigation by using the indica hybrid rice Zhongzheyou 8 as experimental material. A trial with three treatments was conducted in 2023： conventional flooding irrigation （CF）, micro-nano bubble water aeration irrigation （MB）, and micro-nano bubble water aeration irrigation combined with nitrification inhibitor （MBNI）. The effects of nitrification inhibitors on the contents of NH4+-N and NO3--N and the apparent nitrification rate of soil under aerated irrigation were analyzed, as well as the characteristics of bacterial community diversity and its correlation with soil chemical factors. The results showed that compared with those in the CF treatment, the MB and MBNI treatment significantly increased the dissolved oxygen concentration, oxidation-reduction potential, pH, and soil NH4+-N content. Compared with that under the MB treatment, the MBNI treatment increased soil pH, reduced NH4+-N content in a short time after nitrogen fertilizer application, and later increased NO3--N content. Compared with that in the CF treatment, the MB and MBNI treatments could increase the diversity and richness of soil bacteria, while the relative abundance of Proteobacteria and Nitrospirota significantly increased, and the relative abundance of Bacteroidota decreased. The MBNI treatment reduced the diversity and richness of bacteria compared with that in the MB treatment and significantly decreased the relative abundance of Nitrospirota. Correlation analysis showed that soil chemical properties were significantly correlated with bacterial community structure. In conclusion, the combined application of nitrification inhibitors under aerated irrigation can improve soil nitrogen supply capacity, increase soil inorganic nitrogen content, improve soil chemical properties, and affect microbial community diversity and richness to optimize microbial community structure.

Full-scale simultaneous partial nitrification, anammox, and denitrification for the efficient treatment of carbon and nitrogen in low-C/N wastewater

A full-scale simultaneous partial nitrification, anaerobic ammonia oxidation (anammox), and denitrification (SNAD) reactor was initiated to address the problem of high energy consumption for the treatment of low C/N wastewater. The SNAD system achieved a nitrogen removal rate of 0.9 kg/(m3·d) at an influent NH₄+–N concentration of 500 mg/L after 450 days of stable operation. Partial nitrification was achieved by maintaining free ammonia levels at 0.8 ± 0.3 mg/L and dissolved oxygen concentrations between 0.3 mg/L and 1.2 mg/L, which resulted in synergistic nitrogen removal, with anammox contributing 61 % and denitrification contributing 39 %. Microbiological analyses indicated that the dominant microorganisms were Candidatus Brocadia, Thauera, Denitratisoma, and Nitrosomonas. In conclusion, study provides a solid foundation for the broader implementation of the SNAD process in wastewater treatment systems.

Guidelines Assist Selection of Corrosion-Resistant Alloys for CCS and CCUS Injection Wells

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 217664, “Selection of Corrosion-Resistant Alloys for CCS and CCUS Injection Wells,” by Adam C. Rowe, SPE, Stress Engineering Services, and Bruce D. Craig, SPE, MetCorr. The paper has not been peer reviewed. _ Currently, few test data are available for determining the most suitable corrosion-resistant alloys (CRAs) for downhole injection equipment in carbon capture and storage (CCS) and carbon capture, use, and storage (CCUS) wells. The complete paper provides a guideline for such selections based on the composition of the CO2 stream, including impurities and the composition of the saline formation into which the CO2 will be injected. Introduction For those CCS and CCUS systems where water is expected to be present at some point, such as injection into a saline formation or by virtue of incomplete dehydration, carbon steel will corrode and CRAs must be considered. Because carbon steel pipelines are standard practice for transport of supercritical CO2 and have a long, successful history, this paper is strictly focused on the selection of CRAs for injection wells. While the selection of CRA material can be, and often is, based on common practices, each application requires an in-depth review of the complete system to determine the best materials for the job. In the case of storage, service life is ostensibly forever, so even otherwise minor pitting rates may not be tolerable in permanent equipment. The most important factors to consider for CRA corrosion are temperature, pH of the water phase, formation-water composition (typically chloride content), and stream impurities. With respect to temperature, this paper is focused on corrosion within CCS and CCUS wells and, therefore, considers only elevated temperature resulting from downhole geothermal gradients. Stream impurities have a significant effect on potential CRA selection, especially when certain species such as oxygen are present. However, hydrogen sulfide (H2S) and nitrogen and sulfur oxides also can be important to this selection. Technical Review of CCS and CCUS Injection Conditions Much of the CRA experience from the oil patch cannot be applied directly to CCS and CCUS well design. Multiple sources are susceptible to significant residual H2S in the injectate. Currently, no standards or guidelines exist relating to the effect of H2S in supercritical CO2 on materials. Therefore, the industry default at the time of writing is to apply the industry standard NACE MR0175/ISO 15156-3, though it is important to note that environmentally assisted cracking resistance has not been established for many CRAs at pH 3 and lower. It also is important to recognize that this standard is specifically applicable to production of oil and gas, and it remains to be determined whether CCS and CCUS operations are similar enough to apply this guide, or if supercritical CO2 warrants different limits, particularly when O2 is present. The presence of O2 in supercritical-CO2 streams presents a significant problem for the selection of CRAs. The corrosivity from O2 is defined by the dissolved oxygen concentration in the water phase, which is difficult to model in complex systems. Currently, these data are not readily available for supercritical-CO2 streams commingled with formation brines. As a guide, albeit a qualitative one, use of the pitting resistance equivalent number (PREN) is helpful for ranking resistance to pitting and crevice corrosion in aerated brine.

