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1.
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
2.
水体中富营养化水平与磷元素的赋存形态密切相关。目前围绕引起富营养化关键因子之一的磷形态的垂向分布特征、各磷形态间的迁移转化行为及其影响因素取得了比较明确的研究进展。为进一步揭示不同磷形态在沉积物-水体系中迁移转化行为随时空的变化特征,本文采用磷钼蓝分光光度法对沱江流域简阳段间隙水中可溶性活性磷(SRP)、可溶性非活性磷(SUP)及总溶解性磷(TDP)进行测定;采用SMT法和改进的沉积物无机磷形态连续提取法对沉积物中总无机磷(TIP)、总磷(TP)、难提取磷(Res-P)、可交换态磷(Exc-P)、铁结合态磷(Fe-P)、铝结合态磷(Al-P)、钙结合态磷(Ca-P)进行提取,磷钼蓝分光光度法进行测定,以揭示沉积物-水体系中磷的赋存形态垂向分布行为特征,并将实验数据与十年前该地区磷的赋存形态结果进行对比,探讨磷赋存形态的变化趋势及影响因素。结果表明:间隙水中SRP、SUP和TDP的含量分别为0.004～0.36mg/L、0.080～3.19mg/L和0.056～3.28mg/L;沉积物中TP、TIP、Res-P、Exc-P、Al-P、Ca-P含量分别为1235.40～1646.94mg/kg、860.00～1318.59mg/kg、130.31～537.13mg/kg、1.35～14.10mg/kg、0.007～0.12mg/kg、743.13～1109.91mg/kg,Fe-P未检出。对比十年前后沉积物-水体系中磷赋存形态的变化可知,由于受到外源磷输入的影响,间隙水中SRP、SUP以及TDP含量虽然在-10cm以上变化不明显,但在-10cm以下明显增大,且导致沉积物中TP、TIP含量增加;偏碱性的沉积环境导致Al-P的释放,其含量明显减小;Exc-P含量的减小与其转化为稳定的Ca-P或Res-P形态有关。研究认为:随着时空的变化,沱江简阳段沉积物呈现外源磷输入和内源磷释放的综合污染。总体而言,由于输入的磷形态大部分以稳定的Ca-P和Res-P形态存在于沉积物中,使得表层间隙水中生物可直接利用的磷含量总体变化不大,该地区富营养化程度不会加重。维持沉积环境的弱碱性,有利于Al-P、Exc-P等向Ca-P的有效转换,抑制河流富营养化。 相似文献
3.
太湖及其主要入湖河流沉积磷形态分布研究 总被引：57，自引：6，他引：57
选择了我国第三大浅水湖泊--太湖及其主要入湖河流进行沉积磷形态的连续提取研究.太湖湖区沉积磷中不稳态磷(LP)及铝结合态磷(Al-P)含量很低,其余形态磷为铁结合态磷(Fe-P)＜钙结合态磷(Ca-P)＜有机磷(Org-P).河流沉积物中有机磷的相对含量高于湖泊沉积物,绝对含量平均值约为湖泊沉积物的3.9倍,铁结合态磷的绝对含量约为湖泊沉积物的3/4,湖区沉积物Fe-P含量与水体中PO3-4-、Chla呈显著正相关关系,同时与间隙水的氧化性呈显著负相关关系.太湖各湖区沉积物的磷形态表现为空间差异较大,活性组分的差异性要大于活性较差的组分.总的来说北部湖区沉积物中Fe-P和Org-P含量高于其他湖区,这与太湖北部湖区水体高营养级和藻类爆发关系密切.湖区沉积磷的垂直分布规律较复杂,既有随深度增加的,也有随深度降低的,河流沉积物同样如此.这与太湖及河流生态条件、污染物排放以及沉积动力学条件不同有关. 相似文献
4.
5.
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
6.
