土壤團(tuán)聚體制備方法對(duì)其穩(wěn)定性及固碳潛力評(píng)價(jià)的影響研究

鄭 楠,邵 陽(yáng),羅 敏,孟丹陽(yáng),徐殿斗,劉志明,馬玲玲*

土壤團(tuán)聚體制備方法對(duì)其穩(wěn)定性及固碳潛力評(píng)價(jià)的影響研究

鄭 楠1,2,邵 陽(yáng)2,羅 敏2,孟丹陽(yáng)1,2,徐殿斗2,劉志明1,馬玲玲2*

(1.北京化工大學(xué)化學(xué)工程學(xué)院,化工資源有效利用國(guó)家重點(diǎn)實(shí)驗(yàn)室,北京 100029；2.中國(guó)科學(xué)院高能物理研究所,北京市射線成像技術(shù)與裝備工程技術(shù)研究中心,北京 100049)

為探討不同土壤團(tuán)聚體制備方法對(duì)評(píng)價(jià)城市土壤固碳潛力的影響,本研究采集北京市兩種典型的不同利用類(lèi)型土壤—城市綠地土壤和城郊農(nóng)田土壤,分別采用干篩法和濕篩法制備土壤團(tuán)聚體,對(duì)其團(tuán)聚體組成、有機(jī)碳含量以及穩(wěn)定碳同位素特征進(jìn)行了解析.結(jié)果表明:干篩法制備的機(jī)械穩(wěn)定性團(tuán)聚體均以>0.25mm的大團(tuán)聚體為主(城市綠地土壤:69.80%;農(nóng)田土壤:71.36%);而濕篩法制備的水穩(wěn)性團(tuán)聚體均以<0.25mm微團(tuán)聚體為主(城市綠地土壤:57.70%;農(nóng)田土壤:52.14%).紅外光譜解析發(fā)現(xiàn),不同制備方法下,兩類(lèi)土壤中微團(tuán)聚體中均是穩(wěn)定有機(jī)碳比活性有機(jī)碳相對(duì)含量高;北京城郊農(nóng)田土壤中穩(wěn)定芳香碳的相對(duì)含量較多,而脂肪碳相對(duì)含量較少;城市綠地土壤則具有相反特征,說(shuō)明城市綠地土壤中有機(jī)碳具有更高活性易在一定條件下被釋放.結(jié)合穩(wěn)定碳同位素比值解析發(fā)現(xiàn),濕篩制備方法下13C在<0.053mm團(tuán)聚體顆粒組中富集,更符合土壤團(tuán)聚體胚胎發(fā)育模型,說(shuō)明在土壤固碳潛力研究中,濕篩法比干篩法制備團(tuán)聚體更具有實(shí)際評(píng)價(jià)價(jià)值,本研究為進(jìn)一步評(píng)價(jià)我國(guó)城市土壤的固碳潛力具有參考意義.

團(tuán)聚體顆粒組；土壤有機(jī)碳；碳穩(wěn)定同位素；干篩法；濕篩法

土壤是陸地生態(tài)系統(tǒng)中最大的有機(jī)碳庫(kù)[1],土壤有機(jī)碳庫(kù)微小的變化將導(dǎo)致大氣CO2濃度的劇烈波動(dòng)[2].土壤有機(jī)碳(soil organic carbon, SOC)是影響其結(jié)構(gòu)、水分含量和變化及其離子交換容量的決定因子,增加土壤有機(jī)碳含量不僅有利于維持土壤養(yǎng)分和農(nóng)業(yè)發(fā)展[3],而且有利于降低土壤CO2釋放,進(jìn)而減緩溫室效應(yīng)[4].

