Paracetamol, the most widely and globally used analgesic and antipyretic, is easily accumulated in aquatic environments. In the present study, the biodegradation of paracetamol in different media (one for general growth, one specific for sulfate reducing bacteria, a mineral salts medium and municipal wastewater) inoculated with two types of sludge (from anaerobic lagoon and from oxidation ditch) under different oxygenic conditions (anoxic; moderate oxygenation in open flasks and high oxygenation by aeration) was investigated. In addition, bacteria with relative abundances increasing simultaneously with paracetamol degradation, when this drug was the only carbon source, thus with a putative role in its degradation, were identified using 16S rRNA gene sequences. The results show that aerobic microorganisms had a major role in the degradation of paracetamol, with 50 mg/L totally removed from municipal wastewater after 2 days incubation with aeration, and that the metabolites 4-aminophenol and hydroquinone plus one compound not identified in this work were produced in the process. The identification of bacteria with a role in the degradation of paracetamol revealed a strain from genus Pseudomonas with the highest final relative abundance of 21.2%, confirming previous works reporting strains of this genus as paracetamol decomposers. Besides, genera Flavobacterium, Dokdonella and Methylophilus were also in evidence, with initial relative abundances of 1.66%, 1.48 and 0.00% (not detected) in the inoculum and 6.91%, 3.80 and 3.83% after incubation, respectively. Therefore, a putative role of these genera in paracetamol biodegradation is suggested for the first time.
Irrigation with reclaimed water and soil amendment with sewage sludge are becoming common practices in arid and semiarid areas. When wastewater treatments do not efficiently remove all the contaminants, these contaminants can later end up in agricultural soils. These contaminated soils are a potential source of surface and groundwater pollution by leaching and runoff. In the present work, we assessed the behavior of alcohol sulfates (AS) in agricultural soil. For the experimental work, a tract of soil was irrigated with linear alcohol sulfates with 12–18 hydrocarbon chain and subsequently tested for AS concentration from November 2014 to July 2015. The highest concentrations of AS were found at the top layer of soil (29.80 to 6.23 mg kg?1). The adsorption rate and the amount of surfactant adsorbed increased as the length of the hydrocarbon chain increases. AS homologues can leach up to 60 cm. A mathematical model was applied to predict the environmental behavior of AS in the agricultural soils studied. Disappearance rate constant (k) values for AS homologues were between ?5.10·10?3 and ?1.68·10?2 h?1, and average half-life values were between 37 and 135 h. Coefficients of determination (R2) between 92.4 and 99.1% showed that the proposed model satisfactorily describes the experimental results. The present study provides a conceptual framework and essential parameters for predicting and understanding the environmental behavior of AS in agricultural soils.
In this study, the optimum conditions for the ammonia removal from aqueous solution by microwave-assisted air stripping have been investigated at pH 11. Ammonia solution with five different initial ammonia concentrations was prepared synthetically. The Taguchi method was applied to optimize the ammonia removal conditions. Initial ammonia concentration, air flow rate, temperature, stirring speed, microwave radiation power, and radiation time were defined as the optimization parameters. Experiments were carried out at five different levels for each operational parameter. The results of the experiments revealed that 1800 ppm of initial ammonia concentration, 7.5 L min?1 of air flow rate, 60 °C of temperature, 500 rpm of stirring speed, and 500 W of microwave radiation power for 180 min. of microwave radiation time are optimum conditions for complete ammonia removal. In addition to present experimental data, the optimum operational conditions predicted by the balanced characteristics of orthogonal array were confirmed experimentally. Finally, the effect of optimization parameters was discussed in detail.
Black carbon (BC) is considered to be a promising novel material for controlling organic contaminants due to its strong adsorption property, low production cost, and less secondary pollution. However, seldom systemic research was conducted to investigate adsorption-desorption characteristics and interaction mechanism between BC and nonylphenol (NP), one kind of endocrine-disrupting contaminants (EDCs) and persistent organic pollutants (POPs). Therefore, in the present study, adsorption characteristics of NP on two BCs (rice straw black carbon (RC) and fly ash carbon (FC)) involving adsorption isotherm, kinetics, effect of pH, as well as desorption kinetics, were investigated to explore the feasibility of BC for remediation of NP pollution in a water environment. Adsorption isotherm data showed that Qmax was 61,889.21 ± 2777.68 and 6538.99 ± 606.72 mg/kg and n was 0.39 ± 0.037 and 0.55 ± 0.043 for RC and FC, respectively, suggesting the sorption capacity and nonlinearity of RC to NP is far higher than FC and indicating BC was an effective sorbent for NP pollution control, especially RC. The pH affected BC sorption capacity to NP by influencing the surface properties of BC and the NP speciation together. Desorption kinetics data indicated that more than 80% NP could not be released from both BCs, suggesting that BC could reduce NP releasing risk in a water environment evidently when BC is applied for NP pollution remediation.
