雙氰胺、氫醌與含磷添加劑聯(lián)合使用對堆肥溫室氣體排放的影響

楊 燕,李國學(xué),羅一鳴,楊 佳,袁 京

雙氰胺、氫醌與含磷添加劑聯(lián)合使用對堆肥溫室氣體排放的影響

楊 燕,李國學(xué),羅一鳴,楊 佳,袁 京*

(中國農(nóng)業(yè)大學(xué)資源與環(huán)境學(xué)院,農(nóng)田土壤污染防控與修復(fù)北京市重點(diǎn)實(shí)驗(yàn)室,北京 100193)

為實(shí)現(xiàn)堆肥過程N(yùn)2O、CH4和NH3的同步減排,在雙氰胺和氫醌的基礎(chǔ)上進(jìn)一步研究磷石膏和過磷酸鈣添加對豬糞堆肥溫室氣體和NH3排放的影響.以豬糞和玉米秸稈為堆肥原料,設(shè)置3個堆肥處理:只添加雙氰胺和氫醌(HD)、添加雙氰胺、氫醌和磷石膏(HD+P)和添加雙氰胺、氫醌和過磷酸鈣(HD+S),在60L的發(fā)酵罐中進(jìn)行40d的堆肥實(shí)驗(yàn).結(jié)果表明:在雙氰胺和氫醌的基礎(chǔ)上添加磷石膏和過磷酸鈣可提高堆肥腐熟度,降低碳(7.58%～11.33%)和氮(25.03%～33.42%)的損失.3種添加劑聯(lián)用可同步減少15.21%～16.91% NH3和23.75%～38.30% CH4排放,主要是由于含磷添加劑較低的pH值和磷酸成分,可以固定銨態(tài)氮,減少NH3排放,同時硫酸離子會抑制產(chǎn)甲烷菌活性進(jìn)而降低CH4排放.在雙氰胺和氫醌降低N2O排放基礎(chǔ)上,添加含磷添加劑會增加0.14%～20.57% N2O排放,總溫室效應(yīng)降低7.60%～24.30%,其中雙氰胺、氫醌和磷石膏處理總溫室氣體減排效果最佳.

堆肥；雙氰胺；氫醌；含磷添加劑；溫室氣體；氨氣

隨著我國畜牧業(yè)的發(fā)展,畜禽糞污問題愈發(fā)凸顯.據(jù)統(tǒng)計,截止2020年畜禽糞污產(chǎn)量達(dá)到44.28 億t[1],其氮、磷、鉀養(yǎng)分總貯存量約為5323 萬t,占我國目前化肥施用總量的89%[2].好氧堆肥是實(shí)現(xiàn)畜禽糞便無害化、減量化和資源化的綠色方法,可有效地將糞便轉(zhuǎn)化為有機(jī)肥料[3-4].然而,堆肥過程中會產(chǎn)生大量氨氣(NH3)、甲烷(CH4)和氧化亞氮(N2O)等污染氣體,不僅會引起營養(yǎng)元素的損失,而且會造成大氣污染.N2O和CH4均是對溫室效應(yīng)貢獻(xiàn)較大的溫室氣體,其100a溫室效應(yīng)分別是CO2的298倍和25倍[5].堆肥過程中,N2O的產(chǎn)生量約占堆肥初始總氮的0.1%～4.2%[6],CH4的產(chǎn)生量約占堆肥總碳的0.8%～6%[7-8].此外,氨揮發(fā)是堆肥過程氮損失的主要途徑,堆肥過程中的氨揮發(fā)約占堆肥總氮的20%～60%[9-10],在一定程度上造成二次污染.堆肥過程中溫室氣體減排和氮素?fù)p失控制技術(shù)受到越來越多的關(guān)注.

