The adsorption of urea nitrogen onto chitosan coated dialdehyde cellulose (CDAC) under catalysis of immobilized urease in gelatin membrane (IE) was studied in batch system. The pseudo first-order and second-order kine...The adsorption of urea nitrogen onto chitosan coated dialdehyde cellulose (CDAC) under catalysis of immobilized urease in gelatin membrane (IE) was studied in batch system. The pseudo first-order and second-order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. The experimental data fitted well to the second-order kinetic model.展开更多
Summary： The effects of oligosaccharide and creatine （Cr） supplementation on glucose, lactic acid and urea nitrogen levels in blood and activity of serum creatine kinase （CK） were explored. Twenty CUBA male athle...Summary： The effects of oligosaccharide and creatine （Cr） supplementation on glucose, lactic acid and urea nitrogen levels in blood and activity of serum creatine kinase （CK） were explored. Twenty CUBA male athletes were divided into 4 groups： group A （supplementation of Cr alone）, group B （supplementation of oligosaccharide）, group C （supplementation of oligosaccharide and Cr） and group D （placebo control group）. By using orthogonal L4 table （2a ）, the experiment was performed. There were factors including oligosaccharide （carbohydrate, CHO）, Cr and their correlation. Each factor had two levels： supplementation and no-supplementation. The results showed that the supplementation of CliO or Cr alone, combined supplementation of CHO and Cr could significantly reduce the glucose, urea nitrogen levels in blood and serum CK activity after competition in the athletes. Moreover, the effects of combined supplementation of CHO and Cr were more satisfactory. It was concluded that supplementation of CliO and Cr could promote the recovery of physical performance and athletic abilities after athletics in basketball athletes.展开更多
The urea nitrogen adsorbent of complex type, which consists of chitosan coated dialdehyde cellulose （CDAC） and immobilized urease in gelatin membrane （IE）, was prepared. The cellulose, the dialdehyde cellulose （...The urea nitrogen adsorbent of complex type, which consists of chitosan coated dialdehyde cellulose （CDAC） and immobilized urease in gelatin membrane （IE）, was prepared. The cellulose, the dialdehyde cellulose （DAC） and the CDAC were characterized by scanning electronic microscope. The results indicate that the cellulose C2-C3 bond was broken under the oxidation of periodate and it was oxidated to DAC. The DAC was coated with chitosan and the CDAC was obtained. The adsorption of urea nitrogen onto the adsorbent in Na2HPO4-NaH2PO4 buffer solution was studied in batch system. The effects of the experiment parameters, including degree of oxidation of CDAC, initial urea nitrogen concentration, pH and temperature, on the adsorption capacity of urea nitrogen onto the adsorbent at CDAC/IE weight ratio 10：1 were investigated. The results indicate that these parameters affected significantly the adsorption capacity. The adsorption capacity of urea nitrogen onto the adsorbent was 36.7 mg/g at the degree of oxidation of CDAC 88%, initial urea nitrogen concentration 600 mg/L, pH 7.4 and temperature 37℃.展开更多
AIM: To examine characteristics of patients with blood urea nitrogen(BUN) levels higher and lower than the normal limit.METHODS: Patient records between April 2011 and March 2014 were analyzed retrospectively. During ...AIM: To examine characteristics of patients with blood urea nitrogen(BUN) levels higher and lower than the normal limit.METHODS: Patient records between April 2011 and March 2014 were analyzed retrospectively. During this time, 3296 patients underwent upper endoscopy. In total, 50 male(69.2 ± 13.2 years) and 26 female(72.3 ± 10.2 years) patients were assessed. Patients were divided into two groups based on BUN levels: higher than the normal limit(21.0 mg/d L)(H) and lower thanthe normal limit(L). One-way analysis of variance was performed to reveal differences in the variables between the H and L groups. Fisher's exact test was used to compare the percentage of patients with gastric ulcer or gastric cancer in the H and L groups.RESULTS: White blood cell count was higher in the H group than in the L group(P = 0.0047). Hemoglobin level was lower in the H group than in the L group(P = 0.0307). Glycated hemoglobin was higher in the H group than in the L group(P = 0.0264). The percentage of patients with gastric ulcer was higher in the H group(P = 0.0002). The H group contained no patients with gastric cancer.CONCLUSION: Patients with BUN ≥ 21 mg/d L might have more severe upper gastrointestinal bleeding.展开更多
