Polycyclic aromatic hydrocarbons in dated sediments from Green Bay and Lake Michigan

Sediment cores from two locations in Green Bay and two in lake Michigan were analyzed for 12 polycyclic aromatic hydrocarbons (PAHs), loss-on-ignition (LOI),²¹⁰Pb,¹³⁷Cs, and⁷Be to study differences in deposition patterns between the freshwater estuary Green Bay, with several local sources, and the open Lake Michigan, dominated by atmospheric inputs. We found that the remote sites receive relatively less high-molecular weight PAHs such as ideno(1,2,3-cd)pyrene and dibenz(ah)anthracene and are more depleted in anthracene and pyrene. This may be related to a low Henry’s law constant for the high molecular compounds and to selective photo-oxidation of anthracene and pyrene during transport. While sedimentation rates are higher in Green Bay than in the open lake, the PAH levels are generally comparable (0.3–8.5 μg g^?1) in the two areas. However, the highest PAH levels are found in a core from Green Bay (GB88G). The two Green Bay cores have total PAH concentration maxima in 1985, which appear to be related to the combustion of petroleum. Also, one Green Bay core (GB88G) and the two from Lake Michigan exhibit PAH maxima in the early 1950s in agreement with observations from other study areas. There is a significant correlation between total PAH and LOI, and thus total organic carbon, for the Green Bay cores, but little or no such correlation for the Lake Michigan cores. This may indicate that PAHs in Green Bay are effectively scavenged by settling detritus.     

Fatty acids and hydrocarbons in surficial sediments of Lake Huron

Fatty acid and hydrocarbon distributions in surficial sediments from ten locations in southern Lake Huron indicate both aquatic and terrigenous recent biological sources of these geolipid materials. Normal alkanoic acids appear to be derived primarily from aquatic sources whereas normal alkanes are from multiple origins. Geolipid distributions are determined by the nature of the biogenic source and are modified during transport and deposition. Sediments receiving urban runoff in Saginaw Bay contain large amounts of non-biogenic hydrocarbons of a petroleum or industrial nature.     

Bacterial and algal hydrocarbons in sediments from a saline Antarctic lake, Ace Lake

Capillary gas chromatography-mass spectrometry (C-GC-MS) and Iatroscan thin layer chromatography-flame ionisation detection (TLC-FID) were used to study hydrocarbon distributions in a sediment core from Ace Lake, a saline, meromictic lake in the Vestfold Hills of Antarctica. Hydrocarbons were abundant in most core sections (up to 125/μg/g dry wt), particularly in near-surface samples, and the distributions were very complex. Major constituents were identified as phytane, 2,6,10,15,19-pentamethyleicosane, tetrahydrosqualene, a mixture of phytenes, cholesta-3,5-diene and fern-7-ene. Smaller amounts of sterenes and hopenes were also present. The predominance of the first 3 acyclic isoprenoids in sediments buried less than 30 cm is consistent with high populations of methanogenic bacteria known to be present.Phytenes were abundant in all core sections, and there was no relationship between their abundance and that of phytane which suggests that they were not derived from methanogenic bacteria. Phytadienes were minor constituents at all depths studied. An unusual feature of some distributions was the high concentrations of fern-7-ene which was the major hydrocarbon in the 20–25 cm core section. This alkene was only abundant in sediments which contained high concentrations of methanogen markers suggesting that it may also be indicative of anoxic depositional environments. A possible source might be from purple non-sulphur bacteria. High concentrations of straight-chain C₂₉ and C₃₄ alkenes were also found in these sediments but their origin has not been determined. Major changes in the hydrocarbon distributions with depth indicate that the depositional environment in the lake has altered dramatically since the lake was formed less than 8000 years ago. The present condition of permanent anoxic bottom waters probably developed only in the last 1000 years.     

太湖宜溧河水系沉积物中多环芳烃来源解析

利用索氏提取技术和GC／MS测定，分析了太湖定溧河水系中13个样点沉积物中的多环芳烃（PAHs)，并利用芳香类不可分辨鼓包峰的检出、多环芳烃组分协相关因子检验及PAHs特征化合物指数，分析了太湖流域宜溧河水系中各地区的PAHs污染来源差异，并结合定溧河所在地区工业布局和环境特征得到了验证。溧阳附近PAHs主要来自于油类污染和染料工业的影响；宜兴市附近PAHs来源与溧阳不同，主要与现代煤烟型污染有关。从水第的干支流对比中发现，主干河道中沉积物PAHs污染来源比支流复杂的多，存在多种污染源交叉作用的情况。     

湖北梁子湖沉积物正构烷烃与多环芳烃对环境变迁的记录

对梁子湖沉积柱91～345 cm段中正构烷烃和17种多环芳烃含量进行了分析,发现在整个沉积柱中,长碳链正构烷烃的比例和17种多环芳烃含量的变化具有良好的一致性,二者都是从181～194 em(14C定年显示其对应的沉积年代为我国历史上的春秋战国时期)开始突然增高,指示了陆源有机质输入的剧增.认为这种变化正是春秋战同时期我国自然环境条件的改变以及由此引起的人类活动的增加在湖泊沉积记录中的反映.     

