Phosphorus fractionation in volcanic lake sediments (Azores – Portugal)
Phosphorus fractionation in volcanic lake sediments (Azores –Portugal)
D.C.Ribeiro a ,G.Martins a ,R.Nogueira a ,J.V.Cruz b ,A.G.Brito
a,*
a
Institute for Biotechnology and Bioengineering,Centre for Biological Engineering –University of Minho,DEB,
Campus de Gualtar 4700-057Braga,Portugal
b
Geosciences Department –University of Azores (currently at Regional Department of Water Resources and Land Planning),Portugal
Received 6March 2007;received in revised form 19July 2007;accepted 26July 2007
Available online 14September 2007
Abstract
The phosphorus distribution in volcanic sediments of three lakes that are under di?erent anthropogenic pressures in Sa ?o Miguel island (Azores –Portugal)was evaluated using a sequential extraction scheme.The P-fractionation scheme employs sequential extractions of sediment with NH 4Cl,bicarbonate-dithionite (BD),NaOH (at room temperature),HCl and NaOH (at 85°C)to obtain ?ve P-fractions.The P-fractionation shows that in lakes with higher trophic status (Lake Furnas and Lake Sete Cidades),the NaOH extracted P is the dominant fraction,that contribute with more than 50%to total sedimentary phosphorus.The rank order of P-fractionation for these two lakes was NaOH >NaOH (85°C)>HCl >BD >NH 4Cl for Furnas lake and NaOH >HCl >NaOH (85°C)>NH 4Cl >BD for Sete Cidades lake.On the other hand,the trend of P contribution in the oligotrophic lake Fogo shows that the most inert P pools have the higher concentrations,with more than 50%of the P contribution from the last extraction step with NaOH at 85°C.For this lake,the rank order of P-fractionation was NH 4Cl >BD >NaOH >HCl >NaOH (85°C).The Phosphorus Maximum Solubilization Potential (P-MSP)was also calculated and the results show that for the more bio-available P-fractions (?rst and second extraction step),the P-MSP values for Furnas and Sete Cidades lakes are sensibly higher than the results obtained in Fogo lake,an indication of the non-point di?use load discharged in the ?rst ones.ó2007Elsevier Ltd.All rights reserved.
Keywords:Eutrophication;Phosphorus extraction;Sediment;Volcanic lakes
1.Introduction
Biological productivity in lakes is strongly related to the concentration of phosphorus (P)in the water column.It has been shown that the sediment of the lakes can act as an inter-nal source of phosphorus for the overlying water (Lijklema et al.,1993;Ramm and Scheps,1997;Zhou et al.,2001).This is especially important when the external nutrient sources are controlled.In this context,many studies in the past years have been made to understand the factors that a?ect the P release from the sediments.Temperature,redox reactions,pH,dissolved oxygen concentration,nitrate,sul-fates and bacterial activity are pointed as the major control-ling factors (Kim et al.,2003;Jin et al.,2006).
Phosphorus is present in sediments in several chemical forms (Gonsiorczyk et al.,1998).Thus,prediction of future internal P-loading requires more than the knowledge on the total concentration of phosphorus.Soil P-fractionation has been investigated since 1957and later applied to lake sediments to overcome the limited information that total-P analysis can provide (Zhou et al.,2001).Since then,sev-eral procedures for phosphorus extraction in sediments have been proposed in order to suit studies of di?erent sed-iment mineral phases.(Psenner and Pucsko,1988;Rutten-berg,1992;Ruban et al.,1999).These sequential extraction schemes made possible,in several studies,to characterize the diverse forms in which P is distributed in sediments,classi?ed as labile P,reductant P,metal bound P,occluded P and organic P (Psenner and Pucsko,1988).These frac-tions have been also classi?ed as water soluble P,readily desorbable P,algal available P or ecologically important P (Pettersson et al.,1988;Zhou et al.,2001).
0045-6535/$-see front matter ó2007Elsevier Ltd.All rights reserved.doi:10.1016/j.chemosphere.2007.07.064
*
Corresponding author.Tel.:+351253604400;fax:+351253678986.E-mail address:agbrito@deb.uminho.pt (A.G.Brito).
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Chemosphere 70(2008)
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The aim of this research is to de?ne P speciation and pro-?le in the sediments of three lakes,in Sa ?o Miguel,as a tool for understanding the potential mobility of P from sediments to the overlaying water and corresponds to the ?rst study to apply phosphorus speciation to characterize in these lake sediments.In the present study we used a modi?ed Psenner sheme (Psenner and Pucsko,1988),as already proposed by
Romero-Gonza
′lez (Romero-Gonzalez et al.,2001).This procedure allows the partial separation of P iron-bond frac-tion from aluminum and calcium-bond fraction.2.Material and methods 2.1.Study site
The three studied lakes are located in the island of Sa ?o Miguel which belongs to the archipelago of Azores (Portu-gal),located between the parallels 36°450–39°430of lat-itude North and meridians 24°450–31°170of longitude West (Fig.1).The eutrophic shallow lake Furnas is located in East side of the island.The Sete Cidades lake is located in the Western part of Sa ?o Miguel and it is composed by two interconnected lakes,the so-called Azul and Verde lakes.The Azul lake is at meso-eutrophic state but the Verde lake is already classi?ed as eutrophic.The third stud-ied lake is Fogo,an oligo-mesotrophic lake,located in the central part of the island.The morphometric and geochem-ical characteristics of the lakes are presented in Table 1.The three studied lakes are in the bottom of large calde-ras,located in the three volcanic centers that dominated Sa ?o Miguel geology.These centers correspond to the major active trachytic central volcanoes of Fogo,Sete Cidades and Furnas,linked by rift zones.During the last 5000years the activity of these three active central volcanoes is shown by 57volcanic eruptions,with an output of 4.6km 3of dense rock (Booth et al.,1978).For the whole island of Sa ?o Miguel it is possible to estimate an overall erupted vol-ume of 400km 3in the past four million years,at an average volume of at least 0.01km 3per century.The majority of these eruptions presented were explosive,resulting in pum-ice deposits,of acid character,that cover the volcanoes ?anks.Therefore,in the bottom of the lakes it is expected that sediments present a close relation with these pumice
deposits.Thus the granulometry analysis shown that the ?ner fraction (silt and clay)is dominant and it corresponds to 98%of the sediment composition,of which silt is the main class.Sa ?o Miguel Island is also called ‘‘The Green Island’’which de?nitely is its dominant colour,due to the fact that the area is occupied by highly fertilized grass ?elds crossed by small rivers of not constant ?ow.Their ?ows depend mostly on the rainfall which is often very intense leading to signi?cant soil erosion and to the discharge of nutrients from the grass ?elds into the lakes.
