Correlation between plasmid DNA damage induced by PM10 and trace metals in inhalable particulate matters in Beijing air

Based on the study of Beijing PM₁₀ bioreactivity with the newly developed plasmid DNA assay method, and analysis for trace elements of PM₁₀, the cause of plasmid DNA damage by PM₁₀ was investigated. The study showed that plasmid DNA oxidative damages by PM₁₀ are of difference in different seasons at various areas. The concentrations of TM50 of PM₁₀ in whole samples respectively collected at urban and comparison sites during winter were 900 μg mL⁻¹ and 74 μg mL⁻¹, while those in their corresponding soluble fractions were 540 μg mL⁻¹ and 86 μg mL⁻¹. In contrast, TM50 contents of PM₁₀ from summer whole samples at urban areas and comparison sites were 116 μg mL⁻¹ and 210 μg mL⁻¹, whereas those in their soluble fractions were 180 μg mL⁻¹ and 306 μg mL⁻¹. The difference of bioreactivity of Beijing PM₁₀ resulted from the variation of trace elements. The oxidative damage of plasmid DNA caused by Pb, Zn, As in PM₁₀ (whole sample) was relatively strong. TM50 and Mn, V, Zn display stronger correlation in the soluble fraction. It implies that Zn could be the major trace element in Beijing PM₁₀ which contributes to oxidative damage to plasmid DNA.     

Field-aligned currents in the winter and summer hemispheres caused by IMF <Emphasis Type="Italic">By</Emphasis>

Structures controlled by the IMF By sign and season of the year have been detected based on the decomposition of field-aligned current maps constructed using magnetic field measurements on polar low-orbiting satellites. It has been indicated that field-aligned currents have identical structures, composed of the main polar circular current and the return current at the polar cap dayside boundary, at any By sign in the summer hemisphere. Two different types of structures are implemented under winter conditions depending on the By sign. For the northern winter, it is the polar circular current and the return current at the polar cap nightside boundary at By < 0; current sheets are strongly stretched along latitudes below 80° MLat, and only small part of the current is in the noon sector of the polar cap. For the summer winter, the corresponding structures are implemented at opposite By signs. The intensities of the field-aligned currents, originating as a result of the interhemispheric asymmetry and flowing along closed geomagnetic field lines near the polar cap boundary, have been estimated. The maximum of the interhemispheric current density is 0.25 μA m⁻² in the summer and 0.1 μA m⁻² in the winter; the total current is 5 × 10⁵ and 5 × 10⁴ A, respectively.     

Variation in transparent exopolymer particles in relation to biological and chemical factors in two contrasting lake districts

In inland waters, transparent exopolymer particles (TEP) can affect carbon export and sequestration in sediments with consequences for lake C budgets. We measured TEP concentration in 32 lakes from two contrasting lake districts covering wide ranges in biological and chemical characteristics. North temperate lakes, located in a wet region, have low to moderate ionic strength and low to high dissolved organic carbon with corresponding variation in color (light absorbance). Mediterranean lakes located in a semiarid region were characterized by high ionic strength and high concentrations of dissolved organic carbon but low color. TEP concentrations were large relative to the living portion of the particulate organic carbon pool in both Mediterranean (36%) and north temperate (33%) lakes. TEP concentrations ranged from 36 to 1,462 μg [as Gum Xanthan equivalents (GX eq)] L⁻¹ in north temperate lakes. In the Mediterranean lakes, concentrations were higher that previously reported for other systems and ranged from 66 to 9,038 μg GX eq L⁻¹. TEP concentration was positive and significantly related to chlorophyll a (chl a) in north temperate lakes and in the entire data set. Although a significant and positive relationship between TEP and chl a was also detected in the Mediterranean lakes, bacterial abundance was most strongly related to TEP. In contrast with the positive influence of phytoplankton and bacteria on TEP, there were weaker relationships between TEP and the chemical variables tested. We observed a significant and positive relationship between pH and TEP (for all lakes) but this relationship was indirectly driven by a co-variation of pH with phytoplankton biomass based on multiple regression analysis. For the Mediterranean lakes, the negative (but not significant) trends between TEP and both conductivity and divalent cations suggest thresholds above which TEP will likely be destabilized. Under these conditions, TEP may flocculate or disperse in the water column.     