Effects of Mesoscale Eddies on Southern Ocean Biogeochemistry.

The Southern Ocean is rich in highly dynamic mesoscale eddies and substantially modulates global biogeochemical cycles. However, the overall surface and subsurface effects of eddies on the Southern Ocean biogeochemistry have not been quantified observationally at a large scale. Here, we co-locate eddies, identified in the Meta3.2DT satellite altimeter-based product, with biogeochemical Argo floats to determine the effects of eddies on the dissolved inorganic carbon (DIC), nitrate, and dissolved oxygen concentrations in the upper 1,500m of the ice-free Southern Ocean, as well as the eddy effects on the carbon fluxes in this region. DIC and nitrate concentrations are lower in anticyclonic eddies (AEs) and increased in cyclonic eddies (CEs), while dissolved oxygen anomalies switch signs above (CEs: positive, AEs: negative) and below the mixed layer (CEs: negative, AEs: positive). We attribute these anomalies primarily to eddy pumping (isopycnal heave), as well as eddy trapping for oxygen. Maximum anomalies in all tracers occur at greater depths in the subduction zone north of the Antarctic Circumpolar Current (ACC) compared to the upwelling region in the ACC, reflecting differences in background vertical structures. Eddy effects on air-sea exchange have significant seasonal variability, with additional outgassing in CEs in fall (physical process) and additional oceanic uptake in AEs and CEs in spring (biological and physical process). Integrated over the Southern Ocean, AEs contribute 0.01 Pg C (7 ) to the Southern Ocean carbon uptake, and CEs offset this by 0.01 Pg C (2 ). These findings underscore the importance of considering eddy impacts in observing networks and climate models.

Environmental DNA as a novel tool for monitoring fish community structure and diversity feature in the northern Antarctic Peninsula

The northern Antarctic Peninsula (NAP), one of the fastest warming area around the Southern Ocean, hosts a large variety of endemic fish and is influenced by complex hydrography. However, the dynamics of fish diversity kept unclear and without monitoring. Monitoring of environmental DNA (eDNA) is a noninvasive, ecofriendly, and accurate approach for detecting aquatic organisms, including fish. In this study, the fish composition and diversity were detected by high-throughput sequencing of eDNA for the first time in the NAP. Overall, 32 species (1 order, 6 families, and 25 genera) of fishes were detected in the environmental water samples from 18 stations around the NAP, in which number of fish species were similar in the Drake Passage and the northern shelf of the South Shetland Islands (DP-SSIs) and the Bransfield Strait (BS). Most of the fish species were identified in previous Antarctic fish surveys using conventional methods, which supports the applicability of eDNA-based survey. Moreover, Pogonophryne albipinna was detected firstly in the NAP. Among the identified fish species, Champsocephalus gunnari and Notothenia rossii had the highest abundance (45.04% and 27.59%, respectively). There was difference in fish composition between the DP-SSIs and BS stations, although alpha diversity indices did not differ. The dissolved oxygen content and water temperature were the main drivers for the differences in fish species composition between areas. Our results indicated that eDNA could be a rapid and accurate biomonitoring approach for the entire Southern Ocean, particularly in areas with difficult logistics, in the future.

