Canoeing is the most favorite recreational activity in several Taiwanese rivers. However, river water frequently contains elevated levels of pathogenic Escherichia coli, which has adverse effects on ...human health. This study adopted a quantitative microbial risk assessment to analyze seasonal risks to canoeists' health in the Dongshan River, Taiwan. First, river E. coli concentrations were statistically analyzed to determine the seasonal distributions. The exposure duration (ED) was determined by field observations. To propagate the parametric uncertainty, Monte Carlo simulation was employed to model the probability distributions of seasonal pathogenic E. coli levels, ingestion rates, and ED for athletes. Finally, the beta-Poisson dose-response model was implemented to determine seasonal health risks for canoeists. The study results indicated that the health risks in infection probability ranged from 0.5 × 10
to 8.8 × 10
illnesses/person/day for tourists and 1.2 × 10
to 7.7 × 10
illnesses/person/day for athletes. The health risks in the Lizejian Bridge area for tourists exceeded an acceptable level suggested by the U.S. Environmental Protection Agency, 8 × 10
illnesses/person/day, in spring for an ED of 2 h/day, and the health risks for tourists and athletes approached this level in spring and winter for an ED exceeding or equaling 1.5 h/day. According to sensitivity analysis, the geometric standard deviation of river E. coli levels was the most sensitive parameter affecting seasonal risks to canoeists' health. To protect canoeists' health, effluent sewer systems, best management practices, and total maximum daily loads should be promptly implemented in this watershed.
Groundwater nitrate-nitrogen contamination typically involves several natural and anthropogenic factors, including those related to hydrology, hydrogeology, topography, and land use (LU). ...DRASTIC-LU-based aquifer contamination vulnerability could be used to characterize the pollution potentials of groundwater nitrate-nitrogen and to determine groundwater protection zones. This study used regression kriging (RK) with environmental auxiliary information on DRASTIC-LU-based aquifer contamination vulnerability to investigate groundwater nitrate-nitrogen pollution in the Pingtung Plain of Taiwan. First, the relationship between groundwater nitrate-nitrogen pollution and assessments of aquifer contamination vulnerability was determined using stepwise multivariate linear regression (MLR). Subsequently, the residuals between the nitrate-nitrogen observations and MLR predictions were estimated by kriging techniques. Finally, the groundwater nitrate-nitrogen distributions were spatially analyzed using RK, ordinary kriging (OK), and MLR. The findings indicated that the land used for orchards and the medium- and coarse-sand fractions of vadose zones were associated with groundwater nitrate-nitrogen concentrations. The fertilizer used for orchards was identified as the primary source of groundwater nitrate-nitrogen pollution. The RK estimates could be used to analyze the characteristics of the pollution source for land used for orchards and exhibited high spatial variability and accuracy after residual correction. Moreover, RK had an excellent estimate ability for extreme data compared to MLR and OK. Correctly determining groundwater nitrate-nitrogen distributions using RK was useful for administering environmental resources and preventing public health hazards.
Rivers are an important urban water resource. This study adopted multivariate linear regression (MLR) and logistic regression (LR) with multiple thresholds to assess river fecal pollution in the ...Tamsui River watershed using auxiliary environmental data. First, environmental data between 2015 and 2017 on land use, antecedent precipitation, population density, sewerage infrastructure, and river water quality were obtained using geographic information systems and served as explanatory variables. River fecal coliforms (FC), the dependent variable, were also collected for the same period. Then, MLR was used to establish an overall prediction model after validation, and to determine significant factors influencing the level of river fecal pollution. Finally, after stratifying the fecal pollution as low, medium, and high levels, LR with multiple thresholds was employed to explore key factors affecting different FC pollution levels. The study results revealed that land use type and river water quality (other than FC) strongly affected river FC pollution. The discharge of household sewage and wastewater from urban areas was a major source of river FC pollution, particularly for low and medium pollution levels, while farmland land use was negatively correlated with the medium and high levels of river FC pollution in the highly urbanized watershed. Biochemical oxygen demand and suspended solids were highly correlated with medium and high pollution levels in river water.
