○ Water quality evaluation index WQI grade 2 or higher → Healthy sea with almost no external pollutants
○ Tidal flat organic matter and heavy metal contamination are good; continuous observation of some sites required

Gyeonggi Province announced on October 20 that, through a pollution survey of its seawater and tidal flats undertaken over the past three years, seawater quality has been found to be above grade 2 while organic matter and heavy metal pollution of tidal flats was deemed positive.

The Gyeonggi-do Maritime & Fisheries Research Institute examined the Water Quality Index and the Cleanup Index of Eutrophication (CIET) of 10 sea and tidal flat areas in the cities of Hwaseong, Ansan, and Siheung so as to assess the province’s water quality and tidal flat organic matter contamination.

The water quality evaluation index ranks water quality by dividing it into grades 1 to 5 based on five criteria: dissolved oxygen concentrations, phytoplankton concentrations, transparency, nitrogen content, and phosphorus content. In addition, the CIET determines the extent to which tidal flats have been contaminated based on analyses of three items (reduction of ignition, chemical oxygen demand, and acid volatile sulfides).

According to the survey, consisting of 488 water quality assessments conducted over the past three years, grade 2 accounted for more than 81%. Grade 2 refers to a healthy state with almost no external pollutants, an institute official explained.

From late summer to autumn, 11 cases of grade 4 (bad) and 1 case of grade 5 (very bad), were found in some sea areas; however, these were attributed to temporary increases in phytoplankton due to shallow bay-type marine structures. In addition, tidal flat organic matter pollution was deemed to be very good with only one case out of 90 showing eutrophication, and there was little or no pollution.

The results of this survey will be used as basic data for establishing marine environment management policies through further research.

Kim Bong-hyeon, head of the Gyeonggi-do Maritime & Fisheries Resources Research Institute, said, “The research institute is assembling scientific and systematic data on the fishery environment through regular water quality and sediment surveys… Based on this, we will strive to improve not only marine pollution but also marine productivity.”