Baccharane (18,19-secolupane): A rare triterpenoid skeleton widespread in Triassic sediments and petroleum from the Adriatic Basin

Baccharane (18,19-secolupane) 1, a triterpenoid skeleton seldom encountered in living organisms, has been characterized together with 17βH-des-E-lupane 2, one of its minor degradation products, in Italian Triassic sediment and crude oil samples from the Adriatic Basin by synthesis of standards.Reports of baccharane-derived triterpenoids in the field of natural products are scant and up to now restricted to terrestrial plants (angiosperms and ferns). In this regard, sedimentary baccharane derivatives may indicate a continental contribution (ferns?) to fossil organic matter; but they may also represent a contribution of as yet undetermined marine microorganisms, as has been proposed for dammarenes and dammaranes. Alternatively, they could be the bio/geochemical transformation products of biosynthetically closely related precursors such as lupane- or dammarane-type triterpenoids.The apparently restricted occurrence of baccharane derivatives in geological samples (up to now detected only in Triassic sediments of the Adriatic Basin) confers upon these compounds great value as correlation parameters and possibly as source indicators.     

Aliphatic hydrocarbons in coastal sediments of the Northern Cyprus (Eastern Mediterranean)

The sources and spatial distributions of aliphatic hydrocarbon concentrations were investigated in surficial sediments of the Northern Cyprus (Gemi Konagi, Girne and Gazi Magusa Areas). Aliphatic hydrocarbon levels were determined with a gas chromatography–mass spectrometer. Total aliphatic hydrocarbon (n-alkanes, Σ25; isoprenoids, Σ2) concentrations in the sediments were found in the range of 1107–6360 ng/g. Results indicated that the sediments were mainly dominated by odd numbered n-alkanes (n-C10–n-C34), maximizing at n-C17, n-C29 and n-C31. Statistical analyses and diagnostic ratios have been used to determine the possible sources and origins of aliphatic hydrocarbons. Aliphatic hydrocarbons were showed biogenic character at all sampling areas and were found mainly originated from terrestrial, marine and both terrestrial-marine plants at Gemi Konagi, Gazi Magusa and Girne, respectively.     

Oxygen isotope composition of diatoms from sediments of Lake Kotokel (Buryatia)

This is a summary of new oxygen isotope record of diatoms from Lake Kotokel sediments, with implications for responses of the lake system and its environment to global change over the past 46 kyr. Fossil diatoms in all samples are free from visible contamination signatures and contain no more than 2.5% Al₂O3, which ensures reliable reconstructions. The 5¹⁸O values in diatoms vary between + 23.7 and + 31.2%c over the record. The results present mainly diatom assemblages of summer blooming periods, except for the time span between 36 and 32 kyr, when the isotopic signal records mainly a shift from summer to spring blooming conditions. Possible water temperature changes only partly explain the changes in the isotopic record. The observed isotopic patterns are produced mainly by isotope changes in lake water in response to variations in air temperature, hydrology, and atmospheric circulation in the region. During Marine Isotope Stage (MIS) 2 (Last Glacial maximum), high 5¹⁸Od_iatom resulted from rapid evaporation and low fluvial inputs. The high 5¹⁸Od_iatom values of about + 29 to + 30%c during the first half of MIS 1 (Holocene interglacial) suggest an increased share of summer rainfalls associated with southern/southeastern air transport. The 5¹⁸Odi_atom decrease to + 24%c during the second half of MIS 1 is due to the overall hemispheric cooling and increased moisture supply to the area by the Atlantic air masses. The record of Lake Kotokel sediments provides an example of complex interplay among several climatic/environmental controls of 5¹⁸O_diatom during the Late Pleistocene and the Holocene.     

Near east paleomagnetic secular variation recorded in sediments from the Sea of Galilee (Lake Kinneret)

Paleomagnetic records of declination and inclination from sediments recovered from the bed of Lake Kinneret (32.4°N, 35.7°E) have been dated by radiocarbon techniques. The sediments span the last 5000 yr. The changes in inclination down the sediment cores are more pronounced than the declination fluctuations and are repeatable between the three coring sites, which are several kilometers apart. Magnetic susceptibility logs display 13 maxima in the 5-m-long sequences, with a pronounced susceptibility minimum about 1000 yr B.P. Many of the susceptibility maxima and minima can be easily correlated between coring sites and are shown to be dominantly related to changes in sediment carbonate content. The natural remanent magnetization intensity follows a similar pattern to that of susceptibility, and the natural remanence of the Kinneret sediments is presumed to reside in detrital magnetite grains carried into the lake by the river Jordan from the basalt-rich bedrock of the rift floor and the Golan Heights. The ¹⁴C chronology is strongly supported by a pollen study in which pronounced changes in the proportion of olive pollen were interpreted as being due to extensive cultivation of olives around Galilee in the Hellenistic and Byzantine periods. The Kinneret paleosecular variation records, if accurately dated, point to a complex spatial pattern of Holocene secular variation with significant variations over distances as small as 1000–2000 km.     

