Effective Photoinactivation of Alpha‐Amylase,Catalase and Urease at 222 nm Emitted by an KrCl‐Excimer Lamp

The inactivation of enzymes is of great interest for many industrial applications. The effectiveness of photoinactivation of alpha‐amylase, catalase, and urease with 222 nm radiation was investigated in comparison to that at 254 nm. The enzymes were irradiated with different fluence rates of 222 nm radiation emitted by a KrCl‐excimer lamp and with 254 nm radiation produced by a low‐pressure mercury lamp. The relative activities were calculated before and after irradiation. Degradation caused by UV‐radiation was assessed by SDS‐PAGE analysis. The results clearly demonstrated that inactivation of the proteins is much more effective with the 222 nm excimer lamp compared to the 254 nm mercury lamp. Irradiation with the excimer lamp and a UV‐fluence rate of 1000 J/m² was sufficient to reduce the relative activities of amylase and urease to 15% and that of catalase to 60%. After irradiation with 4000 J/m², the enzyme activity was almost completely inhibited. In contrast, after irradiation with the mercury lamp with an UV‐fluence rate of 4000 J/m², the relative activity was still above 85%. The gel patterns showed no visible degradation after irradiation at 254 nm, but a strong and unspecific degradation was obvious after treatment at 222 nm, presumably caused by cleavage of the peptide bonds.     

Higher effectiveness of photoinactivation of bacterial spores,UV resistant vegetative bacteria and mold spores with 222 nm compared to 254 nm wavelength

Eleven selected species of vegetative bacteria, bacteria spores and mold spores were irradiated with different doses of UV radiation of a 222 nm krypton‐chloride excimer lamp and a 254 nm mercury lamp under laboratory conditions. Then the inactivation curves were determined. The necessary UV fluences for a respective reduction were higher for the excimer lamp for the tested vegetative bacteria of Bacillus cereus, Arthrobacter nicotinovorans, Staphylococcus aureus and Pseudomonas aeruginosa and slightly higher for the spores of Streptomyces griseus and Clostridium pasteurianum. However, less than 250 J/m² UV fluence with 222 nm was sufficient for a 4‐log reduction, depending on the species. On the other hand, the UV fluences for the 254 nm mercury lamp were much higher for the bacterial spores of Bacillus cereus, Thermoactinomyces griseus and the bacteria of Deinococcus radiodurans and slightly higher for the mold spores of Aspergillus niger and Penicillium expansum. The results show that especially the germs with a higher UV resistance and those with more effective repair mechanisms can be inactivated more efficiently by the 222 nm excimer lamp. This may be due to the fact that low UV fluence mainly affects radiation sensitive microorganisms by DNA damage whereas at higher UV fluence (various) mechanisms of protein damage can presumably be held responsible for inactivation.     

Stormflow dynamics and loads of Escherichia coli in a large mixed land use catchment

Storm events are major transporters of faecal microbial contaminants, but few studies have reported storm loads or concentration dynamics in relation to discharge or other pollutants, notably fine sediment. Episodically, high loads of faecal contamination during storm flows impact downstream uses of water bodies, particularly contact recreation and shellfish harvesting. We examined the storm dynamics of Escherichia coli, turbidity and discharge in the mixed land use Motueka catchment (2047 km²; 60% forest and 19% pasture) to gain insights into E. coli sources and transport. We also explored different approaches for calculating E. coli loads. Discharge and field turbidity were recorded continuously, and E. coli concentrations were sampled during events, over a 13‐month period near the mouth of the Motueka River. E. coli loads were estimated by interpolation, averaging estimators and by using linear regression with smearing correction of the log‐transformed variables: discharge, turbidity, and both turbidity and discharge. The annual E. coli load was dominated (～98%) by export during events. Comparison of monthly monitoring with the intensive storm monitoring campaign suggests that simple stratification of the sampling into storm and baseflow would greatly improve export estimates. E. coli peak concentrations always preceded discharge and turbidity peaks (which had similar timing). Turbidity can be a useful surrogate for faecal microbes in smaller catchments, but in the Motueka turbidity was no better for predicting E. coli concentration than discharge. Runoff from grazed pasture and direct deposition from livestock are probably the ultimate E. coli sources in the Motueka catchment. However, in‐channel stores seem to dominate E. coli dynamics during events and account for the typical feature of bacterial concentrations peaking ahead of discharge and turbidity. This study demonstrates the importance of storm events to faecal microbial loads and shows that E. coli concentration dynamics may contrast with those of turbidity. Copyright © 2009 John Wiley & Sons, Ltd.     

