Effects of potassium on nitrate mediated alterations of osmoregulation in marine crabs

Determination of the Acute and Chronic Toxicity of Sulfate from the Sulfur Autotrophic Denitrification Process to Juvenile Zebrafish (Danio rerio)

Sulfur-based materials are widely used as electron donors for denitrification to enhance nitrogen removal from water. This leads to an increased sulfate concentration in the effluent or sulfate accumulation in recirculating aquaculture systems. This study explored acute and chronic toxicity of sulfate to juvenile zebrafish (Danio rerio) and investigated the histopathological changes in the gills of juvenile zebrafish exposed to sulfate. Results show that zebrafish had a high tolerance to sulfate, with no acute toxicity at sulfate concentrations from 250 to 3200 mg/L. For the chronic toxicity study, it was found that zebrafish mortality decreased with the increase in sulfate concentrations ranging from 250 to 1500 mg/L. In contrast, when the sulfate concentration was 1500-3000 mg/L, zebrafish mortality increased with the increasing sulfate concentration. In addition, in the ion balance test, KCl was added to balance the effects of Na⁺ from the Na₂SO₄ used to obtain the desired sulfate concentrations, showing that fish mortality correspondingly increased with increasing KCl addition. Furthermore, when living in an environment with elevated sulfate concentrations for a long period, changes were observed in the morphology, behavior, and gill tissue of the zebrafish, including slow and lateral swimming; bottom settling; and large opening and closing, lamellar fusion, and necrosis of gills. This research reveals the toxicity of sulfate to aquatic organisms, providing a scientific basis for the promotion and application of sulfur or sulfur-based materials in autotrophic reduction processes for wastewater treatment.

Eggshell membrane derived nitrogen rich porous carbon for selective electrosorption of nitrate from water

Nitrate (NO₃^-) is a ubiquitous contaminant in water and wastewater. Conventional treatment processes such as adsorption and membrane separation suffer from low selectivity for NO₃^- removal, causing high energy consumption and adsorbents usage. In this study, we demonstrate selective removal of NO₃^- in an electrosorption process by a thin, porous carbonized eggshell membrane (CESM) derived from eggshell bio-waste. The CESM possesses an interconnected hierarchical pore structure with pore size ranging from a few nanometers to tens of micrometers. When utilized as the anode in an electrosorption process, the CESM exhibited strong selectivity for NO₃^- over Cl^-, SO₄^2-, and H₂PO₄^-. Adsorption of NO₃^- by the CESM reached 2.4 × 10^-3 mmol/m², almost two orders of magnitude higher than that by activated carbon (AC). More importantly, the CESM achieved NO₃^-/Cl^- selectivity of 7.79 at an applied voltage of 1.2 V, the highest NO₃^-/Cl^- selectivity reported to date. The high selectivity led to a five-fold reduction in energy consumption for NO₃^- removal compared to electrosorption using conventional AC electrodes. Density function theory calculation suggests that the high NO₃^- selectivity of CESM is attributed to its rich nitrogen-containing functional groups, which possess higher binding energy with NO₃^- compared to Cl^-, SO₄^2-, and H₂PO₄^-. These results suggest that nitrogen-rich biomaterials are good precursors for NO₃^- selective electrodes; similar chemistry can also be used in other materials to achieve NO₃^- selectivity.

Influence of cerium oxide nanoparticles on dairy effluent nitrate and phosphate bioremediation

This study investigated, for the first time, the role of cerium oxide nanoparticles (CeO₂ NPs) on dairy effluent nitrate and phosphate bioremediation using different inoculum sources. Two inoculum sources (wastewater and sludge) were obtained from the dairy wastewater treatment plant unit. A culture was prepared to be tested in the treatment of nitrate and phosphate effluent, and the role of CeO₂ NPs was checked to be completely efficient after 5 days of incubation. The reduction efficiency of nitrate using sludge as inoculum source was improved up to 89.01% and 68.12% for phosphate compared to control. In the case of using wastewater as an inoculum source, the nitrate reduction was improved up to 83.30% and 87.75% for phosphate compared to control. The bacterial richness showed a significant variance (higher richness) between control and other samples. The optimal concentration of CeO₂ NPs for inoculum richness and nitrate and phosphate reduction was (sludge: 1 × 10^-10 ppm) and (wastewater: 1 × 10^-12 ppm). The results revealed that CeO₂ NPs could enhance the microbial growth of different inoculum sources that have a key role in dairy effluent nitrate and phosphate bioremediation.

