Comparison of HTC method and UV/persulphate method to determine colloidal organic carbon in seawater

ＩＮＴＲＯＤＵＣＴＩＯＮＣｏｌｌｏｉｄｓａｒｅａｂｕｎｄａｎｔｉｎｓｅａｗａｔｅｒ(Ｋｏｉｋｅ,1 990 ;ＷｅｌｌｓａｎｄＧｏｌｄｂｅｒｇ,1 991 ;1 992 ) ,ａｎｄａｌａｒｇｅｆｒａｃ ｔｉｏｎｏｆｄｉｓｓｏｌｖｅｄｏｒｇａｎｉｃｃａｒｂｏｎｉｎｓｅａｗａｔｅｒｉｓｃｏｌｌｏｉｄ.Ｔｈｉｓｆｒａｃｔｉｏｎｏｆｄｉｓｓｏｌｖｅｄｏｒｇａｎｉｃｃａｒｂｏｎｐｌａｙｓａｎｉｍ ｐｏｒｔａｎｔｒｏｌｅｉｎｔｈｅｂｉｏｇｅｏｃｈｅｍｉｃａｌｃｙｃｌｉｎｇｏｆｏｒｇａｎｉｃｃａｒｂｏｎａｎｄｔｒａｃｅｍｅｔａｌｓｉｎ…     

DISSOLVED AND PARTICULATE ORGANIC CARBON IN YANTAI SISHILI BAY AQUICULTURE WATERS

Investigation of dissolved organic carbon (DOC) and particulate organic carbon (POC) at 12 stations in Yantal Sishili Bay in May, August, and November of 1997 and March and May of 1998 showed that DOC concentrations varied from 1.14 mg/L to 5.35 mg/L; that the average values at all staticrLs ineach entise varied from 1.52 mg/L to 2.12 mg/L; that POC concentrafions varied from 0.049 mg/L to 1.411mg/L; and averaged 0.159 mg/L to 0.631 mg/L in each cruise. Horizontal distribution of DOC was influ-enced by factors such as continental input, organism activity, temperature, aquieulture environment, etc. The higher POC concentration occurred along the coast. The vertical distribution of DOC and POC changed obviously in spring and summer, but not obviously in autumn and winter. DOC concentration was highest in summer and POC in spring; both were lowest in winter. The seasonal change of DOC was con-sistent with primary productivity seasonal variation, and that of POC was consistent with ehlorophyll-a sea-sanal variation. The seasonal change trend of the C/N ratio of dissolved organic matter was obvious, but the C/N ratio of particulate organic matter had no such trend.     

The effects of estuarine processes on the fluxes of inorganic and organic carbon in the Yellow River estuary

Riverine carbon flux is an important component of the global carbon cycle. The spatial and temporal variations of organic and inorganic carbon were examined during both dry and wet seasons in the Yellow River estuary. Concentrations of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in the Yellow River during dry seasons were higher than those during wet seasons. The effective concentrations of DOC (C_DOC*) were higher than the observed DOC at zero salinity. This input of DOC in the Yellow River estuary was due to sediment desorption processes in low salinity regions. In contrast to DOC, the effective concentrations of DIC were 10% lower than the DIC measured at freshwater end, and the loss of DIC was caused by CaCO₃ precipitation in low salinity region. Particulate organic carbon (POC) and particulate inorganic carbon (PIC) contents of the particles stabilized to constant values (0.5%±0.05% and 1.8%±0.2%, respectively) within the turbidity maximum zone (TMZ) and showed no noticeable seasonal variations. A rapid drop of PIC and rise of POC occurred simultaneously outside the TMZ due to an intense dilution of riverine inorganic-rich particles being transported into a pool of aquatic organic-poor particles outside the TMZ. Annually, the Yellow River transported 6.95×10⁵ t of DIC, 0.64×10⁵ t of DOC, 78.58×10⁵ t of PIC and 2.29×10⁵ t of POC to the sea.     

