Kaoping River Research Articles

River dust-induced air pollution in a changing climate: A study of Taiwan's Choshui and Kaoping Rivers

This study investigates river dust episodes along the Choshui and Kaoping Rivers in Taiwan, focusing on their spatiotemporal distribution and correlation with hydrometeorological factors (temperature, precipitation, relative humidity, and wind speed). Using the Improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (ICEEMDAN) algorithm and time-dependent intrinsic correlation (TDIC) analysis, we identified significant annual and diurnal correlations between PM10 concentrations and these factors. The analysis revealed that wind speed at Lunbei station had a positive annual correlation with PM10, while other factors exhibited significant negative correlations. Seasonal variations in PM10 correlations with temperature, relative humidity, and wind speed were observed, aligning with the prevailing seasons of river dust episodes. Wind motion analysis highlighted diurnal associations with land-sea breezes and annual correlations with the winter monsoon. Specifically, the Choshui River's dust events coincided with the northeast monsoon, whereas the Kaoping River's events occurred during the northwest and southwest monsoons. The study also uncovered that downstream stations (Lunbei and Daliao) were more prone to severe dust events than upstream stations (Douliu and Pingtung). These findings enhance our understanding of the dynamics and environmental impacts of river dust episodes, providing valuable insights for air quality management and health risk mitigation.

Bacterial heavy metal resistance related to environmental conditions

Contaminated water bodies such as rivers provide reservoirs for bacterial resistance. This field study tested the water quality and the bacterial resistance to heavy metals of Qishan River water pollution. Wastewater discharged to environmental surface waters is a major pathway of heavy metals and heavy metal-resistant bacteria. Contaminated water bodies such as rivers provide reservoirs for bacterial resistance. This field study tested the water quality and bacterial resistance to heavy metals of Qishan River water pollution. Guided by our research hypothesis that an overall increase in downstream heavy metal resistance levels was following an increase in human settlements were eight sites sampled along the Qishan River. These were situated upstream and downstream to the confluence of the Qishan River with the Kaoping River. In the laboratory bacterial heavy metal resistance was bio-assayed by disk diffusion and micro-dilution with six widely used heavy metals. The comparison of bacterial resistance was among Qishan River upstream sites (sites 1–6) and downstream sites (sites 7–9). Multi-drug-resistant bacteria and co-resistance against heavy metals and antibacterials appeared at site 8. This research discusses the correlation between environmental factors, and antibacterial and heavy metal resistance. The results provide stakeholders and authorities responsible for environmental pollution with a reference for risk assessment and management of bacterial resistance.

Comparison of antibiotic-resistant Escherichia coli and extra-intestinal pathogenic E. coli from main river basins under different levels of the sewer system development

Antimicrobial-resistant Escherichia coli in the aquatic environments is considered a strong indicator of sewage or animal waste contamination and antibiotic pollution. Sewer construction and wastewater treatment plant (WWTP) infrastructure may serve as concentrated point sources of contamination of antibiotic-resistant bacteria and antibiotic resistance genes. In this study, we focused on the distribution of antimicrobial-resistant E. coli in two rivers with large drainage areas and different urbanisation levels. E. coli from Kaoping River with drainage mainly from livestock farming had higher resistance to antibiotics (e.g. penicillins, tetracyclines, phenicols, aminoglycosides, and sulpha drugs) and presented more positive detection of antibiotic-resistance genes (e.g. ampC, blaTEM, tetA, and cmlA1) than that from Tamsui River. In Kaoping River with a lower percentage of sewer construction nearby (0–30%) in contrast to a higher percentage of sewer construction (55–92%) in Tamsui River, antimicrobial-resistant E. coli distribution was related to livestock farming waste. In Tamsui River, antimicrobial resistant E. coli isolates were found more frequently in the downstream drainage area of WWTPs with secondary water treatment than that of WWTPs with tertiary water treatment. The Enterobacterial Repetitive Intergenic Consensus (ERIC) PCR showed that the fingerprinting group was significantly related to the sampling site (p < 0.01) and sampling date (p < 0.05). By utilising ERIC-PCR in conjunction with antibiotic susceptibility and antibiotic-resistance gene detection, the relationship among different strains of E. coli could be elucidated. Furthermore, we identified the presence of six extra-intestinal pathogenic E. coli isolates and antibiotic-resistant E. coli isolates near drinking water sources, posing a potential risk to public health through community transmission. In conclusion, this study identified environmental factors related to antibiotic-resistant bacteria and antibiotic-resistance gene contamination in rivers during urban development. The results facilitate the understanding of specific management of different waste streams across different urban areas. Periodic surveillance of the effects of WWTPs and livestock waste containing antibiotic-resistant bacteria and antibiotic-resistance genes on river contamination is necessary.

