Single-step nitrification models erroneously describe batch ammonia oxidation profiles when nitrite oxidation becomes rate limiting

Nitrification involves the sequential biological oxidation of reduced nitrogen species such as ammonium-nitrogen (NH(4)(+)-N) to nitrite-nitrogen (NO(2)(-)-N) and nitrate-nitrogen (NO(3)(-)-N). The adequacy of modeling NH(4)(+)-N to NO(3)(-)-N oxidation as one composite biochemical reaction was examined at different relative dynamics of NH(4)(+)-N to NO(2)(-)-N and NO(2)(-)-N to NO(3)(-)-N oxidation. NH(4)(+)-N to NO(2)(-)-N oxidation and NO(2)(-)-N to NO(3)(-)-N oxidation by a mixed nitrifying consortium were uncoupled using selective inhibitors allylthiourea and sodium azide. The kinetic parameters of NH(4)(+)-N to NO(2)(-)-N oxidation (q(max,ns) and K(S,ns)) and NO(2)(-)-N to NO(3)(-)-N oxidation (q(max,nb) and K(S,nb)) were determined by a rapid extant respirometric technique. The stoichiometric coefficients relating nitrogen removal, oxygen uptake and biomass synthesis were derived from an electron balanced equation. NH(4)(+)-N to NO(2)(-)-N oxidation was not affected by NO(2)(-)-N concentrations up to 100 mg NO(2)(-)-N L(-1). NO(2)(-)-N to NO(3)(-)-N oxidation was noncompetitively inhibited by NH(4)(+)-N but was not inhibited by NO(3)(-)-N concentrations up to 250 mg NO(3)(-)-N L(-1). When NH(4)(+)-N to NO(2)(-)-N oxidation was the sole rate-limiting step, complete NH(4)(+)-N to NO(3)(-)-N oxidation was adequately modeled as one composite process. However, when NH(4)(+)-N to NO(2)(-)-N oxidation and NO(2)(-)-N to NO(3)(-)-N oxidation were both rate limiting, the estimated lumped kinetic parameter estimates describing NH(4)(+)-N to NO(3)(-)-N oxidation were unrealistically high and correlated. These findings indicate that the use of single-step models to describe batch NH(4)(+) oxidation yields erroneous kinetic parameters when NH(4)(+)-to-NO(2)(-) oxidation is not the sole rate-limiting process throughout the assay. Under such circumstances, it is necessary to quantify NH(4)(+)-N to NO(2)(-)-N oxidation and NO(2)(-)-N to NO(3)(-)-N oxidation, independently.     

长期施肥条件下黄土旱塬土壤N03^--N的淋溶分布规律

在黄土旱塬区,长期施肥对土壤剖面NO3^-1—N含量和分布有显著影响．施用化学氮肥,土壤剖面中出现NO3^-1—N的淋溶与深层累积,而施用磷肥和有机肥有减弱NO3^-1—N向更深层淋溶的作用．单施氮肥处理(N),NO3^-1—N的累积峰深度最大,为120～200cm;N、P有机肥配施处理(NPM),NO3^-1—N的累积峰值最高,但峰深度降低至60～120cm;N、P配施(NP)累积深度为80～140cm．不施氮肥,分布在土壤剖面中NO3^-1—N含量显著降低．氮肥用量愈大,NO3^-1—N的累积量愈大．N、P配施可以有效降低NO3^-1—N累积．在同一氮肥用量下,NO3^-1—N累积量随磷肥用量的增加而减少．     

Influence of nitrate and COD on phosphorus, nitrogen and dinitrotoluene (DNT) removals under batch anaerobic and anoxic conditions

In this study, the effects of COD to NO(3)-N ratio in the feed on PO(4)-P removal was investigated. Maximum PO(4)-P uptake was obtained in the anoxic reactor when the COD to NO(3)-N ratios were between 2 and 3.75. With the influent COD of 800-1500 mg COD/L a total of the maximum removable PO(4)-P was 56 mg PO(4)-P/L through 20 days of anaerobic/anoxic incubation, indicating 98% P removal in the anoxic reactor. Similarly, for the COD to NO(3)-N ratios varying between 2 and 3.75 maximum denitrification was observed. Through anoxic operation the poly-P bacteria are capable of removing NO(3)-N using VFA, COD as carbon source and NO(3)-N as the electron acceptor after methanogenesis has been completed. High NO(3)-N concentrations stopped significantly the P uptake. A total of 97-99% dinitrotoluene removal efficiencies in the reactors containing COD to NO(3)-N ratio of 2 and 3.75 after 20 days of incubation period. For maximum NO(3)-N and PO(4)-P removals optimal COD to NO(3)-N ratios, COD and NO(3)-N concentrations were 2-3.75, 2000-4000 mg COD/L and, 800-1500 mg NO(3)-N/L, respectively.     

