INTRODUCTION

The application of organic and inorganic amendments has been recognized as a possible method for improving soil physicochemical properties and fertility(Waltz et al.,2003;Lima et al.,2009;Colombani et al.,2014).Among them,natural zeolite-bearing rocks are known to be a suitable material for agricultural purposes owing to their very high cation exchange capacity(CEC),reversible dehydration,and molecular sieving properties(Reh´akov´a et al.,2004;Passaglia,2008;Misaelides,2011).Zeolites are aluminosilicates with an open three-dimensional framework,which delimits channels and cavities where different kinds of polar and non-polar molecules can be exchanged,involving both inorganic and organic compounds,with a particular affinity to NH+4(Reh´akov´a et al.,2004).Furthermore,zeolites can be easily modified from their natural state by enrichment processes,which cause the adsorption of specific cations,e.g.,NH+4and Na+(Dittert et al.,1998;Leggo,2000;Faccini et al.,2015).

八、外币兑换。出境前可携带本人身份证前往就近的、可以经营外汇业务的银行办理相关换汇事宜。具体换汇信息及营业网点，请以银行工作人员或银行查询热线告知的信息为准。

Since natural chabazite(CHA)zeolites are less abundant than clinoptilolites worldwide(Passaglia,2008),the latter have been investigated in the majority of agricultural and environmental studies.Chabazite zeolites are commonly found in volcanoclastic deposits,especially in the Italian Peninsula,where many quarries are exploiting zeolite-rich tuffs for the production of construction bricks(Passaglia,2008).These tuffs are generally dominated by potassium(K)-rich CHA,and thus can be classified as zeolitites(ZT)with a high zeolite content(＞50%)(Galli and Passaglia,2011).During the cutting process of these construction bricks,a high amount of zeolite-rich material remains unused,constituting a waste for the quarry.However,it is an interesting and precious granular by-product,which can be used for many purposes,including the use as a soil amendment as demonstrated by the ZeoLIFE project,European Union(LIFE10 ENV/IT/000321)(Ferretti et al.,2017a).

The use of different kinds of natural and enriched ZTs as a soil amendment has been studied extensively in terms of modification of the soil physicochemical characteristics(Passaglia,2008;Colombani et al.,2015,2016),reduced N leaching,increased N use efficiency,increased water use efficiency,and improved crop yield(Reh´akov´a et al.,2004;Sepaskhah and Barzegar,2010;De Campos Bernardi et al.,2013;Gholamhoseini et al.,2013;Li et al.,2013;Di Giuseppe et al.,2016).Some studies have defined NH+4-enriched ZT as a slow-release fertilizer,where NH+4is released slowly over time and becomes available for plant uptake,thus reducing potential N losses(Barbarick and Pirela,1984;Lewis et al.,1984;Dwairi,1998).Except for a few studies such as M¨uhlbachov´a andˇSimon(2003),the effects of ZT amendments on the soil microbial biomass(MB)are mostly unexplored.Concerning amendments with NH+4-enriched ZT,Leggo(2000)carried out an investigation of plant growth in an organo-zeolitic substrate and observed an increase in NO−3after the use of natural clinoptilolite enriched by composting with poultry manure.He concluded that the Ca2+present in the soil solution has probably been exchanged with the NH+4adsorbed by the zeolites,making it immediately available to nitrifier microorganisms.However,this outcome is contradictory to the view of NH+4-enriched ZT as a slow-release fertilizer.To the best of our knowledge,no studies exists on the effects of natural and NH+4-enriched CHA-rich ZT(CHAZT)amendments on soil MB.

VP是“A到VP”格式中重要的组成部分，我们需要分析它在“A到VP”格式中起到的作用以及它和“A”“到”之间的关系，因此我们将分别从“A到VP”格式中VP的结构分析和VP的语义分析两方面来看VP的特征。

The present study aimed to investigate the effects of different typologies of CHAZT amendments on soil MB and C-N dynamics over a short-term period.To this end,this study was designed to simulate the conditions occurring in the ZeoLIFE experimental field(Zeo-LIFE project),an ongoing field-scale experimentation,in which natural and NH+4-enriched CHAZTs are being tested at the field scale(Ferretti et al.,2017a).We hypothesized that∶i)amendments with CHAZT at natural state will reduce N availability to soil MB in athan bacteria due to the lower nutrient requirement of fungi(McGill et al.,1981;Strickland and Rousk,2010)and ii)NH+4-enriched CHAZT,acting as a slow-release fertilizer once added to soil,will not affect soil MB in the short-term period.

