Quantifying urban heat island intensity in Hong Kong SAR, China

This paper addresses the methodological concerns in quantifying urban heat island (UHI) intensity in Hong Kong SAR, China. Although the urban heat island in Hong Kong has been widely investigated, there is no consensus on the most appropriate fixed point meteorological sites to be used to calculate heat island intensity. This study utilized the Local Climate Zones landscape classification system to classify 17 weather stations from the Hong Kong Observatory’s extensive fixed point meteorological observation network. According to the classification results, the meteorological site located at the Hong Kong Observatory Headquarters is the representative urban weather station in Hong Kong, whereas sites located at Tsak Yue Wu and Ta Kwu Ling are appropriate rural or nonurbanized counterparts. These choices were validated and supported quantitatively through comparison of long-term annual and diurnal UHI intensities with rural stations used in previous studies. Results indicate that the rural stations used in previous studies are not representative, and thus, the past UHI intensities calculated for Hong Kong may have been underestimated.     

An interlaboratory comparison of sediment elutriate preparation and toxicity test methods

Elutriate bioassays are among numerous methods that exist for assessing the potential toxicity of sediments in aquatic systems. In this study, interlaboratory results were compared from 96-h Ceriodaphnia dubia and Pimephales promelas static-renewal acute toxicity tests conducted independently by two laboratories using elutriate samples prepared from the same sediment. The goal of the study was to determine if the results from the elutriate tests were comparable between two U.S. Environmental Protection Agency (USEPA) laboratories when different elutriate preparation procedures were employed by each lab. Complete agreement in site characterization was attained in 22 of the 25 samples for both bioassays amongst each lab. Of the 25 samples analyzed, 10 were found to be toxic to at least one of the species tested by either laboratory. The C. dubia elutriate tests conducted by the National Exposure Research Laboratory (NERL) indicated that 7 of the 25 sediment samples were toxic, while 8 sediment samples were characterized as such in testing conducted by USEPA Region 6 (Region 6). The P. promelas elutriate tests conducted by NERL determined 8 samples as toxic, while Region 6 tests displayed toxicity in 5 of the samples. McNemar's test of symmetry for C. dubia (S?=?0.33, p?=?0.5637) and P. promelas (S?=?3.0, p?=?0.0833) tests indicated no significant differences in designating a site toxic between NERL and Region 6 laboratories. Likewise, Cohen's kappa test revealed significant agreement between NERL and Region 6 C. dubia (K?=?0.7148, p?<?0.01) and P. promelas (K?=?0.6939, p?<?0.01) elutriate tests. The authors conclude that differences in interlaboratory elutriate preparation procedures have no bearing on the ability of either the C. dubia or P. promelas bioassay testing methods to detect toxicity while yielding similar results.     

Preparation and measurement methods for studying nanoparticle aggregate surface chemistry

Despite best efforts at controlling nanoparticle (NP) surface chemistries, the environment surrounding nanomaterials is always changing and can impart a permanent chemical memory. We present a set of preparation and measurement methods to be used as the foundation for studying the surface chemical memory of engineered NP aggregates. We attempt to bridge the gap between controlled lab studies and real-world NP samples, specifically TiO(2), by using well-characterized and consistently synthesized NPs, controllably producing NP aggregates with precision drop-on-demand inkjet printing for subsequent chemical measurements, monitoring the physical morphology of the NP aggregate depositions with scanning electron microscopy (SEM), acquiring "surface-to-bulk" mass spectra of the NP aggregate surfaces with time-of-flight secondary ion mass spectrometry (ToF-SIMS), and developing a data analysis scheme to interpret chemical signatures more accurately from thousands of data files. We present differences in mass spectral peak ratios for bare TiO(2) NPs compared to NPs mixed separately with natural organic matter (NOM) or pond water. The results suggest that subtle changes in the local environment can alter the surface chemistry of TiO(2) NPs, as monitored by Ti(+)/TiO(+) and Ti(+)/C(3)H(5)(+) peak ratios. The subtle changes in the absolute surface chemistry of NP aggregates vs. that of the subsurface are explored. It is envisioned that the methods developed herein can be adapted for monitoring the surface chemistries of a variety of engineered NPs obtained from diverse natural environments.     