Amine-grafted MSU-3 mesoporous silica samples were synthesized from pure and waste silica sources and their CO2 adsorption performances were evaluated. The obtained samples were characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), N2 adsorption–desorption isotherm analysis, Fourier transform infrared (FTIR), and transmission electron microscopy (TEM). CO2 adsorption capacities of the samples at different temperatures were determined by TGA. The amine-modified MSU-3 synthesized from waste exhibited the highest CO2 adsorption capacity of 1.32 mmol/g at 25 °C and 1 bar, depending essentially on the porous texture and the amine content of the material. The CO2 adsorption isotherms of the synthesized samples were measured by a static volumetric method. Adsorption isotherm indicated that the amine-modified samples presented significantly higher CO2 adsorption capacity than the pure samples. The Avrami kinetic model fitted the experimental data well and suggested that complex reaction mechanism or the appearance of multiple reaction pathway occurred in the CO2 adsorption.
Mercury (Hg) is an environmental pollutant which is detrimental to the health of living beings due to the toxicity in its all oxidation states. To control mercury pollution development of low cost, efficient and highly sensitive prototype mercury sensor remains a challenge. In the present work, we have proposed a low-cost prototype device based on silver nanoparticle-impregnated poly(vinyle alcohol) (PVA-Ag-NPs) nanocomposite thin film for mercury detection. The thin film, fabricated through a facile protocol, is shown to be a fast, efficient, and selective sensor for Hg2+ in aqueous medium with a detection limit of 10 ppb. We have utilized the aggregation and amalgamation of Ag-NPs with Hg2+ to develop the low-cost, highly efficient and feasible prototype mercury sensor. In the presence of Hg2+, the yellowish thin film turned into colourless due to the loss of intense surface plasmon resonance (SPR) absorption band of the silver nanoparticles (Ag-NPs) through aggregation and amalgamation with mercury. The developed sensor has high selectivity for Hg2+ ions over a wide range of other competing heavy metal ions, generally present in water of natural sources. The sensor response is found to be linear over the Hg2+ ion concentration regime from 10 ppb to 5 ppm. The developed sensor has shown to determine a trace Hg2+ ions in real water samples. Finally, using the proposed technique, we have developed a simple and inexpensive prototype device for monitoring in field environmental mercury pollution.
Developing urbanization, water shortage, watercourse pollution, and demands for more food due to population growth require a more efficient water irrigation and fertilizer application. Retaining nutrients and water in agricultural soils brings about higher crop yields and prevents pollution of water courses. Among different solutions, zeolites, which are environmental friendly, ubiquitous, and inexpensive, have been extensively employed in agricultural activities. These minerals are considered as soil conditioners to improve soil physical and chemical properties including infiltration rate, saturated hydraulic conductivity (Ks), water holding capacity (WHC), and cation exchange capacity (CEC). Natural and surface-modified zeolites can efficiently hold water and nutrients including ammonium (NH4+), nitrate (NO3?) and phosphate (PO43?), potassium (K+), and sulfate (SO42?) in their unique porous structures. Their application as slow-release fertilizers (SRFs) are reported as well. Therefore, zeolite application can improve both water use efficiency (WUE) and nutrient use efficiency (NUE) in agricultural activities and consequently can reduce the potential of surface and groundwater pollution. This review paper summarizes findings in the literature about the impact of zeolite applications on water and nutrient retention in the agriculture. Furthermore, it explores benefits and drawbacks of zeolite applications in this regard.
