Soluble organic nitrogen in forest soils of northeast China

Soluble organic nitrogen （SON） is recognized as a sensitive indicator of soil nitrogen status. The present work was conducted in the temperate forests of northeast China where soils are typically characterized by high organic matter and high organic nitrogen content, and soil sampling was made in early spring just after the freeze-thaw period. The water extracted SON pools in the organic layer of forest soils were measured within the range from 156.0 mg·kg^-1 to 292.6 mg·kg^-1, a similar magnitude of salt solution extracted SON pools reported in literatures. However, the water soluble SON pools in 0-15 cm mineral soils in present study were much higher （3-10 times） than any other reports, ranging from 58.6 mg·kg^-1 to 125.2 mg·kg^-1. Water soluble SON varied markedly among the soils under different forests and at different sites. The SON in water extracts were positively and significantly correlated to soil organic matter and total nitrogen contents, but negatively correlated to microbial biomass nitrogen （MBN）. The reasons of the abnormally large SON pools and the negative correlations between SON and MBN in the 0-15cm mineral soils in this study were specially discussed.

Biodegradability of soil water soluble organic carbon extracted from seven different soils

Water soluble organic carbon （WSOC） is considered the most mobile and reactive soil carbon source and its characterization is an important issue for soil ecology study. A biodegradability test was set up to study WSOC extracted from 7 soils differently managed. WSOC was extracted from soil with water （soil/water ratio of 1：2, W/V） for 30 min, and then tested for biodegradability by a liquid state respirometric test. Result obtained confirmed the finding that WSOC biodegradability depended on the both land use and management practice. These results suggested the biodegradability test as suitable method to characterize WSOC, and provided useful information to soil fertility.

Effects of Soluble Organic N on Evaluating Soil N-Supplying Capacity

It is important to study the soluble organic N （SON） extracted during water-logged incubation for evaluating soil Nsupplying capacity. Soil initial SON and mineral N （Nmin）, cumulative soluble organic N and NH4＋-N in leachates during water-logged incubation, mineralization potentials of both easily decomposable N （ND） and resistant N （NR）, and their relationships with N uptake by crop in pot experiment were investigated by using 10 kinds of farmland soils with widely different physical and chemical properties on the Loess Plateau, China, and the effects of SON on evaluating soil Nsupplying capacity were studied. The results showed that the average content of initial SON （23.9 mg kg^-1） of 10 soils was 28.8% of initial total soluble N and 2.4% of soil total N. The percentage of cumulative SON in leaching total soluble N （118.1 mg kg^-1 was 46.4%, higher than the percentage of initial SON （28.8%）, and almost close to the percentage of cumulative NH4^＋-N in the leachates. ND had close correlation with total N, and the correlation coefficients were 0.92 （P 〈 0.01, excluding SON in estimating ND） and 0.88 （P 〈 0.01, including SON in estimating ND）, respectively. N mineralization potential and mineralization rate constant were different with the soil types. ND of Los-Orthic Entisols and Ust-Sandiic Entisols were lower than that of Eum-Orthrosols. Mineralization rate constant for the fast decomposable N-fraction （kD） decreased and the mineralization rate constant of resistant materials （kR） increased when SON was taken into account. Cumulative NH4^＋-N was a better evaluation index of soil N-supplying capacity, and it is not only suitable for the first season crops but also for two successive season crops. Cumulative SON alone was not a satisfactory index for the potential of mineralizable N. But it would be more accurate for ND in revealing the potential mineralizable N when SON was taken into account. Cumulative TSN, to some extent, could also be taken as an index for the potential mineralizable N. Cumulative NH4＋-N, total soluble N, and ND were good indexes for estimating soil potential mineralizable N, especially for soils of two successive season crops. And cumulative total soluble N and ND in evaluating the permanence of soil N-supply is of greater significance when SON was included.

