Nitrogen forms and decomposition of organic carbon in the southern Bohai Sea core sediments

Study on form characteristics of nitrogen in marine sediments is the primary method to research its biogeochemical cycling and nitrogen form characteristics in core sediments can reflect the process and results of early diagenesis in a certain degree. In this paper, Sequential extraction process in natural grain size was used for studying the existent forms of nitrogen in five core sediments of the southern Bohai Sea for the first time. Nitrogen was divided into two parts - transferable and fixed based on whether it could be extracted by the reagent. Distributions and early diagenesis of transferable nitrogen forms in the southern Bohai Sea were researched integratedly. Results indicate that IEF - N and OSF-N are predominant forms in transferable part in the studied core sediments. Contents of different nitrogen forms vary differently with depth, and have different diagenesis process. Decomposition constant of organic nitrogen (ON) and OC are about 15.51 -× 10^(-3)a^(-3)and 4.79× 10^(-3)a^(-1) respectively, and the decomposition content of biogenic elements C, N, P, Si has the sequence N>P>CSi. OC/TN (simplified as C/N in the following) ratio is much lower than OC/ON, which indicates that sediment preserves plenty of inorganic nitrogen (IN) and/or fixed nitrogen, and the decrease of OC/ON ratio with depth is due to ON reservation in sediments. Generally, transferable nitrogen accounts for more proportion of TN in the surface layer than in the deep layer of core sediments, whereas, some stable forms of nitrogen can activate and become transferable under appropriate environment, which induces the proportion of transferable nitrogen in TN in the deep layer to be almost the same as that in the surface layer.

Distribution characteristics of heavy metals in surface sediments and core sediments of the Shenzhen Bay in Guangdong Province,China

The concentration of zinc, chromium, cadmium, nickel, lead and copper was measured on both surface sediments and core sediments in the Shenzhen Bay. The average contents of all metals have exceeded the background values in the coastal zone of Guangdong Province. Cadmium is a heavy pollution matter which indicates a strong pollution level according to the ecological risk coefficient method. The ecological risk index of the whole area is 299 which belongs to middle and strong level. The area with strong pollution level is the near shore area closing to the inside of Shenzhen Bay, Shakou area is in the middle level while the weak pollution level occurs in Shenzhenhe Estuary according to ecological risk index. The four sediment cores can be divided into two parts based on lead-210 dating, sediments size analysis and economic development period in surrounding areas since 1950 with strong human intervention. The sediment size, deposition rate and human activities have positive relationship with the contents of heavy metals which directly impact the pollution level of heavy metals in sediments in Shenzhen Bay.

Provenance of Cored Sediments from Active Margin off Southwestern Taiwan Deduced from Geochemical Constraints

The cored sediments sampled by R/V Marion Dufrense in the active margin off southwestern Taiwan on the east side of the Manila Trench are mostly muds consisting mainly of quartz, feldspar, illite, chlorite ＋ kaolinite with a trace amount of montmorillonite. The cored sediments have higher Fe, Ti, Cr, Cs, Li, Ni, and V but lower Ca, Na, Mn, Hf, Nb, Sr, Ta, U and Zr contents when compared with the upper continental crust（UCC, Taylor and McLennan, 1985）. The Eu/Eu＊ ratios of the sediments averaging 0.69 indicate that the recycling effect on the Eu anomaly may be minor and the contribution of mafic source rock was unimportant, which can also be depicted in the La-Th-Sc plot（Cullers, 1994） showing a ＂mixed origin＂ close to the felsic end member. The chemistry of the cored sediment can be explained by a mixing model designed by Ho and Chen（1996） with four end members i.e., greywacke, shale, quartzite and limestone, which are widely distributed in the Cenozoic formations of southern Taiwan with greywacke as the dominant contributor followed by shale.