Odour-based species recognition in two sympatric species of sac-winged bats (<Emphasis Type="Italic">Saccopteryx bilineata,S. leptura)</Emphasis>: combining chemical analyses,behavioural observations and odour preference tests

Combining chemical analysis and odour preference tests, we asked whether two closely related sympatric species of sac-winged bats use odour for species recognition. Males of the two sister species Saccopteryx bilineata and Saccopteryx leptura have pouches containing an odoriferous liquid in their antebrachial wing membrane, which is used in S. bilineata during courtship displays. Although both species occasionally share the same daytime roosts and are morphologically similar, there is no evidence for interbreeding. We compared the production and composition of the wing sac odorant in male S. leptura and S. bilineata and performed odour preference tests with female S. bilineata. Similar to male S. bilineata, male S. leptura cleansed and refilled their wing sacs with secretions, but they spent more time each day in doing so than male S. bilineata. Chemical analysis by gas chromatography and mass spectrometry revealed that male Saccopteryx carried species-specific scents in their wing sacs. Binary choice tests confirmed that female S. bilineata preferred the wing sac scents of male S. bilineata to those of the sister species, suggesting that the species specificity of male wing sac scents maintain the pre-mating isolation barrier between these closely related species.     

Influence of groundwater recharge and well characteristics on dissolved arsenic concentrations in southeastern Michigan groundwater

Arsenic concentrations exceeding 10 μg/l, the United States maximum contaminant level and the World Health Organization guideline value, are frequently reported in groundwater from bedrock and unconsolidated aquifers of southeastern Michigan. Although arsenic-bearing minerals (including arsenian pyrite and oxide/hydroxide phases) have been identified in Marshall Sandstone bedrock of the Mississippian aquifer system and in tills of the unconsolidated aquifer system, mechanisms responsible for arsenic mobilization and subsequent transport in groundwater are equivocal. Recent evidence has begun to suggest that groundwater recharge and characteristics of well construction may affect arsenic mobilization and transport. Therefore, we investigated the relationship between dissolved arsenic concentrations, reported groundwater recharge rates, well construction characteristics, and geology in unconsolidated and bedrock aquifers. Results of multiple linear regression analyses indicate that arsenic contamination is more prevalent in bedrock wells that are cased in proximity to the bedrock-unconsolidated interface; no other factors were associated with arsenic contamination in water drawn from bedrock or unconsolidated aquifers. Conditions appropriate for arsenic mobilization may be found along the bedrock-unconsolidated interface, including changes in reduction/oxidation potential and enhanced biogeochemical activity because of differences between geologic strata. These results are valuable for understanding arsenic mobilization and guiding well construction practices in southeastern Michigan, and may also provide insights for other regions faced with groundwater arsenic contamination.     

Natural variability and correlations in the metabolic profile of healthy Eisenia fetida earthworms observed using ¹H NMR metabolomics

¹H NMR metabolomics can be used to assess the sub-lethal toxicity of contaminants to earthworms by identifying alterations in the metabolic profiles of contaminant- exposed earthworms in contrast to those of healthy (control) individuals. In support of this method this study sought to better characterize the baseline metabolic profile of healthy, mature earthworms of the species, Eisenia fetida, which is recommended for both acute and sub-lethal toxicity testing for soil contaminants. Profiles of D₂O-buffer extracted metabolites were determined using ¹H NMR spectroscopy and both inter-individual metabolic variability and pair-wise metabolic correlations were assessed. The control earthworm extracts exhibited low overall inter-individual metabolic variability, with a spectrum-wide median relative standard deviation (%RSD = standard deviation/mean × 100) of 14%, which suggests that the metabolic profile of E. fetida earthworms is well controlled in laboratory conditions and supports further use of this organism in environmental metabolomics research. In addition, strong positive correlations were detected between the levels of maltose, betaine, glycine, and glutamate as well as between the levels of lactate, valine, leucine, alanine, lysine, tyrosine, and phenylalanine which had not previously been reported. Since comparison of pair-wise metabolic correlations between control and treated organisms can reveal changes in the underlying pattern of biochemical relationships between the metabolites, identification of these significant metabolic correlations in control earthworms provides an additional characteristic that may be applied to delineate between control and treated earthworms in future NMR-based metabolomic studies.     

