張樂, 徐平平, 李素艷, 孫向陽, 張濤, 劉子豪, 姚麗媛
(北京林業(yè)大學林學院,100083,北京)
有機-無機復(fù)合改良劑對濱海鹽堿地的改良效應(yīng)研究
張樂, 徐平平, 李素艷?, 孫向陽, 張濤, 劉子豪, 姚麗媛
(北京林業(yè)大學林學院,100083,北京)
濱海鹽堿土; 有機改良劑; 園林廢棄物堆肥; 高溫惰化; 磷石膏
土壤鹽堿化是世界上許多國家面對的重要難題,其危害主要體現(xiàn)在影響植被生長,惡化生態(tài)環(huán)境。若能充分改良利用鹽堿地資源,營造大面積的林分,對于提高森林覆蓋率,減少水土流失及改善脆弱的生態(tài)環(huán)境即會產(chǎn)生巨大作用[1-2]。
目前,在濱海鹽堿化土壤改良治理技術(shù)方面,開展了大量的研究工作[3-5]。其中,化學改良措施可以在一定程度上,增加土壤的孔隙度,減輕Na+毒害,增加土壤養(yǎng)分;但由于化學改良材料種類眾多,許多化學改良劑存在對土壤造成污染的危險,尋找合適的改良材料,是目前的重要研究方向[6]。城市園林綠化的養(yǎng)護過程中,會產(chǎn)生大量的園林綠化廢棄物[7],其消納處理是一項亟需解決的問題。研究[8]發(fā)現(xiàn),園林廢棄物經(jīng)過腐熟發(fā)酵后,可促進土壤團聚體的生成,改善土壤通透性[9];園林廢棄物的惰化產(chǎn)品對土壤結(jié)構(gòu)有很好的改良效果,它的吸附性對土壤環(huán)境也有多方面的積極影響[10]。磷石膏是磷酸工業(yè)廢渣,大量堆積會對自然環(huán)境造成極大的污染,作為常用的鹽堿土壤改良劑,能夠有效降低土壤鹽分及pH值[11-13]。
磷石膏與農(nóng)業(yè)廢棄物等結(jié)合施用,改良鹽堿土已經(jīng)有了一定的研究基礎(chǔ)[14-15],但關(guān)于磷石膏結(jié)合園林廢棄物的相關(guān)研究鮮有報道。筆者根據(jù)濱海鹽堿地特點,研發(fā)了一種新型有機改良劑,由園林廢棄物的堆肥和高溫惰化產(chǎn)品,按照一定比例配制而成,通過有機改良劑與磷石膏結(jié)合,改良濱海鹽土,以期為濱海鹽堿地區(qū)的城市綠化,提供理論依據(jù)。
研究區(qū)位于河北省滄州市渤海新區(qū)(E117°24′~38′,N38°20′~28′),屬暖溫帶半濕潤大陸性季風型氣候,年平均降雨量627 mm,75%集中在夏季,年平均蒸發(fā)量為降雨量的3倍多。研究區(qū)的淺層地下水埋藏深度較淺,雨季時,地下水深度僅為80 cm,平均礦化度為4 g/L,屬強礦化度水。由于淡水資源緊缺,農(nóng)業(yè)灌溉用水多混有淺層含鹽地下水,極易造成土壤的鹽漬化。
前期土壤調(diào)查表明,該區(qū)域的土壤母質(zhì)主要為河流三角洲沖積物,土壤質(zhì)地呈現(xiàn)出層狀分布特征,0~20 cm為粉砂壤土,20~40 cm處可見黏土層,40~100 cm深度土層仍為粉砂壤土,土壤質(zhì)地不均,且保水透氣性差。土壤鹽分的垂直分布特征呈現(xiàn)出明顯的表聚性[16-17],以氯化物占絕對優(yōu)勢,其中,Cl-和Na+質(zhì)量分數(shù)約占全鹽質(zhì)量分數(shù)的46.68%和37.02%。
2.1 供試材料
有機改良劑(CP):由園林廢棄物堆肥產(chǎn)品[18](GWC)和高溫惰化產(chǎn)品[19](PG),按照質(zhì)量比4∶1配制而成。產(chǎn)品均購自園林綠化廢棄物消納中心。
無機改良劑:磷石膏(Pg)購自山東省華鎣商貿(mào)有限公司,pH值為2.5,主要成分為CaSO4·2H2O(約占總質(zhì)量的94.6%),MgO、P2O5和Fe2O3比例依次為0.087%、2.06%和0.37%。
2.2 試驗設(shè)計