眾多學(xué)者表明,化學(xué)添加劑是減少氮素?fù)p失和控制溫室氣體排放的有效途徑.Weiske等[11]實(shí)驗(yàn)表明,硝化抑制劑雙氰胺(二氰二氨,C2H4N4,縮寫DCD)的施用對土壤N2O排放的抑制效應(yīng)達(dá)70%,3a平均使農(nóng)田土壤的N2O排放下降26%,使草地土壤N2O排放下降40%以上.Jiang等[12]豬糞堆肥表明,在不同時期加入DCD可減少76.1%～77.6% N2O的排放.姜繼韶等[13]在污泥堆肥中添加DCD,結(jié)果表明DCD可以提高堆肥產(chǎn)品的微生物多樣性.氫醌(對苯二酚,C6H6O2)被認(rèn)為是一種經(jīng)濟(jì)有效的脲酶抑制劑[14].有研究認(rèn)為,硝化抑制劑和脲酶抑制劑可被聯(lián)合用于降低土壤系統(tǒng)中氨氣和溫室氣體排放.Boeckx等[15]研究表明,聯(lián)合使用雙氰胺和氫醌可使土壤CH4和N2O的排放率分別降低58%和62%.Xu等[16]在水稻田土壤中聯(lián)合施用雙氰胺和氫醌后,CH4和N2O分別降低51%和47%.雙氰胺和氫醌在農(nóng)田中被廣泛使用,不僅可以減少污染氣體的排放,還可以提高作物對營養(yǎng)元素的吸收,從而提高農(nóng)作物產(chǎn)量[17-18].硝化抑制劑和脲酶抑制劑聯(lián)用在堆肥系統(tǒng)中尚未廣泛應(yīng)用,其主要減少N2O的排放,對NH3減排作用不顯著.

磷酸鹽作為添加劑不僅可被用于減少堆肥NH3揮發(fā),還可提高堆肥產(chǎn)品中的養(yǎng)分元素含量.磷石膏(PG)和過磷酸鈣(SP)作為氮素?fù)p失控制材料還可在一定程度上降低豬糞堆肥過程中的CH4排放.吳娟[19]在豬糞堆肥中加入過磷酸鈣可增加堆肥產(chǎn)品中30%總碳和40%總氮含量,并顯著降低CH4、CO2和NH3的排放.羅一鳴等[20]在豬糞堆肥中添加3.3%～6.6%的過磷酸鈣處理相較于對照減少30%總溫室氣體排放量.林小鳳等[21]研究發(fā)現(xiàn)過磷酸鈣作為堆肥氮素固定劑,最高氮素固定率達(dá)85%.Hao等[22]在牛糞條跺式堆肥中加入磷石膏,發(fā)現(xiàn)可起到減少堆肥CH4排放的效果.Gabhane等[23]的研究認(rèn)為,磷石膏減少堆肥氮素?fù)p失的效果可能源自其對堆肥物料pH值的調(diào)節(jié)作用.含磷添加劑對NH3和CH4減排效果顯著,但對N2O減排作用仍不明晰.

現(xiàn)有研究表明,硝化抑制劑、脲酶抑制劑和含磷添加劑在固氮減排上有較好的效果,但單一使用某種抑制劑效果不是很理想,如硝化抑制劑有增加氨揮發(fā)的可能[24].本文在現(xiàn)有研究基礎(chǔ)上,以雙氰胺和氫醌為主要添加材料,在控制N2O產(chǎn)生基礎(chǔ)上,進(jìn)一步探究聯(lián)合添加磷石膏和過磷酸鈣對豬糞堆肥CH4和NH3排放的影響,實(shí)現(xiàn)堆肥過程N(yùn)2O、CH4和NH3的同步減排,研究結(jié)果旨在為畜禽糞便堆肥過程溫室氣體減排和氮素固定提供理論參考.