A Quantitative Review of Urban Ecosystem Service Assessments: Concepts,Models, and Implementation

Although a number of comprehensive reviews have examined global ecosystem services (ES), few have focused on studies that assess urban ecosystem services (UES). Given that more than half of the world’s population lives in cities, understanding the dualism of the provision of and need for UES is of critical importance. Which UES are the focus of research, and what types of urban land use are examined? Are models or decision support systems used to assess the provision of UES? Are trade-offs considered? Do studies of UES engage stakeholders? To address these questions, we analyzed 217 papers derived from an ISI Web of Knowledge search using a set of standardized criteria. The results indicate that most UES studies have been undertaken in Europe, North America, and China, at city scale. Assessment methods involve bio-physical models, Geographical Information Systems, and valuation, but few study findings have been implemented as land use policy.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-014-0504-0) contains supplementary material, which is available to authorized users.     

Note On The Use of Law Students as an Air Management Resource

Abstract

In this research, pilot-scale trickle bed biofilter systems have been analyzed to determine their effectiveness in controlling toluene in waste gas streams. These studies evaluated two synthetic microbial attachment media—a monolithic channelized medium and a pelletized ceramic medium. Operational parameters considered included toluene loading, empty bed residence time (EBRT), temperature, and long-term operation. The channelized medium provided 99% removal efficiency for a toluene loading of 0.725 kg COD/m³-day during the initial stages. However, continuous operation resulted in reduced and erratic efficiencies, due to air channeling caused by random plugging. After biomass accumulated within the channels and was subsequently removed by hosing, performance of the channelized medium never regained the previous levels. Similarly, the pelletized medium exhibited consistently good performance until the accumulation of excess biomass in the medium interstices also caused overall performance to deteriorate.

Implementation of a suitable backwashing strategy for biomass control was achieved for the pelletized medium by using full medium fluidization. This strategy permitted long-term operation of the biofilter at a toluene loading of 2.27 kg COD/m³-day and 1 minute EBRT, with efficiencies consistently over 99% and no appreciable back-pressure development between successive periods of backwashing.     

Field Method Comparison between Passive Air Samplers and Continuous Monitors for VOCs and NO2 in El Paso,Texas

Abstract

This study evaluates the performance of Model 3300 Ogawa Passive Nitrogen Dioxide (NO₂) Samplers and 3M 3520 Organic Vapor Monitors (OVMs) by comparing integrated passive sampling concentrations to averaged hourly NO₂ and volatile organic compound (VOC) measurements at two sites in El Paso, TX. Sampling periods were three time intervals (3-day weekend, 4-day weekday, and 7-day weekly) for three consecutive weeks. OVM concentrations were corrected for ambient pressure to account for higher elevation. Precise results (<5% relative standard deviation, RSD) were found for NO₂ measurements from collocated Ogawa samplers. Reproducibility was lower from duplicate OVMs for BTEX (benzene, toluene, ethylbenzene, and xylene isomers) VOCs (≥7% RSD for 2-day samples) with better precision for longer sampling periods. Comparison of Ogawa NO₂ samplers with chemiluminescence measurements averaged over the same time period suggested potential calibration problems with the chemiluminescence analyzer. For BTEX species, generally good agreement was obtained between OVMs and automated-gas chromatograph (auto-GC) measurements. The OVMs successfully tracked increasing levels of VOCs recorded by the auto-GCs.