Besides the nutrient input due to agriculture,secondary manifestations of active volcanism may also contribute to water composition in these studied lakes,through seepage of thermal waters or gaseous compounds.At the
fumaroles
Fig.1.Location of the studied lakes in S.Miguel Island.
Table 1
Physical and Chemical properties of the studied lakes
Lake Furnas
Lake Sete Cidades Lake Fogo
Physical description b Surface Area (km 2) 1.9 4.35 1.48Max.Depth (m)12
33
30
Volume (m 3)92125004776050018040800Volcanic setting
Caldera Caldera Caldera Chemical and trophic parameters a pH b 7.36
7.46 6.68EC (l S cm à1)b
142.78
113.6747.50HCO 3(mg l à1)
b
49.0128.28 6.20Ca (mg l à1)b 2.88
1.430.48Mg (mg l à1)b
2.27
1.320.80Dissolved CO 2(mg l à1)b
10.33
5.98 2.97NO à
3(mg l à1)
1.04 1.330.42SO 2à
4
(mg l à1)22.710.212.1Soluble reactive phosphorus (l g P l à1)c
11
3–Total phosphorus (l g l à1)
c 45
21–Chla (mg m à3)c 17.85
10.43 2.73Secchi disc transparency
(m)c
0.8 2.3–
Trophic classi?cation Hypertrophic
Meso-Eutrophic
Oligotrophic
a Variation can occur by seasonal changes.
b Data from Cruz and Fran
c ?a (2006).
c
Data from water monitoring network from regional government.
D.C.Ribeiro et al./Chemosphere 70(2008)1256–12631257
?eld located in the north margin of Furnas lake the dis-charge of boiling SO4-rich waters occurs convicted to a steam-heating mechanism(Cruz and Franc?a,2006)and in the?eld surface runo?to the lake is observable.There-fore it is not excluded that these steam-heated waters are a supplementary SO4source into the lake.
2.2.Water/sediment sampling and analysis
One sediment sample was collected in February2006,at the deepest locations of each of the three lakes.For the Sete Cidades Lake,the core was made in the deepest site of the Verde lake.A gravitational Uwitec-corer was used,which enabled collecting undisturbed sediment cores,in the soft sediments of the studied lakes.The Uwitec-corer tubes, with a diameter of60mm,and600mm length,had pene-trated about220–440mm in the sediments,and collected also the overlaying water.The sediment samples with the water were sealed in situ,in the core tubes.After a very del-icate transportation into the laboratory,the water from the sampling core tubes was recovered,sealed in glass?asks and preserved at4°C until the analysis.The sediment of each core tube was cut in?ve slices with an Uwitec Mechanical cutting apparatus.Each slice was homoge-nized,dried at105°C,sealed and conserved frozen in plastic Petri dishes,until the analysis.
2.2.1.Water analysis
The analyzed chemical parameters of the water were
phosphateePO3à
4T,nitrateeNOà
3
T,and sulfateeSO2à
4
T,after
?ltration with a0.45l m membrane.Phosphate was ana-lyzed by spectrophotometric method by the molybdenum blue/stannous chloride method,nitrate by ultraviolet spec-trophotometric screening method,and sulfate by turbidi-metric method(APHA et al.,1995).
2.2.2.Phosphorus fractionation
The phosphorus fractionation method used in the pres-ent work was the Psenner and Pucsko(1988)scheme,with minor modi?cations.This extraction method draws the conclusion on the P-binding forms in the sediments (Table2),and is also useful to predict bioavailability of P.
After each extraction step,samples were centrifuged at 7000rpm,for20min.,and the supernatant was?ltrated through a0.45l m membrane.The analysis of SRP was made by molybdenum blue/stannous chloride method (APHA et al.,1995).The total-P(TP)analysis was achieved by an acid digestion of the samples,with nitric and sulfuric acids at250°C,and further analyzed as a SRP sample.The NRP fraction is de?ned as the di?erence between TP and SRP.With this extraction procedure,as shown in Table2, phosphorus is fractionated in labile P(NH4Cl),redox-sensi-tive P(bicarbonate-dithionite),metal oxide bound P (NaOH-SRP),organically bound P(NaOH-NRP),Ca-bound P(HCl),refractory/residual P(hot NaOH).
2.3.Phosphorus maximum solubilization potential
(P-MSP):de?nition and presumptions
We de?ne phosphorus Maximum solubilization potential (P-MSP)as a hypothetical concentration of phosphorus in the water column,in the case of total dissolution of the P present in the sediments,for each chemical form.Natu-rally,this hypothetical event is extremely improbable,as it depends on many complex chemical and biological pro-cesses.However,the purpose of this calculation is to esti-mate the maximum input limit of P from the sediments to the overlaying water.
This theoretical parameter is calculated from the results of P concentration obtained by the sequential extraction procedure applied in the sediments of the studied lakes. For this evaluation,several presumptions have been assumed:
–All the sediment area of the lake has the same environ-mental conditions as well as the same phosphorus chem-ical forms concentration.
–A water and sediment control volume is de?ned and all the lakes’water body and sediments have the same phys-ical and chemical behavior of the respective control volumes.
Table2
Extraction procedure used in the present work,adapted from Psenner and Pucsko(1988)extraction scheme(SRP–Soluble Reactive Phosphorus; NRP–Non Reactive Phosphorus;TP–Total Phosphorus)
Step Solvent P-Fraction P bounding forms
1NH4Cl SRP Loosely bound P:Pore water soluble phosphate and sediment surface loosely adsorbed
phosphate,algal available phosphate
2BD(0.11M)(Bicarbonate–
Dithionite)40°C SRP Reductant soluble P:Redox-sensitive P,mainly bound to Fe-hydroxide and Mn-hydroxide NRP Redox-sensitive organic P
3NaOH(1M)(Sodium
Hydroxide)40°C SRP Metallic oxide bound P:Phosphate bound to metallic oxide(mainly Fe and Al),soluble inorganic P compounds in alkaline solution
NRP P in micro-organisms,detritus,humic compounds,poly-P,P-lipid
4HCl(0.5M)(Hydrochloric acid)SRP Apatite and CaCO3bound P
NRP Organic P sensible to acid
5NaOH(1M)85°C TP Organic refractory P
1258 D.C.Ribeiro et al./Chemosphere70(2008)1256–1263
–Only vertical di?usion of P is considered and the water col-umn is homogeneous(no thermal or chemical gradients).–The sediment control volume is homogeneous with a mean concentration value for each the P forms,calculated by the results obtained in the P-fractionation procedure.
