Heavy Seasonal Rainfall Research Articles

Cascading Landslide: Kinematic and Finite Element Method Analysis through Remote Sensing Techniques

Cascading landslides are specific multi-hazard events in which a primary movement triggers successive landslide processes. Areas with dynamic and quickly changing environments are more prone to this type of phenomena. Both the kind and the evolution velocity of a landslide depends on the materials involved. Indeed, rockfalls are generated when rocks fall from a very steep slope, while debris flow and/or mudslides are generated by fine materials like silt and clay after strong water imbibition. These events can amplify the damage caused by the initial trigger and propagate instability along a slope, often resulting in significant environmental and societal impacts. The Morino-Rendinara cascading landslide, situated in the Ernici Mountains along the border of the Abruzzo and Lazio regions (Italy), serves as a notable example of the complexities and devastating consequences associated with such events. In March 2021, a substantial debris flow event obstructed the Liri River, marking the latest step in a series of landslide events. Conventional techniques such as geomorphological observations and geological surveys may not provide exhaustive information to explain the landslide phenomena in progress. For this reason, UAV image acquisition, InSAR interferometry, and pixel offset analysis can be used to improve the knowledge of the mechanism and kinematics of landslide events. In this work, the interferometric data ranged from 3 January 2020 to 24 March 2023, while the pixel offset data covered the period from 2016 to 2022. The choice of such an extensive data window provided comprehensive insight into the investigated events, including the possibility of identifying other unrecorded events and aiding in the development of more effective mitigation strategies. Furthermore, to supplement the analysis, a specific finite element method for slope stability analysis was used to reconstruct the deep geometry of the system, emphasizing the effect of groundwater-level flow on slope stability. All of the findings indicate that major landslide activities were concentrated during the heavy rainfall season, with movements ranging from several centimeters per year. These results were consistent with numerical analyses, which showed that the potential slip surface became significantly more unstable when the water table was elevated.

Velocity distribution and movement of multiple slow-moving landslides characterized by an optimized MTInSAR workflow

Slow-moving landslides can be found worldwide, exhibiting gradual movement over years to decades, with velocities ranging from millimeters to meters per year. However, slow-moving landslides can undergo transformation into rapid and catastrophic events, leading to severe damage to human society. Given the presence of >2500 pre-existing slow-moving landslides identified and cataloged using LiDAR bare ground data in Taiwan, it is crucial to efficiently assess their activity prior to the typhoon and heavy rainfall seasons. Therefore, a key research objective is to enhance the ability to detect landslide velocities and movements over large areas spanning tens of thousands of square kilometers. This study aims to establish a workflow that employs the multitemporal interferometric synthetic aperture radar (MTInSAR) technique for the detection and monitoring of multiple slow-moving landslides across wide regions. Specifically, we propose an optimized analysis package called “multi-snap2stamps,” based on the existing snap2stamps method, to generate interferograms for multiple regions simultaneously. Focusing on the analysis of nine pre-existing slow-moving landslides, with velocities <1.6 m/year (classified as very slow or extremely slow landslides according to established criteria), distributed across Taiwan with diverse terrain and geological conditions, this study investigates the characteristics of these deep-seated landslides using the proposed MTInSAR analysis workflow in both spatial and temporal domains. The results reveal that two slow-moving landslide sites exhibit significant seasonal signals in the time series, while seven sites do not display such signals. Additionally, the MTInSAR time series effectively captures accelerated movement in the Shiding-T001 landslide, which corresponds well with in situ inclinometer monitoring data. This study demonstrates the effective analysis of velocity distribution and movement characteristics of slow-moving landslides using the proposed MTInSAR workflow. Furthermore, it highlights the potential of this workflow for improving landslide motion detection over vast areas of interest in the future.