Geochemical characteristics of Sr isotopes in the LS33 drill core from the Qiongdongnan Basin, South China Sea, and their response to the uplift of the Tibetan Plateau

Making full use of modern analytical and testing techniques to explore and establish new indexes or methods for extracting paleoseawater geochemical information from sediments will help to reconstruct the sedimentary paleoenvironment in different research areas.The connection between the subsidence of the South China Sea basin and the uplift of the Tibetan Plateau has been a scientific concern in recent decades.To explore the information on the sedimentary paleoenvironment,provenance changes and uplift of Tibetan Plateau contained in core sediments(debris),we selected core samples from Well LS33 in the Qiongdongnan Basin,South China Sea,and analyzed the contents of typical elements(Al,Th,and rare earth elements)that can indicate changes in provenance and the Sr isotopic compositions,which can reveal the geochemical characteristics of the paleoseawater depending on the type of material(authigenic carbonate and terrigenous detritus).The results show the following:(1)during the late Miocene,the Red River transported a large amount of detrital sediments from the ancient continental block(South China)to the Qiongdongnan Basin.(2)The authigenic carbonates accurately record changes in the 87Sr/86Sr ratios in the South China Sea since the Oligocene.These ratios reflect the semi-closed marginal sea environment of the South China Sea(relative to the ocean)and the sedimentary paleoenvironment evolution process of the deep-water area of the Qiongdongnan Basin from continental to transitional and then to bathyal.(3)Since the Neogene,the variations in the 87Sr/86Sr ratio in the authigenic carbonates have been consistent with the variations in the uplift rate of the Tibetan Plateau and the sediment accumulation rate in the Qiongdongnan Basin.These consistent changes indicate the complex geological process of the change in the rock weathering intensity and terrigenous Sr flux caused by changes in the uplift rate of the Tibetan Plateau,which influence the Sr isotope composition of seawater.

Heavy metal pollution in tidal zones of Bohai Bay using the dated sediment cores

Three sediment cores were collected in November 2003 from Dagu estuary to Qikou estuary. The main polluted heavy metals in the sediment of tidal zones for the Bohai Bay have been found by analyzing the relationship among the contents of heavy metals, the contents of geochemical elements （Fe, AI and Mn） and the size of grain. The dominating contaminative elements in tidal sediments of Bohai Bay are Pb, Zn and Cd. Their contents are higher than the corresponding upper limit of environmental background values and they have very faint correlation with the corresponding contents of geochemical elements and the size of grain, indicating the anthropogenic enrichment. Especially, the preliminary study on the pollution sources and the history of heavy metals in the Dagu estuary has been done using the dated results. The contamination by Zn and Cd also started in the middle 1950s, while the contamination by Pb appeared in the early 1940s. The pollution by Zn and Cd mainly originate from sewage discharge, while the pollution by Pb has many sources, like atmosphere deposition and industrial discharRe.

Vertical distribution of nonylphenol and nonylphenol ethoxylates in sedimentary core from the Beipaiming Channel, North China

The vertical profiles of nonylphenol （NP） and nonylphenol ethoxylates （NPEOs） were investigated in a sediment core from the Beipaiming Channel, North China using high sensitive LC-MS and GC-MS metthods In this core, relatively high concentrations of NP and NPEOs occurred in the surface sediment （≤40 cm）, with the maximum value of NP and NPEOs reaching 3539 and 12735 mg/g, respectively, whereas, no NP or NPEOs were detected in deeper sediments （〉40 cm）. The high concentrations of NP and NPEOs in the surface layers suggested recent inputs in this area. NPEOs with short ethoxy chains （NPnEO, n=0-3） were dominant in the NPEO mixture with percentages from 54% to 78%, which were similar to the distribution of homolog NPEO in effluents from nearby sewage treatment plants （STPs）, indicating that the channel received the effluents from these STPs. The sewage treatment ratio was quite similar to that found in North America before the 1980s. Finally, the concentrations of NP and NPEOs were related to the total organic carbon （TOC） （p〈0.001）, suggesting that TOC was an important factor for vertical distribution of NPEOs and NP from the Beipaiming Channel.

