剩余污泥臭氧化减量处置方法研究进展

综合臭氧污泥减量化近年来的发展和研究,对其技术原理和工艺应用进行分析,提出了其现存问题,并讨论了未来的技术发展万向.     

丛枝菌根真菌调控土壤氧化亚氮排放的机制

氮素是陆地生态系统初级生产力的主要限制因子,自Haber-Bosch反应以来,氮肥的生产和施用极大地提高了粮食产量.然而过量施用氮肥导致氮肥利用率低,并造成了严重的环境污染,包括氮沉降、硝态氮淋洗以及N2O排放等.微生物直接参与土壤氮素循环,固氮微生物、氨氧化和反硝化微生物分别在土壤固氮、铵态氮转化和硝态氮转化过程中起...     

Effects of transition season management on soil N dynamics and system N balances in rice–wheat rotations of Nepal

In the low-input rice–wheat production systems of Nepal, the N nutrition of both crops is largely based on the supply from soil pools. Declining yield trends call for management interventions aiming at the avoidance of native soil N losses. A field study was conducted at two sites in the lowland and the upper mid-hills of Nepal with contrasting temperature regimes and durations of the dry-to-wet season transition period between the harvest of wheat and the transplanting of lowland rice. Technical options included the return of the straw of the preceding wheat crop, the cultivation of short-cycled crops during the transition season, and combinations of both. Dynamics of soil N_min, nitrate leaching, nitrous oxide emissions, and crop N uptake were studied throughout the year between 2004 and 2005 and partial N balances of the cropping systems were established. In the traditional system (bare fallow between wheat and rice) a large accumulation of soil nitrate N and its subsequent disappearance upon soil saturation occurred during the transition season. This nitrate loss was associated with nitrate leaching (6.3 and 12.8 kg ha⁻¹ at the low and high altitude sites, respectively) and peaks of nitrous oxide emissions (120 and 480 mg m⁻² h⁻¹ at the low and high altitude sites, respectively). Incorporation of wheat straw at 3 Mg ha⁻¹ and/or cultivation of a nitrate catch crop during the transition season significantly reduced the build up of soil nitrate and subsequent N losses at the low altitude site. At the high altitude site, cumulative grain yields increased from 2.35 Mg ha⁻¹ with bare fallow during the transition season to 3.44 Mg ha⁻¹ when wheat straw was incorporated. At the low altitude site, the cumulative yield significantly increased from 2.85 Mg ha⁻¹ (bare fallow) to between 3.63 and 6.63 Mg ha⁻¹, depending on the transition season option applied. Irrespective of the site and the land use option applied during the transition season, systems N balances remained largely negative, ranging from −37 to −84 kg N ha⁻¹. We conclude that despite reduced N losses and increased grain yields the proposed options need to be complemented with additional N inputs to sustain long-term productivity.     

秸秆生物质炭对稻田土壤剖面N2O和N2浓度的影响*

氧化亚氮（N2O）和氮气（N2）是淹水稻田土壤剖面反硝化过程的重要气态产物,可通过土水界面向大气排放,也可随水向下淋溶。秸秆生物质炭施入稻田后会改变土壤理化及微生物学性质,影响反硝化过程及N2O和N2产排。本研究依托2010年夏建立的连续秸秆生物质炭还田的稻麦轮作农田试验,通过埋设淋溶管收集土壤剖面溶液,采用气相色谱和膜进样质谱分别定量溶液中N2O和exN2（反硝化产生N2量）,观测了2018和2019年水稻季不同秸秆生物质炭施用量（CK：每季0 t·hm-2;1BC：每季2.25 t·hm-2;5BC：每季11.3 t·hm-2;10BC：每季22.5 t·hm-2）下0~1 m土壤剖面溶液中N2O和exN2浓度的时空变化,评估了长期施用秸秆生物质炭对稻田土壤剖面反硝化作用及其主要气态氮产物exN2随水流失的影响。结果表明,两个稻季CK处理N2O浓度以60 cm处较高,exN2浓度则随土壤深度增加呈降低趋势。秸秆生物质炭处理能降低剖面N2O和exN2浓度,以10BC处理最为明显。其中,N2O浓度降低以60 cm处较大,exN2浓度降低随土壤深度增加而加大。施用秸秆生物质炭对土壤剖面溶液无机氮（NO3-+NH4+）含量无明显影响,但5BC和10BC处理增加了可溶性有机碳（DOC）和溶解氧（DO）浓度以及氧化还原电位（Eh）。CK处理下土壤剖面溶液N2O和exN2浓度变化与DOC、硝态氮（NO3-）及DO有关;秸秆生物质炭处理下则主要受DO和Eh控制。exN2淋溶量（按1 m深度计算）CK处理下为2.3 ~5.5 kg·hm-2,相当于无机氮和有机氮（DON）淋溶量的32%~34%,5BC和10BC处理则降低为1.7 ~3.7 kg·hm-2和1.1~1.9 kg·hm-2,上述结果表明,反硝化产生N2随水淋溶量不容忽视,秸秆生物质炭还田可改善淹水稻田土壤剖面的通气状况,增加DO,提高Eh,进而有效减少深层反硝化及其主要气态产物exN2随水流失的风险。     

