Estimating the Background Nutrient Concentrations and Establishing the Nutrient Criteria for the Tamsui River with Reference Conditions
Date Issued
2012
Date
2012
Author(s)
Hsieh, Po-Yen
Abstract
Uniform regulative or classified standards for river nutrient concentrations, including “surface water classification and water quality standards of Taiwan EPA” as well as “Taiwan river pollution index” (RPI), are adopted for every river basin in Taiwan. However, these nutrient standards may not consider whether different basins need different nutrient standards because of distinct environmental attributes. This may lead to that the background nutrient concentraitions are lower than the concentrations of current standards. Therefore, in this study, the reference conditions of river nutrients will be established to provide authorities to determine the proper criteria or standards for protecting the water quality of the upstream Tamsui River. Meanwhile, the candidate criteria derived from this study will be compared to current Taiwan standards.
The USEPA proposed two statistical methods for developing nutrient criteria to States and Tribes. The first method identified the criterion as the 75th percentile of the frequency distribution of nutrient data from reference sites within a region. The second method used the 5th to 25th percentile of the frequency distribution from the general population of nutrient data. To evaluate the applicability in Taiwan of each method, data was assembled from the Taipei Water Management Office (TWMO) and the Taiwan EPA to create a nutrient general population. The data from TWMO in the Taipei Water Source Domain were provided as reference population. Data of the Tamsui River were extracted from the general population and compared to those of the reference sites according to each nutrient component. Furthermore, the land use of subwatersheds controlled by corresponding monitoring sites was examined by multiple linear regressions to verify the disturbance by human activities. Before the background concencentrations of nutrients are predicted, the analysis of variance (ANOVA) was conducted to find out the spatial variations of the nutrient concentrations in the Tamsui River Basin. The results of ANOVA would show whether the nutrient concentrations among 61 sites are significant different.
The results of multiple linear regressions indicate the predicted background concentrations of TP and NH3-N in the Tamsui River are 0.027 and 0.029 mg/L. The background TP concentration is higher than the Category A standard of Taiwan EPA, but the Category A standard is still acceptable for the Tamsui River because it is in the interval of candidate criteria. In addition, the background NH3-N concentration is far lower than two current standards. Based on the results of this study, the authorities can adjust the policy of controlling nutrients for the Tamsui River.
Subjects
The Tamsui River
Background concentrations
Reference conditions
Nutrient criteria
Analysis of Variance
Multiple linear regressions
Type
thesis
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