永定河沉积物中磷的存在形态及其指示意义 总被引：11，自引：3，他引：11
采集官厅水库的永定河入库口附近沉积物,采集深度77cm,以1cm做为一个层位单元进行分割,测定其中11个层位的总磷,同时对这些层位沉积物中二钙结合态磷、八钙结合态磷、铝结合态磷、铁结合态磷进行连续分级提取,有机磷通过灼烧法测定,残留态磷由总磷与上述五种形态磷差减确定。结果显示:沉积物中总磷含量在580.3~1276.2μg/g,主要成分为无机磷,平均占总磷的比例为88%;残留态磷为沉积物中磷的主要形态,含量占总磷50%以上。在沉积物深度75~20cm的沉积年份中,永定河向官厅水库输送的残留态磷量不断增加,且增速逐渐加快,主要为水土侵蚀的产物。从沉积深度20cm以来的沉积年份里,总磷的输入量不断减少,但以二钙结合态磷为主的生物有效磷输入量随总磷的含量降低而持续增加,主要来自工业和生活污水,反映了官厅水库上游永定河流域内工业和生活污水排放所占的比重日益增加,成为官厅水库富营养化污染的主要来源,以致官厅水库富营养化的趋势增强。 相似文献
7.
平水期洞庭湖不同形态磷赋存特征 总被引：4，自引：0，他引：4
通过现场调查和室内实验,对平水期洞庭湖24个断面上覆水-沉积物磷的污染程度、分布特征进行研究;同时,分析了各形态磷间的相关性,探讨了磷的赋存形态对水体富营养化的影响、沉积物释放量和释放风险。结果表明,水体内总磷分布规律为南洞庭西洞庭东洞庭大通湖,东洞庭湖以颗粒态磷为主,西洞庭湖、南洞庭湖、大通湖均以溶解态磷、无机磷为主。沉积物中总磷的分布规律为南洞庭西洞庭东洞庭大通湖。东洞庭湖、西洞庭湖、南洞庭湖则以Ca-P为主,大通湖以Fe/Al-P为主。Ca-P与Fe/Al-P呈现较显著的负相关关系。大通湖释放风险较大,可释放量大;东洞庭湖有一定的可释放量,应对这两个湖泊给予较多的关注。与国内其他湖泊比较,洞庭湖沉积物中TP处于中下水平,IP在沉积物中占据较高比例。湖区沉积物中Fe/Al-P与水体中DIP、DTP、TP均具有较显著的负相关关系,存在磷的内源释放。 相似文献
8.
Phosphorus speciation in the sediment and mass balance for the central region of the Great Barrier Reef continental shelf (Australia) 总被引：1，自引：0，他引：1
Solid phase P speciation has been determined in sediments from a transect across the central section of the continental shelf and slope of the Great Barrier Reef (GBR) lagoon. This region is characterized by a gradient of riverine aluminosilicate clay and silt nearshore, seawards of which biogenic carbonate sediment predominates. Phosphorus speciation results show large variations along this transect. Organic P and authigenic (apatite) P are the major chemical forms of phosphorus in the central GBR continental shelf sediments. Post-depositional reorganization of P was also observed, converting organic P and iron bound P (Fe-P) to authigenic (apatite) P. Phosphorus burial rate was estimated from measurements of total P concentration and excess 210Pb sediment mass accumulation rates. Burial efficiency varies significantly over the shelf. Inshore areas showed significant P remobilization from sediments to the water column (up to ∼50%). The mid and the outer shelf showed little evidence for remobilization (except for coral reef platform sediments), with more of the sediment P being in the less reactive authigenic apatite phases. An appreciable fraction of this non-labile authigenic apatite phase was identified as fish bone. P sources and sinks over the central part of the GBR shelf were quantified using a mass balance approach. This showed that Coral Sea shelf edge upwelling events are essential to satisfy the large P nutrient demand of the whole GBR lagoon. P inputs due to upwelling events were greater than those contributed by local rivers over an average year. 相似文献
9.
Phosphorus distribution in the sediments of a shallow eutrophic lake,Lake Chaohu,China 总被引：8，自引：5，他引：3
Fengyu Zan Shouliang Huo Beidou Xi Qingqin Li Haiqing Liao Jingtian Zhang 《Environmental Earth Sciences》2011,62(8):1643-1653
In this study, the sediment profiles of total phosphorus (TP), inorganic phosphorus (Pi), organic phosphorus (Po), C/P and N/P were used to investigate time-dependent P distribution changes in Lake Chaohu. The characteristics of Pi and Po fractions in the surface sediments were studied and the difference between east and west lake region was also discussed.