MATERIALS AND METHODS

Soil sampling

Soil samples were collected during spring 2015 from the ZeoLIFE project experimental field,consisting of a 6-ha agricultural field where different CHAZT amendments are being tested since 2012.The field is located in the Po River Delta Plain near Codigoro Town in Ferrara Province,Italy(44°50′33′′N,12°05′40′′E),and lays on clayey-silty soil of alluvial origin classified as Calcaric Gleyic Cambisol(Di Giuseppe et al.,2014;IUSS Working Group WRB,2014).The experimental field has been subdivided into different plots(0.5–1.5 ha)in which both natural and NH+4-enriched CHAZTs have been applied in various amounts(5–15 kg m−2).Soil samples for this study were collected from an unamended parcel from the top 0.3-m depth layer and amended with different types of CHAZTs in the laboratory immediately before the beginning of the experiment in order to reproduce the short-term effects of zeolite application.Approximately 5 kg soil was brought to the laboratory immediately after sampling,sieved to＜5 mm and air-dried.Main soil characteristics are given in Table I,and soil mineralogical composition has been reported in Malferrari et al.(2013).The soil is mainly characterized by quartz,illite,chlorite,K-feldspar,plagioclase,calcite and amorphous residues,thus lacking of clay minerals with very high CEC(e.g.,smectite).

Soil NO−3-N content ranged from 24.2(in 15NZ)to 301(in 10CZ)mg kg−1(Table III).It is noteworthy that NO−3-N content in 10CZ was entirely out of scale if compared with the other treatments throughout the incubation period.Furthermore,just after 2 d of incubation,10CZ exhibited a very high NO−3-N content(151 mg kg−1),approximately five times higher than that of the other treatments(P＜0.05).The content of NO−3-N in 10CZ increased significantly from days 9 to 16,doubling its initial value.

Zoo-technical effluents commonly used as organic fertilizers,such as pig slurry,are generally strongly enriched in the heavier15N isotope due to NH3volatilization that causes depletion of the lighter14N.The N isotope ratio is expressed in the standard(δ)notation in per mil(‰relative to the atmospheric air(AIR)isotope standard)(Gon fiantini et al.,1995).The abovementioned process results in δ15N values generally ＞10‰ or even＞ 20‰ in pig slurries(Table II)(Dittert et al.,1998;Schmidt and Ostle,1999;Lim et al.,2007),implying that in some cases they can be employed as an isotopic tracer for studies on natural N abundance(Dittert et al.,1998).The main properties of the NZ and CZ used in this study are presented in Table II.

TABLE I Basic properties of the soil used in this study

a)EC=electrical conductivity;CEC=cation exchange capacity;TN=total N;TOC=total organic C.b)Means±standard deviations(n=3).

Propertya)Value 7.6±0.2b)EC(mS cm−1) 1.0± 0.1 CaCO3(g kg−1) 64.5± 3.5 CEC(mmol kg−1) 325± 1 TN(g kg−1) 2.33± 0.31 TOC(g kg−1) 22.76± 3.20 TOC/TN ratio 9.76±0.34 Bulk density(kg m−3) 1247± 81 pH

Natural and NH+4-enriched CHAZTs used

“与人民群众的血肉联系是党的事业兴旺发达的牢固根基”[2]， “伟大的长征精神，就是紧紧依靠人民群众，同人民群众生死相依、患难与共、艰苦奋斗的精神。”[3]47

The quarried material is a zeolitized tuff(a weathered rock of volcanic origin)composed of more than 68%of K-rich CHA,1.8%of phillipsite,and 0.6%of analcime,resulting in a total zeolitic content of 70.9%(Malferrari et al.,2013).The CEC of the whole rock was 1 420 mmol kg−1according to Malferrari et al.(2013).Chabazite-rich zeolitites with a grain size of 3–5 mm were selected and used both at natural state(NZ)and after NH+4pre-enrichment as soil amendments.After sieving,a part of the NZ was subjected to an enrichment process,which allowed the enrichment of the CHA contained in the ZT with NH+4,thus creating an NH+4-enriched CHAZT(CZ).The enrichment process involved mixing of pig slurry and CHAZT in a specifically conceived prototype(Faccini et al.,2015)and produced the CZ with an average NH+4-N load of 3.014 g kg−1.

石羊河流域高效节水灌溉与农业种植结构调整…………………………………………… 李元红，王以兵(5.52)

TABLE II Main properties of the natural(NZ)and NH+4-enriched(CZ)chabazite-rich zeolitites used in this study

a)GWC=gravimetric water content;TN=total N;TOC=total organic C;TDN=total dissolved N;DOC=dissolved organic C;MBC and MBN=microbial biomass C and N,respectively. b)Below the detection limit.

Propertya) NZ CZ Grain size(mm) 3–5 3–5 Air-dry GWC(%) 14.2 21.8 TN(g kg−1) 0.01 4.27 TOC(g kg−1) 0.08 1.24 δ15N(‰) –b) 43.6 TDN(mg kg−1) 14.6 3611 DOC(mg kg−1) – 118 TOC/TN ratio 8.42 0.29 pH 7.58 6.95 MBC(mg kg−1) 22.2 23.8 MBN(mg kg−1) 9.69 388 NO−3-N(mg kg−1) – 146 NH+4-N(mg kg−1) – 3014 Ergosterol(mg kg−1) – –

