宁夏生态移民社区生活空间融合与重构的影响因素及机理——以宁夏闽宁镇为例

生态移民的空间位移引致了迁入区多因素的相互作用及长期演化,成为多学科深入探究的重要问题之一。以闽宁镇生态移民社区为例,采用主成分分析法和地理探测器分析法,对生态移民社区生活空间融合的影响因素和机理进行了研究,结果发现：（1）生态移民社区生活空间融合与重构受多种因素影响,生活基础设施、经济收入增长、移民社区环境、邻里关系、政府政策、民族生活六个主成分对生态移民社区生活空间融合的影响可以起到解释作用。（2）影响生态移民社区生活空间的因子解释力由强到弱依次排序为：X₁生活基础设施>X₂经济收入增长>X₃邻里关系>X₄政府政策>X₅民族生活>X₆移民社区环境;交互探测结果表明社区各要素因子交互后因子解释力呈双线性增强,即任意两个因子交互作用对于生态移民社区生活空间融合的影响强度都大于单个因子的独自作用强度。（3）各影响因素之间的互动影响,共同促进生态移民社区固有的生活方式、文化习惯、社会交往关系的演化,进而形成了生活空间的融合与重构。     

Construction of platinum-tipped redox probes for determining soil redox potential

Redox probes are typically constructed by soldering Pt wire to a metal wire or rod, such as copper or brass. The junction between the Pt and wire or rod is often sealed with an epoxy resin and hardener or with heat-shrink tubing. Microcracks (small cracks invisible to the unaided eye) can form in the hardened resin and result in incorrect readings. The hardened resin is not easily removed, making repairs difficult. Heat-shrink tubing is thin, lacks rigidity, and can be damaged in the soil. The method described in this paper used a thick-walled, adhesive-lined terminal insulator to seal the junction. The terminal insulators were easily applied and removed, which made faulty probes easy to repair. Two-hundred forty probes were made with this method and eight were made with a marine epoxy resin. The probes were tested with a redox buffer solution (Light Solution) and were usable if they read +476 +/- 10 mV. The probes were installed 0.76 and 1.5 m deep in the soil. The ability of the probes to provide reliable redox readings was examined by testing selected probes after 10 mo of use and testing all of the probes after completion of the study (19 mo). Ten of the twelve probes tested after 10 mo worked satisfactorily, while the other two clearly malfunctioned before testing. After the study was completed, 236 of the 240 of the probes worked satisfactorily. These results indicate that the construction method presented produces reliable, long-lasting probes.     

A Brief Overview of Carbon Sequestration Economics and Policy

This article provides an overview of the issues and challenges involved in analyzing the costs and program design for carbon sequestration. The first section examines some of the pitfalls of comparing the results of carbon sequestration cost studies and suggests some simple ways in which analysts could make their results more useful. The pitfalls in comparing studies include different definitions for the summary statistic dollars per ton, differences in the type of costs that are estimated, and differences in underlying assumptions regarding program design and implementation. Future cost studies will benefit from improved treatment of leakage, general equilibrium interactions, and public finance interactions. The second section reviews issues related to the implementation of a carbon sequestration program, including which policy tools are available and which have received the most attention, some of the challenges for using those policy tools, and one alternative that has received little attention, but may become necessary. The discussion also provides an overview and analysis of the bills introduced in the last two congresses and considers the general policy implications of those proposals.     

Trends in water quality in LEASEQ rivers and streams (northwestern Ohio), 1975-1995. Lake Erie Agricultural Systems for Environmental Quality

Trends in water quality in four northwest Ohio rivers over the period 1975-1995 were identified using datasets of daily concentrations containing 4500 to 6800 observations per river during the study period. Concentrations were log-transformed prior to analysis, and adjusted for flow using a locally weighted scatterplot smoother (LOWESS) fit between log(concentration) and log(flow). Seasonality was modeled using one- and two-cycle sinusoidal oscillations and monthly additive constants. Substantial decreases in total and soluble reactive phosphorus were documented at all stations. Smaller but highly significant decreases in total Kjeldahl nitrogen were documented at all stations, and significant decreases in total suspended solids were documented at three of the four stations. Nitrate did not show significant trends at the two stations draining major watersheds, and showed significant trends in opposite directions at the two stations on smaller watersheds. Comparisons using nonparametric, nonlinear trend fits (LOWESS) suggest that changes in fertilizer and manure application rates are the most important cause of trends in phosphorus and total Kjeldahl nitrogen; point sources are insufficient to account for the phosphorus trends. The conflicting trends for nitrate are enigmatic, but may reflect diverging land use in the two smaller watersheds.     