The Pi and Po contents displayed a clear gradient from east to west in sediments of Lake Chaohu, and the Po/P ratios were lower in sediments with industrial and urban pollution sources input in west lake region. The study indicated
that different sediments area had diverse concentrations and distributions of Po fractions due to their different drainage basin and pollution sources. The profile distribution of the C/P and N/P ratios
decreased with increasing depths and stayed relatively constant ratios at the depths of 15–30 cm. The C/P and N/P ratios were
always below Redfield ratios in sediment profile, indicating P enrichment but likely due to the preferential loss of carbon
in respect to phosphorus. The rank order of Pi-fractions extracted was HCl-Pi > NaOH-Pi > NaHCO3-Pi in surface sediments. The relative distribution of NaHCO3-Pi and HCl-Pi was in agreement with the trophic conditions of the regions studied. Among the sequentially extracted Po forms, the rank order of Po fractions was residual Po > HCl-Po > fulvic acid-P > humic acid-P > NaHCO3-Po, with mean relative proportion of 5.4:3.4:2.2:1.1:1.0. 相似文献
10.
Zhenying Liu Zhaohui Jin Yawei Li Tielong Li Jiujun Gu Si Gao 《Environmental Geology》2007,52(5):997-1005
Sediment phosphorus (P) fractions and profile distribution at submerged macrophyte growth zone, emergent macrophyte growth
zone and open-water zone were studied in Wuliangsuhai Lake, China, as well as the correlations among water content, grain
size, and organic matter and P fractions. Among the three surveyed zones, the highest concentrations of most P forms occurred
in the surface sediment and the lowest between a depth of 12 and 22 cm, except HCl-P and NaOH-P. Sediment phosphorus was mainly
associated to inorganic forms (>50%) in three surveyed areas, and the highest value of inorganic phosphorus (IP) in the surface
sediment was obtained from submerged macrophyte growth zone. Submerged and emergent macrophytes increased the IP content by
107 and 44 μg/g, respectively, in the surface sediment compared with open-water zone. Vertical profiles of IP in the three
surveyed zones showed that the concentrations decreased from surface to 12 cm depth and then increased. There was a similar
trend in the sediment profiles of organic phosphorus (OP) and total phosphorus (TP), but the highest concentration of OP and
TP in surface sediment was obtained from the emergent macrophyte growth zone. Compared with open-water zone, the emergent
macrophyte increased TP content in surface sediment by 1.73 times to 1,320 μg/g, while submerged macrophyte enhanced TP content
in the surface sediment by 1.13 times to 865 μg/g. It was observed that in macrophyte growth zones, a strong linear correlation
existed between organic matter and OP (r > 0.98), and the maximum concentrations of OP were present in the areas with maximum concentrations of organic matter. Results
show that, although rooted macrophyte could uptake directly P from sediments, it is responsible for increasing the internal
P loading especially OP by reducing current velocities, attenuating wave energy and generating organic residue in Wuliangsuhai
Lake. 相似文献
11.
C. Christiansen F. Gertz M. J. C. Laima L. C. Lund-Hansen T. Vang C. Jürgensen 《Environmental Geology》1997,29(1-2):66-77
The yearly nutrient supply from land and atmosphere to the study area in SW Kattegat is 10 900 tons of N and 365 tons of
P. This is only few percent of the supply from adjacent marine areas, as the yearly transport through the study area is 218 000
tons of N and 18 250 tons of P. Yearly net deposition makes up 1340 tons of N (on average 2.5 g m–2 yr–1) and 477 ton of P (on average 0.9 g m–2 yr–1). Shallow-water parts of the study area have no net deposition because of frequent (>35% of the year) resuspension. Resuspension
frequency in deep water is <1% of the year. Resuspension rates, as averages for the study area, are 10–17 times higher than
net deposition rates. Because of resuspension, shallow-water sediments are coarse lag deposits with small amounts of organic
matter (1.1%) and nutrients (0.04% N and 0.02% P). Deep-water sediments, in contrast, are fine grained with high levels of
organic matter (11.7%) and nutrients (0.43% N and 0.15% P). Laboratory studies showed that resuspension changes the diffusive
sediment water fluxes of nutrients, oxygen consumption, and penetration into the sediment. Fluxes of dissolved reactive phosphate
from sediment to water after resuspension were negative in organic-rich sediments (13.2% organic matter) with low porosity
(56) and close to zero in coarse sediments with a low organic matter content (2.3%) and high porosity (73). Fluxes of inorganic
N after resuspension were reduced to 70% and 0–20% in relation to the rates before resuspension, respectively.
