【作者】 朱雪竹；

【导师】 黄耀；

【作者基本信息】 南京农业大学 ， 土壤学， 2009， 博士

【摘要】 全球变暖和酸雨污染是当今重要的全球性环境问题,已引起各国政府和国际学术界的广泛关注。全球变暖的主要原因之一是人类影响了生态系统的碳、氮循环,造成大气中温室气体(CO2、CH4、N2O等)浓度不断提高。同时,化石燃料的燃烧过程也向大气排放SO2、NOX,造成酸雨污染。农田生态系统是人类活动最活跃的系统,在全球变化研究中具有十分重要的地位。酸雨因具有较高浓度的H+、SO42-、NO3-,可通过影响土壤理化性质、农作物的生长和生理过程、土壤微生物群落的组成与活性,对农田温室气体的产生和排放产生影响。定量研究酸雨污染对农田温室气体排放的影响,将为客观评价酸雨污染的生态效应和正确估计农田温室气体排放提供依据。本研究的目的是：定量研究雨水离子浓度升高和／或pH值降低对不同土壤-作物系统温室气体(CO2、CH4、N2O)排放的影响规律,探讨其影响途径。本研究盆栽试验用于研究模拟酸雨对土壤-作物系统温室气体排放的影响规律,室内培养试验用于探讨秸秆、土壤水分条件对酸雨作用的影响。盆栽试验选择酸性(pH5.48)(S1)、中性(pH 6.70)(S2)、碱性(pH 8.18)(S3)水稻土,以我国大面积种植的粮食作物冬小麦、水稻为实验对象,分别设置雨水离子浓度和pH值存在差异的3种模拟雨水(T1(pH 6.0)、T2(离子浓度为T1 2倍,pH 6.0)、T3(离子浓度为T1 2倍,pH 4.4)),雨水喷淋量参照南京市1970-2000年30年月平均降水量。盆栽试验时间持续2个冬小麦和2个水稻生长季。土壤-作物系统温室气体排放速率采用静态暗箱-气相色谱技术测定。室内培养试验Ⅰ选择与盆栽试验相同的3种水稻土(分别设置施用秸秆0、15g.kg-1土处理)在20℃条件下进行40 d的培养试验。培养期间分别用pH值存在差异的3种模拟雨水(TC1(pH 6.0)、TC2(pH 4.5)、TC3(pH 3.0))将土壤含水量调为400 g·kg-1土。室内培养试验Ⅱ只选择了中性土壤S2(分别设置施用秸秆0、15g·kg-1土处理),室温条件下进行51 d的培养试验。培养期间分别用模拟雨水CR1(离子浓度为T22倍,pH 5.6)、CR2(离子浓度为CR1 2倍,pH5.6)、CR3(离子浓度同CR1,pH 3.5),将土壤含水量分别设置为400 g·kg-1土和淹水条件。种子培养试验雨水设置同盆栽试验,25℃条件下黑暗培养。主要结果如下：1.小麦生长期,酸雨显著促进了碱性土壤-小麦系统暗呼吸和N20排放,S3T3组平均暗呼吸速率分别比S3T1组和S3T2组高23.6%、27.6%,S3T3组N20平均排放速率比S3T2组高25.6%(p<0.05)(2005～2006年)；酸雨虽然未对中性土壤和酸性土壤-小麦系统平均暗呼吸速率和N20平均排放速率产生显著影响(p>0.05),但在小麦幼苗、拔节、灌浆等时期,也对温室气体排放产生了显著影响。2.水稻生长期,由于2006年和2007年田间秸秆填埋的差异,2年间酸雨对土壤-水稻系统温室气体排放的影响有所不同。2.1仅雨水pH值的降低并未对土壤-水稻系统平均暗呼吸速率产生显著影响；雨水离子浓度升高后可显著提高酸性土壤-水稻系统平均暗呼吸速率；当雨水离子浓度升高的同时pH值降低后,中性土壤-水稻系统2006年平均暗呼吸速率和碱性土壤-水稻系统2007年平均暗呼吸速率显著下降,但中性土壤-水稻系统2007年平均暗呼吸速率显著上升。具体的变化程度为：S1T2组2007年的平均暗呼吸速率比S1T1组高8.1%,S2T3组2006年平均暗呼吸速率比S2T1组降低21.4%,S3T3组2007年的平均暗呼吸速率比S3T1组低7.3%；S2T3组2007年的平均暗呼吸速率比S2T1组高7.9%(p<0.05)。2.2高离子浓度雨水对CH4排放有促进作用,低pH值雨水对CH4排放排有抑制作用。S1T2组CH4累积排放量比S1T1组高85.6%,S2T2组CH4累积排放量比S2T1组高19.2%,但未达到显著水平；S1T3组CH4累积排放量比S1T2组低51.5%,S2T3组CH4累积排放量比S2T2组低31.4%(p<0.05),但仅中性土壤-作物系统达到显著水平。2.3仅雨水pH值降低对土壤-水稻系统N20累积排放无显著影响(p>0.05)。雨水离子浓度升高抑制了酸性土壤-水稻系统和中性土壤-水稻系统N20排放。雨水离子浓度升高同时降低pH值后,抑制了中性土壤-水稻N20排放。具体的影响程度如下：S1T2组2006年N20累积排放量比S1T1组低16.6%(p=0.039),S2T2组2007年累积排放量比S2T1组低56.4%(p=0.019),S2T3组2007年累积排放量比S2T1组低71.9%(p=0.047)。3.通过室内培养试验证实,酸雨通过影响秸秆的分解过程对土壤系统温室气体排放产生影响。秸秆填埋是2006年和2007年间盆栽试验土壤-水稻系统结果差异的主要原因,同时土壤水分条件也发挥了重要影响。3.1低pH值雨水未显著影响土壤有机碳分解,但显著地影响了土壤中作物秸秆的分解与N20的产生与排放,从而对土壤系统C02、N20排放产生影响：酸雨促进了酸性和碱性水稻土中秸秆的分解,pH 3.0酸雨处理下秸秆在酸性土壤和碱性土壤中40 d分解总量比pH 6.0雨水处理下的分解总量高8%；酸雨抑制了中性水稻土中秸秆的分解,pH 3.0酸雨处理下秸秆40 d分解总量比pH 6.0雨水处理低15%。酸雨显著促进了酸性土壤对照组N20排放,S1TC3CK组N20累积排放量比S1TC1CK组高51.3%(p<0.05)。随着雨水pH值的降低,秸秆对土壤系统N20排放的抑制作用增强,导致3种土壤秸秆组N20排放量的差距随着雨水pH值的降低而缩小。3.2雨水离子浓度增加或pH值降低,未对中性土壤对照组或秸秆组CH4、N2O51d累积排放量产生显著影响,高离子浓度雨水可减少淹水处理的土壤对照组CO2排放,CR2CKF组C02-C累积排放量比CR1CKF低26.1%(p<0.05)。雨水差异对秸秆的分解差生了显著影响：淹水状态下,高离子浓度雨水与低pH值雨水均促进了中性土壤中秸秆的分解,秸秆分解总量在CR2F组、CR3F组中分别比在CR1F中高16.1%(p<0.01),2.6%(p<0.01)；非淹水状态下,高离子浓度雨水和低pH值雨水均抑制了中性土壤中秸秆的分解,秸秆分解总量在CR2D组、CR3D组中分别比在CR1D中低5.3%(p<0.05),8.1%(p=0.111)。综上所述,酸雨未改变土壤-作物系统温室气体排放的季节动态特征。在作物的不同生育期,酸雨对不同土壤-作物系统温室气体排放的影响并不相同。酸雨并未改变作物收割后农田系统温室气体排放。小麦生长期,碱性土壤-作物系统较酸性土壤和中性土壤-作物系统易受酸雨的影响；水稻生长期,N2O、CH4排放在酸性土壤-作物系统与中性土壤-作物系统中比其在碱性土壤-作物系统中更易受酸雨的影响。酸雨主要通过提高作物生长过程的能耗,改变土壤中秸秆的分解速率、作物秸秆与土壤的C／N,提高秸秆木质素含量、降低秸秆纤维素含量等途径对农田温室气体排放产生影响。同时,在酸雨的影响过程中,土壤pH值、土壤水分条件发挥了重要作用。更多还原