Seasonal changes of dissolved and particulate organic carbon in Donghu Lake, China

Concentrations of dissolved and particulate organic carbon (DOC and POC) were documented in 1996–1997 at 4 different trophic state stations in Donghu Lake, a typical shallow eutrophic lake along the Changjiang River's middle reaches. The mean concentrations of DOC were 15.11±3.26, 15.19±4.24, 14.27±3.43, and 13.31±3.30 mg/L in Station I, II, III, and IV, respectively. The DOC concentrations of the studied area were very similar to that in other lakes along the Changjiang River's middle reaches. The POC mean of the whole lake was 5.01 mg/L due to the large amount of organic detritus of both allochthonous and autochthonous origin. Significant linear relationship was found between POC and chlorophyll a at all 4 stations, which presumably reflect that phytoplankton, its exudates and its metabolic products were the main contributors to the POC pool in the water column. The slope of such linear relationship at Station IV was significantly steeper than that at Station I, II and III. In addition, the DOC/POC ratios (mean value: 4.40) indicated that the organic detritus was the most important component of the particulate organic matter; in other works, next to organic detritus, phytoplankton dominated the particulate organic matter in Donghu Lake. Project 39770146, 39430101 supported by NSFC and the State Key Laboratory of Freshwater Ecology and Biotechnology, affiliated to the Institute of Hydrobiology, Chinese Academy of Sciences.     

Distribution and Sources of Polycyclic Aromatic Hydrocarbon （PAH） in Marine Environment of China

1INTRODUCTIONPolycyclicaromatichydrocarbons (PAHs)depo sit edinmarineenvironmentsfromavarietyofsourcessuchaswastewater,industrialanddomesticdischarges,andoilspills.Themajorityofthesesourcesfrompetrogenicoriginischaracterizedbyadominanceoflowmolecularweightaromaticcompounds,especiallynaphthaleneandalkylatedPAHs(Sportoletal.,1 983 ) .Crudeoilanditsrefinedproductssuchasgasoline,keroseneandotherfu eloilshaveahighcontentofalkylatedPAHsduetotheirslowformationattemperatureslowerthanthatofcomb…     

Measurement of Labile Cu, Pb and Their Complexation Capacity in Yueqing Bay in Zhejiang Province, China

1　INTRODUCTIONRecently ,thepollutionoftracemetalinseawaterhasbecomeincreasinglyevident.Researchershavefo cusedattentiontotracemetalpresentinvariousexistenceforms ,especiallyorganiccomplexingphases.Theexistencestatesandtransportmechanismofbaytracemetalswerethesubjectofstudybysomere searchers(Gu ,1 991 ;Florence ,1 998;Guo ,1 998;Wells,1 991 ,1 998a ,b ;Wellsetal.,1 998) .Whetherinfreshwaterorseawater,colloidsareclearlydominantfactorsaffectingtheexistencestatesandtransportmechanismoftrac…     

Study on Dissolved Trace Metals in Sea Surface Microlayer in Daya Bay

Glass-plate sampling during 1988- 1999 in Daya Bay and suitable corresponding analytical methods were used for the measurement of dissolved trace metals, dissolved organic carbon, biological oxygen demand, chemical oxygen demand, salinity of the sea surface mierolayer and subsurface water. Apparent enrichment mechanism and diurnal variation have been revealed for dissolved trace metals in the microlayer in Daya Bay. The more dissolved organic matter was enriched in the sea surface microlayer, the more dissolved trace metals were enriched in the layer. The organic matter played an important role in the enrichment process. The diurnal variations of dissolved trace metals showed that their concentration was apparently inversely related to the tide activity that the concentration was low during rising tide, but high during falling tide. The behavior of dissolved trace metals expressed by the diurnal variation was clearly opposite to that of salinity.     

Densities of Huanghe River estuary and Bohai Bay waters

The densities of 36 water samples from the Huanghe River estuary and Bohai Bay were determinedby a magnetic float densimcter under three temperatures from 15℃ to 25℃.All the measured densities ofsamples were greater than that of the values calculated from the International Equation of State of Seawater.The differences between the measured and calculated densities increased with the decrease of salinities.The dif-ferences appeared exponentially correlated with[Ca~(2+)]/s,[Mg~(2+)]/s and[SO_4~(2-)]/s,and had"s"type curverelationship with the alkalinity in all salinity range.But in the salinity ranging from 25.72 to 31.57,therelationships were all linear.The density difference can be estimated from the equation △ρ（10~3kg·m~(-3)）=（-2.79+236.5([Ca~(2+)]/s)/(-9.7464×10~（-3）+[Ca~(2+)]/s).It was the high alkalinity and[Ca~(2+)]/s that resulted in the measured densi-ties of seawaters being higher than the calculated densities in the Huanghe estuary and Bohai Bay.     