Construction of a permeable reactive barrier in a residential neighborhood

In June 2001, the Massachusetts Department of Environmental Protection (DEP) installed a permeable reactive barrier (PRB) within a roadway in Needham, Massachusetts, to treat a plume of chlorinated solvents migrating toward two public water‐supply wells located in the adjacent town of Wellesley, Massachusetts. The solvents originated from an electronics manufacturer located approximately 2,300 feet upgradient of the roadway and 5,200 feet upgradient of the public supply wells. Chlorinated solvents, primarily trichloroethene (TCE), had migrated past the roadway to within 300 feet of the public supply wells. Two contaminant transport models prepared by the DEP's design contractor and the EPA indicated that the plume would reach the well field if no response actions were taken. To mitigate the future impact to the municipal well field, the DEP decided to install a PRB composed of zero‐valent granular iron across the path of the plume along Central Avenue in Needham. Though several dozen PRBs have been installed at sites worldwide and the technology is no longer considered innovative, the application of the technology in a roadway that receives 17,000 vehicles per day within a residential neighborhood is unique and presented difficulties not typically associated with PRB installations. The Needham PRB was also one of the first zero‐valent iron PRBs installed using the slurry trench method to treat chlorinated compounds. © 2002 Wiley Periodicals, Inc.     

Resilience of Norovirus GII.4 to Freezing and Thawing: Implications for Virus Infectivity

Genogroup II.4 norovirus (NoV) remains the predominant NoV strain in food- and water-borne outbreaks. Capsid integrity as well as viral RNA persistence were determined for GII.4 NoV by real-time RT-PCR after 1?C14 freeze/thaw (F/T) cycles (?80?°C/+22?°C) or after ?80?°C storage for up to 120?days. In both cases, capsid integrity and viral RNA titers remained stable. RNase was exogenously added after 1?C14 F/T cycles, but did not alter the amount of genomic NoV RNA detected, indicating that capsids remained intact. Presumptive NoV infectivity was evaluated in functional studies by a porcine gastric mucin binding assay. Viruses frozen and thawed up to 14× bound similarly to porcine mucin, suggesting no reduction in virus infectivity. Overall, this study shows that a) NoV particles retain their integrity for at least 14 F/T cycles, b) long-term (120?day) frozen storage does not decrease NoV RNA titers, and c) capsid binding to receptor-like glycoprotein moieties remains unaltered after 14 F/T cycles. This work indicates that freezing and thawing of foods or beverages would not be a practical processing intervention to reduce NoV contamination. Likewise, repeated freezing and thawing, as might be encountered during winter months, is not expected to inactivate NoV in the environment. Results do show that laboratory samples destined for molecular biological analyses or for use as positive controls may be repeatedly frozen and thawed without any anticipated reduction in NoV RNA titers. This study documents the cryostability of NoV capsids and RNA to freezing and thawing and to the possible retention of virus infectivity.     

Co-existing populations of Pacific ocean perch, Sebastes alutus, in Queen Charlotte Sound, British Columbia

Variation at five microsatellite loci (Sal1, Sal2, Sal3, Sal4 and Sal5) was examined in approximately 1300 Pacific ocean perch (Sebastes alutus) sampled from 14 coastal sites in British Columbia, Canada. Mean observed heterozygosities by locus ranged from 71% to 88%, and by sample ranged from 75% to 84%. Theta values ranged from 0 to 0.04 over the five loci, and averaged 0.015. Among Pacific ocean perch samples, Š ranged from 0.001 to 0.056. Canonical discriminate analysis of multilocus genotypes and neighbour-joining analysis of pairwise genetic distances between samples both indicated the presence of three populations, one off the west coast of Vancouver Island (the Vancouver Island population) and two co-existing populations in Queen Charlotte Sound, Dixon Entrance and along the west coast of the Queen Charlotte Islands (the eastern and western QCI populations). Pacific ocean perch of the eastern and western QCI populations were caught in close proximity to each other, but individual samples showed little evidence of admixture. Fall and spring samples collected within geographic areas were genetically similar, indicating seasonally stable population structure. Restricted gene flow between the Vancouver Island and the two more northerly populations may result from limited adult dispersal and larval retention within the California Current and Alaska Gyre, respectively, but the presence of two populations within Queen Charlotte Sound cannot be explained entirely by larval retention hypotheses. The presence of two Pacific ocean perch populations in central British Columbia has implications for fisheries management.     

An on-farm survey of spatial and temporal stratifications of 17β-estradiol concentrations