Detection of Common Bacterial And Viral Pathogens Causing Community Acquired Pneumonia Using Rt-pcr And Its Correlation with Some Clinical And Demographic Parameters

Dohuk city is hydrologically located in a relatively narrow watershed bounded by mountain ridges with heavy rainfall seasons. Due to its topographical characteristics and rapid urban development, the city is prone to floods during intense rainfall events or storms and in need of a proper storm water drainage system and flood control hydraulic structures for managing intense storm rainfalls, avoiding urban flooding, property loss, and most importantly human casualties. Nevertheless, the local civil engineers are in need of having up-to-date hydrological formulas, relationships, and information in order to be able to adequately design the flood control hydraulic structures. One of these important relationships is IDF curves which correlates the Intensity, Duration, and Frequency of an observed rainfall event. The authors have been able to develop updated IDF curves and empirical intensity formulas for Dohuk city by converting maximum annual rainfall readings for 21 consecutive years (2000-2020) into sub-daily rainfall records for durations of 10, 20, 30, 60, 120, 180, 360, 720, 1440 minutes with recurrence intervals of 2, 5, 10, 25, 50, 100 years using Gumbel and Log Pearson distribution (LPT III). The accuracy and reliability of the results were statistically confirmed through applying coefficient of determination with the value of (R2=1) and Goodness of fit test (Chi-square) with the confidence degree of (95%)

Mean age at menarche and climate variables on a global scale.

Cross-population variation in age at menarche is related to many factors. The purpose of this study was to examine climate variables in relation to mean age at menarche among 87 modern human populations. We hypothesized a later age at menarche among populations living in areas with high precipitation variability, heavy seasonal rainfall, and high temperatures year-round due to water-borne diseases and periods of resource scarcity. Using a comparative dataset, we examined geospatial distribution and climate variables in relation to age at menarche for 87 modern human populations. We found the strongest predictor of a later age at menarche was higher fertility followed by a later mean age at death. In addition, higher annual rainfall, higher precipitation seasonality, and lower annual mean temperature were moderate predictors of age at menarche. We propose that later ages at menarche in countries with high fertility may be a life-history strategy developed in response to climatic conditions that have resulted in higher immunological load. In these conditions, females may prioritize growth rather than reproduction. Shifts in climate and global population growth may change the future biological landscape of age at menarche.

Flood Risk Perception among the Inhabitants of a Flood-prone Area in Iran

Background: Misunderstanding of disaster hinders people from devoting enough attention to disaster preparedness programs. Flood is one of the main natural hazards in Iran. Objectives: The present study aimed to determine flood risk perception among residents of a flood-prone area in Iran in 2021. Methods: This cross-sectional study was conducted on 201 inhabitants of three villages along the Hesar-Golestan River in northeast Iran. A researcher-made questionnaire was used to assess their flood risk perception and opinions about the causes of the flood. Flood risk perception was assessed using ten questions with a 5-point Likert scale. Risk perception was calculated at three levels: low (scores 10 to 23), medium (scores 24 to 37), and high (scores 38 to 50). Multi-stage sampling technique was used for sampling. Results: The majority of participants (81%) had a moderate risk perception. The mean risk perception score was 30±5, which indicates a moderate risk perception. According to the participants, the three main causes of floods were environmental degradation and soil erosion, unplanned development and construction in flood-prone areas, and heavy seasonal rainfall, respectively. There was a significant relationship between gender and age with some opinions about the causes of floods. Conclusion: The risk perception of participants was at a moderate level. Low or moderate flood risk perception can lead to insufficient attention, inaction, or insufficient efforts to reduce the risk and increase preparedness for floods. Taking measures such as educating people about the causes and consequences of floods using appropriate and effective methods can help to manage disasters better.

The effects of unplanned land use and heavy seasonal rainfall on the storm-water drainage in Dhaka metropolitan city of Bangladesh

ABSTRACT The capital city of Bangladesh, Dhaka, faces several challenges including significant rainwater congestion. With the holistic depiction of the current status, this study quantified rainfall, estimated land cover change and analyzed the drainage system in the western part of Dhaka. Statistical analysis and logarithmic graph fitting methods were used to develop a strong correlation between short-duration and daily rainfall. Land cover maps from 1990 to 2020 were generated using supervised classification in ERDAS IMAGINE, and the future land cover was predicted using the Terrset software with the CA Markov method. This research found that the build-up region increased by about 70% during the last 30 years while about 15.64 km2 of wetland was encroached during the past 15 years leading to the failure of existing drainage network. The assessment of rainfall demonstrated that the extreme events aggravated the issue. Restoration of natural canals is required for activating proper drainage system in the city.