土壤團(tuán)聚體是土壤有機(jī)碳形成和轉(zhuǎn)化的重要載體[2,5],其穩(wěn)定性也是預(yù)測(cè)土壤水分流失和抗侵蝕能力的重要指標(biāo)[6].土壤團(tuán)聚體中有機(jī)碳的數(shù)量和質(zhì)量各不相同,因?yàn)椴煌降膱F(tuán)聚體可能具有不同的質(zhì)地和孔隙度[7].土壤團(tuán)聚體根據(jù)其粒徑大小可以分為大團(tuán)聚體(>250μm)和微團(tuán)聚體(<250μm),各團(tuán)聚體間可進(jìn)一步細(xì)分為粗大團(tuán)聚體(>2000μm)、細(xì)大團(tuán)聚體(2000～250μm)和微團(tuán)聚體(250～53μm)和粉-黏團(tuán)聚體(<53μm)[8];也可根據(jù)其抗外力作用分為穩(wěn)定性團(tuán)聚體和非穩(wěn)性團(tuán)聚體[6].土壤團(tuán)聚作用效應(yīng)大小的關(guān)鍵是其中有機(jī)碳的滯留時(shí)間和降解速度,同時(shí)土壤有機(jī)碳的變化也受到土壤團(tuán)聚體結(jié)構(gòu)的調(diào)控[9].因此,明確團(tuán)聚體的形成和周轉(zhuǎn)模式是理解和研究土壤SOC動(dòng)態(tài)及團(tuán)聚體中SOC固定機(jī)理的基礎(chǔ)[10].

團(tuán)聚體顆粒的分離是探究其性狀結(jié)構(gòu)首要的一步,干篩法和濕篩法在土壤團(tuán)聚體分離中得到了廣泛的應(yīng)用[11-12].干篩法測(cè)定的是原狀土壤機(jī)械穩(wěn)定性團(tuán)聚體含量,由于其對(duì)土壤中瞬變性和臨時(shí)性的有機(jī)膠結(jié)物質(zhì)的破壞較小,能夠反映土壤團(tuán)聚體在自然狀態(tài)下的分布特征.濕篩法測(cè)定的是土壤水穩(wěn)性團(tuán)聚體含量,可以反映土壤潛在的抗水蝕能力.祁迎春等[13]研究認(rèn)為,干篩法對(duì)土壤中微生物群落破壞作用較小,而濕篩法由于離子水合作用或水溶性有機(jī)質(zhì)的存在會(huì)使土壤團(tuán)聚體被破壞,干篩法可能優(yōu)于濕篩法.姜敏等[14]則認(rèn)為,濕篩法比干篩法更能準(zhǔn)確地重現(xiàn)土壤團(tuán)聚體的穩(wěn)定性及土壤的抗侵蝕能力.Liu等[15]在探究水稻土中碳同位素豐度變化與團(tuán)聚體周轉(zhuǎn)之間關(guān)系時(shí)采用濕篩法制備土壤團(tuán)聚體,研究發(fā)現(xiàn)微團(tuán)聚體(<0.25mm)的δ13C值高于大團(tuán)聚體(>0.25mm).前人關(guān)于土壤團(tuán)聚體固碳潛力的研究[16-19]主要集中于土壤團(tuán)聚體粒徑大小和有機(jī)碳分布行為之間的關(guān)系,但鮮見(jiàn)針對(duì)不同分離方法對(duì)不同利用類(lèi)型土壤團(tuán)聚體組成和結(jié)構(gòu)變化及有機(jī)碳固存特征的影響研究.隨著碳中和目標(biāo)實(shí)施的推進(jìn),城市綠化土壤及城郊農(nóng)業(yè)土壤的固碳作用受到越來(lái)越多的關(guān)注.

因此,本文以北京市城市綠地土壤和郊區(qū)農(nóng)田土壤兩種不同土地利用類(lèi)型的土壤為研究對(duì)象,比較不同制備方法中土壤團(tuán)聚體穩(wěn)定性及組成差異,結(jié)合碳同位素比解析及紅外光譜表征等方法來(lái)探究團(tuán)聚體分離方法對(duì)不同土壤團(tuán)聚體有機(jī)碳含量和碳同位素值分布行為的影響,研究將為進(jìn)一步采用有效的土壤固碳潛力評(píng)價(jià)提供一定的科學(xué)依據(jù).

