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1.
Akiko Murakami-Kitase Takamoto Okudaira Jun Inoue 《Environmental Earth Sciences》2010,59(8):1723-1729
Spheroidal carbonaceous particles (SCPs) are produced by the high-temperature combustion of fossil fuels and are emitted to
the atmosphere. Previous studies are divided regarding whether SCPs derived from the combustion of various fossil fuels can
be identified based on their surface morphologies and chemical compositions. In this study, we examined the surface morphology
and chemical composition of SCPs in sediment core samples collected from Osaka Bay, Japan, with the aim of evaluating the
usefulness of SCPs morphology in identifying their origin. Scanning electron microscope (SEM) observations reveal three distinct
surface morphologies: (1) smooth, (2) rough and irregular, and (3) convoluted and layered. According to a morphological classification
scheme proposed previously, the former two morphologies correspond to coal-derived carbon particles, whereas the latter corresponds
to oil-derived carbon particles. In terms of the chemical compositions of the particles with different morphologies, as analyzed
by energy-dispersive spectroscopy, linear discriminant analysis reveals that the two fuel types can be distinguished. An overall
success rate of >90% of reference of morphologically classified material correctly assigned to two groups that are chemically
different each other, indicating a relationship between surface morphology and chemical composition. This result suggests
that morphological characterization based on conventional SEM observations is useful in identifying the source fuel of SCPs. 相似文献
2.
Todd Kuiken 《Environmental Earth Sciences》2010,59(6):1349-1357
The Daliao river system in China has been seriously affected by long-term intensive industrial, urban and agricultural activities.
The objectives of this study were to determine the total phosphorus (TP) content and forms of phosphate in the sediments and
investigate geochemical relationships between P forms and sediment mineral phases. Twenty-seven samples of surface sediments
were collected and analyzed for P and major elements. Chemical forms of phosphate in the sediments were measured by sequential
selective extraction method. Results indicate that TP in the sediments of the Daliao river system averaged 703 mg kg−1, in the range from 206 to 1,342 mg kg−1. The sediments in the tributaries and near cities contained high TP, due to discharge of municipal and industrial effluents.
The distribution of phosphate in the various mineral phases followed the order: Ca-P > RES-P > RS-P > Fe-P > Al-P > S/L-P
for the Hun river and Taizi river, and Ca-P > Fe-P > RES-P > RS-P > Al-P > S/L-P for the Daliao river. Fe and Ca contents
in the sediments were positively correlated to Fe associated P (Fe-P and RS-P) and Ca-P, respectively. In addition, sediment
organic matter, Fe and Ca contents were positively correlated to TP in the sediments. However, Al content was not correlated
to Al-P or TP in the sediments. Generally, the sediments contaminated by effluents and in tidal zone contained more bioavailable
P. Possible release of P from these sediments to overlying water might pose potential risk on estuarine eutrophication. 相似文献
3.
Concentration and mass loadings of heavy metals adsorbed on sediment from an urban road surface in Beijing were investigated.
The buildup and washoff processes are discussed. Results showed that masses of sediments smaller than 500 μm in diameter varied
from 11.2 to 25.5 g/m2. On average, sediments smaller than 125 μm accounted for 42.9% of sediments smaller than 500 μm in mass. Cd, Cr, Cu, and
Ni were more likely to attach to smaller sediments than bigger ones, compared to Pb and Zn. Mass loading of the sediments
generally increased with antecedent dry periods, but the linear relationship was better for smaller sediments than for bigger
ones. Heavy metal concentrations adsorbed on sediments with diameter less than 40 μm generally decreased more obviously than
those adsorbed on bigger ones after rainfall events. 相似文献
4.
Heavy metal contamination of coastal lagoon sediments by anthropogenic activities: the case of Nador (East Morocco) 总被引:1,自引:0,他引:1
Nador lagoon sediments (East Morocco) are contaminated by industrial iron mine tailings, urban dumps and untreated wastewaters
from surrounding cities. The lagoon is an ecosystem of biological, scientific and socio-economic interests but its balance
is threatened by pollution already marked by biodiversity changes and a modification of foraminifera and ostracods shell structures.