亚热带土壤亚铁与厌氧反硝化

本文就亚热带土壤亚铁参与反硝化的可能性进行了探讨。研究结果表明:厌氧还原条件下加入KNO3的处理中,Fe2+浓度随培养时间延长而下降,且Fe2+浓度的降低和NO3–-N浓度的降低呈显著正相关。预培养结束后的亚铁浓度(In-Fe2+)和厌氧培养期间Fe2+浓度降低速率与反硝化势表征指标k、b、v7,以及与无定形铁氧化物(活性铁)含量的显著正相关性初步证明,活性铁通过不同价态铁离子(Fe2+和Fe3+)之间的转化,参与了反硝化的电子传递过程。当有机碳等电子供体受限时,Fe2+可作为电子供体参与反硝化还原NO3–-N。这一结果表明,NO3–-N作为电子受体参与厌氧条件下Fe2+氧化成Fe3+的反应可能在铁氧化物含量丰富的亚热带土壤中普遍存在。     

地下水硝酸盐去除中反硝化微生物的研究进展

地下水硝酸盐污染已经成为一个全球问题,由于饮用高硝酸盐含量的地下水会增加高铁血红蛋白症和癌症风险,地下水硝酸盐污染受到越来越多的关注。反硝化脱氮是地下水硝酸盐脱氮的主要途径之一。本文就参与地下水硝酸盐去除的反硝化微生物种类、反硝化机理、碳源类型以及地下水污染中微生物作用的国内外研究现状进行了较全面系统的评述。在此基础上,提出了该类研究中存在的不足,包括实验室研究较多但野外研究较少,野外原位应用中对特定微生物特性方面研究缺乏,碳源利用率低和硝酸盐去除速度慢,去除过程中有效微生物的代谢途径仍不清楚等问题。针对这些问题,本文认为以后的研究应该进一步开发野外原位应用中反硝化微生物资源,并借助先进的分子方法和功能基因鉴定此类特殊微生物的种类、功能及其生态学行为,选择最佳碳源,完整深入地了解地下水硝酸盐去除中微生物的代谢过程,识别反硝化过程中氮的来源与去向,为寻找提高处理效率的方法提供理论依据,真正将理论和实践结合起来。     

Reciprocal transfer effects on denitrifying community composition and activity at forest and meadow sites in the Cascade Mountains of Oregon

In order to examine the effects of disturbance, vegetation type, and microclimate on denitrification and denitrifier community composition, experimental plots were established at the H. J. Andrews Experimental Forest in the Cascade Mountains of Oregon. Soil cores were reciprocally transplanted between meadow and forest and samples were collected after 1 and 2 years. Denitrifying enzyme activity (DEA) was measured using the acetylene block assay and terminal restriction length polymorphism profiles were generated with nosZ primers that target the gene coding for nitrous oxide reductase. Nitrate concentrations, C mineralization, and water content were measured to gain additional insights into soil properties controlling DEA. Meadow soils were significantly higher in DEA than forest soils, and the highest DEA levels were observed in cores transferred from the meadow into the forest. Nitrate concentrations were also different between forest and meadow soils, but did not correlate to DEA. DEA was higher in open versus closed cores, suggesting an association between denitrification and the rhizosphere. Denitrifier communities of undisturbed forest and meadow soils shifted through a 4-year period but remained distinct from each other. Similarly, denitrifier communities clustered by vegetation type of origin regardless of manipulation, suggesting that the overall denitrifier communities are well buffered against environmental changes.     