A multi-geophysical approach to assess potential sinkholes in an urban area

Sinkholes caused by natural or anthropogenic factors pose as potential safety hazards in urban areas. From April to May 2019, six consecutive ground collapses occurred in Beihuan New Village (Guigang City, China) that affected the livelihoods of residents and caused substantial economic losses. The present study aimed to investigate potential sinkhole areas and determine the formation mechanism of a series of ground collapses in Beihuan New Village using a combined drilling and multi-geophysical approach. Geophysical profiles collected using electrical resistivity tomography (ERT) and ground penetrating radar (GPR) revealed shallow geological structures, potential sinkholes, and karst fracture zones. We also drilled several shallow boreholes along the geophysical survey profiles to obtain accurate hydrogeological information. To precisely identify groundwater runoff zones, cross-hole electrical resistivity tomography (CHERT) surveys of deep boreholes were conducted to locate the initial boundaries of the target anomaly areas delineated using ERT and GPR. The results demonstrated that a combination of geophysical exploration and geological profile analysis could accurately delineate potential sinkholes in urban areas. The locations of sinkholes in the study area were consistent with subsurface karst and groundwater runoff zones inferred from our survey results. Additionally, comprehensive analysis indicated that a depleted groundwater table, heavy seasonal rainfall, and overlying soil characteristics were possibly responsible for sinkhole formation. These findings can assist in prevention of ground collapses in urban areas and mitigation of the damages caused by these collapses.

Mapping of Areas Vulnerable to Flash Floods by Means of Morphometric Analysis with Weighting Criteria Applied

Flash floods, produced by heavy seasonal rainfall and characterized by high speeds and destructive power, are among the most devastating natural phenomena and are capable of causing great destruction in very little time. In the absence of hydrological data, morphometric characterization can provide important information on preventive measures against flash floods. A priority categorization of hydrographic units in the Cañete River basin was carried out using morphometric analysis together with a weighted sum analysis (WSA) based on a statistical correlation matrix. The delineation of the drainage network was performed based on Digital Elevation Model (DEM) data from the Shuttle Radar Topography Mission (SRTM). The Cañete River basin was subdivided into 11 sub-basins, and 15 morphometric parameters were selected. The priority category (very high, high, and moderate) of each sub-basin was assigned according to the value of the composite factor obtained through WSA. The results of this analysis showed that 26.08% of the total area is under a very high flash flood risk (sub-basins 3, 9, and 11), 38.46% is under a high flash flood risk (sub-basins 5, 7, 8, and 10), and 35.45% is under a moderate flash flood risk. This study concludes that flash floods predominate in sub-basin 3 and that downstream areas present characteristics of river flooding (sub-basins 9 and 11).

Forest harvesting impacts on microclimate conditions and sediment transport activities in a humid periglacial environment

Abstract. Sediment transport activities in periglacial environments are controlled by microclimate conditions (i.e., air and ground temperatures, throughfall), which are highly affected by vegetation cover. Thus, there is the possibility that forest harvesting, the most dramatic change to vegetation cover in mountain areas, may severely impact sediment transport activities in periglacial areas (i.e., soil creep, dry ravel). In this study, we investigated changes in sediment transport activities following forest harvesting in steep artificial forests located in a humid periglacial area of the southern Japanese Alps. In the southern Japanese Alps, rainfall is abundant in summer and autumn, and winter air temperatures frequently rise above and fall below 0∘. Our monitoring by time lapse cameras revealed that gravitational transport processes (e.g., frost creep and dry ravel) dominate during the freeze–thaw season, while rainfall-induced processes (surface erosion and soil creep) occur during heavy rainfall seasons. Canopy removal by forest harvesting increased the winter diurnal ground surface temperature range from 2.7 to 15.9 ∘C. Forest harvesting also increased the diurnal range of net radiation and ground temperature, and decreased the duration of snow cover. Such changes in the microclimate conditions altered the type of winter soil creep from frost creep to diurnal needle-ice creep. Winter creep velocity of ground surface sediment in the harvested site (&gt; 2 mm day−1 on the days with frost heave) was significantly higher than that in the non-harvested site (generally &lt; 1 mm day−1). Meanwhile, sediment flux on the hillslopes, as observed by sediment traps, decreased in the harvested site. Branches of harvested trees left on the hillslopes captured sediment moving downslope. In addition, the growth of understories after harvesting possibly reduced surface erosion. Consequently, removal of the forest canopy by forest harvesting directly impacts the microclimate conditions (i.e., diurnal range of ground temperature and net radiation, duration of snow cover) and increases frequency and velocity of periglacial soil creep, while sediment flux on hillslopes is decreased by branches left on the hillslopes and recovery of understories. The impact of forest harvesting on sediment transport activity is seasonally variable in humid periglacial areas, because microclimate conditions relevant to both freeze–thaw processes and precipitation-induced processes control sediment transport.

