Over one hundred years of trace metal fluxes in the sediments of the Pearl River Estuary, South China

Abstract

The rapid economic development in the Pearl River Delta (PRD) region in south China in the last three decades has had a significant impact on the local environment.Estuarine sediment is a major sink for contaminants and nutrients in the surrounding ecosystem. The accumulation of trace metals in sediments may cause serious environmental problems in the aquatic system. Thirty sediment cores were collected in the Pearl River Estuary (PRE) in 2000 for a study on trace metal pollution in this region. Heavy metal concentrations and Pb isotopic compositions in the four 210 Pb-dated sediment cores were determined to assess the fluxes in metal deposits over the last one hundred years. The concentrations of Cu, Pb and Zn in the surface sediment layers were generally elevated when compared with the sub-surface layers. There has been a significant increase in inputs of Cu, Pb and Zn in the PRE since the 1970s. The results also showed that different sampling locations in the estuary received slightly different types of inputs. Pb isotopic composition data indicated that the increased Pb in the recent sediments was of anthropogenic origin. The * Corresponding author (X.D. Li), email: cexdli@polyu.edu.hk; fax: (852) 2334 6389; tel: (852) 2766 6041 This is the Pre-Published Version.2 results of trace metal influxes showed that about 30% of total Pb and 15% of total Zn in the sediments in the 1990s were from anthropogenic sources. The combination of trace metal analysis, Pb isotopic composition and 210 Pb dating in an estuary can provide vital information on the long-term accumulation of metals in sediments.

Trace metal distribution in sediments of the Pearl River Estuary and the surrounding coastal area, South China

“…Means and ranges of trace metal concentrations in various operationally defined geochemical fractions in the surface sediments from the PRE (Li et al, 2000a(Li et al, , 2001Liu et al, 2003) The prefixes of the sample IDs represent the locations of the samples shown in the sampling map, while the number after the prefixes correspond to the depths in the sediment profiles Pb of the sediments at the coastal zone (this study) and the PRE (Ip et al, 2004), atmospheric deposition (Wong et al, 2003) and soils in the PRD region (Wong et al, 2002) and Hong Kong , as well as natural geological sources and anthropogenic sources in the PRD (Zhu et al, 2001) (Li et al, 2000a(Li et al, , 2001Liu et al, 2003) and the surrounding coastal area (in the present study) Pb of the sediments at the coastal zone (this study) and the PRE (Ip et al, 2004), atmospheric deposition (Wong et al, 2003) and soils in the PRD region (Wong et al, 2002) and Hong Kong , as well as natural geological sources and anthropogenic sources in the PRD (Zhu et al, 2001) …”

“…The Pb isotopic compositions of some natural and anthropogenic sources in the region have previously been studied (Zhu, 1995;Zhu et al, 1998Zhu et al, & 2001Duzgoren-Aydin et al, 2004). The Pb isotopic composition of the surface and sub-surface sediments showed clear differentiation (Ip et al, 2004). This makes it possible to differentiate between the recent anthropogenic inputs and the natural geological Pb of the sediments in the adjacent coastal area.…”

“…Some investigations have used Pb isotope compositions in sediments to distinguish and quantify Pb inputs between natural and anthropogenic sources (Farmer et al, 1996;Munksgaard et al, 1998;Li et al, 2001;Ip et al, 2004).…”

“…Various studies of trace metal contamination in the sediments of the PRE have recently been conducted (Li et al, 2000a(Li et al, , 2000b(Li et al, , 2001Liu et al, 2003;Ip et al, 2004). The previous works showed that the enrichment of trace metals in the recently deposited sediments of the PRE was the result from rapid industrial development and urbanisation in the surrounding area in the last few decades.…”

Urban environmental geochemistry of trace metals

“…The toxicological effects are further aggravated by the unique physiology of children, the sensitivity of their developing vital organs, and different chemical forms of metals involved (Hrudey et al, 1996). Other indirect consequences of trace metal contamination of the urban environment include the subsequent migration of the pollutants to receiving bodies of water via urban runoff, resulting in the trace metal enrichment of sediments (Sutherland and Tolosa, 2000;Ip et al, 2004). This may affect the quality of aquatic ecosystems and increase the body loadings of aquatic organisms through bioaccumulation and biomagnification, potentially causing trace metal contamination of the food chain (Callender and Rice, 2000).…”