Wanquan River Research Articles

Spatial Distribution and Contamination Assessment of Surface Heavy Metals off the Western Guangdong Province and Northeastern Hainan Island.

Surface sediments collected from the continental shelf off the western Guangdong Province and northeastern Hainan Island are analyzed for selected heavy metals contents including Cd, Cr, Cu, Pb, Zn, and As to determine spatial distribution, potential ecological risks, and sources. In addition, some of the controlling factors of heavy metals distribution are also discussed. The average heavy metals contents decrease in the order of Zn > Cr > Pb > Cu > As > Cd. The averaged pollution degree, as shown by the index of geo-accumulation (Igeo), decreases in the order of Zn > Cu > Pb > Cr > Cd > As. Due to the barrier of islands, the Igeo values of Zn, Pb, Cr, Cu, and Cd near the Hailing and Xiachuan Islands are larger than those in other areas. Meanwhile, the Igeo value of As near the coastal area off the estuary of Wanquan River is clearly larger than that in other areas. Based on the results of potential ecological risk index, Cd, Cu, and As should be paid more attention for the contamination risk in future. The results of Pearson correlation analysis and principal component analysis indicate that Zn, Cr, Pb, Cu, and Cd are mainly from the Pearl River and surrounding small rivers, whereas As originates from the Hainan Island. The grain size is one of the main controlling factors for heavy metals distribution, and the anthropogenic activity also plays an important role.

Pliocene seismic stratigraphy and deep‐water sedimentation in the Qiongdongnan Basin, South China Sea: Source‐to‐sink systems and hydrocarbon accumulation significance

This study uses high‐quality two‐dimensional (2‐D) seismic and well data to analyse seismic stratigraphy and deep‐water Pliocene sediments in the Qiongdongnan Basin (QDNB), South China Sea. Eight major seismic facies were identified based on the amplitude, continuity, configuration, and external geometry of seismic reflections. Among them, sigmoid progradational configurations, oblique progradational configurations, mound‐shaped chaotic configurations, and mound‐shaped hummocky configurations are newly identified seismic facies indicative of provenance and water system significance. They were interpreted as a Pliocene‐aged eastern shelf‐edge delta, a western shelf‐edge delta, and eastern and western submarine fans in QDNB. Consequently, two sets of Pliocene shelf‐edge delta‐continental slope canyon‐submarine fan systems were established in the QDNB. From the approximately NNW–SSE progradation of the shelf‐edge delta, the characteristics of the approximately ENE–WSW distributed continental slope system, and the definition of a source‐to‐sink system, as well as previous heavy mineral research, we conclude the existence of two Pliocene sources from Hainan Island in the northern QDNB, corresponding to the Lingshui River and Wanquan River. Two independent and complete source‐to‐sink systems (S2S‐2, S2S‐3) were distinguished from the northern Hainan Island to the basin area. S2S‐2 is located in the western QDNB, which includes the Lingshui River‐western shelf‐edge delta‐continental slope canyon‐submarine fan. This source‐to‐sink system has more sand‐rich material and better reservoir conditions than S2S‐3 in the eastern basin, predominantly due to a higher quality granite parent rock, abundant provenance, and a large‐scale delta and submarine fan.

The effect of wind on the dispersal of a tropical small river plume

Wanquan River is a small river located in Hainan, a tropical island in China. As the third largest river in Hainan, the river plume plays an important role in the regional terrigenous mass transport, coastal circulation, and the coral reef’s ecosystem. Studies have shown that wind forcings significantly influence river plume dynamics. In this study, wind effects on the dispersal of the river plume and freshwater transport were examined numerically using a calibrated, unstructured, finite volume numerical model (FVCOM). Both wind direction and magnitude were determined to influence plume dispersal. Northeasterly (downwelling-favorable) winds drove freshwater down-shelf while southeasterly (onshore) winds drove water up-shelf (in the sense of Kelvin wave propagation), and were confined near the coast. Southwesterly (upwelling-favorable) and north-westerly (offshore) winds transport more freshwater offshore. The transport flux is decomposed into an advection, a vertical shear, and an oscillatory component. The advection flux dominates the freshwater transport in the coastal area and the vertical shear flux is dominant in the offshore area. For the upwelling-favorable wind, the freshwater transport becomes more controlled by the advection transport with an increase in wind stress, due to enhanced vertical mixing. The relative importance of wind forcing and buoyancy force was investigated. It was found that, when the Wedderburn number is larger than one, the plume was dominated by wind forcing, although the importance of wind varies in different parts of the plume. The water column stratification decreased as a whole under the prevailing southwesterly wind, with the exception of the up-shelf and offshore areas.

