Western Xiamen Bay Research Articles

Distribution and source appointment of rare earth elements in offshore sediments of Western Xiamen Bay, Southeast China

The REEs concentrations in offshore sediments (surface sediments and core sediments) of Western Xiamen Bay and some potential sources (parent materials, Pb-Zn deposit, vehicle exhaust, atmospheric dust, ship paint, coal combustion and domestic sewage sludge) were determined to investigate the geochemical characteristics and major sources of REEs in the sediments of Western Xiamen Bay. The results showed that the mean concentrations of REEs in surface sediments and core sediments were 245.9 mg·kg−1 and 220.0 mg·kg−1, respectively, which were close to the background value of topsoil in Xiamen City. There were negative Eu anomaly and no Ce anomaly in general and LREEs had a significant enrichment relative to HREEs. The results of enrichment factor showed that REEs were slightly enriched in surface sediments. The patterns of chondrite-normalized REE exhibited a negative slope, indicating that the REEs in surface sediments were mainly from the continental crust. Parameters and normalized patterns of REEs suggested that the sediments in Western Xiamen Bay were mainly from terrestrial sources and also affected by anthropogenic activities such as domestic sewage sludge and coal combustion. The results of Pearson's correlations, chondrite-normalized REEs distribution patterns and ternary plot of (La/Yb)N-(La/Sm)N-(Gd/Yb)N for the surface sediments and some potential sources indicated that the REEs accumulated in the surface sediments might be related to natural sources (parent materials and Pb-Zn deposit) and anthropogenic activities (coal combustion and domestic sewage sludge).

Identification of Pb sources using Pb isotopic compositions in the core sediments from Western Xiamen Bay, China

Pb concentrations and Pb isotopic compositions (total and acid-extractable) in the core sediments collected from Western Xiamen Bay, China, were determined to investigate the Pb pollution history and trace the Pb sources. Pb concentration showed an increasing trend (from 40.3 to 64.2mgkg−1) with obvious fluctuation from 1967 to 2013, reflected by the core sediments. The enrichment factors of Pb were between 2 and 5, indicating a moderate enrichment. The relative contributions of Pb-Zn deposit and parent material to total Pb in the core sediments were 51%–62% and 38%–49%, respectively. Acid-extractable Pb isotopic signature was more sensitive than total Pb isotopic signature in identifying anthropogenic Pb sources due to the substantial variability of acid-extractable Pb isotopic ratios exhibited in the core sediments. Based on the acid-extractable Pb isotopic ratios, Pb-Zn deposit and industrial emission were regarded as the main anthropogenic Pb contributors.

Quantitative analysis of anthropogenic influences on coastal water – A new perspective

Coastal environment has been disturbed by human activities for a long time, especially in the rapidly urbanizing and industrializing areas. Although the surrounding area has achieved great economic success in the past 30 years, Western Xiamen Bay (China) is seriously affected by pollutants and is facing increasing ecological pressure. Because of this, Xiamen was selected in 1994 as a demonstration site for implementing an integrated coastal management program, which included a series of measures for protecting the coastal environment. However, coastal environment is dynamic, complex and site-specific, and thus a scientific quantitative evaluation framework is necessary for environment quality analysis and effective coastal management. In this study, we used oceanographic knowledge together with quantitative methods (Bai-Perron's structural break test) to analyze the long-term variations of water quality indices (pH, DO, COD, DIN, PO4-P and Oil) in Western Xiamen Bay. In addition, we compared with other coastal areas to identify the effectiveness of phosphorus-based nutrient management measures and predicted the probable variation trend in the future. The results show that in Western Xiamen Bay: (1) the concentrations of DO and Oil in seawater are effectively controlled by local coastal management measures; (2) seawater acidification will continue to worsen based on the present situation; and (3) the P-limitation treatment strategies are effective and PO4-P concentration starts to fall according to the multiple statistical analysis and Environmental Kuznets Curve. This paper hopes to provide an epitome of the conflicts and consolations between socioeconomic development and environmental quality in the past, and hints for coastal management in the future.