Experimental setup

This study was conducted in the laboratory in order to mimic the treatments and conditions of the ZeoLIFE experimental field immediately after the application of NZ and CZ,with four different treatments in triplicates.Two treatments were composed of a mixture of soil and NZ in the NZ weight proportion of 5%(5NZ)and 15%(15NZ),respectively.The 3rd treatment were composed of a mixture of soil and CZ in the CZ weight proportion of 10%(10CZ),and the 4th treatment without any amendment served as a control(CNTR).For each treatment,1 kg of 5-mm sieved material was incubated in open ceramic jars(200-mm diameter)for 16 d at room temperature(ca.20°C)with the moisture level adjusted to 45%water- filled pore space(WFPS)with Milli-Q water(Millipore,USA).These conditions reflected the ZeoLIFE field average temperature and moisture level,based on a 4-year(2011–2015)monitoring record.As the present study aimed to verify the immediate effects after the amendments with NZ and CZ,no further N inputs were applied into CNTR,5NZ,and 15NZ.On days 2,7,9,11,and 16 of the incubation period,representative soil samples were collected to analyze a set of parameters mentioned below.

Soil and CHAZT analyses

Inorganic N forms. NH+4-N was extracted with 1 mol L−1KCl at a 1∶10(weight/volume)ratio.The solution was shaken for 1 h, filtered with Whatman no.40 filter paper,and then diluted and analyzed with an O-rion 95-12 ion selective electrode(ISE)connected to an Orion 4star pH/ISE benchtop meter(Thermo Scientific,USA)according to the method modified by Banwart et al.(1972)(Ferretti et al.,2017b).The NO−3-N and NO−2-N were extracted with Milli-Q water(Millipore,USA)at a 1∶10(weight/volume)ratio.The solution was shaken for 1 h and then filtered with Whatman no.40 filter paper(Myers and Paul,1968).Contents of NO−3-N and NO−2-N were determined by ion chromatography(Ferretti et al.,2017b)as indicated by the Italian law according to D.M.13/09/1999 with an isocratic dual pump ICS-1000 Dionex(Thermo Fisher Scientific,USA)equipped with an AS9-HC 4 mm×250 mm high-capacity column and an ASRS-Ultra 4-mm self-suppressor.An AS-40 Dionex auto-sampler was used to run the analysis.A quality control(QC)sample was run every 10 samples.The standard devia-tion of all the QC samples run was less than 4%.Dissolved inorganic N(DIN)was calculated as the sum of NH+4-N,NO−3-N,and NO−2-N.

However,the increase in ergosterol content was not observed in 15NZ despite a very high NZ application rate.Following the previous hypothesis,the higher the NZ in the soil,the higher the fungal development because of the lower available mineral N for microbes.A possible explanation for this behavior may reside in the relative DOC availability in these two treatments(5NZ and 15NZ).The higher DOC content in 5NZ might have favored fungal biomass development,while the relatively lower DOC at the beginning of the incubation in 15NZ might have prevented the development of fungal biomass.This indicates that the amount of NZ added to the soil in fluenced nutrient availability in the short term,with varying effects on fungal biomass.The findings of the present study support the first hypothesis for 5NZ,but not for 15NZ.

pH,dissolved C and N,and microbial biomass C(MBC)and N(MBN). Soil pH was determined using 0.01 mol L−1CaCl2extract at a 1∶10(weight/volume)ratio with a lab pH meter inoLab®pH 196 Level 2(WTW,Germany).Chloroform fumigation-extraction method was employed according to Brandst¨atter et al.(2013)and¨Ohlinger(1996)to determine MBC,MBN,dissolved organic C(DOC),and total dissolved N(TDN).Fumigated and nonfumigated samples were prepared with 1 mol L−1KCl at a 1∶10(weight/volume)ratio.The suspension was shaken for 1 h and then filtered through an N-free filter paper.Filtrates were stored at−20°C prior to analysis with a TOC-L TNM-L Shimadzu Analyzer(Shimadzu,Japan)equipped with an ASI-L auto sampler.Before the analysis,inorganic C was eliminated by acidi fication.The C and N extracted from non-fumigated sample represented DOC and TDN,respectively.The C and N extracted from chloroform-fumigated samples minus those extracted from non-fumigated samples represented the C and N immobilized by soil microorganisms,respectively.Correction factors of 0.45 and 0.54 were used according to Brookes et al.(1985)and Beck et al.(1997)to determine MBC and MBN,respectively.Dissolved organic N(DON)was calculated as the difference between TDN and DIN.

The ZTs used in the present study are a bypro-duct from a quarry located near Sorano Village(central Italy)that is mainly exploited to obtain blocks and bricks for construction and gardening purposes.

Calculation of soil MB and net15N microbial immobilization rates. To measure the N isotopic signature of the soil MB(Dijkstra et al.,2006),we exploited the very high δ15N of the pig slurry employed in the NH+4-enrichment process of CT to trace and verify its interactions with MB.Microbial biomass isotopic signature(MB δ15N)was determined only for CNTR and pure CZ at the beginning of the incubation and 10CZ on days 2,9,and 16 as no differences in isotopic signature were expected between CNTR,5NZ,and 15NZ.Extraction-fumigation-extraction(EFE)method was employed to determine MBC and MBN isotopic signature(Widmer et al.,1989).Briefly,30 mL of 0.1 mol L−1K2SO4was added to 2 g soil.The suspension was shaken for 1 h and then filtered through ash-free paper.The residual soil in the vial was then transferred to the filter paper by adding new extractant,shaking,and pouring the suspension onto the same filter.The soil was then re-extracted by adding 15 mL of 25 mmol L−1K2SO4and 1 mL CHCl3,shaking for 1 h,and filtering with ash-free filter paper.The extract was then freeze-dried and analyzed with an Elementar Vario Micro Cube elemental analyzer(Elementar,Langenselbold,Germany)coupled with an ISOPRIME 100 isotopic ratio mass spectrometer(Isoprime,Cheadle,UK)operating in a continuous- flow mode.The amount of 15N incorporated into MB(MB15N,mg15N kg−1MB)over time was back calculated from MB δ15N and the amount of MBN according to Eqs.1 and 2 as follows∶