Partitioning of water soluble organic carbon in three sediment size fractions:Effect of the humic substances

Water soluble organic carbon （WSOC） in sediments plays an important role in transference and transformation of aquatic pollutants. This article investigated the inherent mechanisms of how sediemnt grain size affect the partitioning coeffcient （k） of WSOC. Influences of NaOH extracted humic substances were particularly focused on. Sediments were sampled from two cross-sections of the middle Yellow River and sieved into three size fractions （〈 63 μm, 63-100 μm, and 100-300 μm）. The total concentration of WSOC in sediments （Cwsoc） and k were estimated using multiple water-sediment ratio experiments. Results showed that Cwsoc ranged from 0.012 to 0.022 mg/g, while k ranged from 0.8 to 3.9 L/kg. Correlations between the spectrum characteristics of NaOH extracted humic substances and k were analyzed. Strong positive correlations are determined between k and the aromaticity indicators of NaOH extracted humic substances in different sediment size fractions. Comparing with finer fractions （〈 63 μm）, k is higher in larger size fractions （63- 100 μm and 100-300 μm） related to higher aromaticity degree of NaOH extracted humic substances mostly. While negative relationship between k and the area ratio of fourier transform infrared spectroscopy （FT-IR） at 3400 and 1430 cm^-1 implied that the lowest k was related to the highest concentration of acidic humic groups in particles 〈 63 μm. WSOC in finer fractions （〈 63 μm） is likely to enter into pore water, which may further accelerate the transportation of aquatic contaminants from sediment to water.

STUDY ON THE MUTUAL SOLUBILITY OF WATER GLASS AND WATER SOLUBLE ORGANIC BINDER

The careful studies have been made into the mutual solubility of water glass and water soluble organic binder in this paper, By means of many experiments, it has been found that water soluble polymer is able to be evenly soluble in water glass, and certain valuable conclusions have been concluded.

Fluorescence characteristics of water soluble organic carbon in eastern China

Fluorescence excitation and average molecular weight of 46 water soluble organic matter (WSOC) samples extracted from 20 soil types in eastern China were determined. It was found all samples shared similar spectroscopy. A good linear relationship existed between total organic carbon and excitation in the range of 350 to 450 nm though the content of organic carbon and pH of the samples vary in a wide range. No significant correlation between relative excitation intensity and average molecular weight of WSOC and FA was found, but the partial correlation became significant with pH as the controlling factor for WSOC samples. The relative excitation intensity showed a general trend of increasing from south to north in the study area. The pH value might play an important role in regulating the fluorescent spatial variation of WSOC. S153 A

Organic Manures Improved the Phenolic Content, Antioxidant Capacity and Soluble Solids in Pepper

The aim of this research was to determine the effect of three organic manures (vermicompost, simple compost, compost with gypsum) with four different levels, as sources of fertilization, and mixed with river sand, this was used as an inert material, on the phenolic content, antioxidant capacity and total soluble solids of bell peppers (Capsicum annuum L.). The 12 mixtures formulated, with eight replications, were distributed in a completely randomized design. Data were statistically analyzed by analysis of variance and means were compared by test Tukey5%. All variables were significantly affected (p ≤ 0.001). Fruits with highest phenolic content were developed in the mixtures M2, M5 and M6 with 538.76, 541.54 and 565.04 mg GAE·100 kg-1 DW, respectively. Antioxidant capacity of fruits was increased with mixtures M2, M5, M6 and M7 with values of 934.48, 942.04, 921.69 and 924.17 μM TEAC·g-1 DW, respectively. The soluble solids content was higher in mixtures M1 and M2 with values of 4.93 and 4.97 °Brix, respectively. It was concluded that the variables studied were favored when applying, as sources of fertilization, mixtures of these organic manures with river sand, which could represent a suitable alternative for food production with quality nutraceutical.

Research progress of soluble CD83 in organ transplantation

Organ transplantation is considered to be an effective method for the treatment of end-stage organ failure,early malignant tumors and tissue damage.In order to reduce the rejection of the transplanted organ by the host,immunosuppressive drugs should be used for a long time,but the suppression of the host immune system by immunosuppressive drugs can cause serious side effects.Therefore,how to induce the recipient's immune system to have no response to the transplanted organ after transplantation,while still showing a normal immune response to the alien antigen.Induction of immune tolerance to donor organs has long been a focus of research by transplant scientists.Soluble CD83(sCD83)is a glycoprotein with specific immunosuppressive effects.In recent years,there have been more and more reports on the immune tolerance induced by sCD83 in animal experiments,which has shown a broad prospect in the treatment of host immune rejection after organ transplantation and provided an experimental basis for its clinical transformation.