莴笋对不同形态氮素的反应

探讨了不同形态氮素对莴笋生长发育的影响及其营养特性。结果表明,莴笋幼苗根系对NH4^+ -N的亲和力稍大于NO3^- -N的亲和力;分别供给NO3^- -N+NO3^- -N及NH4^+ -N,莴笋的生物学产量和吸N量均依次递减（分别为100：56.9：12.4,100：48.9：8.6）,因此在水培条件下,NO3^- -N是最适合莴笋生长发育的氮源,NH4^+ -N与NO3^- -N各占50％时对莴笋的生长发育已有一定的抑制作用,仅以NH4^+ -N作氮源则莴笋很难生长;NH4^+ -N与NO3^- -N各占50％时,莴笋倾向于吸收较多的NH4^+ -N,而且在培养不同阶段NH4^+/NO3^-吸收比例均大于1,莴笋表现出喜铵性,但NH4^+ -N并非莴笋很适合的氮源;营养液中NO3^- -N不足,主要影响莴笋茎叶的生长,而NH4^+ -N所占比例达50％时,莴笋根系生长受到抑制,且有明显的受害症状;以NO3^- -N作氮源预培养两周,以含微量NO3^- -N的自来水为水源,再单独以NH4^+ -N为氮源,对莴笋生长有极大的促进作用,同时还大幅度降低了体内硝酸盐的含量。尿素作氮源莴笋未出现受害症状,但莴笋的生长发育状况明显劣于其它氮源。     

Ammonium oxidation via nitrite accumulation under limited oxygen concentration in sequencing batch reactors

In this study, the effects of sludge retention time (SRT) on NH(4)-N oxidation and NO(x)-N accumulation in the nitritation reactors were studied. The gradually decrease of SRT also caused long reaction time to achieve 99% NH(4)-N removal. Although the target NH(4)-N removal was achieved in a short reaction time at 40 days of SRT, decreasing of SRT from 40 to 30, 25, 20 days, increase the reaction time from 168 to 240 and 265 h, respectively. The inlet NH(4)-N was almost oxidized and the concentration of NO(2)-N accumulated to a high level of 177 mg/l, while NO(2)-N/(NO(3)-N+NO(2)-N) ratio was about 0.9 at SRT of 40 days. However, the concentration of NO(3)-N increased slightly and NO(2)-N/(NO(x)-N) ratio dropped to 0.8 when the SRT was lower than 40 days. During the operation in a cycle, free ammonia concentration in the SBR was decreased from 2.8 to 0.7 mg/l which is below the lowest concentration causing inhibition of nitrite oxidizing bacteria (NOB). It was assumed that combined dissolved oxygen limitation and NH(3)-N inhibition on NOB caused NO(2)-N accumulation under the experimental conditions.     

Denitrification of high strength nitrate waste

The aim of the present work was to study the treatment of high strength nitrate waste (40000 ppm NO(3) i.e., 9032 ppm NO(3)-N) by acclimatizing sludge initially capable of degrading dilute streams (100-200 ppm NO(3)-N). Sludge from an effluent treatment plant of a fertilizer industry was acclimatized for 15 d each at 1694, 3388, 6774 and 9032 ppm NO(3)-N in a 4 L sequencing batch reactor. Complete denitrification of extremely concentrated nitrate waste (9032 ppm NO(3)-N) using acclimatized sludge was achieved in just 6 h. During the acclimatization period, increase in nitrite peak value from zero to 5907 ppm NO(2)-N was observed, as the concentration was increased from 1694 to 9032 ppm NO(3)-N. Kinetic analysis of the nitrate and nitrite profile could reasonably support microbiological explanations for nitrite build up and changes in sludge composition.     