1 材料與方法

1.1 供試材料

北京屬暖溫帶半濕潤(rùn)大陸性季風(fēng)氣候,四季分明,年降水400～750mm,降水主要集中在夏季7、8月份,地帶性土壤類(lèi)型主要是褐土.本試驗(yàn)將位于北京市石景山區(qū)的城市綠地土壤(39°54.4931′N(xiāo),116°14.8082′E)以及海淀區(qū)的郊區(qū)農(nóng)田土壤(40°05.5634′N(xiāo), 116°11.5498′E)作為供試材料,各取樣點(diǎn)土壤質(zhì)地按國(guó)際制標(biāo)準(zhǔn)劃分全為粉粘土.兩種不同利用類(lèi)型的土壤選擇多個(gè)采樣點(diǎn)各采集表層0～20cm土壤混合樣品約1kg,混合后進(jìn)行四分法取舍后裝袋并剔除粗根和石塊,于自然通風(fēng)處風(fēng)干后裝袋保存?zhèn)溆?土壤pH測(cè)定采用電位法,土壤含水量測(cè)定采用重量法,土壤有機(jī)碳和全氮采用穩(wěn)定同位素比質(zhì)譜儀測(cè)定,土壤全磷和全鉀采用微波消解ICP-OES法測(cè)定[20].供試土壤基本理化性質(zhì)如表1所示.

表1 供試土壤基本理化性質(zhì)

干篩法制備機(jī)械穩(wěn)定性土壤團(tuán)聚體顆粒組:分別取適量土樣在振篩機(jī)上篩分15min,得到粒徑>2mm、2～1mm、1～0.25mm、0.25～0.053mm和<0.053mm五個(gè)團(tuán)聚體顆粒組,測(cè)定各孔徑篩子上土樣重量,計(jì)算各級(jí)團(tuán)聚體的粒徑和分布.

濕篩法制備水穩(wěn)定性土壤團(tuán)聚體顆粒組:在盛有適量水的沉降筒中放置10目、18目、60目和270目孔徑的套篩組,將最上層篩子放置的土壤在水中浸潤(rùn)5min后,以每min30次的頻率震動(dòng)3min.靜置5min后用水仔細(xì)的沖洗每一層篩面,將沖洗后的懸濁液收集到燒杯中,充分沉降后冷凍干燥,稱(chēng)量以計(jì)算各級(jí)團(tuán)聚體的粒徑和分布.

1.2 研究方法

土壤團(tuán)聚體有機(jī)碳官能團(tuán)表征:壓片前將各粒徑團(tuán)聚體樣品放置在60℃烘箱中8h,分別稱(chēng)取1.50mg的樣品和150mg的光譜純KBr混合研磨、壓片,進(jìn)行紅外光譜測(cè)定(美國(guó)Nicolet 5PC紅外光譜儀).分辨率4cm-1,波譜范圍4000～400cm-1,數(shù)據(jù)分析采用Omnic version 8.2進(jìn)行紅外譜圖解析以及吸收峰面積統(tǒng)計(jì)解析.

土壤團(tuán)聚體有機(jī)碳含量及同位素測(cè)定[21]:分別稱(chēng)取0.5g的過(guò)100目篩的土壤樣品于50mL離心管中,加入1mol/L鹽酸混勻,于恒溫振蕩器上在室溫下震蕩24h,然后用去離子水將土壤樣品洗至中性,于烘箱中60℃下烘至恒重,研磨后采用穩(wěn)定同位素比質(zhì)譜儀測(cè)定(美國(guó)Thermo.Co公司型號(hào)為MAT 253Plus),每個(gè)樣品重復(fù)測(cè)定3次,保證空白和平行樣品的相對(duì)標(biāo)準(zhǔn)偏差均在5%以下.

1.3 數(shù)據(jù)處理

平均重量直徑(MWD)和幾何平均直徑(GMD)的計(jì)算公式分別為[22]:

式中:w為各粒徑團(tuán)聚體的質(zhì)量百分?jǐn)?shù),%;X為各粒徑團(tuán)聚體的平均直徑,mm.

