Ambient ammonia in terrestrial ecosystems: a comparative study in the Tennessee Valley, USA

Atmospheric ammonia has been shown to degrade regional air quality and affect environmental health. In-situ measurements of ammonia are needed to determine how ambient concentrations vary in different ecosystems and the extent to which emission sources contribute to those levels. The objective of this study was to measure and compare ammonia concentrations in two Tennessee Valley (USA) ecosystems: a forested rural area and a metropolitan site adjacent to a main transportation route. Integrated samples of atmospheric ammonia were collected with annular denuder systems for ~ 4 weeks during the summer of 2009 in both ecosystems. Ancillary measurements of meteorological variables, such as wind direction and precipitation, were also conducted to determine any relationships with ammonia concentration. Measurements in the two ecosystems revealed ammonia concentrations that were mostly representative of background levels. Arithmetic means were 1.57 ± 0.68 μg m^− 3 at the metropolitan site and 1.60 ± 0.77 μg m^− 3 in the forest. The geometric mean concentrations for both sites were ~ 1.46 μg m^− 3. Wind direction, and to a lesser extent air temperature and precipitation, did influence measured concentrations. At the metropolitan site, ammonia concentrations were slightly higher in winds emanating from the direction of the interstate highway. Meteorological variables, such as wind direction, and physical factors, such as topography, can affect measurement of ambient ammonia concentrations, especially in ecosystems distant from strong emission sources. The 12-h integrated sampling method used in this study was unable to measure frequent changes in ambient ammonia concentrations and illustrates the need for measurements with higher temporal resolution, at least ~ 1-2 h, in a variety of diverse ecosystems to determine the behavior of atmospheric ammonia and its environmental effects.     

Extracting dust from soil: a simple solution to a tricky task

Air quality is commonly assessed by the ambient concentration of airborne particles sized smaller than 10 microm (PM10). However, in addition to concentration, particle shape as well as the type and bioaccessibility of elements adsorbed to this particulate fraction are likely to be related to subsequent respiratory health effects. In order to investigate this relationship, a relatively large mass of the relevant size fraction is needed since sample preparation is necessary prior to analysis. Most existing methods for sampling dust have been developed for analysing the dust directly, without prior handling or digestion. In order to provide sufficient material to be used for subsequent bioaccessibility analysis, these methods require repetitive and time consuming sampling as well as special equipment and procedures which are high in both cost and maintenance. This paper describes an inexpensive and relatively simple procedure for extracting the PM10 fraction from soil to be used for lung bioaccessibility studies. The method described involves dry and wet sieving in order to exclude larger size fractions as far as possible. Vacuum filtering of the wet-sieved soil solution through a 10 microm mesh was then employed to extract the required fraction. In order to avoid frequent blocking of the mesh, Stokes's law was applied in the construction of a tube which enables separation of the solution holding the smallest fraction.     

Evaluation of duct opening protection in two-hour fire walls and partitions

There is a continuing debate among fire protection specialists on the value and role of fire dampers in preventing fire spread via HVAC duct systems. It has been recognized that fire dampers are not required under all circumstances. For example, NFPA 90A,Standard for the Installation of Air Conditioning and Ventilation Systems, does not require the installation of fire dampers in ducts penetrating one-hour fire-rated walls and partitions. Additionally, there are circumstances where the closure of dampers may affect critical environmental air systems. In these situations, the value of fire dampers must be determined in terms of an overall risk assessment. It has been suggested that the role of fire dampers be considered in terms of the total building fire protection system, but a quantitative approach for such an assessment has been previously unavailable. In particular, there has been no data related to the performance of a duct system when subjected to a standard two-hour fire exposure. Gewain et al. have described an equivalency approach and full-scale fire test data for the protection of duct openings in two-hour fire-resistant walls and partitions. The objective of this paper is to review and summarize the equivalency rationale and test data and describe engineering methods available to apply an equivalency approach more generally. The approach was developed for situations where horizontal steel ventilation ducts penetrate fire-rated walls and partitions. The approach does not address smoke dampers or ducts containing combustible materials.     

Sustainable reduction in the flux of microbial compliance parameters from urban and arable land use to coastal bathing waters by a wetland ecosystem produced by a marine flood defence structure

'Natural' treatment systems such as wetlands and reed beds have been proposed as sustainable means of reducing fluxes of faecal indicator organisms (FIOs) to recreational and shellfish harvesting waters. This is because FIO fluxes to coastal waters from both point (effluent) and diffuse (catchment) sources can cause non-compliance with microbiological standards for bathing and shellfish harvesting waters. The Water Framework Directive requires competent authorities in the member states to manage both point and diffuse sources of FIOs in an integrated manner to achieve compliance with 'good' water quality as defined in a series of daughter Directives. This study was undertaken to investigate the relative sources of FIOs to the popular bathing waters around Clacton, UK. In this predominantly arable (mainly cereal cropping) farming area, the principal land use predictor, explaining 76% of the variance in geometric mean presumptive Escherichia coli concentration at sub-catchment outlets during the bathing season, was the proportion of built-up (i.e. urbanised) land in each sub-catchment. This new finding contrasts with earlier studies in livestock farming regions where the proportion of improved grassland has proven to be the strongest predictor of microbial concentration. Also novel in this investigation, a flood defence wall has been built creating a wetland area which discharges every tidal cycle. The wetland produces over 97% reduction in the flux and concentrations of FIOs to the marine recreational waters. Also, FIO concentrations in water draining through the wetland to the sea were similar to concentrations measured in six UK sewage treatment plant effluents subject to secondary (biological) treatment followed by UV disinfection.     

