Indoor Air Quality Intervention in Schools; Effectiveness of a Portable HEPA Filter Deployment in Five Schools Impacted by Roadway and Aircraft Pollution Sources

The Healthy Air, Healthy Schools Study was established in January 2020 to better understand the impact of ultrafine particles (UFP) on indoor air quality in communities surrounding Seattle-Tacoma (Sea-Tac) International Airport. The study team took multipollutant measurements indoor and outdoor air pollution at five participating school locations to infiltration indoors. The schools participating in this project were located within a 7-mile radius of Sea-Tac Airport and within 0.5 miles of an active flight path. Based on experimental measures in an unoccupied classroom, infiltration rates of a) Ultrafine particles of aircraft origin b) Ultrafine particles of traffic origin and c) Wildfire smoke or other outdoor pollutants were characterized before and after the introduction of a classroom based portable HEPA filter intervention. The portable HEPA cleaners were an effective short-term intervention to improve the air quality in classroom environments, reducing the ultrafine particles to approximately 1/10th of that measured outside. Before the HEPA filter deployment, approximately one-half of all outdoor UFPs were measured indoors. This study is unique in focusing on UFP in school settings and demonstrating through multivariate methods that the UFP measured in the classroom space is primarily of outdoor origin. Although existing research suggests that improvements to indoor air quality in homes can significantly improve asthma outcomes, further research is necessary to establish the benefit to student health and academic performance of improved air quality in schools.

Plasma Treatment for Cellulose in Tobacco Paper-Base: The Improvement of Surface Hydrophilicity and Mechanical Property

This paper reports a plasma treatment (PT) method for improving the surface hydrophilicity and mechanical properties of cellulose in reconstituted tobacco paper-base. The absorption and infiltration rates of water droplets on PT-reconstituted tobacco paper-base-15s were significantly accelerated. Notably, the increased content of methylene and alkyl groups enabled the tobacco paper-base to absorb more useful substrates in the tobacco extract after plasma treatment. In addition, the tensile mechanical performance of reconstituted tobacco was significantly improved after plasma treatment, which indicated that the content of organic matter absorbed by the tobacco paper-base sheet was increased. Moreover, tobacco extract infiltrated on the surface of PT-reconstituted tobacco paper-base reached 37.7° within 30 s, while it reached 79.9° on the reconstituted tobacco paper-base. Finally, the mechanism by which the surface hydrophilicity and mechanical properties of the cellulose in the tobacco paper-base were improved is discussed.

Determining the impact of flow velocities on reactive processes associated with Enterococcus faecalis JH2-2

This study focuses on the impact of infiltration rates on colloidal transport and reactive processes associated with E. faecalis JH2-2 using water-saturated sediment columns. The infiltration rates influence the physical transport of bacteria by controlling the mean flow velocity. This, in turn, impacts biological processes in pore water owing to the higher or lower residence time of the bacteria in the column. In the present study, continuous injection of E. faecalis (suspended in saline water with varying conditions of dissolved oxygen and nutrient concentrations) into a lab-scale sediment column was performed at flow velocities of 0.02 cm min−1 and 0.078 cm min−1, i.e., at residence times of 1–5 hours. The impact of residence times on reactive processes is significant for field scale setups. A process-based model with a first-order rate coefficient for each biological process was fitted for each obtained condition-specific dataset from the experimental observations (breakthrough curves). The coefficients were converted to a dimensionless form to facilitate the comparison of biological processes. These results indicate that the processes of attachment and growth were flow-dependent. The growth process in the absence of dissolved oxygen was the most dominant process, with a Damkoehler number of approximately 48.

Study on behavior of ponding time based on characteristics of infiltration rate and rainfall intensity with varying return period

Runoff management is based on two main concepts: controlling runoff discharge and managing concentration (Tc). Tc is closely related to understanding ponding time (tp), which is associated with estimating the length of tp on a land surface. The present study aims to investigate the behavior of tp due to varying infiltration rates (f) and rainfall intensities (i) with different return periods (Tr). The ponding time (tp) was derived from graph analysis of infiltration rate and rainfall intensity with Tr 2, 5, and 10 years. Infiltration measurements were conducted at 8 points using a double-ring infiltrometer. Meanwhile, rainfall data were obtained from 2010 to 2019. The observed tp (tpobs ) was derived through overlying between infiltration rate curve and rainfall intensity. In contrast, empirical tp (tpemp ) was estimated using Horton’s formula. The result confirms that the infiltration rate followed an exponential curve and varying rainfall intensities. Infiltration rates give vary in tp where the longer Tr, the faster the initial time of tp. There was fairly good consistency between tpobs and tpemp as shown by relatively high-value R2 >0.6) for Tr 2, 5, and 10 years. It indicates that the Horton’s formula has reliable to estimate tp in the study area.