Physiological changes in the hemolymph of juvenile shrimp Litopenaeus vannamei to sublethal nitrite and nitrate stress in low-salinity waters

Juveniles of the shrimp Litopenaeus vannamei (3.3 ± 0.4 g) were exposed separately to nitrite (0.0, 1.1, 2.6, and 5.3 mg/L nitrogen as nitrite [NO₂^--N]) and nitrate (0, 90, 225 and 400 mg/L nitrogen as nitrate [NO₃^--N]) concentrations equivalent to 0, 10, 25, and 50% of the LC₅₀-96 h value of NO₂^--N and NO₃^--N in low salinity water (3 g/L). Shrimps responded to nitrite and nitrate according to changes in oxyhemocyanin, glucose, lactate and ion levels in the hemolymph after 6, 12, 24, and 48 h of exposure. Oxyhemocyanin levels decreased with increasing nitrite and nitrate levels and were higher at 50% exposure to the contaminants. Compared to the control, glucose and lactate increased significantly at 50% exposure to nitrite and nitrate, particularly at 12 and 24 h. Na⁺ in the hemolymph changed with nitrite and nitrate, while K⁺ only changed ˜with nitrite.

Uptake of Sulfate from Ambient Water by Freshwater Animals

To better understand how the sulfate (SO4 2-) anion may contribute to the adverse effects associated with elevated ionic strength or salinity in freshwaters, we measured the uptake and efflux of SO4 2- in four freshwater species: the fathead minnow (Pimephales promelas, Teleostei: Cyprinidae), paper pondshell (Utterbackia imbecillis, Bivalvia: Unionidae), red swamp crayfish (Procambarus clarkii, Crustacea: Cambaridae), and two-lined mayfly (Hexagenia bilineata, Insecta: Ephemeridae). Using δ( 34 S/ 32 S) stable isotope ratios and the concentrations of S and SO4 2-, we measured the SO4 2- influx rate (J in ), net flux (J net ), and efflux rate (Jout) during a 24 h exposure period. For all four species, the means of J in for SO4 2- were positive, and J in was significantly greater than 0 at both target SO4 2- concentrations in the fish and mollusk and at the lower SO4 2- concentration in the crayfish. The means of J out and J net were much more variable than those for J in , but several species by target SO4 2- concentration combinations for J out and J net , were negative, which suggests the net excretion of SO4 2- by the animals. The results of our experiments suggest a greater regulation of SO4 2- in freshwater animals than has been previously reported.

Nitrate level safety to Amazon River shrimp juveniles

The study's objective was to evaluate the nitrate level safety for Macrobrachium amazonicum juvenile in the laboratory, a potential native species for culture in Brazil. The experiment consisted of six treatments with six replicates in a completely randomized block design: 0, 250, 500, 1,000, 1,500, and 2,000 mg L^-1. Physical and chemical water quality parameters were recorded every 12 h, while the shrimp mortalities in the 24-h interval. Except for nitrate, all physical and chemical water quality parameters remained within the ideal range rearing to this species. No deaths were observed during the first 6 h of exposure range 0-500 mg L^-1 concentrations. At 250 mg L^-1 N-NO₃^-, the mortality (10%) started from 48 h. At 500 mg L^-1 N-NO₃^-, shrimp mortalities occurred after 24 h, reaching 60% after 72 h. In the treatments with 1000 and 1500 mg L^-1 N-NO₃^- concentrations, dead shrimps can be observed after 24 h, with a mortality rate of 78% and 90% of the population in 96 h, respectively. All shrimps exposed at 2000 mg L^-1 died in 96 h. The LC50 values obtained decreased with increasing exposure time. Based on LC50 (96 h), the N-NO₃^- level safety to M. amazonicum is 48.5 mg L^-1.

Toxicity of ammonia, nitrite and nitrate to Litopenaeus vannamei juveniles in low-salinity water in single and ternary exposure experiments and their environmental implications

Information on toxicity of nitrogen compounds for Litopenaeus vannamei in coastal ecosystems and culture under low salinity is scarce. Acute toxicity trials were conducted in L. vannamei to determine the single and combined effects of ammonia, nitrite and nitrate at a salinity of 3 g/L. The 96 h-LC₅₀ was 29.0 mg/L for total ammonia nitrogen (TAN); 10.6 mg/L for nitrogen as nitrite (NO₂^--N); and 900 mg/L for nitrogen as nitrate (NO₃^--N). The joint effects of ammonia, nitrite and nitrate exposure were antagonistic at 24-72 h; and additive from 72 to 96 h. The proposed safety levels of single exposure to TAN, NO₂^--N and NO₃^--N for L. vannamei are 1.45, 0.53 and 45.0 mg/L, respectively. When in mixture, the proposed level of TAN/NO₂^--N/NO₃^--N is 0.05 TU (Toxicity Unit) corresponding to 0.48, 0.08 and 14.6 mg/L of TAN, NO₂^--N and NO₃^--N, respectively.

