This study presents a novel approach,the Supercapacitor Microbial Electrolysis Cell(SCMEC),which utilizes a supercapacitor as an external power source to enhance the efficiency of autotrophic nitrogen removal in low C...This study presents a novel approach,the Supercapacitor Microbial Electrolysis Cell(SCMEC),which utilizes a supercapacitor as an external power source to enhance the efficiency of autotrophic nitrogen removal in low C/N ratio wastewater.The results demonstrated that the SC-MEC system,operating under anaerobic conditions and devoid of any organic carbon source,exhibited exceptional performance in ammonia oxidation and total nitrogen(TN)removal when solely relying on ammonia nitrogen as the electron donor.Operating at a voltage of 1.8 V with a capacitance capacity of 30 F,ammonium oxidation rated up to 56.51 mg/L/day and TN removal rated up to 54.64 mg/L/day,in which 97%of ammonium nitrogen was converted to gaseous nitrogen.Furthermore,the charging and discharging process of supercapacitors autonomously regulated the bipolar potentials.Cyclic voltammetry(CV)analysis showed the significantly enhanced electrochemical activity of the SCMEC system during the reaction process.Based on in-situ CV test results,itwas inferred that this enhancementwas associated with extracellular electron transfer mediators.Themicrobial community analysis revealed a process of synchronous nitrification and denitrification(SND)coupled with anammox,involvingmultiple genera,such as Candidatus Kuenenia,Nitrosomonas,Truepera,and Bosea.In conclusion,this study highlights the tremendous potential of SC-MEC in achieving efficient autotrophic nitrogen removal,offering more feasible and economical solutions for addressing low C/N water pollution issues.展开更多
[Objective]The aim was to study the effects of regulation of C/N ratio wheat straw application on tobacco nitrogen,phosphorus and potassium uptake. [Method]Effects of regulation C/N ratio wheat straw application on th...[Objective]The aim was to study the effects of regulation of C/N ratio wheat straw application on tobacco nitrogen,phosphorus and potassium uptake. [Method]Effects of regulation C/N ratio wheat straw application on the flue-cured tobacco yield,output value,nitrogen,phosphorus and potassium content and cumulative uptake of the upper,middle and bottom leaf were studied by using the field plot experiments at Banqiao town,Qujing city,Yunnan Province during the 2008-2009 summer growing seasons. [Result]The results showed that the application of wheat straw alone or after C/N regulation,could significantly increase tobacco production,potassium content,the potassium and nitrogen accumulation amount of leaf,and was more conducive to the potassium uptake of tobacco leaf with wheat straw application after C/N regulation. Compared with non-straw application,the yield of tobacco increased by 6.59%,3.58%,5.98%,8.80% with application of wheat straw alone,wheat straw and vetch,wheat straw and oilseed cake,wheat straw and urea nitrogen,the potassium content in tobacco leaf increased by 3.85%,7.76%,8.82%,11.21%,respectively,the total potassium cumulative amount of leaf increased by 10.71%,11.62%,15.32% ,21.01% and the total nitrogen cumulative amount increased by 9.76%,1.22%,8.14%,14.00%. However,the differences of tobacco leaf nitrogen content among the different treatments were not significant,the phosphorus uptake of tobacco leaf decreased. [Conclusion]application of high C/N ratio wheat straw in flue-cured tobacco production,which should be concerned not only to adjust C/N ratio by adding nitrogen,but also considering additional phosphorus application.展开更多
Expression of insecticidal protein for transgenic Bacillus thuringiensis （Bt） cotton is unstable and related to nitrogen metabolism. The objective of this study was to investigate the relationship between leaf carbo...Expression of insecticidal protein for transgenic Bacillus thuringiensis （Bt） cotton is unstable and related to nitrogen metabolism. The objective of this study was to investigate the relationship between leaf carbon nitrogen ratio （C/N） and insecticidal efficacy of two Bt cotton cultivars. C/N ratio and Bt protein content were both measured at peak square period and peak boll period respectively under 5-7 d high temperature and different nitrogen fertilizer rates on the Yangzhou University Farm and the Ludong Cotton Farm, China. All plants were grown in field. The results showed that the C/N ratio enhanced slightly and the Bt protein content remained stable at peak square period, but significant increases for the C/N ratio and decreases markedly for the leaf Bt protein concentration were detected at the peak boll period. The similar patterns at the two growth periods were found for the leaf C/N ratio and Bt protein content by different N fertilizer treatments. When nitrogen rate was from 0 to 600 kg ha-l, the C/N ratio was reduced by 0.017 and 0.006 for Sikang 1 and Sikang 3 at peak square period, compared to the 1.350 to 1.143 reduction for Sikang 1 and Sikang 3 at peak boll period, respectively. Correspondingly, the leaf Bt protein contents were bolstered by 2.6-11.8 and 26.9-36.9% at the two different growth periods, respectively. The results suggested that enhanced C/N ratio by high temperature and nitrogen application may result in the reduction of inseetiocidal efficacy in Bt cotton, especially in peak boll period.展开更多
Returning rice straw and leguminous green manure alone or in combination to soil is effective in improving soil fertility in South China.Despite the popularity of this practice,our understanding o f the underlying pro...Returning rice straw and leguminous green manure alone or in combination to soil is effective in improving soil fertility in South China.Despite the popularity of this practice,our understanding o f the underlying processes for straw and manure combined application is relatively poor.In this study,rice straw(carbon(C)/nitrogen(N)ratio of 63),green manure(hairy vetch,C/N ratio of 14),and their mixtures(C/N ratio of 25 and 35)were added into a paddy soil,and their effects on soil N availability and C or N loss under waterlogged conditions were evaluated in a 100-d incubation experiment.All plant residue treatments significantly enhanced C〇2 and CH4 emissions,but decreased N2O emission.Dissolved organic C(DOC)and N(DON)and microbial biomass C in soil and water-soluble organic C and N and mineral N in the upper aqueous layer above soil were also enhanced by all the plant residue treatments except the rice straw treatment,and soil microbial biomass N and mineral N were lower in the rice straw treatment than in the other treatments.Changes in plant residue C/N ratio,DOC/DON ratio,and cellulose content significantly affected greenhouse gas emissions and active C and N concentrations in soil.Additionally,the treatment with green manure alone yielded the largest C and N losses,and incorporation of the plant residue mixture with a C/N ratio of 35 caused the largest net global warming potential(nGWP)among the amended treatments.In conclusion,the co-incorporation of rice straw and green manure can alleviate the limitation resulting from only applying rice straw(N immobilization)or the sole application of leguminous green manure(high C and N losses),and the residue mixture with a C/N ratio of 25 is a better option because of lower nGWP.展开更多
