淋洗后生活垃圾堆肥建植高羊茅草坪生理生态响应

以不同淋洗方式处理后的生活垃圾堆肥为基质进行草坪植物培植,研究了高羊茅的生理生态响应。结果表明,淋洗处理堆肥中高羊茅的发芽率及株高等生长指标均优于未淋洗的原堆肥对照组,其中水肥淋洗比例为1∶1的处理中,高羊茅的最大发芽率比对照提高89.6%。通过对超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）3种保护酶的活性及脯氨酸和丙二醛（MDA）含量等指标的测定可以看出,经淋洗处理后的堆肥基质对草坪植物的胁迫程度均小于原堆肥,更有利于草坪植物的正常生长。综合高羊茅生长指标及生理指标来考虑,堆肥处理的最佳淋洗比例为水∶堆肥的质量比为2∶1。     

Indicators for nitrogen status and leaching in subtropical forest ecosystems,South China

The deposition of nitrogen (N) is high in subtropical forest in South China and it is expected to increase further in the coming decades. To assess effects of increasing deposition on N cycling, we investigated the current N status of two selected 40–45-year-old masson pine-dominated Chinese subtropical forest stands at Tieshanping (TSP, near Chongqing City) and Caijiatang (CJT in Shaoshan, Hunan province), and explored the applicability of several indicators for N status and leaching, suggested for temperate and boreal forest ecosystems. Current atmospheric N deposition to the systems is from 25 to 49 kg ha⁻¹ year⁻¹. The concentration of total N in the upper 15 cm of the soil is from as low as 0.05% in the B₂ horizon to as high as 0.53% in the O/A horizon. The concentration of organic carbon (C) varies from 0.74 (B₂) to 9.54% (O/A). Pools of N in the upper 15 cm of the soils range from 1460 to 2290 kg N ha⁻¹, where 25–55% of the N pool is in the O/A horizon (upper 3 cm of the soil). Due to a lack of a well-developed continuous O horizon (forest floor), the C/N ratio of this layer cannot be used as an indicator for the N status, as is commonly done in temperate and boreal forests. The net N mineralization rate (mg N g⁻¹ C year⁻¹) in individual horizons correlates significantly with the C/N ratio, which is from as high as 18.2 in the O/A horizon to as low as 11.2 in the B₂ horizon. The N₂O emission flux from soil is significantly correlated with the KCl extractable NH₄⁺–N in the O/A horizon and with the net nitrification in the upper 15 cm of the soil. However, the spatial and temporal variation of the N₂O emission rate is high and rates are small and often difficult to detect in the field. The soil flux density of mineral N, defined as the sum of the throughfall N input rate and the rate of in situ net N mineralization in the upper 15 cm of the soil, i.e., the combination of deposition input and the N status of the system, explains the NO₃⁻ leaching potential at 30 cm soil depth best. The seasonality of stream water N concentration at TSP and CJT is climatic and hydrologically controlled, with highest values commonly occurring in the wet growing season and lowest in the dry dormant season. This is different from temperate forest ecosystems, where N saturation is indicated by elevated NO₃⁻ leaching in stream water during summer.     

庐山不同海拔日本柳杉年轮宽度对气候因子的响应

以庐山自然保护区3个不同海拔样地采集的138根日本柳杉样芯为研究材料,利用树木年轮学方法分析其径向生长与季节和月气候因子的响应关系。结果表明:低海拔处日本柳杉径向生长对气候因子的响应相比于中、高海拔更敏感;中、低海拔径向生长与春季相对湿度呈显著正相关(P<0.05),低海拔径向生长与春季日照时数、夏季均温呈显著负相关(P<0.05),而中海拔径向生长与夏、秋季均温呈显著负相关(P<0.05);高海拔径向生长与各个季节气候因子表现出一定的相关性,但相关性不显著; 3个海拔径向生长均与当年1月均温呈显著正相关(P<0.05),中、低海拔径向生长与上年7月及当年7月均温呈显著负相关(P<0.05),高温会抑制树木的生长,低海拔径向生长与当年4月空气相对湿度、降水量呈显著正相关(P<0.05),与当年4月日照时数呈显著负相关(P<0.05),随海拔的升高相关性降低;庐山日本柳杉径向生长与主要气候要素之间的相关性呈现出明显的季节性,日本柳杉径向生长主要受上年7及7月均温和4月空气相对湿度的影响,海拔是影响日本柳杉径向生长对气候因子响应的重要因素,最终建立...     