1 材料與方法

1.1 實(shí)驗(yàn)材料

實(shí)驗(yàn)以新鮮豬糞和玉米秸稈為原料,基本性狀見表1.豬糞取自北京市海淀區(qū)蘇家坨養(yǎng)豬場;玉米秸稈取自北京市大興區(qū),經(jīng)自然風(fēng)干后粉碎成長度小于5cm的小段.雙氰胺和氫醌為分析純化學(xué)試劑,含磷添加材料包括過磷酸鈣和磷石膏,均購于肥料市場.過磷酸鈣產(chǎn)地為河北涿鹿,P2O5質(zhì)量分?jǐn)?shù)318%;磷石膏產(chǎn)地為湖北宜昌,P2O5質(zhì)量分?jǐn)?shù)￡0.8, CaSO4·2H2O質(zhì)量分?jǐn)?shù)375%.

表1 堆肥原料基本理化性質(zhì)

注:a基于濕基;b基于干基.

1.2 實(shí)驗(yàn)設(shè)計

豬糞和玉米秸稈按鮮重6:1混合,雙氰胺和氫醌添加比例分別為0.1%和0.03%(以干重計).實(shí)驗(yàn)共設(shè)3個處理,分別為只添加雙氰胺和氫醌(HD)、在雙氰胺和氫醌的基礎(chǔ)上添加磷石膏(HD+P)和添加過磷酸鈣(HD+S),各處理添加材料比例與添加時間節(jié)點(diǎn)見表2.實(shí)驗(yàn)在60L發(fā)酵罐中進(jìn)行,采用機(jī)械強(qiáng)制間歇式通風(fēng),通風(fēng)速率設(shè)定為0.36L/(kgDM·min),每通風(fēng)20min暫停40min.本次實(shí)驗(yàn)共堆置40d,初始含水率為67%,除堆肥起始和結(jié)束日外,分別在第6, 12, 19, 26和33d進(jìn)行人工翻堆、稱重和采集固體樣本.由于雙氰胺高溫易分解,第19d翻堆采樣后再進(jìn)行添加,再次翻勻后裝回發(fā)酵裝置中.

表2 實(shí)驗(yàn)設(shè)計(%)

注:基于干基; -表示未添加.

1.3 實(shí)驗(yàn)方法

堆肥溫度由溫度傳感器記錄,二氧化碳(CO2)采用泵吸式氣體檢測儀(英國Geotech, BM2K-EOOO)直接讀數(shù)測定.將新鮮樣品在105℃下烘干至恒重用于測定其含水率.將鮮樣與去離子水以1:10的質(zhì)量體積比混合,在170r/min下振蕩30min,通過0.45μm濾膜過濾并收集上清液,用于測定pH值、電導(dǎo)率(EC)、種子發(fā)芽指數(shù)(GI)和4/6(465和665nm處吸光度比值).pH值和EC用MP521型pH計和電導(dǎo)儀測定,4/6使用紫外光分光光度計在波長為465和665nm處測定,GI測定選用小白菜種子,用上述水浸提液5mL于墊有濾紙的培養(yǎng)皿中,置于(20±1)℃培養(yǎng)箱中培養(yǎng)48h后測定發(fā)芽率和根長,并根據(jù)Ren等[25]公式計算.

NH4+-N(Ammonium)和NO3--N(Nitrate)測定方法是將鮮樣與2mol/L KCl溶液按照1:10質(zhì)量體積比混合,振蕩30min,靜置過濾取上清液經(jīng)稀釋后上流動分析儀測定(Auto Analyzer 3,Seal,德國).總有機(jī)碳(TOC)參照農(nóng)業(yè)行業(yè)標(biāo)準(zhǔn)《NY525-2021 有機(jī)肥料》[26]中的標(biāo)準(zhǔn)方法測定;總氮(TN)采用元素分析儀測定(Elementar Analysensysteme, Hanau,德國).碳氮比(C/N)使用總有機(jī)碳含量除以總氮含量計算而得.

