1-s2.0-S0047637408002832-main

ASCII码表信息在计算机上是用二进制表示的，这种表示法让人理解就很困难。

因此计算机上都配有输入和输出设备，这些设备的主要目的就是，以一种人类可阅读的形式将信息在这些设备上显示出来供人阅读理解。

为保证人类和设备，设备和计算机之间能进行正确的信息交换，人们编制的统一的信息交换代码，这就是ASCII码表，它的全称是“美国信息交换标准代码”。

ASCII码对照表在Web开发时，如下的ASCII码只要加上&#和;就可以变成Web可以辨认的字符了在处理特殊字符的时候特别有用，如：' 单引号在数据库查询的时候是杀手，但是如果转换成'（注意：转换后的机构有：&# +字符的ASCII码值+; 三个部分组成）再来存数据库，就没有什么影响了。

其他的字符与ASCII码的对照如下表ASCII表键盘常用ASCII码ESC键 VK_ESCAPE (27)回车键： VK_RETURN (13)TAB键： VK_TAB (9)Caps Lock键： VK_CAPITAL (20) Shift键： VK_SHIFT ($10)Ctrl键： VK_CONTROL (17)Alt键： VK_MENU (18)空格键： VK_SPACE ($20/32)退格键： VK_BACK (8)左徽标键： VK_LWIN (91)右徽标键： VK_LWIN (92)鼠标右键快捷键：VK_APPS (93)Insert键： VK_INSERT (45) Home键： VK_HOME (36)Page Up： VK_PRIOR (33) PageDown： VK_NEXT (34)End键： VK_END (35)Delete键： VK_DELETE (46)方向键(←)： VK_LEFT (37)方向键(↑)： VK_UP (38)方向键(→)： VK_RIGHT (39)方向键(↓)： VK_DOWN (40)F1键： VK_F1 (112)F2键： VK_F2 (113)F3键： VK_F3 (114)F4键： VK_F4 (115)F5键： VK_F5 (116)F6键： VK_F6 (117)F7键： VK_F7 (118)F8键： VK_F8 (119)F9键： VK_F9 (120)F10键： VK_F10 (121)F11键： VK_F11 (122)F12键： VK_F12 (123)Num Lock键： VK_NUMLOCK (144) 小键盘0： VK_NUMPAD0 (96)小键盘1： VK_NUMPAD0 (97)小键盘2： VK_NUMPAD0 (98)小键盘3： VK_NUMPAD0 (99)小键盘4： VK_NUMPAD0 (100)小键盘5： VK_NUMPAD0 (101)小键盘6： VK_NUMPAD0 (102)小键盘7： VK_NUMPAD0 (103)小键盘8： VK_NUMPAD0 (104)小键盘9： VK_NUMPAD0 (105)小键盘.： VK_DECIMAL (110)小键盘*： VK_MULTIPLY (106)小键盘+： VK_MULTIPLY (107)小键盘-： VK_SUBTRACT (109)小键盘/： VK_DIVIDE (111)Pause Break键： VK_PAUSE (19) Scroll Lock键： VK_SCROLL (145)。