Heavy metals in seawater: Effects on limpet pedal mucus production

Toxicological modification of molluscan mucus production has largely been ignored. This is probably due to an underestimation of the r le of mucus in molluscan physiology and its energetic cost. This paper reports that laboratory exposure to episodic doses of waterborne copper and zinc serve to reduce pedal mucus production by the common limpet Patella vulgata L. to about 60% of the unstressed rate. The metals are effective in this respect at concentrations as low as 10 μg l⁻¹, which in the case of zinc is below the current U.K. environmental quality standard. All metal doses reduced mucus production to the same level. This suggests a behavioural response of the limpet, limiting activity. The reduction in mucus production has important consequences both for limpet ecology and for the ways in which biological energy allocation and transformation are assessed.     

Impact of a magnetic ion exchange resin on ozone demand and bromate formation during drinking water treatment

The objective of this research was to examine the impact of a magnetic ion exchange resin (MIEX) on ozone demand and bromate formation in two different ozonated waters at bench scale. The first raw water had a high bromide ion concentration, a high ozone demand, and was highly colored. Based on experimental findings from the first water, the second water was selected as a model water in which more controlled experiments were performed. The waters were treated with the MIEX resin using jar test procedures to find the optimal MIEX dosage based upon the removal of ultraviolet (UV)-absorbing substances, dissolved organic carbon (DOC), and bromide. The optimal resin dosage was chosen for bulk MIEX treatment and subsequent ozonation in a semi-batch reactor. The ozone demand and formation of bromate were analyzed as a function of ozone dosage and dissolved ozone concentration for the MIEX pre-treated water, and compared to the results obtained by ozonating the water without MIEX pre-treatment. The results indicate that pre-treatment of the water with the MIEX resin significantly reduces total organic carbon, DOC, UV absorbance, color, and to some extent, bromide. MIEX pre-treatment of the water prior to ozonation substantially lowered the ozone demand and formation of bromate during subsequent ozonation.     

Recovery and detection of Cryptosporidium parvum oocysts from water samples using continuous flow centrifugation

Continuous flow centrifugation (CFC) was used in conjunction with immunomagnetic separation (IMS) and immunofluorescence microscopy (IFA) and nested PCR to recover and detect oocysts of Cryptosporidium parvum and cysts of Giardia intestinalis from 10L volumes of source water samples. Using a spiking dose of 100 oocysts, nine of 10 runs were positive by IFA, with a mean recovery of 4.4+/-2.27 oocysts; when another 10 runs were analyzed using nested PCR to the TRAP C-1 and Cp41 genes, nine of 10 were positive with both PCR assays. When the spiking dose was reduced to 10 oocysts in 10L, 10 of 12 runs were positive by IFA, with a mean oocyst recovery of 3.25+/-3.25 oocysts. When 10 cysts of Giardia intestinalis were co-spiked with oocysts into 10L of source water, five of seven runs were positive, with a mean cyst recovery of x=0.85+/-0.7. When 10 oocysts (enumerated using a fluorescence activated cell sorter) were spiked into 10L volumes of tap water, one of 10 runs was positive, with one oocyst detected. For the majority of the source water samples, turbidities of the source water samples ranged from 1.1 to 22 NTU, but exceeded 100 NTU for some samples collected when sediment was disturbed. The turbidities of pellets recovered using CFC and resuspended in 10 mL of water were very high (exceeding 500 NTU for the source water-derived pellets and 100 NTU for the tap water-derived pellets). While not as efficient as existing capsule-filtration based methods (i.e., US EPA methods 1622/1623), CFC and IMS may provide a more rapid and economical alternative for isolation of C. parvum oocysts from highly turbid water samples containing small quantities of oocysts.     

用信息取代规制：寻找塑造城市设计的另一种方式

本文的写作目的既不是为了展示研究成果，也不是为了批评（或表扬）规制（regulation）。我的目的是提出两个问题．有没有替代规制的可行方法？如果有，我们能在哪里找到模型7我建议通过关注一个领域来完成这个任务。     

Minimizing the Consequences of Intentional Attack on Water Infrastructure

Abstract:  Since September 11, 2001, protecting the nation's water infrastructure and improving water network resiliency have become priorities in the water industry. In this work, we develop methods to mitigate the consequences of water shortage resulting from destruction of facilities in water networks. These methods integrate search techniques, such as branch-and-bound and genetic algorithms, with a hydraulic solver to check demand feasibilities across a residual water network. The objective is to identify a feasible customer demand pattern that minimizes the consequences of water shortage in the downgraded network. We present a mathematical model of the problem addressed along with an exact solution methodology and several heuristics. We apply these methodologies to three water networks ranging in size from approximately 10–700 nodes and compare the solution quality and computational efficiency.     

The effects of strongly complexing ligands on the adsorptive partitioning of metal ions

This work investigated the effects of polyphosphate, a model ligand which forms strong complexes with metals, on metal sorption onto ferrihydrite. Adsorption experiments were conducted to study the partitioning of metal ions in systems containing a range of metal and ligand concentrations. The sorption of ligands, the associated sorption of charge and complexation of metals by ligands are important in controlling metal partitioning. In metal-free systems, the apparent maximum adsorption density is about 0.1 mol of polyphosphate per mol of Fe. The sorption of metals and/or metal-ligand complexes increases the maximum sorption density of ligands compared to systems where metal ions are not present. At total polyphosphate concentrations less than that needed to saturate the oxide surface, the presence of polyphosphate enhances the sorption of metals. When the concentration of polyphosphate exceeds that needed to saturate the oxide surface, the sorption of metals diminishes due to both the competition between dissolved and surface polyphosphate for metal ions and the dissolution of iron oxides.