Using zircon U–Pb ages to constrain the provenance and transport of heavy minerals within the northwestern shelf of the South China Sea

Numerous ore-grade heavy mineral placer deposits occur in the northern South China Sea region. Previous studies on these deposits have focused on the heavy-mineral ore resources themselves, but the provenance and transport pathways of these heavy minerals are poorly constrained. This paper presents U–Pb ages of detrital zircons from sediments within the northwestern shelf of the South China Sea, and uses this new dataset to determine the provenance and transport pathway of the sediments. Zircons in sediments from ten areas of the northwestern shelf exhibit distinct age populations, suggesting that they have multiple provenances. Zircons in sediments from the Pearl River Mouth, Shangchuan Island, and Moyang River Mouth areas all have an obvious peak of Mesozoic ages, indicating that they have similar sediment provenances; i.e., mainly from the Pearl River, and to a lesser degree from the Moyang River. Zircons in sediments from the areas around the Jian River Mouth and Leizhou Bay, and off Hainan Island have an early Paleozoic age, suggesting that the sediments predominantly originate from the Yunkai massif. Zircons of the sediments from the remaining four areas, the Leiqiong Strait, Wanquan River Mouth, Qiongdongnan, and the Outer Shelf, have Yanshannian and Indosinian age peaks in addition to an obvious early Paleozoic population, implying mixed provenances, including the Yunkai massif and Hainan Island. The sediment transport may have involved two hydrodynamic conditions in two distinct stages. First, the Guangdong Longshore Current carried the river sediments to where they dispersed in the inner shelf; subsequently, wave-induced strong currents further transported sandy sediments southeastward to the outer shelf. In addition to explaining the provenance and transport pathways of heavy minerals within the northwestern shelf of the South China Sea, these results provide new information relevant to exploration for heavy-mineral placer deposits.

Changes in the source of sedimentary organic matter in the marginal sea sediments of Eastern Hainan Island in response to human activities during the past 200 years

Marine sediments have been frequently used to reconstruct the records of environment change and human activities. We collected four sediment cores from Wanquan River estuary and the eastern continental shelf of Hainan Island in the South China Sea, and analyzed the down-core physical and chemical properties of sub-samples. Based on 210Pb dating, the longest core had a record of the most recent 200 years, while the other three profiles were slightly younger. The results show that both the TOC/TN ratios and fossil fuel-corrected organic δ13C of marine sediments for all four cores remained relatively constant before 1950 AD, indicating relatively stable sedimentary material sources. However, after 1950 AD, the TOC/TN ratios and organic δ13C in all four sediment cores displayed decreasing and increasing trends, respectively, indicating that the proportion of marine-derived material increased, whereas the land-derived materials that were mainly transported by the Wanquan River decreased. This is consistent with the obvious decrease in runoff and sediment discharges of the Wanquan River due to the increase in human activities, including industrial and agricultural production, and domestic water use in Hainan Island since 1950 AD. Therefore, we suggest that environmental changes on the land were recorded by changes in the source material of marine sediments collected from coasts and estuaries.

