A five-year investigation of water quality and heavy metal mass flux of an industrially affected river.

This study investigated the water quality parameters (dissolved oxygen, electrical conductivity, salinity, pH, and temperature) and the mass flux of eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) in five years (2015-2019) of the Houjing River. The river flows through a heavily-industrialized zone in Kaohsiung City in southern Taiwan. The surface water was sampled 4 times per year from five sampling locations: upstream sites (H1 and H2), industrial wastewater discharge point sites (H3 and H4), and downstream (H5). Our findings show that the water quality parameters improved in the study period, especially dissolved oxygen. However, some parameters, such as electrical conductivity (mean = 1152.50 ± 414.21 µS cm-1), were still higher than the Taiwan water quality irrigation standards. The heavy metal pollution was investigated in the aspect of mass fluxes and sources contribution. The spatial variation of the total heavy metal mass flux increased gradually from upstream to downstream, with H5 having the highest total mass flux of 74.1 kg d-1. H2, located near an industrial zone, had a total mass flux of 33.7 kg d-1 and contributed to the most Ni, Cr, Pb, Zn, and Hg fluxes. This study indicates that the water quality improvements observed are still not enough to meet the regulations. Stricter enforcement is required as well as further investigation to identify any illegal pollution sources.

Assessment of heavy metal contamination and adverse biological effects of an industrially affected river.

One of the most industrially affected rivers in Taiwan, the Houjing River, was studied in this research. The water and sediment samples were collected at five locations to measure the concentration of eight metals (As, Cd, Cr, Cu, Hg, Pb, Ni, and Zn). In order to assess the heavy metal contamination and its adverse biological effect, the heavy metal pollution index (HPI), the degree of contamination index (DC), the contamination factor (CF), the index of geo-accumulation (Igeo), and hazard quotients (HQs) were employed. The results showed that the Houjing River's water and sediment were contaminated with heavy metals. The annually averaged values of HPI (128.3) and DC (21.3) indicate that the water is unsafe for potable use and the sediment contamination level is at considerable degree of contamination. CF and Igeo calculation show that Zn, Cu, and Cd are the three main metals contributing to heavy metal contamination in sediment. Evaluation of adverse biological effects suggests that Zn, Cu, and Ni are the major metals that cause adverse effects on organisms. This study provides an overview of the synergistic heavy metal contamination degree of the Houjing River and its adverse biological effects, which should be a reliable reference for future contamination control and management plans.

Bioaccumulation and potential sources of heavy metal contamination in fish species in Taiwan: assessment and possible human health implications.

In this study, tissues of five fish species prevalent in the Houjing River were analyzed for heavy metal concentrations. Results show concentrations of such metals to be much higher than internationally recommended standard limits (as determined by the WHO and FAO) and other similar studies. Heavy metal contamination of fish in the Houjing River is hence significant. High hazard and carcinogenic risk related to the Houjing River's fish was proven based on target hazard quotient (THQ) and target cancer risk (TR) estimations. In fact, four of the five species studied present THQ levels higher than 1, and seven TRs of zinc (Zn) and arsenic (As) are higher than 10-4. Despite lower estimated daily intake (EDI) of fish in the area (per recommended daily allowance guidelines), possible heavy metal bioaccumulations in fish stock pose a high health risk for human consumption. From our analyses, the highest bioaccumulation factor (BAF) estimated above 1000 was of Zn. Among the fish species studied, Oreochromis niloticus possesses the ability to accumulate copper (Cu) and Zn dramatically. Pearson's correlation matrix showed a positive correlation between Cu and As, attributed to multiple industrial activities along the river. Hierarchical cluster analysis of results based on sampling stations exhibits three clusters and may be linked to the type of industrial activities specific to that area. More intensive study is needed in order to further determine the toxic metals in fish. Reporting of contaminant levels must be compared with optimal health criteria guidelines. Our study, while showing the severity of heavy metal contamination in fish stock, calls for urgent, sustained, and targeted actions by both governmental authorities and the local scientific community-to help prevent and mitigate the situation and ensure the physical well-being of local inhabitants.