为探究脱硫石膏和生物炭混施对稻田CO2、CH4减排和碳收支的影响,在黄壤性稻田中设置了生物炭与脱硫石膏施用剂量比不同的6个处理,并利用静态箱-气相色谱法对土壤CO2、CH4排放通量进行了为期一年的监测.试验的6个处理分别为裸地(B)、种植水稻(R)、种植水稻+4 t·hm-2生物炭(RC4)、RC4+4 t·hm-2脱硫石膏(RC4G4)、RC4+8 t·hm-2脱硫石膏(RC4G8)和RC4 + 16 t·hm-2脱硫石膏(RC4G16).结果表明,处理R在稻季的CH4排放量为86 kg·hm-2;单施生物炭使CH4排放量增加了52%,进一步混施脱硫石膏则使CH4排放量下降了69%～91%.各处理在休闲期的CH4排放量都比较低(6.24～13.4 kg·hm-2).施用生物炭和脱硫石膏对稻季土壤CO2排放无显著影响;与其他处理相比,RC4G4处理在休闲期的CO2排放量有所增加.不同处理的土壤CO2年排放量为4 525～6 634 kg·hm-2,其中休闲期的贡献率为68%～76%.就全年而言,仅RC4G16处理的碳输入略大于碳输出,表现为碳中和效应;其他处理则皆表现为大气碳源,净排放量为573～4 065 kg·hm-2.综上所述,本试验中单施生物炭促进了温室气体排放,而脱硫石膏的施用抵消了生物炭对温室气体减排的负面效应,且施用效果随剂量的增加而增强.
To evaluate the effect of various environmental conditions on the stabilization of As in soil of development land， FeCl 3 with different additions （Fe/As molar ratio 2:1， 3:1， 4:1， 5:1， 6:1， 7:1， and 8:1， respectively） was added to stabilize As in contaminated soil at a smelting plant in Liaoning province. The suitable amount of FeCl 3 for stabilization was selected by measuring the leaching concentrations and fractions of As. The effects of FeCl 3 addition on As stabilization under the various environmental conditions were assessed by measuring the leaching concentration of As in stabilized soil with different pH levels and different liquid-solid ratios. The results showed that compared with no FeCl 3 addition， the leaching concentration of As decreased by 84.9%～92.8% among all treatments （P＜0.05）， and the minimum leaching concentration of As occurred under the treatment of Fe/As at a molar ratio of 6:1， and the stabilization effect was the best. The addition of FeCl 3 promoted the transformation of As from the nonspecific adsorption state and specific adsorption state with high activity to the residual state with low activity， and the available As content decreased by 6.9%～8.4%. The leaching concentration of As under neutral and alkaline extraction conditions increased significantly， compared to those under the acidic extraction conditions. The leaching concentration of As was the lowest when the pH of the extraction solution was 4， and it was the highest at a pH of 13; the leaching concentration of As increased by 584.4%， comparing the two conditions. The leaching concentration of As increased significantly （P＜0.05） under the lower liquid-solid ratio of the extraction system， compared to the higher liquid-solid ratio of the extraction system. The leaching concentration of As was the lowest and the leaching rate was the largest when the liquid-solid ratio of the extraction system was 20:1， while the leaching concentration of As was the highest and the leaching rate was the lowest when the liquid-solid ratio of the extraction system was 1:1. The results showed that FeCl 3 addition can effectively reduce the leaching concentration of As by changing the As fractions in soil of development land， and the alkaline and the lower liquid-solid ratio of extraction system increased the environmental risk of As in stabilized soil. It is thus recommended to select the corresponding pH and liquid-solid ratio for an extraction system according to the actual soil environment so as to safely evaluate the stabilization effect and the environmental risk of As in soil of development land.