Evaluating methods for estimating whole house air infiltration rates in summer: implications for overheating and indoor air quality

PurposeAccurate values for infiltration rate are important to reliably estimate heat losses from buildings. Infiltration rate is rarely measured directly, and instead is usually estimated using algorithms or data from fan pressurisation tests. However, there is growing evidence that the commonly used methods for estimating infiltration rate are inaccurate in UK dwellings. Furthermore, most prior research was conducted during the winter season or relies on single measurements in each dwelling. Infiltration rates also affect the likelihood and severity of summertime overheating. The purpose of this work is to measure infiltration rates in summer, to compare this to different infiltration estimation methods, and to quantify the differences.Design/methodology/approachFifteen whole house tracer gas tests were undertaken in the same test house during spring and summer to measure the whole building infiltration rate. Eleven infiltration estimation methods were used to predict infiltration rate, and these were compared to the measured values. Most, but not all, infiltration estimation methods relied on data from fan pressurisation (blower door) tests. A further four tracer gas tests were also done with trickle vents open to allow for comment on indoor air quality, but not compared to infiltration estimation methods.FindingsThe eleven estimation methods predicted infiltration rates between 64 and 208% higher than measured. The ASHRAE Enhanced derived infiltration rate (0.41 ach) was closest to the measured value of 0.25 ach, but still significantly different. The infiltration rate predicted by the “divide-by-20” rule of thumb, which is commonly used in the UK, was second furthest from the measured value at 0.73 ach. Indoor air quality is likely to be unsatisfactory in summer when windows are closed, even if trickle vents are open.Practical implicationsThe findings have implications for those using dynamic thermal modelling to predict summertime overheating who, in the absence of a directly measured value for infiltration rate (i.e. by tracer gas), currently commonly use infiltration estimation methods such as the “divide-by-20” rule. Therefore, infiltration may be overestimated resulting in overheating risk and indoor air quality being incorrectly predicted.Originality/valueDirect measurement of air infiltration rate is rare, especially multiple tests in a single home. Past measurements have invariably focused on the winter heating season. This work is original in that the tracer gas technique used to measure infiltration rate many times in a single dwelling during the summer. This work is also original in that it quantifies both the infiltration rate and its variability, and compares these to values produced by eleven infiltration estimation methods.

Hydraulic Properties of Forest Soils with Stagnic Conditions

Tree species, e.g., shallow vs. deep rooting tree species, have a distinct impact on hydrological properties and pore size distribution of soils. In our study, we determined the soil hydrologic properties and pore size distribution at three forest stands and one pasture as reference on soils with stagnant water conditions. All sites are located in the Wermsdorf Forest, where historical studies have demonstrated severe silvicultural problems associated with stagnant water in the soil. The studied stands represent different stages of forest management with a young 25-year-old oak (Sessile Oak (Quercus petraea) and Red oak (Q. robur)) plantation, a 170-year-old oak stand and a 95-year-old Norway Spruce (Picea abies) stand in second rotation. We determined the infiltration rates under saturated and near-saturated conditions with a hood-infiltrometer at the topsoil as well as the saturated hydraulic conductivity and water retention characteristic from undisturbed soil samples taken from the surface and 30 cm depth. We used the bi-modal Kosugi function to calculate the water retention characteristic and applied the normalized Young-Laplace equation to determine the pore size distribution of the soil samples. Our results show that the soils of the old stands have higher amounts of transmission pores, which lead to higher infiltration rates and conductance of water into the subsoil. Moreover, the air capacity under the old oak was highest at the surface and at 30 cm depth. There was also an observable difference between the spruce and oak regarding their contrasting root system architecture. Under the oak, higher hydraulic conductivities and air capacities were observed, which may indicate a higher and wider connected macropore system. Our results confirm other findings that higher infiltration rates due to higher abundance of macropores can be found in older forest stands. Our results also demonstrate that an adapted forest management is important, especially at sites affected by stagnant water conditions. However, more measurements are needed to expand the existing data base of soil hydraulic properties of forest soils in temperate climates.

The Effect of Variations in Drainage on Infiltration Rates in Pore Cylindrical Drainage

Inundation and floods are caused by a combination of factors including lower rain catchment areas, decreasing infiltration rates, and an uneven distribution of rainfall throughout the year, which all combine to create flooding and inundation issues. The alternative option is to install an efficient drainage system that is ecologically friendly, since in addition to its role of accommodating and draining water, it also has the additional purpose of absorbing water into the subsurface soil layer. A pore hole is created at the bottom of the drainage channel in order for the water to be absorbed. There was a desire to investigate the impact of soil texture on the rate of infiltration, therefore this research was conducted. Three kinds of soil were utilized as infiltration medium, namely sandy loam, loam, and clayey loam, all of which were found in the surrounding area. In addition, there are three variants of hole spacing, namely 16 cm, 32 cm, and 48 cm, as well as three variations of flow rate, namely 400 cm3/s, 1500 cm3/s, and 2500 cm3/s, among others. As a consequence of laboratory studies, it has been shown that the impact of changes in flow rate on infiltration discharge is inversely proportional to the flow rate, i.e., the higher the flow rate, the smaller the infiltration discharge that occurs. The reason for this is because it is influenced by the flow velocity

Effectiveness of ultrasound-guided cannulation of AVF on infiltration rates: A single center quality improvement study

Though ultrasonography is increasingly used throughout the spectrum of hemodialysis access, its role in outpatient dialysis units in the United States has been limited so far. This may, in part, be due to limited ultrasound exposure, knowledge and training of dialysis staff. We implemented a quality improvement initiative in our dialysis units to expand the use of ultrasound by our frontline dialysis staff to prospectively evaluate newly placed AVF and guide cannulation. This manuscript describes our experience and the impact of our protocol on infiltration rates in our outpatient HD units.