Only the values at approximately50mm depth have been used for the determination of the mean P concentra-tion in the sediments.
The control volumes for each sediment and water col-umn have the same area,which is the one made by the corer in the sediments.Therefore,the control volume V c i for each sediment(i=sed)or water column(i=wat)is cylindrical,with a circular base area(A).The length of the cylindrical control volume for the sediments(h)consid-ered was50mm.This means that,for all this50mm length control volume,the sediment is homogeneous and has P concentration equal to the mean value calculated from the results of P-fractionation.For the water body,the length of the control volume(H)depends on the length of the deepest location of the lake(Table1).The Eqs.(1) and(2)shows the calculation of the control volume for the sediments and water column.
Vc sed?A?h?p
4
d2?he1T
Vc wat?A?H?p
4
d2?He2T
The density(q sed)and porosity(/)of the sediments are 2.439kg là1and0.90,respectively.The control volume of the sediments(V c sed)is the sum of the sediments volume (V sed)and volume occupied by the interstitial water(V w sed) present in the sediments(Eq.(3)).With the combination of Eqs.(3)and(4)we can obtain the sediments volume(Eq.(5)). V sed?Vc sedàVw sed()Vw sed?Vc sedàV sede3T
/?Vw sed
Vc sed
e4T
V sed?Vc sedáe1à/Te5TThe exact sediment mass(m sed)can be calculated by multiplying the sediment volume and the sediment density, as demonstrated by the Eq.(6).With the results of P con-centration in the sediments(C P,sed)obtained in the applied sequential extraction procedure and with the calculated sediment volume,we can determine the P mass present in the sediment(m P,sed),for each P chemical forms(Eq.(7)).m sed?q sedá
p
4
ád2áháe1à/Te6Tm P;sed?C P;sedám sede7TP-MSP?
m P;sed
Vc wat
?
C P;sedám sed
pád2áH
P-MSP?
C P;sedáq sedáp
4
ád2áháe1à/T
p
4
ád2áH
P-MSP?
C P;sedáq sedáháe1à/T
H
e8TThe concentration of P in the water control volume,if hypo-thetically all the P mass from the sediment control volume would dissolve into it,is given by the Eq.(8),and represents the P-MSP theoretical parameter.The results of P-MSP for each lake and P forms are presented in Table3.
3.Results
3.1.Water at the interface
Despite the fact that several chemical parameters were analyzed,the most important in the present work is the phosphate analysis.As so,the results for the water analysis will focus only in the soluble phosphate concentration.
The SRP concentration in the sediments’overlaying water for Fogo,Furnas and Sete Cidades core site was 24,17and47l g P là1,respectively.The highest SRP con-centration is found in Sete Cidades lake.In contrast of what would be expected,hypereutrophic lake Furnas has the lowest concentration of https://www.wendangku.net/doc/d0734900.html,ke Fogo has a slightly higher concentration than Lake Furnas,although Fogo is at lower trophic status.
3.2.Sediment
Although TP analyses for each step were performed,in the present work only SRP analysis results will be showed and further discussed.The main reason is that this work is specially focused in a geochemical approach.Therefore, these results are the most accurate for the assessment of bioavailability of P,in a chemical point-of-view.Further work in a more biological approach will be made,and NRP pool(which is mainly organic P)will be considered, as well as speci?c biological processes of degradation. The results are next presented for each lake.
https://www.wendangku.net/doc/d0734900.html,ke Fogo
The mean value of the sum of SRP concentration,for all extraction steps(and depth)is86l g P gà1dw.However,
Table3
Values of P-MSP for each lake and P extracted form(in brackets are the standard deviation values)
l g P là1
NH4Cl-SRP BD-SRP NaOH-SRP45°C HCl-SRP NaOH-SRP85°C Fogo 1.0(±0.2) 2.2(±0.9)8.6(±5.6)9.2(±1.6)19.5(±3.6) Furnas 5.9(±1.0)11.7(±0.0)181.8(±6.3)44.3(±6.1)81.2(±18.0)
Sete Cidades12.6(±6.7) 5.5(±1.3)37.6(±5.5)11.3(±1.8)9.0(±0.2)
D.C.Ribeiro et al./Chemosphere70(2008)1256–12631259
the distribution of P in sediments is not linear,as the higher amount of SRP is located in the?rst50mm of the studied sediment core(Fig.2).
For all the samples,the major part of the phosphorus has been extracted in step5,with NaOH at85°C.The most bio-available P,which is extracted in the?st step (NH4Cl-P),is present at low concentration in the sediment of this lake(2l g P gà1dw).
The P bound to Fe-hydroxide and Mn-hydroxide(BD-extraction step)is also in low concentration(4l g P gà1 dw),in comparison with the other extraction steps.Results also demonstrate that in loosely bound P and redox-sensi-tive P(extracted in the?rst two steps),SRP is more concen-trated at the upper part of the sediment,decreasing with depth.
https://www.wendangku.net/doc/d0734900.html,ke furnas
In Furnas Lake,the mean SRP concentration in the analyzed samples is325l g P gà1dw,which is almost four times higher comparing to Lake Fogo.In this case,the most extracted P was veri?ed in the third step(NaOH). The?fth step,also performed with NaOH(at85°C), highly contribute to the sedimentary phosphorus(54.2%).Thus,both extractions with NaOH which extracts the P bound to oxide metals(mainly Fe and Al)and organic P compounds have major contribution(80.9%)in the sedi-ments from this lake(Fig.3).
The loosely bound P is almost constant along the core, and has a relatively low concentration(6l g P là1).The BD-P concentration reaches his maximum in the middle of the sediment core,but still in relatively low concentra-tion(12l g P là1).The HCl-P contribution shows it to be more or less constant along the analyzed core.
https://www.wendangku.net/doc/d0734900.html,ke Sete Cidades(Verde Lake)
The sediment P-fractionation of the Verde lake,shows that the extraction step that most contributed to P concen-tration was the cold NaOH extraction(third step).The loosely bound P-fraction has higher concentrations in the upper sediment zone(interface zone),as shown in Fig.4. The P contribution by the NH4Cl,HCl and hot NaOH extraction steps is similar(Fig.5).