Multiple sulfur isotope chemostratigraphy across the Permian–Triassic boundary at Chaotian,China: Implications for a shoaling model of toxic deep-waters

Previous studies on multiple sulfur isotopes (³²S, ³³S, and ³⁴S) in sedimentary pyrite at the end-Permian suggested a shoaling of anoxic/sulfidic deep-water contributing to the extinction. This scenario is based on an assumption that the sedimentary sulfur cycle was largely controlled by benthos activity, though a stratigraphic correlation between the sulfur records and ichnofabrics of the sediments at the end-Permian has not yet been examined. We report the multiple sulfur isotopic composition of pyrite in the Permian–Triassic boundary interval at Chaotian, South China. Our data can be generally explained by a mixing of sulfur in sulfide from two different sources: one produced via sulfate reduction in an open system with respect to sulfate and the other produced in a closed system. In particular, the former with the substantially low δ³⁴S (<−40 ‰) and high ∆³³S (up to +0.100 ‰) values was likely produced via water-mass sulfate reduction or via sulfate reduction in oxic sediments with common burrows. The frequent occurrence of small pyrite framboids (mostly <5 μm in diameter) in the Lopingian (Late Permian) Dalong Formation of deep-water facies supports the enhanced water-mass sulfate reduction in an anoxic deep-water mass. The negative ∆³³S values are observed only in the oxic limestones, and no substantial ∆³³S change is observed across the extinction horizon despite of the disappearance of bioturbation. Our results are apparently inconsistent with the previous shoaling model. We expand the model and infer that, when the deep-water was sulfidic and its shoaling rate was high, a substantial amount of hydrogen sulfide (H₂S) was supplied onto the shelf via the shoaling; that resulted in the positive ∆³³S value of the bulk sediments. The observed ∆³³S variation on a global scale suggests a substantial variation in H₂S concentration and/or in upwelling rate of shoaling deep-waters during the Permian–Triassic transition.     

Geochemistry of high-Mg andesites from the early Cretaceous Yixian Formation, western Liaoning: Implications for lower crustal delamination and Sr/Y variations

The Yixian Formation at Sihetun in western Liao- ning Province has attracted considerable attention over the last two decades due to discovery of a wide range of well-preserved ‘feathered’ dinosaurs and primitive bird fossils[1―4]. This formation is dominated by vol- canic rocks, with fossil-bearing lacustrine sedimentary rocks at the upper part of the section[4]. The sedimen- tary rocks contain thin layers of tuff. According to previous studies[4], the total thickness of the Yixian Form…     

Sediment resuspension in two adjacent shallow coastal lakes: controlling factors and consequences on phosphate dynamics

A combination of field measurements, modelling and laboratory experiments was used to evaluate the potential impact of sediment resuspension on phosphorus (P) dynamics. The study was carried out in two adjacent shallow coastal lakes (Lake Honda and Lake Nueva) which, due to their geographic proximity (only 200 m apart), are subject to equal meteorological forcing and represent ideal systems to study how morphometry and sediment properties relate to wind events. The focusing factors (a measure of the fluxes of sediment into the water column through resuspension) estimated by comparing settling fluxes measured in surface sediment traps with those measured in bottom traps, were significantly larger (approximately 34% larger) in Lake Honda (LH; 1.18) than in Lake Nueva (LN; 0.88). Our model estimates of resuspension fluxes (E) were also ca. 40% larger in LH than in LN, in agreement with the observed focusing factors. The larger resuspension fluxes encountered in LH, in comparison with LN, can mainly be explained by differences in lake morphometry. Still, they could arise from differences in grain size distribution or in benthic algae concentration encountered in the lake sediments. By means of adsorption experiments in the laboratory, we show that resuspension events will have different effects on P-dynamics in LH and LN. While the resuspended material from LH tends to adsorb phosphate (PO₄ ³⁻), removing it from the water column, in LN the resuspended sediments tend to increase the availability of PO₄ ³⁻ in solution. These differences arise from (1) higher concentrations of PO₄ ³⁻ in water in LH compared to LN; and (2) larger PO₄ ³⁻adsorption capacity of the LH sediments as a result of the more abundant iron oxyhydroxides and clay.     