The aim of the study is to assess the heavy metal contamination level and mobility by identifying the trapping phases. The
study includes analyses by ICP-AES and ICP-MS, of, respectively, major (Si, Al, Mg, Ca, Fe, Mn, Ti, Na, K, P) and trace elements
(Sr, Ba, V, Ni, Co, Cr, Zn, Cu, As, Pb, Cd) in sediments and suspended matter, heavy metals enrichment factors calculations
and sequential extractions. Results show that sediments contain Zn, Cu, Pb, V, Cr, Co, As, Ni with minimum and maximum concentrations,
respectively, of 4–1190 μg/g, 4–466 μg/g, 11–297 μg/g, 11–194 μg/g, 9–139 μg/g, 1–120 μg/g, 4–76 μg/g, 2–62 μg/g. High concentrations
in Zn are also present in suspended matter. The enrichment factors show contamination in Zn, Pb and As firstly induced by
the mining industry and secondly by unauthorized dumps and untreated wastewaters. Cr and Ni are bound to clays, whereas V,
Co, Cu and Zn are related to oxides. Thus, the risk in metal mobility is for the latter elements and lies in the oxidation–reduction-changing
conditions of sediments. 相似文献
5.
Slavica Matijević Natalia Bojanić Grozdan Kušpilić Živana Ninčević Gladan 《Environmental Earth Sciences》2009,59(4):853-866
Phosphorus (P) species concentrations in 0–2 cm surface sediment layer were investigated monthly from November 2001 to December
2002 at the bay, channel and open sea stations in the middle Adriatic. Modified SEDEX method was used for inorganic phosphorus
species determination [P in biogenic (P-FD), authigenic (P-AUT), detrital apatite (P-DET) and P adsorbed on to iron oxides
and hydroxides (P–Fe)], and organic phosphorus (P-ORG). P-FD, P-AUT and P-DET concentration ranges (1.5–5.4, 0–2.7 and 0.4–3.4 μmol g−1, respectively) were similar at all stations, and showed no obvious common trend of seasonal changes. P–Fe ranged from 1.9
to 11.9 μmol g−1 with the highest values at bay station and higher seasonal oscillations than other inorganic P forms. P-ORG ranged from 0.3
to 18.7 μmol g−1 with higher concentrations at stations of fine-sized sediments and showed increased concentrations in warm part of the year
at all stations. Correlation between concentrations of P–Fe in the surface sediment layer and orthophosphate sediment-water
interface concentration gradients at bay and channel stations indicated to P–Fe importance in the orthophosphate benthic flux.
For the bay station, linkage between sediment P-ORG and chlorophyll a concentrations, primary production and microzooplankton abundance was established, indicating a 1 month delay of sediment
response to production fluctuations in the water column. 相似文献
6.
Sediment cores from Sagamore Lake and Woods Lake in New York State's Adirondack Park, an area remote from industrial activities, were analyzed for polynuclear aromatic hydrocarbons (PAH) by high resolution gas chromatography/mass spectrometry (GC/MS). Their composition and distribution with depth in the sediment indicate that the parental PAH in the surface sediments are primarily produced by anthropogenic combustion of fossil fuels. Perylene in deep sediments is apparently transformed from natural precursors in the reducing environment, however, the exact precursors remain unknown. The rather even sediment distributions of the non-parental PAH differ from the parental, suggesting biogenic origins. Based on their chemical structures, retene and alkylated and partially hydrogenated phenanthrenes are believed to be biogenically converted from abietic acid; hydrochrysenes and hydropicenes, from pentacyclic triterpenes. 相似文献
7.
Xiangchun Quan Yulai Wang Weicong Xiong Mengchang He Zhifeng Yang Chunye Lin 《Environmental Earth Sciences》2010,61(8):1725-1734
The Daliao River watershed, an important industrial base of China, has been heavily influenced by anthropogenic activities.
