The potential to increase soil carbon stocks through reduced tillage or organic material additions in England and Wales: A case study

Results from the UK were reviewed to quantify the impact on climate change mitigation of soil organic carbon (SOC) stocks as a result of (1) a change from conventional to less intensive tillage and (2) addition of organic materials including farm manures, digested biosolids, cereal straw, green manure and paper crumble. The average annual increase in SOC deriving from reduced tillage was 310 kg C ± 180 kg C ha⁻¹ yr⁻¹. Even this accumulation of C is unlikely to be achieved in the UK and northwest Europe because farmers practice rotational tillage. N₂O emissions may increase under reduced tillage, counteracting increases in SOC. Addition of biosolids increased SOC (in kg C ha⁻¹ yr⁻¹ t⁻¹ dry solids added) by on average 60 ± 20 (farm manures), 180 ± 24 (digested biosolids), 50 ± 15 (cereal straw), 60 ± 10 (green compost) and an estimated 60 (paper crumble). SOC accumulation declines in long-term experiments (>50 yr) with farm manure applications as a new equilibrium is approached. Biosolids are typically already applied to soil, so increases in SOC cannot be regarded as mitigation. Large increases in SOC were deduced for paper crumble (>6 t C ha⁻¹ yr⁻¹) but outweighed by N₂O emissions deriving from additional fertiliser. Compost offers genuine potential for mitigation because application replaces disposal to landfill; it also decreases N₂O emission.     

Interrelation of Cd‐lon concentrations and the growth and activities of microorganisms in two growth media†

Partitioning of native or anthropogenic heavy metals in solid and solution phases of soil is a result of network of several physico‐chemical reactions. The attainment of equilibrium between two phases is also regulated by biochemical processes. For practical purposes, the bioavailability of metal present in soil is predominantly regulated by the soil solution phase which is in dynamic equilibrium with the solid phase. The results of a model laboratory and greenhouse growth experiments have been used to investigate the effect of Cd‐ion concentrations (either in soil solution or in nutrient solution) on the growth and activities of microorganisms. The soil solution has been simulated by preparing a suspension of soil with 0.1 M NaNO₃ (1: 2.5) equilibrated for two hours. Important conclusions are as follows:

Increase in Cd‐ion concentration in soil solution or in nutrient solution induces corresponding adverse effect on the growth and activities of microorganisms. Thus, it seems that Cd‐ion concentration is a more sensitive indicator for assessing the effect of metal pollution upon the growth and activities of soil microorganisms in comparison to total Cd contents.

During active microbial growth phase, a large part of the organically bound Cd was released in the soil solution which is largely bioavailable. This process is termed as mobilisation. There was momentary increase of Cd‐ion concentration in soil solution which intoxicated the growing organisms. After this stage, the Cd ions from the solution phase were removed by the newly formed solid phase (nonviable biomass) and were transformed in non‐available form. This process is termed as immobilisation.

The consequences and importance of these results for practical agriculture and in deciding the limits or guidelines on the maximum tolerable metal load in soils are discussed.     

脉冲放电等离子体治理甲苯废气放大试验研究

应用脉冲放电等离子体技术,在线板式反应器内对低浓度甲苯废气的治理进行放大试验.采用闸流管开关脉冲电源,其最大输出功率1kW,最大脉冲电压峰值100kV. 试验规模4～16m³·h^-1. 试验考察了峰值电压、重复频率、进口浓度和处理气量对甲苯去除率的影响.结果表明:峰值电场强度在9～12kV·cm^-1范围内增加,甲苯去除率相应明显提高;当处理气量为4 m³·h^-1、脉冲电压峰值69kV、进口浓度1 180mg·m^-3、重复频率300pps时, 甲苯的去除率可达88%;反应器的能量利用率在16g·(kW·h)^-1左右;甲苯的降解产物主要是CO₂和H₂O,还有少量CO. 结合甲苯去除率与能量密度、甲苯进口浓度的关系,建立反应器动力学模型,获得甲苯的反应速率常数为0.00356 L·J^-1. 为进一步优化放大反应器设计及与电源匹配提供了基础数据.     