Provenance of heavy mineral deposits on the northwestern shelf of the South China Sea, evidence from single-mineral chemistry

Abstract A study of heavy mineral geochemistry has been carried out in order to examine the potential sources of heavy mineral deposits within surficial sediment on the northwestern shelf of the South China Sea. Tourmaline, amphibole and garnet from six samples near the coast and eleven samples on the shelf were analyzed by an electron microprobe. Chemical varieties of tourmaline and amphibole indicate that the Pearl River is the main supplier of sandy sediments on the eastern shelf within a 100 km radius west of the paleo-deltas. Sandy sediments on the western shelf are mainly sourced from the Jian River and the Wanquan River. Heavy mineral placers on the middle and outer shelves are mainly derived from reworking of the paleo Pearl River deltas. Heavy mineral placers in the west are mainly sourced from the small rivers and are distributed in the sandy deposits near the coasts. This study demonstrates that the occurrence of heavy mineral placers on wide continental shelf is mainly determined by the sediment supply and marine processes during transgressions.

Phytoplankton Dynamics and Its Further Implication for Particulate Organic Carbon in Surface Waters of a Tropical/Subtropical Estuary

Phytoplankton succession along with salinity in estuaries not only influences the riverine ecosystem but also interferes our understanding of riverine materials (e.g., organic carbon) transport to the sea. Four cruises were conducted in a mid-size river and its estuary (i.e., the Wanquan River) to elucidate the riverine phytoplankton decease along increasing salinity and to quantify the amount of algal particulate organic carbon (POC) present in the system at different seasons. CHEMTAX calculations suggested that chlorophytes were the main chlorophyll a (CHLa) contributor in the dissolved inorganic phosphorus-limited river, which contributed over 60 % of the total CHLa. Microscopy further revealed that the dominant species was Scenedesmus sp. In the estuary, phytoplankton succession along with salinity in the estuary was observed. Chlorophyte contribution to total CHLa dramatically decreased from over 60 % in the river (S = 0) segment to 20, suggesting the removal of riverine algae in the estuary. The mean algal POC concentration ranged from 80 μg/L (summer) to 140 μg/L (winter), and the riverine algal POC accounted for 6–56 % of the bulk riverine POC. The annual flux of riverine algal POC was estimated to be 660 tons.