关键字：最全ASCII码对照表 ASCII码值对照表 ASCII码值 ASCII码中英文对照表Bin Dec Hex 缩写/字符解释0000 0000 0 00 NUL (null) 空字符0000 0001 1 01 SOH (start of handing) 标题开始0000 0010 2 02 STX (start of text) 正文开始0000 0011 3 03 ETX (end of text) 正文结束0000 0100 4 04 EOT (end of transmission) 传输结束0000 0101 5 05 ENQ (enquiry) 请求0000 0110 6 06 ACK (acknowledge) 收到通知0000 0111 7 07 BEL (bell) 响铃0000 1000 8 08 BS (backspace) 退格0000 1001 9 09 HT (horizontal tab) 水平制表符0000 1010 10 0A LF (NL line feed, new line) 换行键0000 1011 11 0B VT (vertical tab) 垂直制表符0000 1100 12 0C FF (NP form feed, new page) 换页键0000 1101 13 0D CR (carriage return) 回车键0000 1110 14 0E SO (shift out) 不用切换0000 1111 15 0F SI (shift in) 启用切换0001 0000 16 10 DLE (data link escape) 数据链路转义0001 0001 17 11 DC1 (device control 1) 设备控制1 0001 0010 18 12 DC2 (device control 2) 设备控制2 0001 0011 19 13 DC3 (device control 3) 设备控制3 0001 0100 20 14 DC4 (device control 4) 设备控制4 0001 0101 21 15 NAK (negative acknowledge) 拒绝接收0001 0110 22 16 SYN (synchronous idle) 同步空闲0001 0111 23 17 ETB (end of trans. block) 传输块结束0001 1000 24 18 CAN (cancel) 取消0001 1001 25 19 EM (end of medium) 介质中断0001 1010 26 1A SUB (substitute) 替补0001 1011 27 1B ESC (escape) 溢出0001 1100 28 1C FS (file separator) 文件分割符0001 1101 29 1D GS (group separator) 分组符0001 1110 30 1E RS (record separator) 记录分离符0001 1111 31 1F US (unit separator) 单元分隔符0010 0000 32 20 空格0010 0001 33 21 !0010 0010 34 22 "0010 0011 35 23 # 0010 0100 36 24 $ 0010 0101 37 25 % 0010 0110 38 26 & 0010 0111 39 27 ' 0010 1000 40 28 ( 0010 1001 41 29 ) 0010 1010 42 2A * 0010 1011 43 2B + 0010 1100 44 2C , 0010 1101 45 2D - 0010 1110 46 2E . 0010 1111 47 2F / 0011 0000 48 30 0 0011 0001 49 31 1 0011 0010 50 32 2 0011 0011 51 33 3 0011 0100 52 34 4 0011 0101 53 35 5 0011 0110 54 36 6 0011 0111 55 37 7 0011 1000 56 38 8 0011 1001 57 39 9 0011 1010 58 3A : 0011 1011 59 3B ; 0011 1100 60 3C < 0011 1101 61 3D = 0011 1110 62 3E > 0011 1111 63 3F ? 0100 0000 64 40 @ 0100 0001 65 41 A 0100 0010 66 42 B 0100 0011 67 43 C 0100 0100 68 44 D 0100 0101 69 45 E 0100 0110 70 46 F 0100 0111 71 47 G0100 1000 72 48 H 0100 1001 73 49 I 0100 1010 74 4A J 0100 1011 75 4B K 0100 1100 76 4C L 0100 1101 77 4D M 0100 1110 78 4E N 0100 1111 79 4F O 0101 0000 80 50 P 0101 0001 81 51 Q 0101 0010 82 52 R 0101 0011 83 53 S 0101 0100 84 54 T 0101 0101 85 55 U 0101 0110 86 56 V 0101 0111 87 57 W 0101 1000 88 58 X 0101 1001 89 59 Y 0101 1010 90 5A Z 0101 1011 91 5B [ 0101 1100 92 5C \ 0101 1101 93 5D ] 0101 1110 94 5E ^ 0101 1111 95 5F _ 0110 0000 96 60 ` 0110 0001 97 61 a 0110 0010 98 62 b 0110 0011 99 63 c 0110 0100 100 64 d 0110 0101 101 65 e 0110 0110 102 66 f 0110 0111 103 67 g 0110 1000 104 68 h 0110 1001 105 69 i 0110 1010 106 6A j 0110 1011 107 6B k 0110 1100 108 6C l0110 1101 109 6D m0110 1110 110 6E n0110 1111 111 6F o0111 0000 112 70 p0111 0001 113 71 q0111 0010 114 72 r0111 0011 115 73 s0111 0100 116 74 t0111 0101 117 75 u0111 0110 118 76 v0111 0111 119 77 w0111 1000 120 78 x0111 1001 121 79 y0111 1010 122 7A z0111 1011 123 7B {0111 1100 124 7C |0111 1101 125 7D }0111 1110 126 7E ~0111 1111 127 7F DEL (delete) 删除ESC键 VK_ESCAPE (27)回车键：VK_RETURN (13)TAB键：VK_TAB (9)Caps Lock键： VK_CAPITAL (20)Shift键：VK_SHIFT ()Ctrl键： VK_CONTROL (17)Alt键：VK_MENU (18)空格键：VK_SPACE (/32)退格键：VK_BACK (8)左徽标键：VK_LWIN (91)右徽标键：VK_LWIN (92)鼠标右键快捷键：VK_APPS (93)Insert键：VK_INSERT (45)Home键：VK_HOME (36)Page Up：VK_PRIOR (33)PageDown：VK_NEXT (34)End键： VK_END (35)Delete键：VK_DELETE (46)方向键(←)：VK_LEFT (37)方向键(↑)： VK_UP (38)方向键(→)： VK_RIGHT (39)方向键(↓)： VK_DOWN (40)F1键： VK_F1 (112)F2键： VK_F2 (113)F3键： VK_F3 (114)F4键： VK_F4 (115)F5键： VK_F5 (116)F6键： VK_F6 (117)F7键： VK_F7 (118)F8键： VK_F8 (119)F9键： VK_F9 (120)F10键： VK_F10 (121)F11键： VK_F11 (122)F12键：VK_F12 (123)Num Lock键： VK_NUMLOCK (144)小键盘0： VK_NUMPAD0 (96)小键盘1：VK_NUMPAD0 (97)小键盘2：VK_NUMPAD0 (98)小键盘3：VK_NUMPAD0 (99)小键盘4： VK_NUMPAD0 (100)小键盘5： VK_NUMPAD0 (101)小键盘6：VK_NUMPAD0 (102)小键盘7：VK_NUMPAD0 (103)小键盘8：VK_NUMPAD0 (104)小键盘9： VK_NUMPAD0 (105)小键盘.：VK_DECIMAL (110)小键盘*：VK_MULTIPLY (106)小键盘+：VK_MULTIPLY (107)小键盘-：VK_SUBTRACT (109)小键盘/：VK_DIVIDE (111)Pause Break键： VK_PAUSE (19)Scroll Lock键： VK_SCROLL (145)关键字：最全ASCII码对照表 ASCII码值对照表 ASCII码值 ASCII码中英文对照表。