Rainwater harvesting for multiple uses: a farm-scale case study

Rainwater harvesting (RWH) alternatives from runoff and roof collection were evaluated for implementation in a farm in subtropical Mexico. Groundwater extraction and bulk water purchase in tanker trucks were evaluated and compared to RWH. The main water uses included irrigation (trees and seasonal crops), domestic (showers and toilets), and semi-industrial (food processing and cleaning). For all uses, except tree irrigation, a disinfection system was included as part of the process. Financial and non-financial factors were considered in the evaluation. Heavy seasonal rainfall during hurricane/monsoon season (June–September) contrasted with extremely dry months (November–May). Large water storage requirements and extended detention time result from this seasonal rainfall phenomenon. The space available for construction of water storage facilities was constrained at the site of study. These factors must be accounted for in RWH systems that show marked discrepancies between the time of rainwater collection and its use. The financial assessment showed that a new groundwater well would cost less (US dollars per m3) compared to RWH alternatives. However, in situations where water rights are not available, or if groundwater extraction is charged to the user, implementation of RWH may be more feasible. Therefore, RWH systems must be evaluated case by case, particularly for those users that experience marked seasonal rainfall conditions.

A controlled monitoring study of simulated clandestine graves using 3D ground penetrating radar

ABSTRACTA controlled three‐dimesional ground penetrating radar monitoring study over simulated clandestine graves was conducted near Pretoria, South Africa, in which the detectability of graves as a function of post‐burial interval was assessed, as this is of particular interest to local forensic investigators. It was demonstrated that the site‐specific environmental parameter (a clay‐rich loamy soil with poor drainage) and heavy seasonal rainfall (as confirmed by ground‐penetrating‐radar‐derived soil moisture estimates) drastically compromised the long‐term grave detectability, especially when adopting a three‐dimensional depth slice analysis approach. It is also seen that the disturbed burial zone is the major contributor to the total grave anomaly rather than the buried body due to the combination of environmental parameters and the absence of buried artefacts. This paper also advocates the combined use of different data representations (two‐dimensional and three‐dimensional) to increase the likelihood of detecting subtle grave anomalies.

Leptospirosis: Updating the Global Picture of an Emerging Neglected Disease.