Microbes in sediments play an important role in recycling of organics and nutrients, and knowledge of the microbial composition
and community structure in river sediments can help us to understand the contribution of microorganisms to environmental processes
and their response to environmental perturbation. In this study, 11 surface sediment samples and 1 core sediment sample were
collected from the Daliao River water system and its estuary, and their microbial abundance and community compositions were
investigated using fluorescence in situ hybridization. Results showed that total cell numbers in surface sediments from different
locations ranged from 4.2 × 108 to 16.2 × 108 cells cm−3. Domain bacteria represented 58–82% with α-, β-, and γ-proteobacteria as the major subgroups summing up to 40%. Total cell
numbers along the core sediment profile ranged from 7.9 × 108 to 20.1 × 108 cells cm−3, with relatively higher total cell numbers in the upper (0–6 cm) and middle (21–30 cm) layers. In the core sediment, domain
bacteria represented 62–85% and archaea 1.0–11.8%. α-, β- and γ-Proteobacteria were three major phylogenetic groups of bacteria
in the core sediment also with γ-proteobacteria as the most abundant subgroup accounting for 9.8–40.8% of total cells. 相似文献
8.
Geochemical Characteristics of Amino Acids in Sediments of Lake Taihu, A Large, Shallow, Eutrophic Freshwater Lake of China 总被引:1,自引:0,他引:1
Xin Yao Guangwei Zhu Linlin Cai Mengyuan Zhu Linlin Zhao Guang Gao Boqiang Qin 《Aquatic Geochemistry》2012,18(3):263-280
To examine the biogeochemistry of amino acids (AAs) in the sediment of Lake Taihu, surface sediments (0–3 cm) and deeper sediments
(18–21 cm) were collected at 21 sites from different ecotype zones of the lake. AAs were extracted from the sediments, and
the total hydrolyzable amino acids (THAA) were determined by high-performance liquid chromatography instrument. The THAA contents
in Taihu sediment were much lower than that in marine sediments, ranging from 6.84 to 38.24 μmol g−1 in surface sediments and from 2.91 to 18.75 μmol g−1 in deeper sediments in Taihu, respectively. AAs were a major fraction of the organic matter (OM) and organic nitrogen in
Taihu sediments. The AAs on average contributed 8.2% of organic carbon (OC) and 25.0% of total nitrogen (TN) from surface
sediments, and 5.9% of OC and 20.5% of TN in deeper sediments, respectively. AA composition provided very useful information
about the degradation of OM. Glycine (Gly) and lysine (Lys) were the predominant forms of AAs in the sediments, irrespective
of lake regions, followed by alanine, glutamic acid, serine (Ser), and aspartic acid (Asp). The high concentrations of Gly,
Lys, and Ser suggested that these forms of AAs were relatively refractory during OM degradation in sediments. The relationship
between the Asp/Gly ratio and Ser + Thr [mol%] indicated that OM in surface sediment was relatively fresher than that in deeper
sediments. The AAs-based degradation index (DI) gave a similar conclusion. The composition and DI of AAs in surface sediments
are markedly different across different zones in Taihu. The percentages of AAs to organic carbon (AA-C%) and total nitrogen
(AA-N%) were higher in phytoplankton-dominated zones than those in macrophyte-dominated zones. These results suggest that
DI could provide useful information about the degradation of OM in shallow lakes such as Taihu. 相似文献
9.
Utilizing a sequential extraction technique this study provides the first quantitative analysis on the abundance of sedimentary
phosphorus and its partitioning between chemically distinguishable phases in sediments of the Bering Sea, the Chukchi Sea
and the Mackenzie River Delta in the western Arctic Ocean. Total sedimentary phosphorus (TSP) was fractionated into five operationally
defined phases: (1) adsorbed inorganic and exchangeable organic phosphorus, (2) Fe-bound inorganic phosphorus, (3) authigenic
carbonate fluorapatite, biogenic apatite and calcium carbonate-bound inorganic and organic phosphorus, (4) detrital apatite,
and (5) refractory organic phosphorus. TSP concentrations in surface sediments increased from the Chukchi Sea (18 μmol g−1 of dried sediments) to the Bering Sea (22 μmol g−1) and to the Mackenzie River Delta (29 μmol g−1). Among the five pools, detrital apatite phosphorus of igneous or metamorphic origin represents the largest fraction (~43%)
of TSP. The second largest pool is the authigenic carbonate fluorapatite, biogenic apatite as well as CaCO3 associated phosphorus (~24% of TSP), followed by the Fe-bound inorganic phosphorus, representing ~20% of TSP. The refractory
organic P accounts for ~10% of TSP and the readily exchangeable adsorbed P accounts for only 3.5% of TSP. Inorganic phosphorus
dominates all of phosphorus pools, accounting for an average of 87% of the TSP. Relatively high sedimentary organic carbon
and total nitrogen contents and low δ13C values in the Mackenzie River Delta together with the dominance of detrital apatite in the TSP demonstrate the importance
of riverine inputs in governing the abundance and speciation of sedimentary phosphorus in the Arctic coastal sediments. 相似文献
10.
