Individual-based modelling of carbon and nitrogen dynamics in soils: Parameterization and sensitivity analysis of microbial components

The fate of soil carbon and nitrogen compounds in soils in response to climate change is currently the object of significant research. In particular, there is much interest in the development of a new generation of micro-scale models of soil ecosystems processes. Crucial to the elaboration of such models is the ability to describe the growth and metabolism of small numbers of individual microorganisms, distributed in a highly heterogeneous environment. In this context, the key objective of the research described in this article was to further develop an individual-based soil organic matter model, INDISIM-SOM, first proposed a few years ago, and to assess its performance with a broader experimental data set than previously considered. INDISIM-SOM models the dynamics and evolution of carbon and nitrogen associated with organic matter in soils. The model involves a number of state variables and parameters related to soil organic matter and microbial activity, including growth and decay of microbial biomass, temporal evolutions of easily hydrolysable N, mineral N in ammonium and nitrate, CO₂ and O₂. The present article concentrates on the biotic components of the model. Simulation results demonstrate that the model can be calibrated to provide good fit to experimental data from laboratory incubation experiments performed on three different types of Mediterranean soils. In addition, analysis of the sensitivity toward its biotic parameters shows that the model is far more sensitive to some parameters, i.e., the microbial maintenance energy and the probability of random microbial death, than to others. These results suggest that, in the future, research should focus on securing better measurements of these parameters, on environmental determinants of the switch from active to dormant states, and on the causes of random cell death in soil ecosystems.     

Moist Olive Husks Addition to a Silty Clay Soil: Influence on Microbial and Biochemical Parameters

To investigate the effects of moist olive husks (MOH-residues) on soil respiration, microbial biomass, and enzymatic (o-diphenoloxidase, β-glucosidase, dehydrogenase and alkaline phosphatase) activities, a silty clay soil was incubated with 0 (control), 8 × 10³ (D), 16 × 10³ (2D) and 80 × 10³ (10D) kg ha^?1 of MOH-residues on a dry weight basis. Soil respiration and microbial biomass data indicated that the addition of MOH-residues strongly increased microbial activity proportionally to the amounts added. Data of qCO₂ suggested that the respiration to biomass ratio of the microbial population was strongly modified by MOH-residues additions during the first 90 days of incubation. The qCO₂ data suggested a low efficiency in energy yields from C oxidation during the first 2 months of soil incubation. qFDA seemed to be relatively unaffected for treatments D and 2D as compared to the control, but was significantly lowered by the application of 10D, showing the lowest hydrolytic activity of microbial biomass in this treatment up to 360 days of incubation.

o-Diphenoloxidase activity was delayed, and this delay was extended with the addition of larger quantities of MOH-residues. Alkaline phosphatase, β-glucosidase and dehydrogenase activities were in line with the findings on microbial biomass changes and activities. The biological and biochemical data suggest that the addition of a large quantity of MOH-residues (80 × 10³ kg ha^?1) strongly modifies the soil characteristics affecting the r- and K-strategist populations, and that these changes last for at least the 360 days of incubation. The data also suggest that application rates exceeding 16 × 10³ kg ha^?1 are not recommended until the agro-chemical and -physical functions of the soil are further studied.     

Radical Scavengers Suppress Low Frequency EMF Enhanced Proliferation in Cultured Cells and Stress Effects in Higher Plants

Summary In previous publications, we reported that sinusoidal varying magnetic fields (SVMF) modify the activity and dynamics of the malignancy marker adenosine deaminase, and enhance the proliferation of chick embryo fibroblasts (CEF). While the SVMF examined by us (50, 60 & 100 Hz / 0.06–0.7 mT) were all below kT, they may have the potential of altering chemical processes in which excited radicals are involved. We tested this hypothesis in two experimental systems: CEF in culture and Spirodela oligorrhiza (Lemnaceae) (a small aquatic plant, commonly known as Duckweed). CEF were exposed to SVMF of 100 Hz/0.7 mT for 24 h. The addition of the exogenous radical scavengers catalase, superoxide dismutase or vitamin E to the cells during exposure significantly suppressed enhancement of cell proliferation caused by the field (by 79, 67 and 82%, respectively, as evaluated by the MTT colorimetric assay). ¹⁵N NMR analysis of Duckweed plants fed by ¹⁵N-labeled ammonium chloride and exposed to SVMF at 60 and 100 Hz/0.7 mT for 24 h, revealed augmented alanine production. Alanine did not accumulate in the absence of SVMF. The addition of vitamin C, a radical scavenger, reduced alanine production by 82%. Exposure to SVMF resulted in specific metabolic stress effects in Duckweed plants and enhanced proliferation of CEF. In both cases, it is suggested that free radicals are involved.     

A Retrospective Isotopic Study of Spruce Decline in the Vosges Mountains (France)

The objective of this study was to assess the time variation of mineral and water stress levels across the life of a declining, Mg-deficient, spruce stand, in order to clarify the factors that caused the decline. Since 1985, strong soil acidification linked to a large leaching of nitrate and base cations was measured at the study site. In 1994, 5 trees were felled and tree rings were measured and analysed for Ca, Mg, K, Sr, ¹³C¹²C and ⁸⁷Sr/⁸⁶Sr isotopic ratios. Strontium pools and fluxes as well as root Sr isotope ratio in relation to depth were also measured. Wood chemical concentrations and isotope ratios were strongly related to the dominance status of each tree. On average during the study period, the ⁸⁷Sr/⁸⁶Sr ratio of spruce wood decreased. Using a mechanistic model computing long term variations of ⁸⁷Sr/⁸⁶Sr ratio in trees and soils, we reproduced the observed trend by simulating soil acidification – increasing Sr drainage from the whole profile, and particularly from the organic horizon –, and root uptake becoming more superficial with time. Between 1952 and 1976, tree ring ¹³C decreased strongly and continuously, which, in addition to other factors, might be related to an increase in water stress. Thus, a decrease in rooting depth, possibly related to soil acidification, appeared as a possible cause for the long term increase in water stress. The extreme drought event of 1976 appears to have revealed and triggered the decline.     