Sulfur geochemistry of hydrothermal waters in Yellowstone National Park, Wyoming, USA. II. Formation and decomposition of thiosulfate and polythionate in Cinder Pool

Cinder Pool is an acid-sulfate-chloride boiling spring in Norris Geyser Basin, Yellowstone National Park. The pool is unique in that its surface is partially covered with mm-size, black, hollow sulfur spherules, while a layer of molten sulfur resides at the bottom of the pool (18 m depth). The sulfur speciation in the pool was determined on four different days over a period of two years. Samples were taken to evaluate changes with depth and to evaluate the importance of the sulfur spherules on sulfur redox chemistry. All analyses were conducted on site using a combination of ion chromatography and colorimetric techniques.Dissolved sulfide (H₂S), thiosulfate (S₂O₃²⁻), polythionates (S_xO₆²⁻), and sulfate were detected. The polythionate concentration was highly variable in time and space. The highest concentrations were found in surficial samples taken from among the sulfur spherules. With depth, the polythionate concentrations dropped off. The maximum observed polythionate concentration was 8 μM. Thiosulfate was rather uniformly distributed throughout the pool and concentrations ranged from 35 to 45 μM. Total dissolved sulfide concentrations varied with time, concentrations ranged from 16 to 48 μM. Sulfate was relatively constant, with concentrations ranging from 1150 to 1300 μM. The sulfur speciation of Cinder Pool is unique in that the thiosulfate and polythionate concentrations are significantly higher than for any other acid-sulfate spring yet sampled in Yellowstone National Park. Complementary laboratory experiments show that thiosulfate is the intermediate sulfoxyanion formed from sulfur hydrolysis under conditions similar to those found in Cinder Pool and that polythionates are formed via the oxidation of thiosulfate by dissolved oxygen. This last reaction is catalyzed by pyrite that occurs as a minor constituent in the sulfur spherules floating on the pool's surface. Polythionate decomposition proceeds via two pathways: (1) a reaction with H₂S, yielding thiosulfate and elemental sulfur; and (2) by disproportionation to sulfate and thiosulfate.This study demonstrates that the presence of a subaqueous molten sulfur pool and sulfur spherules in Cinder Pool is of importance in controlling the pathways of aqueous sulfur redox reactions. Some of the insights gained at Cinder Pool may be relevant to acid crater lakes where sulfur spherules are observed and variations in polythionate concentrations are used to monitor and predict volcanic activity.     

Preconditioning of an underflow during ice-breakup in a subarctic lake

The fate of inflows into lakes has been extensively studied during summer stratification but has seen relatively little focus during the weak winter stratification, with or without ice-cover. Field observations are presented of groundwater inflow into a shallow bay of a subarctic lake. Atmospheric forcing of the bay during the study period was extremely variable and coincided with spring ice-cover break-up. Two dominant wind regimes were identified; (1) weak wind-forcing (wind speed <5 m s⁻¹ or land-fast ice-cover), and (2) strong wind-forcing (wind speed >5 m s⁻¹ and open water). At a relatively constant temperature of ~3.3°C, the groundwater inflow was closer to the temperature of maximum density than the water in the main body of the lake, which during the observed winter stratification is ~1.2°C. During weak wind-forcing, the stratification within Silfra Bay approximated two-layers as this denser groundwater formed a negatively buoyant underflow. A calculated underflow entrainment rate of 2.8 × 10⁻³ agrees well with other underflow studies. During strong wind-forcing, the water column out to the mouth of the bay became weakly stratified as the underflow was entrained vertically by wind-stirring. Observed periods of mixing can be predicted to occur when turbulent kinetic energy (TKE) production by wind stirring integrated over the underflow hydraulic residence time in the bay exceeds the potential energy associated with the stratification. A decrease of ice cover, as observed in the studied subarctic lake over the last decade, will result in the underflow being more frequently exposed to the strong wind-forcing regime during winter, thereby altering the winter distribution of groundwater inflow within the lake.     

