Tsung-Ren Peng

Erratum to “Temperature and hydrological variations of the urban environment in the Taipei metropolitan area, Taiwan”

In this study, the temperature, precipitation and groundwater level variations and changing patterns with varied time scales are presented for Taipei metropolitan area which consists of the capital city with neighboring counties. Along with the continuous city expansion during the past decades, global warming and heat island effect have generated perceivable negative impacts on environmental and reflect on the climatic and hydrological parameters. In addition to accelerating climate warming, hydrological extremity becomes more evident during the past decades and greatly elevates the risks of drought and floods in the study area. These observations in the Taipei metropolitan area support the common hypothesis that climate variability would increase as climate warms. The air temperature records, in conjunction with hydrological data, provide useful and invaluable information for the ongoing study of subsurface environmental changes resulting from nature and anthropogenic influences in Taipei metropolitan area. The continuing climatic warming and hydrological extremity would create observable impacts on the subsurface environment of Taipei metropolitan area and need to pursue in a fast and efficient pace.

Assessing groundwater sources and their association with reservoir water using stable hydrogen and oxygen isotopes: a case study of the Taipei Basin, northern Taiwan

The purpose of this isotopic study is to identify groundwater sources in Taipei Basin (TPB) and their association with water of the Feitsui Reservoir (FTR), northern Taiwan. To this end, water samples including precipitation, catchment surface water, TPB groundwater, FTR water, and catchment surface water of FTR were analyzed for stable hydrogen and oxygen isotope compositions (δ2H and δ18O). Isotopic results support previous reports that Dahan Stream and Xindian Stream waters are the major recharge sources of TPB groundwater. These recharge regions are located along the southern border of the TPB. Further, isotopic evidence finds that water from the southern hills catchment area of the TPB also recharges TPB groundwater, and most importantly, indicates that TPB groundwater is highly related to FTR water. However, for caution’s sake, future comprehensive study is needed to confirm hydrological connectivity between the FTR water and TPB groundwater.

Assessing the authenticity of commercial deep-sea drinking water by chemical and isotopic approaches

This study combines stable isotopes and chemical elements with statistical principal component analysis (PCA) to assess the authenticity of bottled commercial drinking water desalinized from deep seawater in the Taiwan market. Isotopic results indicate that true bottled deep-sea drinking water (DSDW) exhibits about 0 ‰ for both δ2H and δ18O values, which are values similar to those of open seawater. By comparison, suspected counterfeit DSDW products display δ2H and δ18O values of around −51 ‰ and −8 ‰, respectively. These values are representative of terrestrial freshwater. In addition, suspected counterfeit DSDWs have δ and electrical conductivity values similar to a mixed water (MW) product that was manufactured by purifying terrestrial freshwater and adulterating this with small amounts of brine. Furthermore, PCA results indicate the chemical constitution of suspected DSDW products to be similar to the MW product which falls between purified terrestrial freshwater and desalinized open seawater. These similarities imply that suspected counterfeit DSDW products are manufactured in a similar manner to the declared MW product. This study demonstrates how combining knowledge of stable water isotopes and PCA can be used in assessing the authenticity of commercial DSDW products. The method should be of great interest to similar investigations elsewhere.

Oxygen and carbon isotopic records of mollusks in the Kuokang Shell Bed, Taiwan: implications and applications

Abstract Oxygen and carbon isotopic compositions have been determined in fossil molluscan shells from the Kuokang Shell Bed and in modern shells from coastal areas around Taiwan. Fossil mollusks have been well preserved, based on X-ray diffraction, stable isotopic data and their occurrence in the field. The stable isotopic data of fossil shells indicate that they lived in an open sea environment. Heavier oxygen and lighter carbon isotopic ratios of these fossils relative to modern counterparts around Taiwan indicate that these fossil mollusks grew in a glacial period, as supported by the 14C dating results. The calculated mean uplift rate for the Kuokang Shell Bed shows a lower rate compared to the eastern and southern parts of Taiwan and reflects a more stable, away-from-collision nature for western Taiwan.