Riverine antibacterial resistance gradient determined by environmental factors.

Polluted waterbodies such as rivers provide a pathway or reservoir for bacterial resistance. We studied water quality and bacterial antibacterial resistance along the subtropical Qishan River in Taiwan as a case study of environmental resistance spread in a pristine rural area. Human settlement densities increased generally from pristine mountain sites to the more polluted lowlands. Accordingly, as a working hypothesis, we expected the antibacterial resistance level to increase downstream. We collected sediment samples from 8 stations along the Qishan river and where the Qishan river reaches the Kaoping river. The samples were processed in the lab for bacteriological and physicochemical analysis. Antibacterial resistance was tested with common antibacterial. A comparison was made among the sites where isolates began to occur at the upstream (sites 1-6) with the downstream, including site 7 (Qishan town), site 8 (wastewater treatment plant), and site 9 (Kaoping river). The results of multivariate analysis for bacteriological and physicochemical parameters showed increasing water pollution levels downstream of the Qishan river. Bacterial isolates including Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, Enterobacter sp., Acinetobacter sp., Staphylococcus spp., and Bacillus spp. were analyzed and tested in the study. Their percentage of occurrence varied at each site. The resistance level was determined from the growth inhibition zone diameter (disk diffusion) and the minimum inhibitory concentration (micro-dilution). The results indicated that antibacterial resistance was related to certain environmental factors. Besides, the usage pattern of different classes of antibacterial in different sections could alter trends of their resistance. Bacteria were found with increased resistance to antibacterial used in agriculture through the downstream sites. The WWTP discharging wastewater was demonstrated to be a hotspot of resistance in aquatic environments. In conclusion, bacterial resistance against antibacterial from the Qishan river has become a potential public health threat. This study could assist authorities by providing a reference for risk assessment and management of water quality in Kaohsiung city and southern Taiwan.

Hemimyzon yushanensis, a new species of balitorid fish (Teleostei: Baltiordae) from southern Taiwan

The new balitorid fish was collected in the Kaoping river basin from southern Taiwan. The new balitorid, Hemimyzon yushanensis n. sp. can be well distinguished from other congeneric species by following combination of features: (1) dorsal fin rays 3 + 8; pectoral fin rays 11-13 + 9-11 (total 22-23; modally 22); (2) lateral-line scales 69-72 (modally 70); predorsal scales 25-30 (26-27); (3) pelvic fin moderate large, extending to rear vertical of dorsal fin; (4) the position of anus with larger distance of pelvic rear tip to anus about 1.2-1.7 times of that of anus to anal fin origin; and (5) specific coloration: predrorsal region and head with rounded creamy yellow spots, pectoral and pelvic fins with several small whitish spots on greenish brown background. The morphological comparison of congeners and diagnostic key of Taiwanese species would be also provided in this paper.

Uranium isotopes in a subtropical mountainous river of Taiwan: Insight into physical and chemical weathering processes