무인자동 양식어류 급이공급 시스템 개발 및 검증

Unmanned automatic feeding systems are being actively distributed to automate land-based aquaculture farms. Currently, feed supply in aquaculture is primarily based on a fixed period and amount, depending on the predetermined feed quantity set by the operator, which does not consider the dynamic feed supply needs of fish. This can lead to under- or oversupply of feed, affecting the fish growth rate and water quality in aquaculture. To address this, a method is proposed in this paper to identify fish hunger levels using machine vision and predict the dissolved oxygen concentration in real time to prevent mass fish mortality due to water quality deterioration, even with additional feed supply. The method aims to verify its performance. Firstly, based on the observation that aquaculture farm operators estimate fish hunger levels by feeding time, a method is proposed to estimate hunger levels using machine vision and feeding time. Next, a combination of time series data decomposition model and pre-trained deep learning model is used to predict the dissolved oxygen concentration in real time.

Restoration and evaluation for severed streams in high-density urban areas based on a multi-objective framework: A case study of Heping Stream in Nanjing

Numerous severed streams that emerge during rapid urbanization has been negatively impacting regional water systems and urban environments. Traditional restoration efforts are prone to focus on water quality, overlooking the complex of urban severed stream as natural-social ecosystems. However, current literature indicates a lack of systematic restoration methods and post-implementation evaluations tailored to severed streams, which adversely affects water resource management and sustainable urban development. This study bases on research of the severed streams in Nanjing’s Hexi New District to develop methods for the restoration and evaluation of severed streams in high-density urban areas. Taking the Heping Stream as a case study, it took three years to complete a full-process study encompassing the design, implementation, and post-occupancy evaluation of the restoration of the severed stream. We developed a multi-objective framework, including five measures for the restoration of severed streams, along with performance evaluation indicators from environmental, social, and economic perspectives to compare the state of the severed-stream before and after the restoration. So as to assess the effectiveness of the restoration methods and to put forward suggestions for the improvement of the restoration measures. The results showed that the method had a positive effect on the quality of the water environment, public evaluation, capital investment and energy consumption. Some of the environmental performance indicators were significantly improved after the restoration, especially the dissolved oxygen content, water flow. Most of the social performance indicators were better after the restoration than before. In terms of economic performance indicators, the use of photovoltaic energy resulted in significant savings in electricity and pumping costs. Performance evaluation confirmed comprehensive benefits of the method, with Run off Control, Waterfalls Construction and Riverbank Ecological Restoration being most effective. To improve the benefits of restoration, diverse strategies should be combined together, including runoff control, artificial wetlands, vegetated buffers, and riverbank restoration. This research can support the optimization of future restoration measures and scientific decision-making in urban severed-stream restoration.

Complex landscape, instream and anthropogenic environmental features drive genetic and morphological structuring amongst brown trout (Salmo trutta) populations in a dendritic river system

Abstract Untangling the patterns and proximate drivers of intraspecific genetic and phenotypic structuring informs our understanding of the evolutionary processes shaping diversity. This study investigated morphological and genetic structuring of brown trout (Salmo trutta L.) populations across varying spatial scales in a single, complex, dendritic river catchment and examined the potential natural and anthropogenic environmental features driving this structuring. Morphometric and hierarchical genetic structuring analyses of fish from 22 sampling sites in the River Foyle catchment, Ireland (~ 4500km2) identified 19 morphologically distinct groups and 15 genetically distinct populations, separated by river distances ranging from 0.4 km to 188 km. Isolation by Distance was the main factor shaping both genetic and morphological divergence, indicating that strong philopatry is one of the major drivers of the observed population structuring in this system. However, both natural and anthropogenic environmental variables also explained pairwise genetic and morphological differences between sampling sites. Thus, the pairwise differences in the area of woodland in the upstream catchment, water phosphorus concentration, biological oxygen demand, catchment slope, urban area in upstream catchment, altitude, site specific percentage of canopy cover and dissolved oxygen concentration in the river channel were correlated with genetic divergence. The pairwise differences in the concentration of suspended solids, the extent of bankside overhang, the composition of bedrock, boulder and cobble substrates, watercourse width, catchment slope and site altitude were correlated with between-site morphological differences. We hypothesise that local differential selection pressures comprising both natural environmental variation and variation resulting from anthropogenic effects, in combination with strong philopatry and random genetic processes drive the clearly defined genetic and phenotypic patterns described here.

