波罗的海芬兰湾各沿海监测站对反硝化和ANAMMOX过程中的季节性变化和短期变化的研究

PRIMARY RESEARCH PAPER

Seasonal and short-term variation in denitri?cation

and anammox at a coastal station on the Gulf of Finland,Baltic Sea

Susanna Hietanen ?Jorma Kuparinen

Received:3November 2006/Revised:30May 2007/Accepted:16June 2007/Published online:10July 2007óSpringer Science+Business Media B.V.2007

Abstract Benthic processes were measured at a coastal deposition area in the northern Baltic Sea,covering all seasons.The N 2production rates,90–400l mol N m –2d –1,were highest in autumn-early winter and lowest in spring.Heterotrophic bacterial production peaked unexpectedly late in the year,indicating that in addition to the tem-perature,the availability of carbon compounds suitable for the heterotrophic bacteria also plays a major role in regulating the denitri?cation rate.Anaerobic ammonium oxidation (anammox)was measured in spring and autumn and contributed 10%and 15%,respectively,to the total N 2production.The low percentage did,however,result in a signi?cant error in the total N 2produc-tion rate estimate,calculated using the isotope pairing technique.Anammox must be taken into account in the Gulf of Finland in future sediment nitrogen cycling research.

Keywords Denitri?cation áAnammox áBenthic bacterial production áOxygen consumption áBaltic Sea

Introduction

The Gulf of Finland is a eutrophic,highly seasonal sub-estuary of the Baltic Sea.It is directly con-nected to the Baltic Proper at its western end and is under the in?uence of the Neva River at the eastern end.In the easternmost part of the Gulf,primary production is limited by phosphorus avail-ability,whereas the central and western parts are

nitrogen-limited (Kivi et al.,1993;Pitka

¨nen &Tamminen,1995).Nutrient loading into the Gulf has decreased in recent decades,due to the active protection of the Gulf and economic changes (depression)in the surrounding states of Russia

and Estonia (Pitka

¨nen et al.,2001).Still,120kt of nitrogen enter the Gulf of Finland every year (Kiirikki et al.,2003).Denitri?cation,the sequen-tial reduction of nitrate to nitrogen gas,is a process that removes nitrogen from the aquatic ecosystem.

Mass balance calculations (Perttila

¨et al.,1995)as well as ecosystem models (Kiirikki et al.,2006)indicate that about 70kt nitrogen is denitri?ed in the Gulf of Finland annually.Denitri?cation has been extensively measured in the open Baltic Sea depositional areas (Tuominen et al.,1998).How-ever,the rates measured have been lower than

Handling editor:J.Cole

S.Hietanen áJ.Kuparinen

Department of Biological and Environmental Sciences,University of Helsinki,P.O.BOX 65,Helsinki 00014,Finland

S.Hietanen (&)áJ.Kuparinen

Tva

¨rminne Zoological Station,University of Helsinki,Hanko 10900,Finland

e-mail:susanna.hietanen@helsinki.?

Hydrobiologia (2008)596:67–77DOI 10.1007/s10750-007-9058-5

predicted,and based on these measurements, denitri?cation has been calculated to remove only 45kt of nitrogen from the Gulf of Finland annu-ally.This estimate is based solely on measurements performed in the open Baltic Sea depositional areas,assuming that denitri?cation proceeds at the same rate throughout the entire basin.The shal-lower coastal areas are hypothesized to be sites of more intense denitri?cation due to differences in temperature and nitrate and carbon input.So far, no data have been published concerning coastal denitri?cation in the Gulf of Finland,except from the inner Neva estuary,where it was very low (Gran&Pitka¨nen,1999).Another natural process removing?xed nitrogen from the aquatic ecosys-tem,anaerobic ammonium oxidation(anammox), has recently been found in marine sediments also (Dalsgaard&Thamdrup,2002;Thamdrup& Dalsgaard,2002;Trimmer et al.,2003).No infor-mation on the importance of this process,in which ammonium is oxidized with nitrite to form nitrogen gas,is available from the Baltic Sea area.

To estimate seasonal and short-term variation in coastal nitrogen removal and carbon cycling, we measured denitri?cation and benthic bacterial production,oxygen consumption and oxygen penetration into the sediment at a coastal station in the northern Gulf of Finland.The processes were measured in May,August,October and December2003and in April2004.The contribu-tion of anammox to nitrogen reduction was estimated in May and August.

Methods

Study area and sampling

Samples were collected from a coastal station in the northern Gulf of Finland(Tva¨rminne Storfja¨rden, 59°51￠21,23°15￠56),representing a typical outer archipelago depositional area consisting of soft mud.The water depth at the sampling station is 33m,and the water column usually is thermally strati?ed from June to September.The highest bottom water temperatures,up to13°C,are found in late autumn when thermal strati?cation breaks, and the lowest,below2°C,in early spring when the water column has yet to stabilize after ice-out.Sedimentation at the station shows a typical pattern of about80%of the sedimenting carbon reaching the bottom at the end of the spring bloom in May, with little sedimentation during the rest of the year (Heiskanen&Leppa¨nen,1995;Heiskanen& Tallberg,1999).In an intensive study in1992,the total primary sedimentation at the station from March to October was34g C m–2(Heiskanen& Tallberg,1999),of which phytoplankton carbon contributed8.3g C m–2(Tallberg&Heiskanen, 1998).

