不同填埋工艺对填埋气产生动态变化的影响

依据厌氧、准好氧填埋原理构建了填埋试验装置,对准好氧填埋CH₄、O₂浓度的动态变化进行了监测,并与厌氧填埋结构CH₄的浓度变化进行了比较.结果表明,准好氧填埋方式下、厌氧填埋方式下CH₄的平均浓度变化范围分别为7%～13%、35%～50%;准好氧填埋结构有利于减少CH₄气体的产生;CH₄浓度在准好氧填埋、厌氧填埋方式下都表现出明显的空间层次效应,呈现出下层>中层>上层的规律性;准好氧填埋结构的O₂浓度呈现上层>中层>下层的规律性.     

准好氧填埋渗滤液水质变化特性研究

在大型模拟填埋试验装置(21 m×3.8 m×6.0 m)上,研究了准好氧填埋渗滤液水质的主要指标COD_Cr、BOD、NH₃⁺-N和pH的变化特性.结果表明,准好氧填埋结构下渗滤液COD_Cr、BOD浓度下降很快,没有出现在传统填埋场累积的现象,并且封场后39周分别降为173和30 mg·L^-1;NH₃⁺-N浓度下降更为显著,第39周降为1 mg·L^-1,下降率达到99.6%,为渗滤液后续处理解决了NH₃⁺-N浓度过高的难题;pH值在前2周略低于7,第3周后一直呈弱碱性.根据实验数据,拟合了准好氧填埋结构渗滤液污染物的衰减方程.     

准好氧填埋场的温度空间变异性

利用半变异函数, 对准好氧填埋装置中温度的空间变异特性进行了研究,并对装置内部温度进行了Kriging（克里格法）插值,得到纵剖面的等温线图.对不同理论模型进行优化拟合结果表明,剖面上温度半变异函数用线性有基台值模型拟合, 效果最好.得到的理论模型参数为：变程3.5 m,基台值83.6.利用克里格法进行最优内插估值得到的温度等温线表明,高温区域一般位于填埋体中段4～16 m的3 m以上部分,低温区域一般位于填埋体两端及中段1 m以下部分.可在高温区加大通风散热效果, 以降低过高的温度; 在低温区改善好氧环境, 增大氧气含量, 从而提高温度.对剖面上温度进行加权平均后,得到的准好氧填埋堆体的温度为59.8 ℃.这一温度可作为准好氧填埋结构基本形成的参考值.     

垃圾渗滤液在土壤中的生物降解动态

通过室内好氧、厌氧2种培养,研究了3种不同填埋年限垃圾渗滤液在红壤和潮土中的生物降解动态.鲜样、天井洼样、水阁样垃圾渗滤液分别为填埋0年、4～5年和12年的垃圾渗滤液.结果表明,垃圾渗滤液在前7 d降解相对较快.在好氧培养条件下,红壤鲜样、天井洼样、水阁样渗滤液在前7 d的表观降解率为88.9%、60.5%、25.0%;潮土中的表观降解率更大,分别为96.6%、80.4%和65.0%;7 d后下降趋势均趋于平缓.在相同土壤中,填埋龄越短的垃圾渗滤液的表观降解率越大,在厌氧培养条件下的情况与此类似,但降解率不如好氧条件下高.在没有土壤介质参与的条件下(如低洼处积存的渗滤液),3种垃圾渗滤液自身降解速率均符合一级动力学方程.鲜样垃圾渗滤液降解的半衰期为12～16 d,其余垃圾渗滤液降解的半衰期为20～30 d.垃圾渗滤液一旦进入土壤环境,降解速率会大大加快.土壤处理垃圾渗滤液有一定的功效.     