Distribution and enrichment of trace metals in marine sediments of Bay of Bengal,off Ennore,south-east coast of India 总被引:1,自引:0,他引:1
In order to avoid the pollution of trace metals in marine environment, it is necessary to establish the data and understand
the mechanisms influencing the distribution of trace metals in marine environment. The concentration of heavy metals (Fe,
Mn, Cr, Cu, Ni, Pb, Zn, Co and Cd) were studied in sediments of Ennore shelf, to understand the metal contamination due to
heavily industrialized area of Ennore, south-east coast of India. Concentration of metals shows significant variability and
range from 1.7 to 3.7% for Fe, 284–460 μg g−1 for Mn, 148.6–243.2 μg g−1 for Cr, 385–657 μg g−1 for Cu, 19.8–53.4 μg g−1 for Ni, 5.8–11.8 μg g−1 for Co, 24.9–40 μg g−1 for Pb, 71.3–201 μg g−1 for Zn and 4.6–7.5 μg g−1 for Cd. For various metals the contamination factor (CF) and geoaccumulation index (I
geo) has been calculated to assess the degree of pollution in sediments. The geoaccumulation index shows that Cd, Cr and Cu moderately
to extremely pollute the sediments. This study shows that the major sources of metal contamination in the Ennore shelf are
land-based anthropogenic ones, such as discharge of industrial wastewater, municipal sewage and run-off through the Ennore
estuary. The intermetallic relationship revealed the identical behavior of metals during its transport in the marine environment. 相似文献
11.
Microelectrode Study of Oxygen Uptake and Organic Matter Decomposition in The Sediments of Xiamen Western Bay 总被引:2,自引:0,他引:2
Sediment cores were sampled from Xiamen Western Bay at five sites during the summer and winter of 2006 and Hg–Au microelectrodes
were used to make on board measurements of the concentration gradients of dissolved oxygen, Mn2+, and Fe2+ within the sediments. The O2 concentrations decreased sharply from about 200 μmol L−1 in the bottom seawater to zero within a depth of a few millimeters into the sediment. Dissolved Mn2+ was detected below the oxic zones with peak concentrations up to 600 μmol L−1, whereas dissolved Fe2+ had peak concentrations up to 1,000 μmol L−1 in deeper layers. The elemental contents of organic carbon and nitrogen within the sediments were analyzed and their C/N
ratios were in the range of 9.0 to 10.1, indicative of heavy terrestrial origin. Sediments from two sites near municipal wastewater
discharge outlets had higher organic contents than those from the other sites. These high organic contents corresponded to
shallow O2 penetration depths, high dissolved Mn2+ and Fe2+ concentrations, and negative redox potentials within the sediments. This indicated that the high organic matter content had
promoted microbial respiration within the sediments. Overall, the organic content did not show any appreciable decrease with
increasing sediment depths, so a quadratic polynomial function was used to fit the curve of O2 profiles within the sediments. Based on the O2 profiles, O2 fluxes across the seawater and sediment interface were estimated to be in the range 6.07 to 14.9 mmol m−2 day−1, and organic carbon consumption rates within the surface sediments were estimated to be in the range 3.3 to 20.8 mgC cm−3 a−1. The case demonstrated that biogeochemistry within the sediments of the bay was very sensitive to human activities such as
sewage discharge. 相似文献
12.