In the present study,samples were collected throughout the year in1to2-week periods,with several sampling days in each period(Table1). Temperature and salinity of the near-bottom water were recorded daily using a CTD probe(SIS CTD plus100,Klausdorf/Schwentine,Germany).The sediment was sampled with a Gemini twin corer (ID of the cores80mm,length80cm).The oxygen and nitrate concentrations in the overlying water were measured from a single core,about2cm above the sediment surface,on every sampling day. The sediment dry weight and organic content(loss on ignition)were measured from a single core once every sampling period from the topmost1cm,and C%and N%were measured in the same samples in all except the April2004sampling period.The oxygen pro?les in the sediment were measured in October,December and April in undisturbed subsample cores(see denitri?cation),using Clark-type oxygen microelectrodes having100-l m tips (OX-100,Unisense A/S,Denmark),giving a spatial resolution of about200l m.

Denitri?cation and anaerobic ammonium oxidation

Denitri?cation was measured every sampling day, using the isotope pairing technique(IPT;Nielsen, 1992).Three replicate subsamples were taken in clear plastic(acrylic)cores(diameter 2.6cm, height9cm)so that about half the core was?lled with the sediment and half with the water from above.The samples were enriched with K15NO3 (98at.%labelling;Cambridge Isotope Laborato-ries,MA,USA)to a?nal concentration of100l M and incubated,with a magnetic stirrer on the lid of the cores,at in situ temperature in darkness for3h. Microbial activity was then terminated by adding

1ml of 100%ZnCl 2,the samples were mixed,and subsamples of the sediment-water slurry were transferred into gastight 12-ml glass vials (Exetain-er;Labco,High Wycombe,UK).These were sent to the National Environmental Research Institute,Silkeborg,Denmark,for analysis of N 2isotopic composition,using a gas chromatographic column coupled to a triple-collector isotopic mass ratio spectrometer (RoboPrep G +in line with Tracer-Mass,Europa Scienti?c,Crewe,UK).In May and August,the validity of the IPT at this coastal site was evaluated by testing a major assumption behind the method,namely the independency of the rate of denitri?cation of the 15NO 3–concentra-tion used in the incubations (Nielsen,1992).Brie?y,in sediments where denitri?cation is the only N 2-producing process,the estimated dinitro-gen (28N 2)production rate,based on naturally occurring 14NO 3–,is independent of the incubation concentration of the added 15NO 3–,whereas the production rate of labelled compounds (29N 2and 30

N 2)is linearly dependent on the concentration added.If anammox is present,both the 28N 2production rate and the production rate of labelled compounds correlate positively with the 15NO 3–concentration used in the experiment.If this is the case,the true rate of 28N 2production must be

estimated from the 14NO 3–/15

NO 3–ratios in the reducing zone and the ratios of labelled compounds produced at different 15NO 3–incubation concentra-tions,using revised equations (r-IPT;Risgaard-Petersen et al.,2003,2004b ).The resulting new 28

N 2production estimate is lower than the estimate calculated using the classical IPT,since part of the observed 29N 2production is attributed to anammox instead of denitri?cation.Three sets of samples were incubated with different concentrations of 15

NO 3–(40,100and 400l M)using randomized

blocks design.The results from these experiments

were ?rst analysed for signi?cant differences between rates in different concentrations using one-way randomized blocks ANOVA (a =0.05)and then further recalculated according to r-IPT.Benthic bacterial production

Benthic bacterial production was measured on every sampling day (except one)in the topmost 1cm of the sediment,using the leucine incorpora-tion method modi?ed for sediment samples (Hietanen et al.,1999).In short,100-l l sediment samples were slurried with ?ltered near-bottom water in microcentrifuge tubes.At the beginning of every sampling period,the saturation level of the 14C-leucine (3.7MBq/ml,Perkin Elmer Life Sciences,MA,USA)was measured by incubating samples with different 14C-leucine concentrations.The measured saturating concentration was then used in all the following incubations,run in three replicates and one blank.The samples were incu-bated at in situ temperature for 40–60min (tested for linearity of the uptake)and killed with 10%TCA.The unincorporated isotope was removed by repeated centrifugation after washing once with 80%ethanol and twice with 10%TCA.The samples were then suspended in a scintillation cocktail (Instagel Plus;Packard Instruments,Frankfurt,Germany)and gel was formed by adding water according to the manufacturer’s instructions.Radioactivity was recorded in a scintillation coun-ter (WALLAC 1414LSC;Wallac,Turku,Finland).Isotope dilution was measured once every sampling period,except in May 2003,by adding increasing amounts of unlabelled leucine to samples incubated with a constant amount of 14C-leucine (at saturation level)and using the reciprocal plot for calculation

Table 1Sampling periods,number of measurements and

environmental conditions 5cm above the sediment surface within periods

May-03

Aug-03Oct-03Dec-03Apr-04Denitri?cation 3

8883Anammox

11000Benthic bacterial production 38873Sediment oxygen consumption 07880O 2pro?les

009213Temperature (°C) 2.0 3.0 5.9 4.4 2.6Salinity 6.35 6.83 6.62 6.46 5.82O 2(l M)

33095310380390NO 2–+NO 3–

-N (l M)

0.29

1.40

1.64

2.26

0.29

(Findlay,1993).Leucine incorporation was con-verted to carbon production according to Simon& Azam(1989),using the measured isotope dilution factor.