为探究覆膜措施对津市藠头产量及根际土壤细菌群落多样性、结构、生态功能、物种之间网络互作的影响,本研究采集了未覆膜、覆普通地膜、覆蓝色地膜3个处理下的藠头根际土壤,利用高通量测序技术和生物信息学的相关方法进行研究.结果表明:覆膜措施提高了藠头产量,其中未覆膜处理产量为29 766.7 kg·hm-2,普通地膜处理产量为31 466.7 kg·hm-2,增产5.7%,蓝色地膜处理产量为39 966.7 kg·hm-2,增产34.3%.覆膜处理显著改变了细菌群落结构,并显著降低了细菌群落多样性.此外,藠头根际土壤细菌群落对不同地膜处理的响应不同,在门和属水平上均存在一定差异.网络分析结果表明,未覆膜处理具有124个模块,普通地膜和蓝色地膜处理的根际细菌分子生态网络分别具有77个和80个模块.覆膜措施使藠头根际细菌分子生态网络的模块数降低,这可能会导致细菌群落生态功能多样性降低.覆膜措施还导致根际细菌关键物种改变.基于功能预测,相较于未覆膜处理,覆盖蓝色地膜显著提高了尿素分解功能(P＜0.05),而普通地膜处理相对于蓝色地膜处理能显著提升好氧氨氧化与硝化作用(P＜0.05).研究表明,蓝色地膜处理更有利于藠头的增产,覆膜措施改变了藠头根际细菌群落结构、关键物种及物种互作关系.此外,尚不能忽视覆膜措施对农田土壤细菌生态环境的潜在风险.
Environmental hazards and remediation of pharmaceuticals and personal care products（PPCPs）have recently received growing attentions. Thus, investigating the purification effect of azolla on domestic sewage containing PPCPs is important. Representative PPCPs gemfibrozil, carbamazepine, and azolla were used as test materials, and indoor simulation culture tests were conducted to investigate the growth of azolla in domestic wastewater at both different incubation times（1, 2, 4, and 8 d）and different initial concentrations of PPCPs(0,1, 10, 100, and 1 000 μg·L -1 ), as well as the removal rates of conventional pollutants（ammonia nitrogen, NH3-N; nitrate nitrogen, NO 3 --N;total phosphorus, TP; chemical oxygen demand, COD）and PPCPs. With an increase of the initial concentration of PPCPs in domestic wastewater, the relative growth rate and tolerance index of azolla showed a trend of first increasing and then decreasing, and the growth of azolla was inhibited under the treatment of 100 and 1 000 μg · L -1 PPCPs. Compared with the control, the removal effect of azolla on nitrogen and phosphorus was significantly enhanced under 1 and 10 μg·L -1 PPCPs treatment（P＜0.05）, but was significantly weakened under100 and 1 000 μg·L -1 PPCPs treatment（P＜0.05）. When treating with different initial concentrations of PPCPs, the effect of azolla on COD removal was significant, and the COD removal rate increased with the increase of the initial concentration of PPCPs. The removal effect of azolla on gemfibrozil and carbamazepine was enhanced with increasing incubation time. The removal rate of gemfibrozil increased with increasing initial concentration of PPCPs(except for 1 000 μg·L -1 PPCPs treatment), whereas the removal rate of carbamazepine decreased with increasing initial concentration of PPCPs. Azolla has a good removal effect on both PPCPs and conventional pollutants other than ammonia nitrogen in domestic wastewater and can be used as a remediation treatment plan for domestic wastewater containing typical PPCPs.
