Baseline zinc levels and monitoring implications in sediments of the Changhua offshore wind farm region

Abstract

This study integrates data on the content of zinc (Zn) in the sediment during the construction of wind farms in the Changhua coastal area, and conducted two seasons of sediment surveys surrounding the Changhua offshore wind farms (OWFs). The survey results were compared with historical data from previous monitoring efforts in the Changhua offshore wind farm region. From 6 environmental impact assessments of Changhua OWFs, sedimentary Zn contents were below the effects range-median (ERM; 410 mg/kg) of the US National Oceanic and Atmospheric Administration (NOAA) standards. Our results showed that the Zn concentration in the sediment of the two sampling stations in this study was lower than the effect range low (ERL; 150 mg/kg) threshold. Compared among the sediments of CH-1 and CH-2 sites and other OWFs, the Zn concentrations were significantly lower than those of the Zhong Neng offshore wind farm, Zhang Fang offshore wind farm, and Haixia I/II offshore wind farm. In the spatial background, the distribution of Zn concentration in the southern area along the Changhua coastal sediments was higher than that in the northern area. The Mann-Kendall trend test analysis indicated a decreasing trend in the time series. Results of Geo-accumulation index (I _geo) and potential ecological risk (PERI) demonstrated that the sediment has low ecological potential risk. This study established baseline data on Zn concentrations in the sediment of the Changhua coastal area. The proposed alert value for Zn concentration in the Changhua coastal area environment monitoring in sediment is 83.6 mg/kg.