Radionuclide dating(^(210)Pb,^(137)Cs) of recent inter-dune saline lake sediment cores in the Badain Jaran Desert,Inner Mongolia,Northwest China

Inter-dune lake sediment cores are ideal and unavailable materials for study climate and environmental changes of arid region.The precious dating of lake sediment cores is required for carrying out high resolution climate and environmental changes with these cores.The Badain Jaran inter-dune lake group embedding in the sand sea is the

An improved method for quantitatively measuring the sequences of total organic carbon and black carbon in marine sediment cores

Understanding global carbon cycle is critical to uncover the mechanisms of global warming and remediate its adverse ef fects on human activities.Organic carbon in marine sediments is an indispensable part of the global carbon reservoir in global carbon cycling.Evaluating such a reservoir calls for quantitative studies of marine carbon burial,which closely depend on quantifying total organic carbon and black carbon in marine sediment cores and subsequently on obtaining their high-resolution temporal sequences.However,the conventional methods for detecting the contents of total organic carbon or black carbon cannot resolve the following specific difficulties,i.e.,(1)a very limited amount of each subsample versus the diverse analytical items,(2) a low and fluctuating recovery rate of total organic carbon or black carbon versus the reproducibility of carbon data,and(3)a large number of subsamples versus the rapid batch measurements.In this work,(i)adopting the customized disposable ceramic crucibles with the microporecontrolled ability,(ii)developing self-made or customized facilities for the procedures of acidification and chemothermal oxidization,and(iii)optimizing procedures and carbon-sulfur analyzer,we have built a novel Wang-Xu-Yuan method(the WXY method)for measuring the contents of total organic carbon or black carbon in marine sediment cores,which includes the procedures of pretreatment,weighing,acidification,chemothermal oxidation and quantification;and can fully meet the requirements of establishing their highresolution temporal sequences,whatever in the recovery,experimental efficiency,accuracy and reliability of the measurements,and homogeneity of samples.In particular,the usage of disposable ceramic crucibles leads to evidently simplify the experimental scenario,which further results in the very high recovery rates for total organic carbon and black carbon.This new technique may provide a significant support for revealing the mechanism of carbon burial and evaluating the capacity of marine carbon accumulation and sequestration.

Distribution of general aerobic heterotrophic bacteria in sediment core taken from the Canadian basin and the Chukchi Sea

The occurrence percentage and abundance of General Aerobic Hetero- trophic Bacteria （GAB） were determined by using the method of MPN for 182 sub- samples from 10 sediment cores taken from the Canadian basin and the Chukchi Sea at two different culturing temperatures. The results showed that the general occurrence percentage of GAB was quite high, average abundanees of GAB at cultured temperatares of 4℃ and 25℃ were 4.46 ×10^7 and 5.47×10^7 cells·g^-1（wt）, respectively. The highest abundance of GAB occurred at 20 -22 cm section in the sediment. GAB abundances changed among the section of sediments, but there is a trend ： the a-bundances at the middle or lower sections were lower than those at upper section. Cultivation at 25℃ could improve the occurrence percentage and abundances of GAB, which suggests that the increasing of temperature may change the living circum-stances of GAB. The differences of GAB among the latitudes areas indicated that occurrence percentage and abundances of GAB in middle latitude areas were higher than those in the higher or lower latitude areas, and were more obvious at 4℃ than those at 25℃. The GAB abundances in sediment under the shallower water seemed to be low- er than those in sediments under the deeper water and this status was more obvious at 25℃ than that at 4℃.

11000-Year Record of Trace Metals in Sediments off the Southern Shandong Peninsula in the South Yellow Sea