In order to clarify how disinfection by-products（DBPs）were produced during disinfection, in this study, the samples were collected from the effluent of different treatment units in a typical swine wastewater treatment plant, which comprised of anaerobic digestion and an improved A~2O process. The comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry（GC×GC-qMS）combined with three-dimensional fluorescence（3D-EEM）was applied to analyze the effect of organic compounds on DBPs generation. A total of 38 DBPs in 10 categories were found with a high concentration of chloro-phenols and chloro-heterocyclic DBPs observed in disinfected raw swine wastewater. Anaerobic digestion and the improved A~2O process eliminated the majority of the DBP precursors. After anaerobic digestion, chloro-phenols and chloro-heterocyclic DBPs were reduced by 88.50% and 77.64%, respectively. However, an increase in the concentration of esters and hydrocarbons after anaerobic digestion, increased the production of chloro-esters and chloro-hydrocarbons by 392.18% and 68.37%, respectively. Improved A~2O process could remove certain precursors of chloro-esters. The increase in C/N ratio, decrease in H/C ratio, and increase in HIX of organic compounds indicated the enhancement of humification degree, stability degree, and aromaticity in the effluent of improved A~2O. It would partly explain the increase in chloro-hydrocarbons DBPs after disinfection. Anaerobic digestion and improved A~2O process removed relatively little of the precursors of chloro-esters and chloro-hydrocarbons; thus, the swine wastewater treatment system needs to strengthen its removal capacity.
为预测碳达峰时间和峰值,综合分析减排潜力,本研究使用生命周期评价法对2004—2018年棉花生产碳排放进行核算,基于STIRPAT模型进行模拟,结合Kaya恒等式确定模型变量为技术效率、生产规模、进口数量、农业经济和城镇化率,通过岭回归确定系数将2019—2035年碳排放情景分为高减排度情景(HERS)、中等减排度情景(MERS)、基准情景(BS)3类进行变量设定和预测.结果表明:2004—2018年中国棉花生产碳排放及其增长率呈缓慢上升趋势,2018年碳排放达到最高值(24.34万t),新疆的碳排放值最大(2018年占比86.8％)并呈明显增加的趋势,肥料生产与施用、灌溉用电、农膜是生产过程中的主要碳排放构成因素.用于模拟中国棉花生产碳排放的STIRPAT模型性能良好(R2=0.866,adjusted R2=0.792,P=0.001),自变量均对因变量有显著影响(P<0.01),生产规模、城镇化率和技术效率是主要宏观影响因素.结果显示2019—2035年HERS、MERS、BS下中国棉花生产碳达峰时间分别是2021、2025、2031年,峰值分别为24.89万、26.12万、27.25万t.研究表明,在未来棉花生产向着集约化和规模化方向发展的同时,提高生产效率以及加快低碳种植技术和土壤固碳技术的研发与推广是推动棉花低碳生产的主要突破点.
为探讨喷施微生物合成纳米Se(B)对水稻Se、Cd吸收的影响与籽粒富Se降Cd的效果,本研究通过盆栽试验,研究微生物合成SeNPs喷施5(B5)、10(B10)、20(B20)mg·L-1对水稻Se、Cd吸收、转运效应,以及与无机Se(S)、有机Se(M)喷施对比,比较水稻籽粒富Se降Cd效果.结果表明,与不喷Se(CK)、S、M处理相比,B5、B10、B20处理提高籽粒Se含量分别为227.52%～366.46%、3.38%～23.31%、30.54%～42.57%,降低籽粒Cd含量分别为10.14%～55.07%、4.08%～36.37%、9.03%～40.77%,籽粒富Se降Cd效果表现为B＞S＞M＞CK,B处理中,籽粒富Se降Cd效果以喷施20 mg·L-1浓度最佳,高Se与低Se水稻品种间对Se、Cd吸收差异不显著.与CK处理相比,B处理促进了水稻叶片中Cd在细胞壁、液泡组分中的积累,减少了叶绿体、线粒体组分中的积累,促进了叶片中Se在细胞壁、叶绿体组分中的积累,减少了线粒体、液泡组分中的积累.主成分分析和Pearson相关矩阵表明,水稻各部位Se与Cd含量呈负相关关系(P≤0.01).与CK、M处理相比,B处理对水稻Se生物富集系数分别提高 20.63%～264.70%、20.37%～32.86%,表现为S＞B＞M＞CK,B5、B10、B20处理对水稻Cd富集系数分别降低9.10%～25.10%、5.70%～9.65%、10.64%～22.10%,表现为CK＞M＞S＞B.供试水稻Se转移系数表现为根-茎＜茎-籽粒＜茎-叶,Cd转移系数表现为根-茎＜茎-叶＜茎-籽粒,与CK、S、M处理相比,B处理均促进了Se向籽粒的转移,减少了Cd向籽粒的富集.与CK、S、M处理相比,B处理均显著提高了水稻叶片SOD、CAT、POD、APX、PAL、Pro、GSH含量,降低了MDA、H2O2的含量,高Se水稻品种(泰丰优208)对提高水稻抗氧化酶活性与抗氧化性物质含量效果高于低Se水稻品种(桂野丰).因此,叶面喷施微生物合成SeNPs在调控水稻Se、Cd吸收、转运与籽粒富Se降Cd方面有着更显著的优势.