Diffusive oxygen consumption in sediment

The sediment oxygen consumption was calculated in August,October and December from the con-centration change during incubation in plastic (acrylic)chambers similar to those used for the denitri?cation measurements,but equipped addi-tionally with a sampling tube at the side,1cm higher than the middle of the chamber.A series of 3–6samples were incubated in the dark,with one sample killed at the beginning of the incubation and thereafter every45min.The oxygen concentration was measured using Winkler titration.Oxygen diffusion into the chambers through the walls was measured in August.Sterile(0.2-l m?ltered)sea-water was bubbled with nitrogen gas until the ambient90-l M O2concentration was attained.The incubation chambers were?lled with the bubbled seawater,incubated in the coldroom the same way as the samples and the concentration increase in the sterile water was followed over time by Winkler titration.Diffusion of oxygen into the chambers through the walls was50l M O2h–1.This was taken into account in calculating the oxygen consumption rates in August.During all the other measuring periods the ambient oxygen concentration was approximately at saturation level and,according to Fick’s First law,no diffusion into the chambers was expected.After incubation the sediment sam-ples were sieved(mesh size100l m)to check for the presence of macrofauna.The few samples with animals,mainly Macoma baltica(L.),were omitted from the?nal calculations.Therefore the calculated rates represent diffusive oxygen consumption,not total sediment uptake.

Results

Annual variation in hydrography and oxygen conditions

The temperature in the near-bottom water varied from1.1°C to6.5°C between the sampling peri-ods,showing the typical annual dynamics of a coastal station.The water column was completely mixed in the?rst sampling period in May2003, with good oxygen conditions(330l M O2)in the bottom water,and strati?ed by temperature and salinity in August2003,with a clearly lowered oxygen level(95l M O2).By October2003,the strati?cation had deteriorated and the mixing had replenished the depleted oxygen stores(Table1). The average depth of oxygen penetration into the sediment was 3.2mm in October(SD0.3), 3.6mm in December(SD0.7)and 2.5mm in April(SD1.3).

Seasonal and short-term variability in

denitri?cation

There was wide and statistically signi?cant varia-tion in denitri?cation activity between seasons, whereas the short-term variation between the days within a sampling period was not signi?cant,except in December when a value from one day was exceptionally high(ANOVA,a=0.05,P<0.01). Denitri?cation was highest in October–December and lowest in April and May(Fig.2b).The bulk of denitri?cation was always coupled with nitri?cation (Fig.2b).Coupled nitri?cation-denitri?cation(Dn) was positively correlated(P<0.05)with sediment oxygen consumption and bacterial carbon produc-tion,as well as with temperature and nitrate concentration.Denitri?cation based on the nitrate available in the water column(Dw)correlated positively with nitrate availability and bacterial carbon production,but was not signi?cantly corre-lated with temperature.Neither Dn nor Dw was correlated with the O2concentration. Contribution of anammox to nitrogen reduction

In the experiments with increasing15NO3–con-centrations,both14NO3–reduction(28N2produc-tion)and15NO3–reduction(29N2and30N2 production)correlated with the concentration added(May P=0.00and0.00,August P=0.01 and0.00,respectively,Fig.1).Therefore the contribution of anammox was calculated accord-ing to the r-IPT.The rate of anammox was about 10l mol N m–2d–1,corresponding to10%of the total N2production rate in May,and about

30l mol N m–2d–1,corresponding to14%in August.The anammox caused the IPT to overes-timate the N2production rate by80%in May and 150%in August,at the routinely used100l M 15NO

3

–incubation concentration(Fig2a,b).Since we have no reason to believe that anammox would disappear for the rest of the year,the results from the IPT(shown uncorrected in Fig.2a)were also corrected for the effect of anammox outside the measured seasons.We used a conservative estimate of10%contribution to the total N2production(ra)as measured in May to recalculate the results from October,Decem-ber and April(Fig.2b),because we have no

information on the seasonality of the process in the Baltic Sea.However,if the increase in relative importance from May to August were correlated with the overall increase in activity caused by the rising temperature and proceeding of the miner-alization of the sedimented spring bloom,the higher ra levels could have lasted for the rest of the year and,consequently,the values given here for the N2production could still be overestimates.On the other hand,if the percentage of anammox would for some reason decrease from October to April,these new values would be underestimates of the true N2production.The effect is clear when the annual N2production in the Gulf of Finland is calculated by multiplying the rates measured at the coastal station(which are similar to the rates measured in the open sea(Tuominen et al., 1998))for the entire area of the Gulf of Finland

(29,600km2).Using10%anammox,90%deni-tri?cation for May(measured),October,Decem-ber and April and15%anammox,85% denitri?cation for August(measured)gives 39,100t N removed per year(Fig.2b).Using the same data so that10%anammox,90% denitri?cation are used for May(measured)and 15%anammox,85%denitri?cation for August (measured),and no anammox is assumed for October,December and April when it was not measured,gives43,100t N.If anammox is totally overlooked and only the results from classical IPT are used,denitri?cation removes53,800t N annually from the Gulf of Finland(Fig.2a). Seasonal and short-term variability in benthic bacterial production

Benthic leucine uptake became saturated at about 4l M in all seasons.The isotope dilution,mea-sured in all but the May samples,varied from no dilution(factor1)in April to the highest dilution (factor5.2)in December.Benthic bacterial pro-duction was low in the early spring and increased towards the end of the year(Fig.1).Assuming no isotope dilution in May2003(none occurred in April2004),bacterial production increased from

6.5mmol C m–2d–1in May to84mmol

C m–2d–1in December.It varied in a statistically signi?cant manner(a=0.05,P<0.01)daily with-in a season except in April2004(when there were only3sampling days)and between the seasons as well.Benthic bacterial carbon production corre-lated with denitri?cation(Dn and Dw),sediment oxygen consumption,temperature and nitrate concentration.