Received: 10 July 1995 · Accepted: 19 January 1996 相似文献
12.
Organic matter was isolated from the water columns and sediments of two pond systems in the south-eastern United States. Water column material was ultrafiltered to provide three fractions, i.e. <0.45 μm, but > 50,000 daltons; <50,000 daltons, but > 5000 daltons; and <5000 daltons. Sedimentary organic matter was separated into humic acid and fulvic acid fractions based on solubility criteria and the humic acid fraction was ultrafiltered to provide the same fractions as the water column isolates. All fractions were analysed for organic carbon, Al, Ca, Cu, Fe, Mg and Mn. Infra-red spectra were also measured for the sedimentary organic fractions. Organic matter isolated from the water column of the two ponds had similar organic carbon and elemental distributions, as did the organic matter isolated from the two sediments. However, significant differences in the organic carbon and elemental distributions were observed for water column and sedimentary organic matter isolated from the same pond. These studies have relevance to diagenetic alterations of organic matter and geochemical cycles of elements within lakes. 相似文献
13.
Federica Tamburini Sylvain HuonPhilipp Steinmann Francis E GroussetThierry Adatte Karl B Fllmi 《Geochimica et cosmochimica acta》2002,66(23):4069-4083
Reactive phosphorus undergoes diagenetic transformation once transferred into marine sediments. The degree of regeneration and redistribution of phosphorus depends on early diagenetic and environmental conditions, which may be linked to larger scale phenomena, such as bottom water circulation, water column ventilation, and organic carbon flux. Phosphorus phases of the <50-μm-sized fraction of deep-sea sediments from core SU 90-09 (North Atlantic, 43°31′N, 30°24′W, 3375 m below sea level) have been analyzed using a sequential extraction technique (SEDEX method) to reconstruct phosphorus geochemistry during Heinrich events 4 and 5. Comparison with Holocene samples from the same site indicates that postdeposition diagenetic transformation has not affected phosphorus distribution in the deep part of the sediments. Total and reactive phosphorus average 0.40 ± 0.04 mg/g and 0.30 ± 0.05 mg/g, respectively, and are comparable to values found in analog deep-sea environments in the North Atlantic. Detrital phosphorus, the phase linked to igneous- and metamorphic-derived material, sharply increases during Heinrich events and covaries with the ice-rafted debris record, whereas authigenic and Fe-bound phosphorus phases, both influenced by redox conditions, decrease or even disappear. These findings suggest that during the deposition of Heinrich layers (HLs), environmental parameters hampered the precipitation of these phases. Large freshwater discharges in relation to iceberg surges may have provoked a temporary stratification of the water column. Accordingly, dysaerobic conditions in the sediments may have fostered the loss of dissolved phosphorus from the sediments to the water column, in a direct and rapid response to the changed conditions. Decreasing trends in organic matter elemental ratios (total organic carbon/organic phosphorus) and Rock-Eval oxygen index values, along with the presence of partly authigenic dolomite and ankerite within HLs, also support this assumption. 相似文献
14.
The fractionation of P in Pandoh Lake surface sediments has been investigated for the first time in order to understand its environmental availability and sources, and the eutrophication status of this lake. Inorganic-P is present mainly as authigenic-P (step-III). The authigenic P concentration is higher in winter relative to the summer and monsoon seasons and ranged from 35.9 to 46.9 μg/g. The loosely sorbed or exchangeable-P (step-I), Fe(III)-bound-P (step-II) and detrital inorganic-P (step-IV) were higher in the monsoon season and varied from 3.70 to 11.1 μg/g, 16.9 to 32.0 μg/g and 9.89 to 17.0 μg/g, respectively. Organic-P reached a maximum in the summer season and ranged from 8.00 to 14.9 μg/g. Authigenic-P and detrital inorganic-P show seasonal changes, as pH influences the interaction between P and CaCO3 in the water column. In the winter season, phosphate is precipitated out of the water column and fixed in the sediments as a result of an increase in pH. Calcite-bound-P in the sediments may be redissolved by decreasing pH in the summer season. Relatively high rates of mineralization during the monsoon results in the seasonal pattern of organic-P fractionation to sediment as follows: monsoon = winter < summer. Iron, Ca, organic matter and silt and clay contents seem to play a significant role in regulating the seasonal P budget. Principal component analysis (PCA) was used to identify the factors which influence sedimentary P in the different seasons. 相似文献
15.