Solubility study and selective purification of HMX explosive in organic electrolyte solution of zinc acetate/diethylene glycol

In this study, an organic electrolyte solution based on zinc acetate/diethylene glycol(ZA/DEG) is introduced for the selective purification of cyclotetramethylene tetranitramine(HMX) high explosive from its identical homologue cyclotrimethylene trinitramine(RDX). The dielectric constant of various organic solutions were investigated through Electrochemical Impedance Spectroscopy(EIS) in the range of 1.0 Hz—30 MHz. and some quantum-chemical descriptors of RDX and HMX dissolutions in the ZA cosolvent were analyzed using Density Functional Theory(DFT). The results show dielectric constant and solubility of RDX is higher than that of HMX, and by increasing of ZA concentration in DEG solvent, the values of dielectric constants were enhanced. Furthermore, the presence of ZA cosolvent on the solubility of two explosives was statistically investigated by Central Composite Design(CCD) of experiment, and some solubility parameters including activity coefficient, dissolving enthalpy, and mixing enthalpies were determined. The experimental results indicate that the weight ratio of RDX to HMX solubility in the proposed organic electrolyte changes up to 30 times, which provides a selective and sequential separation method to separate two materials with similar chemical properties with a separation efficiency>98% and HMX purity> 99.8%. The X-Ray Diffraction(XRD) analysis, High-Performance Liquid Chromatography(HPLC), Laser-Induced Breakdown Spectroscopy(LIBS), and Fourier Transform Infrared Spectroscopy(FT-IR) approves the acceptable quality of the separated materials. The proposed method makes the efficient and safe purification of high-quality HMX for application in oil and gas well perforating gun charges, using a nonvolatile and inflammable organic electrolyte.

东北半干旱黑土区玉米秸秆还田方式对土壤水溶性有机碳含量及其组分的影响

为明确不同秸秆还田方式下土壤有机碳组分的变化特征,基于6 a秸秆还田长期定位试验,利用三维荧光光谱技术,对无秸秆还田(CK)、秸秆覆盖还田(FG)、秸秆翻埋还田(FM)处理下土壤有机碳(SOC)含量及水溶性有机碳(WSOC)含量及其结构特征进行分析。结果表明:(1)与CK相比,FM处理0~40 cm土层SOC含量提高7.87%~29.54%,FG处理0~30 cm土层SOC含量增加1.91%~18.61%,30~40 cm土层SOC含量降低7.67%;FM和FG处理0~40 cm土层土壤WSOC含量分别提升13.42%~39.42%和0.28%~26.34%。(2)通过WSOC三维荧光光谱发现,各土层CK(Ex/Em=300/34、Ex/Em=300/340、Ex/Em=240/340、Ex/Em=300/340)处理WSOC荧光特征峰为溶解性微生物代谢产物和类色氨酸蛋白质物质荧光峰;FM(Ex/Em=340/430、Ex/Em=340/430、Ex/Em=340/435、Ex/Em=340/435)和FG(Ex/Em=270/440、Ex/Em=270/435、Ex/Em=340/435、Ex/Em=340/430)处理为类腐殖酸类物质荧光特征峰,腐殖化程度较高,结构较为复杂;荧光区域积分表明,FM和FG处理类腐殖酸类物质(Ⅴ)和富里酸类物质(Ⅲ)的积分百分比分别较CK增加12.18%~27.39%、11.98%~30.72%和3.96%~5.73%、2.99%~5.40%。(3)土壤WSOC包含两个组分,C1(Ex/Em=340/435,270/435)组分为类腐殖酸类物质,C2(Ex/Em=290/345,240/345)组分为溶解性微生物代谢产物和类色氨酸蛋白质物质;F max值结果表明,0~40 cm土层的C1组分相对含量表现为FM>FG>CK,表明秸秆翻埋还田更有助于土壤中营养物质含量增加和形成更高分子量的有机物。综上,不同秸秆还田方式均可提升SOC和土壤WSOC含量,增加腐殖化程度,加强土壤的供肥能力,翻埋还田处理提升作用更为显著。

