肥料调控强化象草对重度Cd污染农田修复效果

象草（Pennisetum purpureum Schumach.）因适应能力强、生长迅速和生物量大,且具有一定的经济效益,在重金属污染土壤植物修复中有很好的应用前景.通过田间试验,研究不同肥料（有机肥、复合肥和追施氮肥）联合施用强化象草修复重度Cd污染农田的效果.结果表明：①不同肥料调控处理降低了土壤pH值,提高了土壤有机质含量,根际土壤总Cd含量较修复前降低了8.3%~23.3%,土壤有效态Cd含量较对照降低了11.7%~34.6%;②不同肥料调控处理显著促进了象草生长和对Cd的吸收累积,象草地上部生物量增加29.2%~368.2%,象草Cd总累积量增加了37.8%~283.9%,其中有机肥+复合肥+追施氮肥处理（F3N）象草Cd总累积量达到了145.48 g·hm^-2;③不同肥料联合对提高象草Cd累积量的效果为：有机肥+复合肥+追施氮肥>有机肥+复合肥>单一复合肥.因此,在重度Cd污染农田植物修复中,肥料调控可以强化象草对土壤中Cd的富集移除效果,进而加快对污染农田的修复.     

Mitigating Greenhouse Gas Emissions from Rice-Wheat Cropping Systems in Asia

The rice-wheat belt comprises nearly 24–27 million ha in South and East Asia. Rice is generally grown in flooded fields whereas the ensuing wheat crop requires well-drained soil conditions. Consequently, both crops differ markedly in nature and intensity of greenhouse gas (GHG) fluxes, namely emission of (1) methane (CH₄) and (2) nitrous oxide (N_2O) as well as the sequestration of (3) carbon dioxide. Wetland rice emits large quantities of CH₄; strategies to CH₄ emissions include proper management of organic inputs, temporary (mid-season) field drainage and direct seeding. As for the wheat crop, the major GHG is N_2O that is emitted in short-term pulses after fertilization, heavy rainfall and irrigation events. However, N_2O is also emitted in larger quantities during fallow periods and during the rice crop as long as episodic irrigation or rainfall result in aerobic-anaerobic cycles. Wetland rice ensures a relatively high content of soil organic matter in the rice-wheat system as compared to permanent upland conditions. In terms of global warming potential, baseline emissions of the rice-wheat system primarily depend on the management practices during the rice crop while emissions from the wheat crop remain less sensitive to different management practices. The antagonism between CH₄ and N_2O emissions is a major impediment for devising effective mitigation strategies in rice-wheat system - measures to reduce the emission of one GHG often intensify the emission of the other GHG.     

硅藻土负载纳米铁对Cd2+的吸附性能与机制研究

为了提高硅藻土(CDt)的吸附能力,采用NaBH_4液相还原二价铁法合成负载纳米铁的硅藻土颗粒(nZVI-CDt),运用扫描电镜(SEM)、傅里叶红外光谱(FTIR)、X射线衍射(XRD)和X射线光电子能谱(XPS)对nZVI-CDt进行表征,采用静态吸附法研究不同吸附条件对CDt和nZVI-CDt吸附Cd~(2+)的影响,并结合等温吸附属性、吸附过程控制步骤以及吸附动力学、热力学属性分析探讨了CDt和nZVI-CDt对Cd~(2+)的吸附机制.结果表明,负载纳米铁后,硅藻土的团聚现象得到改善,分散性更好,表面活性基团向有利于吸附方向发生变化,吸附能力得到显著提升,相对于CDt,nZVI-CDt对Cd~(2+)的吸附量提升了3.9倍;nZVI-CDt对Cd~(2+)的吸附较为迅速,20 min左右就可达到吸附平衡;随着投加量的增加,nZVI-CDt对Cd~(2+)的吸附量呈下降趋势,而初始浓度对Cd~(2+)的吸附影响则正好相反;相对于CDt,溶液初始pH值对nZVI-CDt吸附Cd~(2+)的影响明显减弱;nZVI-CDt对Cd~(2+)的吸附能力受温度影响不大;nZVI-CDt对Cd~(2+)的吸附符合Temkin等温吸附模型和拟二级动力学模型.吸附反应容易进行,且以物理吸附为主,吸附过程控制步骤为发生在微孔内的吸附反应.吸附热力学参数表明CDt和nZVI-CDt对Cd~(2+)的吸附是自发的吸热过程,且系统的无序性增加.     

Some results of snow chemical surveys in the Kunnes River valley,East Tienshan mountains,China

Chemical surveys of snow were carried out in the upper reaches of the Kunnes River, a tributary of the Yili River in East Tienshan Mountains, China. Some surprisingly high values of sodium and potassium (K⁺+Na⁺) ranging from 4.44 to 8.99 mg/l compared with other data from neighboring areas are detected. Moreover, some relative high values of SO₄²⁻ with mean concentration 15.8 mg/l for new snow and 14.40 mg/l for deposited snow, ranging from 10.43 to 23.71 mg/l are also found. Therefore, it is inferred that the sodium and potassium (K⁺+Na⁺) are in the forms of sulfate and that the sources of the sulfate are deserts and some dried lakes in Central Asia. It is also found that there is obviously spatial variation of ions such as K⁺+Na⁺, Ca²⁺, SO₄²⁻ and HCO₃⁻. The concentrations of K⁺+Na⁺ and SO₄²⁻, and that of Ca²⁺ and HCO₃⁻ have similar spatial pattern. The temporal pattern of ion concentration of new snow is considered to be mainly controlled by the depth and area of snow cover in the study area and in the areas to the west.     