Water quality of Lake Baihua was found worsening in the autumn of 1994.Studies have shown that the decomposition of organic matter in the upper-level sediments resulted in seasonal anoxia with the release of P,Mn,and S^2- from the sediments to the overlying water column,and the increase of NO2^- concentration led to blackening of the water column,deat of fishes and secondary Mn pollution. 相似文献
16.
Phosphorus speciation and availability in intertidal sediments of the Yangtze Estuary,China 总被引：1，自引：0，他引：1
In order to better understand P cycling and bioavailability in the intertidal system of the Yangtze Estuary, both surface (0–5 cm) and core (30 cm long) sediments were collected and sequentially extracted to analyze the solid-phase reservoirs of sedimentary P: loosely sorbed P; Fe-bound P; authigenic P; detrital P; and organic P. The total sedimentary P in surface and core sediments ranged from 14.58–36.81 μmol g−1 and 17.11–24.55 μmol g−1, respectively, and was dominated by inorganic P. The average percentage of each fraction of P in surface sediments followed the sequence: detrital P (54.9%) > Fe-bound P (23.7%) > organic P (14.3%) > authigenic P (6.3%) > loosely sorbed P (0.8%), whereas in core sediments it followed the sequence: detrital P (61.7%) > Fe-bound P (17.0%) > authigenic P (13.1%) > organic P (7.5%) > loosely sorbed P (0.7%). Post-depositional reorganization of P was observed in both surface and core sediments, converting organic P and Fe-bound P to authigenic P. The accumulation rates and burial efficiencies of the total P in the intertidal area ranged from 118.70–904.98 μmol cm−2 a−1 and 80.29–88.11%, respectively. High burial efficiency of the total P is likely related to the high percentage of detrital P and the high sediment accumulation rate. In addition, the bioavailable P represented a significant proportion of the sedimentary P pool, which on average accounted for 37.4% and 25.1% of the total P in surface and core sediments, respectively. This result indicates that the tidal sediment is a potential internal source of P for this P-limiting estuarine ecosystem. 相似文献
17.
Fatimah Sulu-Gambari Mathilde Hagens Thilo Behrends Dorina Seitaj Filip J. R. Meysman Jack Middelburg Caroline P. Slomp 《Estuaries and Coasts》2018,41(4):921-939
Recycling of phosphorus (P) from sediments contributes to the development of bottom-water hypoxia in many coastal systems. Here, we present results of a year-long assessment of P dynamics in sediments of a seasonally hypoxic coastal marine basin (Lake Grevelingen, the Netherlands) in 2012. Sequential phosphorus extractions (SEDEX) and X-ray absorption spectroscopy (XAS) indicate that P was adsorbed to Fe-(III)-(oxyhydr)oxides when cable bacteria were active in the surface sediments in spring. With the onset of summer hypoxia, sulphide-induced dissolution of the Fe-(III)-(oxyhydr)oxides led to P release to the pore water and overlying water. The similarity in authigenic Ca-P concentrations in the sediment and suspended matter suggest that Ca-P is not formed in situ. The P burial efficiency was ≤ 32%. Hypoxia-driven sedimentary P recycling had a major impact on the water-column chemistry in the basin in 2012. Water-column monitoring data indicate up to ninefold higher surface water concentrations of phosphate in the basin in the late 1970s and a stronger hypoxia-driven seasonal P release from the sediment. The amplified release of P from the sediment in the past is attributed to the presence of a larger pool of Fe-bound P in the basin prior to the first onset of hypoxia. Given that P is not limiting, primary production in the basin has not been affected by the decadal changes in P availability and recycling over the past 40 years. The changes in P dynamics on decadal time scales were not recorded in sediment profiles of total P or organic C/total P. 相似文献
18.