Effects of Transport Stress (Duration and Density) on the Physiological Conditions of Marbled Rockfish (Sebastiscus marmoratus, Cuvier 1829) Juveniles and Water Quality

Live transportation is a critical component of fish farming and hatchery release. To optimize hatchery-release techniques and improve the survival rate of marbled rockfish (Sebastiscus marmoratus, Cuvier 1829) juveniles, the effects of varying transport durations (2, 4, 6, and 8 h) and densities (60, 90, 120, and 150 kg m−3) on the physiological indicators of the fish and water quality were investigated under controlled laboratory conditions. We found that as transport duration and density increased, water quality significantly deteriorated, with ammonia nitrogen levels rising and dissolved oxygen content and pH levels decreasing. Physiological indicators including levels of lactate, cortisol, and malondialdehyde and activities of superoxide dismutase, alkaline phosphatase, and glutamate oxaloacetate transaminase notably increased, indicating that the fish experienced heightened stress during transport. Additionally, the mortality rate of juveniles increased significantly with increasing density and transport duration. The high mortality rate might be associated with sustained elevated cortisol levels and liver damage. Our results are helpful for determining the optimal transport conditions for S. marmoratus juveniles and also provide valuable insights for improving transport techniques for other aquatic animal species.

Health risks and pathological effects of heavy metals in Oreochromis mossambicus from Usuma River, Nigeria.

Heavy metals environmental pollution has become a global menace requiring constant biomonitoring and concerted efforts towards its reduction. There are reports of heavy metals pollution of Usuma River, Gwagwalada, Federal Capital Territory, Nigeria. However, information on the direct and indirect health impacts of such pollution on inhabiting fish and on their human consumers are non-existent, especially in Oreochromis mossambicus. The analyses of the physicochemical parameters of Usuma River water, fish heavy metals, histopathological changes, and health risks were performed according to standard procedures. The physicochemical characteristics of the Usuma River water were within acceptable ranges. The Pb bioaccumulation at 2.5100 ± 0.42mg/kg was significantly (p < 0.05) higher than the values recorded for Cd at 0.4267 ± 0.16mg/kg and zinc at 0.6027 ± 0.02mg/kg. Nevertheless, Pb and Cd bioaccumulated more than their recommended permissible levels. Human health risks assessment revealed no immediate carcinogenic risk at a target rate of between 1.2690 × 10-5 - 2.3530 × 10-5. The current heavy metals' concentration posed no long-term non-carcinogenic risk at a hazard index of less than one. This is because the target rate figure above 1.0 × 10-3 and the hazard index figure above one signifies great health risks. The recorded gills and hepatic cellular changes did not affect organ functionalities as their obtained degree of tissue change figures were all below 10 based on the protocol. Although there was a positive strong correlation between the water temperature and its biochemical oxygen demand as well as between the water dissolved oxygen content and gill cellular changes, a negative strong correlation existed between the water pH and its electrical conductivity and total dissolved solids. The findings highlighted the progressing volatility of heavy metals pollution dynamics within the study area that could pose great human health risks, if unchecked.

Keystone taxa drive the synchronous production of methane and refractory dissolved organic matter in inland waters

The production of both methane (CH4) and refractory dissolved organic matter (RDOM) depends on microbial consortia in inland waters, and it is unclear yet the link of these two processes and the underlying microbial regulation mechanisms. Therefore, a large-scale survey was conducted in China's inland waters, with the measurement of CH4 concentrations, DOM chemical composition, microbial community composition, and relative environmental parameters mainly by chromatographic, optical, mass spectrometric, and high-throughput sequencing analyses, to clarify the abovementioned questions. Here, we found a synchronous production of CH4 and RDOM linked by microbial consortia in inland waters. The increasing microbial cooperation driven by the keystone taxa (mainly Fluviicola and Polynucleobacter) could promote the transformation of labile DOM into RDOM and meanwhile benefit methanogenic microbial communities to produce CH4. As such, CH4 and RDOM showed consistent spatial differences, which were mainly influenced by total nitrogen and dissolved oxygen concentrations. This finding deepened the understanding of microbial-driven carbon transformation and will help to more accurately evaluate the carbon source-sink relationship in inland waters.