Statistical analysis

To evaluate significant differences between the treatments,data were checked to meet parametric statistic assumption.Successively,repeated measures analysis of variance(ANOVA)and Fisher’s least signi ficant difference(LSD)tests were conducted at a P level of 0.05 for each sampling time.SigmaPlot 12.0 was employed to run statistical analyses.

RESULTS

Soil inorganic N forms

By relating MBC and ergosterol results(Fig.2),it was clearly shown that samples from 10CZ had a tendency in low MBC and ergosterol contents,while especially samples from 5NZ in high ergosterol content.

银行一年名义利率(X5)与寿险保费收入之间呈现显著的负相关，这说明当银行利率增加时，寿险购买者通常将寿险保单抵押或直接退保以取得现金向其他货币市场或资本市场投放,寿险需求下降;反之,在银行利率下降时,由于寿险公司对保单利率的调整具有迟延性,这时人们通常会积极投保,以此获得低价格高收益的保障,寿险需求上升。

营养过剩是肥胖发生最主要的诱因，肥胖不仅可以造成学生各种代谢障碍，严重的还会增加患糖尿病、高血压、心脑血管疾病、痛风等的风险[3]；营养过剩也是导致龋齿发生的重要因素，高蛋白、高热量食物在口腔积存，会增加其龋齿发生的几率；营养过剩的学生容易出现一些心理问题，肥胖人群经常受到身边人的嘲笑，这样会使得他们出现自卑、自闭的现象。

After an incubation period of 2 d,all the treatments exhibited a significantly lower NO−2-N content compared with that of 10CZ with a peak of 20 mg kg−1(P ＜ 0.05)(Table III).On day 7,soil NO−2-N content in 10CZ remained high(P＜0.05);however,it was considerably lower than that on day 2.From day 9,small differences were observed among the treatments(P＜0.05);however,there was no particular trend.

Soil pH and dissolved C and N

Soil pH ranged from 7.73 to 7.90,with no signi ficant differences between the treatments and no variation during the incubation period(P＞0.05)(Table IV).

在此次研究中,窄谱中波紫外线对寻常型银屑病的护理我们开展了分析研究,结果显示,经过治疗后,对照组患者的临床治疗有效率是60%,观察组患者的临床治疗有效率是96%,两组患者的临床治疗有效率对比存在统计学差异性(P<0.05)。该结果和其他的一些研究报道相符合[4]。因为心理护理对于患者的焦虑、抑郁、自卑等情绪有很好的缓解效果,让患者的精神状态保持良好,促进患者的病情恢复。饮食护理能够让患者的身体状态得到恢复,防止光反应对治疗效果产生影响,治疗阶段为患者提供个性化的护理指导,能够让治疗的效果获得提升[5]。所以,患者接受护理后的效果比较突出。

Soil DOC content ranged from 26.7(in 15NZ)to 67.9(in 10CZ)mg kg−1(Table IV).Dissolved organic C was always higher in 10CZ than that in other treatments with an increase with time from day 9 until the end of the incubation period(P＜0.05).Other treat-ments did not show significant differences in DOC(P＞0.05).

TABLE III Contents of N in different formsa)in the soil without addition(CNTR)or with addition of 5%(5NZ)and 15%(15NZ)natural chabazite-rich zeolitite and 10%NH+4-enriched chabazite-rich zeolitite(10CZ)on days 2,7,9,11,and 16 of the incubation period

a)TDN=total dissolved N;DIN=dissolved inorganic N;DON=dissolved organic N;MBN=microbial biomass N. b)Means±standard deviations(n=3). c)Means in the same column followed by different letters are significantly different on each sampling day(P ＜ 0.05)based on analysis of variance and Fisher’s least significant difference test. d)Below the detection limit.