In order to improve the representativeness of soil monitoring sites to obtain soil information more accurately and implement effective management measures. In this study， an optimization method for soil environmental quality monitoring site layout， based on characteristic representativity is proposed. This method builds feature space， based on the attribute distribution of several auxiliary variables that are strongly correlated with the monitoring target variables; in this study， the feature space was stratified and coded by the conditional Latin hypercube method. The sampling sequence was determined by calculating the stratified impact level of the feature space and a highly representative sampling scheme was obtained based on point-by-point sampling. The study considered the Shunyi District of Beijing， as an example to optimize the layout of monitoring sites using soil type， soil texture， land use type， and slope as auxiliary variables， and compared with the simple random sampling， spatial stratified sampling， and conditional Latin hypercube sampling methods （cLHS）. The results showed that compared with the other three methods， the feature space coverage rate of the proposed method was approximately 15% higher on average. The time consumption of the proposed method was much less than that of the cLHS method and slightly higher than those of the simple random sampling and spatial stratified sampling methods. The obtained uncertainty of the monitoring sites’ layout scheme for the proposed method was significantly lower than those of the other three methods. The distribution characteristics of heavy metal contents were highly similar to the overall data. In conclusion， this method can significantly improve the representation of the monitoring sites in the feature space and effectively reflect the overall distribution characteristics of soil attributes in the survey area， which can provide a reference for a follow-up investigation and monitoring of soil information.
为探明粉碎秸秆还田量对宁夏银川北部地区土壤碳平衡及真菌群落多样性的影响,实现农业废弃物资源化利用、固碳减排、盐碱地改良的目标.研究建立2020-2022年短期粉碎秸秆还田试验,依据秸秆原位消纳原则,设置全量还田(CS9000)、2/3全量还田(CS6000)、1/3全量还田(CS3000)、未还田(CS0)4个处理,分析还田2年后不同还田量对土壤碳排放、水热盐碱因子变化及真菌微生物群落多样性影响.结果表明:相比CS0处理,粉碎秸秆还田后土壤全盐降低7.94%～19.57%,地温提高0.11～0.58℃,其中,CS9000处理抑盐增温效果明显,同时,该处理显著增加碳排放量与微生物异养呼吸碳,而CS6000处理相比其他处理显著增加净初级生产力固碳量,净生态系统生产力固碳量也分别比CS9000、CS3000、CS0处理显著增加27.11%、29.41%、35.22%.通过计算碳收支平衡得出CS6000、CS3000处理下农田生态系统是大气CO2的"汇",其中,CS6000处理对碳平衡提升效果最好,有助于增加土壤碳汇.另外,粉碎秸秆还田后土壤真菌多样性变化较大,CS6000处理相比CS0处理显著提高Schao1、Hshannon指数,且该处理可明显增加子囊菌门(Ascomycota)、粪壳菌纲(Sordariomycetes)、被孢霉属(Mortierella)、镰刀菌属(Fusarium)优势群落相对丰度.从固碳减排、微生物多样性的角度考虑,粉碎秸秆还田量为6 000 kg·hm-2为该地区最佳还田量.