Use of Nitrogen‐15‐Enriched Escherichia coli as a Bacterial Tracer in Karst Aquifers

Karst aquifers are susceptible to contamination by microorganisms, but relatively few studies have used bacteria as tracers. We demonstrate the utility of Escherichia coli enriched in the stable isotope nitrogen‐15 (¹⁵N) as a novel bacterial tracer. Nonpathogenic E. coli from two springs in central Kentucky were grown on ¹⁵N‐enriched media. Survival of E. coli and persistence of the isotopic signal were assessed in two sets of laboratory experiments conducted with sterilized spring water in dark microcosms at 14 °C. First, isotopically labeled bacteria survived for 130 d at concentrations within one log unit of the average initial value, and there was no significant difference in δ¹⁵N values from Day 1 to Day 130. Second, water samples with E. coli were inoculated with either of two different species of protozoa (Tetrahymena pyriformis or Colpoda steinii). During 7 d, δ¹⁵N values increased in T. pyriformis while bacterial populations decreased. In a field test, following a 2.1‐cm rainfall, ¹⁵N‐labeled E. coli, solutes (rhodamine WT dye and bromide), and latex microspheres were injected into a sinkhole approximately 530 m upgradient of a spring. Breakthrough of all tracers coincided, but microspheres were remobilized by subsequent storms, unlike other tracers. Enriched E. coli exhibited more tailing than solute tracers during the initial storm‐flow recession. These results indicate that ¹⁵N‐enriched E. coli is a viable tracer of bacterial transport in karst aquifers, although predation may attenuate the isotopic signal in systems that are not rapidly flushed.     

冷季不同植物人工湿地处理生活污水的工程实例分析

本实验以亚热带地区福建省永春县农村生活污水作为处理对象,选取10种湿地植物,构建具有不同植物类型的表面流人工湿地的实例工程,比较不同植物配置人工湿地的处理能力,以及湿地植物的生物量和植物体内氮、磷累积能力.研究结果表明,水龙和美人蕉人工湿地具有较高的铵态氮去除能力,去除率可分别达到76.7%和87.7%;两者同时也对总氮表现出较好的去除效果,尤其是美人蕉人工湿地在冬季节对总氮的去除率可维持在80.3%以上;2014年初冬季节实验结果表明,水龙还具有一定的总磷去除能力,去除率可达到69.0%.水龙和美人蕉具有较大的生物量,其单位面积干重可分别达到0.46和0.30 kg/m~2,又能较好地积累氮、磷元素,其体内氮含量可分别达到6.43和4.60 g/m~2,磷含量可分别达到0.50和1.01 g/m~2.综上所述,种植水龙和美人蕉的人工湿地总体处理效果较好,同时又能更多地积累氮、磷元素,且具有更大的生物量,可选为相对适宜用于处理生活污水的适合亚热带地区应用的人工湿地植物.     

