CHAPTER 1 INTRODUCTION
1.5 Two green oyster investigation projects
Recently, there were two investigations in identifying the copper source for Hsianshan green oyster. In April 2006, Huang et al. took water and sediment samples from HSP and Keya stream for analyzing heavy metal concentrations (Huang et al., 2006). In addition, they also measured the heavy metal concentrations in oysters near Keya estuary for identifying the potential copper source in the Hsianshan oyster. Table 2 shows the relative distance from the confluence of Nanman creek to Keya stream or the locations of these 7 sampling points. The sampling point P is inside the 2nd period of HSP for which the samples are pretreatment wastewater mostly discharged from semiconductor manufacturing companies before entering the wastewater treatment plant of HSP. The location of N0 is right at the discharge point of the HSP at Nanman creek. The sampling point S is located at a municipal sewer in the eastern part of Hsinchu city where the municipal wastewater is going to enter the Keya stream. The sampling points Kd2 and Kd4 are located at Keya bridge and Shiangya bridge, respectively, which are both at the downstream of the Keya stream.
Note that these two bridges are situated at about 710 m and 8,900m, respectively,
from the downstream of the confluence of Nanman creek and Keya stream. The sampling point I is at the intertidal zone of Keya stream. The sampling point C is at the coastal area of Hsianshan. The water samples taken from those six sampling points were analyzed for 18 heavy metals, including Zn, Cu, Pb, Fe, Al, Mn, Cd, Sr, Cr, Ba, Ni, Ag, Sn, As, V, W, Ga, and Mo. The concentration data of those 18 heavy metals, called as Data Set 1 given in (Huang et al., 2006), are graphed in Fig. 3, showing that all the heavy metal concentrations are in ppb level and the Cu concentrations sampled at P, N0, S, Kd2, Kd4, and I are 20, 340, 5, 15, 10, and 12 ppm, respectively. The concentration data of Data Set 2 are graphed in Fig. 4, showing that the Cu concentrations sampled at P, N0, S, Kd2, Kd4, I and C are 4600, 1400, 200, 500, 300, 250 and 100, respectively.
Huang et al. pointed out that the concentrations of Zn, Cu, Fe, Al, Sr, Ni, Cd, Sn, W, Ga, and Mo at the N0, the discharge point of HSP, are higher than those at other sampling points (Huang et al., 2006). Particularly, the Cu concentration at N0 is several tens fold if compared with that at other sampling points, indicating that the HSP is the Cu source for water in the downstream of Keya stream (Huang et al., 2006).
They also found very high concentrations of Zn, Cu, Pb, Fe, Al, Sr, Ba, Ni, W, and Ga in the organs of oyster growing in the Hsianshan coast. In addition, the mean concentrations of Zn (2584 ppm), Cu (2366 ppm), Fe (1348 ppm) and Al (1883 ppm)
are especially high among those 18 heavy metals. Note that the concentrations of Cu in the sediment ranged from 70 to 275 ppm with an average of 170 ppm are also listed in Table 1. They mentioned that the Cu source of oyster should relate to the high Cu concentration discharged from HSP wastewater and the coastal sediment. In addition to the Cu concentration, they also mentioned that the concentrations of Zn, Fe, Al, Sr, Ni, W, and Ga are also high both in HSP wastewater and oyster, revealing some relationship between the HSP wastewater and contaminated oyster. However, they remarked that they did not have direct evidence to prove that that HSP is the source of heavy metals of the Hsianshan wetland contamination (Huang et al., 2006).
An investigation was also conducted for identifying the copper source of Hsianshan green oyster by the Bureau of Environmental Protection Hsinchu (BEPH) (2006).
The water samples were collected at 7 sampling points, Nu, N0, Nd,Ku, Kd1, Kd3, and Kd5 during the period of February to August, 2006 and analyzed for 6 chemical items including SS, DO, BOD, NH3-N, Cu, As. One additional sampling point Y located at Yuchegou creek was added and its water samples were taken from August to November, 2006. The purpose of adding this sampling point is to assess whether the HIP is a Cu source or not. The concentration data of those 6 chemical items for Data Sets 3 to 12 respectively taken from February to November in 2006 are given in Table 4. Figure 2 shows the sampling locations, where Nu, N0, Nd are at Nanman creek, Y
is at Yuchegou creek, and Ku, Kd1, Kd3, Kd5 are at Keya stream. The sampling points Nu and Nd are, respectively, located at the upstream and downstream of the discharge point of HSP wastewater treatment plant at Nanman creek. The Ku is at the upstream and Kd1, Kd3, Kd5 are at the downstream of the confluence of Nanman creek and Keya stream. Table 2 shows the relative distances of those 8 sampling points measured from the confluence of Nanman creek and Keya stream.
Most of the Cu concentrations in the sampling points listed in Table 3 are under the environmental standard of 0.03 mg/L in the regulation for protecting human health promulgated by Taiwan Environmental Protection Agency. The study of BEPH pointed out that the Cu concentrations at N0 and Nd are relatively and equally high if compared with those at Nu except in March and October, 2006. Table 3 shows that, the concentration of Cu at Kd1, which is indeed located right at the downstream of N0 and Nd, is generally higher than those of other the downstream sampling points. It is noticed that the Cu concentrations at Nu in March and October, at Ku in June and October, and at Y in November are relatively high. However, there are no industrial factories in the drainage basins located above the sampling points Nu and Ku. Those data may be caused by illegal dumping of chemical wastes which happened sometimes before in different rivers. The Cu concentration detected at Y reflects that the wastewater released from HIP sometime contains heavy metal. The study of
BEPH also mentioned that the Cu concentrations in oyster are higher in the winter and spring and lower in the summer as indicated in Table 1. Note that this study also estimates that the discharged Cu contained in the wastewater of the HSP to Nanman creek is about 1263 kg/yr (BEPH, 2006).