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1.
Shallow marine sediments of the Buyat-Ratototok district of North Sulawesi, Indonesia, are affected by submarine disposal
of industrial gold mine tailings and small-scale gold mining using mercury amalgamation. Industrial mine tailings contained
590–660 ppm arsenic, 490–580 ppm antimony, and 0.8–5.8 ppm mercury. Electron microprobe survey found both colloidal iron–arsenic-phases
without sulphur and arsenian pyrite in tailings and sites to which tailings had dispersed, but only arsenopyrite in sediments
affected by artisanal mining. Antimony in tailings was present as antimony oxides, colloidal iron–antimony phases, colloidal
iron–antimony phases, and stibnite in sediments affected by both types of mining. A sequential extraction found that 2% of
arsenic held in tailings and tailings-contaminated sediments was exchangeable, 20–30% was labile, including weakly adsorbed,
carbonate- and arsenate bound, 20–30% was metastable, probably incorporated into iron or manganese oxyhydroxides, or strongly
adsorbed to silicate minerals, and 40–48% was relatively insoluble, probably incorporated into sulphides or silicates. Arsenic
in sediments affected by artisanal gold mining was 75–95% relatively insoluble. Antimony in all sediments was >90% relatively
insoluble. Relative solubility patterns of most other metals did not differ between industrial tailings-affected, artisanal-mining
affected areas, and fluvial sediments. Results suggest that submarine tailings disposal is not suitable for refractory Carlin-like
gold deposits because ore processing converts arsenic to forms unstable in anoxic marine sediments.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
2.
Transport of terrestrial organic carbon to the oceans by rivers: re-estimating flux- and burial rates 总被引:5,自引:0,他引:5
This study re-estimates one important component in the global carbon cycle: the modern global fluviatile organic carbon discharge-
and burial rates. According to these results, approximately 430×1012 g of terrestrial organic carbon are transported to the ocean in modern times. This amount is higher than the latest estimates
but takes into account new data from Oceania not previously considered in global flux studies. However, only the minor amount
of 10% or approximately 43×1012 gC year–1 is most likely buried in marine sediments. This amount is similar to the burial of marine organic carbon in the coastal ocean
(55×1012 gC year–1). Adding both estimates gives approximately 100×1012 gC year–1, which is the value calculated by Berner (1982) for "terrestrial" deltaic-shelf sediments. However, the results in this study
suggest that on a global scale the organic carbon content in coastal ocean sediments is not solely of terrestrial origin but
a mixture of nearly equal amounts of marine and terrestrial organic carbon. The major part of the terrestrial organic carbon
that enters the ocean by rivers (approximately 400×1012 gC year–1) seems to be either (a) remineralised in the ocean, whereas the mechanism by which the terrestrial organic carbon is oxidised
in the ocean are unknown; or (b) is dispersed throughout the oceans and accumulates in pelagic sediments.
Received: 9 November 1998 / Accepted: 25 May 1999 相似文献
3.
Processes of authigenic manganese ore formation in sediments of the northern equatorial Pacific are considered on the basis
of study of the surface layer (<2 mm) of ferromanganese nodule and four micronodule size fractions from the associated surface
sediment (0–7 cm). Inhomogeneity of the nodule composition is shown. The Mn/Fe ratio is maximal in samples taken from the
lateral sectors of nodule at the water-sediment interface. Compositional differences of nodules are related to the preferential
accumulation of microelements in iron oxyhydroxides (P, Sr, Pb, U, Bi, Th, Y, and REE), manganese hydroxides (Co, Ni, Cu,
Zn, Cd, Mo, Tl, W), and lithogenous component trapped during nodule growth (Ga, Rb, Ba, and Cs). The Ce accumulation in the
REE composition is maximal in the upper and lower parts of the nodule characterized by the minimal Mn/Fe values. The compositional
comparison of manganese micronodules and surface layers of the nodule demonstrated that the micronodule material was subjected
to a more intense reworking during the diagenesis of sediments. The micronodules are characterized by higher Mn/Fe and P/Fe
ratios but lower Ni/Cu and Co/Ni ratios. The micronodules and nodules do not differ in terms of contents of Ce and Th that
are least mobile elements during the diagenesis of elements. Differences in the chemical composition of micronodules and nodules
are related not only to the additional input of Mn in the process of diagenesis, but also to the transformation of iron oxyhydroxides
after the removal of Mn from the close association with Fe formed in the suspended matter at the stage of sedimentation. 相似文献
4.