【Abstract】 Global warming and acid rain have become two mostly concerned environmental problems of worldwide importance. Anthropogenic increase of greenhouse gases is the main reason for Global warming. Meanwhile, SO2 and NOX emission from fossil fuel combustion is the main reason for acid rain.Agroecosystem plays an important status in the global change, and it is manipulated intensively by human. Acid rainwater increases the input of sulfate ion, nitrate ion, hydrogen ion to soil, and then has effects on the chemical properties of soil, the physiological characteristics and growth of crops, the community structure and activities of soil microorganisms, then induces the change to greenhouse gas (CO2, CH4, N2O) product and emission in agroecosystem. The quantitative investigation on the greenhouse gas emission from farmland treated with simulated acid rainwater will provide the method to evaluate the ecological effects of acid rain objectively. Furthermore, the results of this study will provide the theoretical basis to estimate the regional farmland greenhouse gas emission and its long-term trend in acid rain contaminated.The goal of this research is to quantitatively investigate the greenhouse gas (CO2, CH4, N2O) emission from soil-crop systems treated with different rainwater, which with higher ionic concentrations or lower pH values. The influence way of acid rain on greenhouse gas (CO2, CH4, N2O) emission from soil-crop systems was discussed.In this research, an outdoor pot experiment was used to study the effects of acid rain, and three incubation tests were conducted to discuss the influence way of acid rain. The outdoor pot experiment was conducted with paddy soils of pH 5.48 (S1), pH 6.70 (S2) and pH 8.18 (S3) during two years of rice-wheat growing season. Soil-crop systems were exposed to acid rainwater by spraying the crop foliage and irrigating the soil with simulated rainwater of T1 (pH 6.0), T2 (pH 6.0, ionic concentration was twice as rainwater T1), and T3 (pH 4.4, ionic concentration was twice as rainwater T1), respectively. The quantity of spray rainwater was calculated according to the monthly mean precipitation during 1970-2000. The static opaque chamber-gas chromatograph method was used to measure the flux of CO2, CH4, and N2O from soil-crop systems.Soil incubation test I, a 40-day incubation test, was conducted with the same paddy soils as the pot test. The soils were amended with 0 and 15 g-kg-1 of rice straw, adjusted to the moisture content of 400g-kg-1 air dried soil by using simulated rain of pH 6.0 (TC1), 4.5 (TC2), and 3.0 (TC3), and incubated at 20℃. Soil incubation test II, a 51-day incubation test, was conducted with the soil S2. The soil was amended with 0 and 15 g-kg-1 of rice straw, adjusted to the moisture content of 400g-kg-1 air dried soil or flooded, by using simulated rain of CR1 (pH 5.6, ionic concentration was twice as rainwater T2), CR2 (pH 5.6, ionic concentration was twice as rainwater CR1), and CR3 (pH 3.5, ionic concentration was the same as rainwater CR1), and incubated at room-temperature. Seeds culture test was conducted with rice seeds treated with the same simulated rainwater as in pot test, and incubated at 25℃in dark.Main results of this study are presented as follows:1. During the wheat-growing season, acid rain significantly promoted the average respiration rate and N2O flux from the alkaline soil-wheat systems. During 2005-2006, after the alkaline soil-wheat systems were treated with rainwater T3, the average respiration rate was 23.6% and 27.6% higher than that of alkaline soil-crop systems treated with rainwater T1 and T2, respectively. The N2O average emission rate in