Applicability of two-step models in estimating nitrification kinetics from batch respirograms under different relative dynamics of ammonia and nitrite oxidation

A mechanistically based nitrification model was formulated to facilitate determination of both NH(4)(+)-N to NO(2)(-)-N and NO(2)(-)-N to NO(3)(-)-N oxidation kinetics from a single NH(4)(+)-N to NO(3)(-)-N batch-oxidation profile by explicitly considering the kinetics of each oxidation step. The developed model incorporated a novel convention for expressing the concentrations of nitrogen species in terms of their nitrogenous oxygen demand (NOD). Stoichiometric coefficients relating nitrogen removal, oxygen uptake, and biomass synthesis were derived from an electron-balanced equation.%A parameter identifiability analysis of the developed two-step model revealed a decrease in correlation and an increase in the precision of the kinetic parameter estimates when NO(2)(-)-N oxidation kinetics became increasingly rate-limiting. These findings demonstrate that two-step models describe nitrification kinetics adequately only when NH(4)(+)-N to NO(3)(-)-N oxidation profiles contain sufficient information pertaining to both nitrification steps. Thus, the rate-determining step in overall nitrification must be identified before applying conventionally used models to describe batch nitrification respirograms.     

有机酸去除污泥重金属前后硝态氮和铵态氮浓度变化

研究了柠檬酸、草酸和乙酸溶液对污泥中重金属(Cd、Pb、Cu和Zn)的去除效果,以及处理前后析出液和污泥中硝态氮和铵态氮的浓度变化.结果表明,0.8mol.L-1柠檬酸溶液可去除污泥中76.0%的Pb和92.5%的Zn,是较好的重金属去除剂.污泥经有机酸处理后,有大量的硝态氮和铵态氮溶解于析出液中,与加入蒸馏水的对照处理相比,有机酸可大幅度增加析出液中铵态氮的含量,减少硝态氮含量.由于污泥处理过程中有其他形态的氮的转化,处理后污泥中仍含有较高浓度的硝态氮和铵态氮.0.5mol.L-1草酸处理的析出液中硝态氮和铵态氮浓度分别为2.8和888.1mg.L-1,且重金属含量不高,可作为较好的液体肥料进行回收利用.     

关于好氧反硝化菌筛选方法的研究

采用污泥驯化手段富集好氧反硝化细菌,将得到的驯化污泥分离纯化,共得到105株菌。用测TN的方法对所筛菌株进行初筛,得到25株对TN去除率达到50％以上的菌株。用氮元素轨迹跟踪测定法复筛,证实这25株菌都可以在好氧条件下进行硝酸盐呼吸,其中24株菌的反硝化过程为：NO3^-N→NO2^-N→N2,研究中还发现在反硝化过程中硝酸盐和亚硝酸盐不存在明显竞争被利用的作用。同时还提出了可能实现短程同步硝化反硝化以及在反馈作用的调节下,加快硝化反应速度的观点。     

林下植被去除与氮添加对樟子松人工林土壤化学和生物学性质的影响

通过析因试验设计,研究了科尔沁沙地樟子松人工林生态系统内土壤无机氮(NO3--N+NH4+-N)含量,潜在净氮矿化(PNM)、硝化速率(PNN),微生物生物量碳(MBC)、氮(MBN)及MBC/MBN,土壤脲酶、酸性磷酸单酯酶活性和土壤有效磷(Olsen-P)含量对林下植被管理(对照和去除)和氮添加(对照和添加8g·m-2)的短期响应.结果表明:林下植被去除显著降低了土壤NH4+-N含量、PNM、MBC和MBC/MBN比值,提高了土壤Olsen-P含量,而对土壤NO3--N含量、PNN和土壤酶活性的影响不显著.氮添加提高了土壤NO3--N含量、PNM和PNN,但对其他指标的影响不明显,可能与试验处理时间较短有关.土壤NH4+-N含量对林下植被去除与氮添加的交互作用的响应显著;而NO3--N含量虽对林下植被去除与氮添加处理的交互作用响应不显著,但在氮添加同时进行林下植被去除的样地中的土壤NO3--N含量比只进行氮添加处理的样地提高了27％,有可能导致土壤中NO3-的淋失.林下植被是影响樟子松人工林土壤化学和微生物学性质的重要因素,因此在森林管理和恢复过程中,不能忽视林下植被的作用.     