鄱阳湖湿地溶解性有机质的光化学属性对水体光活性中间体(PPRIs)季节性变化的影响

湿地的水文和水化学在时空尺度上会呈现显著差异,进而会引发光化学反应的变化,光活性中间体(PPRIs)是水体间接光反应的产物,具有极强的氧化性,对水环境中有机物和污染物的归驱具有重要的影响,因此迫切需要探究湿地中PPRIs的产生过程。本研究通过捕获剂法监测了鄱阳湖湿地4个季节水体中3种PPRIs(^(1)O_(2)、·OH及^(3)CDOM^(*))的产生速率和稳态浓度的变化,并通过紫外吸收光谱、三维荧光光谱、以及傅立叶变换离子回旋共振质谱等技术对水体中可溶性有机质(DOM)组分的化学特征进行分析,揭示了鄱阳湖湿地不同季节水体中的DOM的光化学反应特性及与PPRIs产生的相关性。结果发现:鄱阳湖夏季和秋季水体的pH值、溶解有机碳(DOC)浓度较高,相反,硝酸盐、亚硝酸盐浓度在夏季和秋季较低。夏季和秋季的DOM中芳香族化合物丰度较高,并且木质素丰度明显高于冬季和春季。不同季节鄱阳湖水体有色可溶性有机物产生能力依次为秋季>夏季>冬季>春季。夏季和秋季水体中^(1)O_(2)和·OH产生速率和稳态浓度显著高于春季和冬季水体。pH、DOC、E2/E3、脂类、蛋白类及木质素类与PPRIs产生速率展现出了良好的正相关关系,尤其是其中的DOC与木质素类组分;另外在三维荧光指标结果中,荧光指数(FI)和新鲜度指数(β/α)与PPRIs呈现负相关关系,证明FI值越低即DOM陆源性越高、非新生DOM比例越高,则PPRIs产生速率越高。综上,PPRIs的光化学产生与植物源DOM密切相关。与春季和冬季相比,夏季和秋季鄱阳湖水体的有机质高,而其中DOM组分中芳香族化合物丰度较高,主要来自陆生植物和土壤有机质,其有机质的腐殖化水平较高,而在春季和冬季水体有机质主要来自湖泊本身和微生物产生的有机质,属于内源。淹水植物残体降解过程释放的有机组分,对夏、秋季DOM的来源和组成有着极易被忽视的影响和作用,而其中光化学活性较强的有机组分如木质素是造成其PPRIs产率更高的主要原因。

半干旱地区秸秆还田对土壤有机碳组分及产量的影响

为了探索半干旱区玉米秸秆还田对土壤有机碳组分和产量的影响,以黑龙江省农业科学院齐齐哈尔分院秸秆长期定位试验田为研究对象,对CK(常规种植)、FM(秸秆翻埋还田)和FG(秸秆覆盖还田)3种处理下土壤颗粒有机碳、水溶性有机碳含量及玉米产量进行分析。结果表明:不同处理各土层均是黏粒(<0.053μm)有机碳含量最高。FM处理4个土层砂粒(>0.250μm)和黏粒(<0.053μm)有机碳含量平均值分别提高了21.78%和20.51%,FG处理分别提高了25.87%和13.52%。FM处理在各土层水溶性有机碳含量最高,在0~10和>10~20 cm土层中顺序为FM>FG>CK,其中FM处理分别较CK增加22.73%和38.25%,FG处理分别较CK提高2.48%和26.32%。在>20~30和>30~40 cm土层中,土壤水溶性有机碳含量依次为FM>CK>FG,其中FG降低幅度分别为14.55%和9.41%,而FM处理增加幅度分别为10.68%和17.85%。不同处理之间穗长、穗粗和穗行数差异不明显。穗粒数顺序为FM>FG>CK,籽粒含水量顺序为FG>CK>FM;产量顺序为FM>FG>CK,FM和FG处理分别较CK增产5.20%和3.20%。

