Oyster arsenic, cadmium, copper, mercury, lead and zinc levels in the northern South China Sea: long-term spatiotemporal distributions, combined effects, and risk assessment to human health

2022 ◽  
Author(s):  
Lifei Wang ◽  
Xuefeng Wang ◽  
Haigang Chen ◽  
Zenghuan Wang ◽  
Xiaoping Jia
Keyword(s):  
Risk Assessment ◽  
South China Sea ◽  
Human Health ◽  
South China ◽  
Northern South China Sea ◽  
Combined Effects ◽  
China Sea ◽  
Lead And Zinc ◽  
Zinc Levels

scholarly journals Oyster As, Cd, Cu, Hg, Pb and Zn Levels in the Northern South China Sea: Long-term Spatiotemporal Distributions, Interacting Effects, and Risk Assessment to Human Health

2021 ◽  
Author(s):  
Lifei Wang ◽  
Xuefeng Wang ◽  
Haigang Chen ◽  
Zenghuan Wang ◽  
Xiaoping Jia
Keyword(s):  
Heavy Metals ◽  
Risk Assessment ◽  
Heavy Metal ◽  
South China Sea ◽  
Human Health ◽  
South China ◽  
Northern South China Sea ◽  
China Sea ◽  
Metal Levels

Abstract Estuarine and coastal ecosystems are often considered vulnerable due to the complex biogeochemical processes and the human disturbances through a variety of pollution. Among environmental contaminants, heavy metals in estuarine and coastal ecosystems have been of increasing concern in environmental conservation. Long-term exposure to heavy metal contamination, mainly through food and water, could be harmful to human health. It is therefore critical to understand the quantitative comparisons and interacting effects of different heavy metals in common seafood species, such as oysters. This work studied the long-term spatiotemporal trends and health risk assessment of oyster arsenic (As), cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb) and zinc (Zn) levels in the coastal waters of northern South China Sea. Cultured oysters (Crassostrea rivularis) from 23 estuaries and harbors in the coastal areas of northern South China Sea in 1989–2015 were analyzed for the spatiotemporal trends of the six heavy metal levels. Metal pollution index (MPI), target hazard quotient (THQ) and hazard index (HI) were used for quantifying the exposure of the six heavy metals to human health through oyster consumption. Principal component analysis (PCA) was used for assessing the relative importance of the six metals in oyster heavy metal distribution patterns in the northern South China Sea. Overall, the As, Cd, Cu, Hg, Pb and Zn levels in oysters from the northern South China Sea generally declined from 1989 to 2015, stayed relatively high (MPI = 2.42–3.68) during 1989–2000, gradually decreased since 2000, and slightly increased after 2010. Oyster heavy metal levels were highest in the Pearl River Estuary (MPI = 1.20–5.52), followed by west Guangdong and east Guangdong, Guangxi, and Hainan coastal waters. This pattern is probably because economics and industry around the Pearl River Estuary have been growing faster than the other areas of this work in the recent two decades, and it should be taken as a hotspot for the monitoring of seafood safety in southern China. Principal component analysis indicated that Cu, Zn and Cd were the most important metals in the long-term distributions of oyster heavy metal levels in the northern South China Sea. Health risk assessment suggested that the risk of the six heavy metals exposure through oyster consumption were relatively high during 1989–2005 (THQ = 1.01–5.82), significantly decreased since 2005 (THQ < 1), and slightly increased after 2010.

Structural Reliability Based Design and Assessment Acceptance Criteria Development for Fixed Offshore Platforms in South China Sea Under Extreme Storm Conditions

2013 ◽  
Author(s):  
Linbin Li ◽  
Ping Li ◽  
Yuan Liu
Keyword(s):  
South China Sea ◽  
South China ◽  
Structural Reliability ◽  
Northern South China Sea ◽  
Offshore Platforms ◽  
Environmental Load ◽  
Acceptance Criteria ◽  
China Sea ◽  
Extreme Storm

This paper presents a reliability based methodology to develop the design and assessment acceptance criteria for fixed offshore platforms in the northern South China Sea under extreme storm events. Firstly, the atmosphere, ocean and wave coupled numeric simulation model with site measurements verification is used to generate the time series directional waves, currents and winds for each refined grid point in the studied area during the past 40 years. Secondly, the storm and response based load statistics method is adopted to investigate the long term distribution of the extreme environmental load considering the joint occurrence of wave, current and wind. Thirdly a structural reliability method is proposed to quantify the probability of platform failure subjected to extreme storms. The environmental load factors for new design platforms in the northern South China Sea with different exposure categories are calibrated. Finally risk assessment is performed to develop the acceptance criteria for the exiting platforms in terms of reserve strength ratio based on the failure consequence and failure probability of platforms. Case studies are presented to illustrate the applications of the proposed method and how the reliability analysis results can be used in development of long term structural integrity management strategies.

