Improved source apportionment of PAHs and Pb by integrating Pb stable isotopes and positive matrix factorization application (PAHs): A historical record case study from the northern South China Sea

Minggang Cai; Yan Lin; Meng Chen; Weifeng Yang; Huihong Du; Ye Xu; Shayen Cheng; Fangjian Xu; Jiajun Hong; Mian Chen; Hongwei Ke

doi:10.1016/j.scitotenv.2017.07.190

Improved source apportionment of PAHs and Pb by integrating Pb stable isotopes and positive matrix factorization application (PAHs): A historical record case study from the northern South China Sea

Sci Total Environ. 2017 Dec 31:609:577-586. doi: 10.1016/j.scitotenv.2017.07.190. Epub 2017 Jul 27.

Authors

Minggang Cai¹, Yan Lin², Meng Chen³, Weifeng Yang², Huihong Du², Ye Xu², Shayen Cheng⁴, Fangjian Xu⁵, Jiajun Hong⁶, Mian Chen², Hongwei Ke⁷

Affiliations

¹ State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361102, China; Fujian Provincial Key Laboratory for Coastal Ecology and Environmental Studies, Xiamen University, Xiamen 361102, China; College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China.
² College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China.
³ Fujian Provincial Key Laboratory for Coastal Ecology and Environmental Studies, Xiamen University, Xiamen 361102, China; College of the Environment and Ecology, Xiamen University, Xiamen 361102, China.
⁴ College of Ocean Science and Resource, National Taiwan Ocean University, Keelung 20224, Taiwan.
⁵ College of Geosciences, China University of Petroleum, Qingdao 266555, China.
⁶ College of the Environment and Ecology, Xiamen University, Xiamen 361102, China.
⁷ College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China. Electronic address: Hongwei_KE@xmu.edu.cn.

PMID: 28763655
DOI: 10.1016/j.scitotenv.2017.07.190

Abstract

To obtain the historical changes of pyrogenic sources, integrated source apportionment methods, which include PAH compositions, diagnostic ratios (DRs), Pb isotopic ratios, and positive matrix factorization (PMF) model, were developed and applied in sediments of the northern South China Sea. These methods provided a gradually clear picture of energy structural change. Spatially, Σ₁₅PAH (11.3 to 95.5ng/g) and Pb (10.2 to 74.6μg/g) generally exhibited decreasing concentration gradient offshore; while the highest levels of PAHs and Pb were observed near the southern Taiwan Strait, which may be induced by accumulation of different fluvial input. Historical records of pollutants followed closely with the economic development of China, with fast growth of Σ₁₅PAH and Pb occurring since the 1980s and 1990s, respectively. The phasing-out of leaded gasoline in China was captured with a sharp decrease of Pb after the mid-1990s. PAHs and Pb correlated well with TOC and clay content for core sediments, which was not observed for surface sediments. There was an up-core increase of high molecular PAH proportions. Coal and biomass burning were then qualitatively identified as the major sources of PAHs with DRs. Furthermore, shift toward less radiogenic signatures of Pb isotopic ratios after 1900 revealed the start and growing importance of industrial sources. Finally, a greater separation and quantification of various input was achieved by a three-factor PMF model, which made it clear that biomass burning, coal combustion, and vehicle emissions accounted for 40±20%, 41±13%, and 19±12% of PAHs through the core. Biomass and coal combustion acted as major sources before 2000, while contributions from vehicle emission soared thereafter. The integrated multi-methodologies here improved the source apportionment by reducing biases with a step-down and cross-validation perspective, which could be similarly applied to other aquatic systems.

Keywords: Energy structure; Lead (Pb); Northern South China Sea; Pb isotopic ratios; Polycyclic aromatic hydrocarbons (PAHs); Positive matrix factorization (PMF).