新疆难解吸煤可溶有机质对瓦斯吸附解吸特征的影响研究

新疆焦煤公司煤层瓦斯难解吸,导致抽采难度增大。而煤中可溶有机质对瓦斯的吸附解吸有重要影响。为了研究其影响,使用四氢呋喃对煤中的可溶有机质进行抽提,采用低温氮吸附测试抽提前后煤的孔隙结构,利用煤岩高压瓦斯吸附装置进行抽提前后煤样的吸附解吸实验。研究结果表明:经过四氢呋喃抽提后,发现所有煤样的平均孔径、孔体积和比表面积均有不同程度的增大,认为煤中的可溶有机质被溶解,形成了新的微孔,同时原孔隙被扩大;4^(#)煤、5^(#)煤和6^(#)煤的吸附常数a分别减小了2.73%、16.09%、14.57%,4^(#)煤和5^(#)煤吸附常数b分别增大了12.18%、2.58%,6^(#)煤的吸附常数b减小了8.59%,煤的吸附能力降低,解吸速度增大,可溶有机质促进了煤对瓦斯的吸附。

西安PM_(2.5)碳组成及水溶性有机物分子特性和来源季节差异

利用平行因子分析和后向轨迹模型,采用紫外光谱法、三维荧光光谱法,分析西安市PM_(2.5)碳组成及水溶性有机物(Water-Soluble Organic Matters,WSOM)的荧光组分、分子特性和来源。结果显示,西安市各季节PM_(2.5)及其有机碳(Organic Carbon,OC)和元素碳(Elemental Carbon,EC)的质量浓度由高到低依次为:冬、秋、春、夏,且南北郊差异不显著。PM_(2.5)中水溶性有机碳(Water-Soluble Organic Carbon,WSOC)质量浓度为3.50~17.29μg/m^(3),冬季WSOC质量浓度最高。四季的WSOM中均含有紫外光类腐殖质和可见光类腐殖质。秋、冬和夏季类富里酸的荧光强度占比最大。WSOM的E_(2)/E_(3)、E_(3)/E_(4)和AAE值由高到低依次是:冬、春、夏、秋。SUVA 254和MAE_(3)65值均在冬季最高,夏季最低。冬季WSOM的相对分子质量和腐殖化程度较小,分子苯环取代程度最大,光吸收能力对光吸收的波长依赖性较强;秋季WSOM的相对分子质量较大,腐殖化程度较强,光吸收的波长依赖性较弱;夏季WSOM的芳香化程度和光吸收能力及春季WSOM分子苯环取代程度最弱。碳组分质量浓度、UV 254、α350和荧光强度两两呈显著正相关(p<0.01)。WSOM的荧光指数(Fluorescence Index,FI)、生物源指数(Biogenic Index,BIX)和腐殖化指数(Humification Index,HIX)值分别为1.51~2.15、0.88~1.46、1.18~3.19。冬季WSOM的自生来源最高,夏季WSOM的陆源来源比例相对较大。西安市污染气团主要来自于陕西省区域气团传输。西安市四季PM_(2.5)碳组成及WSOM的荧光组分、分子特性和来源存在季节差异,但北郊和南郊的紫外荧光光谱特性和来源差异不显著。

加强油源岩沉积成岩成油模拟实验研究

干酪根热降解生油学说源于油页岩高温热解生成“人造石油”的生产实践,其理论内涵是凡富含干酪根的岩石,经高温热解后其所含的干酪根都可以生成“人造石油”。应用该学说的高温热解实验方法,可以评价油页岩的品质及其热解生成“人造石油”的潜力,因此仅适用于油页岩的评价研究。但该学说的倡导者却认为油页岩和油源岩都是能生成石油的岩石,如果埋藏较浅时就称为油页岩,如果埋藏较深时就是油源岩,因此干酪根热降解生油学说同样适用于油源岩。这种观点并没有被美欧等国家所认可,但遗憾的是,在改革开放之初不甚了解国外同行对该学说如何评价的情况下,中国的石油地质家不仅全盘接受了该学说,而且推广应用了40多年。为彻底改变这种被动局面,唯一可行的就是通过油源岩沉积成岩成油模拟实验,研究油源岩中可溶有机质的生油问题和评价方法。