三江平原小叶樟和毛果苔草中N素营养动态分析

讨论了沼泽湿地优势种小叶樟（Ｃａｌａｍａｇｒｏｓｔｉｓ ａｎｇｕｓｔｉｆｏｌｉａ）和毛果苔草（Ｃａｒｅｘ ｌａｓｉｏｃａｒｐａ）生物量和生长率变化情况,不同生长期各器官中Ｎ素含量及储量动态变化,以及植物对Ｎ素利用和区域养分限制情况。结果表明,两种植物地上生物量生长符合模式ｐ＝γ＋ａｔ＋βｔ＾２,地下生物量符合曲线ｐ＋ａ０＋ｂ０ｔ;受土壤水分、养分、气温和植物本身特点及其对Ｎ素选择吸收作用等多种因素     

成垄压实施肥对氮素运移及氮肥利用率的影响

黄土高原地区夏玉米生长正逢雨季,是N素淋溶的主要时期,为此提出氮肥施用的成垄压实法,通过连续两年的田间小区试验,研究了夏玉米生长期成垄压实施肥方式下夏玉米产量和氮肥利用率,以及土壤NO3^--N迁移规律,并结合室内模拟实验探讨了该施肥法的影响因素。结果表明,在供水量接近研究区同期多年平均降雨量(370mm)的年份,平地施肥条件下,NO3^--N可被淋溶至90cm以下的土层;而成垄压实施肥可明显减少施肥区NO3^--N随入渗水分向土壤深层迁移,至60cm以下土层,土壤NO3^--N含量小于10mg·kg^-1,NO3^--N主要累积于近地表20～40cm土层,该土层土壤NO3^--N含量约为80～90mg·kg^-1。成垄压实施肥法局部存在的大容重障碍层对作物生长发育无影响在240.0kgN·hm^-2施氮量条件下,成垄压实较平地施肥没有显著提高玉米生物产量和经济产量,但却能极显著地增加作物吸氮量,使氮肥利用率提高9％左右。成垄压实施肥条件下,障碍层容重对NO3^--N迁移影响明显,随障碍层容重的增加,NO3^--N迁移深度减小,大田条件下,垄坡度对NO3^--N迁移影响不明显。     

Simultaneous removal of carbon and nitrate in an airlift bioreactor

This paper presents the integrated removal of carbon (measured as chemical oxygen demand i.e. COD) and NO(x)-N by sequentially adapted sludge, studied in an airlift reactor (ALR). Simultaneous removal of COD and nitrate occurs by denitrification (anoxic) and oxidation (aerobic). Aerobic (riser) and anoxic (remaining part) conditions prevail in different parts of the reactor. Studies were carried out in a 42 L ALR operated at low aeration rate to maintain anoxic and aerobic conditions as required for denitrification and COD removal, respectively. The sludge was adapted sequentially to increasing levels of NO(x)-N and COD over a period of 45 days. Nitrate removal efficiency of the sludge increased due to adaptation and degraded 900 ppm NO(3)-N completely in 2h (initially the sludge could not degrade 100 ppm NO(3)-N). The performance of the adapted sludge was tested for the degradation of synthetic waste with COD/N loadings in the range of 4-10. The reduction of COD was significantly faster in the presence of NO(x)-N and was attributed to the availability of oxygen from NO(x)-N and distinct conditions in the reactor. This hypothesis was justified by the material balance of COD.     

Is there synchronicity in nitrogen input and output fluxes at the Noland Divide Watershed,a small N-saturated forested catchment in the Great Smoky Mountains National Park?

High-elevation red spruce [Picea rubens Sarg.]-Fraser fir [Abies fraseri (Pursh.) Poir] forests in the Southern Appalachians currently receive large nitrogen (N) inputs via atmospheric deposition (30 kg N ha(-1) year(-1)) but have limited N retention capacity due to a combination of stand age, heavy fir mortality caused by exotic insect infestations, and numerous gaps caused by windfalls and ice storms. This study examined the magnitude and timing of the N fluxes into, through, and out of a small, first-order catchment in the Great Smoky Mountains National Park. It also examined the role of climatic conditions in causing interannual variations in the N output signal. About half of the atmospheric N input was exported annually in the streamwater, primarily as nitrate (NO3-N). While most incoming ammonium (NH4-N) was retained in the canopy and the forest floor, the NO3-N fluxes were very dynamic in space as well as in time. There was a clear decoupling between NO3-N input and output fluxes. Atmospheric N input was greatest in the growing season while largest NO3-N losses typically occurred in the dormant season. Also, as water passed through the various catchment compartments, the NO3-N flux declined below the canopy, increased in the upper soil due to internal N mineralization and nitrification, and declined again deeper in the mineral soil due to plant uptake and microbial processing. Temperature control on N production and hydrologic control on NO3-N leaching during the growing season likely caused the observed inter-annual variation in fall peak NO3-N concentrations and N discharge rates in the stream.     