17β-estradiol (E2) is a natural estrogenic hormone found in animal manure and urine, which may cause endocrine disruption in sensitive organisms. 17β-Estradiol has been widely detected in the environment, and animal agriculture may be an important source. The objectives of this study were to investigate the potential sources and/or spatial and temporal characteristics contributing to detections of E2 at the farm-scale. Soil cores, segmented into 0.15 m increments, were taken down to the water table from four locations (three potential E2 sources and one control) at or around a swine (Sus scrofa domesticus) farm on five different dates between 2006 and 2007. Estradiol was quantified in the soil-water extracts using liquid chromatography-with tandem mass spectrometry (LC/MS/MS) analysis. Estradiol detections were widespread and found in 128 out of 345 extractions (37%). Concentrations ranged from 0 to 1910 ng L⁻¹ (porewater equivalents). A location that received field application of manure had significantly lower E2 concentrations compared to other locations. Also, the spring 2007 E2 concentrations were significantly higher than all other sample dates, perhaps related to climatic and hydrological events. Results suggested E2 was not directly related to manure sources, but was widespread in this environment. Where E2 was detected, highest concentrations favored the upper profile, while the greatest frequency of detections was in the lower profile and near the water table. Detections of E2 were associated with high organic mater contents in the upper profile and high sand contents in the lower profile. The study suggests that E2 is widespread in some soil environments, raising questions as to the source and mechanisms that facilitate its transport and mobility.     

Feasibility of ultraviolet-light-emitting diodes as an alternative light source for photocatalysis

The objective of this study was to determine whether ultraviolet-light-emitting diodes (UV-LEDs) could serve as an efficient photon source for heterogeneous photocatalytic oxidation (PCO). An LED module consisting of 12 high-power UV-A (lambda max = 365 nm) LEDs was designed to be interchangeable with a UV-A fluorescent black light blue (BLB) lamp for a bench scale annular reactor packed with silica-titania composite (STC) pellets. Lighting and thermal properties of the module were characterized to assess its uniformity and total irradiance. A forward current (I(F)) of 100 mA delivered an average irradiance of 4.0 mW cm(-2) at a distance of 8 mm, which is equivalent to the maximum output of the BLB, but the irradiance of the LED module was less uniform than that of the BLB. The LED and BLB reactors were tested for the oxidization of ethanol (50 ppm(v)) in a continuous-flow-through mode with 0.94 sec residence time. At the same average irradiance, the UV-A LED reactor resulted in a lower CO2 production rate (19.8 vs. 28.6 nmol L(-1) s(-1)), lower ethanol removal (80% vs. 91%), and lower mineralization efficiency (28% vs. 44%) than the UV-A BLB reactor. Ethanol mineralization was enhanced with the increase of the irradiance at the catalyst surface. This result suggests that reduced ethanol mineralization in the LED reactor relative to the BLB reactor at the same average irradiance could be attributed to the nonuniform irradiance over the photocatalyst, that is, a portion of the catalyst was exposed to less than the average irradiance. The potential of UV-A LEDs may be fully realized by optimizing the light distribution over the catalyst and utilizing their instantaneous "on" and "off" feature for periodic irradiation. Nevertheless, our results also showed that the current UV-A LED module had the same wall plug efficiency (WPE) of 13% as that of the UV-A BLB, demonstrating that UV-A LEDs are a viable photon source both in terms of WPE and PCO efficiency.     

Factors affecting nitrate distribution in shallow groundwater under a beef farm in South Eastern Ireland

Groundwater contamination was characterised using a methodology which combines shallow groundwater geochemistry data from 17 piezometers over a 2 yr period in a statistical framework and hydrogeological techniques. Nitrate–N (NO₃-N) contaminant mass flux was calculated across three control planes (rows of piezometers) in six isolated plots. Results showed natural attenuation occurs on site although the method does not directly differentiate between dilution and denitrification. It was further investigated whether NO₃-N concentration in shallow groundwater (<5 m below ground level) generated from an agricultural point source on a 4.2 ha site on a beef farm in SE Ireland could be predicted from saturated hydraulic conductivity (K_sat) measurements, ground elevation (m Above Ordnance Datum), elevation of groundwater sampling (screen opening interval) (m AOD) and distance from a dirty water point pollution source. Tobit regression, using a background concentration threshold of 2.6 mg NO₃-N L⁻¹ showed, when assessed individually in a step wise procedure, K_sat was significantly related to groundwater NO₃-N concentration. Distance of the point dirty water pollution source becomes significant when included with K_sat in the model. The model relationships show areas with higher K_sat values have less time for denitrification to occur, whereas lower K_sat values allow denitrification to occur. Areas with higher permeability transport greater NO₃-N fluxes to ground and surface waters. When the distribution of Cl⁻ was examined by the model, K_sat and ground elevation had the most explanatory power but K_sat was not significant pointing to dilution having an effect. Areas with low NO₃ concentration and unaffected Cl⁻ concentration points to denitrification, low NO₃ concentration and low Cl⁻ chloride concentration points to dilution and combining these findings allows areas of denitrification and dilution to be inferred. The effect of denitrification is further supported as mean groundwater NO₃-N was significantly (P < 0.05) related to groundwater N₂/Ar ratio, redox potential (Eh), dissolved O₂ and N₂ and was close to being significant with N₂O (P = 0.08). Calculating contaminant mass flux across more than one control plane is a useful tool to monitor natural attenuation. This tool allows the identification of hot spot areas where intervention other than natural attenuation may be needed to protect receptors.