氮添加对马尾松人工林土壤团聚体氮矿化及土壤酶活性的影响

土壤氮库是生态系统氮素重要的源和汇。以三峡库区马尾松（Pinus massoniana）人工林为研究对象,从团聚体视角出发分析土壤养分和酶活性对氮添加的响应规律,以及相应的变化对氮矿化的影响,为预测该地区在大气氮沉降持续增加的背景下土壤氮动态提供参考。设置4种量的氮添加处理（N₀：0 kg N hm^-2 a^-1;N₃₀：30 kg N hm^-2 a^-1;N₆₀：60 kg N hm^-2 a^-1;N₉₀：90 kg N hm^-2 a^-1）,将土壤按粒径分为>2000 μm （大团聚体）、250-2000 μm （小团聚体）和<250 μm （微团聚体）3个组分的团聚体,观察团聚体氮矿化特征。结果表明：（1）与对照相比,N₃₀和N₆₀处理提高了有机质（SOM）含量,但土壤SOM和全氮（TN）含量在N₉₀下开始出现下降;氮添加降低了土壤速效磷（aP）含量,在小团聚体中表现最为显著。除微团聚体中的POD和NAG以外,其余3种酶的活性均在N₃₀和N₆₀处理之下被提高。（2）土壤平均净硝化速率整体高于土壤平均净氨化速率;大团聚体和小团聚体中净氨化速率在氮添加处理后显著降低,大团聚体净硝化速率低于其他两个粒径;土壤净氮转化速率在N₉₀处理下最高。（3）土壤养分和无机氮含量与土壤酸性磷酸酶（AP）、N-乙酰-β-D-葡糖苷酶（NAG）、过氧化物酶（POD）、硝酸还原酶（NR）和脲酶（UE）的活性呈显著相关,酶活性变化是多因子综合作用的结果;RDA分析显示,UE与土壤净氨化速率存在显著正相关,NAG和POD是与净氮转化速率分别存在显著正相关和显著负相关的关键土壤酶。综上所述,硝化作用是土壤净氮转化的主要贡献者,微团聚体在土壤氮矿化中发挥主要作用,NAG和POD是改变土壤净氮转化的主要生物酶。此外,氮添加会引起土壤氮素的流失,引起土壤的磷限制,并对土壤养分循环产生显著影响。     

皇竹草活性氧代谢对阿特拉津胁迫的响应特征

采用水培实验研究了4个浓度（5、10、20、40 mg·L^-1）除草剂阿特拉津胁迫下,皇竹草（Pennisetum hydridum）叶片内超氧阴离子生成速率、过氧化氢（H₂O₂）含量、超氧化物歧化酶（SOD）活性、过氧化氢酶（CAT）活性、过氧化物酶（POD）活性、丙二醛（MDA）含量、原生质膜透性的变化,探讨皇竹草对阿特拉津的抗性及其生理机制。结果显示:（1）低浓度（5、10 mg·L^-1）的阿特拉津胁迫使皇竹草叶片内超氧阴离子生成速率和CAT活性升高,却使H₂O₂含量及SOD和POD活性降低,但随着培养时间的延长,培养液中阿特拉津浓度的降低导致上述指标又有恢复到正常水平的趋势;而高浓度（40 mg·L^-1）的阿特拉津胁迫则使皇竹草叶片内H₂O₂含量、SOD、POD和CAT活性持续降低。（2）在各胁迫浓度下持续胁迫10 d后,皇竹草叶片内MDA含量开始逐渐升高,并且升高幅度随着胁迫浓度的提高而明显增加,但各胁迫浓度下叶片原生质膜相对透性未见明显的变化。研究表明,皇竹草可能通过活性氧等信号分子调控自身保护酶系统的活性来缓解阿特拉津造成的伤害,从而对低浓度（5、10 mg·L^-1）的阿特拉津胁迫表现出较强抗性。     