Leptospirosis is a zoonotic bacterial disease found predominantly in impoverished populations inhabiting developing countries with tropical climates. Global leptospirosis burden is significant; however, inadequate diagnosis has affected the awareness of the disease among the medical community. This issue of PLOS Neglected Tropical Diseases reports two studies commissioned by the Leptospirosis Burden Epidemiology Reference Group (LERG) of the World Health Organization (WHO) on evaluating the burden of leptospirosis and determinants of transmission, based on systematic reviews of currently available literature. The first and long-awaited paper, by Costa et al. [1], updates previously published estimates from 1999, which relied on national surveys of surveillance data from different parts of the world [2]. In the present study, leptospirosis is estimated to cause more than 1 million severe cases and approximately 60,000 deaths per year. The limitations of surveillance systems in low-income tropical countries likely contribute to an underestimation of its burden. This is the case for numerous countries in Africa, for example, where there is increasing evidence that leptospirosis accounts for a significant proportion of nonmalarial fever cases. The burden of leptospirosis is therefore comparable or even higher than some other important neglected tropical diseases, including visceral leishmaniasis, severe dengue, echinococcosis, and cysticercosis. In the second paper, by Mwachui et al. [3], an overview of risk factors for leptospirosis is presented. Leptospirosis is a complex disease with multiple modes of transmission, broad host range, a multitude of infecting serovars, nonspecific clinical manifestation, and difficult diagnosis. The authors found a high heterogeneity of risk factors among the selected studies, suggesting that epidemiological patterns are highly specific to the geo-climatic context. Water-associated exposures (recreational water activities in developed countries and floods and heavy seasonal rainfall in tropical countries) are the main risk factors. Other risk factors include, as expected, agricultural practices, contact with animals, and poor sanitation. The burden of leptospirosis appears to be mainly determined by the interaction of poverty, geography, and climate. Both papers emphasize the scarcity of data on the surveillance and epidemiology of leptospirosis, as well as a lack of consensus on definitions of cases and risk factors, study design, and adequate methods of data analysis. There is a need for new studies with stringent epidemiological and diagnostic criteria, especially in countries that are not investing in surveillance programs. Further progress in our understanding of the epidemiology should contribute to the development of effective intervention strategies to prevent and control outbreaks. This is the challenge the Global Leptospirosis Environmental Action Network (GLEAN) from the WHO and the Health and Climate Foundation has been tasked with, through an interdisciplinary One Health approach (http://www.glean-lepto.org). Also, Leptospirosis is an emerging disease because of the growing number of inhabitants residing in urban slums and increased frequency of extreme climatic events. Although not included among the 17 NTDs prioritized by WHO (http://www.who.int/neglected_diseases/diseases/en/), these two papers should contribute to raising awareness on leptospirosis as an important and emerging neglected tropical disease.

The new volumetric approach for field measurements of rill erosion

Erosion on agricultural soils in Czech Republic threats seriously their production and nonproduction functions. Erosion have devastating effect on fertile topsoil of agricultural soils, reduces thickness of soil profile and nutrients and humus content, deteriorate physical, chemical and biological properties of soil. At Brno University of Technology in Czech Republic was designed and realized equipment the soil erosion bridge, which allows soil surface profile measurement and quantifies volume of erosion rills, which can occur after heavy rainfall. The main objective was to develop a method for volumetric quantification of erosion rills during heavy rainfall season. Using new equipment soil surface profile was measured directly in field during 4 years (2007–2010). New equipment consists of three parts. The first equipment is a square frame with an inside dimension of 4 m2. The second equipment is removable profile, which serves for movement of soil erosion bridge. The third equipment is soil erosion bridge. The soil erosion bridge serves to volumetric quantification of rill erosion. The more effective way of data processing was developed. It was developed a software, by which it is possible automatically transfer rill surface profile to digital form. In South Moravian Region in Czech Republic was selected case study area with typical very steep sloped relief with loess soil. The measurement was carried out on research plots with a slope of more than 10%. More than 1300 cross sections of soil surface profile were measured using new type of soil erosion bridge. From these profiles it was possible to calculate volume of eroded soil from research plots. The results were always in excess of 100 t.ha–1.rok–1. This is a value many times higher than tolerated limit of soil loss in Czech Republic. Thanks to this new equipment, it is possible to quantify soil loss from plot threatened of water erosion. The advantage of this equipment is its using during vegetable season when soil surface is overgrown with vegetation and crops are higher growth.

Development and performance analysis of satellite communication system for real-time river monitoring

K-water uses its Koreasat No. 5-based communications network for remote acquisition and provision of hydrological information on rainfall, water levels, water quality, and warnings via its hydrological observation network. The satellite is greatly affected by the rainfall attenuation during heavy rainfall seasons and typhoons since it is using the Ku-band frequency. K-water used the site diversity (SD) technology and developed a duplexing system that involved the setup of its main hub station at its headquarters and its auxiliary hub station at Gunnam Dam located at 200 km away, to smoothly use its data during rainfall attenuation and satellite malfunctions. In this paper, we proposed an online monitoring SD system in the communications satellite equipment and manual/automatic switching algorithms. We examined the SD effects in the projected site to improve the stability and reliability of K-water’s hydrological communications satellite. Data reliability was found to be improved to 96.7% through the comparative study of the existing and SD systems, in which present data observation failure occurred in all 418 terminal stations, but proposed method occurred only in 14 terminals.