Sediment oxygen consumption

Oxygen consumption did not vary in a statistically signi?cant manner(a=0.05,P>0.01)daily with-in a season except in October(P<0.01),but varied between the seasons(Fig.1),showing the lowest respiration rates in low oxygen concentra-tions in August(average5.4mmol O2m–2d–1at 95l M O2).There was no difference between the rates in October and December(averages10.1 and11.5mmol O2m–2d–1at310and380l M O2).Oxygen consumption correlated positively with anammox and Dn(but not with Dw),benthic bacterial carbon production,temperature and oxygen concentration.Unfortunately it was only measured in August,October and December, leaving the low-activity season,early spring, unaccounted for.

In August,live animals were found in some of the subsamples almost every day.In these sam-ples the average oxygen consumption was twice the diffusive oxygen consumption.Surprisingly, while the oxygen concentration increased towards the end of the year(Table1),the amount of live macrofauna decreased,so that in October only eight animals were found in the63subsamples and in December only three in45subsamples.In these rare samples with animals the oxygen consumption was increased by about40%and 75%,respectively,compared with the diffusive oxygen uptake.

Discussion

Seasonal variation in N2production

Rates of N2production at the coastal depositional bottom studied,90–400l mol N m–2d–1(excep-tion:one day in December550l mol N m–2d–1), were slightly lower than the rates measured in the central Gulf of Finland(100–650l mol N m–2d–1, Tuominen et al.,1998).The N2production,of which denitri?cation contributed85–90%,fol-lowed an annual cycle similar to that of the open Baltic Sea areas,with low spring values and higher late summer–early winter rates.The driv-ing forces behind the seasonal variation in deni-tri?cation in the open Baltic Sea areas are presumably organic carbon(sedimentation),tem-perature,nitrate concentration and oxygen avail-ability in the sediments.Carbon sedimentation has a2-fold impact,since it increases the activity of the denitrifying heterotrophic bacteria through substrate availability,but also causes a decline in the oxygen concentration.Sedimentation of car-bon in the study area was much higher than in the open Gulf of Finland(study area34g C m–2in an 8-month study(Heiskanen&Tallberg,1999),vs. station GF2,21g C m–2in a6-month study (Leivuori&Vallius,1998)).Still,denitri?cation

was lower in the coastal area.The carbon content of the sediment was measured in May,August, October and December2003,with values decreasing from6.5%in the spring to5.5%in December.At the same time,denitri?cation tended to increase.Therefore,the absolute car-bon sedimentation and content alone could not explain the observed denitri?cation rates.Instead, a key to the denitri?cation dynamics may be the availability of carbon compounds suitable for the heterotrophic denitrifying bacteria.In the study area,most of the annual sedimenting carbon reaches the sea?oor immediately after the spring bloom,in the form of diatoms(Heiskanen& Leppa¨nen,1995;Tallberg&Heiskanen,1998). Tallberg(1999)found that68%of the spring diatoms disappeared within1month in9–12°C lake sediments.Mineralization of the diatom cells at the coastal station is most likely slower and can support benthic processes up to late summer.The increasing leucine isotope dilution factors sug-gested that there were abundant mineralization products available for the bacteria in autumn, indicating increased substrate supply for the heterotrophic denitri?cation bacteria.Why deni-tri?cation peaked in October rather than in December,when the bacterial carbon production did,may be related to the decreasing tempera-ture.

Being microbial processes,both denitri?cation and anammox are temperature-dependent,but apparently respond differently to changes in environmental temperature.In the permanently cold(<–1°C year-round)sediments of Greenland, anammox was maximal at12°C,whereas denitri-?cation exhibited maximum activity at24°C (Rysgaard et al.,2004).In the Skagerrak,where the annual temperature variation is from4°C to 6°C,the optimal temperature for anammox was 15°C and the activity decreased sharply above 25°C,whereas denitri?cation had a wider optimal range(15–32°C)and was still detectable at45°C (Dalsgaard&Thamdrup,2002).In the open Gulf of Finland the annual variation is limited to a few degrees around3°C,and the denitri?cation rates measured showed no temperature dependency (Tuominen et al.,1998).In the study area,tem-peratures ranged from near zero in spring to 6.5°C in autumn,and all the measured process rates(N2production,bacterial production and oxygen consumption)correlated positively with temperature.The denitri?cation rate doubled and anammox rate tripled from May to August,while at the same time the temperature rose from2°C to3°C.Denitri?cation nearly doubled again and anammox rate increased by30%(since lower ra levels were used in the calculations)from August to October,while the temperature doubled to 6°C.This suggests that although the increase in the rate in summer may have been related to the small increases in temperature,other factors such as carbon and O2concentration(through nitri?-cation)apparently co-limit the rates.In Decem-ber,when bacterial production and sediment oxygen consumption peaked,the N2production rates were already decreasing,as was the tem-perature.