化肥减量配施鱼蛋白有机液肥对番茄产量和品质的影响

为探讨增施鱼蛋白有机液肥替代化肥的效果,以每667m^(2)施用高钾水溶肥5.0kg为对照,设置每667 m^(2)施用高钾水溶肥3.5 kg+鱼蛋白有机液肥5.0 L、高钾水溶肥2.0 kg+鱼蛋白有机液肥5.0 L、高钾水溶肥0.5kg+鱼蛋白有机液肥5.0L这3个化肥减量处理,比较分析化肥减量增施鱼蛋白有机液肥对番茄生长、产量和果实性状及可溶性固形物含量的影响。结果表明:在每667m^(2)施用5.0L鱼蛋白有机液肥的情况下,减少水溶肥用量会降低番茄的株高、叶长和叶宽,但促进了茎粗、果实纵横径的生长,其中不同处理的果实纵径差异不显著,果形指数和可溶性固形物含量随水溶肥用量的减少先升高再降低,以每667 m^(2)每次追施高钾水溶肥3.5 kg和2.0 kg的果形指数最大,但与其他处理没有显著差异。不同处理的平均单穗坐果数没有显著差异,单果质量和果实纵横径的变化趋势一致,每667 m^(2)每次追施高钾水溶肥0.5 kg的小区产量最大。因此,在追求产量的情况下,果实膨大至采收前以每667 m^(2)每次追施高钾水溶肥+0.5 kg鱼蛋白有机液肥5.0 L的肥料配比最适合生产;如果追求品质,每667 m^(2)每次追施高钾水溶肥2.0 kg+鱼蛋白有机液肥5.0 L的肥料配比有利于生产,比对照果实可溶性固形物含量可提高5.8%,667 m^(2)产量提高17.2%。

深松与秸秆覆盖还田对半干旱区土壤碳组分和玉米产量的影响

为促进黑龙江省西部半干旱区土壤固碳和玉米增产,以黑龙江省农业科学院耕作与秸秆长期定位试验田为研究对象,以CK(常规种植)、NFG(秸秆覆盖还田)、SFG(深松+秸秆覆盖还田)3种处理对土壤有机碳、不同粒径有机碳、水溶性有机碳含量及玉米产量的影响进行分析,研究深松与秸秆覆盖还田对半干旱区土壤碳组分和玉米产量的影响。结果表明,(1)本试验中,在0~10 cm和10~20 cm土层的土壤有机碳和水溶性有机碳含量顺序均为SFG>NFG>CK。(2)<0.053 mm粒级团聚体有机碳含量明显高于>0.250 mm和0.053~0.250 mm粒级,在0~10 cm土层,SFG、NFG处理土层>0.250 mm、<0.053 mm和0.053~0.250 mm粒级团聚体有机碳含量均比对照CK提高10%以上。(3)在10~20 cm土层,SFG处理>0.250 mm粒级和NFG处理0.053~0.250 mm粒级团聚体有机碳含量增加较为明显。(4)不同处理之间玉米穗长、穗粗和穗行数差异不显著,穗粒数和产量差异达到显著水平,其中SFG和NFG处理分别较CK产量提高了28.57%和15.10%。产量与土壤有机碳含量之间呈极显著正相关关系,与团聚体有机碳和水溶性有机碳含量呈显著正相关关系。

甜樱桃果实品质研究进展

为提高甜樱桃果实品质,阐述了甜樱桃果实在发育成熟过程中外观品质(果实大小、果皮颜色)和内在品质(糖酸、激素和质地)的性状变化,分析了影响果实品质形成的遗传因素(品种、砧木)和环境因素(光照、温度、水分、养分),总结了提高甜樱桃果实品质的栽培管理研究进展,对提高甜樱桃果实品质的研究方向进行了展望。