Near-infrared (NIR) spectroscopy combined with chemometrics methods was applied to the rapid and reagent-free analysis of serum urea nitrogen (SUN). The mul-partitions modeling was performed to achieve parameter stabi...Near-infrared (NIR) spectroscopy combined with chemometrics methods was applied to the rapid and reagent-free analysis of serum urea nitrogen (SUN). The mul-partitions modeling was performed to achieve parameter stability. A large-scale parameter cyclic and global optimization platform for Norris derivative filter (NDF) of three parameters (the derivative order: d, the number of smoothing points: s and the number of differential gaps: g) was developed with PLS regression. Meantime, the parameters’ adaptive analysis of NDF algorithm was also given, and achieved a significantly better modeling effect than one without spectral pre-processing. After eliminating the interference wavebands of saturated absorption, the modeling performance was further improved. In validation, the root mean square error (SEP), correlation coefficient (RP) for prediction and the ratio of performance to deviation (RPD) were 1.66 mmol?L-1, 0.966 and 4.7, respectively. The results showed that the high-precision analysis of SUN was feasibility based on NIR spectroscopy and Norris-PLS. The global optimization method of NDF is also expected to be applied to other analysis objects.展开更多
Background：As a major complication after orthotopic liver transplantation （OLT）,the occurrence of acute kidney injury （AKI） is frequently defined by serum creatinine （Cr）;however,the accuracy of commonly used b...Background：As a major complication after orthotopic liver transplantation （OLT）,the occurrence of acute kidney injury （AKI） is frequently defined by serum creatinine （Cr）;however,the accuracy of commonly used blood urea nitrogen （BUN）,uric acid （UA）,and β2-microglobulin （β2-MG） remains to be explored.This retrospective study compared the accuracy of these parameters for post-OLT AKI evaluation.Methods：Patients who underwent OLT in three centers between July 2003 and December 2013 were enrolled.The postoperative AKI group was diagnosed by the Kidney Disease Improving Global Outcomes （KDIGO） criteria and classified by stage.Measurement data were analyzed using the t-test or Wilcoxon rank-sum test;enumerated data were analyzed using the Chi-square test or Fisher＇s exact test.Diagnostic reliability and predictive accuracy were evaluated using receiver operating characteristic （ROC） curve analysis.Results：This study excluded 976 cases and analyzed 697 patients （578 men and 1 1 9 women）;the post-OLT AKI incidence was 0.409.Compared with the no-AKI group,the AKI group showed very significant differences in Model for End-stage Liver Disease score （14.74 ± 9.91 vs.11.07 ± 9.54,Z =5.404;P ＜ 0.001）,hepatic encephalopathy （45 [15.8％] vs.30 [7.3％],x2 =12.699;P ＜ 0.001）,hemofiltration （28 [9.8％] vs.0 [0.0％],x2 =42.171;P ＜ 0.001）,and 28-day mortality （23 [8.1％] vs.9 [2.2％],x2 13.323;P ＜0.001）.Moreover,mean values of Cr,BUN,UA,and β2-MG in the AKI group differed significantly at postoperative days 1,3,and 7 （all P ＜0.001）.ROC curve area was 0.847 of Cr for the detection of AKI Stage 1 （sensitivity 80.1％,specificity 75.7％,cutoffvalue 88.23 μmol/L）,0.916 for Stage 2 （sensitivity 87.6％,specificity 82.6％,cutoff value 99.9 μmol/L）,and 0.972 for Stage 3 （sensitivity 94.1％,specificity 88.2％,cutoff value 122.90 μmol/L）.Conclusion：The sensitivity and specificity of serum Cr might be a high-value indicator for the diagnosis and grading of post-OLT AKI.展开更多