Temporal and spatial variability of dissolved organic carbon concentration in the Xijiang River, South China

A whole year analysis of riverine dissolved organic carbon (DOC) concentrations in the Xijiang River (XJR), South China, showed that the mean riverine DOC concentration (1.24 mg L-1) in the XJR was notably lower than the averaged value (5.75 mg L-1) of the global riverine DOC concentration in several major rivers. There is an inconspicuous monthly fluctuation of the DOC signal in the XJR, but on a semi-yearly time scale, however, the riverine DOC concentration had significant difference between hydrological...     

Spatial distribution and diurnal variation of chemical oxygen demand at the beginning of the rainy season in the Changjiang （Yangtze） River Estuary

A field observation was carried out in the Changjiang （Yangtze） River Estuary from May 19 to 26, 2003. A total of 29 stations, including 2 anchored stations, were occupied through almost the whole salinity gradient. Based on the observation data, biogeochemistry of chemical oxygen demand （COD） was examined. Spatial distribution pattern of COD shows that it decreased downstream. The COD concentration varied generally within a narrow range of 1.24-1.60 mg/L in the zone around the river mouth, beyond which it decreased rapidly to 0.20 mg/L. In the mixed water zone, the fluctuation in COD was smaller at 2 m above the bottom layer than at the surface layer in 48 h. In the seawater zone, the 48-h fluctuation at the surface was the largest, followed by that of 5 m below the surface and 2 m above the bottom layers in a range of from 2.50 to 0.55 mg/L. Freshwater discharge was the dominant source of COD in the estuary. The average COD beyond the river mouth was 2.7 mg/L, which accorded with the Chinese seawater quality Grade I. Relationships between dissolved oxygen and biogeochemical parameters such as suspended particulate matter, dissolved organic matter and chlorophyll-a were also discussed.     

Seasonal variations of riverine organic carbon contents in Makou and Hekou gauge stations of the Zhujiang River, China

Water samples were collected and analyzed in high water season (July 1997) and in middle water season (October, 1997) from two main lower reach gauge stations of the Zhujiang (Pearl) River, namely Hekou and Makou, respectively. Content of particulate organic carbon is always higher than that of dissolved organic carbon in both seasons, which is obviously different from the global average pattern, i.e. dissolved organic carbon is the dominant component of the transported riverine organic carbon. The content of dissolved and particulate organic carbon changes with the water levels in a direct ratio. The percentage of organic carbon in total suspended substance changes with the content of total suspended substance in an inverse ratio. The more intense is the soil erosion in the drainage, the more concentrated is the riverine organic carbon in the river. The contribution of autochthonous organic carbon is large in high water season than in middle water season. Fundation item: This project was supported financially by the National Natural Science Foundation of China (No. 49901002), the key funds of resources and eco-environmental research of the CAS (No. KZ952-J1-402), a funds of the state key laboratory of organic geochemistry, and Guangdong Province Science Funds (No. 984131). Biography: Gao Quan-zhou (1965 —), male, a native of Anhui Province, associate professor. His research interests are geomorphology and Quaternary geochemistry.     

Chemical characterization and composition of dissolved organic matter in Jiaozhou Bay

Biologically utilizable dissolved organic compounds, including dissolved organic carbon (DOC), dissolved carbohydrates (DCHO) and dissolved free amino acids (DFAA) were analyzed in filtered surface seawater samples collected at 19 stations in Jiaozhou Bay, China, on June 3, 2007. In these samples, concentrations of DOC, dissolved free carbohydrates (DFCHO), dissolved combined carbohydrates (DCCHO), total dissolved carbohydrates (TDCHO) and total dissolved free amino acids (TDFAA) ranged from 141.7 to 191.1 μmol C/L, 1.98 to 18.18 μmol C/L, 5.04 to 24.90 μmol C/L, 14.52 to 30.36 μmol C/L, and 1.83 to 11.89 μmol C/L, respectively. As a major component of the dissolved carbohydrates, the concentrations of DCCHO were about three times higher than those of DFCHO. Three major constituents of the DFAA were threonine (23.0±5.7 mol%), glutamic acid (16.6±3.2 mol%) and arginine (9.1±3.3 mol%). Based on the composition of DFAA, a molar C:N ratio of 3.60±0.75 in DFAA was derived, indicating longer carbon chains in the amino acids. DCCHO (8.1%) was the most abundant fraction of DOM in most samples, followed by DFCHO (4.8%) and TDFAA (2.7%). These DOM concentrations displayed a decreasing trend from the coast to the central region. Significant correlations were found between the DCCHO and DFCHO concentrations (r=-0.724, n=19, P<0.001) and the DCCHO and TDCHO concentrations (r=0.506, n=19, P=0.027).     