第十四届全运会大气污染物减排措施对西安市气溶胶中水溶性离子和含碳组分的影响

人为源密集的城市是空气污染影响的主要区域,厘清城市地区排放源的变化与大气污染物浓度之间的影响作用机制,有助于协调我国大气污染防控与城市社会经济发展之间的关系。为研究第十四届全运会期间大气污染物减排措施对西安市大气污染物(PM_(2.5)、PM_(10)、SO_(2)、NO_(2)、O_(3)和CO)的影响,于2021年8月6日至10月1日使用在线监测仪器观测了环境六要素、气象要素和PM_(2.5)中的气溶胶化学组分(有机碳、元素碳和水溶性离子)。结果表明:大气污染物减排措施对主要污染物O_(3)和PM_(2.5)浓度日变化的影响不同,主要由温度对光化学过程的影响和扩散条件差异导致。O_(3)在减排措施实施期间晴天峰值浓度更高、持续时间更长、浓度变化更迅速。PM_(2.5)在减排措施实施前晴天白天的峰值浓度较高,并在减排措施实施期间晴天夜间的峰值浓度较高。大气污染物减排措施对PM_(2.5)中化学组分的影响不同,尤其是对有机碳的组成影响较大。与减排措施实施前晴天相比,减排措施实施期间晴天NO_(3)^(-)、SO_(4)^(2-)、NH_(4)^(+)、Cl^(-)、Ca^(2+)、Na^(+)和NO_(2)^(-)浓度降低了17.9%~71.8%,K^(+)、Mg^(2+)和元素碳浓度增加了1.9%~13.6%,有机碳浓度仅降低了1.0%,但是一次有机碳浓度增加了13.6%,二次有机碳浓度降低了4.7%。NO_(3)^(-)/SO_(4)^(2-)值在减排措施实施期间晴天(0.53)远低于减排措施实施前晴天(1.66),表明减排措施实施期间交通源的贡献显著降低。降雨对NO_(3)^(-)和NH_(4)^(+)的清除较弱,反而会增加其浓度,但对K^(+)、Mg^(2+)、Ca^(2+)和Na+的清除作用较强。NO_(3)^(-)、SO_(4)^(2-)和NH_(4)^(+)在减排措施实施前后均是水溶性离子最重要的组成,在水溶性离子中的占比为90.8%(减排措施实施前的晴天)~95.8%(减排措施实施期间的雨天)。二次有机碳是有机碳的主要组成,占比为75.5%(减排措施实施期间的雨天)~79.9%(减排措施实施前的晴天)。不同阶段的水溶性离子和含碳气溶胶浓度日变化特征不同。NO_(3)^(-)、SO_(4)^(2-)和NH_(4)^(+)浓度晴天的日变化为单峰型分布,雨天为多峰型分布。

不同施肥方法对香蕉园土壤条件和香蕉产量及品质的影响

为了探究不同施肥方式对香蕉园土壤环境条件、香蕉产量及果实品质的影响差异,筛选香蕉园较佳的施肥方式,为香蕉园合理施肥提供参考。以当地常规施肥(仅施化肥)为对照,设置增施生物有机肥、复合微生物肥和鸽子粪肥等处理,在广州市增城区永宁街道永和简村开展为期2年的香蕉大田试验,分析比较不同施肥方式对香蕉园土壤养分含量、酶活性、微生物群落结构,及香蕉产量和果实品质的影响。结果表明,与对照相比,增施生物有机肥、复合微生物肥和鸽子粪肥处理均显著增加香蕉园土壤有机质含量,以增施生物有机肥处理效果最为明显,分别较对照和增施鸽子粪肥处理增加46.51%和18.23%,处理间差异显著;增施生物有机肥处理的有效磷、总氮、碱解氮含量及pH值也最高。土壤酶活性方面,3个增施肥处理均增加α-葡萄糖苷酶、中性磷酸酶、酸性磷酸酶和硝酸还原酶活性,3个处理间差异不显著,增施生物有机肥处理的多酚氧化酶显著降低,而纤维素酶则显著增加。增施复合微生物肥处理改变土壤细菌群落结构,增加变形菌门(Proteobacteria)丰度,而增施生物有机肥处理则提升细菌群落丰度。3个增施肥处理均显著增加香蕉产量和产值,提高果实可溶性糖和维生素C含量,降低硝酸盐和亚硝酸盐含量,以增施生物有机肥处理效果最为明显,较对照产量增加754 kg/667 m^(2),纯收益增加1248元/667 m^(2),施肥产投比达到5.8∶1。说明香蕉园增施生物有机肥、复合微生物肥和鸽子粪肥均可增加土壤有机质含量,提高土壤酶活性,改变土壤微生物菌落结构及丰度,并显著提高香蕉产量,改善果实品质,以增施生物有机肥效果最佳。