Biofloc technology has been applied successfully in the intensive aquaculture of several fish and shrimp species. The growth of heterotrophic microorganisms can be stimulated through adding extra carbon, which reduces...Biofloc technology has been applied successfully in the intensive aquaculture of several fish and shrimp species. The growth of heterotrophic microorganisms can be stimulated through adding extra carbon, which reduces the nitrogen level in the water and provides microbial protein to the animals. However, most of the studies and practical applications have been conducted in freshwater and marine environment. This paper focused on brine shrimp Artemia that lives in high salinity environment together with other halophilic or halotolerant microorganisms. The effect of carbon supplementation on Artemia growth, water quality, and microbial diversity of biofl ocs was studied in the closed culture condition without any water exchange. The salinity of the culture medium was 100. A 24-d culture trial was conducted through supplementing sucrose at carbon/nitrogen (C/N) ratio of 5, 15, and 30 (Su5, Su15, and Su30), respectively. The culture without adding sucrose was used as a control. Artemia was fed formulated feed at a feeding ration of 60% recommended feeding level. The results showed that sucrose supplementation at higher C/N ratio (15 and 30) signifi cantly improved the Artemia survival, growth and water quality ( P <0.05). Addition of sucrose at C/N ratio of 15 and 30 significantly increased biofloc volume (BFV)( P <0.05). The Illumina MiSeq sequencing analysis showed that supplementing carbon at C/N ratio of 15 had a better total bacterial diversity and richness, and shaped the microbial composition at genera level. This study should provide information for studying the mechanism of biofloc technology and its application in high salinity culture conditions.展开更多
Soil organic carbon and nitrogen are used as indexes of soil quality assessment and sustainable land use management. At the same time, soil C/N ratio is a sensitive indicator of soil quality and for assessing the carb...Soil organic carbon and nitrogen are used as indexes of soil quality assessment and sustainable land use management. At the same time, soil C/N ratio is a sensitive indicator of soil quality and for assessing the carbon and nitrogen nutrition balance of soils. We studied the characteristics of soil organic carbon and total nitrogen by investigating a large number of apple orchards in major apple production areas in China. High apple orchard soil organic carbon content was observed in the provinces of Heilongjiang, Xinjiang, and Yunnan, whereas low content was found in the provinces of Shandong, Henan, Hebei, and Shaanxi, with the values ranging between 6.44 and 7.76 g·kg-1. Similar to soil organic carbon, soil total nitrogen content also exhibited obvious differences in the 12 major apple producing provinces. Shandong apple orchard soil had the highest total nitrogen content (1.26 g·kg-1), followed by Beijing (1.23 g·kg-1). No significant difference was noted between these two regions, but their total nitrogen content was significantly higher than the other nine provinces, excluding Yunnan. The soil total nitrogen content for Xinjiang, Heilongjiang, Hebei, Henan, and Gansu was between 0.87 and 1.03 g·kg-1, which was significantly lower than that in Shandong and Beijing, but significantly higher than that in Liaoning, Shanxi, and Shaanxi. Six provinces exhibited apple orchard soil C/N ratio higher than 10, including Heilongjiang (15.42), Xinjiang (13.38), Ningxia (14.45), Liaoning (12.24), Yunnan (11.03), and Gansu (10.63). The soil C/N ratio was below 10 in the remaining six provinces, in which the highest was found in Shaanxi (9.47), followed by Beijing (8.98), Henan (7.99), and Shanxi (7.62), and the lowest was found in Hebei (6.80) and Shandong (6.05). Therefore, the improvement of soil organic carbon should be given more attention to increase the steady growth of soil C/N ratio.展开更多
Microbial activity and nutrient release are known to be influenced by organic matter properties,but it is difficult to separate the effect of C/N ratio from that of C/P ratio because in most plant residues both ratios...Microbial activity and nutrient release are known to be influenced by organic matter properties,but it is difficult to separate the effect of C/N ratio from that of C/P ratio because in most plant residues both ratios are either high or low.An incubation experiment was conducted to investigate the effects of reducing the C/N and C/P ratios of slowly decomposable plant residues(young eucalyptus leaves,mature wheat straw,and sawdust) to those of rapidly decomposable residues(young kikuyu shoots) on soil respiration,microbial biomass,and N and P availability.The C/N and C/P ratios of the former were adjusted to 15 and 89,respectively,by adding N as(NH_4)_2SO_4,P as KH_2PO_4 or both and residues were added at 10 g C kg-1 to a silt loam.Soil respiration was measured over21 d;microbial biomass C(MBC) and available N and P were measured on days 0,7,and 21.Compared to the unamended soil,addition of kikuyu increased cumulative respiration 20-fold,MBC concentration 4 to 8-fold,and available P concentration up to4-fold,whereas the increase in available N concentration was small and transient.Cumulative respiration and MBC concentration were low in the sawdust-amended soil and were not influenced by reducing the C/N and C/P ratios.Cumulative respiration with original wheat and eucalyptus was 30%-40%of that with kikuyu.Reducing the C/N ratio alone or both C/N and C/P ratios increased cumulative respiration and MBC concentration 2-fold compared to the original wheat and eucalyptus,whereas reducing the C/P ratio had little effect.Throughout the experiment,the available N concentration after addition of residues with reduced C/N ratio increased in the following order of eucalyptus < wheat < sawdust.By independently lowering the C/N and C/P ratios,microbial activity was more limited by C and N than P.However,lowering the C/N ratio of very slowly decomposable sawdust had no effect on soil respiration and MBC concentration,suggesting that other properties such as concentration of poorly decomposable C compounds limited decomposition.展开更多
Soil salinization is a critical environmental issue restricting agricultural production.Deep return of straw to the soil as an interlayer (at 40 cm depth) has been a popular practice to alleviate salt stress.However,t...Soil salinization is a critical environmental issue restricting agricultural production.Deep return of straw to the soil as an interlayer (at 40 cm depth) has been a popular practice to alleviate salt stress.However,the legacy effects of straw added as an interlayer at different rates on soil organic carbon (SOC) and total nitrogen (TN) in saline soils still remain inconclusive.Therefore,a four-year (2015–2018) field experiment was conducted with four levels (i.e.,0,6,12and 18 Mg ha~(–1)) of straw returned as an interlayer.Compared with no straw interlayer (CK),straw addition increased SOC concentration by 14–32 and 11–57%in the 20–40 and 40–60 cm soil layers,respectively.The increases in soil TN concentration (8–22 and 6–34%in the 20–40 and 40–60 cm soil layers,respectively) were lower than that for SOC concentration,which led to increased soil C:N ratio in the 20–60 cm soil depth.Increases in SOC and TN concentrations in the 20–60 cm soil layer with straw addition led to a decrease in stratification ratios (0–20 cm:20–60 cm),which promoted uniform distributions of SOC and TN in the soil profile.Increases in SOC and TN concentrations were associated with soil salinity and moisture regulation and improved sunflower yield.Generally,compared with other treatments,the application of 12 Mg ha~(–1) straw had higher SOC,TN and C:N ratio,and lower soil stratification ratio in the2015–2017 period.The results highlighted that legacy effects of straw application as an interlayer were maintained for at least four years,and demonstrated that deep soil straw application had a great potential for improving subsoil fertility in salt-affected soils.展开更多