为筛选耐Cd种质资源并研究生姜耐Cd机理,以华东、华中和西南主产区的5个主栽品种凤头姜、贵州小黄姜、罗平小黄姜、竹根姜和山东大姜为试验材料,设置对照(CK)和镉(Cd)处理,两处理的水分处理一致,CK无外源添加Cd.测定生姜生长指标和生理指标,利用主成分分析和隶属函数法对5个品种苗期的耐Cd性进行综合评价.结果表明:Cd处理显著(P＜0.05,下同)降低了生姜的株高、茎粗、过氧化氢酶(CAT)活性、光合色素含量及PSⅡ最大光化学效率(Fv/Fm)、光化学猝灭系数(qP);显著升高了叶片中的硫代巴比妥酸反应物(TBARS)含量、超氧化物歧化酶(SOD)活性及非光化学猝灭系数(NPQ);山东大姜的过氧化物酶(POD)活性、游离脯氨酸(Pro)与类胡萝卜素(Car)含量无显著变化.综合评价5个品种生姜的耐Cd性排序为山东大姜＞贵州小黄姜＞罗平小黄姜＞凤头姜＞竹根姜.相关性分析结果表明茎粗、Car含量与综合评价值(D值)呈极显著(P＜0.01)正相关,叶片TBARS含量、POD活性与D值呈显著负相关(P＜0.01).竹根姜Cd含量是山东大姜的3.57倍,Cd主要富集在根和叶中,山东大姜的Cd主要富集在根中.5个品种中山东大姜耐Cd性最强,竹根姜耐Cd性最差.茎粗、Car含量、叶片TBARS含量和POD活性可以作为生姜耐Cd品种筛选的主要参考指标.
为探究江苏省宜兴市这一典型天然富硒区土壤硒的空间分布及影响因素,采集表层土壤(0～20 cm)4 461件,利用统计学和相关分析方法研究土壤硒的空间分布特征和影响因素.结果表明:研究区表层土壤硒含量范围为0.06～1.74 mg·kg-1,均值为0.42 mg·kg-1,是全国土壤硒元素背景值(0.29 mg·kg-1)的1.45倍,是江苏表层土壤硒含量均值(0.20 mg·kg-1)的2.1倍.土壤硒含量的变异系数为43.47%,表明土壤硒元素呈中等程度变异.半方差函数分析显示,土壤硒空间分布的最优模型为球状模型,块金效应值为0.568,具有较强空间相关性,变程为30 250 m,空间自相关范围较大.研究区土壤硒总体空间分布特征为南部低山丘陵显著高于北部太湖堆积平原,碎屑岩类成土母质风化形成的土壤硒含量高,同时土地利用方式为园林地、海拔较高、地形起伏大的丘陵山区的土壤硒含量也相对较高.土壤理化性质、人类活动对土壤硒的分布也有影响,pH低、有机质含量高的土壤硒含量高,距离金属矿点近、距离湖泊河流越远的土壤硒含量高.通过分析土壤硒含量的影响因素可知,在选取地区开发利用富硒土地资源、发展富硒特色产业时优先考虑的因素是成土母质,其次为土壤理化性质和地形地貌.