Assessment of the Environmental Sustainability of a Treatment Aimed at Soil Reuse in a Brownfield Regeneration Context

A combined stabilization/solidification (S/S) and granulation treatment was shown to be effective, at lab scale, to produce secondary aggregates from a Brownfield soil slightly contaminated by metals. This treatment, as opposed to the frequently adopted “dig and dump” option, allows to combine soil management with site regeneration, minimizing landfill disposal. But is this treatment actually more environmentally sustainable than excavated soil management by dig and dump? To answer this question, we analyzed and compared by life cycle assessment the environmental impacts resulting from the application of the above‐mentioned treatment versus dig and dump on the basis of the results of lab tests performed on a Brownfield soil sample, including leaching test results. The impacts related to the production of all the reagents used in the on‐site treatment, as well as the avoided impacts due to the replacement of raw aggregates with recycled ones, were included. Results showed that the proposed S/S‐granulation process may allow a drastic decrease of the impacts related to land use and resource depletion in comparison to dig and dump, with beneficial effects also with regard to toxicity‐related impact categories. Conversely, the proposed treatment yielded higher impacts, in terms of acidification, water resource depletion, and, in particular, climate change, almost entirely related to the manufacturing of the cement employed for stabilization. However, an average 40% reduction of overall impacts was noted when fly ash cement was assumed to be used as binder instead of Portland cement.     

Effects of acid irrigation and liming on nitrate reduction and nitrate content of Picea abies (L.) Karst. and Oxalis acetosella L.

Nitrate reductase activities (NRA) and nitrate concentration per unit biomass in Picea abies (L.) Karst. roots from four different soil horizons and in leaves and roots of the frequent field-layer species Oxalis acetosella L. were measured on six different irrigation and liming treatments within the Höglwald project, S-Bavaria, Germany. Liming increased and acid irrigation reduced soil nitrate availability when compared to control plots. Nitrate assimilation capacities of the respective plant compartments per unit of soil volume or ground area were calculated from the NRA per unit of biomass and from the biomass distribution on the various treatments.Mean NRA per unit of biomass in Picea abies roots ranged between 0.23 and 0.09 mol NO ₂ ^- g_-1 d.w. h_-1 without significant effects of soil horizon or treatment. Limed and non-limed treatments showed for Picea different root distributions within the soil profile, but root biomass per unit of ground area (295 to 220 g d.w. m^-2) was not affected by the various treatments. Thus, nitrate assimilation capacity of Picea roots per unit of ground area ranged between 19.5 and 11.4 mol NO ₂ ^- m^-2 h_-1 without major treatment effects.In laminae of Oxalis acetosella mean NRA per unit of biomass ranged between 2.91 and 0.27 mol NO ₂ ^- g_-1 d.w. h_-1 and, in contrast to Picea abies, treatment effects were found with NRA on limed plots increased and on acid irrigated plots reduced when compared to control plots. Mean leaf biomass of Oxalis per unit of ground area ranged between 9.57 and 0.66 g d.w. m^-2 and responded in a similar manner to the various treatments. Thus, for the Oxalis leaf NRA per unit of ground area (27.85 to 0.18 mol NO₂ m^-2 h_-1) a cumulative response to the variations in nitrate availability was found.The different responses of Picea abies and Oxalis acetosella to changes in soil nitrate availability are discussed with respect to their suitability to prevent soil nitrate leaching.     

