Geochemistry of organic carbon and nitrogen in surface sediments of coastal Bohai Bay inferred from their ratios and stable isotopic signatures

To investigate the characteristics and potential sources of heavy metals pollution, surface sediments collected from Bohai Bay, North China, were analyzed for the selected metals (Cd, Cr, Cu, Ni, Pb, and Zn). The Geoaccumulation Index was used to assess the level of heavy metal pollution. Pb isotopic compositions in sediments were also measured to effectively identify the potential Pb sources. The results showed that the average concentrations of Cd, Cr, Cu, Ni, Pb, and Zn were 0.15, 79.73, 28.70, 36.56, 25.63, and 72.83 mg/kg, respectively. The mean concentrations of the studied metals were slightly higher than the background values. However, the heavy metals concentrations in surface sediments in Bohai Bay were below the other important bays or estuaries in China. The assessment by Geoaccumulation Index indicated that Cr, Zn, and Cd were classified as “the unpolluted” level, while Ni, Cu, and Pb were ranked as “unpolluted to moderately polluted” level. The order of pollution level of heavy metals was:Pb>Ni>Cu>Cr>Zn>Cd. The Pb isotopic ratios in surface sediments varied from 1.159 to 1.185 for206Pb/207Pb and from 2.456 to 2.482 for208Pb/207Pb. Compared with Pb isotopic radios in other sources, Pb contaminations in the surface sediments of Bohai Bay may be controlled by the mix process of coal combustion, aerosol particles deposition, and natural sources.

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Carbon and nitrogen stable isotopic signatures of human dietary change in the Georgia Bight

American Journal of Physical Anthropology ◽

10.1002/ajpa.1330890206 ◽

1992 ◽

Vol 89 (2) ◽

pp. 197-214 ◽

Cited By ~ 53

Author(s):

Clark Spencer Larsen ◽

Margaret J. Schoeninger ◽

Nikolaas J. van der Merwe ◽

Katherine M. Moore ◽

Julia A. Lee-Thorp

Keyword(s):

Dietary Change ◽

Isotopic Signatures ◽

Carbon And Nitrogen ◽

Stable Isotopic ◽

Georgia Bight

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How does acid treatment to remove carbonates affect the isotopic and elemental composition of soils and sediments?

Environmental Chemistry ◽

10.1071/en07070 ◽

2008 ◽

Vol 5 (1) ◽

pp. 33 ◽

Cited By ~ 34

Author(s):

Milena Fernandes ◽

Evelyn Krull

Keyword(s):

Organic Carbon ◽

Isotopic Analysis ◽

Isotopic Signature ◽

Isotopic Signatures ◽

Carbon And Nitrogen ◽

Isotopic Shifts ◽

Soils And Sediments ◽

Significant Difference ◽

Acid Treatments

Environmental context. The ability to accurately determine the elemental and isotopic composition of soils and sediments has important implications to our quantitative understanding of global biogeochemical cycles. However, the analysis of organic carbon in solid matrices is a time-consuming task that requires the selective removal of carbonates, a treatment that has the potential to significantly alter the composition of the original sample. In the present work, we compare three of the most common acid treatments used for carbonate removal, and critically evaluate their effect on the content and isotopic signature of organic carbon and nitrogen in both soils and sediments. Abstract. In the present work, we compared the efficacy of three acid treatments in removing carbonates from soils and sediments for elemental and isotopic analysis. The methods tested were (1) refluxing with H2SO3; (2) in situ treatment with H2SO3 in silver capsules; and (3) treatment with HCl followed by rinsing with water. Refluxing with H2SO3 led to substantial losses of organic carbon and nitrogen, but comparatively small nitrogen isotopic shifts. The in situ treatment was inadequate for carbonate-rich samples (contents ≥30%) as a consequence of the formation of a mineral precipitate. Treatment with HCl led to substantial losses of nitrogen from carbonate-rich samples, and deviations in nitrogen isotopic signatures (δ15N) of up to 3.7‰. δ15N values showed no significant difference between acid-treated and untreated samples or between treatments, although variability was high and influenced by sample composition. Carbonate-poor samples showed no statistical difference in δ13C values between treatments, whereas carbonate-rich samples tended to be more 13C-depleted when treated with HCl, potentially suggesting the preferential preservation of 13C-depleted compounds (e.g. lipids or lignin).

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Composition Characteristics of Organic Matter and Bacterial Communities under the Alternanthera philoxeroide Invasion in Wetlands

Applied Sciences ◽

10.3390/app10165571 ◽

2020 ◽

Vol 10 (16) ◽

pp. 5571

Author(s):

Qingqing Cao ◽

Haijie Zhang ◽

Wen Ma ◽

Renqing Wang ◽

Jian Liu

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Constructed Wetlands ◽

High Throughput Sequencing ◽

Surface Sediments ◽

Alligator Weed ◽

Weed Invasion ◽

Bacterial Phyla ◽

Carbon And Nitrogen ◽

Natural Wetlands

The influence of Alternanthera philoxeroide (alligator weed) invasion on wetland organic matter (OM) accumulation and bacterial changes is rarely studied, but is possibly an important step for revealing the invasion mechanism. Thus, the distribution characteristics of light fraction organic carbon and nitrogen (LFOC and LFON), and heavy fractions organic carbon and nitrogen (HFOC and HFON) were analyzed. Sampling was done on two sediment depths (0–15 cm and 15–25 cm) of invaded and normal habitats of two natural wetlands and two constructed wetlands, and bacterial taxa and composition in surface sediments were also analyzed by high-throughput sequencing. In the surface sediments, the LFOC and LFON contents were significantly higher in the constructed wetlands (0.791 and 0.043 g·kg−1) than in the natural wetlands (0.500 and 0.022 g·kg−1), and the contents of the C and N fractions were also prominently higher in the invaded areas than in normal wetland habitats. The OM storage was relatively stable. Proteobacteria (55.94%), Bacteroidetes (5.74%), Acidobacteria (6.66%), and Chloroflexi (4.67%) were the dominant bacterial phyla in the wetlands. The abundance of Acidobacteria, Actinobacteria, and Gemmatimonadetes were significantly higher in the invaded areas than in the normal habitats. The relative high abundance-based coverage estimator (ACE) index in the constructed wetlands and invaded areas suggested the corresponding high bacterial diversity. The significant and positive relationship between Acidobacteria and organic nitrogen concentrations suggested their potential and positive interrelationships. This study demonstrated that the alligator weed invasion could significantly change the compositions of sediment organic matterand bacteria, thus further changing the nutrition cycle and wetland microhabitat.

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