基于溶解无机碳中碳氧同位素及化学组分的瓶装饮用水产地真实性鉴别

为了鉴别我国市场上销售的瓶装饮用水的产地和产品类型,本试验分析了瓶装饮用水溶解无机碳(DIC)中的δ¹⁸O_DIC和δ¹³C_DIC、水中的δ¹⁸O和δ²H值、矿物元素(K、Ca、Na、Mg、Sr)含量、阴离子(Cl^-、SO₄^2-、HCO₃^-)含量、pH值与电导率等水化学指标,结合费希尔判别分析(Fisher-DA)建立模型,对瓶装饮用水的类别和产地进行鉴别。结果表明,不同产地瓶装饮用水的δ¹⁸O_DIC、δ¹³C_DIC、δ¹⁸O、δ²H值均具有显著差异,而且矿物元素与阴离子的含量变化范围广,具有不同的地域性特征。产地溯源判别模型对不同产地瓶装饮用水的判别准确率高达100%,且采用水化学指标还能区分瓶装饮用水的类型。正态化重要性分析显示,对产地具有指示效应的前五项重要指标分别为K、Cl^-和δ¹³C_DIC、δ²H和pH值。综上所述,通过稳定同位素指纹信息和水化学指标的差异进行融合分析,结合多元统计模型可有效鉴别市场上瓶装饮用水的真实性,保护消费者的合法权益,维护市场公平。     

Measurement of Si adsorption and “Active Si” in a soil amended with slag fertilizers by using stable isotope 30SP

The silicic acid adsorption by a soil (Eutric Gleysols) where slag fertilizers were applied was measured by the addition of a silicic acid solution labelled with ³⁰Si after soil incubation, in order to study the effect of slag application on the specific Si adsorption by the soil and to estimate the amount of Si in the soil solid phase which can easily enter the soil solution. It was evident that the application of slags increased the ability of soil to adsorb Si. It was also shown that the ³⁰Si added was diluted with not only the Si present in the soil solution but also the Si dissolved from the soil solid phase. We proposed the use of the term “active” for Si in soil which can take part in the isotopic dilution within 1 h. The amount of active Si in the soil solid and liquid phases (D ₆₀ - value) was calculated from the ³⁰Si content in the soil solution and compared with the amount of Si taken up by rice plant (Oryza sativa L.), which was determined in our previous study. The buffering capacity of the soil for Si, which can reflect the ability of soil to maintain the Si concentration in the soil solution constant when Si is added to or removed from the soil, was also determined. The D ₆₀ - value and the Si buffering capacity of the soil increased by slag application. These increases were large when the alkalinity of the applied slags was high. The correlation study revealed that the D ₆₀ - value was a better index of Si availability of the soil than the amount of Si dissolved from the soil solid phase during the incubation when the slags were previously applied.     

Pedogenic carbonate recrystallization assessed by isotopic labeling: a comparison of 13C and 14C tracers

The C isotopic composition (δ¹³C) of pedogenic carbonates reflects the photosynthetic pathway of the predominant local vegetation because pedogenic (secondary) CaCO₃ is formed in isotopic equilibrium with soil CO₂ released by root and rhizomicrobial respiration. Numerous studies show the importance of pedogenic carbonates as a tool for reconstructing paleoecological conditions in arid and semiarid regions. The methodological resolution of these studies strongly depends on the time scale of pedogenic carbonate formation, which remains unknown. The initial formation rate can be assessed by ¹⁴C labeling of plants grown on loess and subsequent incorporation of ¹⁴C from rhizosphere CO₂ into newly formed carbonate by recrystallization of loess CaCO₃. We tested the feasibility of ¹⁴C and ¹³C tracers for estimating CaCO₃ recrystallization rates by simultaneous ¹⁴C and ¹³C labeling and comparison with literature data. ¹⁴C labeling was more efficient and precise in assessing recrystallization rates than ¹³C labeling. This is connected with higher sensitivity of ¹⁴C liquid scintillation counting when compared with δ¹³C measurement by IRMS. Further, assessment of very low amounts of incorporated tracer is more precise with low background signal (natural abundance), which is true for ¹⁴C, but is rather high for ¹³C. Together, we obtained better reproducibility, higher methodological precision, and better plausibility of recrystallization rates calculated based on ¹⁴C labeling. Periods for complete CaCO₃ recrystallization, extrapolated from rates based on ¹⁴C labeling, ranged from 130 (125–140) to 240 (225–255) y, while it was ≈ 600 (365–1600) y based on the ¹³C approach. In terms of magnitude, data from late‐Holocene soil profiles of known age provide better fit with modeled recrystallization periods based on the ¹⁴C approach.     