The effects of C/N ratio of a nitrate-containing wastewater on nitrate removal performed by autohydrogenotrophic bacteria as well as on the morphological parameters of floc such as floc morphology, floc number distrib...The effects of C/N ratio of a nitrate-containing wastewater on nitrate removal performed by autohydrogenotrophic bacteria as well as on the morphological parameters of floc such as floc morphology, floc number distribution, mean particle size（MPS）, aspect ratio and transparency were examined in this study. The results showed that the nitrate reduction rate increased with increasing C/N ratio from 0.5 to 10 and that the nitrogen removal of up to 95% was found at the C/N ratios of higher than 5（between 0.5–10）. Besides, high C/N ratio values reflected a corresponding high nitrite accumulation after 12-hr operation, and a fast decreasing rate of nitrite in the rest of operational time. The final p H values increased with the C/N ratio increasing from 0.5 to 2.5, but decreased with the C/N ratio increasing from2.5 to 10. There were no significant changes in floc morphology with the MPSs ranging from35 to 40 μm. Small and medium-sized flocs were dominant in the sludge suspension, and the number of flocs increased with the increasing C/N ratios. Furthermore, the highest apparent frequency of 10% was observed at aspect ratios of 0.5 and 0.6, while the transparency of flocs changed from 0.1 to 0.7.展开更多
External organic carbon sources are needed to provide electron donors for the denitrification of wastewater with a low COD/NO_(3)^(-)-N(C/N)ratio,increasing the treatment cost.The economic strategy is to enhance the b...External organic carbon sources are needed to provide electron donors for the denitrification of wastewater with a low COD/NO_(3)^(-)-N(C/N)ratio,increasing the treatment cost.The economic strategy is to enhance the bioactivity and/or biodiversity of denitrifiers to efficiently utilize organic substances in wastewater.In this study,novel zero-valent iron(ZVI)composite carriers were prepared and implemented in a suspended carrier biofilm reactor to enhance the bioactivity and/or biodiversity of denitrifiers.At the influent C/N ratio of 4(COD was 179.5±5.0 mg/L and TN was 44.2±0.8 mg/L),COD and TN removal efficiencies were 85.1%and 66.4%,respectively,in the reactors filled with 3 wt%ZVI composite carriers.In contrast,COD and TN removal efficiencies were 70.4%and 55.3%,respectively,in the reactor filled with conventional high-density polyethylene(HDPE)biofilm carriers.The biofilm formation on the 3 wt%ZVI composite carriers was optimized due to its higher roughness(surface square roughness increased from 76.0 nm to 93.8 nm)and favorable hydrophilicity(water contact angle dropped to 72.5°±1.4°from 94.3°±3.2°)compared with the HDPE biofilm carriers.In addition,heterotrophic denitrifiers,Thauera and Dechloromonas,were enriched,whereas autotrophic denitrifiers,Raoultella and Thiobacillus,exhibited high relative abundance in the biofilm of ZVI composite carriers.The coexistence of heterotrophic denitrifiers and autotrophic denitrifiers on the surface of ZVI composite carriers provided mixotrophic metabolism of denitrification(including heterotrophic and iron-based autotrophic),thereby ensuring effective denitrification for wastewater with a low C/N ratio without external organic carbon source addition.展开更多
In order to explore the effect of carbon and nitrogen(C/N)ratio on the performance of anoxic/aerobic-moving bed bio-film reactor(A/O-MBBR)process for treating mariculture wastewater,a laboratory-scale A/O-MBBR was con...In order to explore the effect of carbon and nitrogen(C/N)ratio on the performance of anoxic/aerobic-moving bed bio-film reactor(A/O-MBBR)process for treating mariculture wastewater,a laboratory-scale A/O-MBBR was conducted.The results showed that the reduction of C/N ratio was conducive to improving the removal efficiency of chemical oxygen demand(COD)and ammonia nitrogen(NH_(4)^(+)-N),while inhibiting that of nitrite nitrogen(NO_(2)^(−)-N)and nitrate nitrogen(NO_(3)^(−)-N).The extracellular polymeric substances(EPS)in anoxic zone were significantly higher in concentration than that in aerobic zone although they both declined with decrease of C/N ratio.The result provides solid support for better controlling the pollution of mariculture wastewater.展开更多
In forage grasses, the nitrogen concentration is directly related to the nutritional value. The studies examined the hypothesis that global elevation of CO2 concentration probably affects the biomass, nitrogen （N） c...In forage grasses, the nitrogen concentration is directly related to the nutritional value. The studies examined the hypothesis that global elevation of CO2 concentration probably affects the biomass, nitrogen （N） concentration, and allocation and distribution patterns in the organs of forage grasses. While sainfoin （Onobrychis viciaefolia Scop.） seedlings grew on a low nutrient soil in closed chambers for 90 days, they were exposed to two CO2 concentrations （ambient or ambient＋350 μmol mol^-1 CO2） without adding nutrients to them. After 90 days exposure to CO2, the biomasses of leaves, stems, and roots, and N concentrations and contents of different parts were measured. Compared with the ambient CO2 concentration, the elevated CO2 concentration increased the total dry matter by 25.07%, mainly due to the root and leaf having positive response to the elevated CO2 concentration. However, the elevated CO2 concentration did not change the proportions of the dry matters in different parts and the total plants compared with the ambient CO2 concentration. The elevated CO2 concentration lowered the N concentrations of the plant parts. Because the dry matter was higher, the elevated CO2 concentration had no effect on the N content in the plants compared to the ambient CO2 concentration. The elevated CO2 concentration promoted N allocations of the different parts significantly and increased N allocation of the underground part. The results have confirmed the previous suggestions that the elevated CO2 concentration stimulates plant biomass production and decreases the N concentrations of the plant parts.展开更多
On the basis of multi-proxy analysis on TOC, TN, C/N, organic δ^13C and grain size, sediment record from Qinghai Lake provides evidences of stepwise-pattemed climatic change since 16 ka BE Results show that Qinghai L...On the basis of multi-proxy analysis on TOC, TN, C/N, organic δ^13C and grain size, sediment record from Qinghai Lake provides evidences of stepwise-pattemed climatic change since 16 ka BE Results show that Qinghai Lake underwent six environmental stages. From 16.2 to 14.3 ka BP and from 4.0 to 2.1 ka BP, the organic δ^13C value was controlled by the concentration of atmospheric CO2. Relative higher organic δ^13C values occurred between 14.3 to 10.4 ka BP indicative of water hardness decrease resulted from melting ice water, corresponding to two intervals of C/N peak values to the Boling and AIlerod warm periods in Europe respectively. From 10.4 ka BP, Qinghai Lake entered the Holocene and the climate was warm and a little dry. The Megathermal appeared at about 6.7 ka BP when the vegetation around the lake transformed into a forest. Between 6.3 ka BP and 4.0 ka BP, the temperature decreased and δ^13C value was controlled by the expansion of C3 plants and the retreat of C4 plants in river catchment. Since 4.0 ka BP, the climate gradually became cold and dry. From 2.1 ka BP, the cold-dry climate and human activity resulted in an abrupt increase in C/N with deceased δ^13C value; meanwhile, many coarse grains appeared in sediments.展开更多