How inhibiting nitrification affects nitrogen cycle and reduces environmental impacts of anthropogenic nitrogen input

Anthropogenic activities, and in particular the use of synthetic nitrogen (N) fertilizer, have doubled global annual reactive N inputs in the past 50–100 years, causing deleterious effects on the environment through increased N leaching and nitrous oxide (N₂O) and ammonia (NH₃) emissions. Leaching and gaseous losses of N are greatly controlled by the net rate of microbial nitrification. Extensive experiments have been conducted to develop ways to inhibit this process through use of nitrification inhibitors (NI) in combination with fertilizers. Yet, no study has comprehensively assessed how inhibiting nitrification affects both hydrologic and gaseous losses of N and plant nitrogen use efficiency. We synthesized the results of 62 NI field studies and evaluated how NI application altered N cycle and ecosystem services in N‐enriched systems. Our results showed that inhibiting nitrification by NI application increased NH₃ emission (mean: 20%, 95% confidential interval: 33–67%), but reduced dissolved inorganic N leaching (?48%, ?56% to ?38%), N₂O emission (?44%, ?48% to ?39%) and NO emission (?24%, ?38% to ?8%). This amounted to a net reduction of 16.5% in the total N release to the environment. Inhibiting nitrification also increased plant N recovery (58%, 34–93%) and productivity of grain (9%, 6–13%), straw (15%, 12–18%), vegetable (5%, 0–10%) and pasture hay (14%, 8–20%). The cost and benefit analysis showed that the economic benefit of reducing N's environmental impacts offsets the cost of NI application. Applying NI along with N fertilizer could bring additional revenues of $163 ha^?1 yr^?1 for a maize farm, equivalent to 8.95% increase in revenues. Our findings showed that NIs could create a win‐win scenario that reduces the negative impact of N leaching and greenhouse gas production, while increases the agricultural output. However, NI's potential negative impacts, such as increase in NH₃ emission and the risk of NI contamination, should be fully considered before large‐scale application.     

Reappraisal of drying and wetting effects on C and N mineralization and fluxes in soils

In the next decades, many soils will be subjected to increased drying/wetting cycles or modified water availability considering predicted global changes in precipitation and evapotranspiration. These changes may affect the turnover of C and N in soils, but the direction of changes is still unclear. The aim of the review is the evaluation of involved mechanisms, the intensity, duration and frequency of drying and wetting for the mineralization and fluxes of C and N in terrestrial soils. Controversial study results require a reappraisal of the present understanding that wetting of dry soils induces significant losses of soil C and N. The generally observed pulse in net C and N mineralization following wetting of dry soil (hereafter wetting pulse) is short‐lived and often exceeds the mineralization rate of a respective moist control. Accumulated microbial and plant necromass, lysis of live microbial cells, release of compatible solutes and exposure of previously protected organic matter may explain the additional mineralization during wetting of soils. Frequent drying and wetting diminishes the wetting pulse due to limitation of the accessible organic matter pool. Despite wetting pulses, cumulative C and N mineralization (defined here as total net mineralization during drying and wetting) are mostly smaller compared with soil with optimum moisture, indicating that wetting pulses cannot compensate for small mineralization rates during drought periods. Cumulative mineralization is linked to the intensity and duration of drying, the amount and distribution of precipitation, temperature, hydrophobicity and the accessible pool of organic substrates. Wetting pulses may have a significant impact on C and N mineralization or flux rates in arid and semiarid regions but have less impact in humid and subhumid regions on annual time scales. Organic matter stocks are progressively preserved with increasing duration and intensity of drought periods; however, fires enhance the risk of organic matter losses under dry conditions. Hydrophobicity of organic surfaces is an important mechanism that reduces C and N mineralization in topsoils after precipitation. Hence, mineralization in forest soils with hydrophobic organic horizons is presumably stronger limited than in grassland or farmland soils. Even in humid regions, suboptimal water potentials often restrict microbial activity in topsoils during growing seasons. Increasing summer droughts will likely reduce the mineralization and fluxes of C and N whereas increasing summer precipitation could enhance the losses of C and N from soils.     

