A study was carried out to determine the pathogenicity (hemolytic activity) on corals (Turbinaria sp.) and sea bass (Lates calcarifer) of Aeromonas hydrophila from water, sediment, and coral. Samples were collected from coastal water and coral reef areas. One hundred and sixty-two isolates were successfully isolated. Out of 162, 95 were from seawater, 49 from sediment, and 18 from coral. Sixteen isolates were picked and identified. Isolates were identified using a conventional biochemical test, the API 20NE kit, and 16S rRNA nucleotide sequences. Hemolytic activity was determined. Out of 16 isolates, 14 isolates were β-hemolytic and two isolates were non-hemolytic. Corals infected with A. hydrophila suffered bleaching. Similar effect was observed for both hemolytic and non-hemolytic isolates. Intramuscular injection of A. hydrophila into sea bass resulted in muscular bleeding and death. Higher infection rates were obtained from hemolytic compared to non-hemolytic strains of A. hydrophila isolates.

The main objective of the present study was to determine the optimum C/N ratio for converting waste paper and chicken manure to nutrient-rich manure with minimum toxicity. Six treatments of C/N ratio 20, 30, 40, 50, 60, and 70 (T1, T2, T3, T4, T5, and T6, respectively) achieved by mixing chicken manure with shredded paper were used. The study involved a composting stage for 20 days followed by vermicomposting with Eisenia fetida for 7 weeks. The results revealed that 20 days of composting considerably degraded the organic waste mixtures from all treatments and a further 7 weeks of vermiculture significantly improved the bioconversion and nutrient value of all treatments. The C/N ratio of 40 (T3) resulted in the best quality vermicompost compared to the other treatments. Earthworm biomass was highest at T3 and T4 possibly due to a greater reduction of toxic substances in these waste mixtures. The total N, total P, and total K concentrations increased with time while total carbon, C/N ratio, electrical conductivity (EC), and heavy metal content gradually decreased with time during the vermicomposting process. Scanning electron microscopy (SEM) revealed the intrastructural degradation of the chicken manure and shredded paper matrix which confirmed the extent of biodegradation of treatment mixtures as result of the composting and vermicomposting processes. Phytotoxicity evaluation of final vermicomposts using tomato (Lycopersicon esculentum), radish (Raphanus sativus), carrot (Daucus carota), and onion (Allium cepa) as test crops showed the non-phytotoxicity of the vermicomposts to be in the order T3 > T4 > T2 > T1 > T5 > T6. Generally, the results indicated that the combination of composting and vermicomposting processes is a good strategy for the management of chicken manure/paper waste mixtures and that the ideal C/N ratio of the waste mixture is 40 (T3).

To conserve water resources and guarantee food security, a new technology termed as “wet irrigation” is developed and practiced in rice fields; thus, its impact on radiative forcing derived from nitrous oxide (N₂O) and methane (CH₄) emissions merits serious attention. Dicyandiamide (DCD), a kind of nitrification inhibitor, is proposed as a viable means to mitigate greenhouse gas (GHG) emission while enhancing crop productivity. However, little is known about the response of GHG emission and grain yield to DCD application in a rice system under wet irrigation. In these regard, effects of water regime and DCD application on CH₄ and N₂O emissions, grain yield, global warming potential (GWP), and greenhouse gas intensity (GHGI) from rice fields were studied. For this study, a field experiment, designed: Treatment II (intermittent irrigation), Treatment WI (wet irrigation), Treatment IID (II plus DCD), and Treatment WID (WI plus DCD), was conducted in Jurong, Jiangsu Province, China, from 2011 to 2012. Relative to Treatment II, Treatment WI decreased CH₄ emission significantly by 49–71 % while increasing N₂O emission by 33–72 %. By integrating CH₄ and N₂O emissions and grain yield, Treatment WI was 20–28 and 11–15 % lower than Treatment II in GWP and GHGI, respectively. The use of DCD under wet irrigation reduced N₂O emission significantly by 25–38 % (p < 0.05) and CH₄ emission by 7–8 %, relative to Treatment WI, resulting in a decline of 18–30 % in GWP. Due to the increase in N use efficiency, maximal grain yield (6–7 %) and minimal GHGI (22–34 %) was observed in Treatment WID. These findings indicate that combined application of N fertilizer and DCD is a win-win strategy in water-saving high-yield rice production with less GHG emission.