Mass microalgal culture plays an irreplaceable role in aquaculture,but microalgal productivity is restricted by traditional autotrophic culture conditions.In the present study,a Tetraselmis chuii strain belonging to t...Mass microalgal culture plays an irreplaceable role in aquaculture,but microalgal productivity is restricted by traditional autotrophic culture conditions.In the present study,a Tetraselmis chuii strain belonging to the phylum Chlorophyta was isolated from south Yellow Sea.The growth rate and biomass productivity of this strain was higher under mixotrophic conditions with different carbon:nitrogen(C:N)ratios than those under autotrophic conditions.When the C:N ratio was 16,the optical density and biomass productivity were 3.7-and 5-fold higher than their corresponding values under autotrophic culture conditions,respectively.Moreover,T.chuii synthesized more polysaccharides and total lipids under mixotrophic conditions.In addition,T.chuii cultured under mixotrophic conditions synthesized more types of fatty acids than autotrophic culture conditions.At a C:N ratio of 16,the percentage of C16:0 and C18:1 reached 30.08%and 24.65%of the total fatty acid(TFA) content,respectively.These findings may provide a basis for largescale mixotrophic culture of T.chuii,as a potential bait-microalga.展开更多
A combined nitritation–anammox reactor was developed to treat the digestion supernatant under various C/N ratios. Due to the difficulties for heterotroph to utilize the refractory organics, the reactor presented rela...A combined nitritation–anammox reactor was developed to treat the digestion supernatant under various C/N ratios. Due to the difficulties for heterotroph to utilize the refractory organics, the reactor presented relatively stable performance with increasing supernatant addition. Nevertheless, the adverse effects of supernatant would accumulate during the long-term operation and thus weakened the activity and shock resistance of microbes,which further led to the gradual decrease of reactor performance after 92 days＇ operation.Under this circumstance, supernatant with volatile fatty acids（VFAs） residuals was further introduced into the reactor to investigate the performance of combined nitritation–anammox process with VFA addition. With the appearance of VFAs, the nitrogen removal performance gradually restored and the reactor finally achieved stable and efficient performance with C/N ratio of 0.35. The VFA residuals within 150 mg/L in the supernatant served as the extra electron donors and stimulated the heterotrophic denitrification process, which was vital for the enhancement of reactor. The nitrogen removal rate and total nitrogen removal efficiency reached 0.49 kg N/（m^3·day） and 88.8% after 140 days＇ operation, respectively. The combined nitritation–anammox reactor was proved suitable to treat digestion supernatant.展开更多
Inspired by the importance of Redfield-type C:N:P ratios in global soils,we looked for analogous patterns in peatlands and aimed at deciphering the potential affecting factors.By analyzing a suite of peatlands soil da...Inspired by the importance of Redfield-type C:N:P ratios in global soils,we looked for analogous patterns in peatlands and aimed at deciphering the potential affecting factors.By analyzing a suite of peatlands soil data(n = 1031),mean soil organic carbon(SOC),total nitrogen(TN) and total phosphorous(TP) contents were 50.51%,1.45% and 0.13%,respectively,while average C:N,C:P and N:P ratios were 26.72,1186.00 and 46.58,respectively.C:N ratios showed smaller variations across different vegetation coverage and had less spatial heterogeneity than C:P and N:P ratios.No consistent C:N:P ratio,though with a general value of 1245:47:1,was found for entire peatland soils in China.The Northeast China,Tibet,Zoigê Plateau and parts of Xinjiang had high soil SOC,TN,TP,and C:P ratio.Qinghai,parts of the lower reaches of the Yangtze River,and the coast zones have low TP and N:P ratio.Significant differences for SOC,TN,TP,C:N,C:P and N:P ratios were observed across groups categorized by predominant vegetation.Moisture,temperature and precipitation all closely related to SOC,TN,TP and their pairwise ratios.The hydrothermal coefficient(RH),defined as annual average precipitation divided by temperature,positively and significantly related to C:N,C:P and N:P ratios,implying that ongoing climate change may prejudice peatlands as carbon sinks during the past 50 years in China.展开更多
Crop yields in sandy soils can be increased by addition of clay-rich soil, but little is known about the effect of clay addition on nutrient availability after addition of plant residues with different C/N ratios. A l...Crop yields in sandy soils can be increased by addition of clay-rich soil, but little is known about the effect of clay addition on nutrient availability after addition of plant residues with different C/N ratios. A loamy sandy soil （7% clay） was amended with a clay-rich subsoil （73% clay） at low to high rates to achieve soil mixtures of 12%, 22%, and 30% clay, as compared to a control （sandy soil alone） with no clay addition. The sandy-clay soil mixtures were amended with finely ground plant residues at 10 g kg-l： mature wheat （Triticum aestivum L.） straw with a C/N ratio of 68, mature faba bean （Vicia faba L.） straw with a C/N ratio of 39, or their mixtures with different proportions （0% 100%, weight percentage） of each straw. Soil respiration was measured over days 0-45 and microbial biomass C （MBC）, available N, and pH on days 0, 15, 30, and 45. Cumulative respiration was not clearly related to the C/N ratio of the residues or their mixtures, but C use efficiency （cumulative respiration per unit of MBC on day 15） was greater with faba bean than with wheat and the differences among the residue mixtures were smaller at the highest clay addition rate. The MBC concentration was lowest in sole wheat and higher in residue mixtures with 50% of wheat and faba bean in the mixture or more faba bean. Soil N availability and soil pH were lower for the soil mixtures of 22% and 30% clay compared to the sandy soil alone. It could be concluded that soil cumulative respiration and MBC concentration were mainly influenced by residue addition, whereas available N and pH were influenced by clay addition to the sandy soil studied.展开更多
A hydroponics experiment was conducted to investigate the rice root growth in FACE （free-air carbon dioxide enrichment）. The root biomass, root volume, ratio of root/shoot, number of adventitious roots and root diam...A hydroponics experiment was conducted to investigate the rice root growth in FACE （free-air carbon dioxide enrichment）. The root biomass, root volume, ratio of root/shoot, number of adventitious roots and root diameter significantly increased under FACE conditions, while the CO2 enrichment decreased the N concentration in rice roots without any change in the C content, leading to an increase in root C：N ratio. Moreover, the elevated CO2 resulted in a remarkable decrease of root activity, expressed as per unit root dry weight, which might be responsible for decreased N concentration in roots.展开更多
基金supported by the National Natural Science Foundation of China(No.31970106).