Seasonal dynamics of microbial sulfate reduction in temperate intertidal surface sediments: controls by temperature and organic matter

The role of microbial sulfate reduction on organic matter oxidation was studied quantitatively in temperate intertidal surface sediments of the German Wadden Sea (southern North Sea) on a seasonal base in the years 1998–2007. The sampling sites represent the range of sediments found in the back-barrier tidal area of Spiekeroog Island: sands, mixed and muddy flats. The correspondingly different contents in organic matter, metals, and porosities lead to significant differences in the activity of sulfate-reducing bacteria with volumetric sulfate reduction rates (SRR) in the top 15 cm of up to 1.4 μmol cm^?3 day^?1. Depth-integrated areal SRR ranged between 0.9 and 106 mmol m^?2 day^?1, with the highest values found in the mudflat sediments and lower rates measured in sands at the same time, demonstrating the impact of both temperature and organic matter load. According to a modeling approach for a 154-km² large tidal area, about 39, 122, and 285 tons of sulfate are reduced per day, during winter, spring/autumn, and summer, respectively. Hence, the importance of areal benthic organic matter mineralization by microbial sulfate reduction increases during spring/autumn and summer by factors of about 2 and 7, respectively, when compared to winter time. The combined results correspond to an estimated benthic organic carbon mineralization rate via sulfate reduction of 78 g C m^?2 year^?1.     

Sedimentary inputs and oxygen uptake by the sediment in Lake Geneva (Switzerland)

Sediment cores and sediment traps were collected twice a month in two 35 m deep stations of Lake Geneva (Switzerland). The organic input sedimenting to the bottom is equal to 157 g C m⁻²y⁻¹ in station 1, to 214 g C in station 2. In spite of this difference, the oxygen uptake by the sediment (OUS) is similar in both locations (46–47 g C m⁻²y⁻¹). The oxygen uptake by the matter sedimenting to the bottom (OUSM) is respectively 45 g C m⁻²y⁻¹ and 41 g C in stations 1 and 2. The equivalence between OUS and OUSM implies that most of the sedimented matter arriving to the bottom is directly oxidized at the sediment surface. In station 1, OUS is positively correlated to OUSM, and OUSM is positively correlated to chlorophyll-a concentrations in the water column (0–20 m) one week before sediment sampling. In location 2, OUS is positively correlated to the percentage of organic carbon and nitrogen in the sedimented matter, negatively to its C:N ratio. Increasing allochthonous inputs have a negative influence on benthic respiration. At both sites, OUS is not directly related to macrobenthic biomass or to temperature of bottom water.     

Phytoplankton abundance and contributions to suspended particulate matter in the Ohio,Upper Mississippi and Missouri Rivers

Main channel habitats of the Ohio, Missouri, and Upper Mississippi Rivers were surveyed during the summers of 2004, 2005 and 2006 using a probability-based sampling design to characterize inter-annual and inter-river variation in suspended chlorophyll a (CHLa) and related variables. Large (fivefold) differences in CHLa were observed with highest concentrations in the Upper Mississippi (32.3 ± 1.8 μg L⁻¹), intermediate values in the Missouri (19.7 ± 1.1 μg L⁻¹) and lowest concentrations in the Ohio (6.8 ± 0.5 μg L⁻¹). Inter-annual variation was small in comparison to inter-river differences suggesting that basin-specific factors exert greater control over river-wide CHLa than regional-scale processes influencing climate and discharge. The rivers were characterized by variable but generally low light conditions as indicated by depth-averaged underwater irradiance <4 E m⁻² day⁻¹ and high ratios of channel depth to euphotic depth (>3). Despite poor light conditions, regression analyses revealed that TP was the best single predictor of CHLa (R ² = 0.40), though models incorporating both light and TP performed better (R ² = 0.60). Light and nutrient conditions varied widely within rivers and were inversely related, suggesting that riverine phytoplankton may experience shifts in resource limitation during transport. Inferred grazing and sedimentation losses were large yet CHLa concentrations did not decline downriver indicating that growth and loss processes were closely coupled. The contribution by algae to suspended particulate organic matter in these rivers (mean = 41%) was similar to that of lakes (39%) but lower relative to reservoirs (61%).     