Distribution, fractionation, and contamination assessment of heavy metals in offshore surface sediments from western Xiamen Bay, China

Surface sediment samples were collected at 21 offshore sites in western Xiamen Bay, Southeast China. Total concentrations of Li, V, Cr, Co, Ni, Cu, Zn, Sr, Mn, Pb, Ba, Fe, and Ti were determined by inductively coupled plasma-optical emission spectrometry; Hg was determined by atomic fluorescence spectrometry. A modified BCR sequential extraction procedure was used to extract fractions of the above elements. Concentrations of Pb, Cr, and Hg at most sites met the primary standard criteria of Marine Sediment Quality except site S12 for Pb and S7 for Cr, while concentrations of Zn at 17 sites and Cu at seven sites exceeded the criteria. The mean concentration of Hg was three times higher than the background, with a possible source being the Jiulong River. Fe, Ti, Ba, Co, V, and Li dominated the residual phase, mainly from terrestrial input. Ni, Cr, Pb, and Hg in the non-residual phase varied largely between sites. Sr, Mn, Cu, and Zn were mainly in the non-residual fraction. Most sites showed considerable ecological risk; exceptions were site S7 (very high) and sites S10, S11, and S14 (moderate). Cu showed moderate-to-high pollution and Pb exhibited no-to-low pollution, while other metals had a non-pollution status according to their ratios of secondary phase to primary phase (RSP). Results of two assessment methods showed moderate pollution and a very high ecological risk for Cu, Zn, Ni, and Cr at site S7, which might be due to the local sewage treatment plant.

Lead Content and Isotope Composition in Surface Sediments in Western Xiamen Bay and Its Vicinity: Implication for Possible Source

Lead Content and Isotope Composition in Surface Sediments in Western Xiamen Bay and Its Vicinity: Implication for Possible Source

Spatial variability of summer and autumn phytoplankton community structure in Xiamen Western Bay based on pigment analysis

National Natural Science Funds of China [40906068]; Natural Science Foundation of Guangdong Province, China [9451063201002243]; Fundamental Research Funds for the Central Universities

Heavy metal contaminant remediation study of western Xiamen Bay sediment, China: Laboratory bench scale testing results

A surface sediment sample (<5 cm) was collected from a sewage sludge contaminated site (118°02.711′E, 24°32.585′N) within western Xiamen Bay, China, in July 2005 for a sediment decontamination study. A series of laboratory-based experiments under various conditions were performed using chemical complexation reagents (e.g., H 2C 2O 4, EDTA–2Na, etc.) and their combination in order to provide information for sediment remediation technology development. In this study, the results suggest that aeration and agitation of the sediment samples in distilled–deionized water (DDW) have either no or weak (<30%) effect on metal removal, whereas agitation, aeration and rotation of the samples in chemical complexation solutions yield much better metal removal efficiency (up to 90%). A low pH condition (e.g., pH < 3) and a low solid to liquid ratio (e.g., S:L = 1:50) could increase metal removal efficiency. The experimental results suggest that 0.20 M (NH 4) 2C 2O 4 + 0.025 M EDTA combination with solid:liquid ratio = 1:50 and 0.50 M ammonium acetate (NH 4Ac) + 0.025 M EDTA combination with solid:liquid ratio = 1:50 are the most effective methods for metal removal from the contaminated sediments. This research provides additional useful information for sediment metal remediation technology development.