Temporal shift in groundwater fauna in southwestern Germany

Abstract. Groundwater is an important source of freshwater; drinking water; and service water for irrigation, industrial and geothermal uses. It is also the largest terrestrial freshwater biome in the world. In many areas, this habitat is naturally or anthropogenically threatened. This study uses long-term groundwater data from southwestern Germany to identify shifts in groundwater fauna due to natural or anthropogenic impacts. Comprehensive analysis of metazoan groundwater fauna and abiotic parameters from 16 monitoring wells over 2 decades revealed no overall temporal trends in faunal abundance or biodiversity (in terms of number of species) and no significant large-scale trends in abiotic parameters. While 9 wells out of 16 show stable ecological and hydrochemical conditions at a local level, the remaining wells exhibit shifting or fluctuating faunal parameters. At some locations, these temporal changes are linked to natural causes, such as decreasing dissolved oxygen contents or fluctuating temperatures. A multivariate PHATE (Potential of Heat-diffusion for Affinity-based Trajectory Embedding) analysis suggests that, beside the hydrogeological setting, varying contents of sediment and detritus impact faunal abundance. By examining aerial images of the surroundings of individual wells, we found that anthropogenic impacts, such as construction sites and surface sealing, can cause significant shifts in groundwater fauna and changes in the ecological status in positive as well as negative direction. However, variable faunal compositions and abundances were also observed for sites with very stable abiotic conditions in anthropogenically less affected areas such as the Black Forest. These findings indicate that hydro(geo)logical changes and surface conditions, such as land use, should be assessed in line with hydrochemical parameters to better understand changes in groundwater fauna. Accordingly, reference sites for natural conditions in ecological assessment and biomonitoring schemes for groundwater protection should be selected carefully.

Effects of Temperature, Dissolved Oxygen Concentration, and Photosynthetic Photon Flux Density on the Growth of the Sea Bivalve Tridacna crocea in Combination with the Symbiotic Alga Zooxanthella

The sea bivalve clam Tridacna crocea inhabiting the shallow sea of tropical and subtropical zones lives with the symbiotic alga zooxanthella in its mantle. Zooxanthellae algae perform photosynthesis and supply nutrients to T. crocea. Recently, the abundance of T. crocea has decreased rapidly due to overfishing in coastal areas in Okinawa, Japan. T. crocea culture systems for mass production will contribute to the conservation of T. crocea and thus marine ecosystems. Environmental control methods for T. crocea culture have not been established because of a lack of knowledge about the appropriate environmental conditions for T. crocea growth. The present study was initiated to obtain basic data for developing environmental control methods for T. crocea land-based aquaculture. The effects of water temperature, dissolved oxygen concentration, and photosynthetic photon flux density (PPFD) on the O2 exchange rates of the symbiotic system of T. crocea and zooxanthella, which are indicators of photosynthesis and respiration in the system, and the effect of daily integrated PPFD on T. crocea growth were investigated. Basic knowledge was obtained for the development of optimal environmental control technology for T. crocea clam culture. The optimum water temperature and dissolved oxygen concentration for photosynthesis in this symbiotic system were 28 °C, 5–6 mgO2 L−1 and 500 μmol m−2 d−1, respectively. The optimum daily integrated PPFD for clam growth was 20 mol m−2 d−1.

Microbial Reduction of Solid-Phase Humin by Shewanella oneidensis MR-1 and its Potential Effect on Contaminant Transformation

Insoluble humic substances-humin (HM) are ubiquitous in the environment and often coexist with iron reducers. Previous research has focused on the electron-donating process from HM to iron reducers; however, the reduction process of HM by iron reducers and its impact on the fate of typical contaminants are still poorly understood. In this study, Shewanella oneidensis MR-1 was selected as a model iron reducer, and its ability to reduce HM and the potential environmental impact of bioreduced HM were investigated. The results showed that S. oneidensis MR-1 reduced HMs extracted from different sources to different extents. This process is highly dependent on lactate concentration, salinity, pH, and dissolved oxygen concentration. Alginate bead experiments indicated that the indirect pathway accounted for 40% of the total electrons transferred from S. oneidensis MR-1 to HM. Electrochemical and spectrochemical analyses further revealed that in addition to flavin, c-type cytochrome may mediate electron transfer. The quinone and iron components may be the main functional groups of HM that accept electrons. Finally, we showed that after being reduced by S. oneidensis MR-1, HM can act as an electron donor for microbial nitrate reduction and the chemical reduction of Cr(VI), with electron-mediation efficiencies of 93% and 56%, respectively.

