Field temperature performances of in-use permeable sidewalks and asphalt vehicle roads and the potential impacts on apparent temperature and land surface temperature.

Permeable pavements help reduce surface temperatures and have been widely implemented in urban areas. This study utilized an in-use permeable pavement sidewalk in front of a mass rapid transit station in the Taipei city center of Taiwan to determine the actual pavement surface temperature performance. A neighboring asphalt road and impervious pavement were also monitored. With a full year of continuous monitoring, the results showed that the temperature of permeable pavement was 3.7 °C lower than that of impervious pavement and 4.5 °C lower than that of asphalt pavement in the hot season. The frequent rainfall in spring resulted in the smallest temperature differences between the different pavement types. The cooling effects of permeable pavement differed at the different air temperatures. At air temperatures lower than 15 °C, the differences among pavement surface temperatures were noticeable. However, when the air temperature was higher than 35 °C, the surface temperature of permeable pavement was not different from that of impervious pavement and was greater than 55 °C. Field observations were carried out to determine the effects on the apparent temperature and the future surface temperature of climate change scenarios. The results showed that permeable pavement could reduce the average apparent temperature to near the air temperature, and asphalt pavement could increase the apparent temperature by 1.2 °C, assuming that the pavement temperature completely affects the air temperature. With the good prediction ability of the machine learning approach and 15 environmental factors, the preliminary prediction showed the projected surface temperature change in Taipei city in 2033. In the worst-case scenario, the average impervious pavement temperature is as high as 39.12 °C, whereas the average permeable pavement temperature is 32.50 °C.

Assessing wastewater pollution from outdoor night markets and its impacts on river quality.

Night markets are attractive tourist sites in Asian cities. However, the outdoor activities produce different types of pollutants. Air pollution and solid waste in night markets have received much attention, but wastewater pollution from night markets has rarely been examined. The untreated wastewater are discharged into roadside gutters and might contaminate receiving waterbodies. In this study, night markets in Taipei city, Taiwan, were surveyed to clarify the characteristics of wastewater. The sampled wastewater showed high levels of organic substances, oil and grease, and phosphorous but low levels of nitrogen compounds. In addition, the unit pollution loads in night market stalls were obtained. The BOD load of each stall in the night markets was 2,509 g/day, which is higher than the sewage emissions of 50 people. In order to know the impacts of night market wastewater on the receiving waterbody, a water quality model, the Water Quality Analysis Simulation Program (WASP), was used in the studied river, Keelung River. If night market wastewater could be collected (not discharged), the BOD concentration could be reduced by 9.8%, but the NH3-N and DO concentration could be reduced by less than 1%.

Field performance of 15 rain gardens in different cities in Taiwan.

Rain gardens are widely used for low impact development (LID) or as a nature-based solution (NbS). They help to reduce runoff, mitigate hot temperatures, create habitats for plants and insects, and beautify landscapes. Rain gardens are increasingly being established in urban areas. In Taiwan, the Ministry of Environment (MoE) initiated a rain garden project in Taipei city in 2018, and 15 rain gardens have since been constructed in different cities. These Taiwanese-style rain gardens contain an underground storage tank to collect the filtrated rainwater, which can be used for irrigation. Moreover, the 15 rain gardens are equipped with sensors to monitor temperature, rainfall, and underground water levels. The monitoring data were transmitted with Internet of Things (IoT) technology, enabling the capture and export of real-time values. The water retention, temperature mitigation, water quality, and ecological indices of the rain gardens were quantified using field data. The results from the young rain gardens (1-3 years) showed that nearly 100 % of the rainfall was retained onsite and did not flow out from the rain gardens; however, if the stored water was not used and the tanks were full, the rainwater from subsequent storms could not be stored, and the tanks overflowed. The surface temperatures of the rain garden and nearby impermeable pavement differed by an average of 2-4 °C. This difference exceeded 20 °C in summer at noon. The water in the underground storage tanks had very low levels of SS and BOD, with averages of 1.6 mg/L and 5.6 mg/L, respectively. However, the E. coli concentrations were high, and the average was 6283 CFU/100 mL; therefore, washing or drinking water is not recommended. The ecological indices, i.e., the Shannon and Simpson indices, demonstrated the good flora status of the rain gardens after one year. Although the weather differed by city, the performance of the rain gardens in terms of water retention, temperature mitigation, rainwater harvesting, and providing biological habitats was consistent. However, maintenance influences rain garden performance. If the stored water is not frequently used, the stored volume is reduced, and the stored water quality degrades.

A storm event-based approach to TMDL development.

It is vitally important to define the critical condition for a receiving water body in the total maximum daily load (TMDL) development process. One of the major disadvantages of using a continuous simulation approach is that there is no guarantee that the most critical condition will be covered within the subjectively selected representative hydrologic period, which is usually several years depending on the availability of data. Another limitation of the continuous simulation approach, compared to a design storm approach, is the lack of an estimate of the risk involved. Because of the above limitations, a storm event-based critical flow-storm (CFS) approach was previously developed to explicitly address the critical condition as a combination of a prescribed stream flow and a storm event of certain magnitude, both having a certain frequency of occurrence and when combined, would create a critical condition. The CFS approach was tested successfully in a TMDL study for Muddy Creek in Virginia. The present paper reports results of a comparative study on the applicability of the CFS approach in Taiwan. The Dy-yu creek watershed in northern Taiwan differs significantly from Muddy Creek in terms of climate, hydrology, terrain, and other characteristics. Results show that the critical condition for different watersheds might be also different, and that the CFS approach could clearly define that critical condition and should be considered as an alternative method for TMDL development to a continuous simulation approach.