Microelectrode Study of Oxygen Uptake and Organic Matter Decomposition in The Sediments of Xiamen Western Bay

Sediment cores were sampled from Xiamen Western Bay at five sites during the summer and winter of 2006 and Hg–Au microelectrodes were used to make on board measurements of the concentration gradients of dissolved oxygen, Mn2+, and Fe2+ within the sediments. The O2 concentrations decreased sharply from about 200 μmol L−1 in the bottom seawater to zero within a depth of a few millimeters into the sediment. Dissolved Mn2+ was detected below the oxic zones with peak concentrations up to 600 μmol L−1, whereas dissolved Fe2+ had peak concentrations up to 1,000 μmol L−1 in deeper layers. The elemental contents of organic carbon and nitrogen within the sediments were analyzed and their C/N ratios were in the range of 9.0 to 10.1, indicative of heavy terrestrial origin. Sediments from two sites near municipal wastewater discharge outlets had higher organic contents than those from the other sites. These high organic contents corresponded to shallow O2 penetration depths, high dissolved Mn2+ and Fe2+ concentrations, and negative redox potentials within the sediments. This indicated that the high organic matter content had promoted microbial respiration within the sediments. Overall, the organic content did not show any appreciable decrease with increasing sediment depths, so a quadratic polynomial function was used to fit the curve of O2 profiles within the sediments. Based on the O2 profiles, O2 fluxes across the seawater and sediment interface were estimated to be in the range 6.07 to 14.9 mmol m−2 day−1, and organic carbon consumption rates within the surface sediments were estimated to be in the range 3.3 to 20.8 mgC cm−3 a−1. The case demonstrated that biogeochemistry within the sediments of the bay was very sensitive to human activities such as sewage discharge.

Heavy metal contamination in western Xiamen Bay sediments and its vicinity, China

Concentrations of selected heavy metals (Cu, Pb, Zn, Cd, Cr, Ni and Fe) in surface sediments from nine sites in western Xiamen Bay and its vicinity were studied in order to understand current metal contamination due to urbanization and economic development in Xiamen, China. The sediment samples were collected in December 2004 and July 2005 respectively in order to examine temporal variations. In this study, we found that heavy metal concentrations in surface sediments sampled in the western Xiamen Bay and adjacent Maluan Bay and Yuandang Lagoon varied from 19 to 97 mg kg −1 for Cu, 45 to 60 mg kg −1 for Pb, 65 to 223 mg kg −1 for Zn, 0.11 to 1.01 mg kg −1 for Cd, 37 to 134 mg kg −1 for Cr, 25 to 65 mg kg −1 for Ni and 3.08 to 4.81% for Fe. Although all metal concentrations in sediments meets Chinese National Standard Criteria for Marine Sediment Quality, both metal enrichment factors (EF) and geoaccumulation index ( I geo) show that Pb contamination exists in the entire study area and contamination of other metals are also present in some locations depending on the sources, of which sewage outlets and commercial ports are the main sources of contaminants to the area. This study shows that using the sediment quality standard criteria only to assess sediments cannot properly reflect sediment contamination. A multiple approaches should be applied for the sediment quality assessment.

Hydroinformatics techniques in eco-environmental modelling and management

The high complexity of aquatic ecosystems and the multiple processes involved, make the development of ecohydraulics and eco-environmental models a challenging subject. Conventionally, computer-based models use a mathematical formulation for the processes involved which are then solved by numerical methods. These models are often derived based on the assumption of spatial homogeneity and conservation principles of mass, momentum and energy. Development of these models often demands a clear understanding of the processes involved. However, the above assumptions are easily violated when spatial heterogeneity, individual species behaviour and local interactions play a significant role in the system dynamics. In particular for eco-environmental systems, knowledge on local interactions that determine the overall system behaviour is not always available. Although the rapid advances of data-driven techniques have recently made great contributions to water-environment related research, data on ecosystems are often quite limited, which restricts the application of data mining methods to eco-environmental system modelling. In addition, no modelling – also not black-box modelling – can be undertaken without having at least some understanding of the basic processes and mechanisms involved. It is always advisable to start exploring any dataset using conventional statistical techniques, as elaborated in this paper for a case study on Western Xiamen Bay, China. Neural network trimming was then used to establish the dominant factors; it was shown that a relatively simple ANN model was quite capable of capturing the essential features, provided the right input parameters are chosen. Examples of integrated approaches to ecohydraulics modelling coupling formulations with cellular automata and physical equations with fuzzy rules are presented for applications on eutrophication modelling of Taihu Lake in China, competitive growths and colonization of two underwater macrophytes in Lake Veluwe in The Netherlands, and forecasting of algal blooms in the Dutch coastal waters on the North Sea. A mussel dynamics model developed for the Upper Mississippi River in the USA demonstrates the feasibility of individual based modelling in ecosystem dynamics. Numerical models are quite capable of simulating the abiotic aquatic environment, including complicated fluid flow and transport mechanisms. However, when it comes to simulating the biotic and ecosystem dynamics, the interaction of individual species with their environment, as well as the interactions amongst species, has to be taken into account. The future of ecohydraulics and eco-environmental modelling thus seems to lie in the integration of different paradigms and techniques, which is the core content of the hydroinformatics discipline.