D. Lal 《Journal of Earth System Science》2000,109(1):181-186
The radionuclide10Be (half-life = 1.5my), produced naturally in the Earth’s atmosphere by nuclear interactions of cosmic rays, was sought in
ocean sediments in the late fifties, considering its potential usefulness as a radiotracer for dating sediments.10Be was discovered independently by two groups, one in India and the other in the USA, and used only for dating marine sediments
and manganese nodules until the seventies. Subsequently, as a result of a technical advance resulting in the improvement in
the sensitivity of measurement of10Be by about a factor of 106, there was a global rush to measure this nuclide in most materials participating in the physical, chemical and biological
processes in the dynamic geosphere. This paper outlines the reasons for this “isotope rush”, and the lessons learned from
these studies. I also present my personal views of the special attractive features of this nuclide on the one hand, and on
the other, the pitfalls or the wrong message this nuclide could convey! 相似文献
5.
The sedimentation and ore formation were studied in sediments from nine stations located in the 24°W profile in the Brazil
Basin of the Atlantic Ocean. The sediments are represented by mio- and hemipelagic muds, which are variably enriched in hydrothermal
iron and manganese oxyhydroxides. As compared to the sediments from other basins of the Atlantic Ocean, these rocks are marked
by extremely high manganese contents (up to 1.33%) and maximal enrichment in Ce. It was shown that the positive Ce anomaly
is related to the REE accumulation on iron oxyhydroxides. Influence of hydrothermal source leads to the decrease of Ce anomaly
and LREE/HREE ratio. In the reduced sediments, preservation of positive Ce anomaly and/or its disappearance was observed after
iron and manganese reduction. The REE contents were determined for the first time in the Ethmodiscus oozes of the Brazil Basin. Ore deposits of the Brazil Basin are represented by ferromanganese crust and ferromanganese nodules.
Judging from the contents of iron, manganese, rare, and trace elements, these formations are ascribed to the sedimentation
(hydrogenic) deposits. They are characterized by a notable positive Ce anomaly in the REE pattern. The extremely high Ce content
(up to 96% of total REE) was discovered for the first time in the buried nodules (Mn/Fe = 0.88). 相似文献
6.
Trace element concentrations in shallow marine sediments of the Buyat-Ratototok district of North Sulawesi, Indonesia, are
affected by submarine disposal of industrial gold mine tailings and unregulated dumping of tailings and wastewater from small-scale
gold mining using mercury amalgamation. Industrial mine tailings contained 590–690 ppm arsenic, 490–580 ppm antimony, and
0.8–5.8 ppm mercury. Tailings-affected sediment As and Sb concentrations were 20–30 times higher than in muddy sediments not
contaminated with tailings, and 50–60 times higher than pre-mining average. Highest mercury concentrations were observed in
sediments affected by small-scale mining using mercury amalgamation (5–29 ppm). Concentrations of most other trace elements
were comparable in sediments affected by both types of mining and were slightly higher than regional averages for sediments
collected before the onset of industrial mining. Elevated concentrations of both As and Sb in approximately equal proportions
suggest tailings dispersal of at least 3.5 km. Mercury released from artisanal gold mining dispersed up to 4 km from river
mouths. Slight increases in concentrations of non-mercury trace elements in areas affected by artisanal mining over pre-industrial
mining concentrations were probably caused by increased rates of erosion.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
7.
Analysis of 3-m sediment cores revealed that profiles of carbon (C), sulfur (S), and iron (Fe) varied with relative distance from marine and terrestrial sediment sources in Tomales Bay California. Despite relatively high sedimentation rates throughout the bay (historically 3–30 mm yr−1), sulfate reduction of deposited organic matter led to free-sulfide accumulation in sediments only at the location farthest from terrestrial runoff, the source of reactive iron. Acid-volatile sulfide concentrations in all sediments (<10 μmol g−1) were low relative to concentrations of chromiumreducible sulfide (up to 400 μmol g−1 farthest from the reactive iron source). A calculated index of iron availability, used to describe sediment resistance to build-up of free sulfide, was lowest at this location. Recent, upward shifts in reactive Fe concentration and in the relative contribution of terrestrial orgnic carbon (measured as a shift in δ13C of bulk sediment organic matter) in all cores indicated that erosion and transport of sediments from the watershed surrounding Tomales Bay increased after European settlement in the 1850s. 相似文献
8.