拟平鳅头背部斑纹和下唇结构变异及其分类学意义

针对拟平鳅（<em>Liniparhomaloptera disparis</em>） 的两个亚种（<em>L. disparis disparis</em> 和<em>L. disparis qiongzhongensis</em>） 现有形态分类特征的含糊，通过观察标本室保存的15条水系441尾标本，首次提出利用下唇结构类型作为拟平鳅亚种的补充形态鉴别依据，结合头背部斑纹特征，能有效地鉴别拟平鳅各地理种群和亚种，为拟平鳅的分类和鉴定提供参考依据。依据头背部斑纹差异归纳出4种类型，分别为小斑块型（云开山脉以东的7条水系及海南岛万泉河），虫蚀纹型（云开山脉以西的5条水系），混合斑纹型（海南岛的万泉河、南渡江、昌化江共3条水系），大斑块型（海南岛的昌化江）。 依据下唇结构变化情况总结出3种下唇类型，分别是半圆型（云开山脉以西的5条水系），几字型（云开山脉以东的7条水系），马蹄型（海南岛的3条水系）。 依据头背部斑纹特征结合下唇结构特征，对照模式标本的描述，重新定义了拟平鳅原有的两个亚种，将分布于云开山脉以东水系的种群鉴定为指名亚种，拟平鳅<em>L. disparis disparis</em>，其鉴别特征为：头背部斑纹为小斑块型并且下唇类型为几字型； 将海南岛种群鉴定为琼中拟平鳅<em>L. disparis qiongzhongensis</em>，它们都具有独特的马蹄型下唇类结构，且头背部斑纹以混合斑纹型为主。重要的发现是，分布于云开山脉以西的种群与已命名的2个亚种在形态上有明显的差异，其头背部斑纹为独特的虫蚀纹型且下唇类型为半圆型。 这可能是一个新亚种。分子生物学方法也许能证明云开山脉以西的种群在遗传上的独特性以及形成新亚种的可能性。 云开山脉东、西两侧以及海南岛不同水系的拟平鳅的种群分化问题值得进一步探究。;Ambiguity of morphological characteristics made distinguishing the two subspecies of <em>Liniparhomaloptera disparis</em>(Cypriniformes: Homalopteridae) difficult. Further morphological evidence in infralabial shape and head spot pattern of the loach were herein provided for the first time to define the subspecies, based on laboratory observation of 441 specimens from 15 drainage systems, including the three western, northeastern, and eastern major rivers on Hainan Island. We recognized four head patterns of dark spots: small spots, vermiform spots, mixture of small and vermiform spots, and large spots. The small-spotted head pattern occurred in all seven populations east of the Yunkai Mountains, as well as in the only eastern population on Hainan Island. The vermiform-spotted head pattern occurred in all five populations west of the Yunkai Mountains. The mixed head pattern of small and vermiform spots occurred in both the western and northeastern populations on Hainan Island, but the large-spotted head pattern was also found in the western population. Additionally, we recognized three infralabial shapes: semicircular, subtrapezoidal, and horseshoe-like. The semicircular infralabium occurred in all five populations west of the Yunkai Mountains. The subtrapezoidal infralabium occurred in all seven populations east of the Yunkai Mountains. The horseshoe-like infralabium occurred in all three populations on Hainan Island. Therefore, populations east of the Yunkai Mountains had distinctly small-spotted head pattern and subtrapezoidal infralabia in combination, defined as the nominate subspecies <em>L. disparis</em> <em>disparis</em> according to the holotypic locality. Surprisingly; populations on Hainan Island were distinctly differentiated from the nominate mainlanders; all had uniquely the horseshoe-like infralabium, but the eastern population had small-spotted head pattern like the nominate mainlanders, the northeastern population had the mixed-spotted head pattern solely, and the western population had both the mixed-spotted and large-spotted head patterns. Based on the subspecific type locality(Wanquan River), we have redefined all three populations on Hainan Island that had mostly the mized-spotted head pattern and horseshoe-like infralabium in combination as the second subspecies <em>L. disparis</em> <em>qiongzhongensis</em>. Populations west of the Yunkai Mountains had distinctly the vermiform-spotted head pattern and semicircular infralabium in combination. This morphological variation may have resulted from the orogeny of the Yunkai Mountains. The differences in head spot pattern among populations on Hainan Island and the differences in infralabial shape either between mainland and Hainan Island or between east and west of the Yunkai Mountains suggest geographic isolation of rivers may have occurred long ago but at different times. This paper demonstrates the infralabial shape as a taxonomic character for the first time; this character in combination with the previous characters like head spot pattern can be used to identify subspecies or geographic populations effectively. Molecular analyses may prove the mainland populations west of the Yunkai Mountains and the populations on Hainan Island are genetically unique, new subspecies, and their geophylogenetic associations.

Development and characterization of thirteen polymorphic microsatellite markers in the fish Osteochilus salsburyi

Osteochilus salsburyi (Cypriniformes, Cyprinidae) is a small-sized fish of significant economic value. In this study, thirteen polymorphic microsatellite markers were developed in O. salsburyi and were examined on twenty individuals collected from the Wanquan River in the Hainan Island. The number of alleles (NA), polymorphism information content, observed and expected heterozygosity per locus ranged from 10 to 21, 0.8020 to 0.9354, 0.7500 to 1.0000 and 0.8436 to 0.9628, respectively. No locus was found to significantly deviate from Hardy–Weinberg equilibrium. These markers would be suitable for studies on conservation genetics and population structure of O. salsburyi.