The correlation between physical and chemical weathering in mountainous rivers is debatable. A reliable geochemical tracer for physical erosion and chemical weathering is necessary to obtain crucial information on the relationship between weathering processes and environmental changes on the Earth’s surface. Small mountainous rivers (SMRs) of Taiwan are characterized by extremely high physical and chemical weathering, and therefore, they provide the foremost natural laboratory for studying weathering processes in tectonically active high-standing islands. In this study, water samples collected from the Kaoping River, the largest river catchment in southern Taiwan, were analyzed for elemental concentrations, as well as for U and Li isotopes, to understand the weathering processes and to evaluate the use of the 234U/238U activity ratio, hereafter (234U/238U), as a probe for weathering. The average (234U/238U) of the Kaoping River is significantly higher than that of other rivers worldwide, and variations in (234U/238U) reflect the degree of physical and chemical weathering. The weathering environment corresponds to the weathering-limited regime, and the mountain area is a natural example of the kinetic-limited control on chemical weathering by intense physical erosion. High physical erosion predominates in the mountainous region, which increases (234U/238U), relatively reduces U concentrations, and inhibits chemical weathering. The decreased (234U/238U) and increased Na/Li and δ7Li downstream clearly indicate enhanced chemical weathering in the alluvial plain. Our results demonstrate that dissolved (234U/238U) in the SMRs of Taiwan can reflect the relative contributions of physical and chemical weathering within the river catchment. The coupling between chemical weathering and physical erosion can be observed downstream and the relationship becomes less pertinent in the mountain area due to changes in weathering kinetics. A positive correlation between (234U/238U) and uplift rate in the Kaoping River suggests that the riverine (234U/238U) is mainly controlled by uplift-induced physical erosion, which may be influenced by landslide activities in the rapidly eroding mountainous river of Taiwan.

Mapping Interflow Potential and the Validation of Index-Overlay Weightings by Using Coupled Surface Water and Groundwater Flow Model

Interflow is an important water source contributing to river flow. It directly influences the near-surface water cycles for water resource management. This study focuses on assessing the interflow potential and quantifying the interflow in the downstream area along the Kaoping River in southern Taiwan. The interflow potential is first determined based on the modified index-overlay model, which employs the analytical hierarchy process (AHP) to calculate the ratings and weightings of the selected factors. The groundwater and surface water flow (GSFLOW) numerical model is then used to link the index-overlay model to quantify the interflow potential for practical applications. This study uses the Monte Carlo simulations to assess the influence of rainfall-induced variations on the interflow uncertainty in the study area. Results show that the high potential interflow zones are located in the high to middle elevation regions along the Kaoping River. Numerical simulations of the GSFLOW model show an interflow variation pattern that is similar to the interflow potential results obtained from the index-overlay model. The average interflow rates are approximately 3.5 × 104 (m3/d) in the high elevation zones and 2.0 × 104 (m3/d) near the coastal zones. The rainfall uncertainty strongly influences interflow rates in the wet seasons, especially the peaks of the storms or heavy rainfall events. Interflow rates are relatively stable in the dry seasons, indicating that interflow is a reliable water resource in the study area.

Levee Overtopping Risk Assessment under Climate Change Scenario in Kao-Ping River, Taiwan

With the growing concern about the failure risk of river embankments in a rapidly changing climate, this study aims to quantify the overtopping probability of river embankment in Kao-Ping River basin in southern Taiwan. A water level simulation model is calibrated and validated with historical typhoon events and the calibrated model is further used to assess overtopping risk in the future under a climate change scenario. A dynamic downscaled projection dataset, provided by Meteorological Research Institute (MRI) has been further downscaled to 5-km grids and bias-corrected with a quantile mapping method, is used to simulate the water level of Kao-Ping River in the future. Our results highlighted that the overtopping risk of Kao-Ping River increased by a factor of 5.7~8.0 by the end of the 21st century.

Three types of modern submarine canyons on the tectonically active continental margin offshore southwestern Taiwan

Six submarine canyons are distributed along the active margin off SW Taiwan. Using multi-beam bathymetric data and reflection seismic profiles to determine canyon head locations with respect to shelf edge, five of these canyons were classified into the following three types: 1. river-connected; 2. shelf-indenting; and 3. slope-confined. The remaining canyon was re-interpreted as a sea valley. Type 1 canyon, the Kaoping Canyon, is directly connected to the Kaoping River and supplied with terrestrial sediment. The canyon head segment tends to generate hyperpycnal flows during flooding, causing intense erosion of seafloor across the shelf and slope and forming a major sediment conduit. The Penghu, Kaohsiung and Fangliao canyons are of type 2 and incise into the shelf, forming a V-shaped head segment with abundant slumping features. Without continuous sediment supply from rivers, the canyon head receives sediments mainly from local slope failures on canyon walls and is unable to generate intense erosive sediment flows, resulting in an indentation into the shelf over a short distance. Oceanographic/hydrodynamic measurements close to the canyons are still not available for the region, despite they could shed light on the on-going sediment dynamics in the area. The Shoushan Canyon is a type 3 canyon characterized by limited sediment input from the Kaoping Shelf and weak canyon erosion, especially during sea-level highstands, resulting in a relatively straight canyon course confined to the upper slope. These submarine canyons share common regional tectonics, sea-level changes and climatic conditions. However, they evolved via local processes mainly controlled by sediment input directly related to head location, resulting in distinct morphologies and sizes. These canyons have remained active during the present-day sea-level highstand. Frequent earthquake and flooding events are the major triggering factors for sediment failures and generation of subsequent turbidity currents, resulting in substantial incision into the canyon. The results of the present study indicate that the SW Taiwan margin is characterized by canyons of type 1 and type 2 (n = 4) with only one type 3 canyon. This represents large percentages of type 1 and type 2 canyons compared to other regions of the world. Narrow shelf and abundant sediment supply are the two main controls for the presence of river-connecting and shelf-incising canyons on the active Taiwan margin.