A first step towards identification of tannin-derived black carbon:Conventional pyrolysis (Py–GC–MS)and thermally assisted hydrolysis and methylation (THM–GC–MS)of charred condensed tanninsJoeri Kaal a ,⇑,Klaas G.J.Nierop b ,Peter Kraal c ,Caroline M.Preston daInstituto de Ciencias del Patrimonio (Incipit),Consejo Superior de Investigaciones Científicas (CSIC),San Roque 2,15704Santiago de Compostela,Spain bDepartment of Earth Sciences –Organic Geochemistry,Faculty of Geosciences,Utrecht University,P.O.Box 80021,3508TA Utrecht,The Netherlands cSouthern Cross GeoScience,Southern Cross University,P.O.Box 157,Lismore,2480New South Wales,Australia dPacific Forestry Centre,Natural Resources Canada,506West Burnside Rd.,Victoria,BC,Canada V8Z 1M5a r t i c l e i n f o Article history:Received 5October 2011Received in revised form 13March 2012Accepted 26March 2012Available online 5April 2012a b s t r a c tTannins account for a significant proportion of plant biomass and are likely to contribute to the residues formed by incomplete biomass combustion (black carbon,BC).Nonetheless,the molecular properties of thermally modified tannins have not been investigated in laboratory charring experiments.We applied conventional analytical pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS)and thermally assisted hydrolysis and methylation (THM–GC–MS)to investigate the effects of heat treatment with a muffle furnace on the properties of condensed tannins (CT)from Corsican pine (Pinus nigra )needles.Py–GC–MS showed a decrease in the relative abundance of the 1,2,3-trihydroxybenzenes (pyrogallols)at P 300°C and of the dihydroxybenzenes (mainly catechols)at P 350°C due to dehydroxylation of the CT B ring.Further dehydroxylation led to formation of monohydroxybenzenes (phenols),which showed a strong enrichment between 350and 400°C and,at higher temperatures,to a series of mono-cyclic and polycyclic aromatics [benzene,alkyl benzenes and polycondensed aromatic hydrocarbons (PAHs)].Degradation of the A ring could not be recognized via Py–GC–MS,probably because of the poor chromatographic behavior of 1,3,5-trihydroxybenzenes (phloroglucinols).The progressive dehydroxyla-tion and eventual polycondensation of the CT B ring was corroborated using THM–GC–MS.In addition,with THM–GC–MS the thermal rearrangement of CT A rings at 300°C and higher was inferred from the relative abundance of 1,3,5-trimethoxybenzenes (methylated phloroglucinol derivatives).These com-pounds were observed at moderate/high temperature (up to 450°C)and can not be produced from THM of lignin,suggesting that they may be markers of CT in natural BC samples.Ó2012Elsevier Ltd.All rights reserved.1.IntroductionTannins are among the most abundant plant biopolymers,typ-ically comprising 10–25%of foliar mass (Kraus et al.,2003).In leaves,needles and bark,tannin content often exceeds that of lig-nin (Hernes and Hedges,2004)and it is also present in woody tis-sue (Rogge et al.,1998).Tannins are strong antioxidants with multiple ecosystem functions,such as defense against herbivores,metal mobilization,radical scavenging and regulation of nutrient dynamics by protein precipitation and suppression of microbial activity (Zucker,1983;Kennedy et al.,1996;Fierer et al.,2001).Tannins from terrestrial plants can be divided into two main groups:condensed tannins (CT)and hydrolyzable tannins.Con-densed tannins are oligomers and polymers based on flavan-3-ol monomers linked through covalent bonds (Fig.1).Within thegroup of CT,there is variation in the distribution of OH groups on the aromatic B ring,forming procyanidin and prodelphinidin CT (e.g.Khanbabaee and van Ree,2001).Each CT monomer con-tains up to six OH functionalities concentrated on the aromatic A and B rings (Fig.1).These aromatic OH groups,especially those in adjacent positions on the B ring,give rise to the exceptional reactivity of CT in the environment (Slabbert,1992).Despite the fact that tannins form a major component of plant biomass,they have often been ignored as a possible source of poly-phenolic substances in soil organic matter;these have commonly been ascribed to lignin (Filley et al.,2006).This is also the case for phenolic moieties in biomass burning residue (black carbon,BC)(Baldock and Smernik,2002;Krull et al.,2003),which are abundant in BC formed at low/moderate temperature (e.g.Knicker et al.,2005,2007;Rumpel et al.,2006).In the light of growing interest in BC or ‘biochar’,amendment programs for soil ameliora-tion and C sequestration (Lehmann et al.,2006;Jeffery et al.,2011),the possible effects of charred tannins on soil microbial and nutri-ent dynamics must be understood (Warnock et al.,2010),as they0146-6380/$-see front matter Ó2012Elsevier Ltd.All rights reserved./10.1016/geochem.2012.03.009Corresponding author.Tel.:+34881813588;fax:+34881813601.E-mail address:joeri.kaal@incipit.csic.es (J.Kaal).may be anticipated to be vastly different from that of charred lig-nin.This is not possible,however,as methodologies for identifying charred tannins are not available and the thermal degradation pathways of tannins are largely unknown.The thermal alteration of plant tissue has been investigated in numerous studies,as reviewed by e.g.González-Pérez et al.(2004)and Preston and Schmidt (2006).Pyrolysis–gas chromatog-raphy–mass spectrometry (Py–GC–MS)is one method that can provide information on the molecular properties of BC (De la Rosa et al.,2008;Kaal and Rumpel,2009;Kaal et al.,2009;Fabbri et al.,2012),despite the fact that pyrolysis itself is a heat-induced scission reaction and that secondary rearrangements generate structures that may resemble the pyrolysis products of BC (Saiz-Jiménez,1994;Wampler,1999).Pyrolysis is a relatively inex-pensive and rapid technique that has also proven of value for tan-nin characterization (Galletti et al.,1995).Flash heating in the presence of tetramethylammonium hydroxide (TMAH)is referred to as thermally assisted hydrolysis and methylation (THM)or ther-mochemolysis.With THM,hydrolyzable bonds are cleaved and the resulting CO 2H and OH groups are transformed in situ to the corre-sponding methyl esters and methyl ethers,respectively (Challinor,2001;Hatcher et al.,2001;Shadkami and Helleur,2010),which are more amenable to GC than their underivatized counterparts.As such,THM–GC–MS provides additional information on tannin structure through detection of derivatized polyfunctionalized A and B rings (Nierop et al.,2005).In the present study the thermal degradation of CT was studied using laboratory charring experiments followed by characteriza-tion with Py–GC–MS and THM–GC–MS.The aim was to provide guidelines for the identification of CT-derived BC and identify the molecular changes as a function of charring temperature.2.Material and methodsCondensed tannins were isolated from Corsican pine (Pinus ni-gra var.maritima )needles from the coastal dunes in The Nether-lands (52°2004500N,4°3105700E)using the scheme proposed by Preston (1999)and described in detail by Nierop et al.