氮添加对亚热带常绿阔叶林土壤溶液化学特性的影响

土壤溶液被称作"土壤的血液"，是土壤中各种生物化学反应的中介物质，在外界环境发生变化时，土壤溶液化学成分能在其他土壤指标尚无变化之前对环境变化做出迅速响应。为了探索持续增加的大气氮（N）沉降对森林生态系统的影响，以华西雨屏区亚热带常绿阔叶林为对象，设置对照（CK，0 g m^-2 a^-1），低N（LN，5 g m^-2 a^-1），高N（HN，15 g m^-2 a^-1）三种N处理，通过人工施加硝酸铵（2017年9月起改施硝酸钠及氯化铵）的方法模拟N沉降增加情景，N处理42个月后，使用负压土壤溶液采样器定位收集A层（37-45 cm）及B层（52-60 cm）土壤溶液，并进行分析（每月1次，为期1 a）。结果表明：对照处理中A、B两层土壤溶液NO₃^-浓度达（3.94±0.77）mg/L、（4.27±1.13）mg/L，N添加显著提高两层土壤溶液NO₃^-浓度和B层NH₄⁺浓度；N添加显著降低土壤溶液pH，且显著增加Al³⁺浓度，Ca²⁺和Mg²⁺含量有增加趋势，但影响不显著；N处理使A层土壤溶液可溶性有机碳（DOC）浓度显著降低，对两层土壤溶液芳香化指数（AI）无显著影响；两层土壤溶液电导率（EC）及氧化还原电位（Eh）显著增加；此外，两层土壤溶液中许多化学成分均呈现极显著相关，特别是NO₃^-与EC相关系数达到了0.855。本研究中，对照处理极高的NO₃^-含量以及B层土壤溶液硝酸盐浓度高于A层，表明该亚热带常绿阔叶林N的有效性超过植物和微生物的总营养需求而发生淋溶，该生态系统已达到氮饱和状态，此外N添加会显著促进土壤酸化和铝离子活化，表层土壤溶液DOC的降低一定程度反映了凋落物分解受N添加的抑制作用，显著升高的氧化还原电位可能导致土壤中某些金属元素的迁移率降低。     

色季拉山急尖长苞冷杉林不同层次土壤CO2浓度对短时降雨的响应

为阐明不同层次土壤CO₂浓度日变化特征及对短时降雨的响应,以西藏东南部色季拉山急尖长苞冷杉（Abies georgei var. smithii）林为研究对象,在自然降雨条件下,分析短时降雨及水分再分布过程中各层次土壤CO₂浓度变化特征。结果表明：在0-60 cm层次内,土壤CO₂浓度随土壤层次的加深而显著增加（P < 0.01）,二者之间呈显著对数函数关系（R=0.9764,P < 0.01）;短时降雨脉冲使表层5 cm土壤CO₂浓度显著下降,而10 cm层次土壤CO₂浓度显著增加;在降雨和水分再分布阶段,5 cm与10 cm层次土壤CO₂浓度之间极显著负相关,10、20、40 cm和60 cm之间均呈极显著正相关（P < 0.01）;5 cm层次土壤含水量显著影响0-60 cm剖面CO₂浓度,降雨阶段,二者之间极显著线性正相关（P < 0.001）,而水分再分布阶段,二者之间符合极显著幂函数负相关（P < 0.001）。即降雨引起表层土壤含水量的快速增加,显著提高土壤剖面CO₂浓度,而降雨停止后,有利于土壤CO₂向土表的释放;土壤温度和含水量对CO₂浓度的影响效应在各层次之间表现不一致,除40 cm均为正效应外,其他各层均表现为相反的影响效应。这些结果表明,短时降雨使各层次土壤含水量增加,减少土壤表面CO₂释放量,使下层土壤体系中CO₂浓度升高,在分析土壤CO₂通量时间变化时,应考虑短时降雨对不同层次土壤CO₂的影响。     