Isolation and characterization of polymorphic microsatellite markers in the fish Garra orientalis (oriental sucking barb)

14 Polymorphic microsatellite markers were developed in the Garra orientalis. These new markers were tested in 23 individuals collected from the Wanquan River in the Hainan Island. The number of alleles (NA), polymorphism information content, observed and expected heterozygosity per locus ranged from 8 to 25, 0.6788 to 0.9342, 0.5652 to 1.0000 and 0.7179 to 0.9585, respectively. Four loci are deviated from Hardy–Weinberg equilibrium due to the heterozygote deficiency. These markers can be used to study genetic diversity, population structure, conservation and rational utilization of this species.

Biogeochemical behavior of organic carbon in a small tropical river and estuary, Hainan, China

The biogeochemistry of a small tropical river and estuary (the Wanquan River (WQR)) in Hainan, China, was studied to obtain information on the sources, transformation and fate of riverine organic matter. Water and total suspended matter were sampled along a salinity gradient during four field campaigns in December 2006, August 2007, July–August 2008 and April 2009. We were able to observe the effect of heavy precipitation associated with the tropical cyclone Kammuri (2008) and a strong first-rain event (2009) on the export of organic carbon. Both dissolved organic carbon (DOC) and particulate organic carbon (POC) generally decreased with increasing salinity in the estuary, with minimal seasonal or annual variations. The POC concentrations were in the range of 18–178μM for the WQR and were significantly correlated with chlorophyll a concentrations. The highest average values of DOC (∼190μM) were observed in 2009. These values could be the result of the flushing effect of the first rain. In the high-salinity zone, in situ productivity could be an important source for DOC. The δ13Corg values of particles (−29.5‰ to −23.2‰), combined with the ratio of organic carbon to total nitrogen (OC/TN), reflect a mixture of terrestrial organic matter and in situ production. The amplitudes of the POC and DOC variations on the occasion of the first-rain event of 2009 were larger than those observed during Kammuri. It is estimated that 29.8tday−1 of DOC and 10.4tday−1 of POC, representing 6–10% of the annual loads, were delivered to the coast during the 10-day period of the first flush event in 2009. Our results demonstrate the important role of short-term aperiodic events on small rivers and estuaries along tropical coasts.

Estuarine modification of dissolved and particulate trace metals in major rivers of East-Hainan, China

Dissolved and particulate cadmium, copper, iron, lead, cobalt and nickel were analyzed in surface waters of the Wanquan River estuary and the Wenchang/Wenjiao River estuary in East-Hainan Island during the dry season (December 2006) and two wet seasons (August 2007 and July/August 2008). A major difference to other Chinese rivers was the very low concentration of suspended particles in these tropical Hainan estuaries. In the dissolved phase, a positive deviation from the theoretical dilution line was observed for Cd during different expeditions. Dissolved Cu and Ni essentially behaved conservatively, while Fe, Pb and partly also Co correlated in their negative deviation from simple mixing. Strong seasonal variability was observed only for dissolved Fe, Pb and Cd: sorption by the much higher loading with suspended particles during the dry season lead to a strong lowering of dissolved Fe and Pb, while the opposite was observed for dissolved Cd. In both estuaries all six metals in particulate form showed almost constant values with a tendency for slight decreases along the salinity profile. The normalization to particulate Al revealed some specific particle properties during the different expeditions. The dynamics of Fe chemistry dominated the distribution of Pb in all forms. The distribution coefficients KD showed a general decrease in the order Fe>Pb>Co>Ni>Cu≈Cd. There was no “particle concentration effect”; rather the KD’s of Fe and Pb exhibited slightly positive correlations with the suspended particle loadings. Elevated concentrations levels in the Wenchang/Wenjiao river estuary, especially during the wet season 2008, were ascribed to diffuse inputs from aquaculture ponds which girdle the upper estuary. In comparison to major Chinese rivers, the tropical Hainan estuaries (S>0) showed similar levels for Cd, Cu, Pb, Co and Ni in particles and solution, while Fe was enriched in both matrices. On a global scale, neither in the Wanquan river estuary nor in the Wenchang/Wenjiao river estuary significant trace metal contamination was observed.

