Multivariate Analyses of Potentially Toxic Elements along an Industrialized Urban River in Northern Taiwan

The Ker-Ya River flows through the high-tech industrial park and urban res-idential areas of Hsin-Chu in northern Taiwan. Major and trace element concentrations of waste effluents, river water, and sediment samples collected during 2017 along the Ker-Ya River were analyzed to elucidate the distribution pattern of potential pollutants. Principal component analyses were ap-plied, and four major contaminant associations were recognized: 1) Ce, Co, Fe, La, V, and Cr; 2) Cu and Ni associated with Hg, Ni, P, Ga, W, In, and Ti; 3) B, Li, Ba, Ca, and Ag; and 4) Sn with Zn, In, and Cd. All associations are considered to be mainly anthropogenic. Although the element associations recognized from the water samples are not exactly the same as those from the sediment samples but nevertheless, they are similar, suggesting that the short-term and long-term distribution patterns are consistent. The A association accounts for the most variance in the data and exhibits the widest distribution, suggesting the existence of contaminant sources in the upper and lower reaches, respectively. The sediments near the outlet of the city sewage plant also contain association A elements, signaling incomplete processing of the diverged waters sent to the plant at the river mouth. The B association (mainly Cu and Ni) appeared mainly in the upper and middle reaches, indicative of sources from industries in the upper reaches and the tributary Nan-Men Creek. The


Introduction
Despite efforts advanced in sewage treatment, monitoring and law enforcement, pollution caused by wastewaters discharged from domestic, agriculture, and industry remains a dire and challenging problem in many cities [1]- [9]. This is also the case in certain cities in Taiwan [10] [11]. This paper uses a multivariate statistical method to investigate the element data of river water and surface sediment samples to determine contaminant distribution patterns and elucidate possible pollution sources in a densely populated, highly industrialized area, Hsin-Chu, in northern Taiwan.
Hsin-Chu has been developed as a major high-tech industrial area since 1980, and the related information technology (IT) industrial complex, also known as "Eastern Silicon Valley", is clustered in the Hsinchu Science Park (HSP) and its environs. The Ker-Ya River is the single major river flowing through the industrialized urban complex. In the watershed, there exist more than 500 manufacturing factors, including plants of electroplating, computer chip manufacturing, packaging assembly, rubber processing, paper and pulp mills, glass factories, chemical plants, cement factories, biotechnology companies, fertilizer manufacturing, printing, dyeing, and metal processing. Indeed, more than 400 plants are located inside of the HSP, located to the north of the Ker-Ya River in its middle reaches. Along the upper reaches remain farms, possibly discharging agricultural wastes too.
Ever since the establishment of the HSP in 1980, waste management, regular monitoring, and law enforcement have been implemented. Yet, several major environmental events occurred in the late 1990s, including the pungent smell of the river water, abnormal statistics of blood test results of inhabitants in neighboring communities, and repetitive dead fish incidents in the Ker-Ya River [12], [13]. Currently, the Ker-Ya River itself is still the major receiving water body in the city of different kinds of contaminants discharged from various sources, including agricultural wastewater in the upper reaches, industrial and municipal runoff from the middle and lower reaches in the downtown area, and probably occasional illegal dumping of untreated wastewater from dispersed industries.
Among the numerous pollutants, anthropogenic metals are highly mobile and bioavailable, and therefore can impart adverse effects on aquatic biota and human beings [14] [15].
Beginning from 2015, as a measure designed to improve the water quality of the Ker-Ya River running through the urban area of Hsin-Chu, the waters of small tributary creeks were intercepted at four sites before they enter the main

Study Area and Sampling Design
The Ker-Ya River originates from the hilly Bao-Shan County to the east of the    (Table 2) and 25 elements (Table 3) from sediments, respectively, were retained for the final eigenfunction and eigenvalue calculation, and the final resolved PCA patterns were eventually stabilized.

PCA Results of Sediment Samples
Four PCs were retained for the sediment samples, accounting for 85.6% of the variance in total (  [15]. Generally, the water samples constitute a snap-shot of chemicals in the water, while surface sediments retain longer-term records.

Contaminant Association A-PC1
In the water sample set, the elements with high positive correlation coefficients     Table 4), suggesting that there were sources in the upper reach and tributary creeks other than Glass Factory B. Consistently, sediment samples also signal the occurrence of association A in S14 (River Mouth), S13 (entrance of Yeu-Che Creek), and S04 (entrance of Nan-Men Creek) ( Figure 2, Figure 4, and Table   4). Overall, elements of assemblage A were present in water and surface sedi-

Contaminant Association B-PC2
The second PC of water samples, accounting for 19.9% of the variance, is basically an association of Ni, Cu, P, Hg, W, and As (in descending order of correlation coefficients, see Table 2). Only one water sample (W27 collected on 2017/10/11 at Zhong-Shan Bridge, Figure 3) contains a high concentration of these elements (Table 2, Figure 3). For sediments, association B is characterized by Br, Cu, Ga, In, Ni, and Ti (Table 4). Only Cu and Ni are common in the contaminant associations of water and sediments (Table 4). W27 (Zhong-Shan Bridge (E2) 10/11) and S17 (Phoenix Bridge (B) 10/11) are the two samples showing high scores (Figure 3 and Figure 4).

Contaminant Association C-PC3
The third PC represents an association of Li, Ba, B, and Ca (Tables 2-4) for both water and sediment sets. These elements are characteristic of the original waste water (W4, W5) of the Paper Mill ( Figure 5). They were also present in the surface sediment S07 at the entrance of Paper Mill effluences ( Figure 6). We consider that this association of elements is closely related to the Paper Mill (Table   4).

Contaminant Association D-PC4
The PC4 recognized from water samples has a high correlation with In and Sn, but the sediment's PC4 is correlated mainly with Zn and Cd (Table 4). According to the loading matrices, PC4 is not a well-defined association, and is only roughly correlated with Zn, Cd, In, and Sn. Those elements occurred primarily    in the top area of the middle reaches in both water and surface sediments (W24 and W25 in Figure 7; S04 in Figure 8, see Figure 2 for their locations).

Potential Pollutants and Pollution Sources
Samples exhibiting high positive or negative scores of the four principal components are listed in Figure 9. A total of 21 elements that exhibit high correlation values with the associated principal components are evaluated against the standard high-limit concentrations prescribed by the drinking water guidelines issued     Although four major associations of contaminants were recognized, a close examination of the element concentrations in the water and sediments demonstrates that the Ker-Ya River is not heavily polluted, because only As in the W27 sample (0.0148 mg/L) slightly exceeded the limit value (0.01 mg/L) of drinking water quality standards issued by the Taiwan Environmental Protection Administration (TEPA). In addition, relatively high concentrations of Fe (ranging from 0.58 to 34.50 mg/L) in all of the listed water samples in Figure 9 may cause aesthetic, cosmetic, and/or technical effects when in use, but are not considered to be seriously polluted.

Funding Information
The initial sampling and analyses were funded by the Taiwan

Availability of Data
All of the analyzed data were taken from the report entitled "Sediment Charac-