Compositional changes during landfarming of weathered michigan crude oil‐contaminated soii

Laboratory landfarming experiments were conducted to study the bioremediation potential of weathered Michigan crude oil‐contaminated soils. It was found that landfarming was successful in removing up to 90% of the total petroleum hydrocarbons (TPH) in the soil within 22 weeks of treatment. Boiling point analyses of untreated and treated soils indicate a significant removal of TPH compounds independent of molecular weight or carbon number. Up to 85% of heavy petroleum hydrocarbons with carbon numbers above 44 were biode‐graded. In addition, approximately 93% of saturated and 79% of aromatic compounds of the TPH were biodegraded during the 22 week treatment period. The use of polyethylene sheeting as a landfarm cover does not appear to adversely affect biodegradation kinetics under laboratory conditions. Finally, equilibrium leachate concentrations for BTEX and regulated (in Michigan) polynuclear aromatics (PNAs) were below the respective detection limits for each compound. It can be concluded that landfarming of these weathered soils will be highly successful in removing petroleum hydrocarbons while not adversely impacting either ground‐water or surface water quality.     

Modelling and measuring the effect of nitrogen catch crops on the nitrogen supply for succeeding crops

Nitrogen catch crops are grown to absorb nitrogen from the rooting zone during autumn and winter. The uptake of N (N_upt) from the soil inorganic N pool (N_min) to a pool of catch crop nitrogen, will protect the nitrogen against leaching. After incorporation, a fraction (m) of the catch crop nitrogen is mineralized and becomes available again. However, not all available nitrogen present in the soil in the autumn is lost by leaching during winter. A fraction (r) of the nitrogen absorbed by the catch crop would, without a catch crop, have been retained within the rooting zone. The first year nitrogen beneficial effect (N_eff) of a catch crop may then be expressed b N _eff = m*N _upt - r* N _upt The soil-plant simulation model DAISY was evaluated for its ability to simulate the effects of catch crops on spring N_min and N_eff. Based on incubation studies, parameter values were assigned to a number of catch crop materials, and these parameter values were then used to simulate spring Nmin. The model was able to predict much of the vairiation in the measured spring Nmin (r² = 0.48***) and there was good agreement between the measured and the simulated effect of winter precipitation on spring N_min and Neff.Scenarios including variable soil and climate conditions, and variable root depth of the succeeding crop were simulated. It is illustrated that the effect of catch crops on nitrogen availability for the succeeding crop depends strongly on the rooting depth of the succeeding crop. If the succeeding crop is deep rooted and the leaching intensity is low, there is a high risk that a catch crop will have a negative effect on nitrogen availability. The simulations showed that the strategy for the growing of catch crops should be adapted to the actual situation, especially to the expected leaching intensity and to the rooting depth of the succeeding crop.     

Isolation and study of two strains ofLeptospirillum-like bacteria from a natural mixed population cultured on a cobaltiferous pyrite substrate

Two strains ofLeptospirillum-like bacteria, L6 and L8, have been isolated from a mixed inoculum, also containingThiobacillus ferrooxidans andT. thiooxidans, cultured for one year with a colbaltiferous pyrite as energy substrate in a 100 I continuous bioleaching laboratory unit. Several physiological properties of the strains are described. The vibrio-shaped microorganisms grew at pH values lower than 1.3. Their growth rate was maximum between 2.5 and 8.0 g l¹ ferrous iron. The optimal growth temperature was 37.5° C. Ferric iron had a stimulative effect on bacterial development up to 8 g l^–1, and growth was as rapid at 14 g l^–1 ferric iron as at 8 g l^–1. The negative influence of cobalt on the final cell concentration was observed at 0.5 g l^–1, but the growth rate was not affected up to 2 g l^–1. The G + C content of strains L8 is 55.6 mol%.