NH3測定采用吸收瓶法,即用質(zhì)量分?jǐn)?shù)2%的硼酸直接吸收,標(biāo)準(zhǔn)濃度的稀硫酸滴定.CH4和N2O氣體樣品使用帶三相閥門的注射器采集,用SP-3420A型氣相色譜(北京北分瑞利)測定.堆肥過程中的總碳、氮損失比例、NH3和N2O排放占總氮損失比例及CH4排放占總碳損失比例計算均參照陳是吏等[27]公式計算.總溫室氣體是將堆肥產(chǎn)生的N2O和CH4根據(jù)政府間氣候變化專門委員會2007年報告,按照單位質(zhì)量CH4和N2O的100a溫室效應(yīng)分別是CO2的25和298倍進(jìn)行折算.

1.4 統(tǒng)計分析

文章中圖用Origin 2018繪制,最小顯著差異(LSD)用SAS 8.2(SAS Institute, Cary, NC, USA)分析.

2 結(jié)果與討論

2.1 理化和腐熟度指標(biāo)

堆肥過程中溫度變化如圖1a所示,環(huán)境溫度在20.19～29.12℃范圍之間.各處理堆肥溫度變化趨勢一致,堆肥第2d各處理溫度達(dá)到50℃以上(< 0.001).HD+S處理升溫略有延遲,由于過磷酸鈣的弱酸性會降低堆肥初始pH值,導(dǎo)致嗜熱微生物的活性受到抑制[27].HD、HD+P和HD+S處理均在堆肥1周左右達(dá)到最高溫,分別為72.4, 73.0和73.4℃,高溫期均持續(xù)20d以上,滿足《糞便無害化衛(wèi)生要求(GB7959-2012)》[28]中堆肥溫度應(yīng)在50～55℃持續(xù)5～7d以上的要求.第26d翻堆后,部分處理溫度再次出現(xiàn)短暫上升,尤其是HD+S處理,可能是因?yàn)镠D+S處理中剩余的可利用碳和氮高于其他2個處理,其CO2濃度在腐熟期顯著高于其他2個處理(<0.001),與Luo等[29]豬糞堆肥中結(jié)果一致;HD+P處理翻堆后溫度逐漸下降.堆肥過程中堆體溫度的上升常伴隨著CO2濃度的上升,各處理堆肥溫度和CO2濃度呈顯著正相關(guān)(=0.646～0.904,<0.001).pH值不僅是影響堆肥過程中的主要環(huán)境因素,也是堆肥腐熟度的表征指標(biāo)[30].pH值整體呈現(xiàn)上升趨勢(圖1c),在26d后逐漸趨于穩(wěn)定.過磷酸鈣的添加會降低堆肥初始pH值,其余處理在堆肥第6d pH值均出現(xiàn)短暫上升,至第12d隨著小分子有機(jī)酸累積, pH值下降,在Li等[31]研究中也發(fā)現(xiàn)了相同的現(xiàn)象.在堆肥結(jié)束時,各處理的pH值均達(dá)到腐熟范圍(7.90～ 8.30)(<0.05).