文摘This study presents a novel approach,the Supercapacitor Microbial Electrolysis Cell(SCMEC),which utilizes a supercapacitor as an external power source to enhance the efficiency of autotrophic nitrogen removal in low C/N ratio wastewater.The results demonstrated that the SC-MEC system,operating under anaerobic conditions and devoid of any organic carbon source,exhibited exceptional performance in ammonia oxidation and total nitrogen(TN)removal when solely relying on ammonia nitrogen as the electron donor.Operating at a voltage of 1.8 V with a capacitance capacity of 30 F,ammonium oxidation rated up to 56.51 mg/L/day and TN removal rated up to 54.64 mg/L/day,in which 97%of ammonium nitrogen was converted to gaseous nitrogen.Furthermore,the charging and discharging process of supercapacitors autonomously regulated the bipolar potentials.Cyclic voltammetry(CV)analysis showed the significantly enhanced electrochemical activity of the SCMEC system during the reaction process.Based on in-situ CV test results,itwas inferred that this enhancementwas associated with extracellular electron transfer mediators.Themicrobial community analysis revealed a process of synchronous nitrification and denitrification(SND)coupled with anammox,involvingmultiple genera,such as Candidatus Kuenenia,Nitrosomonas,Truepera,and Bosea.In conclusion,this study highlights the tremendous potential of SC-MEC in achieving efficient autotrophic nitrogen removal,offering more feasible and economical solutions for addressing low C/N water pollution issues.
基金Supported by National Science and Technology Support Program(2006BAD05B06-04)~~
文摘[Objective]The aim was to study the effects of regulation of C/N ratio wheat straw application on tobacco nitrogen,phosphorus and potassium uptake. [Method]Effects of regulation C/N ratio wheat straw application on the flue-cured tobacco yield,output value,nitrogen,phosphorus and potassium content and cumulative uptake of the upper,middle and bottom leaf were studied by using the field plot experiments at Banqiao town,Qujing city,Yunnan Province during the 2008-2009 summer growing seasons. [Result]The results showed that the application of wheat straw alone or after C/N regulation,could significantly increase tobacco production,potassium content,the potassium and nitrogen accumulation amount of leaf,and was more conducive to the potassium uptake of tobacco leaf with wheat straw application after C/N regulation. Compared with non-straw application,the yield of tobacco increased by 6.59%,3.58%,5.98%,8.80% with application of wheat straw alone,wheat straw and vetch,wheat straw and oilseed cake,wheat straw and urea nitrogen,the potassium content in tobacco leaf increased by 3.85%,7.76%,8.82%,11.21%,respectively,the total potassium cumulative amount of leaf increased by 10.71%,11.62%,15.32% ,21.01% and the total nitrogen cumulative amount increased by 9.76%,1.22%,8.14%,14.00%. However,the differences of tobacco leaf nitrogen content among the different treatments were not significant,the phosphorus uptake of tobacco leaf decreased. [Conclusion]application of high C/N ratio wheat straw in flue-cured tobacco production,which should be concerned not only to adjust C/N ratio by adding nitrogen,but also considering additional phosphorus application.
基金supported by the National Natural Science Foundation of China(31171479)the Key Laboratory Foundation of Jiangsu Province,China(10KJA210057)+2 种基金the Priority Academic Program Development of Jiangsu Higher Education Institutions,China,the Doctoral Advisor Foundation of Education Department of China(20113250110001)the Project of National Agricultural Modern Industrial Technology System Post Experts,China(CARS-18-20)the Graduate Student Scientific Research Innovation Projects of Jiangsu Province,China(CXLX11_1019)
文摘Expression of insecticidal protein for transgenic Bacillus thuringiensis （Bt） cotton is unstable and related to nitrogen metabolism. The objective of this study was to investigate the relationship between leaf carbon nitrogen ratio （C/N） and insecticidal efficacy of two Bt cotton cultivars. C/N ratio and Bt protein content were both measured at peak square period and peak boll period respectively under 5-7 d high temperature and different nitrogen fertilizer rates on the Yangzhou University Farm and the Ludong Cotton Farm, China. All plants were grown in field. The results showed that the C/N ratio enhanced slightly and the Bt protein content remained stable at peak square period, but significant increases for the C/N ratio and decreases markedly for the leaf Bt protein concentration were detected at the peak boll period. The similar patterns at the two growth periods were found for the leaf C/N ratio and Bt protein content by different N fertilizer treatments. When nitrogen rate was from 0 to 600 kg ha-l, the C/N ratio was reduced by 0.017 and 0.006 for Sikang 1 and Sikang 3 at peak square period, compared to the 1.350 to 1.143 reduction for Sikang 1 and Sikang 3 at peak boll period, respectively. Correspondingly, the leaf Bt protein contents were bolstered by 2.6-11.8 and 26.9-36.9% at the two different growth periods, respectively. The results suggested that enhanced C/N ratio by high temperature and nitrogen application may result in the reduction of inseetiocidal efficacy in Bt cotton, especially in peak boll period.
基金This work was supported by the China Agriculture Research System-Green Manure,the Virtual Joint Nitrogen Centre(N-Circle)(No.B B/N 013484/1)the Science and Technology Innovation Project of Chinese Academy of Agricultural Sciences(2013-2017)the Chinese Outstanding Talents Program in Agricultural Science.
文摘Returning rice straw and leguminous green manure alone or in combination to soil is effective in improving soil fertility in South China.Despite the popularity of this practice,our understanding o f the underlying processes for straw and manure combined application is relatively poor.In this study,rice straw(carbon(C)/nitrogen(N)ratio of 63),green manure(hairy vetch,C/N ratio of 14),and their mixtures(C/N ratio of 25 and 35)were added into a paddy soil,and their effects on soil N availability and C or N loss under waterlogged conditions were evaluated in a 100-d incubation experiment.All plant residue treatments significantly enhanced C〇2 and CH4 emissions,but decreased N2O emission.Dissolved organic C(DOC)and N(DON)and microbial biomass C in soil and water-soluble organic C and N and mineral N in the upper aqueous layer above soil were also enhanced by all the plant residue treatments except the rice straw treatment,and soil microbial biomass N and mineral N were lower in the rice straw treatment than in the other treatments.Changes in plant residue C/N ratio,DOC/DON ratio,and cellulose content significantly affected greenhouse gas emissions and active C and N concentrations in soil.Additionally,the treatment with green manure alone yielded the largest C and N losses,and incorporation of the plant residue mixture with a C/N ratio of 35 caused the largest net global warming potential(nGWP)among the amended treatments.In conclusion,the co-incorporation of rice straw and green manure can alleviate the limitation resulting from only applying rice straw(N immobilization)or the sole application of leguminous green manure(high C and N losses),and the residue mixture with a C/N ratio of 25 is a better option because of lower nGWP.