Concentration and composition of hydrocarbons in bottom sediments from the Sakhalin shelf

Aliphatic and polycyclic aromatic hydrocarbons were examined in the surface layer of bottom sediments from the eastern part of the Sakhalin shelf (the materials were sampled in the summer of 2002). The concentrations of hydrocarbons were determined to have changed since the beginning of the development of oil fields (compared with earlier years). According to the distribution of markers in the hydrocarbon compositions, the bottom sediments are dominated by allochthonous (terrigenous) hydrocarbons, which are the most stable compounds. The presence of transformed anthropogenic oil alkanes, which have never been found before, may be indicative of the increasing pollution of the region.     

Geochemical characteristics of methane from sediments of the underwater high Posolskaya Bank (Lake Baikal)

The component and carbon isotope compositions were studied in the hydrocabon gases from sediments of the underwater high Posolskaya Bank (Lake Baikal). It was established that sediments of this Baikal area contain methane of microbial (C₁/C₂ >16000; δ¹³C 70 ± 3‰) and thermocatalytic (C₁/C₂ <100; δ¹³C–46 ± 3‰) origin. Some samples represent a gas mixture of thermocatalytic and microbial origin. This gas is characterized by δ¹³C of methane varying from–60 to–70‰ and contains a significant amount of ethane. The main homolog of methane in the thermocatalytic and mixed gas is ethane. Owing to biodegradation, propane and butanes are present in trace amounts.     

Magnetic properties of bottom sediments from Meromectic Shira Lake (Siberia,Russia)

Magnetic properties were studied in bottom sediments of saline meromictic Shira Lake by the methods of static magnetometry and resonance Mössbauer spectroscopy for the first time. All layers of bottom sediments contain nanosized single-domain magnetite particles produced by magnetotactic bacteria. The concentration of magnetite in bottom sediments decreased with depth, reaching a local minimum in the layer corresponding to the minimal level of the lake observed in 1910–1930. It is demonstrated that biogenic magnetite may indicate climate-related changes in the level of Shira Lake, in addition to the other biological and geochemical characteristics.     

An evaluation of trace metal distribution and environmental risk in sediments from the Lake Kalimanci (FYR Macedonia)

Pollution from mining activities is a significant problem in several parts of the Republic of Macedonia. A geochemical study of the surficial sediments of Lake Kalimanci in the eastern part of the Republic of Macedonia was carried out to determine their elemental compositions and to evaluate the pollution status of lake sediments by employing an enrichment factor (EF). The major and trace element contamination in surficial lake sediments was studied to assess the effects of metalliferous mining activities. The mean concentrations of major elements (wt%) Si 23.5, Al 7.9, Fe 6.6, Mg 1.3, Ca 3.8, Na 1.1, K 2.3, Ti 0.4, P 0.2, Mn 0.6 and trace elements ranged within Mo 1.0–4.6 mg kg^?1, Cu 144.4–1,162 mg kg^?1, Pb 1,874–16,300 mg kg^?1, Zn 2,944–20,900 mg kg^?1, Ni 21.7–79.3 mg kg^?1, Cd 16.5–136 mg kg^?1, Sb 0.6–3.6 mg kg^?1, Bi 3.0–24,3 mg kg^?1 and Ag 1.4–17.3 mg kg^?1. The EF ranged within 0.12–590.3. Among which, Cd, Pb, Zn and As have extremely severe enrichment. The data indicate that trace elements had extremely high concentrations in Lake Kalimanci surficial sediments owing to the anthropogenic addition of contaminants.     

Historical record of polycyclic aromatic hydrocarbons (PAH) and heavy metals in floodplain sediments from the Rhine River (Hessisches Ried, Germany)

The depth-related content of polycyclic aromatic hydrocarbons (PAH) and heavy metals was determined for two soil profiles (i.e. one Fluvisol and one Gleyic Cambisol) which developed in sediments from floodplains located at an old meander of the Rhine river. The meander had been cut off from the main river in 1829. The separation of the meander from the main river caused a change in sediment deposition (i.e. from sand to silt) which is clearly visible in the soil-profiles. Since that time, approximately 100 cm of sediments have accumulated due to temporary flooding of the area. Each soil profile was separated into 18 samples. The samples were analysed for their content of PAH after solvent extraction. Additionally, several trace elements (Co, Ni, Cd, Pb, Zn, Cr and Cu) were determined in the same sample set, and depth-related concentration profiles for both PAH and trace elements were developed. The distribution patterns of PAH with more than 3 condensed rings did not provide any evidence for PAH biodegradation or vertical transport after deposition of the sediments. Thus, in the case of PAH, the historical record can be derived not only from subhydric sediments but also from floodplain sediments. It was not possible to distinguish between atmospheric and fluvial input of PAH into the sediments from the observed distribution patterns due to the same origin of PAH from pyrolytic processes. A source determination of the PAH was not possible except for perylene, for which biogenic formation can be assumed. A comparison of the results shows that the depth-related PAH and trace element concentrations display similar trends over most of the total profiles. In the uppermost section of the profiles, the concentration of most trace elements declines whereas the PAH concentration remains high. This indicates the presence of different sources for PAH and trace elements in the last decades.