(2005,2006).The CT were completely isolated from other components and had a prodelphinidin:procyanidin ratio of 2:1and average chain length of 6.6(Nierop et al.,2005).It has been used in various studies (Kaal et al.,2005;Nierop et al.,2006;Kraal et al.,2009).For the charring experiments,ca.200mg of CT were double wrapped in Al foil to simulate limited O 2availability during wild-fires.The samples were placed (30min)in a preheated muffle fur-nace at temperatures (T CHAR )from 200°C to 600°C.Similar experiments have been performed by Turney et al.(2006),Hall et al.(2008)and Wiesenberg et al.(2009).Weight loss was deter-mined gravimetrically before and after charring.C and H contents were determined by way of combustion using a LECO carbon ana-lyzer (model CHN-1000).Uncharred CT was used as a control.Py–GC–MS was performed in duplicate using a Pt filament coil probe Pyroprobe 5000pyrolyzer (CDS Analytical,Oxford,USA).Approximately 1–1.5mg sample was embedded in quartz tubes using glass wool.Pyrolysis was applied at 750°C for 10s (heating rate 10°C/ms).The method produces limited artificial charring during pyrolysis and a relatively high proportion of pyrolyzable biomass in comparison with pyrolysis at lower temperatures (Pastorova et al.,1994;Kaal et al.,2009;Song and Peng,2010).The pyrolysis interface was coupled to a 6890N GC instrument and 5975MSD (Agilent Technologies,Palo Alto,USA).The pyrolysis interface and GC inlet (split ratio 1:20)were set at 325°C.The GC instrument was equipped with a (non-polar)HP-5MS 5%phenyl,95%dimethylpolysiloxane column (30m Â0.25mm i.d.;film thickness 0.25l m)and He was the carrier gas (constant flow 1ml/min).The GC oven was heated from 50to 325°C (held 10min)at 20°C/min.The GC–MS transfer line was held at 270°C,the ion source (electron impact mode,70eV)at 230°C and the quadrupole detector at 150°C scanning a range between m /z 50and 500.Peak areas of the pyrolysis products were obtained from one or two characteristic or dominant fragment ions,the sum of which (total quantified peak area;TQPA)was set as 100%.Relative contributions of the pyrolysis products were calculated as %of TQPA.This is a semi-quantitative exercise that allows better comparison between samples than visual inspection of pyrolysis chromatograms alone.Benzofuran and styrene could not be quantified because of co-elution with contaminants.For THM–GC–MS,samples were pressed onto Curie-Point wires,after which a droplet of a 25%solution of TMAH in water was added,prior to drying under a 100W halogen lamp.THM was car-ried out using a Horizon Instruments Curie-Point pyrolyzer.Sam-ples were heated for 5s at 600°C.The pyrolysis unit was connected to a Carlo Erba GC8060furnished with a fused silica col-umn (Varian,25m Â0.25mm i.d.)coated with CP-Sil 5(film thick-ness 0.40l m).He was the carrier gas.The oven temperature program was:40°C (1min)to 200°C at 7°C/min and then to 320°C (held 5min)at 20°C/min.The column was coupled to a Fi-sons MD800MS instrument (m /z 45–650,ionization energy 70eV,cycle time 0.7s).Like Py–GC–MS,the relative contributions of the THM products were calculated as relative contributions to TQPA using 1–2dominant fragment ions.Benzene and toluene were not detected because they co-eluted with trimethylamine,the main side product of TMAH-based THM (Challinor,2001),i.e.with-in the solvent delay period (3min).Py–GC–MS and THM–GC–MS results were analyzed via princi-pal component analysis (PCA)to illustrate the major effects of heating on the pyrolysis and THM fingerprints,respectively,using SPSS 13.0.3.Results and discussion3.1.Weight loss and elemental compositionWeight loss from CT increased from 17%at T CHAR 200°C towards 56%at T CHAR 600°C (Table 1).The CT C content increased from 51%to 81%with increasing T CHAR .The atomic H/C ratio of the samples declined from 1.2to 0.6with increasing T CHAR ,reflecting loss of functional groups and formation of fused aromatic clusters through condensation (Braadbaart et al.,2004).Model structure of a condensed tannin oligomer;procyanidin,prodelphinidin,R =OH.47(2012)99–108chromatograms of uncharred(control)and charred(200–600°C)CT,from Py–GC–MS.Relative peak intensity vs.retention time3.2.Charred condensed tannin composition:Py–GC–MSPy–GC–MS total ion chromatograms are depicted in Fig.2.Total quantified peak area (Table 1),a rough measure of signal intensity,decreased with increasing T CHAR .This can be explained by the for-mation of non-pyrolyzable structures upon charring,probably through the formation of polycondensed aromatic clusters stable under pyrolysis conditions.However,this does not imply that the results from the high temperature chars should be dismissed for representing only a small and relatively volatilefraction:a more appropriate interpretation is that the samples consist largely of non-pyrolyzable fused aromatic clusters,corroborated by the dom-inant pyrolysis products of such samples (benzene and PAHs;see below)and lack of pyrolysis products from less intensely charred structures.The major pyrolysis products are listed in sponding retention times,fragment ions used and relative proportions.Products were structure,in particular the hydroxylation between benzenes (benzene and alkyl (with one OH),dihydroxybenzenes (DHB),(THB)and other compounds.The DHB are while the THB are based on pyrogallol moieties exclusively from prodelphinidin B rings.The uncharred CT isolate produced mainly pyrolysis (Table 2;Fig.3),which originate from prodelphinidin B rings,respectively.In contrast delphinidin:procyanidin ratio determined et al.,2005),the DHB were more abundant may be explained by way of the poor ‘‘visibility’’a non-polar GC column.The high proportion of and 4-methylpyrogallol points to scission of the the heterocyclic pyran C ring (Fig.1),which has sociation energy than the aromatic A and B acetone and acetic acid may represent the after pyrolysis.Products from the A ring were may be explained by the poor chromatographic rivatized 1,3,5-trihydroxybenzene principal pyrolysis product from the A ring (The lack of unambiguous A ring markers implies that Py–GC–MS cannot be used to study the degradation of the predominantly C-4/C-8and C-4/C-6intermonomeric linkages (Fig.1),and thus to investigate CT depolymerization.Some methoxyphenols (guaiacol and 4-vinylguaiacol)and catechol carbonate were detected.The guaiacols are commonly attributed to lignin and its derivatives (e.g.Kögel-Knabner,2002),but here they might alternatively orig-inate from C ring fission in CT (Galletti et al.,1995).The possibility of tannins as a source of the guaiacols is supported by the absence of resonances from methoxyphenols in liquid-state 13C NMR tra (Nierop et al.,2005)and guaiacols bearing a C 3side chain pyrolyzate,which should be detectable if residual lignin was ent in the fresh needle