The symbiotic relationship between the host and the rumen microbiome plays a crucial role in ruminant physiology.One of the most important processes enabling this relationship is urea nitrogen salvaging(UNS).This proc...The symbiotic relationship between the host and the rumen microbiome plays a crucial role in ruminant physiology.One of the most important processes enabling this relationship is urea nitrogen salvaging(UNS).This process is important for both maintaining ruminant nitrogen balance and supporting production of their major energy supply,bacterially-derived short chain fatty acids(SCFA).The key step in UNS is the trans-epithelial movement of urea across the ruminal wall and this is a highly regulated process.At the molecular level,the key transport route is via the facilitative urea transporter-B2,localized to ruminal papillae epithelial layers.Additional urea transport through aquaporins(AQP),such as AQP3,is now also viewed as important.Long-term regulation of these ruminal urea transport proteins appears to mainly involve dietary fermentable carbohydrates;whereas,transepithelial urea transport is finely regulated by local conditions,such as CO_(2) levels,pH and SCFA concentration.Although the key principles of ruminal urea transport physiology are now understood,there remains much that is unknown regarding the regulatory pathways.One reason for this is the limited number of techniques currently used in many studies in the field.Therefore,future research in this area that combines a greater range of techniques could facilitate improvements to livestock efficiency,and potentially,reductions in the levels of waste nitrogen entering the environment.展开更多
Field experiments were conducted to study the effects of the controlled release urea (CRU) application on growth yield and nitrogen recovery efficiency of cotton in the main cotton zone of the Yangtze River basin in 2...Field experiments were conducted to study the effects of the controlled release urea (CRU) application on growth yield and nitrogen recovery efficiency of cotton in the main cotton zone of the Yangtze River basin in 2010. Different nitrogen levels were set in order to determine the suitable dosage of CRU on cotton. The special purpose was to provide evidence for the CRU application in cotton fields. The results show that the application of CRU promotes the growth of cotton significantly and enhances the nitrogen supply in the whole period. Compared to the treatment with total N as base fertilizer (UB), the bod, flower, little bolls and total bolls are increased significantly. There are no significant differences in the yield between the CRU treatment and the treatment of controlled release urea and urea combined application (60%CRU + 40%U), but an increase by 12.38%-22.67% compared to the UB treatment, and an increase by 4.49%-7.23% compared to the treatments of total N split application (UD). The nitrogen uptake of CRU treatment was significantly increased by 13.01%-48.32% and 30.27%-13.01% than UB treatment and UD treatment, respectively. The nutrient recovery efficiency of CRU treatment is increased by 16.42-20.59, 5.92-11.29 and 4.22-12.59 percentage points compared to the UB treatment, UD treatment and 60%CRU + 40%U treatment, respectively. In this study, there was a good linearity relationship between the cotton yield and amount of CRU in Wuxue site. The yield of cotton response to amount of CRU could be described by the model of linear plus plateau in Jingzhou site.展开更多
The fertiliser industry faces a continuing challenge to improve the efficiency of their products,particularly of nitrogenous fertilisers,and to minimise adverse impacts.Therefore,a new slow release fertilizer,ureaimpr...The fertiliser industry faces a continuing challenge to improve the efficiency of their products,particularly of nitrogenous fertilisers,and to minimise adverse impacts.Therefore,a new slow release fertilizer,ureaimpregnated woodchips from tropical plant biomass(oil palm frond and rubberwood),was developed.The morphology of the impregnated woodchips was investigated by scanning electron microscopy and the success of impregnation of urea and nitrogen deposition into the woodchips was confirmed by energy dispersive X-ray spectrometry.When nitrogen release patterns from impregnated woodchips fertiliser were simulated using a soil solution and distilled water as leaching solutions in a static condition for 768 h,release was slow and steady,although the release rate was lower in distilled water than in the soil solution.展开更多