Estimating landslide occurrence via small watershed method with relevance vector machine

The mechanism of landslide occurrence is complicated due to the dependency and nonlinear relationship of various physical factors. A promising prediction model, which can be used to locate the high-risk regions and a corresponding prevention strategy can be prepared to reduce the slide occurrence and its consequence, is therefore desired. To perform the landslide assessment for a large-scale slope, this study proposes to use the method of small watershed that is integrated with Relevance Vector Machine (RVM) to enhance the prediction accuracy. Effect of physiographic and hydrological factors such as slope steepness, dip slope ratio, landslide ratio, and cumulative rainfall are investigated. To estimate the occurrence of landslide, RVM first maps the aforementioned factors into a feature space using Gaussian radial basis function. A linear boundary, distinguishing landslide or not, is then obtained through the search of the optimal weights. To find these weights, a Bayesian theory-based optimization problem is formulated and solved by iteratively reweighted least squares algorithm and the Laplace approximation procedure. The proposed model is validated by the data collected from Kaoping River Basin. Results indicate that the proposed RVM-based small watershed approach possesses a prediction accuracy of 87.5%, which is better than those of using Support Vector Machine (SVM), Least-Square Support Vector Machine (LS-SVM), and logistic regression, providing authorities in their hazard alert system to minimize the life or property losses caused by the landslide.

Using Standardized Groundwater Index and Standardized Precipitation Index to Assess Drought Characteristics of the Kaoping River Basin, Taiwan

In the present study, long-term monitoring data were collected from the study area of the Kaoping River Basin, Taiwan. Specifically, data from six selected groundwater level stations and six precipitation stations in the vicinity were collected between 1997 and 2014. The standardized groundwater index (SGI) and standardized precipitation index (SPI) were then used to analyze the region’s drought characteristics. The results revealed that continuous droughts occurred in the river basin from 2003 to 2005. The trend for 2014 further indicated that the drought situation in the region would worsen in terms of severity. After calculation and analysis of the cross correlation function between the SGI and the SPI, a positive correlation was identified between the maximum cross correlation function (qmax) and the duration of the drought event. The larger the qmax value, the longer was the duration of the drought, and vice versa. The study also found that the qmax value varied with geographical locations: it was smaller for the various measuring stations located along the Qishan and Laonong rivers, but it tended to be larger for stations located beyond the Ailiao River. Thus, this study reckoned that if a drought event were to occur in the latter area in the future, its duration would be relatively longer. The findings of this study could also serve as future reference for the water resources management of the Kaoping River Basin.

New interpretation for the main sediment source of the rapidly deposited sediment drifts on the northern slope of the South China Sea