Phosphorus Speciation in Stream Bed Sediments from an Agricultural Watershed: Solid-Phase Associations and Sorption Behavior 总被引:1,自引:0,他引:1
The sorption behavior and solid-phase associations of phosphorus (P) in fine-grained sediments (<63 μm) from two upstream
tributaries and one downstream main stem site of the Spoon River in west-central Illinois were characterized to better understand
phosphorus bioavailability in this agriculturally dominated watershed. The P sorption affinities, as indicated by linear distribution
coefficients (K
d), of all sediments were 330–5,150 L/kg, and negatively correlated with equilibrium phosphorus concentration (EPCo) values, which ranged between 0.2 and 2.2 μM. pH values measured at the conclusion of the sorption experiments varied only
slightly (7.45–8.10) but were nonetheless strongly positively correlated to EPCo values, and negatively correlated to K
d values, suggesting the importance of pH to the observed sorption behavior. K
d values were generally lower and EPCo values higher at the main stem site than at the upstream tributary sites, suggesting dissolved reactive P (DRP) bioavailability
(specifically orthophosphate) increased downstream. The solid phase associations of P were operationally assessed with the
streamlined SEDEX (sedimentary extraction) procedure, and most sediment P (≥50%) was released during the step designed to
determine iron oxide–associated P. On average, 70–90% of the total sediment P pool was potentially bioavailable, as estimated
by the sum of the iron oxide-, authigenic carbonate-, and organic-associated P fractions. Considerable calcium was also extracted
from some sediments during the step designed to specifically remove iron oxide–associated P. It is hypothesized that the severe
drought conditions that persisted between April and October, 2005 allowed authigenic carbonates (perhaps partly amorphous)
to accumulate, and that these carbonates dissolved during the iron oxide extraction step. The extensive benthic algal populations
also present may have aided carbonate precipitation, which under more normal hydrologic conditions would be periodically flushed
downstream and replaced by fresh sediment. This suggests antecedent hydrologic conditions played a dominant role in the P
sorption and solid phase associations identified. 相似文献
13.
A systematic study of the granulometric properties and the occurrence and distribution of rare earth elements (REE) within
surface sediments from ten bays situated along the coast of Southeast China has facilitated a more rigorous understanding
of constraints on sediment provenance in the area. The results show that REE concentrations are similar within a single bay,
but vary considerably (133.58–251.77 mg/kg) among the bays. The chondrite-normalized distribution patterns show the typical
enrichment of light REEs (LREEs: La–Eu) relative to heavy REEs (HREEs: Gd–Lu), and an apparent depletion of Eu, which is diagnostic
of a terrigenous sediment source. Obvious enrichments of the middle REEs (MREEs: Sm–Ho) in the PAAS-normalized (Post-Archean
Australian Shale) distribution patterns of these bay sediments are similar to results reported from large rivers in China.
Comparing the REE composition of the bay sediments with those of adjoining fluvial sediments and with the bedrock of the surrounding
drainage basins, the latter are indicated as the dominant sediment source. The uniform REE distribution patterns, and MREE
enrichments, prove that the sediments are derived from the material transported by the streams and rivers that discharge into
the bays. 相似文献
14.
Mobility and ecological risk assessment of heavy metals in surface sediments of Xiamen Bay and its adjacent areas,China 总被引:4,自引:1,他引:3
Xiamen Bay (XMB) has received substantial loadings of pollutants from industrial and municipal wastewater discharged since
the 1980s. To assess ecological risks and the current spatial changes of metal contaminants in bottom surface sediments, 12
samples were collected. Samples were subjected to a total digestion technique and analyzed by ICP–OES for Cu, Pb, Zn, Cr,
and Cd, and by AFS for Hg and As. Among these metals, Zn had the highest values (68–268 mg kg−1), followed by Pb (27–71 mg kg−1), and lower concentrations were found for Cd (42–1,913 μg kg−1) and Hg (0–442 μg kg−1). In comparison with the average crustal abundance values, the results indicated that nearly half of the sediment samples
of XMB and its adjacent areas were contaminated by Cd, Pb, Zn, and As. Furthermore, based on the modified BCR sequential extraction
procedure, the chemical speciation of heavy metals (Cd, Cr, Cu, Pb, Zn, Hg, and As) in selected sediment samples were evaluated
in this study. Data from BCR sequential extractions indicated that Cd posed a medium ecological risk, whereas, Cr posed low
risk since its exchangeable and carbonate fractions were below 4%, and the mobility of heavy metals in XMB decreased in the
order Cd > Pb > Cu > Zn > Hg > As > Cr. By applying mean effects range median quotients (mERMQ), the results showed that Yuandang
Lagoon with mERMQ value >0.5 would be expected to have the greatest potential toxic risk in amphipod within XMB and its adjacent
areas. 相似文献
15.