Geochemical background values are the normal concentration of trace metals in the natural environment and sediment cores have been proved to be excellent samples to get these values.The trace metal(Cu,Pb,Zn,Cr,Cd,As,Hg,Ni,Li,and Co)concentration profiles along a sediment core are investigated to get the background values and to assess the depositional processes and contamination levels off the southern Shandong Peninsula,China.All the metals,except As and Hg,had similar concentration profiles with the highest average values during the period of 6-3 kyr.The high concentrations of As and Hg occurred before 6ka and during the period of 3-0 kyr.The difference in metal concentrations before and after 6 kyr was mainly attributed to the source of core sediments,which are derived from proximal sediment on the Shandong Peninsula before 6 kyr and the mixture of proximal sediment and Yellow River sediment after 6 kyr.The effects of particle size and human activity were mainly contributed to the metal concentrations since 6 kyr.The average concentrations of trace elements in sediments between 6 and 3 kyr were selected as background values.The principal component factor analysis indicate that the metals were from the natural sources throughout the observed depositional period,with the exception of As and Hg,which may had anthropogenic sources for the sediments from the bottom 2 m of the core.Their geoaccumulation indices indicate that the sediments were not contaminated for Cu,Zn,Cr,Cd,Pb,Ni,Li and Co,whereas they were contaminated recently for As and Hg due to the regional civilization and human activities.

In-situ formation of perylene in lacustrine sediments and its geochemical significance

To identify the possible sources and formation mechanism of perylene in sediments,temporal trends of perylene and other polycyclic aromatic hydrocarbons,as well as the organic matters,were analyzed in sediment cores from Dianchi Lake and Sihailongwan Maar Lake in China.Significantly high concentrations of perylene were observed in both cores and increased gradually with the sediment depth.Source identification suggested that perylene in both cores were of primarily diagenetic origin,other than the anthropogenic inputs.Both terrigenous and aquatic organic matters could be the source of perylene in sediments and diagenetic formation of perylene in sediment is kinetically controlled by the microbial activities under anaerobic conditions.All evidence points to the fact that the formation of perylene in sediment should be an index of the microbial activities and environmental conditions,other than the source of specific organic matters or precursors.In addition,we should be cautious when using any geochemical indicators involving the microbial alternation.

A Hydraulic Hammer Corer Utilizing Hydrostatic Energy for Hard Seafloor Sediment Coring

The paper presents the design and preliminary test results of a corer used for hard seafloor sediments sampling. Generally the sediment cores are provided by either gravity-type coting or deep-ocean drilling for a range of studies. However, in consideration of the operability and available sample length in collecting hard sediments, these methods exhibit no advantages. In this paper, a new corer which can exploit both hydrostatic energy and gravity energy for hard sediments coting is presented. The hydrostatic energy is provided by pressure differential between ambient seawater pressure and air pressure in an empty cavity. During sampling process, the corer penetrates into the sediment like a gravity corer and then automatically shifts to the percussion mode. The experiments in the laboratory indicate that the corer can complete 40 cycles in the sea with a cycle time of 2.8 seconds in percussion mode and impact the sample tube with the velocity of 0.2 m/s during each cycle. Besides, its adjustable falling velocity can make the corer achieve the maximum efficiency in coring different sediments.

^(210)Pb distribution characteristics in the lake sediment core at Great Wall Station,Antarctica

The results of 210 Pb measurements in the lake sediment core from Antarctica are reported: the relative specific activities of 210 Pb in the lake sediment were found to decrease exponentially with the depth in the study area; the sedimentation rate of the lake is about 0.072 cm/a. This paper shows that 210 Pb method is applicable to Antarctic lake sediment ,and during the 1960's the atmospheric nuclear tests have an effect on the rate of 210 Pb deposition in Antarctica.

Boron Isotopic Composition of Halite from 46-m-long Sediment Core in the Qarhan Salt Lake,Western China

Previous studies have investigated the boron isotopic composition of salt lake brines in the Qaidam Basin,western China.However,the research on boron isotopic composition of halite is very limited due to halite’s low

Sedimentary Records of Heavy Metal Pollution in Fuxian Lake,Yunnan Province,China:Intensity,History,and Sources