試驗地位于滄州臨港經(jīng)濟技術(shù)開發(fā)區(qū)學院路南側(cè)綠化帶。綠化施工時,采取客土抬高地面的工程措施,客土來自于附近的麥田。試驗于工程結(jié)束半年后,在試驗地內(nèi)土壤鹽漬化程度相同的區(qū)域進行,設(shè)置2個因素,分別為磷石膏(Pg)和有機改良劑(CP);依據(jù)前期的研究結(jié)果,每個因素設(shè)置4個水平,其中:磷石膏施用量為0、1、2 和3 kg/m2(即Pg-0、Pg-1、Pg-2、Pg-3),有機改良劑的施用量為待改良土方量體積的0、5%、10%和15%(即CP-0、CP-5、CP-10、CP-15);各因素的不同水平間兩兩組合,共計16個處理,每個處理為一個小區(qū),其中,Pg-0和CP-0處理組合作為對照處理。
試驗地土壤及供試有機改良劑,其基本理化性質(zhì)如表1所示。各處理隨機分布,每個處理為一個試驗小區(qū),長×寬規(guī)格為12 m×6 m,相鄰小區(qū)間距為3 m,且每個小區(qū)包含3棵國槐(Sophorajaponica),即試驗重復(fù)3次。有機改良劑與磷石膏直接施入國槐栽植坑內(nèi),并與表層土壤(0~20 cm)混合均勻。試驗期間,各處理采取相同的養(yǎng)護措施。
表1 試驗區(qū)土壤及有機改良劑理化性質(zhì)
注:土壤浸提液采用水土比5∶1制取,有機改良劑浸提液采用蒸餾水∶改良材料=5∶1制取。以下類同。Note: Soil extractions were prepared by the ratio of water to soil 5∶1. CP extractions were prepared by the ratio of water to CP 5∶1. CP is an organic modifier. The same below.
2.3 樣品采集與測定
土壤樣品采集按季度分別于2014年7月、2014年10月、2015年3月和2015年7月進行,每個處理中,隨機選取3個點采集表層土壤(0~20 cm)。
SAR簡稱鈉吸附比,計算公式為
2.4 數(shù)據(jù)處理
數(shù)據(jù)采用Excel 2010及SPSS 18軟件進行統(tǒng)計分析。其中,單因素方差分析(one-way ANOVA)比較不同處理間的差異,多重比較采用Duncan法檢驗。
3.1 土壤pH值變化
試驗進行約1年后,各處理表層土壤(0~20 cm)的pH值見圖1??梢钥闯觯诹资嗍┯昧恳欢ǖ臈l件下(Pg處理),施入有機改良劑(CP處理),在一定程度上能夠降低土壤的pH值,但是只有當有機改良劑施入量達到待改良土方量體積的15%時(CP-15處理),土壤pH值才能顯著低于CP-0處理(圖1-A);在有機改良劑施入量一定的條件下,隨著磷石膏施入量的增加,土壤pH值基本呈現(xiàn)顯著降低趨勢(圖1-B)。
CP-0、CP-5、CP-10和CP-15分別是有機改良劑的施用量為待改良土方量體積的0、5%、10%和15%;Pg-0、Pg-1、Pg-2和Pg-3分別為磷石膏施用量為0、1、2和3 kg/m2的處理。各處理不同字母表示差異顯著(p<0.05),下同。CP-0, CP-5, CP-10 and CP-15 refer to the applied amount of CP by 0, 5%, 10% and 15% of being-ameliorated soil volume, respectively. Pg-0, Pg-1, Pg-2 and Pg-3 refer to the treatment with 0, 1, 2, and 3 kg/m2 of phosphogypsum (Pg), respectively. Different letters represent significantly different at P<0.05, the same below.圖1 不同處理對土壤pH值的影響Fig.1 Effects of different treatments on pH values of the saline soil