Treatment TDN NH+4-N NO−3-N NO−2-N DIN DON MBN mg kg−1 Day 2 CNTR 49.8±2.4b)ac) 13.9±3.4a 30.2±1.7a 0.7±0.1a 44.8±1.8a 4.99±3.95a 19.1±7.0a 5NZ 48.7±0.6a 12.2±1.0a 35.9±1.2b –d) 48.1±0.9a 0.52±0.30a 16.3±1.8a 15NZ 48.9±1.2a 10.9±0.5a 34.7±0.9ab – 45.7±1.5a 3.25±0.22a 18.6±1.5a 10CZ 320.8±29.8b 68.7±4.1b 151.4±4.2c 20.0±0.5b 240.0±8.3b 80.71±37.20b 74.0±3.0b Day 7 CNTR 48.5±2.6a 7.6±0.7a 39.5±2.6b 0.2±0.1a 47.3±2.2a 1.15±1.10a 24.0±6.1a 5NZ 47.0±1.1a 11.0±1.0b 33.9±0.9a 0.6±0.2a 45.5±1.1a 1.55±0.21a 19.5±2.9a 15NZ 57.8±3.0a 10.8±0.2b 43.8±2.7b 0.4±0.2a 55.0±2.8b 2.74±2.23a 19.0±7.4a 10CZ 382.2±8.0b 68.8±4.0c 145.4±1.6c 4.3±0.3b 218.5±2.5c 163.72±10.21b 40.1±28.1a Day 9 CNTR 50.5±3.4a 9.7±0.7b 25.0±4.6a 7.6±1.0c 42.2±5.3b 8.29±5.91a 11.0±3.9a 5NZ 47.5±0.9a 6.2±0.7a 29.4±0.9a 0.3±0.1a 35.8±0.3ab 11.65±0.78a 9.7±5.9a 15NZ 52.1±0.2a 7.7±1.0ab 24.2±0.3a – 32.0±0.8a 20.05±0.65b 6.9±4.2a 10CZ 405.6±79.5b 59.1±2.7c 189.7±3.5b 1.9±0.1b 250.6±3.8c 155.04±82.36c 131.9±5.8b Day 11 CNTR 39.2±2.7a 4.8±0.5a 29.5±0.4a 0.3±0.2a 34.6±0.5a 4.63±2.73a 22.2±13.6a 5NZ 50.1±14.4a 4.3±0.8a 31.4±0.3a 0.3±0.1a 36.0±0.8a 14.06±14.79a 11.1±4.3a 15NZ 46.4±1.3a 5.1±0.9a 30.2±0.7a 0.2±0.1a 35.6±1.6a 10.84±2.39a 14.1±3.3a 10CZ 534.5±154.4b 46.7±2.5b 300.5±5.7b 2.4±0.2b 349.6±3.3b 184.89±151.14b 220.4±70.0b Day 16 CNTR 49.4±2.8a 5.0±0.7a 36.5±0.1a – 41.7±0.5a 7.72±3.24a 20.6±14.8a 5NZ 68.0±0.1a 5.4±0.5a 49.8±0.2b 3.3±0.3b 58.6±0.8c 9.44±0.83a 21.7±5.9a 15NZ 54.7±2.8a 6.5±0.5a 40.1±0.1a – 46.6±0.5b 8.11±2.63a 42.0±5.3a 10CZ 375.5±6.7b 29.0±0.8b 274.2±10.1c 2.2±0.1a 305.4±9.2d 70.10±2.71b 237.5±15.6b

Soil TDN content ranged from 39.2(in CNTR)to 534(in 10CZ)mg kg−1(Table III).No significant di-fferences in TDN were observed among CNTR,5NZ,and 15NZ(P＞0.05);however,10CZ exhibited higher TDN content throughout the whole incubation period(P＜0.05).Dissolved inorganic N was calculated as the sum of NH+4-N,NO−3-N,and NO−2-N,while DON was calculated as the difference between TDN and DIN.

Soil ergosterol

Soil ergosterol content was quite similar in CNTR,15NZ,and 10CZ with no significant differences(P ＞0.05),except on day 2,when the ergosterol content was significantly higher in 15NZ than CNTR and 10CZ(P＜0.05)(Table IV).The ergosterol content increased significantly in 5NZ from day 9 until the end of the incubation period(P＜0.05),reaching the highest value on day 16.

Soil MBC and MBN

Soil MBC content ranged from 164(in 10CZ)to 348(in CNTR)mg kg−1(Table IV).On day 2,no significant difference was observed among the treatments(P＞0.05);however,on day 7,MBC was significantly higher in CNTR than other treatments.Furthermore,similar to day 2,no significant differences among the treatments were observed on days 9 and 11.However,by the end of the incubation period,MBC in 15NZ increased significantly(P＜0.05).

Soil MBN content ranged from 6.9(in 15NZ)to 238(in 10CZ)mg kg−1(Table III).Throughout the incubation period,10CZ was the only treatment which showed significant differences in MBN with respect to other treatments(P＜0.05).On day 2,MBN was significantly higher in 10CZ compared with CNTR and both the two NZ treatments(P＜0.05).On day 7,albeit the average values remained very high,a high variability among the three replicates exhibited no significant differences among the treatments(P ＞ 0.05).From day 9,MBN in 10CZ increased significantly tovalues higher than 130 mg kg−1,differing significantly from the other treatments(P＜0.05),and further increased on days 11 and 16,reaching the maximum values recorded during the incubation period.The MBN in 10CZ was strongly correlated with NO−3-N and NH+4-N during the incubation period(Fig.1).