基金Supported by the Yangtze Scholars and Innovative Research Team in University of Ministry of Education of China(No.IRT_17R81)the Technology Support Project of Tianjin(No.16YFZCNC00810)
文摘Biofloc technology has been applied successfully in the intensive aquaculture of several fish and shrimp species. The growth of heterotrophic microorganisms can be stimulated through adding extra carbon, which reduces the nitrogen level in the water and provides microbial protein to the animals. However, most of the studies and practical applications have been conducted in freshwater and marine environment. This paper focused on brine shrimp Artemia that lives in high salinity environment together with other halophilic or halotolerant microorganisms. The effect of carbon supplementation on Artemia growth, water quality, and microbial diversity of biofl ocs was studied in the closed culture condition without any water exchange. The salinity of the culture medium was 100. A 24-d culture trial was conducted through supplementing sucrose at carbon/nitrogen (C/N) ratio of 5, 15, and 30 (Su5, Su15, and Su30), respectively. The culture without adding sucrose was used as a control. Artemia was fed formulated feed at a feeding ration of 60% recommended feeding level. The results showed that sucrose supplementation at higher C/N ratio (15 and 30) signifi cantly improved the Artemia survival, growth and water quality ( P <0.05). Addition of sucrose at C/N ratio of 15 and 30 significantly increased biofloc volume (BFV)( P <0.05). The Illumina MiSeq sequencing analysis showed that supplementing carbon at C/N ratio of 15 had a better total bacterial diversity and richness, and shaped the microbial composition at genera level. This study should provide information for studying the mechanism of biofloc technology and its application in high salinity culture conditions.
文摘Soil organic carbon and nitrogen are used as indexes of soil quality assessment and sustainable land use management. At the same time, soil C/N ratio is a sensitive indicator of soil quality and for assessing the carbon and nitrogen nutrition balance of soils. We studied the characteristics of soil organic carbon and total nitrogen by investigating a large number of apple orchards in major apple production areas in China. High apple orchard soil organic carbon content was observed in the provinces of Heilongjiang, Xinjiang, and Yunnan, whereas low content was found in the provinces of Shandong, Henan, Hebei, and Shaanxi, with the values ranging between 6.44 and 7.76 g·kg-1. Similar to soil organic carbon, soil total nitrogen content also exhibited obvious differences in the 12 major apple producing provinces. Shandong apple orchard soil had the highest total nitrogen content (1.26 g·kg-1), followed by Beijing (1.23 g·kg-1). No significant difference was noted between these two regions, but their total nitrogen content was significantly higher than the other nine provinces, excluding Yunnan. The soil total nitrogen content for Xinjiang, Heilongjiang, Hebei, Henan, and Gansu was between 0.87 and 1.03 g·kg-1, which was significantly lower than that in Shandong and Beijing, but significantly higher than that in Liaoning, Shanxi, and Shaanxi. Six provinces exhibited apple orchard soil C/N ratio higher than 10, including Heilongjiang (15.42), Xinjiang (13.38), Ningxia (14.45), Liaoning (12.24), Yunnan (11.03), and Gansu (10.63). The soil C/N ratio was below 10 in the remaining six provinces, in which the highest was found in Shaanxi (9.47), followed by Beijing (8.98), Henan (7.99), and Shanxi (7.62), and the lowest was found in Hebei (6.80) and Shandong (6.05). Therefore, the improvement of soil organic carbon should be given more attention to increase the steady growth of soil C/N ratio.
文摘Microbial activity and nutrient release are known to be influenced by organic matter properties,but it is difficult to separate the effect of C/N ratio from that of C/P ratio because in most plant residues both ratios are either high or low.An incubation experiment was conducted to investigate the effects of reducing the C/N and C/P ratios of slowly decomposable plant residues(young eucalyptus leaves,mature wheat straw,and sawdust) to those of rapidly decomposable residues(young kikuyu shoots) on soil respiration,microbial biomass,and N and P availability.The C/N and C/P ratios of the former were adjusted to 15 and 89,respectively,by adding N as(NH_4)_2SO_4,P as KH_2PO_4 or both and residues were added at 10 g C kg-1 to a silt loam.Soil respiration was measured over21 d;microbial biomass C(MBC) and available N and P were measured on days 0,7,and 21.Compared to the unamended soil,addition of kikuyu increased cumulative respiration 20-fold,MBC concentration 4 to 8-fold,and available P concentration up to4-fold,whereas the increase in available N concentration was small and transient.Cumulative respiration and MBC concentration were low in the sawdust-amended soil and were not influenced by reducing the C/N and C/P ratios.Cumulative respiration with original wheat and eucalyptus was 30%-40%of that with kikuyu.Reducing the C/N ratio alone or both C/N and C/P ratios increased cumulative respiration and MBC concentration 2-fold compared to the original wheat and eucalyptus,whereas reducing the C/P ratio had little effect.Throughout the experiment,the available N concentration after addition of residues with reduced C/N ratio increased in the following order of eucalyptus < wheat < sawdust.By independently lowering the C/N and C/P ratios,microbial activity was more limited by C and N than P.However,lowering the C/N ratio of very slowly decomposable sawdust had no effect on soil respiration and MBC concentration,suggesting that other properties such as concentration of poorly decomposable C compounds limited decomposition.
基金funded by the National Natural Science Foundation of China (31871584)the Agricultural Science and Technology Innovation Program, Chinese Academy of Agricultural Sciences (CAAS-ZDRW202201)+2 种基金the Fundamental Research Funds for Central Non-profit Scientific Institution, China (1610132020011)the “Open the list” in charge of the Science and Technology Project of Ordos, Center for Agro-pastoral Ecology and Resource Conservation of Ordos City, Inner Mongolia, China (JBGS2021-001)the Inner Mongolia Autonomous Region Research Project (2021EEDSCXSFQZD011)。
文摘Soil salinization is a critical environmental issue restricting agricultural production.Deep return of straw to the soil as an interlayer (at 40 cm depth) has been a popular practice to alleviate salt stress.However,the legacy effects of straw added as an interlayer at different rates on soil organic carbon (SOC) and total nitrogen (TN) in saline soils still remain inconclusive.Therefore,a four-year (2015–2018) field experiment was conducted with four levels (i.e.,0,6,12and 18 Mg ha~(–1)) of straw returned as an interlayer.Compared with no straw interlayer (CK),straw addition increased SOC concentration by 14–32 and 11–57%in the 20–40 and 40–60 cm soil layers,respectively.The increases in soil TN concentration (8–22 and 6–34%in the 20–40 and 40–60 cm soil layers,respectively) were lower than that for SOC concentration,which led to increased soil C:N ratio in the 20–60 cm soil depth.Increases in SOC and TN concentrations in the 20–60 cm soil layer with straw addition led to a decrease in stratification ratios (0–20 cm:20–60 cm),which promoted uniform distributions of SOC and TN in the soil profile.Increases in SOC and TN concentrations were associated with soil salinity and moisture regulation and improved sunflower yield.Generally,compared with other treatments,the application of 12 Mg ha~(–1) straw had higher SOC,TN and C:N ratio,and lower soil stratification ratio in the2015–2017 period.The results highlighted that legacy effects of straw application as an interlayer were maintained for at least four years,and demonstrated that deep soil straw application had a great potential for improving subsoil fertility in salt-affected soils.