The slope of the northern South China Sea (SCS) is one of the world’s most active areas of modern marine sedimentary processes. A rapidly deposited sediment drift (RDSD) was identified on the slope near Dongsha Island. The sources of this body have been studied and discussed by several authors, but no consensus has been achieved. Based on multi-channel seismic profiles interpretation and data analysis of long-term observation of bottom currents, we identified that although the amounts of sediments input from the Pearl and Hanjing Rivers, and from Kao-ping and Tseng-Wen Rivers are large, considering the current situation of northern SCS, none of the Pearl River, the Hanjiang River, the Kao-ping River and the Tseng-Wen River can maintain the deposition pattern of the northern SCS margin as the single source, especially to maintain the supper high sedimentation rate at the RDSD area. The Miocene drape formation (MDF) calmly draped over an unconformity after rifting stage resulting in a relatively constant thickness of about 2000 m throughout the overall northern SCS continental margin, and followed by a standard configuration of a clinoform, the Pliocene formation and another clinoform of about another 700 m in total thickness. Due to Dongsha uplift since 3 Ma, roughly 1/2 of MDF and the N2 formation in the Dongsha area measures 150 km by 200 km were denudated resulting in an average annual denudation rate of 60 × 106 t/y. If these sediments were deposited on a slope region within an area measuring 100 km by 100 km, the sedimentation rate could reach 250 cm/ky. This is clearly an impressive new sediment source that has never been discussed before. Moreover, the RDSD is near the Dongsha Uplift and on the adjacent slope. We believe that this new sediment source should be the main contributor for the RDSD development.

Metallic characteristics of PM2.5 and PM2.5-10 for clustered Aeolian Dust Episodes occurred in an extensive fluvial basin during rainy season

ABSTRACTAeolian dust episodes (ADEs) have been an emergency disaster in the Kaoping River Valley during the rainy season (May-September), which can severely deteriorate ambient particulate air quality in the region surrounding the Kaoping River. Thus, this study aims to characterize the metallic fingerprint of Aeolian dust (AD) and investigate the effects of ADEs on ambient particulate air quality along the Kaoping River Valley. Four manual sampling sites adjacent to the riverside were selected to collect fine (PM2.5) and coarse (PM2.5–10) aerosol samples during and after the ADEs in the periods of six events. A total of 13 metallic elements were analyzed using an inductively coupled plasma-atomic emission spectrometer. With metallic elements analysis and nonparametric statistical methods of Wilcoxon rank-sum test and Kruskal-Wallis test, this study successfully derived the metallic indicators of ADEs. The mass ratios of crustal elements (Fe, Ca, or Al) to reference element (Cd) obtained during the ADEs were much higher than those obtained after the ADEs. High mass ratios of Fe/Cd, Ca/Cd, and Al/Cd in PM2.5-10 were observed on the influenced areas of ADEs. Among them, (Fe/Cd)2.5-10 was proven as the best indicator which can be applied to effectively validate the existence of ADEs and evaluate their influences on ambient air quality. Moreover, PM2.5 concentrations during the ADEs were 3-3.6 fold higher than those after the ADEs. PM2.5 should be a contributor to AD, even though the mass ratios of PM2.5/PM10 ranged from 0.05 to 0.20 during the ADEs. Our findings provide valuable information regarding the characteristics of the AD during the ADEs in the Kaoping River.Implications: Indicators of (Fe/Cd)2.5-10 are approximately applied to observe the effects of ADEs. Local governments could realize the mechanisms of S- and NW-type aeolian dust episodes (ADEs). They can cause deterioration in different ways for the regional air quality surrounding Kaoping River Valley. Residents who have been living in the influenced areas can take precautions to prevent damage from aeolian dust. Strategies for curbing ADEs must reduce the area of bare lands by artificial measures in the long period of the sunny days during the rainy season. Future research should examine physical conditions of topsoils and other chemical composition in aeolian dust.

The impact of physiographic factors upon the probability of slides occurrence: a case study from the Kaoping River Basin, Taiwan

ABSTRACTThis study has investigated the influence of physiographic factors upon the probability of slide occurrence in the Kaoping River Basin. According to previous literature, statistical tests, and physical mechanisms, three physiographic factors (slope steepness, the dip slope ratio, and the time-dependent landslide ratio) were significantly related to slide occurrence. These were combined with hydrological factors (cumulative rainfall) to establish an assessment model for estimating the probability of slide occurrence using logistic regression. The model’s overall accuracy in the training and validation stages was about 81%. Overall, 20 randomly selected historical rainfall events were employed for verification, including 10 events each with and without slide occurrence. The results showed that the model accuracy was approximately 80%, if the probability threshold Psh is set to be 0.5.This assessment model can assist in prediction of slide occurrence and the proposed subsequent engineering measures or vegetation restoration is often able to reduce the landslide ratio and the probability of slide occurrence. After landform changes, the model’s physiographic factors can be updated to adjust the rainfall threshold for slide occurrence. Given an appropriate cumulative rainfall and an acceptable risk of slide occurrence, the model can identify priority regions for slide prevention.