Cenozoic evolution of the sulfur cycle: Insight from oxygen isotopes in marine sulfate

We report new data on oxygen isotopes in marine sulfate (δ¹⁸O_SO4), measured in marine barite (BaSO₄), over the Cenozoic. The δ¹⁸O_SO4 varies by 6‰ over the Cenozoic, with major peaks 3, 15, 30 and 55 Ma. The δ¹⁸O_SO4 does not co-vary with the δ³⁴S_SO4, emphasizing that different processes control the oxygen and sulfur isotopic composition of sulfate. This indicates that temporal changes in the δ¹⁸O_SO4 over the Cenozoic must reflect changes in the isotopic fractionation associated with the sulfide reoxidation pathway. This suggests that variations in the aerial extent of different types of organic-rich sediments may have a significant impact on the biogeochemical sulfur cycle and emphasizes that the sulfur cycle is less sensitive to net organic carbon burial than to changes in the conditions of that organic carbon burial. The δ¹⁸O_SO4 also does not co-vary with the δ¹⁸O measured in benthic foraminifera, emphasizing that oxygen isotopes in water and sulfate remain out of equilibrium over the lifetime of sulfate in the ocean. A simple box model was used to explore dynamics of the marine sulfur cycle with respect to both oxygen and sulfur isotopes over the Cenozoic. We interpret variability in the δ¹⁸O_SO4 to reflect changes in the aerial distribution of conditions within organic-rich sediments, from periods with more localized, organic-rich sediments, to periods with more diffuse organic carbon burial. While these changes may not impact the net organic carbon burial, they will greatly affect the way that sulfur is processed within organic-rich sediments, impacting the sulfide reoxidation pathway and thus the δ¹⁸O_SO4. Our qualitative interpretation of the record suggests that sulfate concentrations were probably lower earlier in the Cenozoic.     

Organic carbon release by phytoplankton and bacterial reassimilation

The release of organic carbon by phytoplankton and its reassimilation by bacteria were studied in Lake Geneva during four daily kinetics, using¹⁴C techniques. Gentamycin was used to suppress bacterial activity. Size fractionation was used to measure¹⁴C fixation in 2 particulate fractions (≥1 μm and 0.2 to 1 μm) and in a third fraction: dissolved organic carbon. Measurements of bacterial biomass and¹⁴C glucose uptake as the H¹⁴CO ₃ ⁻ uptake by samples prefractionated before incubation showed that the whole algae were retained on 1 μm pore size Nuclepore filters, but bacteria were retained on 1 μm and 0.2 μm filters. Concentration of 20 μg.ml⁻¹ gentamycin resulted in incomplete bacterial inhibition while phytoplankton was affected. Phytoplankton released less of 20% of its photoassimilated carbon of which a large proportion was utilized by bacterioplankton.     

Element enrichment and U-series isotopic characteristics of the hydrothermal sulfides at Jade site in the Okinawa Trough

The geochemical and U-series isotopic characteristics of hydrothermal sulfide samples from the Jade site (127°04.5′E, 27°15′N, water depth 1300–1450 m) at Jade site in the Okinawa Trough were analyzed. In the hydrothermal sulfide samples bearing sulfate (samples HOK1 and HOK2), the LREEs are relatively enriched. All the hydrothermal sulfide samples except HOK1 belong to Zn-rich hydrothermal sulfide. In comparison with Zn-rich hydrothermal sulfides from other fields, the contents of Zn, Pb, Ag, Cd, Au and Hg are higher, the contents of Fe, Al, Cr, Co, Ni, Sr, Te, Cs, Ti and U lower, and the ²¹⁰Pb radioactivity ratios and ²¹⁰Pb/Pb ratios very low. In the hydrothermal sulfide mainly composed of sphalerite, the correlations between rare elements Hf and U, and Hf and Mn as well as that between dispersive elements Ga and Zn, are strongly positive; also the contents of Au and Ag are related to Fe-sulfide, because the low temperature promotes enrichment of Au and Ag. Meanwhile, the positive correlations between Fe and Bi and between Zn and Cd are not affected by the change of mineral assemblage. Based on the ²¹⁰Pb/Pb ratios of hydrothermal sulfide samples (3.99×10⁻⁵-5.42×10⁻⁵), their U isotopic composition (²³⁸U content 1.15–2.53 ppm, ²³⁸U activity 1.07–1.87 dpm/g, ²³⁴U activity 1.15–2.09 dpm/g and ²³⁴U/²³⁸U ratio 1.07–1.14) and their ²³²Th and ²³⁰Th contents are at base level, and the chronological age of hydrothermal sulfide at Jade site in the Okinawa Trough is between 200 and 2000 yr. Supported by the Pilot Project of Knowledge Innovation Project, Chinese Academy of Sciences (Grant No. KZCX2-YW-211), National Natural Science Foundation of China (Grant Nos. 40830849, 40176020), and Special Foundation for the Eleventh Five Plan of COMRA (Grant No. DYXM-115-02-1-03)     

