Heavy metal pollution and assessment of the tidal flat sediments near the coastal sewage outfalls of shanghai, China

Abstract

Zn, Cu, Cr and Pb concentrations of the sediment collected from three tidal flat sites of Yangtze estuary were investigated in October 2003. Results showed that the average concentrations of heavy metals in the sediments were two to three times to the environment background values of Yangtze estuary tidal flat sediment. The heavy metal concentrations in the sediments near the Bailonggang (BLG) and Laogang (LG) sewage outfalls were obviously higher than those of Chaoyang (CY) tidal flat where there are no sewage outfalls near the coast. And the concentrations of heavy metals in the surface sediments of LG tidal flat decreased with the increasing of the distance to the sewage outfalls. The heavy metal concentration profile in the sediment core changed with the depth, and generally reached maximum values at the depth of plant roots. The assessment results showed that the sediments of LG, BLG and CY tidal flat had been polluted by heavy metals in different level. The pollution degree of heavy metals in the sediments was as follows: Zn [ Cu [ Pb [ Cr. The potential ecological risks of the four heavy metals in three tidal flat sites sediment were all at a middle level, and Cu and Pb made the main contributions. The adverse ecological effects caused by the four heavy metals did not occur frequently.

A method of identifying priority spatial patterns for the management of potential ecological risks posed by heavy metals

“…where PERI is the potential HM ecological risks index and is the sum of the individual HM potential ecological risk; E i r is the potential ecological risk of the HM i; T i r is the toxic response factor of the HM i presented by Hakanson [39]; C i f is the pollution index of the HM i; C i is the concentration of the HM i, which is the average concentration of sediment soil samplings; C i n is the evaluation reference value of the HM i, which is the background value of the HM i in the study area [25].…”

“…T i r , for Cu, Zn, Ni, Cd, and Cr, is 5, 1, 5, 30, and 2, respectively [22,25,37,39]. C i n for Cu, Zn, Ni, Cd, and Cr, is 30 (mg/kg), 80 (mg/kg), 22 (mg/kg), 0.5 (mg/kg), and 60 (mg/kg), respectively [25,39].…”

“…C i n for Cu, Zn, Ni, Cd, and Cr, is 30 (mg/kg), 80 (mg/kg), 22 (mg/kg), 0.5 (mg/kg), and 60 (mg/kg), respectively [25,39].…”

“…HM from various sources have caused deleterious effects on wildlife habitats, degraded ecosystem integrity, and possibly poisoned humans in coastal areas [1,[21][22][23]. The key research questions on HM in coastal regions include potential ecological risk assessment (ERA) [22], geochemical cycling [3], risk assessment of HM induced by anthropogenic disturbances [24], and biological toxicology assessments [1,2,23,25]. How to make quantitative ERA and control the ecological risks associated with HM are the pending questions in coastal regions around the world [1,2,26].…”

“…Different methods have been proposed to quantitatively assess the cumulative ecological risks, such as the potential ecological risk index (PERI) index [22,39], geoaccumulation index [40][41][42], and excess after regression analysis [43]. In China, PERI index have been widely used in various regions to assess the HM's potential ecological risks, such as the Qinhuai River sediments [44], coastal sediments [6], Lake Dian [45], coal mine area [46], farmlands areas [47], Shanghai coastal areas [25], and gold mining area [37]. In the PERI index method, thresholds are set to classify the HM's potential ecological risks into three categories: low, moderate, and high risk.…”