为探究除草剂草甘膦和杀虫剂毒死蜱对三沙湾滩涂土壤细菌群落结构及多样性的影响,利用五点采样法于2021年3月采集福建省霞浦县东吾洋沿岸滩涂土壤,通过模拟自然环境在室内进行农药添加试验,两种农药分别设置3个浓度,即草甘膦5、25、125 mg·kg-1,毒死蜱6、30、150 mg·kg-1,染毒时间分别取3d和10 d,以未添加农药的滩涂土壤为对照.使用Illumina MiSeq PE300二代高通量测序平台对各处理及对照滩涂土壤细菌16S rRNA基因的V3～V4区进行测序,分析不同处理土壤细菌群落组成结构和功能差异及其影响因素.结果表明:草甘膦和毒死蜱显著降低了三沙湾滩涂土壤细菌α多样性(P＜0.05).门水平上,滩涂土壤中优势菌群包括变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)、绿弯菌门(Chloroflexi)和ε-变形菌门(Epsilonbacteraeota),其丰度占比分别为 32.69%、20.38%、12.46%和 9.14%,农药处理后其优势菌群主要由变形菌门、厚壁菌门和拟杆菌门(Bacteroidetes)组成.属水平上,对照土壤以深海芽孢杆菌属(Thalassobacillus)、海杆菌属(Marinobacter)、硫卵菌属(Sulfurovum)和芽孢杆菌属(Bacillus)为主,农药处理后其优势菌群海杆菌属和芽孢杆菌属得到大量扩增,其他菌属呈现不同程度的衰退.Tax4Fun功能分析结果显示,各处理滩涂土壤的功能类群主要集中在新陈代谢方面,不同阶段细菌功能主要分布于38类代谢通路.经农药处理,滩涂土壤中氨基酸代谢、异生素降解和代谢、脂类代谢、萜类化合物和聚酮的代谢以及环境信息处理中膜运输、细胞运动和细胞运输同化作用等功能得到明显增强,而能量代谢、聚糖生物合成和代谢、遗传信息处理等功能有不同程度的削弱.由此可见,化学农药的加入降低了三沙湾滩涂土壤细菌群落多样性,微生物多样性的损失将改变生态系统的功能,降低生态系统的稳定性.
为确定适用于沼液浓缩的低污染高截留超滤(UF)膜孔径,选取鸡粪沼液为浓缩对象,采用膜孔径为500、100、50、30 KD的UF膜(平均膜孔径分别为20、6、4 nm和3nm)进行浓缩处理,考察不同孔径UF膜对沼液浓缩过程中养分和风险污染物迁移的调控作用.结果表明:不同孔径UF膜的水通量均呈现快速降低-平稳-再降低的三段式现象,整体降低38%～49%,且低孔径膜下降更为明显.不同孔径UF膜对沼液中有机质的截留效果整体差异不显著,对TP、TN、TK等养分的截留率随孔径缩小而逐渐提高.同时,不同孔径UF膜对Ca、Mg、Fe和Zn4种中微量元素的截留性能相似,对重金属和抗生素的截留性能也随孔径的缩小而逐步提升,对Cu和Pb的截留率均可达到100%.综合稳定水通量、养分截留和风险污染物富集,确定适用于沼液浓缩的UF膜孔径为100 KD.
针对当前我国农业面源污染治理存在因机制不完备导致的治理信息安全隐患大、问题企业追责难、监管效率低下等问题,提出了基于区块链的农业面源污染治理信息管理及监管机制.在探讨区块链与农业面源污染治理的系统结构协同和机制功能协同的基础上,搭建了农业面源污染治理Fabric联盟链框架体系,并从农业面源污染治理信息管理和监管两个方面进行了机制创新.研究表明,区块链技术的创新应用将在农业面源污染治理制度和模式上进行突破,保障农业面源污染治理信息的安全性,促进相关利益主体行为得到有效监管,降低治理成本和复杂度,形成政府和农业生产经营主体间信息自由传递、流动的立体网络和治理逻辑.
以河套灌区为研究区,采用SWAT模型估算该灌区流域面源污染负荷,分析面源污染的空间分布特征和年际变化趋势,识别灌区面源污染关键区域和关键污染源.结果表明:2001-2020年灌区内总氮、总磷负荷年平均值分别为565.23 kg·a-1和108.93 kg·a-1;面源氮磷负荷高值区主要分布于灌区中部,低值区主要分布于灌区北部;面源氮磷负荷在中部地区表现为先上升再下降趋势,西部地区表现为先下降再上升趋势,而在东部及北部地区表现为下降趋势;灌区内在产生生活污水过程中产生的氮类和磷类污染物贡献率最大,达到44.51%,其次就是种植业源和养殖业源,贡献率分别为28.76%和26.73%,其中种植业源贡献率会受降雨量变化影响,从东部的乌拉特前旗站向西至杭锦后旗站水量逐渐减少,种植业源贡献率也表现出东部高于西部.生活污水作为第一污染来源,需要严格控制其排放,应着重对厕所粪尿通过排入化粪池等处理方法将其中有害物质转化为沼液等对农作物有用的物质.