氮素形态对黄檗幼苗生长及氮代谢相关酶类的影响

通过改变水培溶液中NH4+-N和NO3--N的比例, 研究了不同氮素形态对黄檗(Phellodendron amurense)幼苗生长及氮代谢相关酶类的影响。结果表明, 硝态氮比例较高的营养供给比铵态氮比例较高的营养供给有利于黄檗幼苗的生长, 叶片叶绿素含量和可溶性蛋白含量也高。在NH4+-N/NO3--N为25/75 时黄檗幼苗具有最大生物量。在铵态氮比例大的营养供给下, 黄檗幼苗的谷氨酰胺合成酶(GS)活性增强,而在硝态氮比例大的营养供给下幼苗的硝酸还原酶(NR)活性则较高, 叶片中的硝态氮较低。营养液的氮素形态及其组成通过影响GS与NR的活性而调控黄檗幼苗的氮素代谢。     

氮素形态对黄檗幼苗生长及氮代谢相关酶类的影响

通过改变水培溶液中NH4^＋-N和NO3^--N的比例,研究了不同氮素形态对黄檗（Phellodendron amurense）幼苗生长及氮代谢相关酶类的影响。结果表明,硝态氮比例较高的营养供给比铵态氮比例较高的营养供给有利于黄檗幼苗的生长,叶片叶绿素含量和可溶性蛋白含量也高。在NH4^＋-N／NO3^--N为25／75时黄檗幼苗具有最大生物量。在铵态氮比例大的营养供给下,黄檗幼苗的谷氨酰胺合成酶（GS）活性增强,而在硝态氮比例大的营养供给下幼苗的硝酸还原酶（NR）活性则较高,叶片中的硝态氮较低。营养液的氮素形态及其组成通过影响GS与NR的活性而调控黄檗幼苗的氮素代谢。     

Effects of Nitrate Availability and the Presence of Glyceria maxima on the Composition and Activity of the Dissimilatory Nitrate-Reducing Bacterial Community

The effects of nitrate availability and the presence of Glyceria maxima on the composition and activity of the dissimilatory nitrate-reducing bacterial community were studied in the laboratory. Four different concentrations of NO(inf3)(sup-), 0, 533, 1434, and 2,905 (mu)g of NO(inf3)(sup-)-N g of dry sediment(sup-1), were added to pots containing freshwater sediment, and the pots were then incubated for a period of 69 days. Upon harvest, NH(inf4)(sup+) was not detectable in sediment that received 0 or 533 (mu)g of NO(inf3)(sup-)-N g of dry sediment(sup-1). Nitrate concentrations in these pots ranged from 0 to 8 (mu)g of NO(inf3)(sup-)-N g of dry sediment(sup-1) at harvest. In pots that received 1,434 or 2,905 (mu)g of NO(inf3)(sup-)-N g of dry sediment(sup-1), final concentrations varied between 10 and 48 (mu)g of NH(inf4)(sup+)-N g of dry sediment(sup-1) and between 200 and 1,600 (mu)g of NO(inf3)(sup-)-N g of dry sediment(sup-1), respectively. Higher input levels of NO(inf3)(sup-) resulted in increased numbers of potential nitrate-reducing bacteria and higher potential nitrate-reducing activity in the rhizosphere. In sediment samples from the rhizosphere, the contribution of denitrification to the potential nitrate-reducing capacity varied from 8% under NO(inf3)(sup-)-limiting conditions to 58% when NO(inf3)(sup-) was in ample supply. In bulk sediment with excess NO(inf3)(sup-), this percentage was 44%. The nitrate-reducing community consisted almost entirely of NO(inf2)(sup-)-accumulating or NH(inf4)(sup+)-producing gram-positive species when NO(inf3)(sup-) was not added to the sediment. The addition of NO(inf3)(sup-) resulted in an increase of denitrifying Pseudomonas and Moraxella strains. The factor controlling the composition of the nitrate-reducing community when NO(inf3)(sup-) is limited is the presence of G. maxima. In sediment with excess NO(inf3)(sup-), nitrate availability determines the composition of the nitrate-reducing community.     