Assessment of lake Markakol’s physical and chemical condition with consideration of eutrofication

The study was conducted in 2023 and comprised a comparative assessment of the state of Lake Markakol’s aquatic ecosystems in surface and bottom water strata. The analysis of bottom water temperatures showed correlation between this parameter and dissolved oxygen concentrations, indicating that pollution caused by organic impurities leads to lake eutrophication, in turn, pro-pelling the extinction of aquatic life. Although the main water physicochemical parameters of Markakol Lake correspond to the oligotrophic type, the shifts in dissolved oxygen and phos-phate content, as well as growth of aquatic vegetation indicate its transition to the mesotrophic type. Higher phosphate content in water is a consequence of pollution disturbing the biological balance, as well as stimulating the reservoir’s eutrophication and increased biological productivity, i.e. algal bloom. In addition, phosphate ions serve an informative indicator of Hazard Class 3 (organoleptically hazardous) anthropogenic pollution. Based on the correlation factor (r), two statistical models were considered for the target lake: 1) Water Pollution: nutri-ent concentrations depending on surface and bottom water temperatures (Model 1); and 2) changes in Water Pollution Indices (biogenic, heavy metals, mean) because of air temperature growth due to global warming of 0.25°C/decade (Model 2).

Growth, immunomodulatory, histopathological, and antibacterial effects of phytobiotic-incorporated diets on Oreochromis niloticus in unchanged water

Phytobiotics are promising diet alternatives, yet their effectiveness in high-risk aquaculture conditions remains underexplored. Therefore, a 90-day feeding trial was conducted based on dietary supplementation of Nile tilapia, Oreochromis niloticus, with herbal extracts, namely, lemon balm [Melissa officinalis (MOE)], marjoram [Origanum majorana (OME)], and chamomile [Matricaria chamomilla (MCE)] with 0% water change. The treated groups were compared to groups untreated with herbs or control groups [positive control (PC; 0% water change) and negative control (NC; 20% water exchange per day]. Fish were cultured at stocking density (20 fish m-3: 1.8kg of biomass/m3). We conducted a physicochemical analysis of the water and the clinical responses, growth, and immune responses of the fish were evaluated. Furthermore, the herbal-supplemented fish were then challenged with a pathogenic Edwardseilla tarda strain and mortality was monitored. In the 1st and 2nd months, the water parameters were within the permissible limits. After that, a fatally low dissolved oxygen concentration and the highest levels of ammonia, nitrite, nitrate, and pH were recorded during the 3rd month. Blood and immune assays were conducted in the treated groups and control groups. The herbal-treated groups appeared healthy, but during the 3rd month, lethargy and decreased appetite were evident. Generally, the herbal-treated fish showed improved growth performance parameters, survival rates, and resistance against pathogenic bacteria E. tarda, particularly in the OME and MOE-treated groups compared to the positive control group. Finally, phytobiotic supplements were shown to improve fish stress tolerance and immune activation for a certain period under stressful conditions or unchanged water, based on the stocking density, dosages of herbs used, and the extent of deterioration of the water quality.

Common Carp (Cyprinus carpio) Fish Aquaculture Revitalization, Multiplication and Sustainability in Nigeria