為了確定土壤的穩(wěn)定性,團(tuán)聚體破壞率(PAD)采用干法和濕法篩分相結(jié)合的方法確定,公式如下[23]:

式中:DR0.25為干篩法>0.25mm機(jī)械穩(wěn)定性團(tuán)聚體的百分率(%),WR0.25為濕篩法>0.25mm水穩(wěn)定性團(tuán)聚體的百分率(%).

δ13值計(jì)算公式如下:

式中:samp和stand分別為土壤樣品以及標(biāo)準(zhǔn)樣品的13C/12C值.

2 結(jié)果與討論

2.1 土壤團(tuán)聚體組成特征

如圖1所示,城市綠地土壤和農(nóng)田土壤中干篩法所得的機(jī)械穩(wěn)定性團(tuán)聚體均以大團(tuán)聚體(>0.25mm)為主.但兩種土壤組成結(jié)構(gòu)存在差異,其中農(nóng)田土壤>2mm團(tuán)聚體顆粒組所占比例約為城市綠地土壤的3.4倍.兩種土壤濕篩法水穩(wěn)定性團(tuán)聚體粒級(jí)分布基本一致,即0.25～0.053mm團(tuán)聚體顆粒組所占比例最高(均在41%之上).姜敏等[14]分別采用干篩法和濕篩法測(cè)定丹江口庫(kù)區(qū)土壤團(tuán)聚體組成,研究表明干篩條件下土壤大團(tuán)聚體(>5mm)含量均達(dá)到50%以上,而濕篩條件下<0.1mm和0.25～1mm團(tuán)聚體顆粒組所占比例最大,分布在29%～42%之間.朱利霞等[23]對(duì)河南周口市楊樹(shù)和女貞林地土壤研究表明,干篩條件下30.25mm團(tuán)聚體顆粒組所占比例最大,濕篩條件下<0.25mm團(tuán)聚體顆粒組所占比例最大.這可能是由于濕篩法破壞了土壤中非水穩(wěn)性團(tuán)聚體,使其崩解為小粒徑的團(tuán)聚體.本研究中濕篩法下,城市綠地土壤中微團(tuán)聚體含量提高了29.5%,農(nóng)田土壤微團(tuán)聚體含量提高了25.5%.這也說(shuō)明,北京城市綠地土壤和農(nóng)田土壤團(tuán)聚體結(jié)構(gòu)與組成的研究中,不同團(tuán)聚體分離方法對(duì)其研究結(jié)果影響較大.

圖1 干篩和濕篩法土壤團(tuán)聚體組成比例

2.2 土壤團(tuán)聚體穩(wěn)定性分析

一般而言,土壤MWD和GMD值越大,土壤團(tuán)聚體就越穩(wěn)定[24].PAD表示水蝕作用下土壤團(tuán)聚體的分散程度,其值越小,穩(wěn)定性越高.由表2可知,干篩法和濕篩法條件下,農(nóng)田土壤的MWD和GMD值均高于城市土壤.城市綠地土壤和農(nóng)田土壤團(tuán)聚體PAD值分別為39.40%和32.94%,表明供試農(nóng)田土壤團(tuán)聚體的水穩(wěn)性優(yōu)于城市土壤.不同土地利用方式下的土壤中,有效根根量的差異是造成這種不同結(jié)果的重要原因之一.土壤膠結(jié)劑是促進(jìn)團(tuán)聚體形成和穩(wěn)定的關(guān)鍵物質(zhì),可分為土壤有機(jī)質(zhì)、根系菌絲等有機(jī)膠結(jié)劑和黏粒、多價(jià)金屬離子、氧化物等無(wú)機(jī)膠結(jié)劑[6].姚賢良等[25]指出,在人為干擾較少的耕作管理情況下,鐵鋁氧化物以及黏粒對(duì)土壤團(tuán)聚體的膠結(jié)作用可能要大于有機(jī)質(zhì),但經(jīng)過(guò)種植旱作一段時(shí)間后,土壤中的黏粒和無(wú)定形鐵鋁氧化物明顯降低.陳山[26]研究發(fā)現(xiàn),各粒級(jí)團(tuán)聚體中無(wú)論是游離態(tài)鐵鋁氧化物還是非晶型鐵鋁氧化物,均與干篩MWD、濕篩MWD和PAD表現(xiàn)為相關(guān)性不顯著.