Laboratory-scale tests for magnesium ammonium phosphate（MAP）precipitation following urea hydrolysis of human urine were conducted using orthogonal experiment design.The effects of initial pH,temperature and the volu...Laboratory-scale tests for magnesium ammonium phosphate（MAP）precipitation following urea hydrolysis of human urine were conducted using orthogonal experiment design.The effects of initial pH,temperature and the volumetric ratios of stale urine to fresh urine,on urea hydrolysis in urine were studied to determine the final hydrolysis time to recover most nitrogen from separated human urine by MAP.With a volumetric ratio of stale to fresh urine>10% and at temperature≥20℃,urea hydrolysis could be completed in two days.Alkaline pH inhibited urea hydrolysis progress.The final pH values were all around 9.0 following urine hydrolysis,while the suspension pH might act as an indicator to detect the start and extent of urea hydrolysis.Over 95% of ammonium nitrogen and over 85% of phosphorus from hydrolyzed urine as MAP precipitate were obtained using MgCl;·6H;O and Na;HPO;·12H;O as precipitation agents at pH 8.5,molar ratio of Mg;:NH;-N:PO;-P at（1.2-1.3）:1:1,mixing speed of 120 r/min,and precipitation time and reaction time of 3 h and 15 min,respectively.The precipitate has a structure resembling pure MAP crystal.展开更多
Poorly-drained, river bottom soils can be high corn (Zea mays L.) yielding environments, but saturated soil conditions often reduce corn yields. Wabash soils located in river bottoms in Northeast Missouri have not bee...Poorly-drained, river bottom soils can be high corn (Zea mays L.) yielding environments, but saturated soil conditions often reduce corn yields. Wabash soils located in river bottoms in Northeast Missouri have not been traditionally tile drained due to high clay content which requires narrow tile drain spacings. Increased land prices in the region have increased interest in tile draining poorly-drained bottom land soils to increase corn yields which could have a deleterious effect on water quality. The objectives of the three-year study were to determine whether use of managed subsurface drainage (MD) in combination with a controlled release N fertilizer could reduce the annual amount of NO3--N loss through tile drainage water compared to free subsurface drainage (FD) with a non-coated urea application. Annual NO3--N loss through tile drainage water with FD ranged from 28.3 to 90.1 kg·N·ha-1. Nitrogen fertilizer source did not affect NO3--N loss through tile drainage water, which was likely due to limited corn uptake over the three-year study due to adverse weather conditions. Averaged over three years, MD reduced tile water drained 52% and NO3--N loss 29% compared to FD. Reduction in NO3--N loss through tile drainage water with MD compared to FD was due to reduced tile flow during the non-cropping period. Annual flow-weighted mean concentration of NO3--N in the tile water was 5.8 mg·N·L-1 with FD and 8.1 mg·N·L-1 with MD. Tile draining river bottom soils at this location for continuous corn production may not pose a health risk over the evaluated duration.展开更多
基金This work was supposed by the Natural Science Foundation of Tianjin City(No．03380211)
文摘The adsorption of urea nitrogen onto chitosan coated dialdehyde cellulose (CDAC) under catalysis of immobilized urease in gelatin membrane (IE) was studied in batch system. The pseudo first-order and second-order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. The experimental data fitted well to the second-order kinetic model.
文摘Summary： The effects of oligosaccharide and creatine （Cr） supplementation on glucose, lactic acid and urea nitrogen levels in blood and activity of serum creatine kinase （CK） were explored. Twenty CUBA male athletes were divided into 4 groups： group A （supplementation of Cr alone）, group B （supplementation of oligosaccharide）, group C （supplementation of oligosaccharide and Cr） and group D （placebo control group）. By using orthogonal L4 table （2a ）, the experiment was performed. There were factors including oligosaccharide （carbohydrate, CHO）, Cr and their correlation. Each factor had two levels： supplementation and no-supplementation. The results showed that the supplementation of CliO or Cr alone, combined supplementation of CHO and Cr could significantly reduce the glucose, urea nitrogen levels in blood and serum CK activity after competition in the athletes. Moreover, the effects of combined supplementation of CHO and Cr were more satisfactory. It was concluded that supplementation of CliO and Cr could promote the recovery of physical performance and athletic abilities after athletics in basketball athletes.