Tillage-induced environmental conditions in soil and substrate limitation determine biogenic gas production

Tillage changes soil environmental conditions and controls the distribution of residues in the soil, both actions that affect the production and emission of soil biogenic gases (CO₂, N₂O, and CH₄). The objective of this study was to determine how tillage-induced environmental conditions and substrate quality affect the mineralization rate of easily metabolizable compounds and the subsequent production of these gases. Carbon compounds, with and without nitrogen, were applied to soil cropped to maize under tilled and no-till systems. Following substrate application in the spring and summer, biogenic gases were measured periodically at the soil surface (flux) and within the profile (concentration) at 10-, 20-, and 30-cm depths (i.e., within, at the bottom of, and below the plough layer). Strong CO₂ and N₂O responses to sucrose and glycine in both the field and the laboratory indicate that the soil was C- and N-limited. Surface fluxes of CO₂ and N₂O were greater in soils amended with glycine than with sucrose and were greater in tilled than no-till soils. Transient emission of CH₄ following the addition of glycine was observed and could be attributed to inhibition of N mineralization and nitrification processes on CH₄ oxidation. Laboratory and field measurements indicated that the larger substrate-induced CO₂ emission from the tilled soils could not be attributed to differences in the total biomass or the basal respiratory activity of the soils. Thus, there appears to be no underlying difference in the functional capacity of the microbial communities under different tillage regimes. Comparison of gas profiles indicates relative accumulation of CO₂ at depth in soils under no-till, as well as greater decline in profile CO₂ content with time in the tilled compared to the no-till soil. These results support the conclusion that greater CO₂ efflux from the tilled soils resulted from more rapid gas diffusion through the profile. Hence, the observed differences in gas fluxes between tilled and no-till soils can be attributed to differences in physical environment.     

Irrigation practices may affect denitrification more than nitrogen mineralization in warm climatic conditions

Predicting the impact of irrigation practices on soil N mineralization and N balance is an important issue to optimize N fertilization and reduce the N losses towards the environment. The effect of summer irrigation on N dynamics was investigated in two arable fields in Southern France. Net N mineralization was assessed by combining frequent measurements of water and mineral N contents in soil and the use of a calculation model (LIXIM). It was first calculated assuming that denitrification was negligible. This hypothesis led to inconsistent results, apparent net N mineralized being smaller under irrigated than non-irrigated conditions and net mineralization kinetics being erratic. The occurrence of denitrification was confirmed by the use of ¹⁵NO₃ tracing in an experiment carried out in summer, including three irrigated treatments. The average ¹⁵N recovery varied from 45% to 85% and was smallest in the most frequently irrigated treatment. Over the 8-week experiment, the N losses varied from 30 to 38 kg ha⁻¹ in the irrigated treatments. They were satisfactorily simulated by a simple denitrification model (NEMIS). Combining the LIXIM model and the simulated or calculated denitrification allowed to predict satisfactorily the evolution of soil mineral N accounting for the effects of temperature and moisture. The net N mineralized for 8 weeks varied from 34 kg N ha⁻¹ in the un-irrigated to 46 kg N ha⁻¹ in the irrigated treatments. The drying–rewetting cycles did not induce a flush of N mineralization. Our results suggest that denitrification has to be accounted for in irrigated systems, particularly in warm conditions and when the topsoil contains high nitrate contents.     

Impact of atmospheric CO2 and plant life forms on soil microbial activities

From the global change perspective, increase of atmospheric CO₂ and land cover transformation are among the major impacts caused by human activities. In this study, we are addressing the combined issues of the effect of CO₂ concentration increase and plant type on soil microbial activities by asking how annual and perennial plant groups affect soil microbial processes under elevated CO₂. The experimental design used a mix of species of different growth forms for both annuals and perennials. Our objective was: (1) to determine how two years of annual or perennial plant cover and CO₂ enrichment could affect Mediterranean soil microbial processes; (2) to test the resistance and the resilience of these soil functional processes after a natural perturbation. We determined the effects of 2 years atmospheric CO₂ enrichment on soil potential respiration (SIR), denitrification (DEA) and nitrification (NEA) activities. We could not find any significant effect of CO₂ increase on SIR, DEA and NEA. However, we found a strong effect of the plant cover type, i.e. annuals versus perennials, on the potential microbial activity related to N cycling. DEA and NEA were significantly higher in soil under annual plants while SIR was not significantly different. To determine whether these changes would survive a natural perturbation, we carried out a rain event experiment once the experimental treatments (i.e. different plant cover and atmospheric CO₂ concentration) were stopped. The soil potential respiration, as expressed by the SIR, was not affected and remained stable. DEA rates converged rapidly under annuals and perennials after the rain event. Under both annuals and perennials NEA increased significantly after the rain event but remained significantly higher in the soil with annual plants. The relative change of the soil microbial processes induced by annual and perennial plants was inversely related to the density and the diversity of the corresponding microbial functional groups.