The availability of nitrate in the bottom water had only a minor effect on the denitri?cation rate. While the uncoupled denitri?cation(Dw)was enhanced by higher nitrate concentrations,the amount of total denitri?cation was closely con-nected to the nitrate formed by nitri?cation in the sediment(Dn).Nitri?cation,in turn,is largely regulated by O2availability in the sediment,and therefore the anoxic denitri?cation process does not simply increase with decreasing O2concen-tration.In Storfja¨rden,the percentage of Dw in total denitri?cation was about5%for May, October and December,and as low as0.4%in April,but increased to10%in August when the O2concentration was low.This indicates either that the nitri?cation/denitri?cation ratio de-creased or that nitri?cation was concentrated in a shallower layer closer to the sediment surface, leading to nitrate diffusion into the water column and thereby uncoupling from denitri?cation. Unfortunately,there were no measurements of oxygen penetration in August.The surface of the sediment,however,was oxidized in all sampling seasons,as demonstrated by the light brown layer covering the darker,deeper,reduced layers.This oxidized layer was thinner,but still present,in August.We calculated the approximate oxygen penetration depth,using the oxygen consumption rate,oxygen concentration in the bottom water and oxygen diffusion coef?cient into the sediment in August;the depth was about 1.6–1.9mm,

which is half the depth measured during good oxygen conditions in the bottom water.Similarly, the Dn rates were40–50%lower than the rates in October and December when much higher O2 concentrations and consumption rates were mea-sured(Fig.2b,Table1).A direct linear relation-ship between denitri?cation and sediment oxygen demand exists in a wide variety of estuarine, freshwater and continental shelf sediments(Sei-tzinger,1987;Seitzinger&Giblin,1996).A positive correlation between oxygen consumption and Dn(but not Dw)could also be seen in the present study in the late summer–winter period. Kemp et al.(1990)found that the nitri?cation rates in Chesapeake Bay were negligible at O2 concentrations<125l M,because the sediment O2consumption exceeded O2diffusion into the sediment and restricted nitri?cation to the sedi-ment surface.In Storfja¨rden,the O2concentra-tion dropped to95l M in August,but the sediment did not become totally anoxic,because the O2consumption also decreased.Clearly the oxygen de?ciency did not totally block nitri?ca-tion at the concentrations observed,since the denitri?cation values were high in August.Previ-ous exposure to low O2concentrations or even anoxia can also cause adaptations in nitrifying communities,so that bacteria repeatedly experi-encing such conditions have higher af?nity for O2 than bacteria from permanently oxic environ-ments(Bodelier et al.,1996).This may also be the case in the Storfja¨rden area.

Spatial variation in N2production

So far,all the published denitri?cation data from the Gulf of Finland have been obtained from depositional areas.Extrapolation from these to the entire Gulf resulted in an estimate of30% removal of the annual nitrogen loading to the Gulf of Finland(Tuominen et al.,1998,this study).However,only25–35%of the Gulf of Finland bottom can be classi?ed as depositional areas(H.Kankaanpa¨a¨,Finnish Institute of Marine Research;H.Vallius,Geological Survey of Finland,https://www.wendangku.net/doc/49560234.html,m.)and thus the present estimates for the Gulf of Finland may be biassed, since no approximation of the variability between different(transport or erosion)bottoms can be given.Stockenberg&Johnstone(1997)measured denitri?cation in the Bothnian Bay in accumula-tion as well as transportation areas,?nding that the denitri?cation capacity of transportation bot-toms was only30%of that of the accumulation basins.If this is the case in the Gulf of Finland as well,the nitrogen removal via denitri?cation and anammox would only cover15–20%of the annual loading,further illustrating the discrepancy between the measured and modelled removal rates.

Anaerobic ammonium oxidation(anammox)

In the present study,the presence of anammox was explored for the?rst time in the Gulf of Finland.Anammox produced10–15%of the total N2production at the coastal station studied.The relative contribution of anammox to the overall nitrogen reduction is often minor in coastal environments with high-denitri?cation rates and increases with depth,as the rate of denitri?cation decreases(Thamdrup&Dalsgaard,2002;Risg-aard-Petersen et al.,2004a;Engstro¨m et al., 2005).Accordingly,a higher relative contribution in this study could have been expected in May, when denitri?cation was low,than in August, when denitri?cation was maximal.However,the absolute rate of anammox tripled from May to August,while the denitri?cation rate doubled.A concomitant increase of1°C(from2°C to3°C)at these low temperatures may have had a larger effect on anammox than on denitri?cation (Dalsgaard&Thamdrup,2002,Rysgaard et al., 2004),causing an increase in the relative percent-age of anammox from10%to15%of the total N2 production.A trend similar to the one observed here—increase in importance of anammox with increasing overall activity—was described in the Thames Estuary(Trimmer et al.,2003)and in subtropical mangrove sediments in Australia (Meyer et al.,2005).In the Thames Estuary, anammox was positively correlated with the organic carbon content,whereas in the subtrop-ical mangrove sediments,nitrite and nitrate availability regulated anammox https://www.wendangku.net/doc/49560234.html,anic carbon may control the autotrophic anammox community in the Thames Estuary by enhancing heterotrophic denitri?cation,which in turn

produces nitrite for the anammox bacteria(Trim-mer et al.,2003).At low nitrate concentration (below10l M),not only the relative contribution but also the absolute rate of anammox diminishes, probably as a consequence of competition for substrate with heterotrophic nitrate and nitrite reducers(Trimmer et al.,2005).In the present study the concentrations of combined nitrate and nitrite were most of the year below2l M and never exceeded3l M,which supports the?ndings of low anammox activities in the area.

