The agricultural sector uses fertilizers such as urea to add more nutrients to the soil needed for plant growth. Although it is cost-effective in crop production, indiscriminate use of nitrate-based fertilizer may result in behavioural, morphological, and physiological alterations on non-target organisms. This study determined the angiogenesis activity in the chorioallantoic membrane of urea-exposed duck embryos. It also investigated the weight, morphometries, and liver histopathology to gather more information on urea fertilizer's toxicity. It was observed that urea promoted angiogenesis in the CAM of duck embryos, especially at higher concentrations (P<0.05). Embryos treated with urea resulted in an alteration of the head-beak length (P<0.05). However, weight, crown-rump length, forelimb length, and hind limb length were not affected. The developing liver of urea-treated embryos showed distortion of the central vein shape and had larger sinusoidal spaces. The presence of Kupffer cells and lipid droplets were observed in the treated section. Congestion of blood cells, haemorrhage, and necrosis of hepatocytes were also observed in the tissue suggesting the extent of damage caused by the fertilizer. The findings of this study showed multiple developmental effects of urea on duck embryos. Further investigations are needed to shed more light on the toxicity of urea fertilizer on vertebrates.

Coastal waters are confluences receiving large amounts of point and non-point sources of pollution. An attempt was made to explore microbial community interactions in response to carbon, nitrogen and metal pollution. Additionally, experiments were designed to analyze the influence of these factors on horizontal gene transfer (HGT). Shift in bacterial diversity dynamics by arsenic stress and nutrient addition in coastal waters was explored by metagenomics of microcosm setups. Phylogenetic analysis revealed equal distribution of Gammaproteobacteria (29%) and Betaproteobacteria (28%) in control microcosm. This proportional diversity from control switched to unique distribution of Gammaproteobacteria (44.5%)> Flavobacteria (17.7%)> Bacteriodia (11.92%)> Betaproteobacteria (11.52%) in microcosm supplemented with carbon, nitrogen and metal (C + N + M). Among metal-stressed systems, alpha diversity analysis indicated highest diversity of genera in C + N + M followed by N + M > C+M> metal alone. Arsenic and ampicillin sensitive E. coli XL1 blue and environmental strains (Vibrio tubiashii W85 and E. coli W101) were tested for efficiency of uptake of plasmid (P) pUCminusMCS (arsBᴿampᴿ) under varying stress conditions. Transformation experiments revealed that combined effect of carbon, nitrogen and metal on horizontal gene transfer (HGT) was significantly higher (p < 0.01) than individual factors. The effect of carbon on HGT was proved to be superior to nitrogen under metal stressed conditions. Presence of arsenic in experimental setups (P + M, P + N + M and P + C + M) enhanced the HGT compared to non-metal counterparts supplemented with carbon or nitrogen. Arsenic resistant bacterial isolates (n = 200) were tested for the ability to utilize various carbon and nitrogen substrates and distinct positive correlation (p < 0.001) was found between arsenic resistance and utilization of urea and nitrate. However, evident positive correlation was not found between carbon sources and arsenic resistance. Our findings suggest that carbon and nitrogen pollution in aquatic habitats under arsenic stress determine the microbial community dynamics and critically influence uptake of genetic material from the surrounding environment.

Ammonia (NH₃) volatilized from soils plays an important role in N cycle and air pollution, thus it is important to trace the emission source and predict source contributions to development strategies mitigating the environmental harmful of soil NH₃ volatilization. The measurements of ¹⁵N natural abundance (δ¹⁵N) could be used as a complementary tool for apportioning emissions sources to resolve the contribution of multiple NH₃ emission sources to air NH₃ pollution. However, information of the changes of δ¹⁵N–NH₃ values during the whole volatilization process under different N application rates are currently lacking. Hence, to fill this gap, we conducted a 15-day incubation experiment included different urea-N application rates to determine δ¹⁵N values of NH₃ during volatilization process. Results showed that volatilization process depleted ¹⁵N in NH₃. The average δ¹⁵N value of NH₃ volatilized from the 0, 20, 180, and 360 kg N ha⁻¹ treatment was −16.2 ± 7.3‰, −26.0 ± 5.4‰, −34.8 ± 4.8‰, and −40.6 ± 5.7‰. Overall, δ¹⁵N–NH₃ values ranged from −46.0‰ to −4.7‰ during the whole volatilization process, with lower in higher urea-N application treatments than those in control. δ¹⁵N–NH₃ values during the NH₃ volatilization process were much lower than those of the primary sources, soil (−3.4 ± 0.1‰) and urea (−3.6 ± 0.1‰). Therefore, large isotopic fractionation may occur during soil volatilization process. Moreover, negative relationships between soil NH₄⁺-N and NH₃ volatilization rate and δ¹⁵N–NH₃ values were observed in this study. Our results could be used as evidences of NH₃ source apportionments and N cycle.

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.

Bio-stimulation of the indigenous microbial community is considered as an effective strategy for the bioremediation of polluted environments. This examination explored the near effects of various bio-stimulants on pyrene degradation, prokaryotic community compositions, and functions using 16S rRNA amplicon sequencing and qPCR. At first, the results displayed significant differences (p < 0.05) between the prokaryotic community structures of the control group, PYR (contains pyrene only), and bio-stimulants amended groups. Among the bio-stimulants, biochar, oxalic acid, salicylate, NPK, and ammonium sulfate augmented the pyrene degradation potential of microbial communities. Moreover, the higher abundance of genera, such as Flavobacterium, Hydrogenophaga, Mycobacterium, Rhodococcus, Flavihumibacter, Pseudomonas, Novosphingobium, etc., across the treatments indicated that these genera play a vital role in pyrene metabolism. Based on the higher abundance of GP-RHD and nidA genes, we speculated that Gram-positive prokaryotic communities are more competent in pyrene dissipation than Gram-negative. Furthermore, the marked abundance of nifH, and pqqC genes in the NPK and SA treatments, respectively, suggested that different bio-stimulants might enrich certain bacterial assemblages. Besides, the significant distinctions (p < 0.05) between the bacterial consortia of HA (humic acid) and SA (sodium acetate) groups from NPK, OX (oxalic acid), UR (urea), NH4, and SC (salicylate) groups also suggested that different bio-stimulants might induce distinct ecological impacts influencing the succession of prokaryotic communities in distinct directions. This work provides new insight into the bacterial degradation of pyrene using the bio-stimulation technique. It suggests that it is equally important to investigate the community structure and functions along with studying their impacts on degradation when devising a bio-stimulation technology.