离散相：为了明显地观测出气流辅助的防飘移机理，喷雾压力为0.4MPa，对应流量为0.015L/s，雾滴直径分布范围为52.49～278.95μm，分布指数3.45，平均直径为160.12μm。在模拟区域中接触到地面的雾滴，为沉积雾滴，设为“trap”；从壁面和出口边界逸出的雾滴，为飘移雾滴设为“escape”；由于雾滴与气流接触要发生传热、传质过程，所以假设雾滴运动过程中发生蒸发。

TABLE IV pH,dissolved organic carbon(DOC),ergosterol,and microbial biomass C(MBC)in the soil without addition(CNTR)or with addition of 5%(5NZ)and 15%(15NZ)natural chabazite-rich zeolitite and 10%NH+4-enriched chabazite-rich zeolitite(10CZ)on days 2,7,9,11,and 16 of the incubation period

a)Means±standard deviations(n=3). b)Means in the same column followed by different letters are significantly different on each sampling day(P ＜ 0.05)based on analysis of variance and Fisher’s least significant difference test.

Treatment pH Ergosterol DOC MBC mg kg−1 Day 2 CNTR 7.74±0.05a)ab) 2.78±0.29a 35.0±5.1b 233±16a 5NZ 7.88±0.01a 2.69±0.23a 38.9±0.3b 257±47a 15NZ 7.90±0.02a 4.46±1.39b 27.6±2.0a 231±21a 10CZ 7.84±0.03a 2.91±0.99a 47.7±5.4c 226±15a Day 7 CNTR 7.84±0.03a 3.39±0.50b 36.3±3.9b 347±93b 5NZ 7.78±0.01a 2.35±0.16a 34.8±2.3b 212±11a 15NZ 7.85±0.03a 2.26±0.32a 28.9±1.3a 252±58a 10CZ 7.73±0.06a 2.36±0.28a 45.2±2.5c 237±43a Day 9 CNTR 7.84±0.04a 2.10±0.05a 48.7±27.4ab 194±61a 5NZ 7.76±0.07a 3.77±1.80a 40.0±5.4a 202±7a 15NZ 7.86±0.03a 2.96±0.38a 38.8±16.2a 197±48a 10CZ 7.86±0.01a 1.98±0.55a 66.7±32.5b 165±70a Day 11 CNTR 7.78±0.06a 2.30±0.41a 30.1±2.2a 260±82a 5NZ 7.85±0.01a 5.47±1.73b 32.3±1.2a 191±9a 15NZ 7.88±0.01a 2.25±0.13a 26.7±2.6a 207±12a 10CZ 7.84±0.03a 2.03±0.20a 60.4±0.6b 184±12a Day 16 CNTR 7.87±0.04a 3.27±0.58a 47.6±16.8a 240±102a 5NZ 7.77±0.05a 6.71±3.20b 39.7±6.1a 227±9a 15NZ 7.84±0.03a 2.76±1.15a 34.3±2.8a 330±58b 10CZ 7.80±0.02a 2.38±0.32a 67.9±10.5b 190±8a

Soil NH+4-N content ranged from 4.3(in 5NZ)to 68.8(in 10CZ)mg kg−1(Table III).The NH+4-N content was similar throughout the incubation period for CNTR,5NZ,and 15NZ with no significant differences(P＞0.05).For 10CZ,exchangeable NH+4-N was always significantly higher than that of the other treatments(P＜0.05),attributed to the N adsorbed by CZ.A decrease in NH+4-N(P＜0.05)in 10CZ was observed from days 9 to 16,reaching half of the initial amount.

Fig.1 Relationships of microbial biomass N(MBN)with NO−3-N and NH+4-N in the soil with addition of 10%NH+4-enriched chabazite-rich zeolitite on days 2,7,9,11,and 16 of the incubation period.

Fig.2 Scatter plot of ergosterol content against microbial biomass C(MBC)in the soil without addition(CNTR)or with addition of 5%(5NZ)and 15%(15NZ)natural chabazite-rich zeolitite and 10%NH+4-enriched chabazite-rich zeolitite(10CZ)during the 16-d incubation period.Black dashed line defines samples from 5NZ,in which a substantial increase in ergosterol content occurred during the incubation;light gray dashed line defines samples from 10CZ,in which MBC tended to be lower than that in CNTR.

Microbial biomass δ15N and net15N immobilization rates

The analysis of MB isotopic signature by the EFE method revealed significant differences(P ＜ 0.05)between CNTR and 10CZ.The MB in CNTR exhibited a marginal negative δ15N value of−4.2‰,and it was assumed constant throughout the incubation period as there was no further addition of N,while the isotopic signature of pure CZ was 43.6‰(Table II).On day 2,MB δ15N in 10CZ was highly variable;however,it was significantly higher(P＜0.05)than that in CNTR with an average value of 12.9‰(Table V).On day 9,MB δ15N in 10CZ increased to 25.6‰,while on day 16,it decreased to 15.3‰,still significantly higher with respect to that in CNTR(P＜0.05).The amount of MB15N calculated from Eqs.1 and 2 resulted 265µg 15N kg−1MB on day 2,495 µg15N kg−1MB on day 9,and 883 µg15N kg−1MB on day 16(Fig.3a).Net15N immobilization rate in 10CZ calculated from Eq.3 was 31.5 µg15N kg−1MB d−1between days 2 and 9,while the rate almost doubled to 55.4 µg15N d−1between days 9 and 16(Fig.3b).