Pyrite oxidation during sample storage determines phosphorus fractionation in carbonate-poor anoxic sediments 总被引：4，自引：0，他引：4
Peter Kraal Caroline P. Slomp Marcel M.M. Kuypers 《Geochimica et cosmochimica acta》2009,73(11):3277-3290
We investigated the phosphorus (P) and iron (Fe) fractionation in four cores with anoxic sediments, deposited during the mid-Cretaceous oceanic anoxic event 2 (∼94 Ma) and the Paleocene-Eocene thermal maximum (∼55 Ma), that were exposed to oxygen after core recovery. Surprisingly, P associated with iron oxyhydroxides (Fe-bound P) was a major P phase in these laminated sediments deposited under euxinic conditions. A significant fraction of total Fe was present as (poorly) crystalline ferric Fe. This fraction increased with increasing storage time of the investigated cores. In carbonate-poor samples, Fe-bound P accounted for up to 99% of total P and its abundance correlated with pyrite contents. In samples with higher CaCO3 contents (>5 wt% in the investigated samples), P was mostly present in authigenic Ca-P minerals, irrespective of pyrite contents. We conclude that the P fractionation in anoxic, carbonate-poor, sediments is strongly affected by pyrite oxidation that occurs when these sediments are exposed to oxygen. Pyrite oxidation produces sulfuric acid and iron oxyhydroxides. The abundance of poorly crystalline Fe oxyhydroxides provides further evidence that these were indeed formed through recent (post-recovery) oxidation rather than in situ tens of millions of years ago. The acid dissolves apatite and the released phosphate is subsequently bound in the freshly formed iron oxyhydroxides. Pyrite oxidation thus leads to a conversion of authigenic Ca-P to Fe-bound P. In more calcareous samples, CaCO3 can act as an effective buffer against acidic dissolution of Ca-P minerals. The results indicate that shielding of sediments from atmospheric oxygen is vital to preserve the in situ P fractionation and to enable a valid reconstruction of marine phosphorus cycling based on sediment records. 相似文献
19.
Sediment and porewater samples (1997–1999) were collected in the Northern Reach of the San Francisco Bay and Sacramento–San
Joaquin Delta for determinations of sedimentary selenium and its chemical speciation. Total sedimentary selenium increased
with depth, with approximately 50% of the sedimentary selenium as elemental selenium and 35% as organic selenide. Porewater
total dissolved selenium increased with depth in the estuary and Delta, and fluxes out of the sediments were calculated at
0.01 and 0.06 nmol cm−2 year−1 for the estuary and Delta, respectively. Present-day sediment–water exchange of dissolved selenium and internal transformations
cannot explain the observed increase in total sedimentary selenium with depth. However, mass balance calculations demonstrate
that the increase in total selenium with depth may be linked to higher dissolved selenium concentrations in the water column
in the 1980s, suggesting that the sediments could be used as historical recorders of selenium in the estuary. 相似文献
20.
Phosphorus fractions in sediment profiles and their potential contributions to eutrophication in Dianchi Lake 总被引：5，自引：0，他引：5
Dianchi Lake is a eutrophic lake in southwestern China. Sediment and the bottom water samples were taken from six sites in
the east, west, south, north and center of the lake, respectively, in December 2002. Total phosphorus (TP) concentrations
in sediments were high and reached a maximum value of 6.66 g/kg. There was a soluble reactive phosphorus (SRP) concentration
gradient at the sediment–water interface. In the present study, sediment P was divided into loosely adsorbed P (NH4Cl-P), redox-sensitive P (BD-P), metal oxides bound P (NaOH-P), calcium bound P (HCl-P), and organic P (Org-P). At three of
the six sites selected, the concentrations of different P forms in sediments followed the order: NaOH-P, Org-P>HCl-P>BD-P>NH4Cl-P in the profile, and in the southern lake the order was HCl-P>NaOH-P, Org-P>BD-P>NH4Cl-P in the top 15 cm layers of the sediments. The sediment profiles showed that different forms of P had an increasing trend
upward toward the sediment surface. There is a considerable potential for release from the sediment into the overlying water
and sediment P could be the dominant factor determining the trophic status of the lake if the external load is reduced.
An erratum to this article can be found at 相似文献