isolate (Saiz-Jiménez and de Leeuw,The results for uncharred CT were in good agreement with earlier pyrolysis experiments with tannin,catechin and gallocate-Relative proportion (TQPA)of pyrolysis product groups from CT vs.charring temperature (200–600°C);0°C,control (uncharred CT);THB,trihydroxybenzene;dihydroxybenzene;PAH,polycyclic aromatic hydrocarbon.Error bars reflect standard error of mean of two replicates.Note differences in y -axis scaling.Pyrolysis products plotted in PC1–PC2space (PCA).THB,trihydroxybenzene;dihydroxybenzene;PAH,polycyclic aromatic hydrocarbon.Arrow indicates trend in pyrolysis patterns with increasing charring temperature.The sample charred at200°C gave a pyrogram similar to that of uncharred CT,indicating limited thermal rearrangement at this temperature(Fig.2).At T CHAR300°C,the proportion of THB de-creased from ca.20%to ca.5%of the TQPA,while the proportion of DHB increased towards ca.70%(Fig.3).This reflects elimination of one OH from the prodelphinidin B ring during charring,causing a relative increase in the contribution of DHB to the pyrolyzate. Thus,the presence of DHB in pyrolyzates does not necessarily indi-cate the presence of uncharred CT.This sheds new light on results from previous studies(Quénéa et al.,2005a,b)in which the pres-ence of DHB in the pyrolyzate of BC-containing forest soil was interpreted as being from uncharred CT,whereas it may alterna-tively originate from CT-derived BC.A more drastic shift in pyro-lyzate composition occurred at T CHAR350°C:the relative abundance of DHB diminished,with a concomitant increase in phenols(from ca.10%to50%),as well as benzenes,PAH and other compounds(Fig.3).Also,the relative contribution of THB de-creased further.The results are indicative of strong B ring dehydr-oxylation at350°C.At T CHAR400°C,a further decrease in DHB contribution and increased relative abundance of benzenes and PAH were observed.The high biphenyl/naphthalene ratio may be specific for the pyrolyzate of CT-derived BC,as it is usually much lower in the pyrolyzate of char obtained from lignocellulose(Kaal et al.,2009).At T CHAR450°C,phenols decreased while the relative abundance of benzenes increased towards60%and that of PAHs to-wards10%,suggesting the loss of most of the OH groups from theB Fig.5.Total ion chromatograms of uncharred(control)and charred(200–600°C)CT,from THM–GC–MS.ring.The relatively weak signal for this sample (Table 1;Fig.2)sug-gested that a significant proportion of the CT was converted to non-pyrolyzable polycondensed aromatics.After charring at 600°C the phenolic pyrolysis products and the possible products of the C ring (acetylacetone,acetone and acetic acid)were absent,while the benzenes and PAH had increased to 75%and 20%,respec-tively (Fig.3).This combination constitutes a typical set of pyroly-sis products from strongly charred biomass (Kaal et al.,2009;Fabbri et al.,2012).The general trends for experimental charring of CT as deter-mined with Py–GC–MS became apparent with PCA.In Fig.4,the pyrolysis products are plotted in PC1–PC2space.PC1explained 62%of the total variance and PC222%.PC1and PC2reflect the same process however,namely thermally-induced dehydroxylation:benzenes and PAH had positive loadings on PC1(recording increas-ing abundance with increasing T CHAR )while DHB and THB had neg-ative loadings (compounds showing an opposite trend of decreasing abundance with increasing T CHAR ).PC2separated the phenols from the other pyrolysis products:the phenols had a small contribution to the pyrolyzate at the lower and highest tempera-tures,while they dominated the pyrolyzates of the samples charred between 350and 400°C.The arrow in Fig.4represents the dehydroxylation pathway of CT with increasing T CHAR .The pro-cess is reflected in the THB/DHB,DHB/phenol and phenol/benzene ratios (not shown),which decreased significantly with increasing T CHAR (P <0.001for all ratios).Under the experimental conditions of the present study,the thermal modification of the CT B ring oc-curred predominantly between 300and 400°C.3.3.Charred condensed tannin composition:THM–GC–MSTHM–GC–MS total ion chromatograms are depicted in Fig.5.Similar to TQPA from Py–GC–MS,TQPA decreased with increasing T CHAR (Table 1).The THM products are listed in Table 3,with corresponding relative contributions to TQPA.The likely origin of the THM products was identified on the basis of the substitution pattern of the functional groups.As such,the THM products were grouped according to the number of O-containing functional groups (OFG).Furthermore,trimethoxybenzenes with the methoxyl groups in the m positions (methylated phloroglucinol derivatives)were assumed to originate from A ring moieties,while the trimethoxybenzenes with the methoxyl groups in the o positions (methylated pyrogallol derivatives)were assumed to originate from prodelphinidin B ring moieties.For the uncharred CT,major products from the A ring were 1,3,5-trimethoxybenzene and 2-methyl-1,3,5-trimethoxybenzene,while procyanidin and prodelphinidin B ring products were pres-ent mainly as methyl esters of 3,4-dimethoxybenzoic acid and 3,4,5-trimethoxybenzoic acid,respectively.These compounds have been found to be the dominant THM products of CT isolated from various plant species (Nierop et al.,2005).The presence of A ring products and absence of CH 2-bridged diaromatic (i.e.diphenylme-thane-based)products suggests that CT was readily depolymerized during THM.The exact location of depolymerization is unknown because it cannot be elucidated whether the Me group in 2-methyl-1,3,5-trimethoxybenzene originated from the C-4carbon in the same monomer or from a C-4carbon in the C ring of an adja-cent monomer.The fact that uncharred CT produced no detectable intermonomeric THM products implies that charring-induced depolymerization cannot be studied either.Parameters used by Nierop et al.(2005)to indicate the %of procyanidin B rings of CT were ‘‘PC-acid’’(dimethoxybenzoic acid,methyl ester/sum di-and trimethoxybenzoic acids,methyl esters;26.9%)and ‘‘PC-THM’’(based on all compounds related to di-and trihydroxy B rings;36.2%),are 49.4%and 34.2%,respectively,for the (uncharred)CT used isolated from Corsican pine used here.The cause of the large difference in the ‘‘PC-acid’’parameter may be of an analytical nature.The fact that the ‘‘PC-THM’’values,which were often closer to those determined with NMR (Nierop et al.,2005),were similar suggests that this parameter to estimate the %procyanidin B rings from THM–GC–MS is reproducible.Analogous to Py–GC–MS,the THM–GC–MS pattern from the CT charred at 200°C was similar to the uncharred CT (Fig.5).At T CHAR 300°C,a major decline was observed for 1,3,5-trimethoxybenzene and 2-methyl-1,3,5-trimethoxybenzene from the A ring (Fig.6),which coincided with an increase in relative contribution of most of the products with two or three adjacent methoxyl groups de-rived from CT B-rings.This