TABLE V Microbial biomass isotopic signature(MB δ15N)for the soil without addition(CNTR)at the beginning of the incubation period and the soil with addition of 10%NH+4-enriched chabaziterich zeolitite(10CZ)on days 2,9,and 16 of the incubation period

Treatment MB δ15N‰CNTR −4.2 10CZ on day 2 12.9 10CZ on day 9 25.6 10CZ on day 16 15.3

DISCUSSION

NZ effects

In the present study,pure NZ was characterized by very low MBC and MBN,indicating a weak colonization of CHAZT at natural state by microorganisms(Table II).Ergosterol measurement is commonly employed as a marker for fungal biomass,as it is a membrane sterol in fungi,and used to study fungi in various ecosystems,including temperate soils(Johnson and McGill,1990;Gessner and Chauvet,1993;Ruzicka et al.,2000).Ergosterol was not detected in NZ(Table II),and thus fungal abundance in pure NZ was below the detection limit,suggesting that fungi were not introduced into the soil by the amendment.

Fig.3 Amounts of15N immobilized in the soil microbial biomass N(MB15N)for the soil with addition of 10%NH+4-enriched chabazite-rich zeolitite(10CZ)on days 2,9,and 16 of the incubation period(a)and net15N immobilization rates(15Nimm)in the soil microbial biomass N for 10CZ between days 2–9 and 9–16 of the incubation period(b).Vertical bars represent standard deviations of the means(n=3).

Addition of NZ to soil did not affect MBC and MBN dynamics during the incubation period,and hence microbial immobilization was likely not significantly in fluenced by NZ amendments in the short term(Tables III and IV).However,ergosterol measurements suggested that the relative amount of fungal biomass compared to the total MB was in fluenced by NZ amendments,especially at a lower application rate(5NZ),as indicated by the relationship between ergosterol and MBC(Fig.2).It was,in fact,evident that 5NZ was characterized by a high ergosterol content from day 9,suggesting an increase in fungal population.Fungi are known to have a lower N requirement compared to bacteria(G¨usewell and Gessner,2009),because of their higher cellular C/N ratio.A broad set of factors such as agricultural management,soil pH,moisture,and temperature,and atmospheric CO2 that are known to in fluence fungal abundance in agricultural soils(Strickland and Rousk,2010)were maintained constant during the incubation period.Therefore,a possible explanation for the observed results might be the realtively lower immediate nutrient availability,because of a competition for the dissolved mineral N species between NZ(adsorption)and MB(assimilation)in the short term.It is plausible that the addition of NZ with a CEC equal to 1420 mmol kg−1(Malferrari et al.,2013)increased the soil CEC,as reported by Gholamhoseini et al.(2013)after using zeolite-amended cattle manure in sun flower field.Similar observation was reported by Ferretti(2017c)directly in the ZeoLIFE experimental field.However,CEC was not measured in the soil-zeolite mixture used.The addition of an initially N-deficient mineral with a very high CEC and affinity for NH+4might have established a sort of competition among soil microorganisms in the short term for the dissolved mineral N.

Ergosterol. Ergosterol content was determined following the method proposed by Gong et al.(2001)with some modifications.The samples were freezedried at−50 °C,and 6 mL methanol(Me-OH)was added to 4 g sample.The suspension was homogenized with a hand vortex,placed in an ultrasound bath for 15 min,and centrifuged at 10518×g for 15 min.The supernatant was filtered using a polytetra fluoroethylene syringe membrane filter(4-mm diameter,0.45-µm pore size),and then kept in the dark until analysis with an Agilent Technologies In finity 1290 high performance liquid chromatography system(Agilent Technologies,Santa Clara,USA).The injection volume of the sample was 5 µL,while the flux rate was 0.5 mL min−1 with 95%Me-OH in H2O as an eluent phase and a Zorbax Eclipse Plus C18 rapid resolution 2.1 mm×50 mm column with 1.8-µm porosity as a solid phase.Ergosterol was determined using a UV detector at 282 nm.

CZ effects

Pure CZ was actively colonized by microorganisms;however,fungi were not introduced into the soil by pure CZ(Table II).The addition of CZ to soil exhibi-ted no effects on fungal biomass during the incubation period,but significantly increased both DIN and DON,and thus TDN(Table III),suggesting a strong mineralization process.In particular,a high NO−2-N content on day 2 suggests the occurrence of ammonia oxidation,the first step in nitrification(Ruiz et al.,2003).The high NO−2-N accumulation indicated that the total nitrification process and therefore the production of NO−3might have been inhibited at the early stages of incubation.It is plausible that this inhibitory effect was due to high NH3levels,also favored by the sub-alkaline pH,which decreased the activity of nitriteoxidizing bacteria(NOB),thereby promoting NO−2accumulation(Stojanovic and Alexander,1958;Morrill and Dawson,1967;McGilloway et al.,2003).Considering the amount of CZ added to 1 kg soil(100 g)and its residual NO−3-N load(146 mg kg−1),the addition of CZ to the soil incorporated a total of 14.6 mg NO−3 kg−1.This amount represent only 9.6%of the total soil NO−3-N for 10CZ on day 2 of incubation.This minimal addition of residual NO−3-N might have partially increased microbial biomass and stimulated decomposition process.