Assessing aquifer vulnerability is crucial for preventing groundwater pollution. In this study, aquifer vulnerability to fecal coliform (FC) pollution was assessed using auxiliary environmental data ...in the Pingtung Plain, Taiwan. Moreover, key environmental factors inducing different fecal pollution levels were determined. First, 23 explanatory variables on land uses, population density, livestock and poultry densities, sanitary condition, antecedent precipitation, groundwater quality, aquifer characteristics, and subsurface hydrology were obtained using geographic information systems in 2014. As dependent variables, groundwater FCs were also simultaneously obtained. Then, multi-threshold logistic regression (LR) was adopted to model aquifer vulnerability assessment after cross validation. The thresholds of aquifer vulnerability causing risks of incidental ingestion were analyzed by risk assessment. Risks to human health were acceptable for a low-level threshold and exceeded the acceptable level for medium- and high-level thresholds when residents incidentally ingested FC-polluted groundwater. Finally, key environmental factors inducing low, medium, and high levels of groundwater FC pollution were characterized. The key environmental factors for the LR with low- and medium-level thresholds were sand and gravel soil textures of unsaturated aquifers and antecedent 3-day cumulative precipitation, and those for the LR with high-level thresholds were chicken farming, urban land use, and ratio of tap water use. Thus, the multi-threshold LR indicated that environmental factors must be ranked for assessing aquifer vulnerability.
Assessments of spatiotemporal fine particulate matter (PM
2.5
) concentrations are crucial for establishing risk maps and maintaining human health. This study spatiotemporally assessed PM
2.5
...concentrations in Taiwan by using multivariate indicator kriging (MVIK) according to current Taiwanese and US regulatory standards for annual average PM
2.5
concentrations (15 and 12 μg/m
3
, respectively). First, multivariate integration was implemented to analyze data on PM
2.5
concentrations for 2019–2021 and 2020–2022 because of no statistical difference of the 3-year PM
2.5
data. MVIK was then used for modeling probabilities according to the two standards. Finally, quantile estimates on the basis of the occurrence probabilities of analyzing PM
2.5
concentrations were employed to determine the optimal classifications for establishing risk maps according to the two PM
2.5
standards. The study results indicated that the multivariate integration of temporal PM
2.5
data in MVIK can effectively streamline the analytic process. The multivariate integration of 3-year PM
2.5
data was suitable for assessing the risk categories of the regulatory standards for annual average PM
2.5
. The greatest estimated difference between the 2019–2021 and 2020–2022 multivariate integrations was in the Northern and Chumiao air quality regions. Because many air quality regions were in the PM
2.5
categories of exceeding 12 μg/m
3
, the regulatory standard for annual average PM
2.5
of 12 μg/m
3
was inappropriate in Taiwan at this point in time according to assessing the 3-year spatiotemporal variability of PM
2.5
concentrations.
As a key component of direct methanol fuel cells (DMFCs), proton exchange membranes (PEMs) are required to be mechanically robust, methanol-resistant, and conductive to protons. In this work, a novel ...sulfonated poly(ether ether ketone) (SPEEK) impregnated poly(vinylidene fluoride) (PVDF) electrospun nanofiber membrane was prepared. To avoid the collapse of PVDF fiber framework by the solvent of SPEEK, we designed a SPEEK/solvent/nonsolvent ternary filling system through the cloud point titration curves. Meanwhile, polydopamine (PDA), an extraordinarily adhesive and hydrophilic material, was coated on the surface of PVDF nanofibers to further improve the interface bonding between SPEEK and PVDF. The introduction of PVDF nanofibers completely changed the rigidity of SPEEK thus achieving a 5.4-fold increase of toughness when compared with that of pure SPEEK at dry state. Notably, significantly improved methanol barrier ability was also obtained due to the tortuous methanol crossover pathways caused by the embedded PVDF nanofibers. In the DMFC tests, the ultra-low methanol permeability and relatively high proton conductivity of the obtained composite membrane made it could be operated with 5 M methanol fuel and showed a peak power density of 104.0 mW cm−2, which was higher than the values of 89.3 mW cm−2 (2 M methanol) and 84.0 mW cm−2 (5 M methanol) recorded with commercial Nafion 115 membrane.
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•A SPEEK/DMAc/H2O ternary system was used to impregnate PVDF electrospun nanofibers.•Providing a new way to design polymer filled electrospun fiber composite membranes.•High toughness and excellent methanol barrier ability were obtained.•Modification of PVDF by PDA created an ion transport bridge for proton conduction.•Better DMFC performance than that of commercial Nafion 115 membrane was obtained.