为合理有效地提取和利用大洋金属资源,在对大洋锰结核化学成分及矿物组成进行测定的基础上,采用分布溶解法对钴的赋存状态进行了分析.选择还原氨浸法对大洋锰结核中的多金属进行了浸取实验,并用铵黄铁矾法对浸取液进行了除铁及用硫化沉淀法对钴进行分离提取等实验.结果表明:大洋锰结核中钴的质量分数可达0.30%,且主要以硅酸钴、氧化钴和硫化钴的形式存在.氨浸提取可以有效地使金属离子从结核中溶出,其中钴的浸出率最高可达93.25%;铵黄铁矾法可将浸出液中的铁全部去除.提取的硫化钴中除含有少量铬外未见其它杂质元素. 相似文献
9.
The marine coastal sediments from Togo have been analysed for the trace elements Cd, Cr, Cu, Ni, Pb, Sr, V, Zn and Zr to
ascertain the geo-ecological impact of dumping of phosphorite tailings into the sea. Trace element concentrations ranged from
2–44 ppm for Cd, 22–184 ppm for Cu, 19–281 ppm for Ni, 22–176 ppm for Pb, 179–643 ppm for Sr, 38–329 ppm for V, 60–632 ppm
for Zn and 18–8928 ppm for Zr. Regional distribution of trace elements in the marine environment indicates that the concentrations
of Cr, Cu, Ni, Pb, V, Sr and Zn increase seawards and along the coastal line outwards of the tailing outfall, whereas Cd and
Zr showed reversed spatial patterns. Sorting and transport of phosphorite particles by coastal currents are the main factors
controlling the distribution of particle-bound trace metals in the coastal environment. The Cd, Sr and Zn concentrations decrease
with decreasing grain size in marine coastal sediments, whereas Cr, Cu, Ni and Zn concentrations increase with decreasing
grain size. Percolation and shaking experiments were carried out in laboratory using raw phosphate material and artificial
sea water. Enhanced mobilization of Cd from phosphorites by contact with the sea water was observed.
Received: 11 May 1998 · Accepted: 20 October 1998 相似文献
10.
A. Bollhöfer A. Eisenhauer N. Frank D. Pech A. Mangini 《International Journal of Earth Sciences》1996,85(3):577-585
Thorium- and uranium isotopes were measured in a diagenetic manganese nodule from the Peru basin applying alpha- and thermal
ionization mass spectrometry (TIMS). Alpha-counting of 62 samples was carried out with a depth resolution of 0.4 mm to gain
a high-resolution230Thexcess profile. In addition, 17 samples were measured with TIMS to obtain precise isotope concentrations and isotope ratios. We
got values of 0.06–0.59 ppb (230Th), 0.43–1.40 ppm (232Th), 0.09–0.49 ppb (234U) and 1.66–8.24 ppm (238U). The uranium activity ratio in the uppermost samples (1–6 mm) and in two further sections in the nodule at 12.5±1.0 mm
and 27.3–33.5 mm comes close to the present ocean water value of 1.144±0.004. In two other sections of the nodule, this ratio
is significantly higher, probably reflecting incorporation of diagenetic uranium. The upper 25 mm section of the Mn nodule
shows a relatively smooth exponential decrease in the230Thexcess concentration (TIMS). The slope of the best fit yields a growth rate of 110 mm/Ma up to 24.5 mm depth. The section from 25
to 30.3 mm depth shows constant230Thexcess concentrations probably due to growth rates even faster than those in the top section of the nodule. From 33 to 50 mm depth,
the growth rate is approximately 60 mm/Ma. Two layers in the nodule with distinct laminations (11–15 and 28–33 mm depth) probably
formed during the transition from isotopic stage 8 to 7 and in stage 5e, respectively. The Mn/Fe ratio shows higher values
during interglacials 5 and 7, and lower ones during glacials 4 and 6. A comparison of our data with data from adjacent sediment
cores suggests (a) a variable supply of hydrothermal Mn to sediments and Mn nodules of the Peru basin or (b) suboxic conditions
at the water sediment interface during periods with lower Mn/Fe ratios. 相似文献
11.
