Lingding Bay Research Articles

Recent geomorphic change in LingDing Bay, China, in response to economic and urban growth on the Pearl River Delta, Southern China

Decreased fluvial water and sediment discharge, increasing land reclamation, changing climate, and rising sea level have had an ever-increasing impact on river deltas, particularly those deltas bordering Southeast Asia. Utilizing 100years of navigational and bathymetric data, together with more than 50years of fluvial discharge data, we here document the impact of human activities on the Pearl River Delta and its estuary at LingDing Bay, China, the site of recent rapid economic expansion and urbanization. Between 1906 and 1988, approximately 80km2, ~1km2/yr, of land was reclaimed from the Bay, almost entirely for agriculture. During the ensuing 20years, 1988–2008, nearly 200km2 of land was reclaimed (10km2/yr), mostly to be used for manufacturing and shipping facilities; even some of the previously reclaimed agricultural land was converted to industrial use. Most of the reclaimed land came from a corresponding loss of intertidal and shallow depths: between 1988 and 2008, the area occupied by supratidal and subtidal flats (−2 to 5m water depths) declined by ~180km2. Channel dredging to accommodate ever larger ships, in contrast, increased areas with depths greater than 10m by about 36km2. Although water volume in the northern bay has decreased by 20% since 1906, decreasing bay area has resulted an overall 15% deepening of the bay. With continued economic expansion in the Pearl River Delta, LingDing Bay should continue to shrink in both area and water volume, although the bay should continue to deepen.

Longitudinal Transportation Mechanism of Sallinity in West Channel of Lingding Bay in Dry Season, China

Estuary is the transition zone,where fresh water and salty water mixes strongly.In dry season,because Discharge of the Pearl River water decreases,salt water intrusion become serious in the Pearl River delta,and affect the safety of fresh water supply.So,salinity transport mechanism is a very important topic.In this paper,according to the measured data in November 3-4,2005,calculate and analyze the longitudinal flow characteristics,salinity distribution and transport mechanisms. Research results show that the velocity varieties with ebb and flood processes,the surface velocity is larger than that of bottom and middle layer.In ebb slack and flood slack period,there is a zero velocity point,and its movement distance is up to 10km.Vertical residual circulation is obvious, surface layer is to sea,and bottom layer is to land.Net salinity transport direction is from sea to land.salinity vertical stratification is evident,and varieties obviously with tide changes.Surface salinity gradient is larger In flood period,and bottom salinity gradient is larger in ebb period.In ebb slack time,salinity is vertical uniform distribution.

AN ANALYSIS OF THE CHANGES AND EVOLVEMENTS ON THE FORESHORE AND DEEP CHANNELS OF LINGDING BAY IN PEARL RIVER ESTUARY

By means of GIS and remote sensing technique, the changes and evolvements characteristics of foreshore and deep channels of Lingding bay in Pearl River Estuary are analyzed. The change reasons and consequences are also illustrated. Basing this, it reminds us of standardizing the development behavior to the coastal area in favor of the long_term development of Pearl River Delta from the sustainable development high_points of coastal area.

Distribution, abundance, and individual movements of Indo-Pacific humpback dolphins (Sousa chinensis) in the Pearl River Estuary, China

AbstractTo obtain critical information on distribution and abundance of Indo-Pacific humpback dolphins (Sousa chinensis) residing in the Pearl River Estuary (PRE), systematic line-transect surveys and photo-identification studies were conducted in the eastern and western sections of the estuary in 2005–2006 and 2007–2008, respectively. Dolphins in the eastern section occurred throughout Lingding Bay, whereas their distribution in the western section extended from the mouth of Modaomen to the channel between Shangchuan and Xiachuan islands. Variations in dolphin distribution during the wet and dry seasons were evident and probably associated with movements of their prey species. Photo-identification of individuals confirmed exchange of at least some individuals between the western and eastern sections of PRE, and thus dolphins from both areas almost certainly comprise a single population. Using line-transect analysis, the total population size of the PRE humpback dolphins was estimated to be 2555 during the wet season and 2517 during the dry season. However, these should be considered preliminary as the coefficients of variation in some survey areas were high. Further studies should focus on refining these estimates and working towards understanding the western boundary of the PRE population.