The mean concentration of SRP of the sum of all extrac-tions(for all samples),is228l g P gà1dw in this lake.The higher SRP concentration is observable in195–210mm depth interval(262l g P gà1dw–Fig.4
).
Fig.2.Phosphorus fractionation in sediments from Lake
Fogo.
Fig.3.Phosphorus fractionation in sediments from Lake Furnas.
1260 D.C.Ribeiro et al./Chemosphere70(2008)1256–1263
3.3.Phosphorus maximum solubilization potential
The P-MSP results are demonstrated in Table 3with the maximum values for each lake in bold type and the stan-dard deviation in brackets.Fogo lake has the higher P potential in the ?fth extraction step (NaOH at 85°C)while Furnas and Sete Cidades lake show to have the P higher potential in the third one (NaOH).4.Discussion
4.1.Loosely adsorbed phosphorus (NH 4Cl-P)
The immediately available P in sediments corresponds mostly to soluble inorganic P,which is mainly orthophos-phate.Therefore,the loosely adsorbed P (also called water soluble phosphorus –WSP)is the best parameter for assessment of bioavailability of P (Zhou et al.,2001).Ana-lytical results suggest that NH4Cl-P concentration in Sete Cidades lake is between 59and 13l g P g à1dw,with the higher values in the upper sediment layers.In comparison with the other two lakes,Sete Cidades has the higher con-
centration value of NH4Cl-P.This means that loosely adsorbed P will be easily available to algae,promoting con-sequent blooms.The SRP concentration in the sediment’s overlaying water is also higher in Lake Sete Cidades.A comparison between the Fogo and Furnas lake in terms of NH4Cl-P extraction shows that Furnas has concentra-tions 2.3–5.4times higher than Fogo.The decrease of the NH4Cl-P concentration with depth,for the three lakes,might be explained by the decrease of pH with depth,which enhance desorption of P (Gonsiorczyk et al.,1998).4.2.Reductant soluble phosphorus (BD-P)
The reductant SRP is assumed to be bound to Fe-hydrox-ide and Mn compounds.For all the studied lakes,this form of P is present in relatively low concentrations (Fig.5).For Lake Sete Cidades reductant P is the smallest contributor for the total amount of SRP.Nevertheless,when the hypo-limnium is in reductive state,due to low oxygen concentra-tion,this P-metal hydroxide bound might be released.However,the widely accepted hypothesis of phosphate release from anoxic sediments due to Fe(OOH)-P
complex
Fig.4.Phosphorus fractionation in sediments from Lake Sete
Cidades.
Fig.5.Relative contribution of each extraction step to sedimentary phosphorus (mean values and standard deviation of the ?ve studied samples of sediment core).
D.C.Ribeiro et al./Chemosphere 70(2008)1256–12631261
reduction has been questioned(Golterman,2001).Gol-terman(2001)has also shown by calculation(for an hypo-thetical shallow lake)of the reduction capacity,that the BD-P contribution from the sediments to the overlaying water is low,and that small changes in Fe(OOH)concentra-tion will have no impact in P release(Golterman,2001).Fur-ther work over samples collected along the present study, including speci?c rate?ux calculation,will be done to inves-tigate the role of BD-P pool in the eutrophication problem.
4.3.Metallic oxide bound phosphorus(NaOH-P)
The concentration of P bound to Fe and Al oxides is much higher in the two eutrophic lakes that in the Lake Fogo(oligo-to-mesotrophic).The NaOH-P amount in Lake Furnas is about six times higher than Lake Fogo.This extraction step is the major contributor to SRP concentra-tion for both Lake Furnas and Sete Cidades(Fig.5).Lake Furnas has also the highest concentration of dissolved iron in the water(241l g là1at deepest site,and an average of 100l g là1)of all the three lakes,as shown by Cruz and Franc?a(2006).Therefore,Lake Furnas presents the highest value of NaOH-P concentration.It has been shown that NaOH extractable P is signi?cantly correlated with2-days and14-days available P for an alga named Selenastrum cap-ricornutum(Zhou et al.,2001).This specie is present in some lakes in the Azores archipelago,but has not been identi?ed in the studied lakes.However,several species from de Sele-nastrum sp.gender are now included in the Ankistrodesmus sp.and Monoraphidium sp.genders.In the Furnas and Sete Cidades lakes,several species form the Ankistrodesmus sp. and Monoraphidium sp.genders were identi?ed.This means that,the NaOH-P could be available for these algal species. The NaOH extractable P has also been suggested to be used for estimation of short and long-term available P in the sed-iment,and is a measure of algal available phosphorus(Zhou et al.,2001).In this context,we can say that,both Lake Fur-nas and Sete Cidades have a highly potential available P for algae,which is undesirable for the eutrophication control.
As shown by Xiangcan Jin et al.(2006),NaOH-P might be released by the change of pH to higher values.In this case,pH control is very important,as this is the main potential pool for P-release in the studied lakes.However, this extraction step has been criticized because it seems that it is not so speci?c for metallic oxide bound P,as it is claimed to be.Golterman(2001)has shown that phosphate extraction with NaOH is time and concentration dependent and will also extract phytate phosphate and org-P as well. Therefore,the use of this extraction step will be pondered and more deeply studied in further research.
