Abstract

The Huangmao Island dumping area is adjacent to the Pearl River Estuary in the South China Sea. From its first dumping activity in 1986 to 2017, 6750 × 104 m3 dredged materials were dumped in this dumping area. Sediment pollution levels, ecological risk, and benthic communities in 2011–2017 were evaluated; the results showed that the concentrations of the heavy metals (HMs; except Hg) in surface sediments of the dumping area met the class I standard of marine sediment quality (GB 18668-2002). HMs in the surface sediments were relatively high in the northern and central areas but relatively low in the south of the dumping area. Speculation was that the spatial variation in HM concentrations might be caused by dumping activities. The Nemerow index implied that the contaminated area was mainly in the north of the dumping area (S1, S2, and S3), where the dumping amount was the largest. The potential ecological risk (Eir) indices of Zn, As, Cu, and Pb indicate that these metals posed a low risk to the ecosystem of the dumping area, whereas Cd and Hg posed a high risk at some stations. The geoaccumulation indices (Igeo) of Zn, As, Cu, and Pb specified no pollution or light pollution in the study area, whereas those of Cd and Hg in most years indicated mild contamination levels. Benthic organisms in the study area were arthropods, chordates, annelids, mollusks, echinoderms, nemertinean, coelenterate, and echiuran, among which arthropods were the most abundant. The abundance of taxa and density of benthic organisms had a little difference among the stations within the dumping area, but were significantly lower than those of the stations outside the dumping area. In addition, non-metric multidimensional scaling analysis confirmed that the observed patterns separated the stations within the dumping area from stations outside the dumping area. The evaluation results of the HMs revealed that the dumping area with a large dumping amount was more severely polluted. Dumping dredged materials seemed to have a negative impact on the benthic community in the dumping area.

Highlights

  • In urbanization and the rapid development of the marine transportation industry and coastal engineering construction projects, many dredged materials are produced [1,2]

  • A few studies have been carried out to evaluate the effect of dumping activities to marine sediments and benthic community [3,17,20,21], but few studies have been conducted in the South China Sea, where there are 25 dumping areas as of 2017

  • The results showed that the concentration of As was higher than effect range low (ERL), and that of other heavy metals (HMs) was lower than ERL and effect range medium (ERM)

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Summary

Introduction

In urbanization and the rapid development of the marine transportation industry and coastal engineering construction projects, many dredged materials are produced [1,2]. A few studies have been carried out to evaluate the effect of dumping activities to marine sediments and benthic community [3,17,20,21], but few studies have been conducted in the South China Sea, where there are 25 dumping areas as of 2017. Among these dumping areas, the Huangmao Island dumping area is the earliest to received dredged materials. According to the research results, suggestions and measures are presented to provide technical support for the sustainable use of the dumping area

Description of the Study Area
Sampling
Laboratory Analysis
Statistical Analysis
HMs in the Sediments
Background
Temporal and Spatial Distribution Characteristics of HMs
Correlation Analysis between HMs and Other Environmental Factors
Pollution Assessment of HMs in Sediments
Characteristics of Benthic Community in the Dumping Area
Conclusions
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