曼地亚红豆杉对甲醛胁迫的生理响应

以一年生曼地亚红豆杉(Taxus media cv.hicksii)扦插苗为材料,采用密闭箱静态熏气法,研究不同甲醛（CH₂O）浓度(0、5、10、20和40 mg·m^-3)和熏气时间（1、3、5、7 d）对曼地亚红豆杉的生理响应。结果显示:（1）在5~20 mg·m^-3CH₂O浓度下,曼地亚红豆杉叶片均无受害症状,在40 mg·m^-3CH₂O熏气1 d时,叶片开始出现受害症状,并随时间的延长逐渐加重;（2）随着CH₂O浓度的增加和熏气时间的延长,叶片MDA、Pro含量和相对电导率皆呈增加趋势,SS含量表现为先升后降,但仍显著高于对照;（3）在5 mg·m^-3CH₂O处理下,叶片SOD、CAT、PPO和GR作为第一道防线共同作用以清除过多的活性氧,其中PPO最为敏感;在10、20 mg·m^-3CH₂O处理下,SOD、POD、CAT、PPO、APX和GR共同作用加快对活性氧的清理;在40 mg·m^-3CH₂O浓度下,各酶的活性均受到抑制,其中APX、PPO和GR活性显著低于对照,而SOD、POD和CAT活性仍显著高于对照。研究表明,在中低CH₂O浓度（5~20 mg·m^-3）处理下,曼地亚红豆杉主要通过合成渗透调节物质和活性氧自由基的酶促清除机制共同作用来适应逆境,在40 mg·m^-3CH₂O浓度下,APX、PPO、GR活性受到显著抑制,细胞膜过氧化程度加剧,植物叶片受到伤害;在CH₂O浓度低于20 mg·m^-3时,曼地亚红豆杉通过自身的应激保护系统来维持正常的生理活动,表现出较强的CH₂O耐受性。     

不同酸中和对垃圾渗滤液厌氧生物处理的影响*

不同时间垃圾填埋场渗滤液用石灰絮凝、吹脱后分别经磷酸、盐酸、硫酸调pH到7,在35℃条件下进行厌氧处理。试验表明,经磷酸或盐酸中和的早期垃圾渗滤液易于厌氧生物处理,38d后其COD、BOD₅、VFA(挥发性脂肪酸)都有大幅度的降低。盐酸中和的早期垃圾渗滤液其厌氧产甲烷性能良好;但磷酸中和的其产甲烷性能被完全抑制。硫酸中和的早期垃圾渗滤液在反应过程中产生大量的硫化物,最高浓度达到1,241mg/L,对厌氧处理产生了严重的抑制,但是在第38d硫化物浓度达到最高后抑制作用慢慢减弱,其COD     

Dimethyl sulfide emission behavior from landfill site with air and water control

Municipal solid waste landfills are responsible for odors affecting the environment and human health. Dimethyl sulfide (DMS) is one of the major odorous compounds known for its low odor threshold and wide distribution. This study examined the generation, migration and emission of DMS in four artificial landfill-simulating reactors: Reactor 1 and Reactor 2, running under anaerobic and semi-aerobic conditions, respectively, without leachate recirculation; and Reactor 3 and Reactor 4, running under anaerobic and semi-aerobic conditions, respectively, with leachate recirculation. From the odor control perspective, aeration can efficiently inhibit maximum DMS headspace concentration by 31.7–93.7%, especially with the functioning of leachate recirculation. However, leachate recirculation in anaerobic conditions may double the DMS emission concentration but may also shorten the period over which DMS is effective because of the upward migration of liquid DMS in the recirculated leachate. The DMS generation was active in the acidification and methane fermentation phase of the simulated landfill and was possibly affected by the volatile fatty acid concentration, chemical oxygen demand, total organic carbon concentration and pH of the leachate, as well as total organic carbon in the refuse. Most significantly, DMS emission can be effectually dealt with by aeration along with leachate recirculation.     