海相沉积型锰矿的成矿过程受古海洋沉积环境影响,而古海洋环境又与超大陆聚合与裂解、极端地质事件、生命演化等密切相关,因此,海相富锰地层是岩石圈、水圈、大气圈和生物圈等多圈层耦合关系与物质循环相关信息的重要载体。深层海水缺氧模型、最小氧化带模型和幕式充氧模型都显示海水中氧化还原梯度的变化是导致锰矿形成的最主要原因。全球范围内海相沉积型锰矿主要形成于古元古代、新元古代和显生宙3个地质历史时期。其中,元古宙时期,地球上发育了完善的氧化还原分层的古海洋结构;古元古代早期和新元古代,超大陆裂解引起的海平面升降变化导致古海洋氧化还原结构产生动荡,并促使大规模沉积型锰成矿作用发生;地球沉寂期(1800~800 Ma)涵盖了整个中元古代,这一时期仅在华北地台发育了少量沉积型锰矿床,反映该时期古海洋中锰的迁移受到了抑制;显生宙地球再次进入活跃期,经历了数次海洋缺氧事件,冰室-温室气候交替促使海水的化学性质剧烈变化,并在局部氧化还原分层的沉积盆地中富集形成沉积型锰矿床。总之,古海洋氧化还原环境的变化是沉积型锰矿形成的必要条件,同时,区域性沉积盆地的结构、海平面的升降、火山作用导致的物缘供给等多种因素都会影响沉积型锰矿的形成。与沉积型铁矿相比,沉积型锰矿对局部海水化学性质的变化更加敏感,综合研究铁锰矿床的共生与分异过程,将有助于更加有效的识别不同尺度的沉积过程与古海洋环境变化。 相似文献
12.
在甘孜—理塘结合带内理塘县中木拉乡附近发现锰结核。通过地质填图和综合研究,该锰结核产于结合带内瓦能蛇绿混杂岩组中的黑色粉砂质板岩中。其沉积层序为玄武岩→硅质岩→含锰结核粉砂质板岩。锰结核主量元素具有高Mn、低Fe、Si、Ca的特点,其中Mn含量为42.19%,高出大洋锰结核平均值1.83倍,Mn/Fe值较高,达8.1。锰结核中除Cr高于大洋锰结核平均值2~7倍外,多数微量元素低于大洋锰结核平均值。稀土元素具有较明显的Ce正异常,稀土总量、轻重稀土分异程度、Eu异常特征与混杂岩中的砂岩、硅质岩近似,而与玄武岩差别较大。该锰结核产出于大陆边缘构造环境,火山活动微弱,代表甘孜—理塘洋扩张到最大程度时的沉积。其时甘孜—理塘洋规模仍是有限的。 相似文献
13.
Iron oxyhydroxide precipitates associated with acid mine drainage (AMD) from the Stearns Coal Zone in southeastern Kentucky
were analyzed for their metal (Al, Cu, Pb, Mn, Ni, and Zn) content. The most concentrated metals within these sediments are
nickel (27–32×103μmol/kg), manganese (16–29×103μmol/kg), and aluminum (13–22×103μmol/kg) as determined by HCl-HNO3 digestion. Metal concentrations associated with the organic fraction as determined by H2O2 digestion were generally far lower, with the exception of aluminum. "Batch" experiments (at initial pH=2.0) were used to
analyze the stability of these metals associated with a contaminated soil. Aluminum was the most mobile of the metals, presumably
the result of the formation of aluminum-sulfate aqueous complexes. The solubilization rates for nickel and iron were very
similar, suggesting that nickel, unlike the other metals, coprecipitated with iron in these sulfatic oxyhydroxides.
Received: 9 October 1997 · Accepted: 15 December 1997 相似文献
14.
Sediments from the Mackenzie Valley — two suspended and one river bottom — were analyzed for major and minor elements, mineralogy,
particle size, and ability to release trace metals when subjected to mild leaching.
Copper and zinc in suspended sediments and cadmium in bottom sediment occurred largely (70 to 84 percent for Cu, 72 to 98
percent for Zn, 75 to 81 percent for Cd) in a form that could not easily be separated from the sediments by 0.1M HC1 and EDTA
solutions. Cadmium was present in suspended sediments in low concentrations, and was present totally in sorbed leachable form.
Iron, manganese, cobalt and chromium were separable from the particulate phase by mild leaching. It was found that approximately
70 hours were required for an apparent steady state concentration to be attained in such leachings.
Reaction of these sediments with Beaufort Sea water (salinity 22.3 parts per thousand) indicated that both iron and manganese
were released from sediments to sea water to a very small degree. Copper, lead, and zinc, however, were absorbed by sediments
from sea water. 相似文献
15.