scholarly journals Long term changes in the ecosystem in the northern South China Sea during 1976–2004

2008 ◽  
Vol 5 (5) ◽  
pp. 3737-3779 ◽  
Author(s):  
X. Ning ◽  
C. Lin ◽  
Q. Hao ◽  
C. Liu ◽  
F. Le ◽  
...  
Keyword(s):  
Climate Change ◽  
South China Sea ◽  
South China ◽  
Northern South China Sea ◽  
Seawater Temperature ◽  
Climate Trend ◽  
Redfield Ratio ◽  
China Sea ◽  
N Limitation

Abstract. Physical and chemical oceanographic data were obtained by seasonal monitoring along Transect N in the northern South China Sea (nSCS) during 1976–2004. Fluctuations of DIN (dissolved inorganic nitrogen), seawater temperature (SST and Tav – average temperature of the water column), N:P ratio and salinity (Sav and S200 – salinity at the 200 m layer) exhibited an increasing trend, while those of T200, DO, P, Si, Si:N and SSS exhibited a decreasing trend. The annual rates of change in DIN, DO, T and S revealed pronounced changes, and the climate trend coefficients Rxt, which was defined as the correlation coefficient between the time series of an environmental parameter and the nature number, were 0.38 to 0.89 and significant (p≤0.01 to 0.05). Our results also showed that the ecosystem has obviously been influenced by the positive trends of both SST and DIN, and negative trends of both DO and P, e.g. before 1997, DIN concentrations in the upper layer were very low and N:P ratios were less than half of the Redfield ratio of 16, indicating potential N limitation. However, after 1997, all Si:P ratios were >22 and the Nav:Pav was close to the Redfield ratio, indicating potential P limitation, and therefore N limitation has been reduced after 1997. Ecological investigation shows that there have been some improved responses of the ecosystems to the long-term environmental changes in the nSCS, and chlorophyll-a concentration, primary production, phytoplankton abundance, benthic biomass, cephalopod catch and demersal trawl catch have increased. But phosphorus depletion in upper layer may be related to the shift in the dominant species from diatoms to dinoflagellates and cyanophytes. The ecosystem response was induced by not only anthropogenic activities, but also global climate change, e.g. pronounced responses to ENSO. The effects of climate change on the nSCS were mainly through changes in the monsoon winds, and physical-biological oceanography coupling processes.

scholarly journals Long term changes in the ecosystem in the northern South China Sea during 1976–2004

2009 ◽  
Vol 6 (10) ◽  
pp. 2227-2243 ◽  
Author(s):  
X. Ning ◽  
C. Lin ◽  
Q. Hao ◽  
C. Liu ◽  
F. Le ◽  
...  
Keyword(s):  
Climate Change ◽  
South China Sea ◽  
South China ◽  
Global Climate Change ◽  
Global Climate ◽  
Northern South China Sea ◽  
Redfield Ratio ◽  
China Sea ◽  
N Limitation

Abstract. Physical and chemical oceanographic data were obtained by seasonal monitoring along a transect (Transect N) in the northern South China Sea (nSCS) during 1976–2004. Fluctuations of DIN (dissolved inorganic nitrogen), seawater temperature (SST and Tav – average temperature of the water column), N:P ratio and salinity (Sav and S200 – salinity at the 200 m layer) exhibited an increasing trend, while those of T200, DO, P, Si, Si:N and SSS exhibited a decreasing trend. The annual rates of change in DIN, DO, T and S revealed pronounced changes, and the climate trend coefficients, which was defined as the correlation coefficient between the time series of an environmental parameter and the nature number (namely 1,2,3,......n), were 0.38 to 0.89 and significant (p≤0.01 to 0.05). Our results also showed that the ecosystem has obviously been influenced by the positive trends of both SST and DIN, and negative trends of both DO and P. For example, before 1997, DIN concentrations in the upper layer were very low and N:P ratios were less than half of the Redfield ratio of 16, indicating potential N limitation. However after 1997, all Si:P ratios were >22 and the Nav:Pav was close to the Redfield ratio, indicating potential P limitation, and therefore N limitation has been reduced after 1997. Ecological investigation shows that there have been some obvious responses of the ecosystems to the long-term environmental changes in the nSCS. Chlorophyll-a concentration, primary production, phytoplankton abundance, benthic biomass, cephalopod catch and demersal trawl catch have increased. But phosphorus depletion in upper layer may be related to the shift in the dominant species from diatoms to dinoflagellates and cyanophytes. The ecosystem response was induced by not only anthropogenic activities, but also global climate change, e.g. ENSO. The effects of climate change on the nSCS were mainly through changes in the monsoon winds, and physical-biological oceanography coupling processes. In this study physical-chemical parameters were systemic maintained, but the contemporaneous biological data were collected from various sources. Regional response to global climate change is clearly a complicated issue, which is far from well understood. This study was made an attempt to tackle this important issue. For the aim these data were valuable.

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