(S,S)-ethylenediaminedisuccinic acid (EDDS) has a strong capacity to mobilize potentially toxic elements (PTEs) in phytoextraction. It can release NH₄⁺-N via biodegradation, which can enhance N supply to soil thereafter promote plant growth and plant resistance to PTEs. However, the advanced feature of released N in the EDDS-enhanced phytoextraction remains unclear. In the current study, the effects of N supply released from EDDS on ryegrass phytoextraction and plant resistance to PTEs were investigated in detail by a comparison with urea. Our results supported that the addition of both EDDS and urea increased N concentration in soil solution, yet EDDS needed more time to release available N for plant uptake and transported more N from root to shoot. Additionally, EDDS significantly increased the concentration of all targeted PTEs, i.e. Cu, Zn, Cd, and Pb, in the soil solution, which results in higher levels of their occurrence in plant biomass compared with urea. By contrast, the supply of N slightly enhanced the ryegrass uptake of micro-nutrients, i.e. Cu and Zn, yet it caused negligible effects on nonessential elements, i.e. Cd and Pb. The mobilized PTEs by EDDS lead to elevated oxidative stress because higher levels of malondialdehyde and O₂•⁻ were observed. The supply of N attenuated oxidative stress caused by O₂•⁻ and H₂O₂, which was associated with enhanced activities of superoxide dismutase and peroxidase. Our results advanced the understanding of the exogenous N supply and metal resistance mechanisms in the EDDS-enhanced phytoextraction. This study also highlighted that EDDS can serve as a N source to ease N-deficient problems in PTEs-contaminated soils.

Evaluation of the effectiveness of best management practices for reducing nitrate leaching in agricultural systems requires detailed water and nitrogen (N) budgets. A 3-year field experiment using 15 auto-weighing lysimeters was set up to quantify nitrate leaching, crop evapotranspiration (ET), and N and water use efficiencies within an intensive wheat-maize rotation system in the Northern China Plain. The lysimeter consists mainly of the following: (1) high-resolution weighing cells; (2) ceramic solution samplers for soil solutions collection; and (3) circular stainless steel leaching trays for collecting seepage water. Two N fertilizer types were applied at two rates (150 and 225 kg N hm⁻² for each crop) with no-N applied as the control. The N fertilizer types were monotypic un-coated urea and a blend product with controlled-release urea (CRU) and un-coated urea. The results indicate that when compared with un-coated urea at the same application rate, the blend product greatly improved water and N use efficiencies with significant increase in yields and crop ET as well as reduction of nitrate accumulation and leaching in the soil profile (p < 0.05). This was mostly because the blend product consistently supplied N to meet crop demands over the entire growth season. The study implied that effective best management practices to control nitrate leaching should be based on technically sound fertilization and irrigation schemes in terms of timing, rate, and fertilizer type to suit site specific conditions.

The emergence of organophosphorus flame retardants and the efficient removal from aquatic environments have aroused increasing concerns. The Urea functionalized Fe₃O₄@LDH (Urea-Fe₃O₄@LDH) was prepared and used to adsorb triphenyl phosphate (tphp) for the first time. The tphp adsorption capacity was up to 589 mg g⁻¹, and the adsorption rate reached 49.9 mg g⁻¹ min⁻¹. Moreover, the influences of various environmental factors (pH, ionic strength and organic matter) on the tphp adsorption on the Urea-Fe₃O₄@LDH were investigated. The initial pH of the solution significantly affected the tphp adsorption, whereas the ionic strength and HA slightly affected the adsorption. The main adsorption mechanism was attributed to electrostatic interaction and π-π interaction. We believe that urea is one of excellent functional groups for the tphp adsorption removal and the materials with urea groups as the adsorbents exhibit good prospects in the future.

Here, we report on a two-years field experiment aimed at the quantification of the emissions of nitrous oxide (N2O) and methane (CH4) from the dominant wheat–maize double cropping system in North China Plain. The experiment had 6 different fertilization strategies, including a control treatment, recommended fertilization, with and without straw and manure applications, and nitrification inhibitor and slow release urea. Application of N fertilizer slightly decreased CH4 uptake by soil. Direct N2O emissions derived from recommended urea application was 0.39% of the annual urea-N input. Both straw and manure had relatively low N2O emissions factors. Slow release urea had a relatively high emission factor. Addition of nitrification inhibitor reduced N2O emission by 55%. We conclude that use of nitrification inhibitors is a promising strategy for N2O mitigation for the intensive wheat–maize double cropping systems.

In this study the influence of environmental conditions, most likely prevailing in filter beds used for intermittently discharged pollutant streams such as landfill leachate and storm water, on the stability of the heavy metal–filter complex was investigated for 2 filter materials; non-treated and urea treated pine bark, using leaching experiments. The metal–filter complex stability was higher for urea treated than for non-treated pine bark and dependent on the metal adsorbed. The type of environmental condition applied was of less importance for the extent of leaching.