This study focused on the concentration change of heavy metals of sediment cores in heavily polluted north area and less polluted middle area of Fuxian Lake in Southwest China.On the basis of the analysis of Cu,Ni,Ti,V,Pb,Cd,and Zn concentration-depth profiles,the pollution history of heavy metals was studied using 137cesium(137Cs) dating.The sources of heavy metals were distinguished by normalization of their profiles to aluminum and analysis of heavy metal concentrations of potential source materials.Geoaccumulation index(Igeo) was used to quantify their contamination intensity.The results showed that all the heavy metals found in the Fuxian Lake sediments originated naturally before 1980s.Cu,Ni,Ti,and V were still mainly natural in the north lake after 1980s,Cu,Ni,Ti,V,and Pb were mainly natural in the middle lake at all time,but the concentrations of Pb and Zn in the north lake were influenced by industrial wastes from the phosphorus fertilizer factory and cement plants.In all the lake,the contaminations of Cd and Zn were the results of agricultural cultivation using a large amount of fertilizers and the atmospheric fallouts of dusts from cement plants.At present,the geoaccumulation indices showed that the Fuxian Lake sediments were moderately to strongly polluted by Cd in the middle lake,and unpolluted to moderately polluted by Pb and Zn and strongly polluted by Cd in the north lake.Moreover,the pollution intensities of Cd,Zn,and Pb have been increased since 1980s.

Terrestrial input and nutrient change reflected by sediment records of the Changjiang River Estuary in recent 80 years

A variety of environmental problems have been observed in the Changjiang River Estuary and adjacent coastal area, including eutrophication, harmful algal blooms（HABs）, and hypoxia in recent decades. Application of sedimentary biogenic element indicators on the study of paleoenvironment can reconstruct environmental evolution history of waters. Two 210Pb-dated cores were collected from the Changjiang River Estuary（S3） and adjacent coastal area（Z13）, and total organic carbon（TOC）, total nitrogen（TN）, biogenic silicon（BSi）, total phosphorus（TP） and phosphorus（P） species were analyzed. Three stages of environmental changes are deduced by the nutrient sedimentary records. First, nutrient concentration increased rapidly since the 1950 s, which attributed to agriculture development and overused chemical fertilizers. Second, nutrient concentration kept high and primary production began to promote during the 1960 s to 1980 s, while diatom abundance and proportion began to decline since the 1970 s, accompanied by reduced 23 Si O- concentration and flux from the river. Third, due to several dams and bridges constructed, river runoff and coastal hydrodynamic conditions reduced to a certain extent since the 1990 s, which aggravated the unbalance in nutrient structure. Multi-nutrient proxies in sediment can reflect the natural environm-ental changes as well as influence of human activities.

Records of bulk organic matter and plant pigments in sediment of the ＂red-tide zone＂ adjacent to the Changjiang River estuary

Cultural eutrophication caused by nutrient over-enrichment in coastal waters will lead to a cascading set of ecosystem changes and deleterious ecological consequences,such as harmful algal blooms(HABs) and hypoxia.During the past two decades since the late 1990s,recurrent large-scale HABs(red tides)and an extensive hypoxic zone have been reported in the coastal waters adjacent to the Changjiang River estuary.To retrieve the history of eutrophication and its associated ecosystem changes,a sediment core was collected from the "red-tide zone" adjacent to the Changjiang River estuary.The core was dated using the^(210)Pb radioisotope and examined for multiple proxies,including organic carbon(OC),total nitrogen(TN),stable isotopes of C and N,and plant pigments.An apparent up-core increase of OC content was observed after the 1970s,accompanied by a rapid increase of TN.The concurrent enrichment of δ^(13)C and increase of the C/N ratio suggested the accumulation of organic matter derived from marine primary production during this stage.The accumulation of OC after the 1970 s well reflected the significant increase of primary production in the red-tide zone and probably the intensification of hypoxia as well.Plant pigments,including chlorophyll a,p-carotene,and diatoxanthin,showed similar patterns of variation to OC throughout the core,which further confirmed the important contribution of microalgae,particularly diatoms,to the deposited organic matter.Based on the variant profiles of the pigments representative of different microalgal groups,the potential changes of the phytoplankton community since the 1970s were discussed.