is suggestive of a greater thermalstabil-Relative proportion (%of TQPA)of THM product groups from CT vs.charring temperature (200–600°C).0°C,control (uncharred CT);OFG refers to number containing functional groups;PAH,polycyclic aromatic hydrocarbon.Note differences in y -axis scaling.ity of B rings than A rings.Between T CHAR300and400°C,the rela-tive contribution of compounds with three and four OFG de-creased,that of two OFG maximized,while that of compounds with only one OFG increased.The trend was especially strong for the compounds with three o methoxyl groups,suggesting thor-ough thermal rearrangement of prodelphinidin B rings in this tem-perature range.At higher charring temperatures,the proportions of benzene,alkyl benzenes and PAH increased strongly,while the proportions of the other compounds decreased.Like the benzenes, benzoic acid methyl ester increased progressively with increasing T CHAR,but it is not clear whether the carboxylic group was formed upon oxidation during the charring experiment or upon Cannizz-aro reactions during THM(Hatcher and Minard,1995;Tanczos et al.,1997).Relatively intact CT A ring products were still recog-nized at T CHAR450°C(R1,3,5-trimethoxybenzenes>10%of TQPA), suggesting that THM–GC–MS might allow unequivocal identifica-tion of CT markers in weak/moderately charred BC.McKinney et al.(1996)identified these THM products from cutan isolated from Agave americana.Apart from its presence in CAM plants only (Boom et al.,2005),a possible interference from cutan-derived 1,3,5-trimethoxybenzenes would be recognized by the presence of methylated aliphatic compounds including fatty acid methyl es-ters.More importantly,these1,3,5-trimethoxybenzenes are not formed upon THM of lignin(e.g.Chefetz et al.,2002;Nierop and Filley,2008;Shadkami and Helleur,2010),a more likely interfering component in plant-derived BC.No O-substituted PAH such as methoxynaphthalenes were de-tected,suggesting that thorough elimination of functional groups preceded the polycondensation reactions.Finally,methylated ben-zene polycarboxylic acids(with three or more carboxyl groups) found among the THM products of aged charcoal(Kaal et al., 2008)were not detected,probably because the necessary oxidation reactions occur during aging in soil and not during heat treatment under limited O2availability.The PC1(58%)–PC2(22%)plot of the THM products showed a similar distribution according to hydrox-ylation pattern(Fig.7).The arrow indicates the progressive loss of OFG with increasing T CHAR.Unsurprisingly,the main difference between Py–GC–MS and THM–GC–MS was the higher abundance of OFG among THM prod-ucts,independent of charring intensity,confirming the protection of functional groups resulting from TMAH derivatization and the loss and/or poor detection of polar compounds using conventional Py–GC–MS.4.ConclusionsThe charring of CT caused progressive dehydroxylation at T CHAR6400°C(under the conditions of the present study)and polyaromatization in the higher temperature range at T CHAR400–600°C.Based on Py–GC–MS,it is suggested that pyrogallol and, more tentatively,catechol derivatives may act as indicators of CT-derived BC formed at low temperature,while a high relative abundance of biphenyl might be indicative of a significant CT con-tribution in more severely charred material.Py–GC–MS is not suit-able for detection of A ring products.From THM–GC–MS,initial A ring degradation occurred at lower temperatures than B ring deg-radation.Nonetheless,the significant contribution of1,3,5-tri-methoxybenzenes from the phloroglucinol A ring up to T CHAR 450°C suggested that these compounds can be used to distinguish between lignin and CT-derived BC in weakly/moderately charred BC samples.The results show that CT is a possible source of pheno-lic moieties in BC and provide a framework for estimating the de-gree of thermal degradation of CT based on the functional group distribution of Py–GC–MS and THM–GC–MS products.Incubation experiments using this CT are currently being developed,aimed at determining the effects of CT charred at different temperatures on organic matter mineralization.AcknowledgmentsWe thank Carmen Pérez Llaguno(Universidade de Santiago de Compostela)for elemental analysis and two anonymous reviewers for their time and comments.Associate Editor—S.DerenneReferencesBaldock,J.A.,Smernik,R.J.,2002.Chemical composition and bioavailability of thermally altered Pinus resinosa(red pine)anic Geochemistry33, 1093–1109.Boom,A.,Sinninghe Damsté,J.S.,De Leeuw,J.W.,2005.Cutan,a common aliphatic biopolymer in cuticles of drought-adapted anic Geochemistry36, 595–601.Braadbaart,F.,Boon,J.J.,Veld,H.,David,P.,Van Bergen,P.F.,boratory simulations of the transformation of peas as a result of heat treatment:changes of the physical and chemical properties.Journal of Archaeological Science31, 821–833.Challinor,J.M.,2001.Review:the development and applications of thermally assisted hydrolysis and methylation reactions.Journal of Analytical and Applied Pyrolysis61,3–34.Chefetz, B.,Salloum,M.J.,Deshmukh, A.P.,Hatcher,P.G.,2002.Structural components of humic acids as determined by chemical modifications and13C NMR,pyrolysis-,and thermochemolysis–gas chromatography/mass spectrometry.Soil Science Society of America Journal66,1159–1171.De la Rosa,J.M.,Knicker,H.,López-Capel,E.,Manning,D.A.C.,González-Pérez,J.A., González-Vila,F.J.,2008.Direct detection of black carbon in soils by py–GC–MS, 13C NMR spectroscopy and thermogravimetric techniques.Soil Science Society of America Journal72,258–267.Fabbri, D.,Torri, C.,Spokas,K.A.,2012.Analytical pyrolysis of synthetic chars derived from biomass with potential agronomic application(biochar).Relationships with impacts on microbial carbon dioxide production.Journal of Analytical and Applied Pyrolysis93,77–84.Fierer,N.,Schimel,J.P.,Cates,R.G.,Zou,J.,2001.Influence of balsam poplar tannin fractions on carbon and nitrogen dynamics in Alaskan taigafloodplain soils.Soil Biology and Biochemistry33,1827–1839.Filley,T.R.,Nierop,K.G.J.,Wang,Y.,2006.The contribution of polyhydroxyl aromatic compounds to tetramethylammonium hydroxide lignin-based anic Geochemistry37,711–727.Galletti,G.C.,Reeves,J.B.,1992.Pyrolysis/gas chromatography/ion-trap detection of polyphenols(vegetable tannins):preliminary anic Mass Spectrometry27,226–230.Galletti,G.C.,Modafferi,V.,Poiana,M.,Bocchini,P.,1995.Analytical pyrolysis and thermally assisted hydrolysis–methylation of wine tannin.Journal of Agricultural and Food Chemistry43,1859–1863.González-Pérez,J.A.,González-Vila,F.J.,Almendros,G.,Knicker,H.,2004.The effect offire on soil organic matter–a review.Environment International30,855–870.THM products plotted in PC1–PC2space(from PCA).OFG refers to numberO-containing functional groups;PAH,polycyclic aromatic hydrocarbon.Theindicates the major trend in dominant THM products with increasing charringtemperature.47(2012)99–108107。