Arsenic in solution, colloidal and particulate phases of East-Hainan estuaries

During two nominal dry seasons (December 2006, March 2009) and two wet seasons (July 2007, July/August 2008) the estuarine distribution and size speciation of arsenic was studied in the Wanquan river and the Wenchang/Wenjiao river estuaries, located in tropical East-Hainan (China). Arsenic in solution and in colloidal fractions was analyzed by anodic stripping voltammetry after oxidative UV digestion thereby including inorganic As(III) and As(V) as well as organic As forms. Particulate As was determined by high-resolution ICP-MS after a microwave assisted total decomposition protocol. Taking the two relatively similar estuaries and the two expeditions for each season together, the average concentrations of total dissolved As (<0.4μm; td-As) of the freshwater endmember were 4.4nM and 7.6nM during the dry and the wet seasons, respectively, which suggests a low – if ever – level of contamination. With one exception (uptake by phytoplankton in the lower estuary), during the dry season td-As increased essentially conservatively along the salinity gradient to 14.4nM as the mean value for salinities of about S=30. During the wet seasons, however, td-As only showed a tendency for a conservative increase; scatter in the data was attributed primarily to heavy rain and side inputs of variable As concentrations from overflowing aquaculture ponds and piles of excavated soil. The separation of colloidal fractions revealed that on average 82% of td-As remains in solution (<5kDa), followed by 13% in small colloids (5kDa to 30kDa) and 5% in large colloids (30kDa–0.4μm). Particulate As (0.24±0.06μmol/g) showed no dependence on either salinity, suspended particles, estuary or season. Relatively high distribution coefficients (logKD=4.48–4.81 in the freshwater; logKD∼4.18 at high salinities) arose primarily from the very low td-As. Except for certain impacts from aquaculture ponds, the two estuaries might be considered uncontaminated with respect to As.

Biogeochemistry of nutrients in an estuary affected by human activities: The Wanquan River estuary, eastern Hainan Island, China

Nutrient dynamics were studied in the estuary of the Wanquan River, a tropical mountainous river system of Hainan Island, China, during 2006–2009. The nutrients measured included NO3−, NO2−, NH4+, PO43−, Si(OH)4, total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), dissolved organic nitrogen (DON), and dissolved organic phosphorus (DOP). The Wanquan River showed great variation in nutrient levels, was enriched in dissolved inorganic nitrogen (DIN) and dissolved silicate, and depleted in PO43−. The levels of dissolved silicate were higher than average for tropical systems. As a consequence the DIN:PO43− and Si(OH)4:DIN ratios were higher than the Redfield ratio. DON accounted for 18% of TDN in the Wanquan River, and DOP represented approximately 61% of TDP.Nutrients in the Wanquan River estuary behave either conservatively or nonconservatively. Nutrient biogeochemistry in the estuary is affected by human activities in adjacent areas and heavy rainfall associated with typhoons. Phosphorus may be the potential limiting nutrient for phytoplankton growth. A simple steady-state box model showed that riverine input was the major source of nutrients to the estuary, which acted as a source of all nutrients except dissolved silicate, TDP, and DOP. The results indicate that substantial quantities of nitrogen and PO43− are transported to the coastal system, and suggest that dissolved silicate accumulates in the sediment or is transformed into other forms.

An examination of groundwater discharge and the associated nutrient fluxes into the estuaries of eastern Hainan Island, China using 226Ra

