Distribution and contamination status of chromium in surface sediments of northern Kaohsiung Harbor, Taiwan

The distribution, enrichment, accumulation, and potential ecological risk of chromium (Cr) in the surface sediments of northern Kaohsiung Harbor, Taiwan, China were investigated. Sediment samples from ten locations located between the river mouths and harbor entrance of northern Kaohsiung Harbor were collected quarterly in 2011 and characterized for Cr, aluminum, water content, organic matter, total nitrogen, total phosphorous, total grease, and grain size. Results showed that the Cr concentrations varied from 27.0 to 361.9 mg/kg with an average of (113.5±87.0) mg/kg. High Cr concentration was observed near the Jen-Gen River mouth. The mean Cr concentration was high at 255.5 mg/kg, which was at least 2 to 7 times than that of other sites. This might imply significant Cr contribution from upstream receiving tanneries wastewater into the Jen-Gen River. The spatial distribution of Cr reveals relatively high in the river mouth region, especially in Jen-Gen River, and gradually diminishes toward the harbor entrance region. This indicates that the major sources of Cr pollution from upstream industrial and municipal wastewaters discharged along the river bank; and Cr may drift with sea current and be dispersed into open sea. Moreover, Cr concentrations correlated closely to the physical-chemical properties of the sediments, which suggested the influence of industrial and municipal wastewaters discharged from the neighboring industrial parks and river basins. Results from the enrichment factor and geo-accumulation index analyses imply that the Jen-Gen River sediments can be characterized as moderate enrichment and none to medium accumulation of Cr, respectively. However, results of potential ecological risk index indicate that the sediment has low ecological potential risk. The results can provide valuable information to developing future strategies for the management of river mouth and harbor.