EC是評價堆肥對作物毒害作用的重要指標(biāo),可反應(yīng)堆體中可溶性鹽的含量.堆肥的可溶性鹽含量較高會對種子發(fā)芽和作物的生長繁殖產(chǎn)生抑制作用[32].隨著堆肥的過程,EC值整體呈現(xiàn)下降趨勢(圖1d),HD+P和HD+S處理的EC值顯著高于對照組(<0.05),這是由于含磷添加劑會增加堆肥中的可溶性Ca2+和SO42-離子.第26d,HD+S處理的EC值上升,這是因?yàn)槲⑸镞M(jìn)一步分解堆體中的有機(jī)碳和有機(jī)氮,產(chǎn)生大量可溶性鹽導(dǎo)致EC上升.堆肥結(jié)束時,各處理EC值均￡4mS/cm,不會對作物造成鹽害[33]. GI值可表征植物毒性特征,評估堆肥產(chǎn)品腐熟度.所有處理GI值在整體呈現(xiàn)上升趨勢(圖1e),各處理差異不顯著(>0.1).堆肥結(jié)束時, HD、HD+P和HD+S處理GI值分別為83.12%、113.12%和120.00%,所有處理GI值達(dá)到2021年發(fā)布的農(nóng)業(yè)行業(yè)標(biāo)準(zhǔn)《NY525-2021 有機(jī)肥料》[26]對GI的要求(GI> 70%).4/6可以表征腐殖酸的相對分子質(zhì)量大小或芳構(gòu)化程度,通常會隨著腐殖酸分子量的增加或芳構(gòu)化程度的增加而降低.堆肥初期,所有處理4/6上升表明有機(jī)物的代謝較為劇烈,產(chǎn)生了分子量較小的或芳構(gòu)化程度較低的富里酸,隨著堆肥進(jìn)入腐熟期,產(chǎn)生了較大分子量或芳構(gòu)化程度較高的胡敏酸,4/6隨即減小,堆肥產(chǎn)品趨于腐熟.HD+S處理4/6低于HD處理,表明添加過磷酸鈣可以提高堆肥腐殖化程度(<0.05),這也是HD+S處理GI值較高的原因.

圖1 堆肥過程理化性質(zhì)變化

隨著堆肥的過程,含水率整體呈現(xiàn)上升趨勢(圖1g),這是由于微生物在分解大分子物質(zhì)時會產(chǎn)生水,且堆肥通風(fēng)為間歇通風(fēng),分解過程產(chǎn)生的水量高于出口空氣中的水量,導(dǎo)致含水率上升,與Jiang等[34]豬糞間歇通風(fēng)堆肥中結(jié)果一致.HD+S處理初期升溫有所延遲,且堆肥后期溫度有所回升,導(dǎo)致其含水率在后期急速上升.堆肥結(jié)束時,各處理含水率范圍為70.61%～73.76%(<0.05).堆肥物料碳氮比(C/N)被認(rèn)為是影響堆體內(nèi)有機(jī)物微生物降解速率的重要指標(biāo)[35].隨著堆肥的過程,各處理C/N呈現(xiàn)先略微上升后下降的趨勢,各處理差異不顯著(>0.1).堆肥初期,各處理TN含量下降,導(dǎo)致各處理C/N略微上升;堆肥高溫期,堆體內(nèi)物質(zhì)轉(zhuǎn)換速率較快,各處理C/N下降幅度較大;堆肥腐熟期,微生物活性受到低C/N等因素限制,各處理C/N趨于穩(wěn)定.堆肥結(jié)束時,各處理C/N分別為10.50, 11.44和11.90.

2.2 元素C和N含量變化

各處理的銨態(tài)氮呈現(xiàn)相同的變化趨勢(圖2a),隨著堆肥時間呈現(xiàn)先上升后逐漸下降趨勢,HD+P和HD+S處理的NH4+-N含量顯著高于對照組(<0.05).含磷添加劑的添加可促進(jìn)對NH4+-N的固定,一方面源于含磷添加劑降低堆體pH值,另一方面是鳥糞石結(jié)晶的形成,這也是減少氨氣排放和氮素?fù)p失的原因[20].各處理NO3--N濃度變化如圖2b所示,各處理整體上呈現(xiàn)下降趨勢,差異不顯著.第19d翻堆后加入雙氰胺,硝化抑制劑抑制硝化細(xì)菌的活性從而減少堆肥過程中硝化作用的發(fā)生,使得堆肥NO3--N濃度進(jìn)一步下降且NH4+-N保持在較高水平.堆肥結(jié)束時,HD+S處理的NO3--N濃度最低,表明過磷酸鈣會加強(qiáng)雙氰胺的硝化抑制作用.