Source and distribution of trace metals and nutrients in Narmada and Tapti river basins,India 总被引:2,自引:1,他引:1
The study was designed to establish the distributions of trace metals, dissolved organic carbon, and inorganic nutrients as
well as to assess the extent of anthropogenic inputs into the Narmada and Tapti rivers. Water and sediment qualities are variable
in the rivers, and there are major pollution problems at certain locations, mainly associated with urban and industrial centers.
The metal concentrations of samples of the aquatic compartments investigated were close to the maximum permissible concentration
for the survival of aquatic life, except for higher values of Cu (5–763 μg l−1), Pb (24–376 μg l−1), Zn (24–730 μg l−1), and Cr (70–740 μg l−1) and for drinking water except for elevated concentrations of metals such as Pb, Fe (850–2,060 μg l−1), Cr, and Ni (20–120 μg l−1). In general, the concentrations of trace metals in the rivers vary down stream which may affect the “health” of the aquatic
ecosystem and may also affect the health of the rural community that depends on the untreated river water directly for domestic
use. The assessment of EF, I
geo, and PLI in the sediments reveals overall moderate pollution in the river basins. 相似文献
16.
Geochemical study of arsenic and other trace elements in groundwater and sediments of the Old Brahmaputra River Plain,Bangladesh 总被引:1,自引:1,他引:0
Faruque Ahmed M. Hawa Bibi Hiroaki Ishiga Takehiko Fukushima Teruyuki Maruoka 《Environmental Earth Sciences》2010,60(6):1303-1316
The geochemical study of groundwaters and core sediments from the Old Brahmaputra plain of Bangladesh was conducted to investigate
the distribution of arsenic and related trace elements. Groundwaters from tube wells are characterized by pH of 6.4–7.4, dissolved
oxygen (DO) of 0.8–1.8 mg/l, Ca contents of 5–50 mg/l, and Fe contents of 0.2–12.9 mg/l. Arsenic concentrations ranged from
8 to 251 μg/l, with an average value of 63 μg/l. A strong positive correlation exists between As and Fe (r
2 = 0.802; p = 0.001) concentrations in groundwater. The stratigraphic sequences in the cores consist of yellowish silty clays at top,
passing downward into grayish to yellowish clays and sands. The uppermost 3 m and lower parts (from 13 to 31 m) of the core
sediments are oxidized (average oxidation reduction potential (ORP) +170 and +220 mV, respectively), and the ORP values gradually
become negative from 3 to 13 m depths (−35 to −180 mV), indicating that anoxic conditions prevail in the shallow aquifers
of the Brahmaputra plain. Age determinations suggest that clay horizons at ~10 m depth were deposited at around 2,000 and
5,000 years BP (14C ages) during the transgressive phase of sea-level change. Elevated concentrations of As, Pb, Zn, Cu, Ni, Cr, and V are present
in the silts and clays, probably due to adsorption onto clay particles. Significant concentrations of As occur in black peat
and peaty sediments at depths between 9 and 13 m. A strong positive correlation between As and Fe was found in the sediments,
indicating As may be adsorbed onto Fe oxides in aquifer sediments. 相似文献
17.