The biogeochemistry of photosynthetic pigments in the Jiulong River estuary and Western Xiamen Bay

High performance liquid chromatography (HPLC) analysis of photosynthetic pigments in samples from Western Xiamen Bay and the Jiulong River Estuary showed that their major carotenoids were fucoxanthin, peridinin, zeaxanthin, violaxanthin, and diadinoxanthin. Diatoms dominated in the spring bloom, dinoflagellates in summer. Violaxanthin and chlorophyll b indicated the appearance of chrysophytes and green algae, most of which were freshwater species. The high phytoplankton biomass region was located at the inner part of the bay. Diatoms and dinoflagellates dominnated phytoplankton communities, contributing to over 50% of total biomass. All the main diagnostic carotenoids were significantly (P<0.01) correlated negatively to dissolved inorganic phosphorus, suggesting that they were limited by phosphorus. The high negative linear relationship (P<0.0001) between dissolved inorganic phosphorus and peridinin (dinoflagellates indicator) implied the potential of dissolved inorganic phosphorus for triggering red tide events in this region.

Distribution and composition of fahs in surface waters, porewater and sediments from Xiamen Western Bay

Xiamen Westem Bay's water and sediment quality were studied by determining the levels of sixteen polycyclic aromatic hydrocarbons (PAHs) in water, porewater and sediment samples from nine locations in the bay. Total PAH concentrations varied from 106 to 945 ng/l in water, below detection to 3548 ng/l in porewater, and 247 to 480 ng/g dry weight in surface sediments. PAHs levels in porewater were higher than those in surface water, due to the preference of these hydrophobic compounds for sedimentary phase instead of water. Such a concentration gradient implies a potential flux of pollutants from sediments to overlying water. The PAHs levels in sediments were one to several orders of magnitude lower than those in 1993, suggesting their decreased input in recent years and possible degradation with time.

Persistent organochlorine residues in sediments of Hong Kong Victoria Harbour and Xiamen Western Bay

Samples of surface sediment were collected from Victoria Harbour, Hong Kong (Aug. 1992), and Xiamen Western Bay (Nov. 1993), and analysed for organochlorine (OC) pesticides (HCHs, DDTs) and polychlorinated biphenyls (PCBs). Concentration ranges of HCHs, DDTs and PCBs in the survey area of Victoria Harbour were from undetectable to 9.4 μg/kg, 1.38–97 μg/kg and 3.2–81 μg/kg, respectively; those for Xiamen Western Bay were 0.14–1.12 μg/kg, 4.45–311 μg/kg and 0.05–7.24 μg/kg, respectively. The determined residue levels and distribution patterns of these organochlorines are discussed, and the Harbour and Bay contamination levels are compared. Two sediment cores were collected (Oct. 1994) from Xiamen Western Bay for study on the vertical profiles and pollution history of the above contaminants. The vertical profile characteristics indicated that the inner part of Xiamen Western Bay was once polluted by PCBs moderately and that there are still new inputs of DDT.