Submarine groundwater discharge around Taiwan

A preliminary study shows that the submarine groundwater discharge (SGD) exists around Taiwan even though groundwater overdrawing on the island is serious. Fifteen of the 20 sites studied for major anions and cations recorded a clear SGD signal with freshwater outflow. A total of 278 salinity and major ion measurements were made. Sixteen nearly freshwater SGD (salinity⩽1.0) samples were obtained, providing strong and direct evidence for the existence of fresh meteoric groundwater entering the ocean from Taiwan. The total SGD flux is estimated to be 1.07×1010 t/a which is about 14% of the annual river output. The freshwater component of the SGD is 3.85×109 t which is about 5.2% of the annual river discharge in Taiwan. The collected SGD has a composition similar to seawater with an addition of Ca, CO3 and HCO3 due to dissolution of calcareous rocks. Some samples with high Cl/(Na+K) may indicate pollution.

Submarine Groundwater Discharge helps making nearshore waters heterotrophic

Submarine groundwater discharge (SGD) is the submarine seepage of all fluids from coastal sediments into the overlying coastal seas. It has been well documented that the SGD may contribute a great deal of allochthonous nutrients to the coastlines. It is, however, less known how much carbon enters the ocean via the SGD. Nutrients (NO3, NO2, NH4, PO4, SiO2), alkalinity and dissolved inorganic carbon (DIC) in the submarine groundwater were measured at 20 locations around Taiwan for the first time. The total N/P/Si yields from the SGD in Taiwan are respectively 3.28 ± 2.3 × 104, 2.6 ± 1.8 × 102 and 1.89 ± 1.33 × 104 mol/km2/a, compared with 9.5 ± 6.7 × 105 mol/km2/a for alkalinity and 8.8 ± 6.2 × 105 mol/km2/a for DIC. To compare with literature data, yields for the major estuary across the Taiwan Strait (Jiulong River) are comparable except for P which is extremely low. Primary production supported by these nutrient outflows is insufficient to compensate the DIC supplied by the SGD. As a result, the SGD helps making the coastal waters in Taiwan and Jiulong River heterotrophic.

Development of an isotopic stream index connecting physiographic characteristics of montane catchments

This study is to develop an isotopic catchment-effect index (CEI) connecting the physiographic characteristics of stream catchments. A CEI, describing the extent of difference in stable water isotopic compositions (δ values) between stream water and local precipitation at any given sampling site, can help in judging whether water resource management should be focused on upstream regions of streams or local hydrology issues. To establish the isotopic CEI, this study measured δ values of stream water and derived δ18 O of local precipitation based on regional isotopic altitude gradient at montane catchments of various sizes. Results indicate that the CEI is strongly related to catchment physiographic characteristics, such as length of main stream, mean area, mean elevation, perimeter, and slope. These characteristics are considered important indices of streamflow. Based on mathematical regression modeling describing the relationships between CEI and respective physiographic factors, CEI values can predict respective physiographic factors and vice versa. Moreover, according to the multiple equations derived in this study, catchments of larger size and steeper slope give elevated CEI values while greater stream length reduces the CEIs value. A greater CEI value indicates that local stream water is principally sourced from upstream reaches rather than contributions from local precipitation. In addition, CEI values are greater in winter than in summer resulting from monsoon effect. Consequently, this study establishes CEI as a useful descriptor of the physiographic characteristics of catchments.

Erratum to “Temperature and hydrological variations of the urban environment in the Taipei metropolitan area, Taiwan” [Science of the Total Environment 404 (2008) 393–400]

In this study, the temperature, precipitation and groundwater level variations and changing patterns with varied time scales are presented for Taipei metropolitan area which consists of the capital city with neighboring counties. Along with the continuous city expansion during the past decades, global warming and heat island effect have generated perceivable negative impacts on environmental and reflect on the climatic and hydrological parameters. In addition to accelerating climate warming, hydrological extremity becomes more evident during the past decades and greatly elevates the risks of drought and floods in the study area. These observations in the Taipei metropolitan area support the common hypothesis that climate variability would increase as climate warms. The air temperature records, in conjunction with hydrological data, provide useful and invaluable information for the ongoing study of subsurface environmental changes resulting from nature and anthropogenic influences in Taipei metropolitan area. The continuing climatic warming and hydrological extremity would create observable impacts on the subsurface environment of Taipei metropolitan area and need to pursue in a fast and efficient pace.