A bioadsorbent formulated with a secondary raw material, consisting of grape marc, subjected to a bioxidize process and entrapped in calcium alginate beads, was used for the desalination of water containing copper(II) sulfate. Experiments were established under different experimental conditions varying the concentration of contaminant, the amount of bioadsorbent, and the extraction time through response surface methodology. The most significant variable in the removal of copper(II) sulfate was the amount of bioadsorbent employed, followed by the extraction time; whereas, the adsorbent capacity was more influenced by the amount of contaminant and the amount of bioadsorbent used. At the highest concentration of copper(II) sulfate (0.15 mol/L), the equations obtained predict that the bioadsorbent has a capacity of 2785 mg/g and produces a copper(II) removal about 43% using low adsorbent/water ratios, 1:10 (v/v), and maximum extraction times; whereas, it would remove 97.2% of copper(II) sulfate in 5 min, using adsorbent/water ratios close to 1:2 (v/v), with capacity values, in this case, around 1800 mg/g. The encapsulation of the bioxidize adsorbent increased its capacity to 30% and allowed the precipitation of sulfate ions as calcium sulfate. The results obtained in this work could presume advances for promoting the industrial symbiosis between winery and environmental industries.
Graphical abstract Utilization of secondary raw material, consisting of bioxidize grape marc from winery industry, as bioadsorbent encapsulated in calcium alginate beads, for the removal of copper(II) sulfate from water
In this work, disks containing different amount of the TiO2 precursor impregnated on the raw red clay were produced. The disks were obtained by pressing in metal template and subsequently calcined at 500 °C. The raw clay was used as rigid support to fix the TiO2. The materials were characterized by X-ray diffraction, diffuse reflectance spectroscopy, N2 adsorption-desorption (BET and BJH), scanning electron microscopy, and Fourier transform infrared (FTIR) spectroscopy. The ability of disks to produce superoxide and hydroxyl radicals after photoexcitation with UV irradiation was monitored by EPR. The catalytic efficiency was evaluated by the Reactive Red 141 dye discoloration under artificial UV light and sunlight. The reaction parameters such as concentration of RR-141 and irradiation source were evaluated. The results showed that the disks were able to decolorize 97.5% under sunlight at 60 min. The disks were also efficient in the discoloration until the tenth cycle, resulting in discoloration values near the initial cycles. Additionally, the dye fragments produced in cleavage of molecule during the reaction were evaluated by LC/MS-MS.
This study predicts the optimal landfarming period for the total petroleum hydrocarbons (TPHs)-contaminated field soils that are subject to the combined landfarming and Fenton oxidation treatment.
Materials and methods
The TPHs degradation in the artificially contaminated model soils and the field-aged contaminated soils were compared in a laboratory scale. The soils were bioaugmented with the 16 petroleum hydrocarbon-degrading microbial cultures that are commercially available in Korea.
Results and discussion
The TPHs degradation by bioaugmentation in the model soils was 81?±?2% after 56 days, while it was only 27?±?2% after 74 days in the field-aged soils. The lower degradation in the field-aged soils can be attributed to the removal of a large part of the biodegradable and volatile TPHs fractions during the weathering process. The two-compartment model that can depict a fast-degradation phase followed by a slow-degradation phase predicted that the remedial goal of 475 mg kg?1 of TPHs could be achieved in the model soils within the conventional landfarming period of 60–120 days in Korea; however, the predicted period for the field-aged soils (710–4,086 days) was not practical requiring a combined biological and chemical treatment approach. Based on the kinetics study, the optimal landfarming period for the field-aged soils was 3 weeks and pre-Fenton oxidation can be used to meet the remedial goal.
Conclusions
The two-compartment model can be useful for predicting landfarming period for the combined landfarming and Fenton oxidation treatment of field-aged TPHs contaminated soils. The prediction of the optimal landfarming period could lead to the reduction in both the treatment cost and period. 相似文献
Effects of graphene oxide (GO) on phosphorus removal characteristics and mechanisms of aerobic granular sludge (AGS) were investigated in controlled batch tests. The scanning electron microscope (SEM) image results showed that the surface of AGS appeared wrinkled with coccus and bacillus brevis being wizened and the fungal mycelium being cut into pieces in AGS with 0.06 g/L GO. The anaerobic and aerobic batch tests suggested that the net phosphorus uptake of AGS was 2.60 mg/L for AGS with GO, compared with the value (4.38 mg/L) without GO, and the maximum release and uptake phosphorus rates also remarkably decreased. Intracellular and extracellular phosphorus contents were reduced to 64.67 and 19.74% of that without GO, indicating the nanoparticle might have great effects on extracellular phosphorus. The standards, measurements, and testing (SMT) analysis suggested that the inorganic phosphorus (IP) and organic phosphorus (OP) content decreased compared with the values without GO. The summation of phosphorus fraction associated with Ca (Ca-P) and the phosphorus fraction associated with Al, Fe, and Mn (Fe/Al-P) were 82.09% (without GO) and 94.27% (with GO), suggesting the presence of GO resulted in the decrease of content and species of IP. The extracellular polymeric substances (EPS) were reduced from 173.68 mg/g MLVSS to 137.55 mg/g MLVSS when AGS contacted with GO. The results of this assay had uncovered that 0.06 g/L GO could inhibit the bioactivity of phosphorus-accumulating organisms (PAOs), which resulted in the decrease of Ca-P, Fe/Al-P, and OP. EPS played an essential role on the phosphorus removal and granular stability. The decrease of EPS, which was produced by microorganisms, was contributed to decrease of extracellular phosphorus. This study provided an extensive insight into the influence of GO on phosphorus removal mechanism by AGS.