treatments S3T3 was 25.6% higher than that in treatments S3T2. Acid rain had significant effects on the dark respiration rate and N2O flux from neutral soil-wheat systems or acidic soil-wheat systems during some specific growth stage (seedling stage, jointing stage, and filling stage), while the average respiration rates and average N2O flux of these two soil-crop systems were not significantly influenced by acid rain.2. During the rice-growing season, the effects of acid rainwater on greenhouse gas emission from soil-rice systems were different between 2006 and 2007.2.1 Rainwater with lower pH value had no significant effects on the average respiration rates in three soil-rice systems. In acidic soil-rice systems, the average respiration rate was significantly promoted by the rainwater with higher ionic concentrations (T2) in 2007. Rainwater, with higher ionic concentrations and lower pH value, reduced the average respiration rate in neutral soil-rice systems during 2006 and that rate in alkaline soil-rice systems during 2007, while it increased the average respiration rate in neutral soil-rice systems during 2007. After the acidic soil-rice systems were treated with rainwater T2, the average respiration rate was 8.1%(p<0.05) higher than that of acidic soil-rice systems treated with rainwater T1. After soil-rice systems treated by rainwater T3, the average respiration rate was 21.4%(p<0.05) lower in neutral soil-rice systems during 2006,7.3%(p<0.05) lower in alkaline soil-rice systems during 2007, and 7.9%(p<0.05) higher in neutral soil-rice systems during 2007 than that rate in soil-rice systems treated with rainwater T1 during the same period respectively.2.2 Rainwater with higher ionic concentrations enhanced the CH4 emission, while rainwater with lower pH value reduced the CH4 emission from soil-rice systems. Higher ionic concentration rainwater could increase the CH4 cumulative emission from acidic soil-rice systems and from neutral soil-rice systems, but these effects did not reach significant level. Compared to the CH4 cumulative emission in rainwater T2 treatments, the CH4 emission decreased in acidic soil-rice systems and in neutral soil-rice systems treated with rainwater T3. After soil-rice systems treated with rainwater T2, the CH4 cumulative emission was 85.6% and 19.2% higher than that in acidic soil-rice systems and in neutral soil-rice systems treated with rainwater T1, respectively. After soil-rice systems treated with rainwater T3, the CH4 cumulative emission was 51.5% and 31.4% lower than that in acidic soil-rice systems and in neutral soil-rice systems treated with rainwater T2, respectively. However, only the effect reached significant level in neutral soil-rice systems.2.3 Rainwater with lower pH value had no significant effects on N2O cumulative emission from the three soil-rice systems. Higher ionic concentrations rainwater (T2) reduced the N2O cumulative emission from acidic soil-rice systems and from neutral soil-rice systems. Rainwater (T3), with higher ionic concentrations and lower pH value, could decrease the N2O cumulative emission from the neutral soil-rice systems. After soil-rice systems treated with rainwater T2, the N2O cumulative emission was 16.6% (p=0.039) (2006) and 56.4% (p=0.019) (2007) lower than that in acidic soil-rice systems and neutral soil-rice systems treated with rainwater T1, respectively. After