Spatial Distribution Assessment and Source Apportionment of Land-Based Pollutant Yield from Qingdao, China

Abstract

The spatial distribution of chemical oxygen demand (COD) and total nitrogen (TN) yield from Qingdao are studied by comparing pollutant yield amount, densities and spatial aggregation (Getis-Ord indexes) among the land-based pollutant source regions (PSRs) entering the three sub-seas (i.e. the Jiaozhou Bay (JZB), other coastal area in the Yellow Sea (OCAYS) and Laizhou Bay (LZB), respectively). Industrial composition of the loads are also studied by comparing pollutant yield among the sources of agriculture, rural domesticity, industry, urban domesticity and service, and calculation of Gini coefficient. Results show that spatial distribution of COD and TN yield from Qingdao are extremely unbalanced. The JZB, with less than 3% of the total coastal sea area of Qingdao, received 62% COD load and 65% TN yield from Qingdao, while the OCAYS, with more than 97% area, only received 23% COD and 20% TN, which consist with the much worsen water quality of JZB than that of OCAYS. On the other hand, the source apportionment of COD and TN loads in the PSRs entering JZB and the OCAYS was similar. The agricultural and domestic sources with high pollution intensity account for more than 80%, while the industrial and service sources with low pollution intensity account for less than 20%. While Gini coefficients, COD 0.81 and TN 0.84 which are much higher than the ‘imbalance’ threshold of 0.4, show the uneven industrial structure of Qingdao. These results may be useful in the determination of land-based pollution total amount control at the PSR level.