Socioeconomic impacts of floods and droughts in the middle Zambezi river basin

Purpose – The purpose of the paper is to analyse how floods and droughts affect communities' livelihood in the middle Zambezi river basin and coping mechanisms which households apply to counter the impact of floods and droughts. Design/methodology/approach – The method adopted was semi-structured interviews, focus group discussions and semi-structured questionnaires. Findings – Thematic analysis shows that the major issues affecting communities' livelihood in the middle Zambezi river basin are related to frequent floods and droughts. Floods are due to heavy seasonal rainfall which occurs at the peak of the rainfall season. As for droughts, the frequency of dry-spells of 20 days on average has been observed during the crop season. The impacts of floods and droughts in the district, notably in some wards such as Kanyemba, are the reduction of crop production, food shortages, reduction of agriculture derived income and erosion of social network. Households have responded to these impacts through a number of coping mechanisms including disposal of assets, labour migration, stream bank and floodplain cultivation, piecework, remittance, wild production and fishing. However, such coping mechanisms are short term and some of them are in conflict with the country's environmental laws. Originality/value – This paper reports a study on the first such finding related to socioeconomic impact of floods and droughts on households located in the middle Zambezi valley which is 500 km from Harare with a specific focus on traditional coping strategies in the face of disasters.

Clinico-hematological pattern of Malaria in Rajkot city.

Background: This study was done to correlate clinico-hematological pattern of Malaria infection, its relation with rainfall & various affiliated demographic profile in Rajkot district, Gujarat, India. This study was conducted at P.D.U. Government Medical College, Rajkot from year 2008 to 2011. Methods: Thick and thin peripheral blood smears were made from each patient with fever and chills and body temperature ≥ 37.5°C (on medicinal thermometer). The stained slides were examined microscopically for malaria parasites. All patients who were admitted in the clinical ward from year 2008 to 2012 with fever were considered for this study. Patients were registered specially by their residential location for demographic data and rainfall pattern was noted. Results: A direct relationship is observed between malaria infection transmission and average monthly rainfall. Two peaks of high parasite density were observed in September & October, each peak was coinciding with high rainfall pattern of rainy season. There was a positive and significant correlation between parasite density and rainfall and breeding places of mosquitoes, suggesting that malaria is more common during heavy rainfall season and with poor living standards. There is also a significant positive correlation between parasite density and body temperature. Conclusions: Our study proves that malarial infection has got direct relationship with average rainfall during monsoon. As well as water stagnation & accumulation plays a major role in mosquito breeding and subsequent spread of malaria. Poor sanitation in lower socioeconomic class has maximum number of malaria cases.

SWAT-based runoff and sediment simulation in a small watershed, the loessial hilly-gullied region of China: capabilities and challenges

Model calibration and validation are necessary before applying it for scenario assessment and watershed management. This study presented the methodology of evaluating Soil and Water Assessment Tool (SWAT) and tested the feasibility of SWAT on runoff and sediment load simulation in the Zhifanggou watershed located in hilly-gullied region of China. Daily runoff and sediment event data from 1998–2008 were used in this study; data from 1998–2003 were used for calibration and 2004–2008 for validation. The evaluation statistics for the daily runoff simulation showed that the model results were acceptable, but the model underestimated the runoff for high-flow events. For sediment load simulation, the SWAT performed well in capturing the trend of sediment load, while the model tended to underestimate sediment load during both the calibration and validation periods. The disparity between observed and simulated data most likely resulted from limitations of the existing SCS-CN and MUSLE methods in the model. This study indicated that the modification of SWAT components is needed to take rainfall intensity and its duration into account to enhance the model performance on peak flow and sediment load simulation during heavy rainfall season.