基金SUPPORTED BY NATURAL SCIENCE FOUNDATION OF TIANJIN ( NO. 033802011).
文摘The urea nitrogen adsorbent of complex type, which consists of chitosan coated dialdehyde cellulose （CDAC） and immobilized urease in gelatin membrane （IE）, was prepared. The cellulose, the dialdehyde cellulose （DAC） and the CDAC were characterized by scanning electronic microscope. The results indicate that the cellulose C2-C3 bond was broken under the oxidation of periodate and it was oxidated to DAC. The DAC was coated with chitosan and the CDAC was obtained. The adsorption of urea nitrogen onto the adsorbent in Na2HPO4-NaH2PO4 buffer solution was studied in batch system. The effects of the experiment parameters, including degree of oxidation of CDAC, initial urea nitrogen concentration, pH and temperature, on the adsorption capacity of urea nitrogen onto the adsorbent at CDAC/IE weight ratio 10：1 were investigated. The results indicate that these parameters affected significantly the adsorption capacity. The adsorption capacity of urea nitrogen onto the adsorbent was 36.7 mg/g at the degree of oxidation of CDAC 88%, initial urea nitrogen concentration 600 mg/L, pH 7.4 and temperature 37℃.
文摘AIM: To examine characteristics of patients with blood urea nitrogen(BUN) levels higher and lower than the normal limit.METHODS: Patient records between April 2011 and March 2014 were analyzed retrospectively. During this time, 3296 patients underwent upper endoscopy. In total, 50 male(69.2 ± 13.2 years) and 26 female(72.3 ± 10.2 years) patients were assessed. Patients were divided into two groups based on BUN levels: higher than the normal limit(21.0 mg/d L)(H) and lower thanthe normal limit(L). One-way analysis of variance was performed to reveal differences in the variables between the H and L groups. Fisher's exact test was used to compare the percentage of patients with gastric ulcer or gastric cancer in the H and L groups.RESULTS: White blood cell count was higher in the H group than in the L group(P = 0.0047). Hemoglobin level was lower in the H group than in the L group(P = 0.0307). Glycated hemoglobin was higher in the H group than in the L group(P = 0.0264). The percentage of patients with gastric ulcer was higher in the H group(P = 0.0002). The H group contained no patients with gastric cancer.CONCLUSION: Patients with BUN ≥ 21 mg/d L might have more severe upper gastrointestinal bleeding.
文摘Near-infrared (NIR) spectroscopy combined with chemometrics methods was applied to the rapid and reagent-free analysis of serum urea nitrogen (SUN). The mul-partitions modeling was performed to achieve parameter stability. A large-scale parameter cyclic and global optimization platform for Norris derivative filter (NDF) of three parameters (the derivative order: d, the number of smoothing points: s and the number of differential gaps: g) was developed with PLS regression. Meantime, the parameters’ adaptive analysis of NDF algorithm was also given, and achieved a significantly better modeling effect than one without spectral pre-processing. After eliminating the interference wavebands of saturated absorption, the modeling performance was further improved. In validation, the root mean square error (SEP), correlation coefficient (RP) for prediction and the ratio of performance to deviation (RPD) were 1.66 mmol?L-1, 0.966 and 4.7, respectively. The results showed that the high-precision analysis of SUN was feasibility based on NIR spectroscopy and Norris-PLS. The global optimization method of NDF is also expected to be applied to other analysis objects.