Two methods are currently used to estimate the contribution of anammox to the total N2produc-tion in sediments where both processes exist.The site-speci?c,intact core method(r-IPT,Risgaard-Petersen et al.,2003,2004b)used in this study gives the best estimates of anammox and denitri-?cation activity because it does not call for destruction of the natural strati?cation in the sediment.It also measures the activity of the entire sediment core instead of a selected layer. However,it requires minimal sediment heteroge-neity,because high scatter in the raw data can mask signi?cant differences in rates(Trimmer et al.,2006).The slurry incubations method (Thamdrup&Dalsgaard,2002)is based on collection of the active surface/subsurface layer of sediment for anoxic incubation with different combinations of labelled and unlabelled nitrogen compounds(NO2–,NO3–,NH4+).The method breaks the chemical strati?cation of the sediment, and the processes are not necessarily measured in the layer in which they are most active.Therefore, it is prone to giving underestimates of the processes(Trimmer et al.,2006.)At the coastal station studied here,the macrofauna was limited to a few small Macoma baltica mussels.These were found occasionally(not even daily)in the samples,and the results from these samples were always omitted from the calculations.Therefore the intact core method probably gave a reliable approximation of the N2production in the study area.The calculated contribution of10–15% caused a dramatic80–150%overestimate in the N2production when the classical IPT was used, due to the high15NO3–incubation concentration used.This indicates a need to verify the measure-ments performed earlier in the Gulf of Finland using the IPT and high15NO3–concentrations,since no data are yet available on the bias anammox may have caused in the denitri?cation estimates.

Conclusions

Coastal denitri?cation,measured here for the ?rst time in the northern Baltic Sea,is of similar magnitude as denitri?cation in the open Baltic Sea depositonal areas.It follows a clear seasonal cycle of low rates in early spring,high rates from late summer to late autumn and diminishing rates again in winter.This variation is strongly related to temperature and mineralization of the sedi-mented spring diatom bloom,the main carbon source to the sediment in the basin studied. Anammox was explored for the?rst time in the Gulf of Finland.It was measured in spring and autumn and contributed less than10%to the total N2production.The low percentage did,however, cause a signi?cant error in the total N2production rate estimate,calculated using the classical IPT. Therefore we recommend that anammox be taken into account in future research in Gulf of Finland sediment nitrogen cycling.Since no data on the seasonal and spatial variability of anam-mox rates from the Gulf of Finland are yet available,the true N2production rates cannot be reliably estimated.Both N budgets and models, however,indicate that some70,000–86,000t N are removed from the Gulf of Finland annually (Perttila¨et al.,1995;Savchuk,2005;Kiirikki et al.,2006).The N2production rates measured in this project release39,100t N annually,leaving 30,900–46,900t N to be removed by other pro-cesses,or by more ef?cient N2production in some areas.Since some of the highest N2production values have been measured from coastal and river estuarine basins(Silvennoinen et al.,2007),these seem likely places to begin looking for the ‘‘mysteriously disappearing nitrogen’’.The high spatial and temporal variability in the sediment processes,caused by heterogeneity in the bottom topography,?ow rates,environmental conditions and interannual changes in these,leave room for speculation.Clearly,there are still large gaps in our understanding of the nitrogen dynamics of the Gulf of Finland.

Acknowledgements We thank S.Hauta-aho(University of Helsinki)warmly for the oxygen consumption data.This study was funded by the Academy of Finland BIREME programme,and conducted through the SEGUE Consortium.

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期货基本分析方法

期货基本分析方法 期货基本分析方法 本分析法是根据商品的产量、消费量和库存量(或者供需缺口)，即通过分析期货商品的供求状况及其影响因素，来解释和预测期货 价格变化趋势的方法。基本面分析主要分析的是期货市场的中长期 价格走势，即所谓大势，并以此为依据中长期持有合约，不太注意 日常价格的反复波动而频繁地改变持仓方向。 期货基本分析方法之供给分析 供给是指在一定时间、一定地点和某一价格水平下，生产者或卖者愿意并可能提供的某种商品或劳务的数量。决定一种商品供给的 主要因素有：该商品的价格、生产技术水平、其他商品的价格水平、生产成本、市场预期等等。 商品市场的供给量则主要由期初库存量、本期产量和本期进口量三部分构成。 1、期初库存量 期初库存量是指上年度或上季度积存下来可供社会继续消费的商品实物量。根据存货所有者身份的不同，可以分为生产供应者存货、经营商存货和政府储备。前两种存货可根据价格变化随时上市供给，可视为市场商品可供量的实际组成部分。而政府储备的目的在于为 全社会整体利益而储备，不会因一般的价格变动而轻易投放市场。 但当市场供给出现严重短缺，价格猛涨时，政府可能动用它来平抑 物价，则将对市场供给产生重要影响。 2、本期产量 本期产量是指本年度或本季度的商品生产量。它是市场商品供给量的主体，其影响因素也甚为复杂。从短期看，它主要受生产能力