Reviving and characterizing three species of dinoflagellate cysts dormant for about 70 years in the East China Sea:Biecheleria brevisulcata,Biecheleriopsis adriatica,and Scrippsiella donghaienis

Many marine dinoflagellates can form resting cysts as a part of their life cycle,and the cysts could be buried in sediment and remained viable for as long as over 150 years.However,only a very limited number of cyst species have been revived from long-buried sediments and investigated in regard to a possible shift in the intra-specific genetic structure of a species detected from the historical record at a particular location.Here,we report a successful germination of three species of resting cysts that were sampled from the depth dated back to 1941±18 AD from a 44-cm sediment core from the East China Sea.Seven isolates were established from germination of single cyst isolation or multi-cyst germinations.LSU rRNA gene or ITS sequences of these strains were obtained,then they were identified to be Biecheleria brevisulcata(five strains),Biecheleriopsis adriatica(one strain),and Scrippsiella donghaienis(one strain)in terms of morphology and rRNA gene sequence.Biecheleria brevisulcata strain 1,Bps.adriatica strain 21,and S.donghaienis strain 23 were examined in detail with light microscope(LM)and scanning electron microscope(SEM),and analyzed with high performance liquid chromatography(HPLC)for their pigment compositions,and genetic diversity.We also confirmed the presence of a resting cyst of Bps.adriatica in the field for the first time.The LSU rRNA gene-based genetic distances of Bps.adriatica from that obtained from water sample,single-cell PCR sequencing for the cysts isolated from the surface sediment of the same sea area and that reported from other regions during the recent years,and ITS-based genetic distances of S.donghaienis from that obtained from cysts isolated from the surface sediment of the same location and that reported from other regions during the recent years indicated that the intra-specific genetic structure of each species in the sampling area may have shifted during the last 70 years.Our work confirms that B.brevisulcata,Bps.adriatica,and S.donghaienis,all described as new species around 2010,have inhabited the East China Sea for about 70 years.The present work reports for the first time the revival of dinoflagellate resting cysts long-buried in the coastal sediments of China,which facilitates further study on the historical occurrences of other harmful dinoflagellates and their relevance to the regional climate and environmental changes in China.

Toxic marine diatoms of Hong Kong:A paleoecological study

To determine whether toxic diatoms in Hong Kong's Victoria Harbour have become more common during the last four decades,a gravity core was taken from the anaerobic sediments of Kowloon Bay in the harbour. Analysis of these sediments from a depth of 0-1cm,4-5cm and 9-10cm indicated that 6.4%,2.4% and 1.5% of the diatoms observed at each of these three respective depths belonged to the genus Pseudonitzschia. The abundance of Pseudonitzschia frustules in the surface sediments of Victoria Harbour was significantly higher(p<0.05)than it was in the harbour's deeper and older(ca.1965)sediments. The increase in potentially toxic diatom species over the last 30 years was attributed to a variety of factors including the addition of large amounts of nutrients to Hong Kong's coastal waters as a re- sult of man's activities.

Sedimentary Records and Environmental Analysis of the Ximencuo Lake in Northeast Qinghai-Tibet Plateau in the Past 1,700 Years

Lake sediment is the recorder of historical climate fluctuation and basin environment change. This study collected the Ximencuo Lake sediment in source area of the Yellow River, analyzed organic matters and geochemical elements of the core, obtained nearly environment changes of the past 1,720 years. The results showed the environment evolution process of the 47-cm columnar core can be divided into four stages: below 32 cm(before 900 A.D.), corresponding to the cool and wet climate; 32–20 cm(900 A.D–1300 A.D.), corresponding to the warming temperature and decreasing precipitation; between 20–3.5 cm(1300–1900 A.D.), the stage is more consistent with the Little Ice Age, and precipitation gradually reduced; 3.5–0 cm(since 1900 A.D.), this is the twentieth Century warming period with increasing temperature and reduced precipitation. Phosphorus content increased rapidly in the last 20 years, reflecting the continuously increasing human interventions, but before this period, the P content was low and stable, indicating the natural background of regional phosphorus content.