Natural attenuation of septic system nitrogen by anammox

On-site disposal of sewage in septic systems can lead to groundwater plumes with NO(3)(-)-N concentrations exceeding the common drinking water limit of 10 mg/L. Currently, denitrification is considered as the principal natural attenuation process. However, at a large seasonal-use septic system in Ontario (256 campsites), a suboxic zone exists where nitrogen removal of up to 80% occurs including removal of NH(4)(+)-N. This zone has both NO(3)(-)-N and NH(4)(+)-N at >5 mg/L each. In the distal NH(4)(+)-rich zone, NH(4)(+)-N concentrations (8.1 ± 8.0 mg/L) are lower than in the proximal zone (48 ± 36 mg/L) and NH(4)(+)-N is isotopically enriched (concentration-weighted mean δ(15)N of +15.7‰) compared to the proximal zone (+7.8‰). Furthermore, δ(15)N-NH(4)(+) isotopic enrichment increases with depth in the distal zone, which is opposite to what would result if nitrification along the water table zone was the mechanism causing NH(4)(+) depletion. Bacterial community composition was assessed with molecular (DNA-based) analysis and demonstrated that groundwater bacterial populations were predominantly composed of bacteria from two Candidatus genera of the Planctomycetales (Brocadia and Jettenia). Together, these data provide strong evidence that anaerobic ammonium oxidation (anammox) plays an important role in nitrogen attenuation at this site.     

试论伊犁盆地库捷尔太铀矿床常量元素的活动性

传统的对控矿层间氧化带的研究往往偏重于铀及其相应的伴生元素(Se、Mo、V、Re、Ga等)的地球化学行为,而对常量元素中非变价元素如：Si、Al、Na、K等研究还很不充分。事实上,层间氧化作用过程中,随着成矿流体的运移和水一岩反应的进行,介质的物理化学条件如Eh、pH等必然会发生显著的改变,而这些改变或多或少的总会在成矿主岩中最常见的元素如：Si、Al、Fe、Na、K的地球化学行为上显示出来。这种改变首先体现在含有上述元素的矿物上的一系列变化,并最终导致元素含量上的改变。不同的元素在这一过程中具有不同的地球化学行为,按照其迁入迁出的强度,这些元素可以划分为活动组分、次活动组分和惰性组分3类。     

Multilevel samplers as microcosms to assess microbial response to biostimulation

Passive multilevel samplers (MLS) containing a solid matrix for microbial colonization were used as in situ microcosms in conjunction with a push-pull biostimulation experiment designed to promote biological U(VI) and Tc(VII) reduction. MLS were deployed at 24 elevations in the injection well and two downgradient wells to investigate the spatial variability in microbial community composition and growth prior to and following biostimulation. The microbial community was characterized by real-time quantitative polymerase chain reaction (Q-PCR) quantification of bacteria, NO(3)(-)-reducing bacteria (nirS and nirK), delta-proteobacteria, Geobacter sp., and methanogens (mcrA). Pretest cell densities were low overall but varied substantially with significantly greater bacterial populations detected at circumneutral pH (t-test, alpha= 0.05), suggesting carbon substrate and low pH limitations of microbial activity. Although pretest cell densities were low, denitrifying bacteria were dominant members of the microbial community. Biostimulation with an ethanol-amended ground water resulted in concurrent NO(3)(-) and Tc(VII) reduction, followed by U(VI) reduction. Q-PCR analysis of MLS revealed significant (1 to 2 orders of magnitude, Mann-Whitney U-test, alpha= 0.05) increases in cell densities of bacteria, denitrifiers, delta-proteobacteria, Geobacter sp., and methanogens in response to biostimulation. Traditionally, characterization of sediment samples has been used to investigate the microbial community response to biostimulation; however, collection of sediment samples is expensive and not conducive to deep aquifers or temporal studies. The results presented demonstrate that push-pull tests with passive MLS provide an inexpensive approach to determine the effect of biostimulation on contaminant concentrations, geochemical conditions, and the microbial community composition and function.     