Seasonal variations in internal wave energy in a Scottish sea loch

Near-continuous observations of an internal wave field were made over a period of 13 months at a location in Inchmarnock Water at the northern end of the Clyde Sea. This paper sets out to determine the seasonal form of the energy density of the internal wave field at this location based on the hypothesis that it varies smoothly throughout the year, being greater in summer than in winter. The mooring was maintained between June 1999 and July 2000 in 150-m water with seven deployments. Estimates of kinetic and potential energy density were derived from Acoustic Doppler Current Profiler (ADCP) and vertical temperature profiles respectively. Both were shown to vary on time scales less than 1 month with median values of mean kinetic energy (KE) density0.5 J m^–3 and for mean potential energy (PE) density0.01 J m^–3. The energy of the internal wave field was found to be continuous and without a clear seasonal form. Further, it was also always non-zero with intermittent peaks of much higher energy. In the late autumn the system experienced complete vertical overturning driven by local convective processes destroying the thermocline and causing a reduction in the overall KE density.Responsible Editor: Jens KappeubergOrginally presented as a poster at PECS 2002, Hamburg Germany     

Reduzierung von Bakterien- und Coliphagen-Konzentrationen auf der Fließstrecke eines Klärwerksableiters

Reduction of the Concentration of Bacteria and Coliphages along the Flowing Stretch of a Treated Sewage Channel The efficiency of surface waters to eliminate E. coli, fecal streptococci, Salmonella spp., and coliphages was evaluated in a small river which receives treated wastewater and which is rich in submerged macrophytes. The study took place between April and December, 1994. Total colony count, BOD₅, O₂ concentration and water temperature were determined in the river as well. As the river does not receive additional water downwards along its 17.2 km course, dilution effects could be ruled out as the cause for the elimination of the microorganisms. The reduction is assumed to happen rather due to sedimentation, grazing, and adsorption to the submerged waterplants. Immediately after discharge of the wastewater, the river water contained about 10⁵ cfu/100 mL E. coli and 10⁴ cfu/100 mL fecal streptococci, about 1000 pfu/100 mL coliphages, and, as a rule, was positive for salmonella in 10 mL. The reduction of E. coli, fecal streptococci, salmonella, clostridia, and coliphages at the end of the course was 1 to 2 orders of magnitude. This reduction took place mainly within the first 4.7 km, a part in which, due to low flowing velocities, suspended solids settle down efficiently. Besides, at the end of this part the submerged waterplants are especially abundant. The reduction of suspended solids correlated positively with that of BOD₅, bacteria, and coliphages. The reduction of microorganisms was not sufficient to fulfill the requirements of the European Community guidelines for bathing waters and for surface waters used as drinking water source. The regenerating capacity of surface waters is not sufficient to eliminate pathogens from convenionally treated wastewater. Therefore, tertiary treatment is necessary to keep receiving waters reasonably free from pathogens.     

An improved hemispherical photography model for stream surface shortwave radiation estimations in a central U.S. hardwood forest

Hemispherical photographs of forest canopies can be used to develop sophisticated models that predict incident below canopy shortwave radiation on the surface of interest (i.e. soil and water). Hemispherical photographs were collected on eight dates over the course of a growing season to estimate leaf area index and to quantify solar radiation incident on the surface of two stream reaches based on output from Gap Light Analyser and Hemisfer software. Stream reaches were shaded by a mixed‐deciduous Ozark border forested riparian canopy. Hemispherical photo model results were compared to observed solar radiation sensed at climate stations adjacent to each stream reach for the entire 2010 water year. Modeled stream‐incident shortwave radiation was validated with above‐stream pyranometers for the month of September. On average, the best hemispherical photo models underestimated daily averages of solar radiation by approximately 14% and 12% for E–W and N–S flowing stream reaches, respectively (44.7 W/m² measured vs 38.4 W/m² modeled E–W, 46.8 W/m² vs. 41.1 W/m²N–S). The best hemispherical photo models overestimated solar radiation relative to in–Stream pyranometers placed in the center of each stream reach by approximately 7% and 17% for E–W and N–S stream reaches respectively (31.3 W/m² measured vs 33.5 W/m² modeled E–W, 31.5 W/m² vs. 37.1 W/m²N–S). The model provides a geographically transferable means for quantifying changes in the solar radiation regime at a stream surface due to changes in canopy density through a growing season, thus providing a relatively simple method for estimating surface and water heating in canopy altered environments (e.g. forest harvest). Copyright © 2012 John Wiley & Sons, Ltd.     