Calix[4]arene-crown-6 compounds are promising ligands in the removal of cesium. With this aim, a macrocyclic compound, calix[4]arene-crown-6, was chemically immobilized onto inorganic ordered mesoporous carbon material. Several adsorption parameters such as nitric acid concentration, contact time, initial cesium content, operation temperature, and competing ions were studied. The results demonstrated the prepared material conserved high cesium selectivity of calix[4]arene-crown-6 and physicochemistry stability of the ordered mesoporous carbon matrix and showed the superior cesium adsorption performance. The optimum adsorption acidity determined as 3.0 M nitric acid was consistent with the actual acidity value in the back-end of the nuclear fuel cycle. The Langmuir model indicated the monolayer coverage adsorption and the highest mass adsorption capacity was calculated as 128.06 mg cesium/g. The pseudo-second-order model and D-R model proved the adsorption was a chemical process. Thermodynamics parameters showed the adsorption was spontaneous and exothermal in nature. Competing ions hardly affected cesium adsorption. Furthermore, the adsorbent showed almost intact adsorption capacity after five adsorption-elution cycles. The comprehensive performance highlights the composite material as a promising adsorbent for cesium adsorption from wastewaters.
Although dilution of lake water has been used for improvement of water quality and algal blooms control, it has not necessarily succeeded to suppress the blooms. We hypothesized that the disappearance of algal blooms by dilution could be explained by flow regime, nutrient concentrations, and their interaction. This study investigated the effects of daily renewal rate (d), nitrogen (N) and phosphorus (P) concentration, and their interaction on the domination between Microcystis aeruginosa and Cyclotella sp. through a monoxenic culture experiment. The simulation model as functions of the N:P mass ratio and dilution rate (D) (calculated from d) was constructed, and the dominant characteristics of both species were predicted based on the model using parameters obtained in a monoculture experiment and our previous study. Results of monoxenic culture experiment revealed that M. aeruginosa dominated in all conditions (d = 5 or 15%; N = 1.0 or 2.5 or 5.0 mg-N L?1; P = 0.1 or 0.5 mg-P L?1) and the predicted cell densities were substantially correspondent to experimental data. Under various N:P ratios and D values, characteristics of domination for each species were predicted, indicating that Cyclotella sp. tended to be dominant under high P concentrations (P ≥ 0.36 mg-P L?1) when the N:P ratio was less than 7.0, and M. aeruginosa could not form algal blooms at the N:P ratio ≤ 7.0 (N ≤ 0.7 mg-N L?1). It was also suggested that the dilution rate leading to the Cyclotella sp. domination required 0.20 day?1 or higher regardless of the N:P ratios.
Graphical Abstract? M. aeruginosa and Cyclotella sp. could be a superior competitor in nutrient-limited and nutrient-rich conditions, respectively. ? The simulation model in this study indicated that the predicted cell density and nutrient concentration were substantially correspondent to experimental data. ? The model predicted that Cyclotella sp. tended to be dominant at the P ≥ 0.36 mg-P L?1 when the N:P ratio was less than 7.0, and M. aeruginosa could not form algal blooms at the N:P ratio ≤ 7.0 (N ≤ 0.7 mg-N L?1).