表2 土壤團(tuán)聚體穩(wěn)定性評(píng)價(jià)

2.3 土壤團(tuán)聚體有機(jī)碳含量及紅外光譜特征

由表3可知,城市綠地土壤團(tuán)聚體具有較高的土壤有機(jī)碳含量,這可能是因?yàn)槠渲参锷锪枯^高,比農(nóng)田積累了更多的凋落物和地下根系.Zhang等[27]發(fā)現(xiàn)退耕還林還草后土壤有機(jī)碳以36.67g/(m2·a)的速度累積.同時(shí),不論是干篩還是濕篩,土壤有機(jī)碳主要賦存于微團(tuán)聚體中(<0.25mm),<0.053mm粒徑團(tuán)聚體固碳能力高于其他粒級(jí).濕篩法所得較大粒徑(>0.25mm)團(tuán)聚體中有機(jī)碳含量普遍低于干篩,但未達(dá)到顯著性差異水平(<0.05).

土壤的紅外光譜圖可用于鑒定土壤黏土礦物類(lèi)型,3700～3100cm-1為黏土礦物羥基伸縮振動(dòng)譜帶,<1300cm-1的指紋區(qū)是晶格硅氧鍵伸縮振動(dòng)及其它能量較小的羥基彎曲振動(dòng)頻率范圍[28].如圖2所示,城市土壤和農(nóng)田土壤都在3621,3425,1646cm-1處都有明顯吸收峰,是典型的蒙脫石型礦物質(zhì)的特征吸收峰,同時(shí)在3696cm-1處都有小的銳峰,說(shuō)明兩種土壤都含有少量高嶺石.

表3 干篩和濕篩法土壤團(tuán)聚體有機(jī)碳含量及官能團(tuán)相對(duì)含量

注:脂肪C1指脂肪CH3和CH2的C-H伸縮振動(dòng);脂肪C2指脂肪CH3和CH2的變形振動(dòng).

總體來(lái)講,無(wú)論采用干篩法還是濕篩法,城市綠地和農(nóng)田土壤不同粒徑團(tuán)聚體的紅外光譜非常相似,只是吸收強(qiáng)度存在差別,說(shuō)明兩種制備方法下不同粒徑團(tuán)聚體中有機(jī)碳官能團(tuán)和黏土礦物組成沒(méi)有差異,只是有機(jī)碳相對(duì)含量有差異.城市綠地土壤在3000～2800cm-1處有C-H伸縮振動(dòng)的微小吸收峰,并且在1440cm-1處有甲基、亞甲基等烷基C-H變形振動(dòng)的較強(qiáng)吸收峰.農(nóng)田土壤團(tuán)聚體紅外圖譜在碳水化合物的1085cm-1和芳香碳的1635cm-1尖峰處存在較強(qiáng)肩吸收.從表3可知,農(nóng)田土壤各粒徑團(tuán)聚體芳香碳的相對(duì)含量較多,變形振動(dòng)脂肪碳的相對(duì)含量較少;城市土壤則正好相反.兩種制備方法均發(fā)現(xiàn)大團(tuán)聚體中芳香碳的含量普遍小于微團(tuán)聚體;而多糖碳和脂肪碳在大團(tuán)聚體中的含量高于微團(tuán)聚體,這表明相對(duì)于微團(tuán)聚體,大團(tuán)聚體中活性有機(jī)碳相對(duì)含量多而穩(wěn)定有機(jī)碳相對(duì)含量較少,大團(tuán)聚體中的有機(jī)碳更容易受到外部擾動(dòng)的影響.

