Geochemistry of organic carbon and nitrogen in surface sediments of coastal Bohai Bay inferred from their ratios and stable isotopic signatures

► Geochemistry of organic matter in sediments of coastal Bohai Bay was studied. ► Sampling area covered its marine region and the major rivers it connects with. ► Most of organic matter from land is deposited before it meets the sea. ► Much attention should be paid to river sediments for environmental risk assessment.