Growth, yield and elements content of wheat (Triticum aestivum) grown in composted municipal solid wastes amended soil

A commercial formulation of composted municipal solid wastes (MSW) was used for amending soil at 0, 50, 100, 150, 200 and 250 kg ha⁻¹ in which wheat had been grown (field experiments) and element residues of amended soil and plant parts were enumerated. MSW amendment caused a significant improvement in soil quality. Growth (shoot length, leaf number, leaf area, tiller number, plant dry weight and chlorophyll contents of leaves) and yield (length of panicle, number of panicles per plant and grain yield per plant) of wheat increased gradually up to the MSW-amendment level of 200 kg ha⁻¹. Elements, Ni, Zn, Cu, Cd, Cr, and Pb accumulated in plants from MSW amended soil, but the degree of metal accumulation was the least in seeds in comparison to other plant parts (root, stem and leaf). Moreover, Ni, Zn, Cd and Pb, were in high concentration in all plant parts. It is recorded that the level of 200 kg ha⁻¹ MSW amendment caused better growth and yield of wheat, but progressive levels of metal accumulation in plant parts were recorded due to increase in amendment levels. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

Surface reaction of Bacillus cereus biomass and its biosorption for lead and copper ions

In this study, the surface chemical functional groups of Bacillus cereus biomass were identified by Fourier transform infrared （FTIR） analytical technique. It had been shown that the B. cereus cells mainly contained carboxyl, hydroxyl, phosphate, amino and amide functional groups. The potentiometric titration was conducted to explain the surface acid-base properties of aqueous B. cereus biomass. The computer program FITEQL 4.0 was used to perform the model calculations. The optimization results indicated that three sitesthree pKas model, which assumed the cell surface to have three distinct types of surface organic functional groups based on the IR analysis results, simulated the experimental results very well. Moreover, batch adsorption experiments were performed to investigate biosorption behavior of Cu（Ⅱ） and Pb（Ⅱ） ions onto the biomass. Obviously, the adsorption equilibrium data for the two ions were reasonably described by typical Langmuir isotherm.     

Modelling soil organic carbon dynamics in two long-term experiments of north-eastern Italy

Simulation models are widely used to assess the impacts of management and environmental variables on soil organic matter dynamics, to address questions on ecosystem sustainability and carbon cycling under global change. We tested the Century ecosystem model for two long-term experiments in north-eastern Italy: one (SF) comparing nutrient management treatments in small confined plots containing widely contrasting soil types (i.e., sandy, clay and peat) and the other (CR) involving a field study with crop rotation, nutrient, and management intensity variables. The organic matter changes in the SF experiment, showed a strong, linear relationship with C inputs from crop residues and added manures in the sand and clay soils, which was closely mimicked by the model. There was a net loss of soil C for all treatments in the peat soil, but the rate and overall magnitude of C losses were accurately simulated by the model, which suggested that treatment effects on soil C inputs was the major determinant of SOC dynamics in all three soils. In the CR experiment the model reasonably simulated the large initial decline (averaging about 30% of initial levels) in SOC observed in all treatments, as well as mean treatment effects over the course of the experiment. The model predicted a general pattern of higher SOC in the high management intensity, high fertility treatment combinations and lower SOC in the low management intensity, low fertility treatments; however, observed soil C did not show a clear pattern related to the treatments. Simulated soil C contents were linearly related to C input levels in the different treatments while there was no significant relationship between measured soil C and C inputs based on observed data.     