Distribution of alkylphenols in the Pearl River Delta and adjacent northern South China Sea, China

The occurrence of alkylphenols (APs) was investigated in surface water and sediments from the Pearl River Delta and adjacent northern South China Sea. Most of the water samples contained detectable amounts of APs, ranging up to 0.628 μg l −1 for nonylphenol (NP) and 0.068 μg l −1 for octylphenol (OP). APs were found in all of the sediment samples with concentrations ranging from 59 to 7808 μg kg −1 for NP and from 1 to 93 μg kg −1 for OP. The Zhujiang River showed the highest concentrations of APs in both water and sediments. Significant decrease of APs concentrations going from the Zhujiang River to the Shiziyang River was observed. The Xijiang River contained concentrations of APs slightly higher in water but relatively lower in sediments than the Lingding Bay, which might be attributed to their different hydrodynamic and sedimentary characteristics. There was a decreasing trend of APs in water from the rivers to the estuary and further to the sea on the whole. In the Lingding Bay and its outer waters, concentrations of APs in sediments increased to a maximum and then decrease seaward, which was consistent with the distribution trend of the sediment organic carbon contents. Linear regression analyses showed the concentrations of APs were markedly correlated with the sediment organic carbon contents, indicating that the sediment organic carbon is an important factor controlling the levels of APs in sediments.

Temporal and spatial variations in signatures of sedimented organic matter in Lingding Bay (Pearl estuary), southern China

The concentration, accumulation rate, the ratio of total organic carbon to total nitrogen, and δ 13C value of sedimented organic carbon from three 210Pb-dated sediment cores were studied in Lingding Bay, a large estuary of the Pearl River in southern China. It was found that terrestrial organic matter contributed significantly to the Lingding Bay sediments, and that hydrodynamic conditions greatly influenced the sources of organic matter, and hence carbon isotope distributions. Specifically, river-transported terrestrial organic matter is the main type of organic matter in core ZJ-6, located near the northwestern river outlets and overlaid mainly by flowing river water. Aquatic organic matter is the main input for the core ZJ-7 in the east of the bay, where the river current is weak. In core ZJ-8 in the southwest of the bay, where seawater and river water interact, organic matter is characterized by mixture of terrestrial and aquatic origin. TOC/TN behaviors vary with organic matter sources. In core ZJ-6, TOC/TN ratios are depressed due to considerable proportion of inorganic nitrogen, and samples with lowest TOC contents are the most depressed. In core ZJ-7 and ZJ-8, the preferential degradation of nitrogen-rich organic matter may result in misleading TOC/TN source signature. Sedimented organic matter had a low accumulation rate and stable δ 13C before about the 1950s, but a high accumulation rate and variable δ 13C since the 1950s. Rapid economic development in the region of Pearl River delta, including Hong Kong and Macao, since the 1950s may give rise to the change.

Polycyclic aromatic hydrocarbons in sediments from the Pearl river and estuary, China: spatial and temporal distribution and sources

Polycyclic aromatic hydrocarbons (PAHs) were measured in surface sediments and dated core sediments from the Pearl river and estuary, China, to investigate the spatial and temporal variability of anthropogenic pollutants. The sediments from the sampling stations at the Guangzhou channel have the highest concentrations of PAHs, owing to contributions from the large amount of urban/industrial discharges from the city of Guangzhou. The significant decrease of PAHs concentrations in sediments from the Shiziyang channel is mainly attributed to the increasing degradation and desorption of low molecular weight PAHs and alkyl PAHs, and the dilution by less contaminated water and particles from the East river. The PAH contaminants were concentrated on the western side in the Lingding bay of the Pearl river estuary because of the hydrodynamic and sedimentation conditions. Based on the characteristics of the parent compound distributions (PCDs) and the alkyl homologue distributions (AHDs) of PAHs, the potential source of PAHs in sediments from each sampling station was identified. Results indicated that the pyrogenic (combustion) source, characterized by the abundance of parent PAHs, were predominant in the heavily contaminated station (ZB01) near the aging industrial area, and the petrogenic (petroleum- derived) PAHs were more abundant in the stations (ZB02, ZB03) adjacent to the petrochemical plant and shipping harbor. Sediments from Lingding bay show variable distributions of PAH composition and variety in the proportion of combustion and petrogenic sources for the PAHs in different stations. Perylene, a naturally derived PAH, was found to be highly abundant in less contaminated stations. Analysis of the dated sediments (210Pb) indicates that higher PAH concentrations occurred in the sediments deposited after 1980, and higher fluxes of PAHs discharged to the Pearl river are found after 1990.