A Preliminary Study of Chromophoric Dissolved Organic Matter (CDOM) in Lake Taihu,a Shallow Subtropical Lake in China

The optical properties and spatial distribution of chromophoric dissolved organic matter (CDOM) in Meiliang Bay of Lake Taihu were evaluated and compared to the results in literature. Concentrations of dissolved organic carbon (DOC) ranged from 8.75 to 20.19 mg L^?1 with an average of (13.10 ± 3.51) mg L^?1. CDOM absorption coefficients a(λ) at 280 nm, 355 nm, and 440 nm were in the range 11.28...33.46 m^?1 (average (20.95 ± 5.52) m^?1), 2.42...7.90 m^?1 (average (4.92 ± 1.29) m^?1), and 0.65...2.44 m^?1 (average (1.46 ± 0.44) m^?1), respectively. In general, CDOM absorption coefficient and DOC concentration were found to decrease away from the river inflow to Meiliang Bay towards the lake center. The values of the DOC‐specific absorption coefficients a*(λ), given as absorption coefficient related to mass concentration of organic carbon (C) ranged from 0.28 to 0.47 L mg^?1 m^?1 at 355 nm. The determination coefficients between CDOM absorption and DOC concentration decreased with the increase of wavelength from 280 to 550 nm. The linear regression relationship between CDOM absorption at 280 nm and DOC concentration was following: a(280 nm) = 1.507 L mg^?1 m^?1 · DOC + 1.215 m^?1. The spectral slope S values were dependent on the wavelength range used in the regression. The estimated S values decreased with increasing wavelength range used. A significant negative linear relationship was found between CDOM absorption coefficients, DOC‐specific absorption coefficients and estimated S values especially in longer wavelength range. The linear regression relationship between DOC‐specific absorption coefficients at 440 nm and estimated S values during the wavelength range from 280 to 500 nm was following: a*(440 nm) = (–0.021 μm · S + 0.424) L mg^?1 m^?1.     

Litterfall,litter and associated chemistry in a dry sclerophyll eucalypt forest and a pine plantation in south-eastern Australia: 1. Litterfall and litter

Litterfall was measured in a dry schlerophyll eucalypt forest and a nearby Pinus radiata plantation of similar tree density and basal area near Canberra in south-eastern Australia. Total annual litterfall for the eucalypts was 329 g m⁻², compared with 180 g m⁻² for the pines, with the bark component being 52 g m⁻² for eucalypts and zero for pines. Barkfall did not occur for the eucalypts during the drought of 1982–1983 but complete bark shedding occurred during the subsequent very wet year when barkfall was 177 g m⁻² for Eucalyptus rossii and 146 g m⁻² for Eucalyptus mannifera (9·3 and 7·6 g m⁻² of basal area, respectively). Barkfall of E. rossii responded to rainfall in the period autumn to early summer, whereas E. mannifera responded to summer rainfall. In the eucalypt forest floor-litter was stratified into a surface layer where the components were substantially intact, and a cohesive layer where the components were fragmented and bound together by fungal hyphae. The amount and residence times of loose and cohesive floor-litter were 1056 g m⁻² and 3·2 years, respectively, for the loose litter layer; and 1164 g m⁻² and 3·5 years for the cohesive layer. The litter biomass represented 17% of the estimated total above-ground biomass of 127 tonnes ha⁻¹. A previous study showed roots to be 25% of total biomass, suggesting a total biomass of 167 tonnes ha⁻¹. © 1998 John Wiley & Sons, Ltd.     