Effect of metals on zooplankton abundance and distribution in the coast of southwestern Taiwan.

Three transects were established along the southwestern coast of Taiwan; transects from north to south were respectively extended from the Kaohsiung Harbor, Kaoping River estuary, and Fangshan River estuary. Six metals including Pb, Cd, Cr, Cu, Zn, and Ni were analyzed in the zooplankton and seawater samples. A total of 24 groups of zooplankton were identified. Calanoid was the frequently collected group and accounted for greater than 40% of the relative abundance of zooplankton. Results showed that metal concentrations in seawater close to coast were higher than those in the outside of transect. The mean of metal concentrations in zooplankton followed the hierarchy: Zn > Cu > Pb > Ni > Cr > Cd. On the whole, metal concentrations in zooplankton from sampling sites in the coastal region were observed to be higher than those in the offshore region. The bioconcentration factor of zooplankton ranged within 103-105 for all studied metals and indicated that zooplankton in the seawater of southwestern Taiwan can accumulate metal even at background concentrations of metals. The value of diversity indices exhibited an increase in the distance to the coast, whereas the abundance showed no significant correlation with that. Consequently, the lowest mean abundance of zooplankton and the highest average metal bioaccumulation were found in transect outside Kaohsiung Harbor, representing that Kaohsiung Harbor has the contamination of anthropogenic metals that results in the impact on zooplankton.

Influences of natural and anthropogenic particles on ambient particulate air quality during typhoon season: From Bashi Channel to Kaoping River Valley

Aeolian dust episode (ADE) is an emerging disaster occurred from the bare lands of the Kaoping River Valley in southern Taiwan because of typhoons. Four manual sampling sites located along the Kaoping River Valley conducted to collect PM10 (aerodynamic diameter ≤ 10 μm) with high‐volume samplers during the ADE occurred by Typhoon Doksuri, and on regular days. Mass percentages of sea‐salt particles (SSs) in PM10 accounted for 5.47–8.91% on regular days and 11.66–14.05% in phase II. Average mass percentage of Ca2+ in phase I increased twice than those on regular days. Cl− deficit percentages were much lower during the ADE (7.37–14.13%) than on regular days (31.69–42.78%), indicating acidic particles mainly produced by chemical reactions of acidic aerosols with aeolian dust and SSs. Even alkaline aeolian dust is a dominant source of the ADE, the atmospheric particles are attributable to acidic particles in the air. Hence, anthropogenic sources play a key role for the worst air quality during typhoon season.

The association of Salmonella enterica from aquatic environmental and clinical samples in Taiwan

Salmonella is one of the most common pathogens of waterborne and foodborne disease-causing pathogens. In this study, we collected 172 surface water samples from Puzih River and Kaoping River between the years 2010 and 2011. Salmonella was detected in 31.7% (32/101) and 42.2% (30/71) of the samples from the two rivers, respectively. From these positive samples, 44 Salmonella isolates were obtained from these positive samples and were characterized using serotyping and pulsed-field gel electrophoresis (PFGE) genotyping. The isolates were found with 17 serovars and 32 PFGE patterns. Salmonella enterica Newport, Bareilly, Kedougou, Albany and subspecies IIIb 50:k:z were the five most common serovars in aquatic environmental Salmonella isolates. In addition, of the total clinical samples from Chiayi and Kaohsiung, 33.7% (60/178) Newport serovars were isolated. After conducting categorical analysis, we found that the serovar Newport was not uniformly distributed cross the cities. The serovar Newport was over-represented (p<0.001) among human isolates in Chiayi and Kaohsiung. To investigate the association between Salmonella isolates from aquatic environment and human samples, we compared the environmental PFGE patterns of the test samples with those of 2438 clinical isolates, obtained from 51 hospitals across the country between 2010 and 2011. Of the 32 PFGE genotypes of environmental isolates, 8 genotypes were identical to those of clinical samples. Serovar Newport isolates with PFGE patterns SNX.119 and SNX.183 obtained from Puzih River samples were also identified in human samples at a local hospital. These suggest that there is a link between environmental and human clinical Salmonella. Identification of Salmonella serovars and genotypes present in surface water provides an indication of the specific S. enterica serovars and genotypes present in humans. This is the first study to investigate the Salmonella serovars and genotypes present in aquatic environment and humans in Taiwan.