To investigate the effect of permeable pavement surface materials (PPSMs) on the influences of pollutant removal in urban storm runoff, six commonly used PPSMs (porous asphalt, porous concrete, cement brick, ceramic brick, sand base brick, and shale brick) were selected and the research was carried out by batch and column experiments. Results indicated that in batch experiments, except for the shale brick, most of the PPSM will release different pollutants continuously with the contact time increasing. Compared with other materials, porous asphalt and ceramic brick could increase the concentration of pollutants in the runoff greatly. With the contact time increased to 48 h, the concentration of NO3-N and TN increased to 13.0 and 23.1 mg/L for ceramic brick and 13.3 and 32.3 mg/L for porous asphalt, respectively. This is mainly due to the artificial activity that accelerates the wear of the PPSM. Furthermore, results showed that PPSM could eliminate pollutants and influenced the removal efficiency greatly in column experiments. Most PPSMs have a noticeable purification effect on different pollutants, among them the purification effect of porous asphalt is the best. The concentrations of COD, NH3-N, and TN are 139.6, 1.32, and 7.79 mg/L in the effluent, respectively. These results may be attributed to the relatively stable environment in column experiments which is more suitable for the removal of pollutants. This study could offer new insight into the transformation of pollutants in damaged PPSM and provide useful guidelines for the better design of permeable pavement system.
Heavy metals are a common contaminant in water supplies and pose a variety of serious health risks to nearby human populations. A promising approach to heavy metal decontamination is the sequestration of heavy metal ions in porous materials; however, current technologies involve materials which can be difficult to synthesize, are high-cost, or are themselves potentially toxic. Herein, we demonstrate that rapidly synthesized calcium carbonate (CaCO3) microparticles can effectively remove high quantities of Pb2+, Cd2+, and Cu2+ ions (1869, 1320, and 1293 mg per gram of CaCO3 microparticles, respectively) from aqueous media. The CaCO3 microparticles were characterized with powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Brunauer–Emmett–Teller (BET) N2 sorption–desorption. It was found that the Ca2+ ions of the microparticles were replaced by the heavy metal ions, leading to partially recrystallized nanoparticles of new compositional phases such as cerussite (PbCO3). The adsorption, surface dissolution/re-precipitation, and nucleation/crystal growth mechanisms were determined by investigating the Ca2+ released, along with the changes to particle morphology and crystal structure. Importantly, this study demonstrates that the porous CaCO3 microparticles performed well in a system with multiple heavy metal ion species: 100% of Cu2+, 97.5% of Pb2+, and 37.0% Cd2+ were removed from an aqueous solution of all cations with initial individual metal concentrations of 50 mg/L and 1.5 g/L of CaCO3 microparticles. At this concentration, the CaCO3 microparticles significantly outperformed activated carbon. These results help to establish CaCO3 microparticles as a promising low-cost and scalable technology for removing heavy metal ions from contaminated water.
Ozonation is an efficient process for the primary degradation of most substrates but not for their mineralisation. In this work, the ozonation enhanced with the addition of H2O2 was studied for two substrates with very different oxidation resistances: the dye rhodamine 6G (R6G) and the surfactant linear alkylbenzene sulfonate (LAS). With O3 only, the primary degradation of R6G was completed in less than 10 min but its TOC removal only reached 45% in 1 h. By adding H2O2, TOC removal was increased to 70% with a molar ratio (mol H2O2/mol substrate) of 10. The analysis of pH decrease served to define the specific basicity loss (SBL). The optimum conditions for the R6G mineralisation were found to be associated with a SBL value between 1 and 10 ((min/g)/L)?1, through an adequate addition of H2O2. Moreover, in the case of LAS, the addition of H2O2 for a greater efficiency should occur after the foaming period, above all formed at acid pH. LAS degradation was also considerably improved, and the optimum for primary degradation achieved in 10 min with a TOC removal of over 65% with a molar ratio (mol H2O2/mol substrate) of 20.
This study presents a combination of dispersive liquid-liquid-solidified floating organic drop microextraction (DLLSFODM) and slotted quartz tube (SQT) with conventional flame atomic absorption spectrometry (FAAS) to improve the sensitivity for cadmium determination. A ligand namely 2-(4-methylphenyl)-1H-imidazo-[4,5-f]-[1,10]-phenanthroline which has not been used in trace analyte determination was used to form a cadmium complex. Stepwise optimization of parameters affecting complex formation (pH, ligand, and buffer solution) and extraction (extraction and dispersive solvents, salt effect and mixing) was done to maximize cadmium absorbance. The slotted quartz tube was fitted onto the flame burner and optimized to increase residence time of atoms in the flame. Instrumental parameters such as sample and fuel flow rate were also optimized to further enhance the absorbance signal for cadmium. Using optimal parameters and values, the limits of detection and quantification were determined to be 0.81 and 2.69 μg L?1, respectively. Low percent relative standard deviations (<?6.0%) indicated good precision for both extraction and instrumental measurements. Recovery tests were used to determine the accuracy of the method and the recovery results obtained were between 88 and 113%.