堆肥初期各處理TN含量為20.33～21.98g/kg,到堆肥結(jié)束時增加至24.53～29.74g/kg(圖2c).堆肥初期由于氨損失引起各處理TN濃度下降,隨著有機(jī)碳的快速降解,TN相對含量逐漸升高,在Li等[36]的研究中也展現(xiàn)出相同的規(guī)律.堆肥結(jié)束時各處理TOC含量為280.62～312.26g/kg,顯著低于堆肥初期345.50～379.68g/kg(圖2d)(<0.001),其中微生物呼吸為碳損失的主要途徑[37],呼吸作用造成的CO2-C損失占TOC總損失的60.67%～85.82%(表3).

2.3 NH3、CH4和N2O排放

堆肥過程中NH3的排放速率和累積排放量如圖3a～b所示.NH3的排放主要集中在高溫期,隨著有機(jī)質(zhì)的降解,微生物產(chǎn)生大量NH3.在整個堆肥過程中,HD處理的NH3排放速率最大峰值在第7d,為0.62g/(kg·d);HD+P和HD+S處理的NH3排放速率最大峰值均延遲至第8d,分別為0.37,0.47g/(kg·d).可見,在雙氰胺和氫醌的基礎(chǔ)上添加磷石膏和過磷酸鈣可進(jìn)一步控制NH3的排放.經(jīng)過40d的堆肥, HD、HD+P和HD+S處理的NH3累積排放分別為5.18, 4.40,4.30g/kg,各處理呈現(xiàn)顯著差異(<0.001).HD+P和HD+S處理相較于HD處理NH3排放整體減少15.21%和16.91%,與張邦喜等[38]的研究結(jié)果一致,其減排原因?yàn)檫^磷酸鈣可以使堆肥中的銨轉(zhuǎn)換為較穩(wěn)定的磷酸銨或硫酸銨[39],且NH4+能交換Ca2+等陽離子,減少氮的損失.

N2O的產(chǎn)生主要來源于堆肥中的硝化和反硝化反應(yīng),圖3c～d為N2O的排放速率和累積排放量變化.N2O的排放峰值主要集中在堆肥初期,此現(xiàn)象與趙旭峰[40]的研究相同,HD、HD+P和HD+S處理的排放速率峰值分別為0.052, 0.039和0.075g/(kg·d).在堆肥高溫期,高溫會抑制硝化細(xì)菌的活性[41],使N2O排放減少,但在翻堆后個別處理出現(xiàn)了排放小峰值,這是由于翻堆改變堆體中的氧氣分布,NO--N通過不完全反硝化反應(yīng)轉(zhuǎn)換為N2O.在第19d加入了硝化抑制劑-雙氰胺,使得堆肥腐熟期N2O的排放量顯著低于堆肥高溫期,這與羅一鳴等[20]的豬糞堆肥相反,其排放峰值主要出現(xiàn)在腐熟期,表明加入雙氰胺后抑制了腐熟期N2O排放峰值的反彈.堆肥結(jié)束后,HD、HD+P和HD+S處理的N2O累積排放分別為0.24, 0.24, 0.29g/kg,而在Luo等[42]相同原料和規(guī)模的堆肥實(shí)驗(yàn)中,不添加添加劑的對照組N2O累積排放達(dá)到0.6g/kg,表明雙氰胺能顯著減少N2O的排放.在雙氰胺和氫醌的基礎(chǔ)上添加磷石膏和過磷酸鈣會增加N2O的排放,增加比例分別為0.14%和20.57%,其中HD+S處理N2O的排放量顯著增加,這是由于較低的pH值會抑制反硝化作用,通過抑制N2O還原酶的活性使得反硝化細(xì)菌的還原能力降低,增加N2O的排放[43],并且過高的NH4+-N會抑制亞硝酸鹽的氧化,使得亞硝酸根積累,進(jìn)一步促進(jìn)N2O排放.