Monitoring the denitrification of wastewater containing high concentrations of nitrate with methanol in a sulfur-packed reactor

Biological denitrification of high nitrate-containing wastewater was examined in a sulfur-packed column using a smaller amount of methanol than required stoichiometrically for heterotrophic denitrification. In the absence of methanol, the observed nitrate removal efficiency was only about 40%, and remained at 400 mg NO(3)(-)-N/l, which was due to an alkalinity deficiency of the pH buffer and of CO(2) as a carbon source. Complete denitrification was achieved by adding approximately 1.4 g methanol/g nitrate-nitrogen (NO(3)(-)-N) to a sulfur-packed reactor. As the methanol concentration increased, the overall nitrate removal efficiency increased. As influent methanol concentrations increased from 285 to 570, 855, and 1,140 mg/l, the value of Delta mg alkalinity as CaCO(3) consumed/Delta mg NO(3)(-)-N removed increased from -1.94 to -0.84, 0.24, and 0.96, and Delta mg SO(4)(2-) produced/Delta mg NO(3)(-)-N removed decreased from 4.42 to 3.57, 2.58, and 1.26, respectively. These results imply the co-occurrence of simultaneous autotrophic and heterotrophic denitrification. Sulfur-utilizing autotrophic denitrification in the presence of a small amount of methanol is very effective at decreasing both sulfate production and alkalinity consumption. Most of methanol added was removed completely in the effluent. A small amount of nitrite accumulated in the mixotrophic column, which was less than 20 mg NO(2)(-) -N/l, while under heterotrophic denitrification conditions, nitrite accumulated steadily and increased to 60 mg NO(2)(-) -N/l with increasing column height.     

基于液泡膜质子泵的硝态氮再利用研究进展

全面掌握洛川果园的土壤水分环境特征,不仅可为苹果的园址选择、砧穗组合和改进土壤水分管理措施提供理论依据,而且对我国苹果产区果园提质增效具有借鉴价值.采用定点土壤水分连续监测法,对洛川苹果园的总体土壤水分环境以及不同生长年限、不同立地类型和乔、矮化果园的土壤水分分异特征进行分析.结果表明： 苹果树根际区 (0～200 cm)土壤水分普遍亏欠,且0～60 cm土层的水分亏欠小于60～200 cm土层;生长季0～60 cm土层贮水量与降水量的变化一致,土壤相对含水量大多<60%,季节性旱象严重;果园剖面土壤含水量变异系数随土壤深度加深而递减;随果园生长年限的增大,土壤剖面贮水量下降;在栽培密度一致的条件下,矮化果园5 m土层土壤含水量均高于乔化果园,而栽培密度大的矮化果园的土壤贮水量低于栽培密度小的乔化果园;塬地成龄果园的土壤水分含量最高,川地次之,台地相对较低.密度对果园土壤水分含量有很大影响,在栽培密度一致的条件下,采用矮化栽培能减少土壤水分消耗,显著提高果园土壤含水量;挖株降低栽培密度是维持苹果园土壤水分平衡、实现可持续发展的有效途径.     

元素硫和双氰胺对蔬菜地土壤硝态氮淋失的影响

采用温室盆栽淋洗试验,以NH₄HCO₃为氮肥源,研究了元素硫(S₀)和双氰胺（DCD）对种葱和不种作物土壤NO₃^--N淋失量和NO₃^--N、NH₄⁺-N浓度的影响.结果表明,在12周试验期间,与对照相比,S₀+DCD和S₀处理NO₃^--N淋失量分别低83%～86%和83%;NH₄⁺-N淋失量分别高16.8～21.0 mg·盆^-1和20.4～25.0 mg·盆^-1;而同期无机氮（NO₃^--N、NH₄⁺-N）淋失量则低60%.试验结束后,,S₀+DCD和S₀处理土壤无机氮含量分别比对照高79.9%～85.4%和74.9%～82.6%,以NH₄⁺-N为主.S₀+DCD处理无机氮淋失量比S₀和DCD处理分别低4.6%～14.4%和15.4%～30.1%;试验结束后土壤无机氮分别高6.1%和16.8～36.0%.在Na₂S₂O₃+DCD、Na₂S₂O₃和DCD处理中也发现类似结果.可见S₀施入土壤具有与DCD同样的氨稳定和硝化抑制作用.S₀与DCD配合施用可使DCD的硝化抑制性增强,其作用机理是S₀氧化中间体S₂O₃^2-、S₄O₆^2-,具有抑制硝化和DCD降解作用,延缓DCD硝化抑制效果.S0与DCD配合施用可用于延缓太湖流域蔬菜地土壤NH₄⁺-N向NO₃^--N转化,减少氮向水体迁移风险.