文摘Background：As a major complication after orthotopic liver transplantation （OLT）,the occurrence of acute kidney injury （AKI） is frequently defined by serum creatinine （Cr）;however,the accuracy of commonly used blood urea nitrogen （BUN）,uric acid （UA）,and β2-microglobulin （β2-MG） remains to be explored.This retrospective study compared the accuracy of these parameters for post-OLT AKI evaluation.Methods：Patients who underwent OLT in three centers between July 2003 and December 2013 were enrolled.The postoperative AKI group was diagnosed by the Kidney Disease Improving Global Outcomes （KDIGO） criteria and classified by stage.Measurement data were analyzed using the t-test or Wilcoxon rank-sum test;enumerated data were analyzed using the Chi-square test or Fisher＇s exact test.Diagnostic reliability and predictive accuracy were evaluated using receiver operating characteristic （ROC） curve analysis.Results：This study excluded 976 cases and analyzed 697 patients （578 men and 1 1 9 women）;the post-OLT AKI incidence was 0.409.Compared with the no-AKI group,the AKI group showed very significant differences in Model for End-stage Liver Disease score （14.74 ± 9.91 vs.11.07 ± 9.54,Z =5.404;P ＜ 0.001）,hepatic encephalopathy （45 [15.8％] vs.30 [7.3％],x2 =12.699;P ＜ 0.001）,hemofiltration （28 [9.8％] vs.0 [0.0％],x2 =42.171;P ＜ 0.001）,and 28-day mortality （23 [8.1％] vs.9 [2.2％],x2 13.323;P ＜0.001）.Moreover,mean values of Cr,BUN,UA,and β2-MG in the AKI group differed significantly at postoperative days 1,3,and 7 （all P ＜0.001）.ROC curve area was 0.847 of Cr for the detection of AKI Stage 1 （sensitivity 80.1％,specificity 75.7％,cutoffvalue 88.23 μmol/L）,0.916 for Stage 2 （sensitivity 87.6％,specificity 82.6％,cutoff value 99.9 μmol/L）,and 0.972 for Stage 3 （sensitivity 94.1％,specificity 88.2％,cutoff value 122.90 μmol/L）.Conclusion：The sensitivity and specificity of serum Cr might be a high-value indicator for the diagnosis and grading of post-OLT AKI.
基金China Postdoctoral Science Foundation(2021M701532)National Natural Science Foundation of China(32072757).
文摘The symbiotic relationship between the host and the rumen microbiome plays a crucial role in ruminant physiology.One of the most important processes enabling this relationship is urea nitrogen salvaging(UNS).This process is important for both maintaining ruminant nitrogen balance and supporting production of their major energy supply,bacterially-derived short chain fatty acids(SCFA).The key step in UNS is the trans-epithelial movement of urea across the ruminal wall and this is a highly regulated process.At the molecular level,the key transport route is via the facilitative urea transporter-B2,localized to ruminal papillae epithelial layers.Additional urea transport through aquaporins(AQP),such as AQP3,is now also viewed as important.Long-term regulation of these ruminal urea transport proteins appears to mainly involve dietary fermentable carbohydrates;whereas,transepithelial urea transport is finely regulated by local conditions,such as CO_(2) levels,pH and SCFA concentration.Although the key principles of ruminal urea transport physiology are now understood,there remains much that is unknown regarding the regulatory pathways.One reason for this is the limited number of techniques currently used in many studies in the field.Therefore,future research in this area that combines a greater range of techniques could facilitate improvements to livestock efficiency,and potentially,reductions in the levels of waste nitrogen entering the environment.
文摘Field experiments were conducted to study the effects of the controlled release urea (CRU) application on growth yield and nitrogen recovery efficiency of cotton in the main cotton zone of the Yangtze River basin in 2010. Different nitrogen levels were set in order to determine the suitable dosage of CRU on cotton. The special purpose was to provide evidence for the CRU application in cotton fields. The results show that the application of CRU promotes the growth of cotton significantly and enhances the nitrogen supply in the whole period. Compared to the treatment with total N as base fertilizer (UB), the bod, flower, little bolls and total bolls are increased significantly. There are no significant differences in the yield between the CRU treatment and the treatment of controlled release urea and urea combined application (60%CRU + 40%U), but an increase by 12.38%-22.67% compared to the UB treatment, and an increase by 4.49%-7.23% compared to the treatments of total N split application (UD). The nitrogen uptake of CRU treatment was significantly increased by 13.01%-48.32% and 30.27%-13.01% than UB treatment and UD treatment, respectively. The nutrient recovery efficiency of CRU treatment is increased by 16.42-20.59, 5.92-11.29 and 4.22-12.59 percentage points compared to the UB treatment, UD treatment and 60%CRU + 40%U treatment, respectively. In this study, there was a good linearity relationship between the cotton yield and amount of CRU in Wuxue site. The yield of cotton response to amount of CRU could be described by the model of linear plus plateau in Jingzhou site.
