Masan Bay (Hanja/Romanization: 馬山灣/Masan-man) is a long and narrow inlet of semi-enclosed bay located at the Southern Gyeongsang Provincial Capital, Changwon. because of its geographical features, the bay has shown a slow rate of water exchange and a trapping effect on contaminants discharged from surrounding industrial complexes and cities. The industrial complexes in Masan and Changwon-Central Districts which include petrochemical, heavy metal, electrical and plastic industries, as well as heavily populated districts in Changwon City are located adjacent to the bay. Masan bay has been listed as a special management coastal zone (SMCZ) by the Korean government since 1983, in association with increased contaminant levels. There are some reports of the distribution and characteristics of organic contaminants such as OCPs, polybrominated diphenyl ethers (PBDEs), poly chlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxin/dibenzofurans (PCDD/Fs) and Nonylphenols (NPs) in Masan Bay environments. The studies which are conducted by Hong Seong-jin (홍성진) and Shin Kyung-hoon (신경훈) showed that Masan Bay is heavily polluted by toxic chemicals originating from surrounding industrial complexes and cities, similar to Lake Sihwa in Siheung City, Gyeonggi Province.
Spatial distributions of NPs in Masan Bay exhibit generally greater abundance in the inner bay than in the outer bay. NP concentrations measured in the Masan Bay environment during the past few years. Although there is insufficient data to understand the temporal trends of NPs in the Masan Bay environment, the concentrations of NPs in surface sediments show a gradually decreasing trend.
On the other hand, a waste water treatment plant (WWTP) which is located at Masan District and its effluent outlet is recognized as a point source of NPs into Masan Bay. The WWTP treats 260,000t d^-1 of industrial and domestic wastewater and discharges its effluent into Masan Bay via underground pipeline. Li and Moon investigated concentrations of NPs, PCDD/Fs, dioxin-like PCBs (dl-PCBs), PBDEs and fecal sterol in the WWTP outfall area to identify the impact of effluents. They collected surface sediment samples based on a fan-shaped sampling scheme from around the WWTP outfall. Concentrations of NP, NP1EO and NP2EO in surface sediments were 68-600, 23-3,491 and 27-2,800 ng g^-1 dw in 2004 and 18-269, 18-576 and 4-258 ng g^-1 dw in 2005 respectively. There were clear decreasing trends for toxic organic contaminants such as NPs, PCSS/Fs, dl-PCBs and PBDEs with increasing distance from the WWTP outfall, suggesting that the WWTP discharge is the major source of these toxic substances, including NPs.
Temporal trends of NPs were recorded in sediment cores collected near the outfall of the WWTP. NPs increased gradually from the early 1990s, with the highest concentration detected using Pb-210 dating at 8-10cm depth, corresponding approximately to the year 2000 and subsequently decreased. There were similar trends in the PCDD/F and dl-PCB concentration profiles. These trends are closely related to the operation and efficiency of the WWTP. The WWTP was established in 1994 and was upgraded to use an activated sludge treatment method in the early 2000s. Spatial and vertical profiles of NPs around the WWTP in Masan Bay sediments suggested that discharges from the WWTP apparently contributed to NP contamination in the Unified Changwon City. Therefore, an adequate capacity of WWTPs needs to be established, as well as continuous monitoring for quality improvement of the aquatic improvement.
Most chemicals in the water column could be assimilated by various aquatic organisms and concentrated or metabolized in their bodies. NP levels in mussels found in Masan Bay ranged from 51 to 289 ng g^-1 dw (average = 140 ng g^-1 dw), showing high correlation with water (r^2=0.98) and sediment (r^2=0.90) NP concentrations at the same site. Wang calculated the bioconcentration factors (BCF) and the average was found to be 2,990 obtained from NP concentrations in mussels and water.