Thirty three mature broodfish of Common Carp were harvested from Panyam Fish Farm, Plateau State (PFFPS), and from Federal University of Agriculture Makurdi Research Fish Farm (FUAMRFF). These farms are situated in two different agro-ecological zones of Nigeria (with a fading history of Carp fish culture). The broodfish were fed for 90 days, in preparation for on-farm breeding activities with the aim of determining water quality, hatching parameters (through un-induced natural spawning, induced natural spawning and induced breeding by stripping in indoor concrete ponds); thirdly, to determine percentage survival of the bred Carp fish progenies cultured for 56 days (in ponds sampled in PFFPS and FUAMRFF). Fourthly, to evaluate growth and potential economic returns from the two areas, and finally to further evaluate fish farmers perception of Carp fish culture in selected fish farms across other agro-ecological zones in Nigeria. After breeding activities, progenies were cultured and fed to satiation. The water quality parameters in the ponds and in water holding tanks was monitored daily. At the end of the research period, PFFPS showed better Carp fish hatching tendency, highest (94%) in Induced Natural spawning), with better environmental condition and water physico-chemical parameters for Carp fish culture with mean Dissolved Oxygen content level (8.35 Mg/l), and pH (7.54). Furthermore, PFFPS has capacity to accommodate the mass production of Carp fish. Economically, PFFPS had a higher gross margin (402,250), and Profit index (5.0). Also, result from fish farmers perception on carp fish culture showed that 62% of farmers have no idea of Carp fish management, 66% have no idea of Carp fish selling price, 66% are aware of PFFPS and 100% expressed that more awareness should be created on aquaculture diversification (with interest in Carp fish aquaclture), as this will meet consumer demand and rescue this species from its current track of going extinct in Nigeria, if given urgent attention).

Further Results on the Effects of the Grinding Environment on the Flotation of Copper Sulphides

Grinding conditions affect the flotation of copper sulphide minerals as changes in the properties of the grinding media and their interactions with the sulphide minerals, and between sulphide minerals themselves, affect the chemical environment in the flotation pulp. Galvanic interactions between steel grinding media and sulphide minerals, and between sulphide minerals, can lower the pulp potential, decrease the dissolved oxygen concentration in the mineral slurry, and lead to the dissolution of iron and copper from the media and the minerals. As a result, the formation of hydrophilic iron hydroxides and their adsorption on the copper sulphide minerals can be deleterious to copper flotation while pyrite (when present) can be activated to flotation by dissolved copper lowering the grade of the copper concentrate. Electrochemically less active grinding media (e.g., chrome alloy balls rather than mild steel media) can have beneficial effects on flotation performance due to the lower oxidation of the grinding media and consequently the lower production of oxidised iron species in the pulp. Copper activation of pyrite can be decreased by chemical additions to the pulp. In this paper, relevant experimental data published in the last 15 years are discussed.

Water CO2 Emission Monitoring in a Romanian Peri-Urban Wetland to Enhance GHG Reporting

This study emphasises the complexity of carbon dioxide (CO2) emission dynamics by conducting a wetland case study along the Dambovita River. Our evaluation highlights the importance of considering spatial variability, meteorological parameters and water quality parameters. The variations in CO2 emissions have been monitored using two complementary methods: a closed static chamber and a closed dynamic chamber. The closed dynamic chamber method has the highest level of confidence. The statistical results of correlations facilitated the validation of the closed static chamber method and its independent use in wetland ecosystems. Also, our findings revealed distinct patterns in emissions across locations that are influenced by parameters such as pH, redox potential (ORP), chlorophyll, dissolved oxygen concentration (DO), and temperature for the water–atmosphere interface. These results contribute to the understanding of the carbon cycle in wetlands and contribute to the improvement of greenhouse gas (GHG) reporting by obtaining data with a high level of confidence, regarding the role of wetland ecosystems in the carbon cycle.

ВНУТРЕННИЕ ВОЛНЫ И ИХ ВЛИЯНИЕ НА ИЗМЕНЧИВОСТЬ РАСТВОРЕННОГО КИСЛОРОДА НА ГЕЛЕНДЖИКСКОМ ШЕЛЬФЕ ЧЕРНОГО МОРЯ В ЛЕТНЕЕ ВРЕМЯ

The paper presents field observations of internal waves at the Gelendzhik polygon from 14– 23 June 2023. The measurements were taken simultaneously on four moored thermochaines, installed at a depth of approximately 23 m. Currents were recorded, and the water column was vertically profiled with measurements of temperature, conductivity, and dissolved oxygen. Dissolved oxygen was recorded at a depth of 18 metres on one of the thermochains. The most intense short-period trains recorded after the strengthening of the alongshore north-western current are presented. The internal waves of the first and second modes are revealed. The main parameters of the observed internal waves are estimated. It is shown that near-inertial internal waves approaching the coastal zone contain colder and saltier water with reduced oxygen content. As a result, their approach leads to a 10 % drop in water oxygen saturation at the horizon. An example of the effect of short-period internal waves on dissolved oxygen content is presented.