基金supported by Research University Grant Scheme(RUGS)University Putra Malaysia(No.03-02-12-2293RU)
文摘The fertiliser industry faces a continuing challenge to improve the efficiency of their products,particularly of nitrogenous fertilisers,and to minimise adverse impacts.Therefore,a new slow release fertilizer,ureaimpregnated woodchips from tropical plant biomass(oil palm frond and rubberwood),was developed.The morphology of the impregnated woodchips was investigated by scanning electron microscopy and the success of impregnation of urea and nitrogen deposition into the woodchips was confirmed by energy dispersive X-ray spectrometry.When nitrogen release patterns from impregnated woodchips fertiliser were simulated using a soil solution and distilled water as leaching solutions in a static condition for 768 h,release was slow and steady,although the release rate was lower in distilled water than in the soil solution.
文摘Laboratory-scale tests for magnesium ammonium phosphate（MAP）precipitation following urea hydrolysis of human urine were conducted using orthogonal experiment design.The effects of initial pH,temperature and the volumetric ratios of stale urine to fresh urine,on urea hydrolysis in urine were studied to determine the final hydrolysis time to recover most nitrogen from separated human urine by MAP.With a volumetric ratio of stale to fresh urine>10% and at temperature≥20℃,urea hydrolysis could be completed in two days.Alkaline pH inhibited urea hydrolysis progress.The final pH values were all around 9.0 following urine hydrolysis,while the suspension pH might act as an indicator to detect the start and extent of urea hydrolysis.Over 95% of ammonium nitrogen and over 85% of phosphorus from hydrolyzed urine as MAP precipitate were obtained using MgCl;·6H;O and Na;HPO;·12H;O as precipitation agents at pH 8.5,molar ratio of Mg;:NH;-N:PO;-P at（1.2-1.3）:1:1,mixing speed of 120 r/min,and precipitation time and reaction time of 3 h and 15 min,respectively.The precipitate has a structure resembling pure MAP crystal.
文摘Poorly-drained, river bottom soils can be high corn (Zea mays L.) yielding environments, but saturated soil conditions often reduce corn yields. Wabash soils located in river bottoms in Northeast Missouri have not been traditionally tile drained due to high clay content which requires narrow tile drain spacings. Increased land prices in the region have increased interest in tile draining poorly-drained bottom land soils to increase corn yields which could have a deleterious effect on water quality. The objectives of the three-year study were to determine whether use of managed subsurface drainage (MD) in combination with a controlled release N fertilizer could reduce the annual amount of NO3--N loss through tile drainage water compared to free subsurface drainage (FD) with a non-coated urea application. Annual NO3--N loss through tile drainage water with FD ranged from 28.3 to 90.1 kg·N·ha-1. Nitrogen fertilizer source did not affect NO3--N loss through tile drainage water, which was likely due to limited corn uptake over the three-year study due to adverse weather conditions. Averaged over three years, MD reduced tile water drained 52% and NO3--N loss 29% compared to FD. Reduction in NO3--N loss through tile drainage water with MD compared to FD was due to reduced tile flow during the non-cropping period. Annual flow-weighted mean concentration of NO3--N in the tile water was 5.8 mg·N·L-1 with FD and 8.1 mg·N·L-1 with MD. Tile draining river bottom soils at this location for continuous corn production may not pose a health risk over the evaluated duration.