不同NFC/NDF比日粮对奶山羊瘤胃pH值动态变化的影响

试验采用动态pH值连续监测记录系统对瘤胃pH值进行24h连续监测,旨在研究不同非纤维性碳水化合物/中性洗涤纤维比(NFC/NDF比)日粮对奶山羊瘤胃pH值昼夜动态变化的影响。选用6只安装有永久性瘤胃瘘管的关中奶山羊作为试验动物,采用自身对照试验设计,分为4期,每期10d,依次饲喂NFC/NDF比分别为1.02(Ⅰ期)、1.24(Ⅱ期)、1.63(Ⅲ期)、2.58(Ⅳ期)的4种日粮。结果表明,瘤胃pH值随着日粮NFC/NDF比增加而显著降低(P<0.05),瘤胃pH值<5.2、5.5、5.8、6.0的平均持续时间亦随日粮NFC/NDF比增加而延长,分别由Ⅰ期的0、0、2.42和9.40h/d增加到Ⅳ期的0.33、7.50、17.06和20.53h/d;瘤胃pH值<5.5、5.8、6.0的曲线面积亦逐步加大,分别由Ⅰ期的0、0.21和1.43(pH·h)增加到Ⅳ期的1.09、4.84和8.59(pH·h);而且瘤胃pH值下降速率和下降幅度及最低值所持续的时间亦随日粮NFC/NDF比增加而增加。     

Gaseous and leaching nitrogen losses from no-tillage and conventional tillage systems following surface application of cattle manure

Previous studies have demonstrated inconsistent results on the impact of tillage systems on nitrogen (N) losses from field-applied manure. This study assessed the impact of no-tillage (NT) and conventional tillage (CT) systems on gaseous N losses, N₂O:N₂O + N₂ ratios and NO₃⁻-N leaching following surface application of cattle manure. The study was undertaken during the 2003/2004 and 2004/2005 seasons at two field sites in Nova Scotia namely, Streets Ridge (SR) in Cumberland County and the Bio-environmental Engineering Centre (BEEC) in Truro. Results showed that the NT system had higher (p < 0.05) NH₃ losses than CT. Over the two seasons, manure incorporation in CT reduced NH₃ losses on average by 86% at SR and 78% at BEEC relative to NT. At both sites and during both seasons, denitrification rates and N₂O fluxes in NT were generally higher than in CT plots, presumably due to higher soil water and organic matter content in NT. Over the two seasons, mean denitrification rates at SR were 239 and 119 g N ha⁻¹ d⁻¹, while N₂O fluxes were 120 and 64 g N ha⁻¹ d⁻¹ under NT and CT, respectively. At BEEC mean denitrification rates were 114 and 71 g N ha⁻¹ d⁻¹, while N₂O fluxes were 52 and 27 g N ha⁻¹ d⁻¹ under NT and CT, respectively. Conversely, N₂O:N₂O + N₂ ratios were lower in NT than CT suggesting more complete reduction of N₂O to N₂ under NT. When averaged across all soil depths, NO₃⁻-N was higher (p < 0.05) in CT than NT. Nitrate-N decreased with depth at both sites regardless of tillage. In most cases, NO₃⁻-N was higher under CT than NT at all soil depths. Similarly, flow-weighted average NO₃⁻-N concentrations in drainage water were generally higher under CT. This may be partly attributed to higher denitrification rates under NT. Therefore, NT may be a viable strategy to remove NO₃⁻-N from the soil, and thus, reduce NO₃⁻-N contamination of groundwater. However, it should be noted that while the use of NT reduces NO₃⁻-N leaching it may come with unintended environmental tradeoffs, including increased NH₃ and N₂O emissions.     

同位素溯源技术在食品安全中的应用

疯牛病、口蹄疫、禽流感疫病等对食品安全管理带来新的压力,对人类健康构成了极大的威胁,给疫病发生国造成了严重的经济损失,并带来社会恐慌。同位素溯源技术是国际上目前用于追溯不同来源食品和实施产地保护的有效工具之一,在食品安全污染物溯源领域有着广阔的应用前景,一些发达国家纷纷开展此领域的研究。本文阐述了同位素溯源技术的基本原理,比较了同位素溯源技术与其他溯源技术的区别与联系,综述了国内外研究进展,提出了我国在同位素溯源技术方面应开展的研究工作,旨在推动我国食品安全追溯制度的建立与完善,保障食品安全,保证消费者身体健康。     

Three‐source partitioning of CO2 efflux from maize field soil by 13C natural abundance