基金the Ministry of Science and Technology of the Republic of China(Taiwan)for the financial support(No.102-2221-E-009-010-MY3)
文摘The effects of C/N ratio of a nitrate-containing wastewater on nitrate removal performed by autohydrogenotrophic bacteria as well as on the morphological parameters of floc such as floc morphology, floc number distribution, mean particle size（MPS）, aspect ratio and transparency were examined in this study. The results showed that the nitrate reduction rate increased with increasing C/N ratio from 0.5 to 10 and that the nitrogen removal of up to 95% was found at the C/N ratios of higher than 5（between 0.5–10）. Besides, high C/N ratio values reflected a corresponding high nitrite accumulation after 12-hr operation, and a fast decreasing rate of nitrite in the rest of operational time. The final p H values increased with the C/N ratio increasing from 0.5 to 2.5, but decreased with the C/N ratio increasing from2.5 to 10. There were no significant changes in floc morphology with the MPSs ranging from35 to 40 μm. Small and medium-sized flocs were dominant in the sludge suspension, and the number of flocs increased with the increasing C/N ratios. Furthermore, the highest apparent frequency of 10% was observed at aspect ratios of 0.5 and 0.6, while the transparency of flocs changed from 0.1 to 0.7.
基金supported by National Science and Technology Major Project Water:Pollution Control and Treatment(No.2012ZX07202006)。
文摘External organic carbon sources are needed to provide electron donors for the denitrification of wastewater with a low COD/NO_(3)^(-)-N(C/N)ratio,increasing the treatment cost.The economic strategy is to enhance the bioactivity and/or biodiversity of denitrifiers to efficiently utilize organic substances in wastewater.In this study,novel zero-valent iron(ZVI)composite carriers were prepared and implemented in a suspended carrier biofilm reactor to enhance the bioactivity and/or biodiversity of denitrifiers.At the influent C/N ratio of 4(COD was 179.5±5.0 mg/L and TN was 44.2±0.8 mg/L),COD and TN removal efficiencies were 85.1%and 66.4%,respectively,in the reactors filled with 3 wt%ZVI composite carriers.In contrast,COD and TN removal efficiencies were 70.4%and 55.3%,respectively,in the reactor filled with conventional high-density polyethylene(HDPE)biofilm carriers.The biofilm formation on the 3 wt%ZVI composite carriers was optimized due to its higher roughness(surface square roughness increased from 76.0 nm to 93.8 nm)and favorable hydrophilicity(water contact angle dropped to 72.5°±1.4°from 94.3°±3.2°)compared with the HDPE biofilm carriers.In addition,heterotrophic denitrifiers,Thauera and Dechloromonas,were enriched,whereas autotrophic denitrifiers,Raoultella and Thiobacillus,exhibited high relative abundance in the biofilm of ZVI composite carriers.The coexistence of heterotrophic denitrifiers and autotrophic denitrifiers on the surface of ZVI composite carriers provided mixotrophic metabolism of denitrification(including heterotrophic and iron-based autotrophic),thereby ensuring effective denitrification for wastewater with a low C/N ratio without external organic carbon source addition.
基金This work was supported by the National Key Research and Development Program of China(No.2018 YFC1407601)the Start-up Foundation for Introducing Talent of NUIST and Guangxi Innovation Driven Development Project(major science and technology project).
文摘In order to explore the effect of carbon and nitrogen(C/N)ratio on the performance of anoxic/aerobic-moving bed bio-film reactor(A/O-MBBR)process for treating mariculture wastewater,a laboratory-scale A/O-MBBR was conducted.The results showed that the reduction of C/N ratio was conducive to improving the removal efficiency of chemical oxygen demand(COD)and ammonia nitrogen(NH_(4)^(+)-N),while inhibiting that of nitrite nitrogen(NO_(2)^(−)-N)and nitrate nitrogen(NO_(3)^(−)-N).The extracellular polymeric substances(EPS)in anoxic zone were significantly higher in concentration than that in aerobic zone although they both declined with decrease of C/N ratio.The result provides solid support for better controlling the pollution of mariculture wastewater.
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education(SRFDP200807181008)the Science Fund of Shaanxi Normal University for the Young Scholars,China
文摘In forage grasses, the nitrogen concentration is directly related to the nutritional value. The studies examined the hypothesis that global elevation of CO2 concentration probably affects the biomass, nitrogen （N） concentration, and allocation and distribution patterns in the organs of forage grasses. While sainfoin （Onobrychis viciaefolia Scop.） seedlings grew on a low nutrient soil in closed chambers for 90 days, they were exposed to two CO2 concentrations （ambient or ambient＋350 μmol mol^-1 CO2） without adding nutrients to them. After 90 days exposure to CO2, the biomasses of leaves, stems, and roots, and N concentrations and contents of different parts were measured. Compared with the ambient CO2 concentration, the elevated CO2 concentration increased the total dry matter by 25.07%, mainly due to the root and leaf having positive response to the elevated CO2 concentration. However, the elevated CO2 concentration did not change the proportions of the dry matters in different parts and the total plants compared with the ambient CO2 concentration. The elevated CO2 concentration lowered the N concentrations of the plant parts. Because the dry matter was higher, the elevated CO2 concentration had no effect on the N content in the plants compared to the ambient CO2 concentration. The elevated CO2 concentration promoted N allocations of the different parts significantly and increased N allocation of the underground part. The results have confirmed the previous suggestions that the elevated CO2 concentration stimulates plant biomass production and decreases the N concentrations of the plant parts.
基金Supported by National Key Basic Research Fund (No. 2004CB720205) and National Nature and Science Foundation of China (No. 40331003).
文摘On the basis of multi-proxy analysis on TOC, TN, C/N, organic δ^13C and grain size, sediment record from Qinghai Lake provides evidences of stepwise-pattemed climatic change since 16 ka BE Results show that Qinghai Lake underwent six environmental stages. From 16.2 to 14.3 ka BP and from 4.0 to 2.1 ka BP, the organic δ^13C value was controlled by the concentration of atmospheric CO2. Relative higher organic δ^13C values occurred between 14.3 to 10.4 ka BP indicative of water hardness decrease resulted from melting ice water, corresponding to two intervals of C/N peak values to the Boling and AIlerod warm periods in Europe respectively. From 10.4 ka BP, Qinghai Lake entered the Holocene and the climate was warm and a little dry. The Megathermal appeared at about 6.7 ka BP when the vegetation around the lake transformed into a forest. Between 6.3 ka BP and 4.0 ka BP, the temperature decreased and δ^13C value was controlled by the expansion of C3 plants and the retreat of C4 plants in river catchment. Since 4.0 ka BP, the climate gradually became cold and dry. From 2.1 ka BP, the cold-dry climate and human activity resulted in an abrupt increase in C/N with deceased δ^13C value; meanwhile, many coarse grains appeared in sediments.