4.4.Apatite and CaCO3bound phosphorus(HCl-P)
The three studied lakes are from volcanic origin and are soft-water lakes,with total hardness of16.67mg là1, 9.08mg là1and4.53mg là1for Furnas,Sete Cidades and Fogo lakes,respectively.Therefore,Ca and Mg are present in low concentrations in these waters(Table1).This might be the reason why,in these lakes,the HCl-P concentration is much lower than the NaOH-P fraction,when compared with other hard-water lakes that has hight HCl-P concen-trations(Gonsiorczyk et al.,1998;Kaiserli et al.,2002). Apatite-P(which is mainly extracted by HCl)is assumed to be an inert fraction(Psenner and Pucsko,1988).Thus, the P concentration in this extraction step will not be bio-available so easily,being considered permanent burial (Jin et al.,2006).
https://www.wendangku.net/doc/d0734900.html,bile organic and refractory P(NaOH-P at85°C)
This extraction step also seems to be an inert P-fraction resulting from soils,terrestrial plant material and dust, loaded into the lakes by in?ows,wind and precipitation (Psenner and Pucsko,1988).This is the main P pool in Fogo Lake.As demonstrated in Fig.5,P contribution at Fogo lake increase from the?rst to the next extraction steps.This is desirable in terms of potential P release to the overlaying water,because it means that the higher P concentration pools are the most inert ones.So,the P release will not occur easily in this lake,preventing eutro-phication.However,a question is proposed when looking to the results for the other two lakes(Fig.5):is it possible that hot-NaOH-P pool would be partially transformed into NaOH-P pool,by biological activity?If these two P pools can be biologically related,then this would explain why NaOH-P pool is much higher than hot-NaOH-P pool, for Furnas and Sete Cidades Lakes.This would also be a concern for the future trophic status of Lake Fogo.There-fore,more research in this area is needed.
4.6.Phosphorus maximum solubilization potential
The results,in Table3,show that the P-MSP value in Fogo lake is higher in the most inert fraction(NaOH-SRP at85°C).Even for the more bio-available P-fractions (?rst and second extraction step),the P-MSP values are under2.l g P là1,which would not have any impact.In fact,the sum of all P-MSP values for the Fogo lake is 40l g P là1.
On the other hand,looking at the P-MSP values for Furnas and Sete Cidades lake,algal bloom risk is evident. Although P-MSP is in relatively low concentration for the most bio-available P forms(under13l g P là1),the P-MSP values for the P-NaOH fraction are182and38l g P là1for Furnas and Sete Cidades,respectively.Thus,it is expected that these two lakes could su?er a more intense eutro?ca-tion process in a short term.
Acknowledgements
The authors wish to thank the?eld expertise provided by Mr.Jose′Gouveia and the comments provided by Dr. Dina Pacheco.The authors also acknowledge the Grant SFRH/BD/25653/2005from the Foundation for Science
1262 D.C.Ribeiro et al./Chemosphere70(2008)1256–1263
and Technology/M.C.T.,Portugal,awarded to Ribeiro, D.C.
References
APHA,AWWA,WPCF,1995.Standard methods for the examination of water and wastewater.
Booth,B.,Croasdale,R.,Walker,G.,1978.A quantitative study of?ve thousand years of volcanism on Sa?o Miguel,Azores.Philos.Trans.
Roy.Soc.Lond.288,271–319.
Cruz,J.V.,Franc?a,Z.,2006.Hydrogeochemistry of thermal and mineral water springs of the Azores archipelago(Portugal).J.Volcanol.Geoth.
Res.151(4),382–398.
Golterman,H.L.,2001.Phosphate release from anoxic sediments or ‘What did Mortimer really write?’.Hydrobiologia450(1–3),99–106. Gonsiorczyk,T.,Casper,P.,Koschel,R.,1998.Phosphorus-binding forms in the sediment of an oligotrophic and an eutrophic hardwater lake of the Baltic Lake District(Germany).Water Sci.Technol.37(3), 51–58.
Jin,X.,Wang,S.,Pang,Y.,Chang Wu,F.,2006.Phosphorus fractions and the e?ect of pH on the phosphorus release of the sediments from di?erent trophic areas in Taihu Lake.China Environ.Pollut.139(2), 288–295.
Kaiserli,A.,Voutsa,D.,Samara,C.,2002.Phosphorus fractionation in lake sediments–Lakes Volvi and Koronia,N.Greece.Chemosphere 46(8),1147–1155.Kim,L.H.,Choi,E.,Stenstrom,M.K.,2003.Sediment characteristics, phosphorus types and phosphorus release rates between river and lake sediments.Chemosphere50(1),53–61.
Lijklema,L.,Koelmans,A.,Portielje,R.,1993.Water quality impacts of sediment pollution and the role of early diagenesis.Water Sci.Technol.
28(8–9),1–12.
Romero-Gonzalez,M.E.,Zambrano,E.,Mesa,J.,Ledo de Medina,H., 2001.Fractional phosphate composition in sediments from a tropical river(Catatumbo River,Venezuela).Hydrobiologia.
Pettersson,K.,Bostro¨m,B.,Jacobsen,O.,1988.Phosphorus in Sediments –speciation and analysis.Hydrobiologia170,91–101.
Psenner,R.,Pucsko,R.,1988.Phosphorus fractionation:advantages and limits of the method for the study of sediment P origins and interactions.Arch.Hydrobiol.Beih30,43–59.
Ramm,K.,Scheps,V.,1997.Phosphorus balance of a polytrophic shallow lake with the consideration of phosphorus release.Hydrobiologia342–343(0),43–53.
Ruban,V.,Lo′pez-Sa′nchez,J.F.,Pardo,P.,Rauret,G.,Muntau,H., Quevauviller,Ph.,1999.Selection and evaluation of sequential extraction procedures for the determination of phosphorus forms in lake sediment.J.Environ.Monitor.1,51–56.
Ruttenberg,K.C.,1992.Development of sequential extraction method for di?erent forms of phosphorus in marine sediments.Limnol.Oceanogr.
37(7),1460–1482.
Zhou,Q.,Gibson, C.E.,Zhu,Y.,2001.Evaluation of phosphorus bioavailability in sediments of three contrasting lakes in China and the UK.Chemosphere42(2),221–225.
