Division Method of Pollutant Discharge Region and Estimation of the Mainland-Based Pollutant Loads Entering the Bohai Sea

Ding, D.-s.; Li, K.-q.; Su, Y.; Liang, S.-k.; Qu, K.-m.; Cui, Z.-g.; Zhang, P., and Wang, X.-l., 2020. Division method of pollutant discharge region and estimation of the mainland-based pollutant loads entering the Bohai Sea. In: Yang, D.F. and Wang, H. (eds.), Recent Advances in Marine Geology and Environmental Oceanography. Journal of Coastal Research, Special Issue No. 108, pp. 312–316. Coconut Creek (Florida), ISSN 0749-0208.The land-based pollutant total load control (PTLC) is an effective approach to comprehensively solve the current problem of marine pollution. The pollutant discharge region (PDR), which is the responsibility and source group, was divided for PTLC source assessment. According to the U.S. TMDLs mode, by tracing the source of the 145 points from which the land-based pollutants were discharged into the Bohai Sea, the Bohai rim was divided into two parts: the Bohai pollutant discharge band (in-band for short), whose pollutant was discharged into the Bohai Sea, and out-of-band, whose pollutant was not discharged into the Bohai Sea. The in-band area included 343 county-level administrative regions of 37 prefectural-level cities. The PDRs are further formed by the intersection of 115 watersheds, 13 sewage plants, and 17 national key monitoring sewage enterprises. These sewage enterprises discharged sewage into the sea by using an independent point, with 343 county-level administrative regions of 37 prefectural-level cities in-band. A total of 145 PDRs was combined to 42 and were further lumped together into three PDR systems. On the basis of the PDRs, the area, CODCr, nitrogen (DIN), and phosphorus (DTP) discharge flux of each PDR were estimated, which totaled 40,4476 km2, 941,072 tons, 90,570 tons, and 12,808.8 tons, respectively. The CODCr, DIN, and DTP load per one square kilometer of each PDR were estimated, which averaged 4.99, 0.42, and 0.09 tons, respectively, and varied between 0.001 and 64.068, 0.006 and 5.063, and 0.0007 and 1.672, respectively. The key PDRs were discussed. From the results, it is seen that the key PDRs mainly lie in Hebei Province along with the large rivers.