Biochemical studies on “sub-micrometer particles” at Daya Bay I. Study on concentration, distribution and correlation of trace metals in different size fractions

This paper discusses the measured concentrations of trace metals in different size fractions at Daya Bay, and describes the features of distribution and variation of lead, copper and cadmium there. On average, 16% of Pb, 10% of Cu and 8% of Cd which previously would have been considered in the dissolved phase are actually associated with colloidal material. Thus, past studies overestimate the dissolved trace-metal concentration. The correlation between the colloidal fraction and the so-called dissolved fraction suggests the significant role of colloidal material in the biogeochemistry of trace metals. Project supported by the National “Ninth-Five-Year Plan” Special Project (No.97-926-04-03) and “KZ95T-04-04-04” Fund.     

Effects of land management practices on labile organic carbon fractions in rice cultivation

A research trial with four land management practices, i.e., traditional tillage-fallow (TTF), traditional tillage-wheat (TTW), conservation tillage-fallow (CTF) and conservation tillage-wheat (CTW), was sampled in the 15th year after its establishment to assess the effects of different management practices on labile organic carbon fractions (LOCFs), such as easily oxidizable organic carbon (EOC), dissolved organic carbon (DOC), particulate organic carbon (POC) and microbial biomass carbon (MBC) in a typical paddy soil, Chongqing, Southwest China. The results indicated that LOCFs were significantly influenced by the combination of no-tillage, ridge culture and crop rotation. And, different combination patterns showed different effectiveness on soil LOCFs. The effects of no-tillage, ridge culture and wheat cultivation on EOC, DOC, POC and MBC mainly happened at 0–10cm. At this depth, soil under CTW had higher EOC, DOC, POC and MBC contents, compared to TTF, TTW and CTF, respectively. Moreover, the contents of LOCFs for different practices generally decreased when the soil depth increased. Our findings suggest that the paddy soil in Southwest China could be managed to concentrate greater quantities of EOC, DOC, POC and MBC. Foundation item: Under the auspices of Key Project of National Natural Science Foundation of China (No. 40231016)     

Carbon dioxide partial pressure and carbon fluxes of air-water interface in Taihu Lake, China

1 INTRODUCTION Carbon dioxide (CO2) is principal greenhouse gas. Its air-water exchange is important in terrestrial ecosystems for climate change (Frankignoulle et al., 1998; Schimel et al., 2001). The direction of CO2 gas movement depends on the CO2 concentration gradient between air and surface water. The amount of CO2 exchange is related to the gas exchange coefficient, k. All lakes, with their small area but large atmospheric CO2 flux are important to under-stand the CO2 fluxes …     

Distributions of inorganic nutrients in the bohai sea of china

1　Introduction　TheBohaiSeaislocatedinthenorthernChinawithlongitudesofbetween 117°38′Eand 12 2°31′Eandlat itudesofbetween 37°0 8′Nand 4 1°0 2′N .Itisashal lowseawithanaveragewaterdepthof 18m (LiuandZhang ,2 0 0 0 ) .Severalbigrivers ,suchastheLiaoheRiver,theHaiheRiverandtheYellowRiver ,findtheirwaysintotheBohaiSeaandtransportlargeamountofnutrientsandsuspendedmattersfromthecontinentintothesea (Zhangetal.,1994 ;Zhang ,1996 ) .Duringthelasttwodecades ,marineenviron mentintheBohai…     

The biogeochemistry of carbon cycle in summer of the Prydz Bay,Antarctic Ⅰ :Characteristics of DOC distribution

The distributions and changes of dissolved organic carbon in the Prydz Bay and out open sea were investigated during CHINARE-15 ( the 15th Chinese National Antarctic Research Expedition). The results showed that the content of DOC was higher in the Prydz Bay and outer open sea compared to those typical of surface oceanic levels ( 70-80 μM) , average content of DOC in the surface water was 102.32 μM,the range was 68.23-125.92 μM. The vertical distribution of DOC in the water column was similar to many ocean sites, that is to say, the content of upper water is higher than deep water, a subsurface maximum persisted between 25-50 m. The DOC pool in the Prydz Bay were consisted with labile, semi-labile and refractory pools, in which refractory pools was mainly part. The concentration of refractory DOC was 92.34 and 76.89 μM in Prydz Bay and outer open sea, and account 77% and 82% for total DOC, respectively.     