neutral soil-rice systems treated with rainwater T3, the N2O cumulative emission was 71.9%(p=0.047) lower than that from neutral soil-rice systems treated with rainwater T1.3. It was demonstrated that acid rain affected the greenhouse gas emission from soil by disturbing the decomposition rate of straw. The moisture of soil played some important roles in the influence of acid rain.3.1 Lower pH value rainwater had no significant effect on the soil organic carbon decomposition while it significantly influenced the N2O emission and the straw decomposition. So it significantly influenced the greenhouse gas emission from soil systems. Compared with pH 6.0 rainwater treatment, acid rainwater of pH 3.0 treatment promoted the straw decomposition rates in both acidic paddy soil and alkaline paddy soil to 8% increase during 40 days, while it reduced by 15% in neutral paddy soil. Compared with pH 6.0 rainwater treatments, acid rainwater of pH 3.0 treatments promoted N2O cumulative emission from acidic paddy soil without straw incorporated by 51.3% higher (p <0.05) during 40 days. Acid rain changed the inhibitory effect of straw on the N2O emission, so the difference became smaller among N2O cumulative emission from the three soils with straw incorporated (AS).3.2 Rainwater, with higher ionic concentrations or with lower pH values, had no significant effects on the cumulative emission of CH4, N2O during 51 days. The CO2 cumulative emission was decreased in soils without straw by higher ionic concentration rainwater under submerged condition. After paddy soil treated with higher ionic concentrations rainwater (CR2), the CO2 cumulative emission was 26.1%(p<0.05) lower than that from paddy soil treated with rainwater CR1 under submerged condition. There was significant difference of straw decomposition rates in soils treated with different rainwater. Under submerged condition, rainwater with higher ionic concentrations or lower pH values could enhance the straw decomposition in neutral soil. The straw decomposition in CR2F groups and CR3F groups was 16.1%(p<0.01),2.6%(p<0.01) higher than that in CR1F groups, respectively. Under non-flooded condition, rainwater with higher ionic concentrations or lower pH values could inhibit the straw decomposition in neutral soil. The straw decomposition rates in CR2D groups and CR3D groups were 5.3%(p<0.05), 8.1%(p=0.111) lower than that in CR1D groups, respectively.In summary, the seasonal dynamic of greenhouse gas emission had not been changed by acid rain. During different growth stages, acid rain had different effects on the greenhouse gas product and emission from soil-crop systems. Acid rain had not changed the greenhouse gas emission from soil-rice systems after harvest. During wheat season, alkaline soil-wheat system was more sensitive than the other two soil-wheat systems. During rice season, CH4 and N2O emissions were more easily influenced by acid rain in acidic soil-rice systems and neutral soil-rice systems than that in alkaline soil-rice systems. Acid rain changed the basic physical and chemical properties of crop straw, straw decomposition rate and crop growth cost in soil-crop systems. All these led to the change of green house gas emission from soil-crop systems. Meanwhile, soil pH value and moisture played some important roles on the effects of acid rain on greenhouse gas emission.更多还原