D.C.Ribeiro et al./Chemosphere70(2008)1256–12631263
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1N4733 5V1 1N4734 5V6 1N4735 6V2 1N4736 6V8 1N4737 7V5 1N4738 8V2 1N4739 9V1 1N4740 10V 1N4741 11V 1N4742 12V 1N4743 13V 1N4744 15V 1N4745 16V 1N4746 18V 1N4747 20V 1N4748 22V 1N4749 24V 1N4750 27V 1N4751 30V 1N4752 33V 1N4753 36V 1N4754 39V 1N4755 43V 1N4756 47V 1N4757 51V DZ是稳压管的电器编号，是和1N4148和相近的，其实1N4148就是一个0.6V的稳压管，下面是稳压管上的编号对应的稳压值，有些小的稳压管也会在管体 上直接标稳压电压，如5V6就是5.6V的稳压管。 1N4728A 3.3 1N4729A 3.6 1N4730A 3.9 1N4731A 4.3 1N4732A 4.7 1N4733A 5.1 1N4734A 5.6 1N4735A 6.2 1N4736A 6.8 1N4737A 7.5 1N4738A 8.2 1N4739A 9.1 1N4740A 10 1N4741A 11 1N4742A 12 1N4743A 13
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分，有括号的作用。知识的问题是一个科学问题，来不得半点的虚伪和骄 傲，决定地需要的倒是其反面——诚实和谦逊的态度。2.表示意思的递进。 团结——批评和自我批评——团结3.表示意思的转折。很白很亮的一堆洋 钱！而且是他的——现在不见了！连接号⑥—1.表示时间、地点、数目等 的起止。抗日战争时期（1937-1945年）“北京—上海”直达快车2.表 示相关的人或事物的联系。亚洲—太平洋地区书名号⑦《》〈〉表示 书籍、文件、报刊、文章等的名称。《矛盾论》《中华人民共和国宪法》《人 民日报》《红旗》杂志《学习〈为人民服务〉》间隔号·1.表示月份和日期 之间的分界。一二·九运动2.表示某些民族人名中的音界。诺尔曼·白求 恩着重号.表示文中需要强调的部分。学习马克思列宁主义，要按照毛泽 东同志倡导的方法，理论联系实际。······
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In\ on\ at (time) at 用在具体某一时刻eg at 11:00 at 4:30 在节假日的全部日子里at Christmas 习惯用法at noon at weekends\ at the weekend at night at breakfast\lunch\supper on 具体到某一天；某一天的早晨，中午或晚上on May the first on Sunday morning 对具体某一天的早晨，中午，晚上进行详细的描述on a sunny morning on a windy night 节日的当天；星期on Women?s Day on Monday In 用在年；月；季节in spring in 2012 in August 后面+一段时间表示将来时in two days 习惯用法in the morning\in the afternoon\in the evening “\”以this, that, last, next, some, every, one, any,all开始的时间副词之前的at\on\in 省略在today, tomorrow, yesterday, the day after tomorrow, tomorrow morning，yesterday afternoon，the day before yesterday 之前的介词必须省略 Practice ___ summer ____ 2012 ____ supper ___ 4:00 ___ June the first ___yesterday morning ____ New Year?s Day ___ Women?s Day ___ the morning ____ the morning of July the first ____ 2014 ___ tomorrow morning ____ midnight 1.—What are you doing ____ Sunday? And what is your wife doing ___ the weekend? 2. He?ll see you ____ Monday. And he…ll see your brother ____next Monday. 3. They often go out ___ the evenings. But they don?t go out ____ Sunday evenings. 4. Do you work ____ Fridays? Does she work _____ every Friday? 5. They usually have a long holiday ___ summer. But their son can only have a short holiday ___ Christmas. 6. Paul got married ___ 2010, He got married ___ 9 o?clock ___ 19 May 2010. His brother got married ___ May, 2011. His sister is getting married ___ this year. 1.—When will Mr Black come to Beijing? ---_______ September 5 A. on B. to C. at D. in 2. The twins were born ____ a Friday evening. A. on B. of C. at D. in 3. It?s the best time to plant ____ spring. A. on B. in C. at D.\ 4. ____ the age of twelve, Edison began selling newspaper on train. A. On B. At C. In D.By 5. She has been an English teacher ____ 2000. A. for B. since C. in D.on 6.I have studied English _____ 2003. A. since B. for C. from D.in
二极管封装大全
二极管封装大全 篇一：贴片二极管型号、参数 贴片二极管型号.参数查询 1、肖特基二极管SMA（DO214AC） 2010-2-2 16:39:35 标准封装： SMA 2010 SMB 2114 SMC 3220 SOD123 1206 SOD323 0805 SOD523 0603 IN4001的封装是1812 IN4148的封装是1206 篇二：常见贴片二极管三极管的封装 常见贴片二极管/三极管的封装 常见贴片二极管/三极管的封装 二极管： 名称尺寸及焊盘间距其他尺寸相近的封装名称 SMC SMB SMA SOD-106 SC-77A SC-76/SC-90A SC-79 三极管： LDPAK
DPAK SC-63 SOT-223 SC-73 TO-243/SC-62/UPAK/MPT3 SC-59A/SOT-346/MPAK/SMT3 SOT-323 SC-70/CMPAK/UMT3 SOT-523 SC-75A/EMT3 SOT-623 SC-89/MFPAK SOT-723 SOT-923 VMT3 篇三：常用二极管的识别及ic封装技术 常用晶体二极管的识别 晶体二极管在电路中常用“D”加数字表示，如： D5表示编号为5的二极管。 1、作用：二极管的主要特性是单向导电性，也就是在正向电压的作用下，导通电阻很小;而在反向电压作用下导通电阻极大或无穷大。正因为二极管具有上述特性，无绳电话机中常把它用在整流、隔离、稳压、极性保护、编码控制、调频调制和静噪等电路中。 电话机里使用的晶体二极管按作用可分为：整流二极管(如1N4004)、隔离二极管(如1N4148)、肖特基二极管(如BAT85)、发光二极管、稳压二极管等。 2、识别方法：二极管的识别很简单，小功率二极管的N极(负极)，在二极管外表大多采用一种色圈标出来，有些二极管也用二极管专用符号来表示P极(正极)或N极(负极)，也有采用符号标志为“P”、“N”来确定二极管极性的。发光二极管的正负极可从引脚长短来识别，长