Sub‐surface water contribution to recession flow in a mountain headwater stream system based on single monitoring campaign

Discharge in mountain streams may be a mixture of snowmelt, water from surface runoff, and deep return flow through valley bottom alluvia. We used δ¹⁸O and δ²H, solute concentrations, and ²²²Rn to determine water sources of a headwater stream located at the McDonald Creek watershed, Glacier National Park, USA, during summer recession flow period. We analysed minimal water isotope ranges of ?17.6‰ to ?16.5‰ and ?133‰ to ?121‰ for δ¹⁸O and δ²H, respectively, potentially due to dominance of snow‐derived water in the stream. Likewise, solute concentrations measured in the stream through the watershed showed minimal variation with little indication of subsurface water input into the stream. However, we observed ²²²Rn activities in the stream that ranged from 39 to 2646 Bq/m³ with the highest value measured in middle of the watershed associated with channel constriction corresponding to changes in local orientation of underlying rocks. Downstream from this point, ²²²Rn activity decreased from 581 to 117 Bq/m³ in a series of punctuated steps associated with small rapids and waterfalls that we hypothesized to cause radon degassing with a maximum predicted loss of 427 Bq/m³ along a 400 m distance. Based on mass balance calculations using ²²²Rn activity values, streamflow, and channel characteristics, we estimated that groundwater contributed between 0.3% and 29% of total flow. Overall, we estimated a 5.9% of groundwater contribution integrated for stream reach measured at McDonald Creek during recession flow period. Finally, a lower mean hyporheic flux of 14 m³/day was estimated compared to the groundwater flux of 70 710 m³/day. These assessments highlight the potential for radon as a conservative tracer that can be used to estimate subsurface water contribution in mountain streams within a complex geologic setting. Copyright © 2015 John Wiley & Sons, Ltd.     

Uncertainties in field-line tracing in the magnetosphere. Part II: the complete internal geomagnetic field

The discussion in the preceding paper is restricted to the uncertainties in magnetic-field-iine tracing in the magnetosphere resulting from published standard errors in the spherical harmonic coefficients that define the axisymmetric part of the internal geomagnetic field (i.e. g_n⁰ ± g_n⁰). Numerical estimates of these uncertainties based on an analytic equation for axisymmetric field lines are in excellent agreement with independent computational estimates based on stepwise numerical integration along magnetic field lines. This comparison confirms the accuracy of the computer program used in the present paper to estimate the uncertainties in magnetic-field-line tracing that arise from published standard errors in the full set of spherical harmonic coefficients, which define the complete (non-axisymmetric) internal geomagnetic field (i.e. g_n^m ± g_n^m and h_n^m ± h_n^m). An algorithm is formulated that greatly reduces the computing time required to estimate these uncertainties in magnetic-field-line tracing. The validity of this algorithm is checked numerically for both the axisymmetric part of the internal geomagnetic field in the general case (1 n 10) and the complete internal geomagnetic field in a restrictive case (0 m n, 1 n 3). On this basis it is assumed that the algorithm can be used with confidence in those cases for which the computing time would otherwise be prohibitively long. For the complete internal geomagnetic field, the maximum characteristic uncertainty in the geocentric distance of a field line that crosses the geomagnetic equator at a nominal dipolar distance of 2 R_E is typically 100 km. The corresponding characteristic uncertainty for a field line that crosses the geomagnetic equator at a nominal dipolar distance of 6 R_E is typically 500 km. Histograms and scatter plots showing the characteristic uncertainties associated with magnetic-field-line tracing in the magnetosphere are presented for a range of illustrative examples. Finally, estimates are given for the maximum uncertainties in the locations of the conjugate points of selected geophysical observatories. Numerical estimates of the uncertainties in magnetic-field-line tracing in the magnetosphere, including the associated uncertainties in thelocations of the conjugate points of geophysical observatories, should be regarded as first approximations in the sense that these estimates are only as accurate as the published standard errors in the full set of spherical harmomic coefficients. As in the preceding paper, howerver, all computational techniques developed in this paper can be used to derive more realistic estimates of the uncertainties in magnetic-field-line tracing in the magnetosphere, following further progress in the determination of more accurate standard errors in the spherical harmonic coefficients.Also Visiting Reader in Physics, University of Sussex, Palmer, Brighton, BN1 9QH, UK     