It was apparent that after 9 d,MBN started to increase further in CZ,along with contemporaneous decline of NH+4-N and increase of NO−3-N(Fig.1),suggesting an increase in nitrification.However,this high availability of NH+4might have stimulated not only NO−3production,but also microbial immobilization into biomass.This was supported by the isotopic analysis conducted on three different samples collected on days 2,9,and 16 of 10CZ(Table V).The δ15N of the pure CZ was 43.6‰and well representative of the pig slurry isotopic signature employed in the enrichment process,while the MB δ15N in CNTR was−4.2‰ at the beginning of the incubation.In this respect,the MB δ15N in 10CZ was strongly in fluenced by CZ isotopic signature since day 2,especially on days 9 and 16.This indicates that a high amount of15N was assimilated by MB(Dittert et al.,1998).This is better reflected by the amount of15N in the soil MB(Fig.3a).The rates at which15N atoms were incorporated almost doubled from day 9,concomitantly with a high net NH+4decrease.The decrease in NH+4levels by microbial immobilization might have also reduced the substrate for NH3production,resulting in lower inhibitory effects on NOB,and thus a more favorable condition for NO−3 production.

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Notwithstanding that the high nitrification occurred,soil pH did not decrease,suggesting the excellent buffering capacity of CZ(Colella,1999;Rˇadulescu,2013)together with soil carbonates.These results partially agree with the findings of McGilloway et al.(2003),who found that in a zeoponic substrate consisting of NH+4-enriched clinoptilolite zeolites,nitri fication was higher than that in soil systems.They also found that ammonium-oxidizing bacteria(AOB)were higher than NOB,causing NO−2accumulation.However,they did not observe a good buffering effect of the substrate.Leggo(2000),who used NH+4-enriched clinoptilolite after mixing with poultry manure to produce an organo-zeolitic substrate,stated that a possible explanation for the high NO−3-N concentration visible from day 1 after the application might be due to the interactions of CZ with the soil solution.In this light,the high natural salinity of the soil employed in the present study might have induced cation exchange reactions with the NH+4adsorbed into the zeolites,thus increasing the availability of the substrate required for nitrification(Di Giuseppe et al.,2014).

High microbial activity during incubation and thus high consumption of O2might have caused anaerobic microniches towards the end of the incubation period(Mastrocicco et al.,2011),causing a decrease in NO−3-N content observed from days 11 to 16 via reduced nitrification or increased denitrification.

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The increase in soil DOC visible on day 2 was probably due to the residual DOC caused by CZ amendment,as the addition of 10%CZ might have raised soil DOC to around 12 mg kg−1.However,the NO−3-N content started to increase on day 9,along with increased DOC,supporting enhanced mineralization process.These results further suggest that CZ addition supplied an immediately available N source to microorganisms that are able to trigger degradation of soil organic matter,thus significantly increasing soil DOC and DON(Jokubauskaite et al.,2015).Considering the above-mentioned points,the combination of the following events,i)the supply of a minimal amount of residual NO−3and DOC,ii)the probable exchange processes with soil cations,and iii)the colonization of CZ,might have caused a positive priming effect on MB in 10CZ(Kuzyakov et al.,2000).A part of the N introduced was thus immediately available to microorganisms for immobilization into their biomass,resulting in high cellular N levels that sharply increased during the incubation period.

The results of the present study did not support the second hypothesis,because the CZ employed did not act as a slow-release N source,but caused a priming effect on soil MB.

CONCLUSIONS

Amendment with 5%NZ increased soil ergosterol content over time,suggesting an increase in fungal biomass and thus indicating a possible positive practice for increasing soil C sequestration.However,a similar result was not observed when the soil was amended with 15%NZ,suggesting that the application rate of NZ can in fluence the nutrient availability to soil MB in the short term with different effects on fungal biomass development.The N incorporated with CZ was immediately available to soil microorganisms,which should be taken into account for the potential application of CZ in the agricultural context,as this specific CZ will act not as a slow-release fertilizer,but a pool of immediately available N to soil MB that may trigger both immobilization and mineralization processes.It is thus recommendable to apply CZ immediately before the growing season to minimize N losses or,alternatively,use it as a component of greenhouse cultivation systems.The present study could serve as a basis to foster long-term experiments,both in the laboratory and field.

ACKNOWLEDGEMENTS

The authors are grateful to Dr.Claudio NATALI,Prof.Gianluca BIANCHINI,and Miss Astrid HOBEL for their help and advices during laboratory procedures.This work has been co-funded by the EU-funded ZeoLIFE project,European Union(No.LIFE10 ENV/IT/000321)and UNIFE young researchers grant 2015.It is related to the EU-funded Eclaire project,European Union(No.FP7-Env.2011.1.1.2-1 282910)and project NitroAustria,Austrian Climate Research Programme(No.KR14AC7K11916).

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