Water Quality Assessment of the Semenyih River, Selangor, Malaysia

This study was carried out to determine the Semenyih River water quality based on the physicochemical and biological parameters. The sampling was conducted in dry and rainy seasons during 2012. Water samples were collected from 8 stations along the river and analyzed using standard methods. The results showed that temperature, pH, conductivity, TDS, SO4, and TH were classified as class I, while DO, turbidity, and BOD were categorized under class II, and NH3-N, TSS, COD, and OG were categorized as class III based on NWQS, Malaysia. Moreover, NO3was classified under class IV, while PO4and FC were categorized as class V and exceeded the allowable threshold levels. Therefore, the river was slightly polluted with NH3-N, TSS, COD, and NO3, whereas it is extremely contaminated with PO4and FC. Furthermore, cluster analysis classified 8 sampling stations into three clusters based on similarities of water quality features. Furthermore, factor analysis of the water quality datasets generated three factors with total variance of 94.05% and pointed out that water quality deterioration in the river was associated with industrial and agricultural activities, livestock farming, and erosion. Therefore, the river water can be used for irrigation with precaution but extensive treatment needed before using for domestic purposes.

Survival, osmoregulation and ammonia-N excretion of blue swimmer crab, Portunus pelagicus, juveniles exposed to different ammonia-N and salinity combinations

Ammonia-N toxicity to early Portunus pelagicus juveniles at different salinities was investigated along with changes to haemolymph osmolality, Na(+), K(+), Ca(2+) and ammonia-N levels, ammonia-N excretion and gill Na(+)/K(+)-ATPase activity. Experimental crabs were acclimated to salinities 15, 30 and 45 per thousand for one week and 25 replicate crabs were subsequently exposed to 0, 20, 40, 60, 80, 100 and 120 mg L(-1) ammonia-N for 96-h, respectively. High ammonia-N concentrations were used to determine LC(50) values while physiological measurements were conducted at lower concentrations. When crabs were exposed to ammonia-N, anterior gill Na(+)/K(+)-ATPase activity significantly increased (p<0.05) at all salinities, while this only occurred on the posterior gills at 30 per thousand. For crabs exposed to 20 and 40 mg L(-1) ammonia-N, both posterior gill Na(+)/K(+)-ATPase activity and ammonia-N excretion were significantly higher at 15 per thousand than those at 45 per thousand. Despite this trend, the 96-h LC(50) value at 15 per thousand (43.4 mg L(-1)) was significantly lower (p<0.05) than at both 30 per thousand and 45 per thousand (65.8 and 75.2 mg L(-1), respectively). This may be due to significantly higher (p<0.05) haemolymph ammonia-N levels of crabs at low salinities and may similarly explain the general ammonia-N toxicity pattern to other crustacean species.

Subchronic exposure to nitrite, potassium and their combination on survival, growth, total haemocyte count and gill structure of juvenile blue swimmer crabs, Portunus pelagicus

Among anthropogenic discharges, nitrite and potassium can simultaneously enter aquatic ecosystems at high loading rates which can threaten marine animals. The sensitivity of early juvenile blue swimmer crabs, Portunus pelagicus, to the subchronic exposure to nitrite, potassium and their combination was evaluated by measuring the survival, growth, total haemocyte count (THC) and gill histopathological changes. In all NaNO(2)-N and KNO(2)-N treatments the survival substantially decreased, many due to "molt death syndrome", along with significantly lower (p<0.01) specific growth rates (SGR). Although fewer deaths occurred in the KCl-K treatments, the SGR at the higher concentrations were significantly less (p<0.05) than the control. The gill histopathological changes following elevated NaNO(2)-N, KNO(2)-N and KCl-K exposure showed drastic but similar damage. In spite of a long term healing response, indicated by a significant hemolymph THC increase (p<0.01) and several gill lamellae modifications, early P. pelagicus juveniles are highly sensitive to elevated NO(2)-N levels.