的制约，资源和自然条件、生产成本及政府政策的影响。不同商品 生产量的影响因素可能相差很大，必须对具体商品生产量的影响因 素进行具体的分析，以便能较为准确地把握其可能的变动。 3、本期进口量 本期进口量是对国内生产量的补充，通常会随着国内市场供求平衡状况的变化而变化。同时，进口量还会受到国际国内市场价格差、汇率、国家进出口政策以及国际政治因素的影响而变化。 期货基本分析方法具体内容 供求关系。期货交易是市抄济的产物，因此，它的价格变化受市场供求关系的影响。当供大于求，价格下跌;反之，价格就上升。反 映供给的变量有前期库存量、当期生产量和当期进口量三部分组成; 反应需求的变量有国内消费量、出口量及期末商品结存量三个部分 组成。 经济周期。在期货市场上，价格变动还受经济周期的影响，在经济周期的各个阶段，都会出现随之波动的价格上涨和下跌现象。 政府政策。各国政府制定的某些政策和措施会对期货价格带来不同程度的影响。 政治因素。期货市场对政治气候的变化非常敏感，各种政治性事件的发生常常对价格造成不同程度的影响。 社会因素。社会因素指公众的观念、社会心理趋势、传播媒介的信息影响。 季节性因素。许多期货商品，尤其是农产品有明显的季节性，价格亦随季节变化而波动。 心理因素。所谓心理因素，就是交易者对市场的信心程度，人称“人气”。如对某商品看好时，即使无任何利好因素，该商品价格 也会上涨;而当看淡时，无任何利淡消息，价格也会下跌。又如一些 大投机商品们还经常利用人们的心理因素，散布某些消息，并人为 地进行投机性的大量抛售或补进，谋取投机利润。

第章季节性施工方案及措施

第十章季节性施工方案及措施 第一节雨季施工方案 一、雨季施工准备 1.组织准备 1）成立以项目经理为第一责任人的领导小组，将方案编制、措施落实到人。料具供应、应急抢险等具体职责落实到部门，并明确责任人。 2）雨季施工主要以预防为主，采取防雨措施及加强排水手段，确保雨季时生产的正常进行，不受季节气候影响。 3）做好施工人员的雨季施工培训工作，组织相关人员进行施工现场的准备工作，并进行一次全面的施工现场的检查，包括检查临时设施、临时用水管道，临时用电，机械设备等各项工作。 4）加强雨季施工的信息反馈，对容易发生问题的要采取防范措施，设法排除隐患，同时合理的安排日常工作。 2.技术准备 1）资料准备 ①收集定安气象资料，了解雨期天气状况。 ②认真熟悉施工图纸，了解进入雨施的各单位工程设计状况及施工特点，提出针对性的雨期施工技术措施。对进入雨期施工但不适于雨施的项目及时与业主及设计院联系，共同研究解决。 ③收集同类工程雨季施工经验，选择合理的针对性的雨季施工措施。 2）雨期施工方案编制 我公司项目部将在开工前，编制并审批完成该工程更为详细的雨期施工方案，同时报业主或监理批准。该方案将根据具体施工图、实际工程进度及施工状况编制完成，提出切实可行的雨期施工技术措施。 3.技术交底 项目部将严格执行技术交底制度，将雨期各项技术要求从管理人员到分包及个人进行层层分级技术交底。 项目部各现场管理人员将对其责任范围内具体负责的工程项目向具体分包负责人或班组长进行具体技术交底。交底内容主要为针对性的具体施工工艺、操作要点、质量要求等内容。 项目部同时将严格监督检查班组对工人的现场及班前交底情况。 4.施工现场准备

农产品季节性与期货

如何分析农产品期货的季节性行情 农产品的共性就是具有固定的一年一度的播种、生长和收获季节性周期，也恰恰是农产品这种特有的季节性供求关系变化使得其价格波动在每年的一些特定时期内同向运动的趋势性十分明显。一般来说，我们可以根据这种季节性特征把农产品走势大体分为：播种生长阶段、收获季节、销售淡季和销售旺季等几个不同阶段。又因为期货价格是现货价格的指引，它们的基本面影响因素是一致的，走势基本是联动的，因此，下面我们以几个品种为例，从季节性影响因素这个角度分别对其期货价格走势进行对比分析： 首先拿大豆品种来说，根据自然规律从每年的4月开始，北半球的大豆主产国开始播种，当年9月份开始收割。从10月份开始，南半球的大豆主产国又开始播种，次年4、5月份收割。从这一种植生长周期可以总结出，每年的7、8月份属于全球大豆的供应淡季，大豆青黄不接，消费需求旺盛，因此价格多是高企；而每年的11月份左右是全球大豆的供应旺季，现货供应充足，价格多处年内低谷，这一规律从上图CBOT大豆行情长期走势中不难得到验证。 仔细观察以上CBOT和DCE大豆近年来季节性走势图，首先我们可发现，国内外大豆价格的相关性很强，纠其原因主要是：2000年以来人们膳食结构的调整使得我国大豆需求激增，国产大豆远远不能满足市场的消费。加之进口大豆出油率高，使得进口大豆数量出现大幅增长，导致国内外大豆价格走势联动性增强；其次，我们还可以发现：2000年至今，每年因季节性而形成的的阶段性高点多出现在5月-8月，主要是因为每年3-5月是销售旺季，而7、8月份又是供应淡季，这样高点出现在这期间就不足为奇；9-11月份进入大豆收获季节，受供应压力影响价格多处年内低点，产量确定后，随着消费的增加，库存的减少，价格有开始抬头趋涨。不过，每年二月份多是过节时期，市场交投清淡，谷物价格通常盘跌。这些规律都很好验证了大豆价格的季节性波动趋势。目前正处于8月份，正是供应淡季，又由于目前国内大豆主产区黑龙江省严重干旱，国内大豆减产基本定局，而美国大豆产区近期天气也是十分炎热干燥，大豆天气行情再度显现，在大豆收获季节来临前，有望走出一波上涨行情。因此依据这一特点可以估计在9--11月份供应压力前大豆可能会形成一个短期高点。 接着再看玉米品种，玉米与大豆的生长周期相差无几，从上图可发现玉米最明显的特征是仲夏到收获期间价格多是走跌。由于新年度玉米产量不确定性的影响，7月份的价格往往达到年内最高价格。即使在7月份中期之前价格开始跌落的年份，如果收获前景可观，价格仍可持续走低。每年10月正值收获季节，由于大量玉米集中上市，市场供应压力最大，价格往往会跌到一年中的最低水平。而后随着时间的推移和持续不断的消费，玉米库存量也越来越少，而价格也随着变化。农业部前期发布的《农业生物质能产业发展规划（2007~2015年）》（以下称《规划》），提出今后一个时期，我国农业生物质能产业要按照大力发展农村沼气，积极发展农作物秸秆固化成型和气化燃料，适度发展能源作物的发展战略，因地制宜地确定发展重点和产业布局。这对前期国内利用玉米发展燃料乙醇的炒做泼了一盆冷水，玉米期价也因此从1700元/吨上方连续回落至1500元/吨以下。由于过渡打压后，近期的东北农作物用地发生干旱灾害，导致玉米期价产生了"反季节"的上涨行情，但于8月10日将有"吉林省2007年轮换地方储备粮竞价销售交易会"，届时将销售轮出省级储备玉米10万吨，这对于玉米期价将是一个压力。在供应季节来临前玉米产生大幅度反弹的行情较小，上涨空间有限。 最后转到国内外小麦品种上，以北半球冬小麦为例，其播种时间为10月上旬（寒露后）至下旬，收获期在5月下旬至6月初。小麦有两个明显的季节倾向：其中之一就是冬末到收获季节来临之前的春季这一时期惯于下跌。多数年景，小麦价格在1、2月份因资金回拢影响都会经历季节性疲弱期。又因每年冬麦上市后的7月份一般为小麦的供应旺季，价格多处年内最低点；另一个趋势就是从收获季节的低点到秋季或者冬初小麦消费逐渐进入旺季，价