Bisphenol A (BPA) and reactive black 5 (RB5) dye are among the most persistent and non-biodegradable contaminants in water which require an urgent need for the development of effective removal method. The ubiquitous existence of both contaminants could interfere with the human health and aquatic environmental balance. Photocatalytic process as one of advanced oxidation processes (AOPs) has shown high performance for degradation of organic compounds to the harmless materials under sensible condition. Therefore, this study aims to develop a visible-light-driven photocatalyst that can efficiently degrade BPA and RB5 present in household water. N-doped TiO2 were successfully synthesized via simple and direct sol–gel method. The prepared TiO2 nanoparticles were characterized by field emission scanning microscope (FE-SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Brunauere Emmette Teller (BET) analysis. The incorporation of nitrogen in TiO2 lattice exhibited excellent optical responses to visible region as revealed by UV–Vis–NIR spectroscopy absorption capability at 400–600 nm. The photocatalytic activity of the N-doped TiO2 nanoparticles was measured by photocatalytic degradation of BPA and RB5 in an aqueous solution under visible-light irradiations. Degradation of BPA and RB5 was 91.3% and 89.1%, respectively after 360 min illumination. The degradation of BPA and RB5 by N-doped TiO2 was increased up to 89.8% and 88.4%, respectively under visible-light irradiation as compared to commercial TiO2 P25. This finding clearly shows that N-doped TiO2 exhibits excellent photocatalytic degradation of BPA and RB5 under visible irradiation, hence have a promising potential in removing various recalcitrant contaminants for water treatment to fulfill the public need to consume clean water.
Biosorbents are the natural origin adsorbents, which popularity in environmental engineering is steadily increasing due to their low price, ease of acquisition, and lack of the toxic properties. Presented research aimed to analyze the possibility of chemical modification of the straw, which is a characteristic waste in the Polish agriculture, to improve its biosorption properties with respect to removal of selected metals from aquatic solutions. Biosorbents used during the tests was a barley straw that was shredded to a size in the range of 0.2–1.0 mm. The biosorption process was performed for aqueous solutions of zinc at a pH 5. Two different modifications of straw were analyzed: esterification with methanol and modification using the citric acid at elevated temperature. The results, obtained during the research, show a clear improvement in sorption capacity of the straw modified by the citric acid. In the case of straw modified with methanol, it has been shown that the effectiveness of zinc biosorption process was even a twice lower with respect to the unmodified straw. Moreover, it was concluded that the removal of analyzed metals was based mainly on the ion-exchange adsorption mechanism by releasing a calcium and magnesium ions from the straw surface to the solution.
Irrigation and fertilization can change soil environment, which thereby influence soil microbial metabolic activity (MMA). How to alleviate the adverse effects by taking judicious saline water irrigation and fertilization regimes is mainly concerned in this research.
Materials and methods
Here, we conducted a field orthogonal designed test under different saline water irrigation amount, water salinity, and nitrogen fertilizer application. The metabolic profiles of soil microbial communities were analyzed by using the Biolog method.
Results and discussion
The results demonstrated that irrigation amount and fertilizer application could significantly change MMA while irrigation water salinity had no significant effect on it. Medium irrigation amount (30 mm), least (50 kg ha?1) or medium (350 kg ha?1) N fertilizer application, and whatever irrigation water salinity could obtain the optimal MMA. Different utilization rates of carbohydrates, amino acids, carboxylic acids, and polymers by soil microbial communities caused the differences of the effects, and D-galactonic acid γ-lactone, L-arginine, L-asparagine, D-glucosaminic acid, Tween 80, L-threonine, and D-galacturonic acid were the indicator for distinguishing the effects.
Conclusions
The results presented here demonstrated that by regulating irrigation water amount and fertilizer application, the effects of irrigation salinity on MMA could be alleviated, which offered an efficient approach for guiding saline water irrigation.