堆肥過程中CH4排放主要是由于堆體內(nèi)氧氣擴(kuò)散距離有限,局部厭氧使得產(chǎn)甲烷菌利用堆體中的有機(jī)物,從而導(dǎo)致CH4產(chǎn)生[7].堆肥過程中CH4的排放速率和累積排放量如圖3e～f所示.CH4的排放峰值主要集中在高溫期,這是由于微生物分解大量有機(jī)質(zhì),氧氣消耗率達(dá)到35.12%～91.22%,形成了局部缺氧區(qū).HD、HD+P和HD+S處理CH4的排放速率峰值分別為0.59, 0.42和0.50g/(kg·d),呈現(xiàn)顯著差異(<0.001).堆肥結(jié)束后,HD、HD+P和HD+S處理的CH4累積排放分別為5.79, 3.57, 4.41g/kg. HD+P和HD+S處理相較于HD處理CH4排放整體減少38.30%和23.75%,這是由于產(chǎn)甲烷菌活性較易受到氧化還原電位、無機(jī)鹽離子濃度等因素的影響.Hao等[22]利用磷石膏作為牛糞堆肥添加材料的實(shí)驗(yàn)發(fā)現(xiàn),磷石膏顯著降低CH4排放,并認(rèn)為與SO42-離子對產(chǎn)甲烷細(xì)菌的抑制作用有關(guān).除HD+S處理,CH4的日排放量與溫度和CO2濃度均呈顯著正相關(guān),其相關(guān)性分別為0.549～0.651(< 0.001)和0.434～0.528 (<0.005).可見,在雙氰胺和氫醌的基礎(chǔ)上添加磷石膏和過磷酸鈣可進(jìn)一步控制CH4的排放.

2.4 碳、氮平衡及溫室效應(yīng)分析

堆肥過程中沒有產(chǎn)生滲濾液,各元素主要以氣體形式損失,表3為3個處理碳、氮平衡及溫室效應(yīng)分析.各處理碳損失占初始總有機(jī)碳的48.40%～ 54.59%,主要以CO2形式損失(30.61%～41.54%),以CH4形式損失的碳較少(0.93%～1.50%),HD+P和HD+S處理相較于HD處理的總碳損失分別減少7.58%和11.33%.氮損失占初始總氮的22.32%～ 33.52%,主要以NH3形式損失(19.57%～23.55%),以N2O形式損失的氮較少(1.08%～1.30%),相較于Luo等[42]實(shí)驗(yàn)中對照組40.4%的氮損失(29.1%的NH3損失和3.1%的N2O形式損失),雙氰胺、氫醌和含磷添加劑的添加顯著減少堆肥過程中的氮損失,尤其是以N2O形式損失的氮素.在雙氰胺和氫醌的基礎(chǔ)上添加含磷添加劑,雖會略微增加N2O的排放,但可顯著減少NH3的排放,HD+P和HD+S處理氮損失分別減少25.03%和33.42%,這與Zvomuya等[44]的研究結(jié)果一致.

表3 碳、氮平衡及溫室效應(yīng)分析

注:碳、氮素平衡分別為碳、氮損失占初始總有機(jī)碳、總氮的百分比;溫室氣體排放當(dāng)量值以物料的干基計算;N2O和CH4對溫室效應(yīng)的貢獻(xiàn)率依次分別為CO2的298和25倍.

堆肥過程中的溫室氣體主要包括CO2、CH4和N2O.根據(jù)政府氣候變化專門委員會(IPCC)關(guān)于農(nóng)業(yè)溫室氣體排放的指南,堆肥過程中的CO2源于生物過程,不作為全球變暖的貢獻(xiàn)因子,但CH4和N2O都是對溫室效應(yīng)貢獻(xiàn)較大的溫室氣體.HD+P和HD+S處理分別減少38.31%和23.75% CH4產(chǎn)生的溫室效應(yīng),分別增加0.16%和20.57% N2O增溫潛勢, HD+P和HD+S處理的總溫室效應(yīng)分別減少24.30%和7.60%,表明在雙氰胺和氫醌的基礎(chǔ)上添加磷石膏和過磷酸鈣有利于控制堆肥過程中溫室氣體的排放.Jiang等[34]研究了不同的工藝參數(shù)下溫室氣體排放,發(fā)現(xiàn)豬糞堆肥過程總溫室氣體排放為289～720kg CO2-eq/t,顯著高于本研究,說明雙氰胺、氫醌進(jìn)一步聯(lián)合含磷添加劑對總溫室氣體排放有顯著減排作用.