季节性施工措施及特殊时期施工保证措施

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季节性时间序列分析方 法 LG GROUP system office room 【LGA16H-LGYY-LGUA8Q8-LGA162】

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目录 第一节雨季施工技术措施 (2) 第二节冬季施工技术措施 (2) 第三节夏季施工 (3) 第四节防风措施 (4)

第一节雨季施工技术措施 武汉地区经常阴雨绵绵，给本工程的施工带来很大的困难。为了确保工程的顺利进行，特提出如下雨季施工措施： 1、密切注意天气变化，避免雨天浇筑混凝土，如施工中遇大雨立即停止混凝土的浇筑，并及时对施工完的混凝土进行草包覆盖保护。 2、采用硬地施工，即施工现场临时道路采用150mm厚砼浇筑，这既给雨季施工带来很大的便利，给工人提供了良好的工作环境，又防止了尘土、泥浆被带到场外，保护了周围环境加强了现场文明施工。 3.雨季施工期间混凝土搅拌站要随时测定砂、石含水率，及时调整混凝土的配合比，严格控制水灰比。 4.现场室外使用的中大型机械必须按规定加设防雨罩或防雨棚，闸箱防雨，漏电接地保护装置应灵敏有效，定期检查线路的绝缘情况。 5.大风天气要做好大型高耸物件(塔吊、附墙吊)的防风加固措施，风力达到或超过6级塔吊禁止使用。 6. 现场临时尽量少备用灰料，如必须备用，则须做好如下防潮工作：下铺木板和两层彩条布，要求石灰袋下部离开地面的架空高度不小于500mm，石灰堆上铺一道彩条布，雨季增加一道。 7. 做好现场排水系统，将地面雨水及时排出场外。 第二节冬季施工技术措施 武汉地区的冬季为12、1、2月，尽管常年冬季气温不太高，冬季持续时间不长，但近年来冬季气温多呈反常现象，为保证工程能在冬季期间正常进行，采取如下措施： 1.确定冬季混凝土施工配合比，并按要求掺加抗冻剂，以提高混凝土的抗

冻性。搅拌站有可靠的冬季施工保证措施，能确保混凝土冬季施工的要求。 2.保证混凝土受冻前达到临界强度，拆模时，混凝土强度必须达到4Mpa,拆除时间以现场同条件试块抗压强度为准。 3.适当延长养护时间，砼达到足够强度后再拆模。 4.控制混凝土拌合物的出机温度，保证混凝土的入模温度不低于5 C。以防混凝土在输送过程中受冻或温度过快降低。搅拌砂浆材料中不得有冰冻块物，气候有冰冻现象时，材料利用塑料薄膜和草包覆盖。 5．混凝土在浇筑前，应清除模板和钢筋上的冰雪，采用地泵浇筑时，混凝土泵管外包保温被(层)。 6．建立冬季施工测温制度。在混凝土浇筑时按要求布置测温孔、并编号，按冬季施工要求进行测温工作。测温工作派专人负责，在混凝土强度未达到3.5N/mm2以前每2h测一次，以后每6h测一次。所有各项测量及检验结果，均应填写“混凝土施工记录”和“混凝土冬期施工日记”。 7．负温条件下焊接钢筋时，应根据当时气温条件，搭设挡风设施和适当延长保温时间。雨大禁止焊接工作。 第三节夏季施工 在夏季施工中，除严格遵守国家现行的施工规范及规程外，为保证施工质量特制定以下措施： 1．高温天气施工混凝土时，采取降温措施，保证混凝土入模时的温度。 2．高温天气施工的混凝土、砂浆，应注意测温，加强降温、养护工作。 3.对砼、砂浆面加强养护，用草袋加水覆盖。