Determination of characteristics of steam reservoirs by Radon-222 measurements in geothermal fluids

The authors conducted a Rn²²² survey in wells of the Larderello geothermal field (Italy) and observed considerable variations in concentrations. Simple models show that flow-rate plays an important part in the Rn²²² content of each well, as it directly affects the fluid transit time in the reservoirs. Rn²²² has been sampled from two wells of the Serrazzano area during flow-rate drawdown tests. The apparent volume of the steam reservoir of each of these two wells has been estimated from the Rn²²² concentration versus flow-rate curves.List of symbols Q Flow-rate (kg h^–1) - Decay constant of Rn²²² (=7.553×10^–3 h^–1) - Porosity of the reservoir (volume of fluid/volume of rock) - ₁ Density of the fluid in the reservoir (kg m^–3) - ₂ Density of the rock in the reservoir (kg m^–3) - M Stationary mass of fluid filling the reservoir (kg). - E Emanating power of the rock in the reservoir (nCi kg _rock ^–1 h^–1). - P Production rate of Rn²²² in the reservoir: number of atoms of Rn²²² (divided by 1.764×10⁷) transferred by the rock to the mass unit of fluid per unit time (nCi kg _fluid ^–1 h^–1). - N Specific concentration of Rn²²² in the fluid (nCi kg^–1) - Characteristic time of the steam reservoir at maximum flow-rate (=M/Q)     

Rainfall interception and splash detachment with a Brussels sprouts plant: A laboratory simulation

Rates of splash detachment from a sandy soil of the Cottenham Series, subjected to a five-minute design storm of 50 mm/h with a kinetic energy of 127 J/m² and a median volume drop size of 3·2 mm supplied from a rotating-disc rainfall simulator, are determined without a plant cover and with the cover of a single Brussels sprouts plant. Measurements are made at regular intervals throughout the growing season. Plant canopies of 10 to 25 per cent result in reductions of 10 to 25 per cent in rainfall volume and 10 to 81 per cent in rainfall energy. The volume and energy of the rain beneath the plant are significantly (P < 0·05) correlated with its number of leaves (r = ?0·84 and ?0·92 respectively for n = 49). No reduction was observed in the rate of splash detachment which averages 1·2 kg/m² for the design storm with and without the plant. The detachment rate was found rather surprisingly to be inversely related to the energy of the rainfall under the plant and positively related to the number of leaves. As the number of leaves increases, so does the detachment rate per unit of rainfall energy.     

抚仙湖秋、冬季光衰减特征及其与有色可溶性有机物的关系

为了研究抚仙湖紫外辐射(UVR)和光合有效辐射(PAR)衰减的时空特征及其与有色可溶性有机物(CDOM)、悬浮物(SS)、浮游植物(叶绿素a表征)等因子的关系,于2014年10月(秋季)、2015年1月(冬季)开展现场调查,结果显示:秋季不同波长(段)的漫射衰减系数Kd(305)、Kd(340)和Kd(PAR)分别为1.27±0.12、0.68±0.11和0.32±0.13 m-1,冬季分别为1.13±0.10、0.63±0.07和0.36±0.07 m-1;秋季CDOM的不同波长吸收系数ag(254)、ag(305)和ag(340)分别为4.09±0.26、1.18±0.09和0.57±0.05 m-1,冬季分别为2.95±0.24、0.61±0.11和0.11±0.07 m-1,秋季ag(254)、ag(305)和ag(340)显著高于冬季;秋季Kd(305)显著大于冬季,这与秋季(雨季)较高的CDOM丰度、浮游植物生物量(及SS浓度)有关.秋季ag(305)/Kd(305)、ag(340)/Kd(340)均显著高于冬季;秋季及秋冬季整体而言,ag(254)与Kd(305)、Kd(340)呈显著正相关,各多元逐步回归方程中均包含ag(254),说明CDOM吸收对UVR的衰减有重要贡献.空间差异方面,秋季北部的ag(254)、Kd(305)和Kd(340)显著高于南部,冬季南北部无明显差异,或与雨旱季北岸河流输入的CDOM和SS的情况有关.此外,浮游植物对UV-B衰减的影响和SS(与CDOM的交互作用)对UV-A衰减的影响更在于季节变化方面,而影响UVR、PAR衰减的各因子的相对贡献有待进一步量化.     