Geochemical and Pb-Sr-Nd isotopic compositions of Indosinian granitoids from the Bikou block,northwest of the Yangtze plate:Constraints on petrogenesis,nature of deep crust and geodynamics

This paper reports geochemical and Pb-Sr-Nd isotopic compositions of the Indosinian Yangba (215 Ma),Nanyili (225 Ma) and Mopi granitoids from the Bikou block of the northwestern margin of the Yangtze plate. These granitoids are enriched in Al (Al2O3:14.56%―16.48%) and Sr (352 μg/g―1047 μg/g),and depleted in Y (<16 μg/g) and HREE (e.g. Yb<1.61 μg/g),resulting in high Sr/Y (36.3―150) and (La/Yb)N (7.8―36.3) ratios and strongly fractionationed REE patterns. The Indosinian granotoids show initial Sr isotopic ratios (ISr) from 0.70419 to 70752,εNd(t) values from-3.1 to -8.5,and initial Pb isotopic ratios 206Pb/204Pb=17.891-18.250,207Pb/204Pb=15.494-15.575,and 208Pb/204Pb=37.788-38.335. Their geochemi-cal signatures indicate that the granitoids are adakitic. However,they are distinct from some adakites,generated by partial melting of subducted oceanic slab and/or underplated basaltic lower crust,be-cause they have high K (K2O: 1.49%―3.84%) and evolved Nd isotopic compositions,with older Nd iso-topic model ages (TDM=1.06―1.83 Ga). Geochemical and Sr-Nd isotopic compositions suggest that the magmas of the Insoninian adakitic rocks in the Bikou block were derived from partial melting of thick-ened basaltic lower crust. Combined with regional analyses,a lithospheric delamination model after collision between the North China and South China plates can account for the Indosinian adakitic magma generation. On the other hand,based on the Pb-Sr-Nd isotopic probing to the magma sources of the adakitic rocks,it is suggested that there is an unexposed continent-type basement under the exposed Bikou Group volcanic rocks. This can constrain on the Bikou Group volcanic rocks not to be MORB-or OIB-type.     

Carbon input, production and turnover in the interstices of a Lake Tegel bank filtration site, Berlin, Germany

The sandy littoral zone of Lake Tegel (Berlin, Germany) was investigated during 2004–2006 down to sediment depths ≥26 cm to derive a scheme of seasonal carbon turnover under induced bank filtration conditions. Carbon turnover processes were quantified regarding external and internal sources of dissolved and particulate organic matter (DOM and POM), primary production, community respiration, redox potential as well as specific loads of soluble chemical compounds such as nitrogen, iron, manganese and DOC.Over the course of the year, infiltrating DOC decreased by about 13–20% within the upper 26 cm sediment of the infiltration stretch. Gradients of all observed soluble compounds that are highly cross-linked to biological activities were highest in the topmost centimetre. In this depth mass balances (output–input) were negative concerning NO₃-N (−1 mg dm⁻² d⁻¹, summer mean) and DOC (−2 mg dm⁻² d⁻¹, winter mean), respectively, while specific loads of cations such as manganese reached up to 0.2 mg dm⁻² d⁻¹ during summer. Carbon mineralization ranged between 3 and 7 mg C dm⁻² d⁻¹ and was nearly twice as high in summer as in winter. The turnover of the infiltrating DOC contributed maximally 25% in summer to 50% in winter to the entire organic carbon mineralization. Gross and net primary production differed up to a factor of >10, indicating very fast turnover reactions and the predominance of community respiration and mineralization, respectively. The POC in the upper sediment layer (10 cm) temporally varied around 1% sediment d.w.; benthic algae, organic seston input and autumnal leaf fall contributed similar percentages to the POC pool.