Terrestrial dissolved organic carbon consumption by heterotrophic bacterioplankton in the Huanghe River estuary during water and sediment regulation

Nearly 20%-50% of the annual terrestrial dissolved organic carbon(DOC) from the Huanghe(Yellow) River was transported to the estuary during the 5-14 d of water and sediment regulation. The concentration of DOC increased sharply during the period of water and sediment regulation, which may promote the terrestrial DOC consumption by heterotrophic bacterioplankton. Water and sediment regulation provides an ideal condition for the study of terrestrial DOC consumption by heterotrophic bacterioplankton when terrestrial DOC increases sharply in rainy season, which may help to seek the fates of terrestrial DOC in the estuaries and coasts. In this study, the concentration and stable isotope of DOC, the biomass,growth, and respiration of heterotrophic bacterioplankton were determined. By the study, we found both average percent contribution of terrestrial DOC to the DOC pool and Contribution of terrestrial DOC to the carbon composition of heterotrophic bacterioplankton decreased as distance from the river mouth increased offshore, which was deceased from(39.2±4.0)%,(37.5±4.3)% to(30.3±3.9)%,(28.22±3.9)%respectively. 255-484 μg C/(L·d) terrestrial DOC was consumed by heterotrophic bacterioplankton. And 29%-45% terrestrial DOC consumed by heterotrophic bacterioplankton releasing as CO_2 by respiration.Comparing with tropical estuary, terrestrial DOC consumed by heterotrophic bacterioplankton was lower in temperate estuary(this study). Temperature may limit the consumption of terrestrial DOC by heterotrophic bacterioplankton.     

Nutrients in seawater and interstitial water of the sediments in the Huanghe River estuarine area (November)

The investigation shows that the concentrations of nutrients are high in estuarine and coastal waters and low in offshore waters. The concentration of nitrate in estuaries is controlled through a physical mixing process and is also affected by biotic activity. The annual transport of total inorganic nitrogen and dissolved phosphate-phosphorus from the Huanghe River water to the sea is about 8.45 ×10⁴ and 1.45×10³ tons respectively. The distributions of inorganic nitrogen and silicate in interstitial water of surface sediments are similar to those in surface and bottom seawater. Their contents in interstitial water are 227–552 μmol/l (average375) for ammonia, 0.31–9.0 μmol/l (average 1.6) for nitrite, 0–41 μmol/l (average6.0) for nitrate, and 41–139 μmol/l (average 77) for silicate. The average concentrations of phosphate in the surveyed area are 0.64 μmol/l for seawater and 1.2 μmol/l for interstitial water. A cycle of phosphate in the estuary is also suggested in this paper. Contribution No. 1434 from Institute of Oceanology, Academia Sinica.     

Estimation of total suspended matter in the Zhujiang (Pearl) River estuary from Hyperion imagery

Although remote sensing data have been used to estimate total suspended matter (TSM) in coastal waters, it has limitations when applied to estuary waters in low spatial resolution situations. The spatial resolution of ocean color satellites such as SeaWiFS and MODIS is usually ～1 km, and therefore is not adequate for small, local-scale areas such as the Zhujiang (Pearl) River estuary. In contrast, 30 m-resolution EO-1 Hyperion imagery has potential for studying TSM in localized areas. We measured the surface spectral radiance reflectance of the river estuary water in the visible and near infra-red spectral range. Sensitivity analysis indicated that the ratio of remote sensing reflectance at 813 nm (Rrs(813)) to reflectance at 559 nm (Rrs(559)) could be used to estimate TSM concentration, and a linear relationship was established between the ratio and in-situ TSM concentration. We applied the linear relationship to Hyperion imagery to map TSM concentration in the estuary. The Hyperion imagery provided sufficient spatial resolution to detect spatiotemporal changes in TSM concentrations in the estuary small estuary area. This study demonstrated the usefulness of Hyperion imagery for mapping the distribution of TSM in estuary waters.