Extracellular Polymeric Substances (EPS) influenced Poly Cyclic Aromatic Hydrocarbons (PAHs) degrading Klebsiella pneumoniae was isolated from the marine environment. To increase the EPS production by Klebsiella pneumoniae, several physicochemical parameters were tweaked such as different carbon sources (arabinose, glucose, glycerol, lactose, lactic acid, mannitol, sodium acetate, starch, and sucrose at 20 g/L), nitrogen sources (ammonium chloride, ammonium sulphate, glycine, potassium nitrate, protease peptone and urea at 2 g/L), different pH, carbon/nitrogen ratio, temperature, and salt concentration were examined. Maximum EPS growth and biodegradation of Anthracene (74.31%), Acenaphthene (67.28%), Fluorene (62.48%), Naphthalene (57.84%), and mixed PAHs (55.85%) were obtained using optimized conditions such as glucose (10 g/L) as carbon source, potassium nitrate (2 g/L) as the nitrogen source at pH 8, growth temperature of 37 °C, 3% NaCl concentration and 72 h incubation period. The Klebsiella pneumoniae biofilm architecture was studied by confocal laser scanning microscopy (CLSM) and scanning electron microscope (SEM). The present study demonstrates the EPS influenced PAHs degradation of Klebsiella pneumoniae.

The generation of HONO and NO₂ by the photolysis of nitrates in the presence of humic acids (HA) was measured under various conditions. The photolysis experiments of HA, KNO₃ and KNO₃/HA under simulated sunlight was carried out by a flow tube reactor at ambient temperature and pressure. HONO and NO₂ were major products by the photolysis of KNO₃. By contrast, the photolysis of HA and KNO₃/HA mainly generated HONO. HA significantly enhanced the formation of HONO during the photolysis process of KNO₃. With increasing the KNO₃ mass, the HONO formation rate (RHONO) on KNO₃/HA increased while the photolysis rate normalized by the KNO₃ mass exhibited an opposite trend. RHONO on KNO₃/HA linearly increased with irradiation intensity (88–262 W/m²) and relative humidity (7–70%), whereas it linearly decreased with the pH (pH = 2–12). In addition, the reaction paths of the HONO formation by the photolysis of nitrates in the presence of HA were proposed according to experimental results. Finally, atmospheric implications of the enhanced HONO formation by the photolysis of nitrates in the presence of HA were discussed.

Extracellular polymeric substances (EPS) found in soils can reduce the mobility of heavy metals through the use of both electrostatic and non-electrostatic mechanisms. Their effects vary from one soil type to another. The influence of EPS from Escherichia coli on the adsorption behaviors of Cu(II) and Cd(II) by two bulk variable charge soils, Oxisol and Ultisol, was studied at constant and varied pH, and the results were compared to a constant charge Alfisol. The maximum adsorption capacities of the soils were significantly (P < 0.05) enhanced in the presence of EPS, with Cu(II) adsorption being greater. Interaction of EPS with soils made the soil surface charge more negative by neutralizing positive charges and shifting the zeta potentials in a negative direction: from −18.6 to −26.4 mV for Alfisol, +5.1 to −22.2 mV for Oxisol, and +0.3 to −28.0 mV for Ultisol at pH 5.0. The adsorption data fitted both the Freundlich and Langmuir isotherms well. Preadsorbed Cd(II) was more easily desorbed by KNO₃ than preadsorbed Cu(II) from both the control and EPS treated soils. The adsorption of both metals was governed by electrostatic and non-electrostatic mechanisms, although more Cu(II) was adsorbed through the non-electrostatic mechanism. The information obtained in this study will improve our understanding of the mechanisms involved in reducing heavy metals mobility in variable charge soils and hence, their bioavailability.