常用标点符号用法含义
一、基本定义 句子，前后都有停顿，并带有一定的句调，表示相对完整的意义。句子前后或中间的停顿，在口头语言中，表现出来就是时间间隔，在书面语言中，就用标点符号来表示。一般来说，汉语中的句子分以下几种： 陈述句： 用来说明事实的句子。 祈使句： 用来要求听话人做某件事情的句子。 疑问句： 用来提出问题的句子。 感叹句： 用来抒发某种强烈感情的句子。 复句、分句： 意思上有密切联系的小句子组织在一起构成一个大句子。这样的大句子叫复句，复句中的每个小句子叫分句。 构成句子的语言单位是词语，即词和短语（词组）。词即最小的能独立运用的语言单位。短语，即由两个或两个以上的词按一定的语法规则组成的表达一定意义的语言单位，也叫词组。 标点符号是书面语言的有机组成部分，是书面语言不可缺少的辅助工具。它帮助人们确切地表达思想感情和理解书面语言。 二、用法简表 名称
句号① 问号符号用法说明。？1．用于陈述句的末尾。 2．用于语气舒缓的祈使句末尾。 1．用于疑问句的末尾。 2．用于反问句的末尾。 1．用于感叹句的末尾。 叹号！ 2．用于语气强烈的祈使句末尾。 3．用于语气强烈的反问句末尾。举例 xx是xx的首都。 请您稍等一下。 他叫什么名字？ 难道你不了解我吗？为祖国的繁荣昌盛而奋斗！停止射击！ 我哪里比得上他呀！ 1．句子内部主语与谓语之间如需停顿，用逗号。我们看得见的星星，绝大多数是恒星。 2．句子内部动词与宾语之间如需停顿，用逗号。应该看到，科学需要一个人贡献出毕生的精力。 3．句子内部状语后边如需停顿，用逗号。对于这个城市，他并不陌生。 4．复句内各分句之间的停顿，除了有时要用分号据说苏州园林有一百多处，我到过的不外，都要用逗号。过十多处。 顿号、用于句子内部并列词语之间的停顿。
2时间介词in,on,at的用法
介词in on at 表示时间的用法及区别 Step1 Teaching Aims 教学生掌握时间介词in,on和at的区别及用法。 Step2 Teaching Key and Difficult Points 教学生掌握时间介词in,on和at的区别及用法。 Step3 Teaching Procedures 1.用in的场合后所接的都是较长时间 (1)表示“在某世纪/某年代/特定世纪某年代/年/季节/月”这个含义时，须用介词in Eg: This machine was invented in the eighteenth century. 这台机器是在18世纪发明的。 、 She came to this city in 1980. 他于1980年来到这个城市。 It often rains here in summer. 夏天这里常常下雨。 (2)表示“从现在起一段时间以后”时，须用介词in。(in+段时间表将来) Eg: They will go to see you in a week. 他们将在一周后去看望你。
I will be back in a month. 我将在一个月后回来。 (3)泛指一般意义的上、下午、晚上用in, in the morning / evening / afternoon Eg: They sometimes play games in the afternoon. 他们有时在下午做游戏。 Don't watch TV too much in the evening. 晚上看电视不要太多。（4）A. 当morning, evening, afternoon被of短语修饰，习惯上应用on, 而不用in. Eg: on the afternoon of August 1st & B. 但若前面的修饰词是early, late时，虽有of短语修饰，习惯上应用in, 而不用on. Eg: in the early morning of September 10th 在9月10的清晨； Early in the morning of National Day, I got up to catch the first bus to the zoo. 国庆节一清早，我便起床去赶到动物园的第一班公共汽车。 2.用on的场合后所接的时间多与日期有关 （1）表示“在具体的某一天”或（在具体的某一天的）早上、中午、晚上”，或“在某一天或某一天的上午，下午，晚上”等，须用介
1N系列常用整流二极管的主要参数
1N 系列常用整流二极管的主要参数
反向工作 峰值电压 URM/V 额定正向 整流电流 整流电流 IF/A 正向不重 复浪涌峰 值电流 IFSM/A 正向 压降 UF/V 反向 电流 IR/uA 工作 频率 f/KHZ 外形 封装
型 号
1N4000 1N4001 1N4002 1N4003 1N4004 1N4005 1N4006 1N4007 1N5100 1N5101 1N5102 1N5103 1N5104 1N5105 1N5106 1N5107 1N5108 1N5200 1N5201 1N5202 1N5203 1N5204 1N5205 1N5206 1N5207 1N5208 1N5400 1N5401 1N5402 1N5403 1N5404 1N5405 1N5406 1N5407 1N5408
25 50 100 200 400 600 800 1000 50 100 200 300 400 500 600 800 1000 50 100 200 300 400 500 600 800 1000 50 100 200 300 400 500 600 800 1000
1
30
≤1
＜5
3
DO-41
1．5
75
≤1
＜5
3
DO-15
2
100
≤1
＜10
3
3
150
≤0.8
＜10
3
DO-27
常用二极管参数： 05Z6.2Y 硅稳压二极管 Vz=6~6.35V,Pzm=500mW,
介词in-on-at在表示时间时的用法
介词in, on, at在表示时间时的用法区别 ①in时间范围大（一天以上）如：in Tanuary, in winter, in 1999;泛指在上午，下午，晚上，如：in the morning(afternoon, evening). 习惯用法：in the daytime 在白天。 ②on指在某一天或某一天的上午，下午，晚上，如：on Monday, on Sunday afternoon, on July 1, 1999 ③at时间最短，一般表示点时间，如at six o’clock, at three thirty.习惯用法：at night, at noon, at this time of year. in, on和at在表达时间方面的区别 in 表示在某年、某季节、某月、某周、某天和某段时间 in a year在一年中 in spring 在春季 in September 在九月 in a week 在一周中 in the morning/afternoon/evening 在上午/下午/傍晚 但在中午，在夜晚则用at noon/night on 表示某一天或某一天的某段时间 on Monday 在周一 on Monday afternoon 在周一下午 on March 7th 在3月7日 on March 7th, 1998. 在1998年3月7日 on the morning of March 7th, 1998. 在1998年3月7日上午