Ana Carolina Ruiz-Fernández José Luis Marrugo-Negrete Roberth Paternina-Uribe Libia Hascibe Pérez-Bernal 《Estuaries and Coasts》2011,34(6):1117-1128
With the aim of evaluating temporal changes in sedimentation and organic carbon (Corg) supplied over the last ~100 years, a sediment core was collected at Soledad Lagoon, a costal ecosystem surrounded by mangroves,
located in the Cispatá Estuary (Caribbean coast of Colombia). The core sediments were characterized by low concentrations
of calcium carbonate (0.2–2.9%), organic matter (3–8%), total nitrogen (0.11–0.38%), and total phosphorus (0.19–0.65 mg g−1). Fe and Al concentrations ranged from 4% to 5%, and Mn from 356 to 1,047 μg g−1. The 210Pb-derived sediment and mass accumulation rates were 1.54 ± 0.18 mm year−1 and 0.08 ± 0.01 g cm−2 year−1, respectively. The sediment core did not provide evidence of human impact, such as enhancement of primary production or nutrient
enrichment, which may result from recent land uses changes or climate change. The Corg fluxes estimated for Soledad Lagoon core lay in the higher side of carbon fluxes to coastal ecosystems (314–409 g m−2 year−1) and the relatively high Corg preservation observed (~45%) indicate that these lagoon sediments has been a net and efficient sink of Corg during the last century, which corroborate the importance of mangrove areas as important sites for carbon burial and therefore,
long-term sequestration of Corg. 相似文献
18.
A large pool of nitrogen in the sediment pore fluid of a eutrophic lake in Iowa, USA, was mapped in this study. Previously,
the lake had supported fishing and boating, but today it no longer supports its designated uses as a recreational water body.
In the top 5 cm of the lake bottom, the pore water nitrogen ranges between 3.1 and 1,250 μg/cm3 of sediments, with an average of 160.3 μg/cm3. Vertically, nitrate concentrations were measured as 153 μg/cm3 at 0–10 cm, 162 μg/cm3 at 10–20 cm, and 32 μg/cm3 at 20–30 cm. Nitrate mass distribution was quantified as 3.67 × 103 kg (65%) in the bottom sediments, 172 kg (3%) in suspended particulates, and 1.83 × 103 kg (32%) in the dissolved phase. Soil runoff nutrients arrive at the lake from the heavily fertilized lands in the watershed.
Upon sedimentation, a large mass of nitrogen desorbs from mineral particles to the relatively immobile pore fluid. Under favorable
conditions, this nitrogen diffuses back into the water column, thereby dramatically limiting the lake’s capability to process
incoming nutrients from farmlands. Consequently, a condition of oxygen deficiency disrupts the post-season biological activities
in the lake. 相似文献
19.
Vertical distribution patterns of organic geochemical constituents and the enzymes aminopeptidase and β-glucosidase provide
insights about the nature and reactivity of sediment organic matter in the sandy sediments of two shallow “South Texas” estuaries.
Sediment total organic carbon (TOC) δ13C values indicated that the organic matter (OM) was derived more from a mixture of seagrass and phytoplankton than from terrigenous
OM. Down-core amounts of TOC and total nitrogen (TN) were <0.2% of dry weight, respectively. Enzyme activities were highest
near surface and ranged from 25 to 1 μM/h for aminopeptidase as compared to 5 to 0.2 μM/h for glucosidase. In Aransas Bay,
aminopeptidase activity correlated with sediment TN content (r
s = 0.30) and β-glucosidase with TOC content (r
s = 0.27). In Copano Bay, aminopeptidase correlated with TOC, TN, and carbohydrate content (r
s = 0.89, 0.90, and 0.83, respectively). Variations of glucosidase activity also related positively to TOC, TN, and total carbohydrate
content (r
s = 0.68, 0.77, and 0.48, respectively). Overall, enzyme activities in these low OM, sandy sediments resembled those for other
benthic marine environments. 相似文献
20.
F. Ruiz J. Borrego M. L. González-Regalado N. López-González B. Carro M. Abad 《Environmental Geology》2009,58(4):779-783
The analysis of a short core collected in the Tinto Estuary (SW Spain) permits to delimitate the influence of historical mining
activities on sediments and microfauna (Foraminifera and Ostracoda). In very shallow palaeochannels of the middle estuary,
a first mining period (~3,600 cal years BP) caused high sediment pollution by Cu, with a significant diminution of the palaeontological
record due to continuous acid mining drainage processes. In this core, the polluted levels derived from both Roman extractions
(2,000–1,900 years BP) and the extensive mining activities between 1870 and 1935 have been eroded. The 1,800–200 years BP
period is characterized by a limited mining activity and an important improvement of this ecosystem. In addition, the effects
of recent industrial wastes have been limited in this area. 相似文献