施入磷石膏約1個月后,各處理的土壤pH值均顯著低于Pg-0,由于土壤的緩沖性和磷石膏中的酸性物質(zhì)在降水的作用下淋洗出土體,土壤pH值隨著時間的變化有所回升。施入磷石膏的同時施入有機改良劑,可以使土壤pH值較快趨于穩(wěn)定(相鄰采樣日期間差異不顯著,p>0.05)。未施入有機改良劑時(圖2-A),施入磷石膏的各處理在改良的9個月之后,土壤pH值才能趨于穩(wěn)定;而在有機改良劑施入時(圖2-B,C和D),且磷石膏施入量適中(Pg-1,Pg-2)的條件下,僅4個月,土壤pH值即可趨于穩(wěn)定。
3.2 土壤SAR變化
SAR簡稱鈉吸附比,是評價土壤鹽堿化程度的一個重要指標[21],該指標的變化表現(xiàn)在SAR越大,對土壤的有害性也相對越大。從單因素試驗來看,如圖3-A(Pg-0)所示,隨著有機改良劑施入量的增加,土壤SAR呈現(xiàn)不同程度的降低,原因在于GWC分解產(chǎn)生的腐殖酸類物質(zhì),可以改善土壤結(jié)構(gòu),從而促進土壤鹽分的淋洗,顯著降低土壤中Na+質(zhì)量分數(shù);另外,PG也會吸附土壤中的Na+,如圖3-B(CP-0)所示,隨著磷石膏施入量的增加,土壤SAR均顯著降低,原因在于加入磷石膏后,土壤中Ca2+質(zhì)量分數(shù)顯著增加,且Ca2+與Na+發(fā)生離子代換作用,導(dǎo)致土壤膠體吸附的Na+質(zhì)量分數(shù)減少。2種因素交互作用下(圖3-A),在不施入或施入較少的磷石膏時(Pg-0、Pg-1),SAR隨著有機改良劑施入量的增加而顯著降低,而施入較多的磷石膏時(Pg-2、Pg-3),隨著有機改良劑施入量的增加,SAR降低不顯著;如圖3-B,無論有機改良劑的水平如何,SAR隨著磷石膏施入量的增加而顯著降低。
圖2 不同處理下土壤pH值的動態(tài)變化Fig.2 Dynamic of pH values of the saline soil under different treatments
圖3 不同處理對土壤SAR的影響Fig.3 Effects of different treatments on SAR (Sodium Absorption Ratio) of the saline soil
圖4 不同處理對土壤Cl-及質(zhì)量分數(shù)的影響
3.4 土壤全鹽質(zhì)量分數(shù)變化
圖5 不同處理對土壤全鹽質(zhì)量分數(shù)的影響Fig.5 Effects of different treatments on total salt content of the saline soil
3.5 改良效果與成本簡析
由上可知,Pg-1、CP-5處理組合的改良效果較好。如表2所示,與未施入任何土壤改良劑的Pg-0、CP-0處理組合,以及鋪設(shè)于試驗初期,以抬高地表的綠化客土相比, Pg-1、CP-5處理組合表層土壤全鹽質(zhì)量分數(shù)仍顯著高于試驗初期的綠化客土,但全鹽質(zhì)量分數(shù)僅增加1 g/kg左右;而與未采取土壤改良措施的Pg-0、CP-0處理組合相比,土壤全鹽質(zhì)量分數(shù)顯著降低,降幅高達3 g/kg左右。此時的改良成本約為6.70元/m2(表3)。
1) 施入有機改良劑以及磷石膏,均可有效降低土壤pH、SAR和Cl-質(zhì)量分數(shù),調(diào)整離子組成結(jié)構(gòu),降低單鹽毒害作用,對植物生長有利。但是,由于磷
表2 土壤改良效果
土壤的pH變化過大,對植物產(chǎn)生不利影響;而在施入磷石膏的同時,施入有機改良劑,可以使土壤石膏多殘留有硫酸,酸性較強,施入土壤后,pH值較快地趨于穩(wěn)定。
表3 推薦措施下的土壤改良成本
注:未考慮運費及人工成本。Note: Cost for transportation and labor are not taken into account yet.
