1:45 PM - 3:15 PM
[O11-P108] Survey of spring water systems on Kozu Island, Tokyo
Keywords:Kozu Island, spring water, water quality, water system
[Background and subject]
Kozu Island is said to be rich in groundwater. All water supplies to homes and facilities on the island are powered by groundwater. There are also two springs that have been selected as two of the 57 best springs in Tokyo, and their locations are promoted as tourist attractions. The point about the abundance of water on Kozu Island can also be read from the myth of water distribution on the seven Izu islands. In this myth, it is said that the gods of the seven Izu islands, who were suffering from a water shortage, gathered on Kozu Island to discuss how to distribute the water. There are currently several rivers within Kozu Island, of which those on the eastern side of the island have water constantly flowing through them. In this study, the water quality of springs and surface water was investigated to examine the characteristics of the water at each site and to discuss the water system.
[Methods]
In this study, air temperature, water temperature and pH were measured at a total of 13 different sites on Kozu Island on the 4th, 11th and 19th October and 22nd, 29th November and 9th March.[Table 1] Initially, well water test kits were used to check five parameters: pH, iron, total hardness, Chemical Oxygen Demand [COD] and nitrite. The electrical conductivity was also measured using an electrical conductometer.
[Result]
All sites had iron below 0.05 mg/L and nitrite below 0.02 mg/L, with no differences in values between sites for these two parameters. The three parameters that varied by location and the graph and figure of electrical conductivity are shown below. However, the COD at site ⑩ and electrical conductivity at site ⑤ are missing.
The pH was above 7.2 at eight of the 13 sites, between 6.8 and 7.0 at three sites and below 6.8 at two sites.
Total hardness was above 60 mg/L at two of the 13 sites, between 40 mg/L and 60 mg/L at three sites and below 40 mg/L at eight sites.
The COD was between 2.0 mg/L and 4.0 mg/L at five of the 12 sites, between 4.0 mg/L and 6.0 mg/L at four sites and above 6.0 mg/L at three sites.
Electrical conductivity was between 100 µS/cm and 200 µS/cm at seven of the 12 sites, between 300 µS/cm and 400 µS/cm at two sites and above 400 µS/cm at three sites.
[Discussion]
The figure1,2 and 3 show a similar trend for values ⑥, ⑦ and ⑧ on the north to north-west slopes of Mt. Tenjo, the highest peak on Kozu Island, and for values at site ⑪ and site ⑫ collected near Nagahama coast, located on the north-west side of Mt. Tenjo. This suggests that the water at the above locations, north to north-west of Mt.Tenjo and near the Nagahama coast, respectively, is of similar quality, and therefore can be considered as closed water systems.
For site ① on the west side of Mt. Tenjo, the total hardness is higher than for site ②, which is closer to the site ① in Fig. 3.It can be read that both site ① and site ② show higher electrical conductivity than other sites that are more affected by the salinity contained in the sea breeze. Given the location of the spring and site ②, it can be assumed that the high total hardness of the water at site ① is due to the spring being strongly influenced by geological factors.
For sites ③, ⑨ and ⑩, relatively high values of electrical conductivity can be read from the graph 4.The proximity of these sites to the coast suggests that they were strongly affected by the salinity contained in the sea breeze.
Higher COD and lower pH were observed at sites ⑥,⑦ and ⑧ on the north to north-west slopes of Mt. Tenjo than at other sites. This suggests that rainwater infiltrating into the slopes at site ⑥, ⑦ and ⑧ gushed onto the slopes in a relatively short period of time.
[Agenda for the future]
In this study, the parameters for which differences between sites were observed and discussed in relation to topographical characteristics, but it was not possible to conduct experiments to determine what the causal agents were.
Future research should investigate which substances are responsible for the differences in water quality and thus clarify factors that were unclear from the results of this study alone.
Kozu Island is said to be rich in groundwater. All water supplies to homes and facilities on the island are powered by groundwater. There are also two springs that have been selected as two of the 57 best springs in Tokyo, and their locations are promoted as tourist attractions. The point about the abundance of water on Kozu Island can also be read from the myth of water distribution on the seven Izu islands. In this myth, it is said that the gods of the seven Izu islands, who were suffering from a water shortage, gathered on Kozu Island to discuss how to distribute the water. There are currently several rivers within Kozu Island, of which those on the eastern side of the island have water constantly flowing through them. In this study, the water quality of springs and surface water was investigated to examine the characteristics of the water at each site and to discuss the water system.
[Methods]
In this study, air temperature, water temperature and pH were measured at a total of 13 different sites on Kozu Island on the 4th, 11th and 19th October and 22nd, 29th November and 9th March.[Table 1] Initially, well water test kits were used to check five parameters: pH, iron, total hardness, Chemical Oxygen Demand [COD] and nitrite. The electrical conductivity was also measured using an electrical conductometer.
[Result]
All sites had iron below 0.05 mg/L and nitrite below 0.02 mg/L, with no differences in values between sites for these two parameters. The three parameters that varied by location and the graph and figure of electrical conductivity are shown below. However, the COD at site ⑩ and electrical conductivity at site ⑤ are missing.
The pH was above 7.2 at eight of the 13 sites, between 6.8 and 7.0 at three sites and below 6.8 at two sites.
Total hardness was above 60 mg/L at two of the 13 sites, between 40 mg/L and 60 mg/L at three sites and below 40 mg/L at eight sites.
The COD was between 2.0 mg/L and 4.0 mg/L at five of the 12 sites, between 4.0 mg/L and 6.0 mg/L at four sites and above 6.0 mg/L at three sites.
Electrical conductivity was between 100 µS/cm and 200 µS/cm at seven of the 12 sites, between 300 µS/cm and 400 µS/cm at two sites and above 400 µS/cm at three sites.
[Discussion]
The figure1,2 and 3 show a similar trend for values ⑥, ⑦ and ⑧ on the north to north-west slopes of Mt. Tenjo, the highest peak on Kozu Island, and for values at site ⑪ and site ⑫ collected near Nagahama coast, located on the north-west side of Mt. Tenjo. This suggests that the water at the above locations, north to north-west of Mt.Tenjo and near the Nagahama coast, respectively, is of similar quality, and therefore can be considered as closed water systems.
For site ① on the west side of Mt. Tenjo, the total hardness is higher than for site ②, which is closer to the site ① in Fig. 3.It can be read that both site ① and site ② show higher electrical conductivity than other sites that are more affected by the salinity contained in the sea breeze. Given the location of the spring and site ②, it can be assumed that the high total hardness of the water at site ① is due to the spring being strongly influenced by geological factors.
For sites ③, ⑨ and ⑩, relatively high values of electrical conductivity can be read from the graph 4.The proximity of these sites to the coast suggests that they were strongly affected by the salinity contained in the sea breeze.
Higher COD and lower pH were observed at sites ⑥,⑦ and ⑧ on the north to north-west slopes of Mt. Tenjo than at other sites. This suggests that rainwater infiltrating into the slopes at site ⑥, ⑦ and ⑧ gushed onto the slopes in a relatively short period of time.
[Agenda for the future]
In this study, the parameters for which differences between sites were observed and discussed in relation to topographical characteristics, but it was not possible to conduct experiments to determine what the causal agents were.
Future research should investigate which substances are responsible for the differences in water quality and thus clarify factors that were unclear from the results of this study alone.