碱渣海洋倾倒定点化学追踪试验

碱渣海洋倾倒，在夏季温度、盐度和密度跃层存在下，以ｐＨ、浊度为化学追踪指示值，于北黄海５号倾废区进行的三个航次定点化学追踪试验，讨论了碱渣入海后的沉降速度，扩散时间和飘移距离。选择ｐＨ、浊度值作为碱渣海洋倾倒化学追踪指示值是一种尝试。实验室模拟及海上现场试验结果表明，它们在碱渣海洋倾倒中定量描述碱渣在海水中的时空分布是可行的。可作为研究碱渣海洋倾倒区划分合理性应用，并可提供基本依据。     

Interpretation of out-diffusion experiments on crystalline rocks using random walk modeling

Matrix diffusion in saturated rocks with very low permeability is one of the major mechanisms of solute transport. Laboratory out-diffusion experiments on rock samples may provide an estimate of the bulk diffusion coefficient. However, numerous results have shown that this average parameter does not really depict the complex mechanism of diffusion as a function of the internal heterogeneity of crystalline rocks. Two-dimensional images of the porosity distribution in a granite sample were obtained by impregnation with a radioactive resin and autoradiography. Some examples based on these images and synthetic images were used to perform numerical simulations of out-diffusion using two different random walk methods. The simulated shapes of the out-diffusion curves depend on the spatial distribution of the porosity and on the pore connectivity with the border of the sample. Such relations might explain the multiple nested slopes or the convex shapes often observed on real experimental curves.     

Testing the ability of males and females to respond to altered songs in the dueting green lacewing, Chrysoperla plorabunda (Neuroptera: Chrysopidae)

Green lacewings in the carnea group of Chrysoperla engage in species-specific heterosexual duets using low-frequency substrate-borne signals. Within each species, both sexes sing nearly identical songs. Songs are the principal barriers to hybridization between sympatric species in the complex. Here, we investigated the responsiveness of males and females of Chrysoperla plorabunda to synthesized, prerecorded songs that differed from the species mean in the period between repeated volleys of abdominal vibration. We tested 15–16 males and 15–16 females using playbacks of two signals that gradually increased or decreased in volley period, starting at the species mean. We found that (1) duets during courtship are accurate, interactive, and adjustable by each participant; (2) in staged duets, both sexes respond best to song tempos near the mean volley period of their population, but can nonetheless maintain duets with signals of nearly twice, or half, the normal volley period; (3) individuals fine-tune their adjustments to signals of different volley periods by changing their own volley duration and latent period, or less often by inserting extra volleys or skipping every other volley; (4) males are significantly better at matching signals of changing tempo than females; and (5) the range of song responsiveness of C. plorabunda does not overlap the natural range of volley periods found in Chrysoperla adamsi, an acoustically similar sibling species, thus reaffirming strong behavioral isolation. In sum, the precise, almost unbreakable heterosexual duets characteristic of song species of the carnea group result from tight mutual feedback between partners. Effective reproductive isolation between species can be based on song differences alone.     

The maximum power principle: An empirical investigation

The maximum power principle is a potential guide to understanding the patterns and processes of ecosystem development and sustainability. The principle predicts the selective persistence of ecosystem designs that capture a previously untapped energy source. This hypothesis was investigated empirically in controlled and replicated tests conducted in planktonic microcosms. Microecosystems that developed under a pH-controlled light regime, in which light duration was altered based on changes in an ecosystem-controllable variable (water column pH), were compared with those that developed under fixed photoperiods. According to the principle, pH-decreasing (and power-increasing) organization should selectively persist under pH-controlled light. To assess changes in pH dynamics that occurred under the alternative selection regime, in which photoperiods were not linked with pH-affecting selection or organization, the microecosystems that developed under fixed photoperiods were subjected to pH-controlled light on the last day of each test. The daily light duration increased 506 min on average in microecosystems that developed under pH-controlled light and 412 min on average in microecosystems that developed under fixed photoperiods. Selective reinforcement of acid-secreting blue-green algae in response to CO₂ and nutrient limitations could account for the greater increase in power acquisition in microecosystems that developed under pH-controlled light.