基金Supported by the National Basic Research Program of China(973Program)(Nos.2011CB200901,2011CB200904)the National Key Technology Research and Development Program(No.2011BAD14B01)+1 种基金the National High Technology Research and Development Program of China(863 Program)(No.2013AA065801)the Special Foundation for Marine Renewable Energy(No.GHME2011SW03)
文摘Mass microalgal culture plays an irreplaceable role in aquaculture,but microalgal productivity is restricted by traditional autotrophic culture conditions.In the present study,a Tetraselmis chuii strain belonging to the phylum Chlorophyta was isolated from south Yellow Sea.The growth rate and biomass productivity of this strain was higher under mixotrophic conditions with different carbon:nitrogen(C:N)ratios than those under autotrophic conditions.When the C:N ratio was 16,the optical density and biomass productivity were 3.7-and 5-fold higher than their corresponding values under autotrophic culture conditions,respectively.Moreover,T.chuii synthesized more polysaccharides and total lipids under mixotrophic conditions.In addition,T.chuii cultured under mixotrophic conditions synthesized more types of fatty acids than autotrophic culture conditions.At a C:N ratio of 16,the percentage of C16:0 and C18:1 reached 30.08%and 24.65%of the total fatty acid(TFA) content,respectively.These findings may provide a basis for largescale mixotrophic culture of T.chuii,as a potential bait-microalga.
基金supported by the Mega-Projects of Science Research for Water Environment Improvement (No. 2012ZX07205-001)
文摘A combined nitritation–anammox reactor was developed to treat the digestion supernatant under various C/N ratios. Due to the difficulties for heterotroph to utilize the refractory organics, the reactor presented relatively stable performance with increasing supernatant addition. Nevertheless, the adverse effects of supernatant would accumulate during the long-term operation and thus weakened the activity and shock resistance of microbes,which further led to the gradual decrease of reactor performance after 92 days＇ operation.Under this circumstance, supernatant with volatile fatty acids（VFAs） residuals was further introduced into the reactor to investigate the performance of combined nitritation–anammox process with VFA addition. With the appearance of VFAs, the nitrogen removal performance gradually restored and the reactor finally achieved stable and efficient performance with C/N ratio of 0.35. The VFA residuals within 150 mg/L in the supernatant served as the extra electron donors and stimulated the heterotrophic denitrification process, which was vital for the enhancement of reactor. The nitrogen removal rate and total nitrogen removal efficiency reached 0.49 kg N/（m^3·day） and 88.8% after 140 days＇ operation, respectively. The combined nitritation–anammox reactor was proved suitable to treat digestion supernatant.
基金Under the auspices of National Key Research Program of China(No.2016YFC0500404-5)National Natural Science Foundation of China(No.41671081,41471081,41671087)Foundation of Jilin Province(No.20140520141JH)
文摘Inspired by the importance of Redfield-type C:N:P ratios in global soils,we looked for analogous patterns in peatlands and aimed at deciphering the potential affecting factors.By analyzing a suite of peatlands soil data(n = 1031),mean soil organic carbon(SOC),total nitrogen(TN) and total phosphorous(TP) contents were 50.51%,1.45% and 0.13%,respectively,while average C:N,C:P and N:P ratios were 26.72,1186.00 and 46.58,respectively.C:N ratios showed smaller variations across different vegetation coverage and had less spatial heterogeneity than C:P and N:P ratios.No consistent C:N:P ratio,though with a general value of 1245:47:1,was found for entire peatland soils in China.The Northeast China,Tibet,Zoigê Plateau and parts of Xinjiang had high soil SOC,TN,TP,and C:P ratio.Qinghai,parts of the lower reaches of the Yangtze River,and the coast zones have low TP and N:P ratio.Significant differences for SOC,TN,TP,C:N,C:P and N:P ratios were observed across groups categorized by predominant vegetation.Moisture,temperature and precipitation all closely related to SOC,TN,TP and their pairwise ratios.The hydrothermal coefficient(RH),defined as annual average precipitation divided by temperature,positively and significantly related to C:N,C:P and N:P ratios,implying that ongoing climate change may prejudice peatlands as carbon sinks during the past 50 years in China.
基金supported by a postdoctoral award of Australian Department of Education and Training Endeavour to S. Pal
文摘Crop yields in sandy soils can be increased by addition of clay-rich soil, but little is known about the effect of clay addition on nutrient availability after addition of plant residues with different C/N ratios. A loamy sandy soil （7% clay） was amended with a clay-rich subsoil （73% clay） at low to high rates to achieve soil mixtures of 12%, 22%, and 30% clay, as compared to a control （sandy soil alone） with no clay addition. The sandy-clay soil mixtures were amended with finely ground plant residues at 10 g kg-l： mature wheat （Triticum aestivum L.） straw with a C/N ratio of 68, mature faba bean （Vicia faba L.） straw with a C/N ratio of 39, or their mixtures with different proportions （0% 100%, weight percentage） of each straw. Soil respiration was measured over days 0-45 and microbial biomass C （MBC）, available N, and pH on days 0, 15, 30, and 45. Cumulative respiration was not clearly related to the C/N ratio of the residues or their mixtures, but C use efficiency （cumulative respiration per unit of MBC on day 15） was greater with faba bean than with wheat and the differences among the residue mixtures were smaller at the highest clay addition rate. The MBC concentration was lowest in sole wheat and higher in residue mixtures with 50% of wheat and faba bean in the mixture or more faba bean. Soil N availability and soil pH were lower for the soil mixtures of 22% and 30% clay compared to the sandy soil alone. It could be concluded that soil cumulative respiration and MBC concentration were mainly influenced by residue addition, whereas available N and pH were influenced by clay addition to the sandy soil studied.
基金National Natural Science Foundation of China （nos. 40231003 , 40110817） Knowledge Innovation Program of Chinese Academy of Sciences （no. KZCX2-408） the National Key Project on Basic Sciences （no. 2002CB714003）.
文摘A hydroponics experiment was conducted to investigate the rice root growth in FACE （free-air carbon dioxide enrichment）. The root biomass, root volume, ratio of root/shoot, number of adventitious roots and root diameter significantly increased under FACE conditions, while the CO2 enrichment decreased the N concentration in rice roots without any change in the C content, leading to an increase in root C：N ratio. Moreover, the elevated CO2 resulted in a remarkable decrease of root activity, expressed as per unit root dry weight, which might be responsible for decreased N concentration in roots.