常用ASCII码对照表1. ASCII码在计算机内部，所有的信息最终都表示为一个二进制的字符串。

每一个二进制位（bit）有0和1两种状态，因此八个二进制位就可以组合出256种状态，这被称为一个字节（byte）。

也就是说，一个字节一共可以用来表示256种不同的状态，每一个状态对应一个符号，就是256个符号，从0000000到。

上个世纪60年代，美国制定了一套字符编码，对英语字符与二进制位之间的关系，做了统一规定。

这被称为ASCII码，一直沿用至今。

ASCII码一共规定了128个字符的编码，比如空格“SPACE”是32（十进制的32，用二进制表示就是00100000），大写的字母A是65（二进制01000001）。

这128个符号（包括32个不能打印出来的控制符号），只占用了一个字节的后面7位，最前面的1位统一规定为0。

2、非ASCII编码英语用128个符号编码就够了，但是用来表示其他语言，128个符号是不够的。

比如，在法语中，字母上方有注音符号，它就无法用ASCII码表示。

于是，一些欧洲国家就决定，利用字节中闲置的最高位编入新的符号。

比如，法语中的é的编码为130（二进制）。

这样一来，这些欧洲国家使用的编码体系，可以表示最多256个符号。

但是，这里又出现了新的问题。

不同的国家有不同的字母，因此，哪怕它们都使用256个符号的编码方式，代表的字母却不一样。

比如，130在法语编码中代表了é，在希伯来语编码中却代表了字母Gimel ()，在俄语编码中又会代表另一个符号。

但是不管怎样，所有这些编码方式中，0—127表示的符号是一样的，不一样的只是128—255的这一段。

至于亚洲国家的文字，使用的符号就更多了，汉字就多达10万左右。

一个字节只能表示256种符号，肯定是不够的，就必须使用多个字节表达一个符号。

比如，简体中文常见的编码方式是GB2312，使用两个字节表示一个汉字，所以理论上最多可以表示256x256=65536个符号。

ASCII码对照表2009-04-23 19:43ASCII（American Standard Code for Information Interchange）定义从 0 到127 的共128个数字所代表的英文字母或一样的结果与意义。

由于使用7个位(bit)就可以表示从0到127的数字，大部分的电脑都使用8个位来存取字元集(character set)，所以从128到255之间的数字可以用来代表另一组128个符号，称为extended ASCII。

目前计算机中用得最广泛的字符集及其编码，是由美国国家标准局(ANSI)制定的ASCII码（American Standard Code for Information Interchange，美国标准信息交换码），它已被国际标准化组织（ISO）定为国际标准，称为ISO 646标准。

适用于所有拉丁文字字母，ASCII码有7位码和8位码两种形式。

因为1位二进制数可以表示（21=）2种状态： 0、1；而2位二进制数可以表示（22）=4种状态：00、01、10、11；依次类推，7位二进制数可以表示（27=）128种状态，每种状态都唯一地编为一个7位的二进制码，对应一个字符（或控制码），这些码可以排列成一个十进制序号0～127。

所以，7位ASCII码是用七位二进制数进行编码的，可以表示128个字符。

第0～32号及第127号(共34个)是控制字符或通讯专用字符，如控制符：LF（换行）、CR（回车）、FF（换页）、DEL（删除）、BEL（振铃）等；通讯专用字符：SOH（文头）、EOT（文尾）、ACK（确认）等；第33～126号(共94个)是可打印字符，其中第48～57号为0～9十个阿拉伯数字；65～90号为26个大写英文字母，97～122号为26个小写英文字母，其余为一些标点符号、运算符号等。