为探索污泥堆肥在铬污染耕地上的资源化合理利用,本研究通过田间试验,设置了空白对照、常规施肥、单施污泥堆肥以及不同比例污泥堆肥替代化肥配施处理,并将其与有机肥替代化肥进行效果对比,从玉米生物量、铬吸收、土壤铬含量及其有效性等方面探讨污泥堆肥施用对作物生长和土壤铬累积的影响.结果表明:相比于对照,不同用量污泥堆肥均能促进玉米生长,显著提高玉米产量,增产范围为15.24%～36.65%,其中污泥堆肥替代20%化肥配施对玉米的增产效果最好,相较于常规施肥增产了7.16%.各替代化肥处理下玉米籽粒中重金属铬含量均低于《食品安全国家标准食品中污染物限量》(GB 2762-2022)中的限值,其中污泥堆肥30%替代化肥处理玉米籽粒降铬效果最好.污泥堆肥施用量在750～1 500 kg·hm-2时玉米地上部分对铬的携出量大于污泥铬的携入量.当季施用污泥堆肥对土壤总铬含量无显著影响,且各替代化肥处理下土壤有效态铬含量相较对照降幅为5.59%～12.68%.施用污泥堆肥不会对作物产生盐害并且能够缓解土壤酸化、提高土壤有机质、全氮以及速效氮磷钾含量.综合来看,在铬污染耕地,污泥堆肥替代化肥施用不仅有利于提高玉米产量,还能显著降低籽粒铬含量,并且施用量为1 500 kg·hm-2时即能保障玉米安全、高产,且不会对土壤造成富集铬的风险,并能有效提高土壤各养分指标.
本研究以发光细菌Photobacterium kishitanii为模式生物,通过发光抑制试验研究了5种重金属与四环素类抗生素对发光细菌的急性单一毒性与联合毒性.利用毒性单位法(TU法)表征联合毒性,并采用浓度加和模型(Concentration addtion,CA模型)与独立作用模型(Independent action,IA模型)预测二元混合体系对发光细菌的联合急性毒性.研究表明:单一毒性大小排序为硝酸铅＞七水硫酸锌＞氯化镉＞盐酸土霉素＞盐酸金霉素＞盐酸强力霉素＞盐酸四环素＞五水硫酸铜＞重铬酸钾.重金属之间的联合毒性主要表现为协同作用,重金属与四环素类抗生素的联合毒性主要表现为相加作用和拮抗作用,四环素类抗生素之间的联合毒性主要表现为拮抗作用.研究表明,重金属与四环素类抗生素共存会对发光细菌产生不同的毒性效应,因此在评价环境复合污染时应考虑联合毒性效应.
为研究畜禽粪便好氧堆肥过程氨气(NH3)与温室气体的排放特征及协同减排机制,以鸡粪与蘑菇渣为原料,设置9组不同条件的好氧堆肥正交实验,并进行为期45d的跟踪监测,了解好氧堆肥过程基本理化参数变化,分析NH3和温室气体的排放规律及最佳减排条件,探究微生物群落与环境因子、气体排放通量之间的相关性.结果表明:含水率与碳氮比(C/N)变化影响整个堆肥进程,经45d堆肥后,大多数处理组的堆肥均已经完全腐熟,且添加一定比例的椰壳生物炭与钙镁磷肥可以提高堆肥腐熟度.NH3和4种温室气体(CH4、N2O、CO、CO2)在堆肥前期(1～22 d)排放通量较高,人工翻堆会增加气体排放通量.NH3和温室气体排放的影响因子和最佳减排条件各不相同,存在"此消彼长"的关系.对NH3、CH4、N2O排放影响较大的因子是椰壳生物炭占比、钙镁磷肥占比和通风速率,有利于这3种气体协同减排的条件为含水率60%、椰壳生物炭0或5%、钙镁磷肥0或5%或10%、通风速率0.12 L·min-1·kg-1,其中含水率60%、椰壳生物炭占比5%、通风速率0.12 L·min-1·kg-1是NH3和CH4协同减排的最佳条件.整个堆肥过程中,门水平与属水平的微生物群落相对丰度均发生明显变化,C/N和温度是微生物群落变化的主要驱动因素;堆肥前期(22d前),门水平的优势菌为Firmicutes、Actinobacteria、Bacteroidetes和Proteobacteria,其中Firmicutes对NH3与温室气体的排放具有显著影响.研究表明,鸡粪好氧堆肥过程中影响NH3和温室气体排放的因子很多,通风条件下进行调理剂种类及配比优选有望实现NH3、CH4和N2O的协同排放.