Assessment of susceptibility to rainfall-induced landslides using improved self-organizing linear output map, support vector machine, and logistic regression

Quantitative landslide susceptibility assessment is necessary for mitigating casualties, property damage, and economic loss. Identification of landslides and preparation of landslide susceptibility maps are crucial steps in landslide susceptibility assessment. Therefore, an optimal landslide susceptibility model is presented that is capable of producing accurate landslide susceptibility maps and assessing landslide susceptibility. To construct the optimal landslide susceptibility model, the effectiveness of the improved self-organizing linear output map (ISOLO), support vector machines (SVM) with four kernel functions (LN-SVM, PL-SVM, RBF-SVM, and SIG-SVM) and logistic regression (LR) was compared. Twelve landslide causative factors (namely, slope, slope aspect, elevation, curvature, profile curvature, plan curvature, slope length, topographic wetness index, distance to river, distance to road, distance to fault and annual maximum 24- and 48-h rainfalls) were used in this landslide susceptibility analysis. These models were applied to the Kaoping River basin in Southwestern Taiwan to assess its performance. Landslide inventory maps from 2008 to 2011 were collected. Data from the first three-year period were used for training and the remaining data was used for testing. The performance of the models was compared using accuracy and the area under the receiver operating characteristic curve as criteria. The results show that the RBF-SVM model outperformed the logistic regression in the study area. Using the RBF-SVM model, the landslide susceptibility under the annual 48-h maximum rainfall of various return periods were analyzed to assist local administrations and decision makers in disaster planning.

Comparative phylogeography of two codistributed endemic cyprinids in southeastern Taiwan

Two cyprinid fishes, Spinibarbus hollandi and Onychostoma alticorpus, are endemic to southeastern Taiwan. This study examined the phylogeography of these two codistributed primary freshwater fishes using mitochondrial DNA cytochrome b sequences (1140 bp) to search for general patterns in the effect of historical changes in southeastern Taiwan. In total, 135 specimens belonging to these two species were collected from five populations. These two codistributed species revealed similar genetic variation patterns. The genetic variation in both species was very low, and the geographical distribution of the genetic variation corresponded neither to the drainage structure nor to the geographical distances between the samples. The results of a statistical dispersal-vicariance analysis suggested that the ancestral populations of these two species were distributed in southern Taiwan before their dispersal. Our study suggests that the initial colonization occurred in the Kaoping River followed by eastern and northward dispersal. Our results also indicate that the Central Range in Taiwan did not act as a barrier to the dispersal of S. hollandi or O. alticorpus.

How Aeolian Dust Deteriorate Ambient Particulate Air Quality along an Expansive River Valley in Southern Taiwan? A Case Study of Typhoon Doksuri

Aeolian dust episodes (ADEs) frequently occurred at the bare lands of the riverbeds in Kaoping River are emerging disasters in Southern Taiwan in the past few years. However, their influences on ambient particulate air quality due to the outflow circulation of typhoons have not been addressed in such a subtropical region. This study aims to investigate the association between typhoons and ADEs and their influences on the ambient particulate air quality, which might occur in East Asia. Four sites along the Kaoping River were selected to collect PM10 with high-volume samplers during and after the ADE accompanying with Typhoon Doksuri on June 29, 2012. During the ADE, PM_(10) concentration rose as high as 30– 40 folds higher than those on regular days. Chemical composition of PM_(10) was further analyzed to verify several valuable indicators including the molar ratios of [Cl^-]/[Na^+] (0.95-1.02), the mass ratios of Fe/Cd (211.6-3957), and the mass ratios of OC/EC (1.18-1.35). Nevertheless, the chloride deficit phenomenon was not favorable during the ADE. Moreover, CMB receptor modeling results showed that aeolian dust and sea-salts were major contributors of PM_(10) during the ADE. Along the Kaoping River, the contribution of aeolian dust to PM_(10) ranged from 11.5 to 33.1% during the ADE, and reduced to 7.2–23.0% after the ADE. However, a small amount of finer aeolian dust could be still suspended in the ambient air after the ADE. Moreover, integrating SURFER software and WRF model was appropriate to locate the hot spots influenced by the ADE.