A natural‐¹³C‐labeling approach—formerly observed under controlled conditions—was tested in the field to partition total soil CO₂ efflux into root respiration, rhizomicrobial respiration, and soil organic matter (SOM) decomposition. Different results were expected in the field due to different climate, site, and microbial properties in contrast to the laboratory. Within this isotopic method, maize was planted on soil with C₃‐vegetation history and the total CO₂ efflux from soil was subdivided by isotopic mass balance. The C₄‐derived C in soil microbial biomass was also determined. Additionally, in a root‐exclusion approach, root‐ and SOM‐derived CO₂ were determined by the total CO₂ effluxes from maize (Zea mays L.) and bare‐fallow plots. In both approaches, maize‐derived CO₂ contributed 22% to 35% to the total CO₂ efflux during the growth period, which was comparable to other field studies. In our laboratory study, this CO₂ fraction was tripled due to different climate, soil, and sampling conditions. In the natural‐¹³C‐labeling approach, rhizomicrobial respiration was low compared to other studies, which was related to a low amount of C₄‐derived microbial biomass. At the end of the growth period, however, 64% root respiration and 36% rhizomicrobial respiration in relation to total root‐derived CO₂ were calculated when considering high isotopic fractionations between SOM, microbial biomass, and CO₂. This relationship was closer to the 50% : 50% partitioning described in the literature than without fractionation (23% root respiration, 77% rhizomicrobial respiration). Fractionation processes of ¹³C must be taken into account when calculating CO₂ partitioning in soil. Both methods—natural ¹³C labeling and root exclusion—showed the same partitioning results when ¹³C isotopic fractionation during microbial respiration was considered and may therefore be used to separate plant‐ and SOM‐derived CO₂ sources.     

常年淹水稻田甲烷产生潜力和产生途径的季节变化

甲烷的减排问题已成为各国政府和科研人员关注的焦点。稻田是温室气体甲烷的重要排放源,甲烷产生是排放的前提条件,主要有乙酸发酵和CO₂/H₂还原两条途径。常年淹水稻田甲烷排放量高,减排潜力大,但关于这类稻田甲烷产生途径的季节变化规律尚少见报道。于四川省资阳市的常年淹水稻田,采集水稻4个重要生育期(分蘖期、孕穗期、抽穗期、成熟期)的新鲜土样,通过室内厌氧培养试验观测了甲烷产生潜力,并采用稳定性碳同位素方法和氟甲烷(CH₃F,2%)抑制法,量化CO₂/H₂产甲烷的碳同位素分馏系数(α(CO₂/CH₄)),从而定量评估乙酸产甲烷途径的相对贡献率(?乙酸)。结果表明：添加CH₃F显著降低甲烷产生,甲烷产生潜力在成熟期最大,变化范围为3.22～12.71μg·g^–1·d^–1;产生CH₄的δ¹³C值(δ¹³CH_...     

Ratios of Nutrients in Lowland Rice Grown on Two Iron Toxic Soils in Nigeria

ABSTRACT

Iron (Fe) toxicity is a widespread nutritional soil constraint affecting rice production in the wetland soils of West Africa. Critical levels of total iron in plant causing toxicity is difficult to determine as different rice cultivars respond to excessive Fe^{2 +} in various ways in what is called “bronzing” or “yellowing” symptoms (VBS). An investigation was conducted to evaluate the relationship between plant growth and nutrient ratios at four iron levels (1000, 3000, 4000 μ g L^?1) and control. This involved two rice cultivars (‘ITA 212’ and ‘Suakoko 8’), and two soil types (Aeric Fluvaquent and Aeric Tropaquept). The experimental design was a 2 × 2 × 4 factorial in a completely randomized fashion with four replications. The results showed that nutrient ratios [phosphorus (P)/Fe, potassium (K)/Fe, calcium (Ca)/Fe, magnesium (Mg)/Fe, and manganese (Mn)/Fe), Fe content, and Fe uptake vary widely with the iron levels as well as with the age of the cultivars. The iron toxicity scores expressed as VBS increased with increasing Fe^{2 +} in the soils, resulting in simultaneous reduction of the following variables: plant height, tiller numbers/pot, relationships grain yield (GY) and dry matter yield (DMY). There were no significant difference between nutrient ratios, Fe contents, Fe uptake, the GY and DMY of both rice cultivars on both soil types. Multiple stepwise regression analysis showed that Fe uptake and Fe contents contributed 42% and 17% respectively to the variation in the grain yield of ‘ITA 212’ on Aeric Tropaquept. On both soil types and cultivars, Fe uptake and Fe content contributed between 26 and 68% to the variation in the DMY, while the nutrient ratios (P/Fe, K/Fe, Ca/Fe, and Mn/Fe) contributed between 3% and 13% DMY. Thus, it could be concluded that iron toxicity in rice is more a function of a single nutrient (Fe) rather than nutrient ratios.     

同位素示踪法在磺酰脲类除草剂残留分析中的应用

除草剂的同位素残留分析技术日益受到人们的重视,并取得了长足的发展。本文综述了利用同位素示踪技术对4种磺酰脲类除草剂的残留分析进展。