Spatial sampling and the environment: some issues and directions

In this paper we summarize research issues for spatial environmental sampling stemming from a NISS/USEPA workshop held on 21-22 September 1994 at Chapel Hill, NC.     

稻田土壤对铵的矿物固定对土壤保氮作用的贡献

为了定量评价土壤对铵的矿物固定作用在土壤对肥料氮的保持作用中的相对贡献,通过室内培养试验和分析测定,研究了湖南省几种主要母质发育的水稻土对添加铵的矿物固定作用及其对土壤保氮作用的贡献。结果表明:土壤对外源铵的矿物固定是土壤重要的保氮机制之一,但不同土壤对保氮作用的相对贡献大小不一,以河沙泥的固铵作用对土壤保氮作用的贡献最大,固铵量占总保氮量的51.5%,红黄泥最低,固铵量仅占总保氮量的17.1%,其余五种土壤的固铵作用对土壤保氮作用的贡献大小顺序依次是黄泥田(43.7%)、湖潮泥(35.5%)、紫泥田(35.4%)、灰泥田(25.0%)、麻沙泥(20.8%)。     

Photochemical ozone creation potentials (POCPs) for different emission sources of organic compounds under European conditions estimated with a Master Chemical Mechanism

Through the combined application of a speciated VOC emission inventory and an explicit chemical mechanism, a picture has been put together of the different contributions to photochemical ozone formation from 248 VOC emission source categories. The study has shown that the different VOC emission source categories show vastly different propensities for forming photochemical ozone as indexed by their photochemical ozone creation potentials (POCPs). POCPs range from close to zero for numerous processes, including halocarbon solvent usage, through to over 70 for diesel combustion and some reactive solvent and other product usage applications. The consequences of the large range in POCPs are highlighted for cost-effective VOC emission control strategies across north west Europe.     

Size-resolved,real-time measurement of water-insoluble aerosols in metropolitan Atlanta during the summer of 2004

During the month of August 2004, the size-resolved number concentration of water-insoluble aerosols (WIA) from 0.25 to 2.0 μm was measured in real-time in the urban center of Atlanta, GA. Simultaneous measurements were performed for the total aerosol size distribution from 0.1 to 2.0 μm, the elemental and organic carbon mass concentration, the aerosol absorption coefficient, and the aerosol scattering coefficient at a dry (RH=30%) humidity. The mean aerosol number concentration in the size range 0.1–2.0 μm was found to be 360±175 cm⁻³, but this quantity fluctuated significantly on time scales of less than one hour and ranged from 25 to 1400 cm⁻³ during the sample period. The mean WIA concentration (0.25–2.0 μm) was 13±7 cm⁻³ and ranged from 1 to 60 cm⁻³. The average insoluble fraction in the size range 0.25–2.0 μm was found to be 4±2.5% with a range of 0.3–38%. The WIA population was found to follow a consistent diurnal pattern throughout the month with concentration maxima concurring with peaks in vehicular traffic flow. WIA concentration also responded to changes in meteorological conditions such as boundary layer depth and precipitation events. The temporal variability of the absorption coefficient followed an identical pattern to that of WIA and ranged from below the detection limit to 55 Mm⁻¹ with a mean of 8±6 Mm⁻¹. The WIA concentration was highly correlated with both the absorption coefficient and the elemental carbon mass concentration, suggesting that WIA measurements are dominated by fresh emissions of elemental carbon. For both the total aerosol and the WIA size distributions, the maximum number concentration was observed at the smallest sizes; however the WIA size distribution also exhibited a peak at 0.45 μm which was not observed in the total population. Over 60% of the particles greater than 1.0 μm were observed to be insoluble in the water sampling stream used by this instrumentation. Due to the refractive properties of black carbon, it is highly unlikely that these particles could be composed of elemental carbon, suggesting a crustal source for super-micron WIA.     

A possible in situ 3H and 3He source in Earth’s interior: an alternative explanation of origin of 3He in deep Earth

Origin of ³He in the Earth is a mystery. Lacking a production mechanism, scientists assume ³He was trapped in the Earth, when the Earth was formed. In contrast to this assumption, we have found ³He and ³H concentrations in excess of the atmospheric values in the deep waters of the volcanic Lakes Pavin (France), Laacher (Germany) and Nemrut (Turkey). This paper reports the result of finding ³H in these three volcanic lakes that appear to originate from the mantle. Because ³H has a half-life of 12.3 years, this ³H and the resulting ³He must have formed recently in the mantle and not be part of a primordial reservoir. The nuclear reactions that generate tritium might be a source of “missing” energy in the interior of the Earth.