The nutrient concentrations and stoichiometry in a coastal bay/estuary are strongly influenced by the direct riverine discharge and the submarine groundwater discharge (SGD). To estimate the fluxes of submarine groundwater discharge into the Bamen Bay (BB) and the Wanquan River Estuary (WQ) of eastern Hainan Island, China, the naturally occurring radium isotope ( 226Ra) was measured in water samples collected in the bay/estuary in August 2007 and 2008. Based on the distribution of 226Ra in the surface water, a 3-end-member mixing model was used to estimate the relative contributions of the sources to these systems. Flushing times of 3.9 ± 2.7 and 12.9 ± 9.3 days were estimated for the BB and WQ, respectively, to calculate the radium fluxes for each system. Based on the radium fluxes from groundwater discharge and the Ra isotopic compositions in the groundwater samples, the estimated SGD fluxes were 3.4 ± 5.0 m 3 s −1 in the BB and 0.08 ± 0.08 m 3 s −1 in the WQ, or 16% and 0.06%, respectively, of the local river discharge. Using this information, the nutrient fluxes from the submarine groundwater discharge seeping into the BB and WQ regions were estimated. In comparison with the nutrient fluxes from the local rivers, the SGD-derived nutrient fluxes played a vital role in controlling the nutrient budgets and stoichiometry in the study area, especially in the BB.

Particle dynamics of 7Be, 210Pb and the implications of sedimentation of heavy metals in the Wenjiao/Wenchang and Wanquan River estuaries, Hainan, China

Radionuclides (i.e., 7Be and 210Pb) can be used to trace particle and sediment dynamics and to quantify coastal oceanic processes with time scales ranging from a few days to a hundred years. Here, we study the settling dynamics of suspended particles and the implication by sedimentary heavy metals in the Wenjiao/Wenchang River and Wanquan River estuaries through the measurement of the particulate 7Be and 210Pb nuclides. Activity in the particulate phase had a range of 2.1–54.5 and 4.6–67.9 Bq kg −1 for 7Be and excess 210Pb ( 210Pb xs), respectively, in the Wenjiao/Wenchang River estuary. In the Wanquan River estuary, activity is in the range of 1.2–43.5 Bq kg −1 for 7Be and 6.2–194.5 Bq kg −1 for 210Pb xs. At the same time, activity in the dissolved phase had a range of 0.46–1.26 and 0.30–1.17 Bq m −3 for 7Be and 210Pb, respectively, in the Wenjiao/Wenchang River estuary; ranges of 0.10–2.31 and 0.09–1.87 Bq m −3 for 7Be and 210Pb, respectively, were observed in the Wanquan River estuary. The distribution coefficients ( K d ) for the two nuclides decreased within increased in suspended particle matters (SPM) concentration and/or salinity in Wanquan River estuary. The residence times of particulate 7Be and 210Pb xs had ranges of 0.4–1.6 and 1.65–5.15 days, respectively, in the Wenjiao/Wenchang River estuary; and ranges of 0.02–3.2 and 0.61–4.44 days, respectively in the Wanquan River estuary. All residence times for the two nuclides increased in the seaward direction. In the Wenjiao/Wenchang River estuary, we found that 11.8–21.0% of Cu, 3.0–9.0% of Zn and 43.2–69.9% for Cd is removed from the water column and deposited into the estuary, and 24.2–34.8% for Cu, 7.2–23.8% for Zn, and 70.0–82.5% for Cd in the Wanquan River estuary, respectively.

An Invasive Species Red-eared Slider (&lt;i&gt;Trachemys Scripta Elegans&lt;/i&gt;) Carrying &lt;i&gt;Salmonella&lt;/i&gt; Pathogens in Hainan Island

The red-eared slider ( Trachemys scripta elegans ) is a semiaquatic turtle belonging to the family Emydidae. It is native to the southern United States, but has become established in other places because of pet releases. It is the most popular pet turtle in the United States and also popular in the rest of the world. In China the red-eared slider listed as an invasive and quarantinable species due to carring the Salmonella pathogens. In this research we collected 68 individuls of the wild red-eared sliders from Nandujiang (Nandu river), Wanquanhe (Wanquan river) and Haikoudonghu (East Lake of Haikou City) in Hainan island of the most southern of China. We sampled the tissue and mucus from from cloacae of the red-eared sliders used for Salmonella bacterial culture to observe its morphology, biochemical characteristics and serotypes. The result showed that the total carrier rate of Salmonella carring in the tested red-eared sliders reach 54.41% (n=68), of which the carrier rate in Nandujiang is 53.85% (n=26), in Wanquanhe 58.82%(n=34),and Haikoudonghu 50% (n=8). The serotypes of Salmonella in the tested red-eared sliders were indentified to be S. litchfiled , S. chailey , S. senftenberg , and S. Stanley . In this research we strong suggested that the wild red-eared slider carrying Salmonella pathogens in Hainan island be potential dangerous impact on the ecological system and island resident.