圖2 干篩和濕篩法土壤團(tuán)聚體紅外光譜解析

a.城市綠地土壤干篩;b.城市綠地土壤濕篩;c.農(nóng)田土壤干篩;d.農(nóng)田土壤濕篩

2.4 土壤團(tuán)聚體碳穩(wěn)定同位素分析

為了進(jìn)一步探討不同團(tuán)聚體分離方法的適用性,理解土壤有機(jī)碳的動(dòng)態(tài)與團(tuán)聚體的周轉(zhuǎn)密切相關(guān),我們對(duì)不同團(tuán)聚體顆粒組的穩(wěn)定碳同位素進(jìn)行了解析.如圖3所示,農(nóng)田土壤團(tuán)聚體中δ13C值較城市綠地土壤更大.這可能是由于兩種表層土壤中植物凋落物與根系分泌物不同,而C3植物δ13C值與C4植物相比更趨向負(fù)值,所以C4植物表層土壤δ13C值更大.

理論上,穩(wěn)定C同位素分餾發(fā)生在植物-土壤系統(tǒng)中碳遷移轉(zhuǎn)化的每一個(gè)步驟,各組分中13C的豐度與物質(zhì)遷移有關(guān)[29].在土壤團(tuán)聚體轉(zhuǎn)化和有機(jī)碳固定過(guò)程中,13C分餾導(dǎo)致后期形成的團(tuán)聚體δ13C值增加.因此,δ13C值較高的團(tuán)聚體可視為低δ13C值團(tuán)聚體的產(chǎn)物.如圖3可示,城市綠地和農(nóng)田土壤濕篩制備團(tuán)聚體中δ13C值分別從-25.42‰到-22.07‰和-21.70‰到-20.01‰變化,隨團(tuán)聚體粒徑的增加而減小,而干篩法制備兩種土壤團(tuán)聚體δ13C值最大值均出現(xiàn)在2～1mm粒徑中.在探究土壤團(tuán)聚體周轉(zhuǎn)過(guò)程中碳同位素分餾特征時(shí),不同團(tuán)聚體分離方法對(duì)其研究結(jié)果影響較大.Li[5]采用濕篩法分離石漠化地區(qū)土壤團(tuán)聚體研究其穩(wěn)定性和固碳潛力,研究表明SMA (1～0.25mm)團(tuán)聚體顆粒組中有機(jī)碳含量最高,而<0.05mm團(tuán)聚體顆粒組中δ13C值最大.曾偉斌等[30]研究丹江口庫(kù)區(qū)不同土地利用土壤碳氮含量,采用濕篩法制備林地、灌木地和農(nóng)田土壤團(tuán)聚體,發(fā)現(xiàn)3種土地利用類(lèi)型下土壤有機(jī)碳含量均以<0.053mm團(tuán)聚體顆粒組最高,δ13C值的大小順序在各粒徑中均為:農(nóng)田>灌木地>林地,且三者差值隨粒徑變小呈減少趨勢(shì).

團(tuán)聚體的胚胎發(fā)育模型認(rèn)為,新鮮有機(jī)質(zhì)加入后會(huì)先和土壤中的小團(tuán)聚體結(jié)合,逐漸形成大團(tuán)聚體,而后大團(tuán)聚體破碎,又會(huì)從中釋放出小團(tuán)聚體.本研究中同位素解析發(fā)現(xiàn)濕篩制備團(tuán)聚體中δ13C值隨粒徑增加而減少,可能是由于濕篩過(guò)程中大團(tuán)聚體有機(jī)質(zhì)膠結(jié)劑分解導(dǎo)致大團(tuán)聚體破碎,穩(wěn)定的微團(tuán)聚體釋放,進(jìn)入下一輪團(tuán)聚體的循環(huán).因此,濕篩法制備土壤團(tuán)聚體來(lái)研究土壤的固碳潛力及影響因素更符合大團(tuán)聚體周轉(zhuǎn)及SOC動(dòng)態(tài)變化規(guī)律.