3) 磷石膏與有機改良劑單施能夠顯著改善土壤的鹽堿狀況,二者配施的效果優(yōu)于改良劑單施。此外,磷石膏中可能含有極其少量的重金屬成分,而園林廢棄物高溫惰化產(chǎn)物作為一種環(huán)境友好型材料,對重金屬具有一定的吸附性,從而降低植物的吸收,對植物生長有利。
4) 施入1 kg/m2的磷石膏及5%的有機改良劑時(體積比,約3.35 kg/m2),能夠取得較好的改良效果。采用該改良方案,能夠在一定程度上抑制表層土壤返鹽,適用于濱海地區(qū)受土壤鹽漬化影響的老城區(qū),以及其他不便進行大規(guī)模施工的區(qū)域,此方案可以作為一種可靠的改良措施,但其改良效果的長期性,仍然需要進一步的研究。
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Amelioration effects of organic-inorganic compound amendment on coastal saline-alkali soil
ZHANG Le, XU Pingping, LI Suyan, SUN Xiangyang, ZHANG Tao, LIU Zihao, YAO Liyuan
(School of Forestry, Beijing Forestry University, 100083, Beijing, China)
[Background] The urbanization level in coastal areas are higher than other areas in China, and the coastal soils in these areas are threatened by salinization, which could cause negative effects on ornamental plants surviving and growing, thus the ornamental value and ecological functions of the urban green land was reduced. In this way, the improvement of saline-alkali soil should result in a significant impact upon construction of urban green space in coastal areas. [Methods] The experiment was conducted in a greenbelt of Bohai district in Cangzhou City of Hebei Province, where is in high salinity. An organic modifier (Green waste compost:Pyrolysised garden wastes in 4∶1 as 0, 5%, 10%, and 15% of being-ameliorated soil volume) and phosphogypsum (0, 1, 2, and 3 kg/m2) were utilized for the soil amendments, totally 16 treatments by combining any 2 of them, and 0 of them as the control. Each treatment was laid in an experimental plot (12 m×6 m) with 3 repeats of plantingSophorajaponica. Soil samples were collected at 3 random sites of topsoil (0-20 cm) in each plot in July 2014, October 2014, March 2015 and July 2015. OHAUS Starter 3C was used for measuring pH, dual-indicator neutralization titration method for CO2-3and HCO-3, silver nitrate titration method (Moore method) for Cl-, EDTA titration method for Ca2+and Mg2+, indirect EDTA complexometric titration for SO2-4, flame photometry (FP6410, Shanghai) for K+and Na+, and total salt content was the sum of 8 ions’ concentrations. The data were analyzed by Excel 2010 and SPSS 18 software, single factor analysis of variance (one-way ANOVA) was to compare the differences among different treatments, and the multiple comparisons were examined by Duncan method. [Results] 1) The soil pH decreased obviously with the addition of organic modifier and phosphogypsum, and phosphogypsum played a leading role. To prevent the negative impacts to the plants from the drastic variations of pH caused by the application of phosphogypsum, organic modifier should be applied at the same time. 2) Single-factor experiment showed that soil SAR (Sodium Absorption Ratio) significantly decreased when this 2 soil amendments were more used. Moreover, phosphogypsum showed better effects than organic modifier. Interaction experiments showed that combined application of phosphogypsum and organic modifier achieved better effect in decreasing SAR than single application. 3) The content of Cl-significantly decreased with the application of phosphogypsum and organic modifier, but SO2-4was the opposite. 4) The experimental results demonstrate that combined application of phosphogypsum and organic modifier was suggested to get the better effect, the recommended addition of phosphogypsum and organic modifier were 1 kg/m2and 5% (volume ratio, about 3.35 kg/m2), which improved the saline soil effectively. [Conclusions] Due to the low cost, waste resource recovery and the solid environmental effects in treatment process, organic modifier is more practicable in the improvement of saline-alkali soil. Besides, this improvement method for saline soil provids a feasible plan for beneficial reuse of phosphogypsum and organic modifier.
coastal saline-alkali soil; organic modifier; green waste compost; pyrolysis; phosphogypsum
2016-09-21
2016-03-16
張樂(1993—),男,碩士研究生。主要研究方向:土壤修復(fù)。E-mail: zlomusic@163.com
?通信作者簡介: 李素艷(1968—),女,博士,副教授。主要研究方向:土壤改良與修復(fù)。E-mail:lisuyan@bjfu.edu.cn
S156.4+2
B
2096-2673(2017)02-0093-08
10.16843/j.sswc.2017.02.012
項目名稱: 林業(yè)公益性行業(yè)科研專項項目“林業(yè)廢棄物基質(zhì)化研制技術(shù)與應(yīng)用”(201504205)