A multi‐tracer approach to quantifying groundwater inflows to an upland river; assessing the influence of variable groundwater chemistry

Understanding the behaviour and variability of environmental tracers is important for their use in estimating groundwater discharge to rivers. This study utilizes a multi‐tracer approach to quantify groundwater discharge into a 27 km upland reach of the Gellibrand River in southwest Victoria, Australia. Ten sampling campaigns were conducted between March 2011 and June 2012, and the distribution of ²²²Rn activities, Cl and ³H concentrations imply the river receives substantial groundwater inflows. Mass balances based on ²²²Rn, Cl and ³H yield estimates of groundwater inflows that agree to within ± 12%, with cumulative inflows in individual campaigns ranging from 24 346 to 88 467 m³/day along the studied river section. Groundwater discharge accounts for between 10 and 50% of river flow dependent on the time of year, with a high proportion (>40 %) of groundwater sustaining summer flows. Groundwater inflow is largely governed by regional groundwater flowpaths; between 50 and 90% of total groundwater inflows occur along a narrow 5–10 km section where the river intersects the Eastern View Formation, a major regional aquifer. Groundwater ²²²Rn activities over the 16 month period were spatially heterogeneous across the catchment, ranging between 2000 Bq/m³ and 16 175 Bq/m³. Although groundwater ²²²Rn activities display temporal variation, spatial variation in groundwater ²²²Rn is a key control on ²²²Rn mass balances in river catchments where groundwater and river ²²²Rn activities are within an order of magnitude of each other. Calculated groundwater discharges vary from 8.4 to 15 m³/m/day when groundwater ²²²Rn activities are varied by ± 1 σ. Copyright © 2013 John Wiley & Sons, Ltd.     

The Impact of Biofilm Growth on Transport of Escherichia coli O157:H7 in Sand

Understanding the transport behavior, survival, and persistence of pathogens such as Escherichia coli O157:H7 in the subsurface is essential to protection of public health. In this study, the transport of E. coli O157:H7 in a two‐dimensional bench‐scale sand aquifer system, hereafter referred to as the sandbox, was investigated, with a focus on the impact of biofilm development on E. coli retention and survival. Biofilm growth was initiated through flushing with unsterilized groundwater and addition of glucose, nitrate, and phosphate. Retention of E. coli from an injection test in clean sand, prior to promotion of biofilm growth, was approximately 9%. Subsequent to biofilm growth, 47% of injected E. coli cells were retained under similar flow conditions. After 10 d of no flow, sterile water was flushed through the biofouled sandbox and substantial concentrations (up to 1.5 × 10⁵ cells/mL) of E. coli were measured in the effluent indicating that E. coli had survived the starvation period. Confocal laser scanning microscopy revealed that E. coli were located not only on the surface but also within the biofilm. Imposition of starvation conditions resulted in biofilm sloughing and possible mobilization of biofilm‐associated E. coli.     

Knickpoint recession rate and catchment area: the case of uplifted rivers in Eastern Scotland

Knickpoint behaviour is a key to understanding both the landscape responses to a base‐level fall and the corresponding sediment fluxes from rejuvenated catchments, and must be accommodated in numerical models of large‐scale landscape evolution. Knickpoint recession in streams draining to glacio‐isostatically uplifted shorelines in eastern Scotland is used to assess whether knickpoint recession is a function of discharge (here represented by its surrogate, catchment area). Knickpoints are identified using DS plots (log slope versus log downstream distance). A statistically significant power relationship is found between distance of headward recession and catchment area. Such knickpoint recession data may be used to determine the values of m and n in the stream power law, E = KA^mSⁿ. The data have too many uncertainties, however, to judge definitively whether they are consistent with m = n = 1 (bedrock erosion is proportional to stream power and KPs should be maintained and propagate headwards) or m = 0·3, n = 0·7 (bedrock incision is proportional to shear stress and KPs do not propagate but degrade in place by rotation or replacement). Nonetheless, the E Scotland m and n values point to the dominance of catchment area (discharge) in determining knickpoint retreat rates and are therefore more consistent with the stream power law formulation in which bedrock erosion is proportional to stream power. Copyright © 2005 John Wiley & Sons, Ltd.     