为探究水稻秸秆和蚯蚓联合抗Cr细菌对Cr污染土壤的修复效果和机制,本研究通过室内模拟试验探讨细菌(寡氧单胞菌,Stenotrophomonas sp.,F)、水稻秸秆(S)、细菌+水稻秸秆(SF)、水稻秸秆+蚯蚓(赤子爱胜蚓,Eisenia foetida,SE)和细菌+水稻秸秆+蚯蚓(SFE)对50、300 mg·kg-1 Cr(Ⅵ)污染土壤的修复效果,生物有效态Cr的变化及总Cr和Cr(Ⅵ)在各粒径团聚体中的分布.结果表明:在试验早、中、后期各处理的总Cr和Cr(Ⅵ)去除率逐渐增加,在50、300 mg·kg-1 Cr(Ⅵ)暴露后期SFE处理的总Cr和Cr(Ⅵ)去除率最高,其总Cr去除率分别为35.68%、35.29%,Cr(Ⅵ)去除率分别为99.28%、75.33%.SFE处理显著降低了土壤氧化还原电位,增加了土壤pH和有机质含量,并促进了微团聚体凝聚胶结为大团聚体.在0、50、300 mg·kg-1 Cr(Ⅵ)暴露下SE处理大团聚体的占比最高,与CK相比分别增加了14.57、9.51、9.85个百分点,与SFE相比分别增加了3.73、4.09、3.28个百分点.各处理对Cr化学形态的影响为SFE＞SF＞SE＞S＞F,在整个试验过程中除F处理外,其余处理中各化学形态的占比都随试验时间的延长而稳定变化.与CK相比,在50、300 mg·kg-1 Cr(Ⅵ)暴露后期SFE处理中可交换态的占比分别降低了35.55、21.02个百分点,残渣态的占比分别增加了22.45、12.51个百分点.总Cr主要分布在大团聚体中,Cr(Ⅵ)主要分布在微团聚体中,所有处理各粒径团聚体中的总Cr和Cr(Ⅵ)含量都随试验时间的延长而降低,SFE处理显著降低了大团聚体中总Cr和微团聚体中Cr(Ⅵ)的含量.研究表明,在50、300 mg·kg-1 Cr(Ⅵ)暴露下水稻秸秆、蚯蚓和寡氧单胞菌协同处理显著增加了土壤总Cr和Cr(Ⅵ)的去除率,降低了生物有效态Cr的占比并改善了Cr在团聚体中的分布.
农业废弃物的高值化利用有助于缓解资源约束、减少环境污染.秸秆纤维素是细胞壁中最主要的物质,与木质素和半纤维素稳定嵌套,难以分离.因此,秸秆有效组分分离提取是实现其高值化利用的基础和关键.本文对秸秆中纤维微观结构、形成机制及理化性质进行深入阐述,介绍了提取纤维素的多种技术,并对纤维素分离原理与优缺点进行了凝练.针对现有技术壁垒及局限性,展望秸秆纤维分离、提取及纯化等的研究领域和发展方向,以期为探索出高效绿色环保的工艺技术,实现秸秆纤维素的高值化利用奠定基础.
