DISTRIBUTION TREND OF HEAVY METALS AND PAHS IN SEDIMENT, POREWATER, AND WEST AFRICAN MUD CREEPER (Tympanotomy falcatus var. radula) FROM THE NIGER DELTA

Background: Petroleum-impacted Niger Delta creeks remain under-monitored, with few studies integrating sediment, porewater, and biota over time. Methods: Heavy metals (Fe, Zn, Ni, Cd, Cr), total petroleum hydrocarbons (TPH) and the 16 US EPA priority polycyclic aromatic hydrocarbons (ΣPAH₁₆) were measured monthly from March to August 2026 at three stations along Bille Creek, Rivers State, Nigeria. Samples comprised surface sediment, interstitial water and soft tissue of Tympanotonus fuscatus var. radula. Porewater physicochemical parameters were also measured. Analyses used ICP-OES, ICP-MS, GC-FID and GC-MS, with certified reference materials and routine quality control. Results: Sediment TPH peaked at 3,117.50 ± 10.14 mg/kg at Station 2, approximately 62 times the DPR EGASPIN sediment limit of 50 mg/kg. ΣPAH₁₆ ranged from 11.78 to 40.27 mg/kg and exceeded the USEPA effects range-low (ERL; 4.0 mg/kg) at Stations 2 and 3. Sediment cadmium at Stations 1 and 2 (0.79 and 1.14 mg/kg) exceeded the CCME interim sediment quality guideline. Porewater TPH was highest in March (14.36 ± 2.04 mg/L) and stabilised at 1.80–2.00 mg/L from April to August. Nickel (0.21–0.22 mg/L) and iron (1.20–1.47 mg/L) exceeded WHO drinking-water guideline values at all stations. In T. fuscatus, tissue cadmium, lead, arsenic, TPH and ΣPAH increased from Station 1 to Station 3, and cadmium (0.050 to 0.100 mg/kg) and ΣPAH (0.006 to 0.011 mg/kg) increased between March and August. Conclusions: The findings demonstrate persistent, spatially heterogeneous petroleum and metal contamination in Bille Creek, warranting pollution control and precautionary seafood safety measures.