自反应性化学物质的热危险性评价方法

笔者进行的研究工作 ,给出了利用C80微量量热仪所测得的自反应性化学物质的热流速曲线 ,从而求解该物质的化学反应动力学参数 ,以及在Semenov模型下求解其自加速分解温度SADT(Self AcceleratingDecompositionTemperature)的方法 ,并将一些有机过氧化物、氧化剂和可燃剂的混合物的自加速分解温度的推算结果与实测值进行了比较。实验证明 ,该推算方法结论准确 ,是一种安全、简便、实用的反应性化学物质热危险性的评价方法     

87年生杉木生长分析

本文分析了87年生杉木的生长状况。     

Taming B.C. Hydro: Site C and the implementation of the B.C. Utilities Commission Act

Public policy making in resources management is greatly influenced by the institutional arrangements that arise out of the legal powers, administrative structures, and financial provisions of the decision system. In British Columbia, the institutional arrangements for energy planning in the province have been greatly altered by the passage of the Utilities Commission Act in 1980. This act redefines the policy implementation process for energy in British Columbia and provides for the regulation of the province's power utility, B.C. Hydro. This is the first time that the hitherto autonomous utility has been subject to regulation and the Utilities Commission Act represents a major reform in the institutional arrangements for energy planning in the province. The article evaluates the effectiveness of the 1980 B.C. Utilities Commission Act and assesses the impact of the legislation upon the institutional arrangements for energy planning in the province. Data for the article were derived from written sources and a series of personal interviews with key participants involved with energy planning in B.C.It is shown that the act represented a major departure in the management of energy resources in B.C. Moreover the implementation of the act's provisions, particularly in regard to B.C. Hydro, had a dramatic impact on the development of new energy projects in the province. It is suggested that while the political and economic climate during the period also favored restraint, the major influence on taming the utility was passage of the Utilities Commission Act. The article concludes by exploring the implications of policy changes that have occurred as a consequence of the act's impact on B.C. Hydro.     

Assessment of risks posed by chemical industries—application of a new computer automated tool -III

The paper describes the application of a new computer automated tool, developed by us, in the risk analysis of a typical chemical industry engaged in the manufacture of linear alkyl benzene. Using the tool—a comprehensive software package -III (MAXimum CREDible accident analysis)—nine different scenarios, one for each storage unit, have been studied. It is observed that the accident scenario for chlorine (instantaneous release followed by dispersion) leads to the largest area-under-lethal-impact, while the accident scenario for propylene (CVCE followed by fireball) forecasts the most intense damage per unit area. The accidents involving propylene, benzene, and fuel oil have a high possibility of causing domino/secondary accidents as their destructive impacts (shock waves, heat load) would envelope other storage and process units.Besides demonstrating the utilizability of -III, this study also focuses attention on the need to bestow greater effort towards risk assessment/crisis management. The authors hope that the study will highlight the severity of the risk posed by the industry and thus generate safety consciousness among plant managers. The study may also help in developing accident-prevention strategies and the installation of damage control devices.     

桉树遗态Fe_2O_3/Fe_3O_4/C复合材料对某尾矿库废水中砷的吸附研究

以制备的桉树遗态Fe_2O_3/Fe_3O_4/C复合材料(PBGC-Fe/C)为吸附剂,对某尾矿库废水中砷等重金属进行了吸附实验。研究了温度、pH、废水化学组成、吸附剂投加量及粒径等对吸附的影响。结果表明,吸附剂投加量越大、粒径越小,温度为35℃,p H为3左右吸附效果最好。但实际废水组分复杂,存在竞争吸附及化学沉淀等使砷的总去除率随p H的增大而增大。综合考虑,吸附砷的最佳条件组合为废水p H=5,PBGC-Fe/C投加量0.06 g/m L,粒径150μm。此时废水中总砷质量浓度为0.487 mg/L,可达标排放。     

水解反硝化+A/O工艺处理低碳氮比城镇废水试验研究

采用水解反硝化强化脱氮工艺,将水解酸化过程与反硝化脱氮过程相结合,研究此工艺对城镇低碳氮比废水的处理效果。实验表明,系统对COD、NH_4~+-N、TN的去除效果较为稳定,去除率分别为87.95%、99.42%、51.84%,出水COD及NH_4~+-N均优于国家一级A排放标准。当硝化液回流比为100%时,为最优工况,在进水C/N比为1时,系统对TN去除率为55.07%,去除量达45.43 mg/L;进水C/N比为0.82时,系统对TN去除率为50.45%,去除量达37.27mg/L。在C/N<1的条件下,系统仍然表现出较高的脱氮性能。对比水解池与后段A/O缺氧池的脱氮效果,水解池在反硝化脱氮能力及碳源利用率方面均优于缺氧段。