广义Radon变换的正交展开和反演

本文具体给出了广义Ｒａｄｏｎ变换在函数空间Ｌ＾２（Ｒ＾ｎ,Ｗｎ）上的正交函数展开形式,由此得到了广义Ｒａｄｏｎ变换的反演公式,从而推广了Ｌｏｕｉｓ和Ｄａｖｉｓｏｎ的工作。     

The 2.5-5.0 micrometers spectra of Io: evidence for H2S and H2O frozen in SO2

Infrared spectra of Io in the region 2.5-5.0 micrometers, including new observational data, are analyzed using detailed laboratory studies of plausible surface ices. Besides the absorption bands attributable to sulfur dioxide frosts, four infrared spectral features of Io are shown to be unidentified. These unidentified features show spatial and temporal band strength variations. One pair is centered around 3.9 micrometers (3.85 and 3.91 micrometers) and the second pair is centered around 3.0 micrometers (2.97 and 3.15 micrometers). These absorptions fall close to the fundamental stretching modes in H2S and H2O, respectively. The infrared absorption spectra of an extensive set of laboratory ices ranging from pure materials, to binary mixtures of H2S and H2O (either mixed at different concentrations or layered), to H2O:H2S:SO2 mixtures are discussed. The effects of ultraviolet irradiation (120 and 160 nm) and temperature variation (from 9 to 130 K) on the infrared spectra of the ices are examined. This comparative study of Io reflectance spectra with the laboratory mixed ice transmission data shows the following: (1) Io's surface most likely contains H2S and H2O mixed with SO2. The 3.85- and 3.91-micrometers bands in the Io spectra can be accounted for by the absorption of the S-H stretching vibration (nu 1) in H2S clusters and isolated molecules in an SO2-dominated ice. The weak 2.97- and 3.15-micrometers bands which vary spatially and temporally in the Io spectra coincide with the nu 3 and nu 1 O-H stretching vibrations of clusters of H2O molecules complexed, through hydrogen bonding and charge transfer interactions, with SO2. (2) The observations are well matched qualitatively by the transmission spectra of SO2 ices containing about 3% H2S and 0.1% H2O which have been formed by the condensation of a mixture of the gases onto a 100 K surface. (3) No new features are produced in the region 2.5 to 5.0 micrometers in the spectrum of these ices under prolonged ultraviolet irradiation or temperature variation up to 120 K. (4) Comparison of the Io spectra to transmission spectra of both mixed molecular ices and layered ices indicates that only the former can explain the shifts and splitting of the absorption bands seen in the Io spectrum and additionally can account for the fact that solid H2S is observed in the surface material of Io at temperature and pressure conditions above the sublimation point of pure H2S.     

Approximate solution for solute transport during spherical-flow push-pull tests

An approximate analytical solution to the advection-dispersion equation was derived to describe solute transport during spherical-flow conditions in single-well push-pull tests. The spherical-flow case may be applicable to aquifer tests conducted in packed intervals or partially penetrating wells. Using results of two-dimensional numerical simulations, we briefly illustrate the applicability of the derived spherical-flow solution and provide a comparison with its cylindrical-flow counterpart. Good agreement between simulated extraction-phase breakthrough curves and the spherical-flow solution was found when the length of the injection/extraction region was small compared to both aquifer thickness and maximum solute frontal position at the end of the injection phase. On the other hand, discrepancies between simulated breakthrough curves and the spherical-flow solution increased with increasing anisotropy in hydraulic conductivities. Several inherent limitations embedded in its derivation such as assumptions of isotropy and homogeneity warrant the cautious use of the spherical-flow solution.     

海洋的作用与海洋科学面临的挑战

近若干年来,世界已经历了惊人的变化: ·经济实力(而不是军事威力)正迅速地转变为确保国家未来的安全和国民健康的原动力; ·技术的进步正在加速进行,大大超过了决策者对技术进步效果价值认识的步伐; ·全球增温和气候变化的潜在威胁已成为那些确定国家科研日程的人们的主导思想; ·绝大多数的公共教育体系正迅速地丧失对准备改变新世界秩序的儿童的竞争力;     

The discovery of a new infrared emission feature at 1905 wavenumbers (5.25 microns) in the spectrum of BD +30 degrees 3639 and its relation to the polycyclic aromatic hydrocarbon model

We have discovered a new IR emission feature at 1905 cm-1 (5.25 microns) in the spectrum of BD +30 degrees 3639. This feature joins the family of well-known IR emission features at 3040, 2940, 1750, 1610, "1310," 1160, and 890 cm-1 (3.3, 3.4, 5.7, 6.2, "7.7," 8.6, and 11.2 microns). The origin of this new feature is discussed and it is assigned to an overtone or combination band involving C-H bending modes of polycyclic aromatic hydrocarbons (PAHs). Laboratory work suggests that spectral studies of the 2000-1650 cm-1 (5.0-6.1 microns) region may be very useful in elucidating the molecular structure of interstellar PAHs. The new feature, in conjunction with other recently discovered spectral structure, suggests that the narrow IR emission features originate in PAH molecules rather than large carbon grains. Larger species are likely to be the source of the broad underlying "plateaus" seen in many of the spectra.