Urban rivers provide an excellent opportunity for water recreation. This study probabilistically assessed health risks associated with water recreation in urban rivers in the Bitan Scenic Area, ...Taiwan, by employing quantitative microbial risk assessment and disability-adjusted life years (DALYs). Moreover, the effects of urbanization on the health risks of river recreation induced by waterborne pathogenic Escherichia coli (E. coli) were investigated. First, data on river E. coli levels were collected in both the Bitan Scenic Area and the upstream river section, and model parameters were obtained through a questionnaire administered to river recreationists. Monte Carlo simulation was then employed to address parameter uncertainty. Finally, DALYs were calculated to quantify the cumulative effects in terms of potential life lost and years lived with disability. The results indicated that the 90 % confidence intervals for the disease burden (DB) were 0.2–74.1 × 10−6, 0.01–94.0 × 10−6, and 0.3–128.9 × 10−6 DALY per person per year (pppy) for canoeing, swimming, and fishing, respectively, in the Bitan Scenic Area. Furthermore, urbanization near the Bitan Scenic Area approximately doubled the DB risks to river recreationists in upstream rural areas. At the 95th percentile, the DB risks exceeded the tolerances recommended by the World Health Organization (1 × 10−6) or U.S. Environmental Protection Agency (1 × 10−4). The findings suggest that the simultaneous implementation of effluent sewer systems and best management practices can reduce health risks to river recreationists by at least half, reducing the DALY levels below 1 × 10−4 or even 1 × 10−5 pppy.
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•Risks of river recreationists for pathogenic E. coli are analyzed by QMRA and DALYs.•Effects of urbanization on health risks of river recreationists are investigated.•90 % CI ranges from 0.01 to 128.9 × 10−6 DALY pppy for canoeing, swimming and fishing.•The 95th percentiles of disease burden risks exceed 10−4 (U.S. EPA) or 10−6 (WHO).•Urbanization near the Bitan Scenic Area roughly doubles health risks in rural areas.
Low-cost biopolymer chitosan has received considerable attention in the field of anion exchange membranes (AEMs) because it can be easily quaternized and avoids the carcinogenic chloromethylation ...step. Simultaneously increasing the ionic conductivity and improving mechanical properties of quaternized chitosan (QCS) is key for its high-performance application. In this study, new composite AEMs consisting of QCS and functionalized carbon nanotubes (CNTs) were prepared. CNTs were coated with a thick silica layer onto which high-density quaternary ammonium groups were then grafted. The insulator silica coating effectively prohibits electron conduction among nanotubes and the grafted –NR3+ provides new OH− conductive sites. Incorporating 5 wt% functionalized CNTs into the matrix enhanced ionic conductivity to 42.7 mS cm−1 (80 °C) which was approximately 2 times higher than that of pure QCS. The effective dispersion of CNTs and appropriate interfacial bonding between nanofiller and QCS improved the mechanical properties of AEMs, including both the strength and toughness of the composite membranes. An alkaline direct methanol fuel cell equipped with the composite membrane (5% functionalized CNTs loading) produced an maximum power density of 80.8 mW cm−2 (60 °C), which was 57% higher than that of pure QCS (51.5 mW cm−2). This study broadens the application of natural polymers and provides a new way to design and fabricate composite AEMs with both improved mechanical properties and electrochemical performance.
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•CNTs were coated by silica and then quaternized to obtain OH− ion transport ability.•Quaternized silica coated CNTs were used as a multifunctional filler to modify QCS.•Enhanced mechanical property together with hydroxide conductivity were obtained.•Peak power density of the composite membrane was improved by 57%.
Because Taiwan is a subtropical island, many pleasure beaches are situated on its coast. However, according to long-term monitoring data, fecal contamination at Taiwanese coastal beaches frequently ...exceeds the U.S. Environmental Protection Agency (EPA) guidelines. To avoid public health hazards, mapping the spatial extent of this contamination is crucial. This study applied indicator kriging (IK) to probabilistically assess the water quality of bathing beaches on the Taiwanese coast. Moreover, because the discontinuity of the traditional Cartesian coordinate established on an island coastline is difficult for geostatistical estimates, this study proposed a novel kriging estimation approach to deal with this problem. First, a one-dimensional (1-D) cyclic coordinate system of the Taiwanese coast was established using primary and secondary coordinates at each beach site.
Escherichia coli (E. coli
) and enterococci concentrations at coastal beaches were converted into indicator variables according to the U.S. EPA guidelines. IK was then used to spatially model the occurrence probabilities that exceeded the U.S. EPA guidelines for
E. coli
and enterococci. Finally, the water quality of bathing beaches on the Taiwanese coast was classified on the basis of the estimated probabilities. The study results indicated that bathing on the central western, northeastern, and southeastern Taiwanese coasts poses a potential threat to human health caused by high levels of fecal contamination. Moreover, primary and secondary coordinates established at beach sites were capable of analyzing the spatial variability and kriging estimates of the 1-D cyclic coordinates along the coastline.