Treatment of Refractory Organics Contained in Actual Agro‐Industrial Wastewaters by UV/H2O2

In this work, the treatment of actual agro‐industrial wastewaters (IWW) by a UV/H₂O₂ process has been investigated. The aqueous wastes were received from industrial olive oil mills and then treated by laboratory scale physicochemical methods, i. e., coagulation using ferrous and aluminum sulfate, decantation, filtration and adsorption on activated carbon. These wastes are brown colored effluents and have a residual chemical oxygen demand (COD) in the range of 1800 to 3500 mgO₂ L^–1, which cannot be further eliminated with physicochemical processes. The UV/H₂O₂ treatments were carried out under monochromatic irradiation at 254 nm using a thermostated reactor equipped with a mercury vapor lamp located in an axial position. The effects of initial H₂O₂ concentration, initial COD, pH and temperature have been studied in order to determine the optimum conditions for maximum color and COD removals. The experimental results reveal the suitability of the UV/H₂O₂ process for both removal of high levels of COD and effectively decolorizing the solution. In particular, 95% of color removal and 90% of COD removal were obtained under conditions of pH = 5 and 32°C using 2.75 g H₂O₂ g^–1 COD L^–1 during 6 h of UV‐irradiation. The treatment is unaffected by pH over the range 2 to 9. In addition, the COD removal is improved by increasing the temperature, whereas the color removal has not been affected by this parameter. The results show that the hydroxyl radicals generated from the catalytic decomposition of H₂O₂ by UV‐irradiation of the solution could be successfully used to mineralize the organics contained in IWW. The mineralization of the organics seems to occur in three main sequential steps: the first is the rapid decomposition of tannins leading to aromatic compounds, which are confirmed by the decolorization of the IWW; the second step corresponds to the oxidation of aromatics leading to aliphatic intermediates, which occurs by the cleavage of an aromatic ring, and is established by the removal of aromatics, and the final step is the slow oxidation of the aliphatic intermediates, which is measured by the COD removal.     

抚仙湖有色可溶性有机物的来源组成与时空变化

基于2017年1-12月在抚仙湖开展的逐月观测,利用紫外-可见吸收光谱和三维荧光光谱技术探讨该湖有色可溶性有机物（CDOM）的来源组成及时空变化特征.12个月CDOM吸收值a（254）的均值为3.47±0.57 m^-1,范围为1.82~5.22 m^-1,说明CDOM丰度较低.平行因子分析结果给出了2种类酪氨酸荧光组分（C1和C3）、1种类色氨酸荧光组分（C2）、1种类腐殖质荧光组分（C4）,12个月内源组分（C1+C3）对总荧光强度的平均贡献为65.81%±15.38%,外源组分（C2+C4）的平均贡献为34.19%±15.38%;荧光指数FI的均值为1.73±0.14,腐殖化指数HIX的均值为1.02±0.37,生源化指数BIX的均值为1.23±0.27,说明CDOM主要为微生物内源产生.时空变化方面,春（3-5月）、夏（6-8月）、秋（9-11月）和冬（1、2、12月）季的a（254）分别为3.20±0.47、3.76±0.64、3.67±0.50和3.23±0.38 m^-1,夏季和秋季均显著高于冬季和春季;CDOM丰度及内外源组分的空间分布具有季节异质性,可能与流域土地利用、河流输入、降雨、温度、光辐射等因素有关.