An engineered cover system for mine tailings using a hardpan layer: A solidification/stabilization method for layer and field performance evaluation

A cover system for mine tailings with a solidified layer (called an engineered hardpan) was developed in this study to reduce water infiltration, acid generation and sulfide oxidation. Hydrated lime and waterglass were used to produce calcium silicate, which can serve as a binder when constructing a hardpan layer. The compressive strength of each solidified/stabilized material was found to be sufficient in the lab, and the amounts of heavy metals were significantly reduced in chemical leaching tests. Various characteristics of tailings may affect the layer's mechanical strength early on, but a long curing period is capable of compensating for these effects. Heavy metals were stabilized as carbonate-bound phases and sulfide minerals were surrounded by calcium silicate matrix, thereby preventing further reaction. To evaluate the field performance of the system, a hardpan layer was installed on top of tailings on a pilot scale. Leachate with high salt content was generated in the tailings layer in the early stages of monitoring, but after approximately 6 months, the objective was achieved as the hardpan layer gradually stabilized. Notably, during the heavy rainfall season of the later monitoring stage, water infiltration was continuously prevented by the system.

Personal and indoor exposure to PM2.5 and polycyclic aromatic hydrocarbons in the southern highlands of Tanzania: a pilot-scale study

Personal and indoor exposure to PM(2.5) and polycyclic aromatic hydrocarbons (PAHs) were measured in households in the Njombe district of Tanzania. Cooking is conducted indoors in this region due to its high elevation, cool climate, and heavy seasonal rainfall. Kitchens are often poorly ventilated, resulting in high exposures to combustion-related pollutants. Sampling sites were selected to represent typical cooking practices across regional socio-economic divisions. These include the use of open wood fires, charcoal, a mix of charcoal and kerosene, and liquid petroleum gas (LPG) for cooking fuels. PM(2.5) average personal exposure was 14 μg/m(3) (±3, n = 3) for LPG, 88 μg/m(3) (±42, n = 3) for kerosene/charcoal mix, 588 μg/m(3) (±347, n = 3) for charcoal alone, and 1574 μg/m(3) (±287, n = 3) for open wood fires. Total PAH average personal exposures were less than 1 ng/m(3) (±1, n = 3) for LPG, 57 ng/m(3) (±16, n = 3) for kerosene/charcoal mix, 334 ng/m(3) (±57, n = 3) for charcoal alone, and 5040 ng/m(3) (±909, n = 3) for open wood fires. Benzo[a]pyrene equivalent exposures for US EPA's priority PAH pollutants were 0 for LPG, 8 ng/m(3) for kerosene/charcoal mix, 44 ng/m(3) for charcoal, and 767 ng/m(3) for open wood fire. Inhalable pollutants are present at unacceptably high levels, exceeding indoor air quality standards for all but LPG fuels. Relative results provide an exposure profile for rural East Africa and support the feasibility of conducting a larger scale smoke exposure campaign in the region. The use of "fuel efficient" wood stoves for the reduction of PM(2.5) and PAH exposure was measured in a local secondary school. Proper use of "fuel efficient" wood stoves reduced personal and indoor exposure to measured pollutants by more than 90%, supporting further investigation into the applicability of this technology to significantly improve indoor air quality.

A Case Study of the DAF-based Drinking Water Treatment Plant in Korea

Since 2003, a full-scale dissolved air flotation (DAF) process has been operated by the Korea Water Resources Corporation (K-Water) in the Songjeon drinking water treatment plant (SWTP). The SWPT was designed with an adaptable operation mode so that it is able to produce safe and stable drinking water, even when the raw water is in very poor condition. The adaptable operation mode is able to buffer the dramatic change in the characteristics of the raw water. During the service period of 2003 to 2006, the SWTP has shown a constantly sound performance for the treatment of high turbid water (64–430 NTU), yielding a significantly low level of turbidity (DAF treated water, 0.15 ∼ 1.16 NTU; anthracite filtered water, 0.02–0.09 NTU). In terms of the DAF process, this work focused on suggesting some practical solutions that would cope with several difficult problems that occurred in the DAF-based drinking water treatment plant. These problems included the unexpected high turbidity occurring during the heavy rainfall season, the scraper problem due to the shortage of feed water to the DAF process, and the increase of turbidity due to the use of powder activated carbon (PAC) prior to the DAF process. In addition, from a cost-effective perspective, the relationship between the recycle ratio and the operating cost was investigated in the DAF process under two different recycle ratio conditions.