注意：在计算机的存储单元中，一个ASCII码值占一个字节(8个二进制位)，其最高位(b7)用作奇偶校验位。

最全ASCII码对照表2009-04-15 00:00Bin Dec Hex 缩写/字符解释0000 0000 0 00 NUL (null) 空字符0000 0001 1 01 SOH (start of handing) 标题开始0000 0010 2 02 STX (start of text) 正文开始0000 0011 3 03 ETX (end of text) 正文结束0000 0100 4 04 EOT (end of transmission) 传输结束0000 0101 5 05 ENQ (enquiry) 请求0000 0110 6 06 ACK (acknowledge) 收到通知0000 0111 7 07 BEL (bell) 响铃0000 1000 8 08 BS (backspace) 退格0000 1001 9 09 HT (horizontal tab) 水平制表符0000 1010 10 0A LF (NL line feed, new line) 换行键0000 1011 11 0B VT (vertical tab) 垂直制表符0000 1100 12 0C FF (NP form feed, new page) 换页键0000 1101 13 0D CR (carriage return) 回车键0000 1110 14 0E SO (shift out) 不用切换0000 1111 15 0F SI (shift in) 启用切换0001 0000 16 10 DLE (data link escape) 数据链路转义0001 0001 17 11 DC1 (device control 1) 设备控制1 0001 0010 18 12 DC2 (device control 2) 设备控制2 0001 0011 19 13 DC3 (device control 3) 设备控制3 0001 0100 20 14 DC4 (device control 4) 设备控制4 0001 0101 21 15 NAK (negative acknowledge) 拒绝接收0001 0110 22 16 SYN (synchronous idle) 同步空闲0001 0111 23 17 ETB (end of trans. block) 传输块结束0001 1000 24 18 CAN (cancel) 取消0001 1001 25 19 EM (end of medium) 介质中断0001 1010 26 1A SUB (substitute) 替补0001 1011 27 1B ESC (escape) 溢出0001 1100 28 1C FS (file separator) 文件分割符0001 1101 29 1D GS (group separator) 分组符0001 1110 30 1E RS (record separator) 记录分离符0001 1111 31 1F US (unit separator) 单元分隔符0010 0000 32 20 空格0010 0001 33 21 !0010 0010 34 22 "0010 0011 35 23 #0010 0100 36 24 $0010 0101 37 25 %0010 0110 38 26 &0010 0111 39 27 '0010 1000 40 28 (0010 1001 41 29 )0010 1101 45 2D - 0010 1110 46 2E . 0010 1111 47 2F / 0011 0000 48 30 0 0011 0001 49 31 1 0011 0010 50 32 2 0011 0011 51 33 3 0011 0100 52 34 4 0011 0101 53 35 5 0011 0110 54 36 6 0011 0111 55 37 7 0011 1000 56 38 8 0011 1001 57 39 9 0011 1010 58 3A : 0011 1011 59 3B ; 0011 1100 60 3C < 0011 1101 61 3D = 0011 1110 62 3E > 0011 1111 63 3F ? 0100 0000 64 40 @ 0100 0001 65 41 A 0100 0010 66 42 B 0100 0011 67 43 C 0100 0100 68 44 D 0100 0101 69 45 E 0100 0110 70 46 F 0100 0111 71 47 G 0100 1000 72 48 H 0100 1001 73 49 I 0100 1010 74 4A J 0100 1011 75 4B K 0100 1100 76 4C L 0100 1101 77 4D M 0100 1110 78 4E N 0100 1111 79 4F O 0101 0000 80 50 P 0101 0001 81 51 Q 0101 0010 82 52 R 0101 0011 83 53 S 0101 0100 84 54 T 0101 0101 85 55 U 0101 0110 86 56 V 0101 0111 87 57 W 0101 1000 88 58 X0101 1100 92 5C \0101 1101 93 5D ]0101 1110 94 5E ^0101 1111 95 5F _0110 0000 96 60 `0110 0001 97 61 a0110 0010 98 62 b0110 0011 99 63 c0110 0100 100 64 d0110 0101 101 65 e0110 0110 102 66 f0110 0111 103 67 g0110 1000 104 68 h0110 1001 105 69 i0110 1010 106 6A j0110 1011 107 6B k0110 1100 108 6C l0110 1101 109 6D m0110 1110 110 6E n0110 1111 111 6F o0111 0000 112 70 p0111 0001 113 71 q0111 0010 114 72 r0111 0011 115 73 s0111 0100 116 74 t0111 0101 117 75 u0111 0110 118 76 v0111 0111 119 77 w0111 1000 120 78 x0111 1001 121 79 y0111 1010 122 7A z0111 1011 123 7B {0111 1100 124 7C |0111 1101 125 7D }0111 1110 126 7E ~0111 1111 127 7F DEL (delete) 删除ESC键VK_ESCAPE (27)回车键：VK_RETURN (13)TAB键：VK_TAB (9)Caps Lock键：VK_CAPITAL (20)Shift键：VK_SHIFT ()Ctrl键：VK_CONTROL (17)Alt键：VK_MENU (18)空格键：VK_SPACE (/32)退格键：VK_BACK (8)左徽标键：VK_LWIN (91)右徽标键：VK_LWIN (92)鼠标右键快捷键：VK_APPS (93) Insert键：VK_INSERT (45) Home键：VK_HOME (36) Page Up：VK_PRIOR (33) PageDown：VK_NEXT (34)End键：VK_END (35)Delete键：VK_DELETE (46)方向键(←)：VK_LEFT (37)方向键(↑)：VK_UP (38)方向键(→)：VK_RIGHT (39)方向键(↓)：VK_DOWN (40)F1键：VK_F1 (112)F2键：VK_F2 (113)F3键：VK_F3 (114)F4键：VK_F4 (115)F5键：VK_F5 (116)F6键：VK_F6 (117)F7键：VK_F7 (118)F8键：VK_F8 (119)F9键：VK_F9 (120)F10键：VK_F10 (121)F11键：VK_F11 (122)F12键：VK_F12 (123)Num Lock键：VK_NUMLOCK (144) 小键盘0：VK_NUMPAD0 (96) 小键盘1：VK_NUMPAD0 (97) 小键盘2：VK_NUMPAD0 (98) 小键盘3：VK_NUMPAD0 (99) 小键盘4：VK_NUMPAD0 (100) 小键盘5：VK_NUMPAD0 (101) 小键盘6：VK_NUMPAD0 (102) 小键盘7：VK_NUMPAD0 (103) 小键盘8：VK_NUMPAD0 (104) 小键盘9：VK_NUMPAD0 (105) 小键盘.：VK_DECIMAL (110) 小键盘*：VK_MULTIPLY (106) 小键盘+：VK_MULTIPLY (107) 小键盘-：VK_SUBTRACT (109) 小键盘/：VK_DIVIDE (111) Pause Break键：VK_PAUSE (19) Scroll Lock键：VK_SCROLL (145)。