As concentrations of greenhouse gases (GHG: N₂O, CO₂, CH₄) continue to increase in the earth’s atmosphere, there is a need to further quantify the contribution of natural systems to atmospheric GHG concentrations. Within this context, characterizing GHG contributions of riparian zones following storms events is especially important. This study documents soil GHG effluxes in a North Carolina riparian zone in the days following both a natural 2.5-cm precipitation event, and that same event associated with the addition of 8.7 cm artificial rainwater in select static chambers. No significant differences in CO₂, CH₄, and N₂O fluxes in response to increased moisture were observed between a depression, a sand bar, and an upland forested area. However, in this water-limited riparian zone, less negative CH₄ fluxes (i.e., methane oxidation decreased) and higher CO₂ fluxes (i.e., aerobic respiration increased) were observed following precipitation. A short-term burst in N₂O emission was observed in the hours after precipitation occurred, but elevated N₂O emissions did not persist long enough to turn the site from the N₂O sink to a N₂O source in the 3 days following the beginning of the experiment. Our results are in contrast with riparian GHG studies in wetter environments and illustrate the importance of water limitation in regulating riparian soil response to precipitation with respect to GHG emissions. More studies should be conducted in water-limited environments (e.g., US southeast/southwest) before management strategies commonly applied in wetter environments (e.g., US Northeast/Midwest) are applied in these regions.

Predicting the soil-to-plant transfer of metals in the context of global warming has become a major issue for food safety. It requires a better understanding of how the temperature alters the bioavailability of metals in cultivated soils. This study focuses on one agricultural soil contaminated by Cd, Zn and Pb. DGT measurements were performed at 10, 20 and 30 °C to assess how the bioavailability of metals was affected by a rise in soil temperature. A lettuce crop was cultivated in the same conditions to determine if the soil-to-plant transfer of metals increased with a rise in soil temperature. A gradual decline in Cd and Zn bioavailability was observed from 10 to 30 °C, which was attributed to more intense complexation of metals in the pore water at higher temperatures. Together with its aromaticity, the affinity of dissolved organic matter (DOM) for metals was indeed suspected to increase with soil temperature. One main output of the present work is a model which satisfactorily explains the thermal-induced changes in the characteristics of DOM reported in Cornu et al. (Geoderma 162:65–70, 2011) by assuming that the mineralization of initial aliphatic compounds followed a first-order reaction, increased with soil temperature according to the Arrhenius law, and due to a priming effect, led to the appearance of aromatic molecules. The soil-to-plant transfer of Cd and Zn was promoted at higher soil temperatures despite a parallel decrease in Cd and Zn bioavailability. This suggests that plant processes affect the soil-to-plant transfer of Cd and Zn the most when the soil temperature rises.

In spite of extensive studies on multispecies toxigenic cyanobacterial blooms, they are still difficult to eliminate, and factors regulating their succession and toxin production remain still to discover. A 4-year study revealed periodical mass development of diazotrophic Nostocales such as Dolichospermum spp. (previously Anabaena), Aphanizomenon gracile and expansive Cuspidothrix (previously Aphanizomenon) issatschenkoi in a lake affected by perennial blooms of Planktothrix agardhii (Oscillatoriales). Compared to Oscillatoriales, Nostocales reached the highest total biomass (up to 16 mg L⁻¹) and contributed nearly 33–85 % to the total biomass of filamentous cyanobacteria at higher water temperatures (average values 17.5–22.6 °C) and higher ratio (11.8–14.1) of dissolved inorganic nitrogen to dissolved inorganic phosphorus (DIN/DIP). Species structure of Nostocales changed considerably from year to year as indicated by the Jaccard similarity index (0.33–0.78). Concentrations of intracellular anatoxin-a (ANTX) ranged from 0.03 to 2.19 μg L⁻¹ of the lake water, whilst extracellular toxin reached up to 0.55 μg L⁻¹. The highest positive correlations were found between the intracellular ANTX and the biomass of Dolichospermum spp. (R ² = 0.73) and C. issatschenkoi (R ² = 0.43–0.65). Our study suggests that ANTX production by Dolichospermum depended mainly on water temperature, whereas that by C. issatschenkoi was related to water conductivity and DIN/DIP ratio. P-PO₄ concentrations also seemed to be important. The relatively short-term mass development of neurotoxic Nostocales is an additional threat to shallow, highly eutrophic water bodies continuously affected by Oscillatoriales blooms and may be controlled mainly by the DIN/DIP ratio. ANTX should be considered as a pollutant of freshwaters.

In the present study, multi-walled carbon nanotubes (MWCNTs) have been used for the rapid removal of four trihalomethanes (THMs) from aqueous solutions. The adsorption capacity of THMs onto MWCNTs was reasonably constant in the pH range of 5–7 but decreased as the pH exceeded 7. Four equilibrium isotherm models, namely, Langmuir, Freundlich, Temkin, and Sips, were applied to determine the best-fit equilibrium expressions. The results showed that all four experimental adsorption isotherms were best correlated by using the Sips model. The maximum adsorption capacities for the CHCl₃, CHCl₂Br, CHClBr₂, and CHBr₃ were found to be 10.98, 6.85, 6.57, and 5.95 mg/g, respectively. The rate of adsorption followed the pseudo-second-order kinetic model. Furthermore, four nonlinear regression-based equations were also derived to model THM adsorption from aqueous solutions by MWCNTs. The modeling results clearly indicated that the empirical formulations satisfactorily described the behavior of the present adsorption process for CHCl₃ (R ² = 0.949), CHCl₂Br (R ² = 0.945), CHClBr₂ (R ² = 0.936), and CHBr₃ (R ² = 0.919). The overall results confirmed that MWCNTs could be a promising adsorbent material for THMs removal from aqueous solutions.