According to the norms adopted by the National Network of observation of the marine life quality (RNO 1997) and US National Oceanic and Atmospheric Administration (US NOAA 1999), the superficial sediments of the Bizerte lagoon (northern Tunisia) show a contamination by nickel, which is the probable
consequence of the closeness to the industrial zone, and by lead, the result of detrital material rich in lead of the geological
lands of Jbel Kchabta and Jbel Messeftine. In the lagoon southern and eastern sectors, the contamination of superficial sediments
is essentially by copper, zinc, nickel and iron. This pollution is related, on one hand, to the rejections of the steelworks
El Fouledh and the military arsenal, and on the other hand, to Menzel Bourguiba waste disposal. The rest of the lagoon is
exempted from any metallic contamination of the surface sediments. The enriched zones in manganese and zinc correspond to
the higher contents in kaolinite and in smectite. Positive correlations were recorded between the percentage in fine fraction
on the one hand, and the sedimentary contents in TOC, total nitrogen and heavy metals on the other hand. The majority of the
analysed elements are “argilophilous” except zinc and manganese, which are clayey organophile. These results show that this
lagoon receives concentrations in anthropogenic metals that risk provoking more or less important disruptions, which are harmful
and irreversible on the fauna and flora of this lagoon and on the whole ecobiological equilibrium. 相似文献
16.
Baturin G. N. Gorshkov A. I. Magazina L. O. Bogdanova O. Yu. 《Lithology and Mineral Resources》2002,37(4):374-385
Ferruginate shells and tubular worm burrows from the oxygenated zone of the Black Sea (Kalamit Bay and Danube River mouth) are studied using transmission and scanning electron microscopy combined with analyses of elemental composition. Iron and manganese hydroxide nodules considered here are enriched in phosphorus. They contain variable amounts of terrigenous and biogenic material derived from host sediments. The hydroxides are mainly characterized by colloform structure, whereas globular and crystalline structures are less common. The dominating iron phase is represented by ferroxyhite and protoferroxyhite, whereas the manganese phase is composed of Fe-free vernadite. Relative to sediments, concentrations of Mn, As, and Mo increase 12–18 times, while concentrations of Fe, P, Ni, and Co increase 5–7 times during the nodule formation. 相似文献
17.
Mitchell Lyle 《Geochimica et cosmochimica acta》1982,46(11):2301-2306
Using available information on the accretion rates and the bulk chemical compositions of oceanic ferromanganese nodules, it can be shown that the accumulation rate of manganese is proportional to the square of the accumulation rate of iron. This relationship has been used to derive an equation that predicts nodule growth rates from their chemical compositions. The equation accurately predicts growth rates up to about 50 mm/106 yr, but yields incorrect rates for faster-growing concretions. From this relationship nodules underneath water of high primary productivity grow most rapidly and accumulate transition metals most rapidly; however, nodules from regions of highest primary productivity do not have the highest concentrations of nickel and copper. Reduction of manganese within the sediment column and remobilization of a fraction to the surface sediments adds manganese to nodules without substantially augmenting the supply of other transition elements. The addition of remobilized manganese to the nodule dilutes the concentrations of nickel, copper and iron, even though their rates of accumulation are also high. 相似文献
18.
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
19.
A. V. Dubinin T. Yu. Uspenskaya M. N. Rimskaya-Korsakova T. P. Demidova 《Lithology and Mineral Resources》2017,52(2):81-101
The Sr isotope stratigraphy of the biogenic apatite was used to determine the age of pelagic sediments in the Brazil Basin (Station 1541) that contain ferromanganese micronodules, nodules, and coatings on the weathered volcanic rocks. The age of sediments at horizons 0–5 and 86–90 cm was estimated at 24.1 ± 0.2 Ma and 24.8 ± 0.2 Ma, respectively. The average sedimentation rate in the Late Oligocene was about 13 mm/ka. The hydrogenous Fe–Mn nodule on the sediment surface with the Mn/Fe value of 1.05–1.95 was formed at a rate of 1.2–2.4 mm/Ma, which is 1000 times lower than the growth rate of buried nodule (Mn/Fe 0.4) at depth of 83 cm. Diagenesis provoked changes in the mineral composition of the buried nodule (asbolane-buserite partially replaced by goethite), leading to the loss of a part of Mn, Ni, Li, and Tl but accumulation of trace elements linked with iron oxyhydroxides (Ce, Th, Be, As, and V) were retained. The composition of manganese micronodules at two studied depths in sediments evolved in the course of two stages of ore formation: related to the oxic and suboxic diagenesis. The Sr isotopic composition in manganese micronodules from both horizons do not differ from that of dissolved Sr in the ocean water. The 143Nd/144Nd ratio, which reflects the Nd isotopic composition in the paleocean during the micronodule formation, varies in manganese micronodules from different horizons and is constant in different size fractions. 相似文献
20.
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