圖3 干篩和濕篩法土壤團(tuán)聚體的δ13C值

3 結(jié)論

3.1 干篩法制備的機(jī)械穩(wěn)定性團(tuán)聚體均以>0.25mm的大團(tuán)聚體為主(城市綠地土壤:69.80%;農(nóng)田土壤:71.36%);而濕篩法制備的水穩(wěn)性團(tuán)聚體以<0.25mm微團(tuán)聚體為主(城市綠地土壤:57.70%;農(nóng)田土壤52.14%).北京城市綠地土壤和農(nóng)田土壤團(tuán)聚體結(jié)構(gòu)與組成的研究中,不同團(tuán)聚體分離方法對(duì)其研究結(jié)果影響較大.

3.2 兩種篩分方法制備土壤團(tuán)聚體均發(fā)現(xiàn)有機(jī)碳含量隨粒徑減小而增大,微團(tuán)聚體中活性有機(jī)碳相對(duì)含量少而穩(wěn)定有機(jī)碳相對(duì)含量較多.

3.3 干篩法中城市綠地和農(nóng)田土壤團(tuán)聚體的δ13C值最大值均出現(xiàn)在2～1mm團(tuán)聚體顆粒組中;而濕篩法中兩種類(lèi)型土壤的13C均在<0.053mm團(tuán)聚體顆粒組中富集.在探究土壤團(tuán)聚體周轉(zhuǎn)過(guò)程中碳同位素分餾特征時(shí),濕篩法制備土壤團(tuán)聚體能更好地反映土壤中團(tuán)聚體周轉(zhuǎn)及土壤有機(jī)碳動(dòng)態(tài)變化的胚胎發(fā)育模型.因此濕篩法比干篩法制備團(tuán)聚體來(lái)研究其固碳潛力更具有實(shí)際應(yīng)用價(jià)值.

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Effects of soil aggregate preparation methods on the stability and carbon sequestration potential evaluation.

ZHENG Nan1,2, SHAO Yang2, LUO Min2, MENG Dan-yang1,2, XU Dian-dou2, LIU Zhi-ming1, MA Ling-ling2*

(1.State Key Laboratory of Chemical Resources Engineering, College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China；2.Beijing Engineering Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China)., 2022,42(6)：2821～2827

To investigate the effects of different soil agglomerate preparation methods on the evaluation of agglomerate stability and its carbon sequestration potential, soils were collected from two typical land utilization types-urban road soils and suburban agricultural soils in Beijing. The soil aggregate was prepared by dry sieving and wet sieving methods, respectively, and its composition, organic carbon content and stable carbon isotope were analyzed. The mechanically stable aggregates prepared by the dry sieving method were dominated by the large (>0.25mm) aggregates (urban road soils: 69.80%; agricultural soils: 71.36%). In contrast, the water-stable aggregates prepared by the wet sieving method were dominated by the micro (<0.25mm) aggregates (urban road soil: 57.70%; agricultural soil: 52.14%). Infrared spectrum analysis showed that irrespective of the different preparation methods, the relative content of stable organic carbon in micro aggregates was higher than that of active organic carbon for the two types of soils. For the arable soil in the suburbs of Beijing, the relative content of stable aromatic carbon was more, while the relative content of fatty carbon was less. In the case of urban greening soil, the opposite characteristics can be observed, indicating that organic carbon in urban greening soil has higher activity and is easy to be released under certain conditions. Combined with the analysis of stable carbon isotope ratio, it is found that13C is enriched in the aggregate particle group smaller than 0.053mm prepared by the wet sieve method, which is more fitted the soil aggregate embryo development model, indicating that the wet sieve method has more practical evaluation value than the dry sieve method in the study of soil carbon sequestration potential. This study has reference significance for further evaluating the carbon sequestration potential of urban soils in China.

soil aggregates；organic carbon；stable isotope composition；dry sieving method；wet sieving method

X53

A

1000-6923(2022)06-2821-07

鄭 楠(1994-),女,山西太原人,北京化工大學(xué)碩士研究生,主要從事污染物環(huán)境行為研究.

2021-11-17

國(guó)家自然科學(xué)基金資助項(xiàng)目(U1932103,11875266);國(guó)家自然科學(xué)基金重點(diǎn)項(xiàng)目(U1832212,91643206)

* 責(zé)任作者, 研究員, malingling@ihep.ac.cn