Zeolitic imidazole frameworks (ZIFs), a new adsorbent with a high chemical and thermal stability and a high adsorption capacity, are used for adsorptive removal of azo dyes. The synthesized ZIF-67 was characterized with Fourier transform infrared spectroscopy (FTIR), thermogravimetric–differential thermal analysis (TG–DTA) and zeta potential instrument. The adsorption of some azo dyes on ZIF-67 in the single dye systems showed that the removal efficiencies are congo red > methyl orange > methyl red > methyl blue. The highest adsorption capacity of congo red and methyl orange were 3900 and 1340 mg/g, respectively. In a binary dye system the adsorption capacity of congo red decreased, while the removal efficiency of methyl orange increased in comparison with the single systems, indicating that a competitive adsorption of congo red and methyl orange over the ZIF-67 occurred. The experimental data indicate that the electrostatic attraction between ZIF-67 and congo red is the major driving force and the π–π stacking is also responsible for dye adsorption. After 5 cycles of ZIF-67 adsorption and desorption, the congo red removal efficiency maintained more than 95%. Graphical Abstract The adsorption of Congo red and Methyl orange on the ZIF-67

Hexavalent chromium (VI) in wastewater is a great risk to human health and to the quality of water sources. However, adapted microorganisms can rapidly reduce this chemical species to the trivalent form (III) and make it less active. Our objective was to evaluate the capacity of bacterial isolates for Cr (VI) reduction in nutrient medium and in effluent and to compare indigenous microorganisms with those isolated from wastewater contaminated with Cr (VI). Cr (VI) reduction was also tested with different sources of carbon, nitrogen, and phosphorus at two temperatures (10 and 30 °C). Initially, the resistant microorganisms were isolated from the solution with 100 mg L⁻¹ of Cr (VI). Subsequently, we evaluated the effectiveness of the isolates in reducing Cr (VI) I in culture medium under temperature-controlled conditions, with concentrations of 10 and 100 mg L⁻¹ of Cr (VI). In the subsequent step, we studied the isolates and autochthonous microorganism efficiency to reduce Cr (VI) present in contaminated effluent, with the addition of nutrients and at different temperatures (10 and 30 °C). In the culture medium containing 10 mg L⁻¹ of Cr (VI), isolates were reduced by 100 % in 48 h. When tested against 100 mg L⁻¹ of Cr (VI), the decrease was 70 and 40 % at 120 h of incubation of the isolates 6 and 11, respectively. In the effluent, there was no significant reduction without nutritional biostimulation. When carbon and phosphorus were applied, isolates 6, 11, and indigenous microorganisms reduced 100 % of the Cr (VI) in 72 h. Nitrogen was not limited in terms of effluent characteristics. At 10 °C incubation temperature, Cr (VI) was completely reduced but slower compared to incubation at 30 °C. The results demonstrate that nutritional biostimulation aided by bioremediation is an excellent tool for reducing hexavalent chromium in wastewater.

This study evaluated the seed germination and dry mass accumulation of five plant species (Brassica napus L., Brassica rapa L., Celosia cristata L., Tagetes erecta L., and Calendula officinalis L.) grown in five mine tailings collected from Zacatecas, Mexico. Sampled mines were El Bote, Noria de San Pantaleon, Noria de Angeles, Vetagrande, and El Bordo-El Lampotal, in which Pb (3.9–69.7 mg kg⁻¹), As (0.7–26.2 mg kg⁻¹), Hg (0.05–0.10 mg kg⁻¹), and Au (0.01–0.02 mg kg⁻¹) were detected. The most abundant elements at each mine site were as follows: Pb and Au (3.9 and 0.023 mg kg⁻¹, respectively) for El Bote; As, Pb, and Hg (7.4, 6.1, and 0.10 mg kg⁻¹, respectively) for the Noria de San Pantaleon; Pb, As, and Hg (69.7, 26.2, and 0.08 mg kg⁻¹, respectively) for Noria de Angeles; Pb (20.8 mg kg⁻¹) for Vetagrande; and Pb (5.3 mg kg⁻¹) for El Bordo-El Lampotal. Both Noria de Angeles and Vetagrande mine tailings had high values of sodium, sulfates, and electrical conductivity, chemical properties that impaired seed germination and dry mass accumulation. Regardless the mining tailings, B. napus showed high seed germination (66 %), tolerance, growth, and total dry mass accumulation (0.041 g). Either B. napus or C. cristata has good potential for stabilizing or recovering metals from mine tailings.