Comparison of Bacteria and Archaea communities in municipal solid waste, individual refuse components, and leachate

Refuse decomposition in landfills is a microbially mediated process that occurs primarily under anaerobic conditions. Because of limited moisture conditions, hydraulic transport as a means of cellular translocation within the landfill appears limited, especially during the initial stages of decomposition. Thus, microbial communities within the incoming refuse serve as a primary source of facultative and obligate anaerobic microorganisms that initiate refuse decomposition. Fresh residential refuse was collected five times over 26 months, and microbial communities in these samples were compared with those in individual refuse components and decomposed refuse. Bacterial and archaeal community structures were determined using T-RFLP. The Bacterial microbial community richness was correlated (r(2) = 0.91) with seasonal differences in ambient air temperature. Analysis of the results shows that fresh refuse is most likely not the source of methanogens in landfills. Microbial communities in the solid and leachate phases were different, indicating that both matrices must be considered when characterizing microbial diversity within a landfill.     

Settlement Prediction for Municipal Solid Waste Landfills Using Power Creep Law

One of the most important factors that affect the post-closure operation of a landfill is the settlement of refuse and foundation material. Prediction of settlement of refuse is complex because of the mechanisms of settlement and the heterogeneity of the refuse. The settlement of a landfill can be estimated using a simplified method, the Power Creep Law. Based on the analysis of published data measured in the field from four landfills, a correlation is proposed between two parameters, reference compressibility and rate of compression, required to predict the refuse settlement using the Power Creep Law. The settlement-time relationships of waste landfills predicted using the proposed correlation show better agreement with the measured settlements than the settlements predicted using average values or some arbitrary combination of the parameters.     

In situ simultaneous organics and nitrogen removal from recycled landfill leachate using an anaerobic-aerobic process

An anaerobic-aerobic process including a fresh refuse landfill reactor as denitrifying reactor, a well-decomposed refuse reactor as methanogenesis reactor and an aerobic activated sludge reactor as nitrifying reactor was operated by leachate recirculation to remove organic and nitrogen simultaneously. The results indicated that denitrification and methanogenesis were carried out successfully in the fresh refuse and well-decomposed landfill reactors, respectively, while the nitrification of NH(4)(+)-N was performed in the aerobic reactor. The maximum organic removal rate was 1.78 kg COD/m(3)d in the well-decomposed refuse landfill reactor while the NH(4)(+)-N removal rate was 0.18 kg NH(4)(+)-N/m(3)d in the aerobic reactor. The biogas from fresh refuse reactors and well-decomposed refuse landfill reactors were consisted of mainly carbon dioxide and methane, respectively. The volume fraction of N(2) increased with the increase of NO(3)(-)-N concentration and decreased with the drop of NO(3)(-)-N concentration. The denitrifying bacteria mustered mainly in middle layer and the denitrifying bacteria population had a good correlation with NO(3)(-)-N concentration.     

In situ nitrogen removal in phase-separate bioreactor landfill

The feasibility of in situ nitrogen removal in phase-separate bioreactor landfill was investigated. In the experiment, two sets of bioreactor landfill systems, namely conventional two-phase and in situ nitrogen removal bioreactor landfills, were operated. The in situ nitrogen removal bioreactor landfill (NBL) was comprised of a fresh-refuse filled reactor (NBLF), a methanogenic reactor (NBLM) and a nitrifying reactor (NBLN), while the two-phase bioreactor landfill (BL) used as control was comprised of a fresh-refuse filled reactor (BLF) and a methanogenic reactor (BLM). Furthermore, the methanogenic and nitrifying reactors used aged refuse as bulk agents. The results showed that in situ nitrogen removal was viable by phase-separation in the bioreactor landfill. In total 75.8 and 47.5 g of nitrogen were, respectively, removed from the NBL and the BL throughout the experiment. The methanogenic reactor used the aged refuse as medium was highly effective in removing organic matter from the fresh leachate. Furthermore, the aged refuse was also suitable to use as in situ nitrification medium. The degradation of fresh refuse was accelerated by denitrification in the initial stage (namely the initial hydrolyzing stage) despite being delayed by denitrification in a long-term operation.     