Microplastics are an emerging contaminants of concern in aquatic environments. The aggregation behaviors of microplastics governing their fate and ecological risks in aquatic environments is in need of evaluation. In this study, the aggregation behavior of polystyrene microspheres (micro-PS) in aquatic environments was systematically investigated over a range of monovalent and divalent electrolytes with and without natural organic matter (i.e., Suwannee River humic acid (HA)), at pH 6.0, respectively. The zeta potentials and hydrodynamic diameters of micro-PS were measured and the subsequent aggregation kinetics and attachment efficiencies (α) were calculated. The aggregation kinetics of micro-PS exhibited reaction- and diffusion-limited regimes in the presence of monovalent or divalent electrolytes with distinct critical coagulation concentration (CCC) values, followed the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The CCC values of micro-PS were14.9, 13.7, 14.8, 2.95 and 3.20 mM for NaCl, NaNO3, KNO3, CaCl2 and BaCl2, respectively. As expected, divalent electrolytes (i.e., CaCl2 and BaCl2) had stronger influence on the aggregation behaviors of micro-PS as compared to monovalent electrolytes (i.e., NaCl, NaNO3 and KNO3). HA enhanced micro-PS stability and shifted the CCC values to higher electrolyte concentrations for all types of electrolytes. The CCC values of micro-PS were lower than reported carbonaceous nanoparticles CCC values. The CCC[Ca2+]/CCC [Na+] ratios in the absence and presence of HA at pH 6.0 were proportional to Z−2.34 and Z−2.30, respectively. These ratios were in accordance with the theoretical Schulze–Hardy rule, which considers that the CCC is proportional to z−6–z−2. These results indicate that the stability of micro-PS in the natural aquatic environment and the possibility of significant aqueous transport of micro-PS.

Mediterranean coastal regions are particularly exposed to oil pollution due to extensive industrialization, urbanization and transport of crude and refined oil to and from refineries. Bioremediation of contaminated beach sand through landfarming is both simple and cost-effective to implement compared to other treatment technologies. The purpose of the present study was to investigate the effect of alternative nutrients on biodegradation of crude oil contaminated beach sand in an effort to reduce the time required for bioremediation employing only indigenous hydrocarbon degraders.A natural sandy soil was collected from Agios Onoufrios beach (Chania, Greece) and was contaminated with weathered crude oil. The indigenous microbial population in the contaminated sand was tested alone (control treatment) or in combination with inorganic nutrients (KNO3 and K2HPO4) to investigate their effects on oil biodegradation rates. In addition, the ability of biosurfactants (rhamnolipids), in the presence of organic nutrients (uric acid and lecithin), to further stimulate biodegradation was investigated in laboratory microcosms over a 45-day period.Biodegradation was tracked by GC/MS analysis of aliphatic and polycyclic aromatic hydrocarbons components and the measured concentrations were corrected for abiotic removal by hopane normalizations. It was found that the saturated fraction of the residual oil is degraded more extensively than the aromatic fraction and the bacterial growth after an incubation period of approximately 3weeks was much greater from the bacterial growth in the control.The results show that the treatments with inorganic or organic nutrients are equally effective over almost 30days where C12–C35n-alkanes were degraded more than 97% and polyaromatic hydrocarbons with two or three rings were degraded more than 95% within 45days. The results clearly show that the addition of nutrients to contaminated beach sand significantly enhanced the activity of indigenous microorganisms, as well as the removal of total recoverable petroleum hydrocarbons (TRPH) over a 45-day study period.

Possible environmental effects of flash powder mixture combustion containing aluminium and boron along with other ingredients like potassium nitrate and sulphur are reported. Once the firecrackers are lighted, they burst out particulate matter and harmful gases with scintillating effect. These particulate matters and the harmful gases together make the environment fogged and get deposited on all surfaces. Recent research suggests replacing aluminium with boron to implement safety during manufacturing and to enhance performance. But the effects of the combustion residue have to be checked and compared before implementation. Hence, in this work, the possible effects of the firework mixtures particularly flash powder mixtures containing aluminium are monitored and compared with the effects of boron blended flash powder mixtures. Based on the smoke settling test, plant growth test and soil test, it is concluded that up to 12.5% of boron can be added in flash powder mixture to prevent pollution of the environment. The threshold quantity of residue without affecting the soil quality for 100 % usage of boron was found as 10 g of residue in 2 kg of soil.

Respiratory quotient (RQ) is a parameter proposed as a tool for practical and online monitoring of petroleum hydrocarbon biodegradation. Various environmental factors and remediation conditions affect RQ values. Occasionally, actual RQ values deviate from theoretical RQ values of petroleum hydrocarbon biodegradation. In addition, different RQ calculation and interpretation approaches investigated in literature make it difficult to compare the results. In this study, different RQ calculation and interpretation methods given in the literature were compared and the effects of nitrogen biostimulation with ammonium and nitrate salts on RQ values of petroleum hydrocarbon biodegradation were investigated. Respirometric reactors were used in bioremediation of diesel fuel–contaminated soils. Ammonium sulfate and potassium nitrate were amended to enhance hydrocarbon biodegradation. Total n-alkane levels in the soils were analyzed after the incubation period. RQ values were calculated based on continuous CO₂ and O₂ measurements. Biostimulation with ammonium and nitrate led to significant contaminant biodegradation. The nitrogen source type affected RQ values significantly. It was concluded that in evaluating hydrocarbon biodegradability properties and interpreting biostimulation properties, the use of graphical RQ evaluation methods that include plotted statistical approaches allows access to more useful information than using individual theoretical RQ values.