Interannual variation of rare earth element abundances in corals from northern coast of the South China Sea and its relation with sea-level change and human activities

Here we present interannual rare earth element (REE) records spanning the last two decades of the 20th century in two living Porites corals, collected from Longwan Bay, close to the estuarine zones off Wanquan River of Hainan Island and Hong Kong off the Pearl River Delta of Guangdong Province in the northern South China Sea. The results show that both coral REE contents (0.5–40 ng g −1 in Longwan Bay and 2–250 ng g −1 in Hong Kong for La–Lu) are characterized with a declining trend, which are significantly negative correlated with regional sea-level rise (9.4 mm a −1 from 1981 to 1996 in Longwan Bay, 13.7 mm a −1 from 1991 to 2001 in Hong Kong). The REE features are proposed to be resulted from seawater intrusion into the estuaries in response to contemporary sea-level rise. However, the tendency for the coral Er/Nd time series at Hong Kong site is absent and there is no significant relation between Er/Nd and total REEs as found for the coral at Longwan Bay site. The observations are likely attributed to changes of the water discharge and sediment load of Pearl River, which have been significantly affected by intense human activities, such as the construction of dams/reservoirs and riverbed sediment mining, in past decades. The riverine sediment load/discharge ratio of the Pearl River decreased sharply with a rate of 0.02 kg m −3 a −1, which could make significant contribution to the declining trend of coral REE. We propose that coastal corals in Longwan Bay and similar unexplored sites with little influences of river discharge and anthropogenic disruption are ideal candidates to investigate the influence of sea-level change on seawater/coral REE.

The coast evolution and regulation in Wanquan River Estuary, Hainan Island

In this paper, sediment samples were collected along the Wanquan beaches and sieved in the laboratory in order to obtain the grain size distributions and associated parameters, i.e. mean grain size, sorting coefficient and skewness. Furthermore, we have calculated the longshore drift sediment transport rates and equilibrium cross-sectional areas of the entrance channel by using the method of sedimentary dynamics. The results indicate that the longshore drift sediment transport is dominated by waves with a direction from south to north, which result in rapid changes of the entrance channel. Therefore, some suggestions were proposed for improving the water quality and restoring the ecosystem of estuary. The engineering method includes increasing the sea-route of entrance channel, tidal prism and water exchanges in Shamei Lagoon.

Change in the sedimentary environment of Wanquan River Estuary, Hainan Island, China

210Pb geochronology and sediment core profiles of organic carbon, total sulfur and organic carbon isotope (δ13C) values were used to reconstruct the local environmental history of the Shamei Lagoon, located in the Wanquan River Estuary, eastern Hainan Island, China. Total sulfur and δ13C values decreased upwards in the top 30 cm of a sediment core that spanned the last 200 years of deposition. Total sulfur concentration and δ13C values respectively decreased upward from 1.92% to 0.36%, and −20.63‰ to −23.64‰ The C/S ratio in the 19th century and earlier was relatively stable in the range of 0.47–0.80, and there was a positive correlation between organic carbon and total sulfur. Since around 1900 AD, the C/S ratio increased rapidly to a maximum of 3.94, but no simple correlation was found between organic carbon and total sulfur during this more recent period. These results indicated that before 1800 AD, the lagoon had a fully marine character, and the location of today’s Wanquan River Estuary was an open embayment. From 1800 to 1900, the salinity of Shamei Lagoon decreased noticeably. The amount of seawater which could enter the lagoon decreased gradually as the Yudai spit grew. Today, seawater scarcely affects the lagoon; it is essentially a freshwater basin.