at 表示某个具体时刻。 at eight o’clock 在8点钟 at this time of the year 在一年中的这个时候 at the moment 在那一时刻 at that time 在那时 注意：在英语中，如果时间名词前用this, last, next 等修饰时，像这样的表示，“在某时”的时间短语前，并不需要任何介词。 例如：last month, last week, this year, this week, next year, the next day, the next year 等。 1．What’s the weather like in spring/summer/autumn/winter in your country? 你们国家春天/夏天/秋天/冬天的天气怎么样？ in 在年、月、周较长时间内 in a week 在里面 in the room 用某种语言 in English 穿着 in red on 某日、某日的上下午on Sunday afternoon 在……上面 on the desk 靠吃……为生live on rice 关于 a book on Physics 〔误〕We got to the top of the mountain in daybreak. 〔正〕We got to the top of the mountain at day break. 〔析〕at用于具体时刻之前，如：sunrise, midday, noon, sunset, midnight, night。〔误〕Don't sleep at daytime 〔正〕Don't sleep in daytime. 〔析〕in 要用于较长的一段时间之内，如：in the morning / afternoon, 或in the week / month / year. 或in spring / supper /autumn / winter等等。 〔误〕We visited the old man in Sunday afternoon. 〔正〕We visited the old man on Sunday afternoon. 〔析〕in the morning, in the afternoon 如果在这两个短语中加入任何修饰词其前面的介
常见二极管参数大全
1N系列稳压管
快恢复整流二极管
常用整流二极管型号和参数 05Z6.2Y 硅稳压二极管 Vz=6~6.35V,Pzm=500mW, 05Z7.5Y 硅稳压二极管 Vz=7.34~7.70V,Pzm=500mW, 05Z13X硅稳压二极管 Vz=12.4~13.1V,Pzm=500mW, 05Z15Y硅稳压二极管 Vz=14.4~15.15V,Pzm=500mW, 05Z18Y硅稳压二极管 Vz=17.55~18.45V,Pzm=500mW, 1N4001硅整流二极管 50V, 1A,(Ir=5uA,Vf=1V,Ifs=50A) 1N4002硅整流二极管 100V, 1A, 1N4003硅整流二极管 200V, 1A, 1N4004硅整流二极管 400V, 1A, 1N4005硅整流二极管 600V, 1A, 1N4006硅整流二极管 800V, 1A, 1N4007硅整流二极管 1000V, 1A, 1N4148二极管 75V, 4PF,Ir=25nA,Vf=1V, 1N5391硅整流二极管 50V, 1.5A,(Ir=10uA,Vf=1.4V,Ifs=50A) 1N5392硅整流二极管 100V,1.5A, 1N5393硅整流二极管 200V,1.5A, 1N5394硅整流二极管 300V,1.5A, 1N5395硅整流二极管 400V,1.5A, 1N5396硅整流二极管 500V,1.5A, 1N5397硅整流二极管 600V,1.5A, 1N5398硅整流二极管 800V,1.5A, 1N5399硅整流二极管 1000V,1.5A, 1N5400硅整流二极管 50V, 3A,(Ir=5uA,Vf=1V,Ifs=150A) 1N5401硅整流二极管 100V,3A, 1N5402硅整流二极管 200V,3A, 1N5403硅整流二极管 300V,3A, 1N5404硅整流二极管 400V,3A,
常用稳压二极管技术参数及老型号代换.
常用稳压二极管技术参数及老型号代换 型号最大功耗 (mW) 稳定电压(V) 电流(mA) 代换型号国产稳压管日立稳压管 HZ4B2 500 3.8 4.0 5 2CW102 2CW21 4B2 HZ4C1 500 4.0 4.2 5 2CW102 2CW21 4C1 HZ6 500 5.5 5.8 5 2CW103 2CW21A 6B1 HZ6A 500 5.2 5.7 5 2CW103 2CW21A HZ6C3 500 6 6.4 5 2CW104 2CW21B 6C3 HZ7 500 6.9 7.2 5 2CW105 2CW21C HZ7A 500 6.3 6.9 5 2CW105 2CW21C HZ7B 500 6.7 7.3 5 2CW105 2CW21C HZ9A 500 7.7 8.5 5 2CW106 2CW21D HZ9CTA 500 8.9 9.7 5 2CW107 2CW21E HZ11 500 9.5 11.9 5 2CW109 2CW21G HZ12 500 11.6 14.3 5 2CW111 2CW21H HZ12B 500 12.4 13.4 5 2CW111 2CW21H HZ12B2 500 12.6 13.1 5 2CW111 2CW21H 12B2 HZ18Y 500 16.5 18.5 5 2CW113 2CW21J HZ20-1 500 18.86 19.44 2 2CW114 2CW21K HZ27 500 27.2 28.6 2 2CW117 2CW21L 27-3 HZT33-02 400 31 33.5 5 2CW119 2CW21M RD2.0E(B) 500 1.88 2.12 20 2CW100 2CW21P 2B1 RD2.7E 400 2.5 2.93 20 2CW101 2CW21S RD3.9EL1 500 3.7 4 20 2CW102 2CW21 4B2 RD5.6EN1 500 5.2 5.5 20 2CW103 2CW21A 6A1 RD5.6EN3 500 5.6 5.9 20 2CW104 2CW21B 6B2 RD5.6EL2 500 5.5 5.7 20 2CW103 2CW21A 6B1 RD6.2E(B) 500 5.88 6.6 20 2CW104 2CW21B RD7.5E(B) 500 7.0 7.9 20 2CW105 2CW21C RD10EN3 500 9.7 10.0 20 2CW108 2CW21F 11A2 RD11E(B) 500 10.1 11.8 15 2CW109 2CW21G RD12E 500 11.74 12.35 10 2CW110 2CW21H 12A1 RD12F 1000 11.19 11.77 20 2CW109 2CW21G RD13EN1 500 12 12.7 10 2CW110 2CW21H 12A3 RD15EL2 500 13.8 14.6 15 2CW112 2CW21J 12C3 RD24E 400 22 25 10 2CW116 2CW21H 24-1
常用稳压管型号参数对照
常用稳压管型号参数对照 3V到51V 1W稳压管型号对照表1N4727 3V0 1N4728 3V3 1N4729 3V6 1N4730 3V9 1N4731 4V3 1N4732 4V7 1N4733 5V1 1N4734 5V6 1N4735 6V2 1N4736 6V8 1N4737 7V5
1N4739 9V1 1N4740 10V 1N4741 11V 1N4742 12V 1N4743 13V 1N4744 15V 1N4745 16V 1N4746 18V 1N4747 20V 1N4748 22V 1N4749 24V 1N4750 27V 1N4751 30V
1N4753 36V 1N4754 39V 1N4755 43V 1N4756 47V 1N4757 51V 摩托罗拉IN47系列1W稳压管IN4728 3.3v IN4729 3.6v IN4730 3.9v IN4731 4.3 IN4732 4.7 IN4733 5.1
IN4735 6.2 IN4736 6.8 IN4737 7.5 IN4738 8.2 IN4739 9.1 IN4740 10 IN4741 11 IN4742 12 IN4743 13 IN4744 15 IN4745 16 IN4746 18 IN4747 20
IN4749 24 IN4750 27 IN4751 30 IN4752 33 IN4753 34 IN4754 35 IN4755 36 IN4756 47 IN4757 51 摩托罗拉IN52系列 0.5w精密稳压管IN5226 3.3v IN5227 3.6v