Performance evaluation of a full-scale natural treatment system for nonpoint source and point source pollution removal.

This study presents a full-scale performance of a natural treatment system (NTS) facility in Taiwan with nearly 2 years of observations. The study site, composed of several treatment ponds in series, was designed primarily to reduce polluted stormwater runoff from tea gardens and partially to untreated domestic wastewater from nearby villages. Thus, both nonpoint source and point source pollution are treated in this system. From 28 field samplings in 2006-2007, the NTS site shows satisfactory treatment performance and the effluent water quality is significantly improved. Seven of the 28 sampling events are storm events (nonpoint source pollution) and the remainder are from regular monitoring (point source pollution). The average volume of influent and effluent is 533 CMD and 196 CMD, respectively. In order to determine the removal efficiency, several assessment measures are employed in an attempt to obtain unbiased conclusions. They are removal rate (RR), efficiency rate (ER), summation of loads (SOL), flux rate (FR), and effluent probability method (EPM). The average percent removal efficiency of NH(3)-N is 53.5-75.2% and of TP is 59.0-84.7%, in which the highest result is calculated by SOL method and the lowest rate is obtained from RR. In FR evaluation, larger treatment capacity for NH(3)-N than for TP is provided in the site and the average FR is respectively 0.230 g/m(2) day and 0.017 g/m(2) day. Of the methods examined, EPM is the only method capable of illustrating data distribution. Finally, recommendations on the usefulness of these measures are summarized to facilitate the understandings of NTS performance evaluations.

The measurement of dry deposition and surface runoff to quantify urban road pollution in Taipei, Taiwan.

Pollutants deposited on road surfaces and distributed in the environment are a source of nonpoint pollution. Field data are traditionally hard to collect from roads because of constant traffic. In this study, in cooperation with the traffic administration, the dry deposition on and road runoff from urban roads was measured in Taipei City and New Taipei City, Taiwan. The results showed that the dry deposition is 2.01-5.14 g/m(2) · day and 78-87% of these solids are in the 75-300 µm size range. The heavy metals in the dry deposited particles are mainly Fe, Zn, and Na, with average concentrations of 34,978, 1,519 and 1,502 ppm, respectively. Elevated express roads show the highest heavy metal concentrations. Not only the number of vehicles, but also the speed of the traffic should be considered as factors that influence road pollution, as high speeds may accelerate vehicle wear and deposit more heavy metals on road surfaces. In addition to dry deposition, the runoff and water quality was analyzed every five minutes during the first two hours of storm events to capture the properties of the first flush road runoff. The sample mean concentration (SMC) from three roads demonstrated that the first flush runoff had a high pollution content, notably for suspended solid (SS), chemical oxygen demand (COD), oil and grease, Pb, and Zn. Regular sweeping and onsite water treatment facilities are suggested to minimize the pollution from urban roads.

Developing a simplified river landscape assessment model: examples from the Chungkang and Touchien rivers, Taiwan.

Currently, river landscape evaluations cannot be conducted by the general public, due to their lack of professional training. However, consulting professionals is time consuming and costly. The research conducted addresses both problems by (1) developing suitable criteria for assessing river environments, and (2) formulating a strategy for using the proposed criteria, thereby creating an effective method for river management by non-professionals. This research was carried out, in accordance with Visual Resource Management theory, at 12 survey sites along the ChungKang River. The landscape quality sequences acquired were then evaluated using a revised and simplified assessment model. The same process was repeated on the Touchien River to verify its feasibility. This research developed both specific criteria as well a method for evaluating river landscapes, which can be employed by non-professional river project managers. Ultimately, the aim of this research is to develop and promote sustainable river resource management.

Phosphorus load reduction goals for Feitsui Reservoir Watershed, Taiwan.

The present paper describes an effort for developing the total maximum daily load (TMDL) for phosphorus and a load reduction strategy for the Feitsui Reservoir in Northern Taiwan. BASINS model was employed to estimate watershed pollutant loads from nonpoint sources (NPS) in the Feitsui Reservoir watershed. The BASINS model was calibrated using field data collected during a 2-year sampling period and then used to compute watershed pollutant loadings into the Feitsui Reservoir. The simulated results indicate that the average annual total phosphorus (TP) loading into the reservoir is 18,910 kg/year, which consists of non-point source loading of 16,003 kg/year, and point source loading of 2,907 kg/year. The Vollenweider mass balance model was used next to determine the degree of eutrophication under current pollutant loading and the load reduction needed to keep the reservoir from being eutrophic. It was estimated that Feitsui Reservoir can becoming of the oligotrophic state if the average annual TP loading is reduced by 37% or more. The results provide the basis on which an integrated control action plan for both point and nonpoint sources of pollution in the watershed can be developed.

Implementation of a best management practice (BMP) system for a clay mining facility in Taiwan.

The present paper describes the planning and implementation of a best management practice (BMP) system for a clay mining facility in Northern Taiwan. It is a challenge to plan and design BMPs for mitigating the impact of clay mining operations due to the fact that clay mining drainage typically contains very high concentrations of suspended solids (SS), Fe-ions, and [H+] concentrations. In the present study, a field monitoring effort was conducted to collect data for runoff quality and quantity from a clay mining area in Northern Taiwan. A BMP system including holding ponds connected in series was designed and implemented and its pollutant removal performance was assessed. The assessment was based on mass balance computations and an analysis of the relationship between BMP design parameters such as pond depth, detention time, surface loading rate, etc. and the pollutant removal efficiency. Field sampling results showed that the surface-loading rate is exponential related to the removing rate. The results provide the basis for a more comprehensive and efficient BMP implementation plan for clay mining operations.