Effects of in situ nitrogen removal on degradation/stabilization of MSW in bioreactor landfill

The effects of in situ nitrogen removal on degradation of municipal solid waste (MSW) in bioreactor landfill system were investigated. The in situ nitrogen removal bioreactor landfill (NBL) consisted of fresh-refuse filled, methanogenic and nitrifying reactors was operated. The two-phase bioreactor landfill (BL) comprised of fresh-refuse filled and methanogenic reactors was used as control. The methanogenic and nitrifying reactors were all loaded with aged refuse whose placement time was 6-7 yr. Furthermore, the nitrifying reactor was in situ aerated. The results showed that the degradation of fresh-refuse was delayed and CH4 production also was reduced in the in situ nitrogen removal bioreactor landfill. It was feasible to perform in situ ammonia nitrification in aged refuse. Moreover, the efficiency of oxygen utility was high during the in situ nitrification because of the porous characteristic of aged refuse. Supplementing only 8.5mg O2 mg(-1)Nd(-1) to aged refuse could make ammonia removed completely. However, aeration did not accelerate the further stabilization of aged refuse.     

Molecular phylogenetic analysis of dominant microbial populations in aged refuse

The phylogenetic analysis of dominant microbial populations in 8-year-old refuse samples was done in terms of the whole Bacterial and Archaeal domains. The results indicated that the Bacterial 16S rRNA genes sequences from the aged refuse were largely affiliated with the genus Bacillus, and that more than 60 % of the Archaeal sequences were closely related to the methanogenic archaeon. Some inferentially identified extremophilic organisms, particularly alkaliphiles and/or halophiles, were noted to be present in the aged refuse. Moreover, molecular evidence for the occurrence of ammonia-oxidizing Archaea in aged refuse was reported, which opens up avenues for elucidating its role in ammonia transformation in landfill systems. It seems reasonable to assume that the highly complex environment within the landfill systems may select for microbial populations with versatile metabolism and strong adaptation. These findings underline the need for further biochemical and ecological study of these organisms in aged refuse.     

Colour removal from landfill leachate by coagulation and flocculation processes

A study was conducted to investigate the efficiency of coagulation and flocculation processes for removing colour from a semi-aerobic landfill leachate from one of the landfill sites in Malaysia. Four types of coagulant namely aluminium (III) sulphate (alum), ferric (III) chloride, ferrous (II) sulphate and ferric (III) sulphate were studied using standard jar test apparatus. Results indicated that ferric chloride was superior to the other coagulants and removed 94% of colour at an optimum dose of 800 mg/l at pH 4. The effect of coagulant dosages on colour removal showed similar trend as for COD, turbidity and suspended solids. This suggested that colour in landfill leachate was mainly contributed by organic matters with some insoluble forms that exhibited turbidity and suspended solids readings. The results from this study suggested that ferric chloride could be a viable coagulant in managing colour problems associated with landfill leachate.     

Performance and bacterial compositions of aged refuse reactors treating mature landfill leachate

Aged landfill leachates become more refractory over time and difficulty to treat. Recently, aged refuse bioreactors show great promise in treating leachates. In this study, aged refuse bioreactors were constructed to simulate landfill leachate degradation process. The characteristics of leachate were: COD_cr, ∼2200 mg/L; BOD₅, ∼280 mg/L; total nitrogen, ∼2030 mg/L; and ammonia, ∼1900 mg/L. Results showed that bioreactor could remove leachate pollutants effectively at hydraulic loading of 20 L/m³ d. The removal rate reduced when hydraulic loading doubled or temperature lowered. Effluent recirculation could alleviate the temperature effect. Combining aged refuse and slag biofilters could treat leachate more efficiently. Pyrosequencing analysis indicated that bacteria from Pseudomonas, Lysobacter, Bacillus and δ-proteobacter, Flexibacteraceae were more abundant in the samples. The Shannon index decreased at lower temperature, while evenness and equitability increased with recirculation. We suggest that filter medium and temperature may be the main factors for shaping bacterial community structure.