3 結(jié)論

3.1 堆肥后各處理產(chǎn)品均達(dá)到無害化和腐熟度要求,HD、HD+P和HD+S處理GI值分別為83.12%、113.12%和120.00%,在雙氰胺和氫醌的基礎(chǔ)上添加磷石膏和過磷酸鈣提高堆肥腐熟度和腐殖化進(jìn)程.

3.2 在雙氰胺和氫醌的基礎(chǔ)上添加含磷添加劑可降低7.58%～11.33%碳素?fù)p失和25.03%～33.42%氮素?fù)p失.

3.3 氫醌和雙氰胺分別通過減少初期有機(jī)氮的礦化和抑制腐熟期硝化作用減少N2O的排放.在雙氰胺和氫醌降低N2O排放基礎(chǔ)上,聯(lián)合使用含磷添加劑可進(jìn)一步減少15.21%～16.91% NH3排放和23.75%～38.30% CH4排放,添加含磷添加劑會增加0.14%～20.57% N2O排放,但總溫室效應(yīng)降低7.60%～ 24.30%,其中磷石膏處理總溫室氣體減排效果最佳.

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Effects of dicyandiamide, hydroquinone and phosphorus additives on greenhouse gas emissions during composting.

YANG Yan, LI Guo-xue, LUO Yi-ming, YANG Jia, YUAN Jing*

(Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resource and Environmental Science, China Agricultural University, Beijing 100193, China)., 2022,42(2)：936～944

In order to reduce the emission of N2O, CH4and NH3simultaneously during composting, this study explored the effects of phosphogypsum (PG) and superphosphate (SP) on NH3andgreenhouse gases emissions based on the dicyandiamide (DCD) and hydroquinone (HR) addition during pig manure composting. Pig manure and cornstalks were used and mixed as raw materials, and three treatments were carried out for 40days in the 60L composting vessel. In the HD treatment, DCD and HR were added; for the HD+P and HD+S treatment, the PG and SP were added together, separately, on the basis of DCD and HR addition. The results showed that the phosphorus additives amendment promoted the compost maturity and reduced carbon (7.58%～11.33%) and nitrogen losses (25.03%～33.42%) based on the addition of dicyandiamide and hydroquinone. The combined use of those additives could reduce NH3emission by 15.21%～16.91% and CH4emission by 23.75%～38.30%, while increased N2O emissions by 0.14%～20.57%. The phosphorus-containing additives could fix ammonium nitrogen and reduce NH3emissions due to its lower pH and phosphoric acid. At the same time, the CH4emissions was reduced by sulfuric acid ions through inhibiting the methanogens activity. In general, adding dicyandiamide, hydroquinone and phosphorus simultaneously decreased the total greenhouse emission of 7.60%～24.30%, and the HD+P treatment had the best performance in greenhouse gas emissions during composting.

composting；dicyandiamide；hydroquinone；phosphorus additives；greenhouse gases；ammonia

X713

A

1000-6923(2022)02-0936-09

楊 燕(1998-),女,四川雅安人,中國農(nóng)業(yè)大學(xué)碩士研究生,主要研究方向?yàn)橛袡C(jī)固體廢物處理與資源化.

2021-06-23

國家現(xiàn)代農(nóng)業(yè)產(chǎn)業(yè)技術(shù)體系建設(shè)專項(xiàng)(CARS-39-19)

* 責(zé)任作者, 副教授, jingyuan@cau.edu.cn