Greenhouse gas emissions from paddy soils respond differently to different combinations of crop root residues and N forms. An incubation experiment was carried out to explore the effect of four crop residues (milk vetch, ryegrass, winter wheat, and rape) and four nitrogen treatments (without fertilizer, urea, (NH₄)₂SO₄, and KNO₃) on CH₄, CO₂, and N₂O emissions in a paddy soil. Except in KNO₃ application treatments, CH₄ emissions of milk vetch residue treatments were significantly higher than those of the rest residue treatments. In the presence of milk vetch and ryegrass residues, urea application significantly increased CH₄ emissions in comparison to treatments without fertilizer. Urea significantly promoted CO₂ emissions, whereas (NH₄)₂SO₄ and KNO₃ significantly inhibited CO₂ emissions at all root residue treatments. Urea did not increase N₂O emissions, but (NH₄)₂SO₄ and KNO₃ promoted N₂O emissions at all residue treatments. In addition, KNO₃ had more effects on the increase of N₂O emissions than (NH₄)₂SO₄ in milk vetch-amended soils. Urea addition had no effect on global warming potentials, and (NH₄)₂SO₄ and KNO₃ addition significantly increased global warming potentials at all residue treatments except KNO₃ + winter wheat residue combination. Our results indicated that urea application had no additive effect on global warming when root residues were left in paddy soils, whereas (NH₄)₂SO₄ and KNO₃ application could increase the risk of global warming.

The effects of urea, (NH₄)₂SO₄, KNO₃, and NH₄NO₃ on nitrous oxide (N₂O) emission from soil at field capacity and submerged condition were studied during 120 days in the laboratory. Soils in both moisture regimes gave higher emissions in the beginning, which were reduced later. Total emission of N₂O was higher at submergence as compared to field capacity regardless of fertilizer type. At field capacity soil fertilized with ureaemitted the highest amount of N₂O (1903 μg N₂O-N kg⁻¹ soil) during 120 days while at submerged condition, soil with NH₄NO₃ gave the highest emission (4843 μg N₂O-N kg⁻¹ soil). In another study, the efficacy of seven nitrification inhibitors in reducing the emission of N₂O-N from soil fertilized with urea was tested in the laboratory. Nitrapyrin, 2-amino-4-chloro-6-methylpyrimidine (AM), and dicyandiamide (DCD) reduced the emission to 12, 24, and 63% that of urea, respectively, whereas sodium thiosulphate, sulphur, acetylene,and thiourea had no effect on emission of N₂O. In submerged conditions none of the inhibitors reduced the emission.

The current research outlines the course of eutrophication processes emerging when some critical physical and chemical factors interact altogether. For this purpose, investigations were carried out, where nitrogen [N as (NH₄)₂HPO₄ and KNO₃] and phosphorus [P as (NH₄)₂HPO₄] were added to three different water sources (double distilled water, DDW; tap water, TW; and lacustrine water, LW) and the solutions were incubated at two distinct temperatures (17 and 23 °C). Treatments were kept in 1 dm³ glass jars and the incubation time lasted 7 weeks. The eutrophication process emerged only at 23 °C and was stronger for the lacustrine water (LW). In the case of DDW treatments, this process was observed at N/P = 5.1 and even at 60.0, whereas for the TW, no algal blooming was detected (N/P ratio 17.7–640.0). The lacustrine water (LW) outlined patterns with strong eutrophication at N/P = 4.40, but also at ratios 20.9–71.1. Algal blooming significantly intensified according to LW > TW > DDW but was reversely dependent on the P/N ratios, which followed the range DDW (P/N, 1.6–3.78) > TW (P/N, 0.050–0.100) > LW (P/N, 0.016–0.023). At P = constant (P = 0.10 mg dm⁻³) and the N inputs varying from 0.010 to 2.0 mg dm⁻³, it appeared that the higher the N concentrations, the more intensive the eutrophication process. For N/P ratios, phosphorus regulated for most of the intensity of the process, whereas in the case of P/N, the role of N and P was interchangeable. The main finding of the research is that nitrogen revealed in many cases to be a powerful eutrophication-regulating factor than did phosphorus.