Black carbon and polycyclic aromatic hydrocarbons (PAHs) in surface sediments of China’s marginal seas

This study investigates the distribution of black carbon （BC） and its correlation with total polycyclic aromatic hydrocarbons （EPAH） in the surface sediments of China＇s marginal seas. BC content ranges from 〈0.10 to 2.45 mg/g dw （grams dry weight） in the sediments studied, and varied among the different coastal regions. The Bohai Bay sediments had the highest BC contents （average 2.18 mg/g dw）, which comprises a significant fraction （27%-41%） of the total organic carbon （TOC） preserved in the sediments. In comparison, BC in the surface sediments of the North Yellow Sea, Jiaozhou Bay, East China Sea and the South China Sea is less abundant and accounted for an average of 6%, 8%, 14% and 5%, respectively, of the sedimentary organic carbon pool. The concentration of EPAH in the surface sediments ranges from 41 to 3 667 ng/g dw and showed large spatial variations among the sampling sites of different costal regions. The Bohai Bay has the highest ZPAH values, ranging from 79 to 3 667 ng/g dw. This reflects the high anthropogenically contaminated nature of the sediments in the bay. BC is positively correlated to TOC but a strong correlation is not found between BC and ZPAH in the surface sediments studied, suggesting that BC and PAHs preserved in the sediments are derived from different sources and controlled by different biogeochemical processes. Our study suggests that the abundance of BC preserved in the sediments could represent a significant sink pool of carbon cycling in China＇s marginal seas.

Accumulation of petroleum hydrocarbons and heavy metals in clams (Ruditapes philippinarum) in Jiaozhou Bay,China

Accumulation and distributions of aliphatic and polyaromatic hydrocarbons (PAHs) and heavy metals were measured in tissues of the clam Ruditapes philippinarum collected from 5 sites in Jiaozhou Bay,Qingdao,China.The concentrations of total aliphatic hydrocarbon and PAHs ranged from 570 to 2 574 ng/gdw (gram dry weight) and from 276 to 939 ng/gdw,in the most and least polluted sites,respectively.The bio-accumulation of hydrocarbons and PAHs in the clams appeared to be selective.Aliphatic hydrocarbons were predominantly represented by short chain (<nC23) n-alkanes,suggesting that petroleum hydrocarbons were likely the major contamination source.The selective uptake of 3 and 4 ring PAHs,such as naphthalene,fluorene,phenanthrene,fluoranthene and pyrene,by the clams was probably related to the physiological and bio-kinetic processes that were energetically favorable for uptake of compounds with fewer rings.Accumulation of the metals Cd,Cu,Zn,Pb,Cr,Hg,and As in the clam tissues also showed high variability,ranging from 0.043 to 87 μg/gdw.Among the 7 detected metals,Zn,Cd,Cu,and As had a particularly high potential of accumulation in R.philippinarum.In general,a positive correlation was found between the tissue concentrations and sediment concentrations of hydrocarbons and of some metals.Our study suggests that moderate contamination with polyaromatic hydrocarbons,and low to moderate contamination with metals,currently exists for clam R.philippinarum in Jiaozhou Bay,in comparison with other regional studies.A long-term monitoring program is certainly needed for assessment of the potential ecological influence and toxicity of these contaminants of R.philippinarum in Jiaozhou Bay.

Organic carbon content and carbon isotope variations across the Permo-Triassic boundary in the Gartnerkofel-1borehole, Carnic Alps, Austria

The Gartnerkofel borehole is one of the most thoroughly studied and described Permo-Triassic sections in the world. Detailed bulk organic carbon isotope studies show a negative base shift from-24% to-28% in the Latest Permian which latter value persists into the Earliest Triassic after which it decreases slightly to-26%. Two strongly negative peaks of [-38% in the Latest Permian and a lesser peak of-31% in the Early Triassic are too negative to be due to a greater proportion of more negative organic matter and must be due to very negative methane effects. The overall change to more negative values across the Bulla/Tesero boundary fits the relative rise in sea level for this transition based on the facies changes. A positive shift in organic carbon isotope values at the Late Permian Event Horizon may be due to an increase in land-derived organic detritus at this level—a feature shown by allTethyan Permo-Triassic boundary sections though these other sections do not have the same values. Carbonate carbon isotope trends are similar in all sections dropping by2–3 units across the Permo-Triassic boundary. Gartnerkofel carbonate oxygen values are surprisingly, considering the ubiquitous dolomitization, compatible with values elsewhere and indicate reasonable tropical temperatures of 60 °C in the Latest Permian sabkhas to 20–40 °C in the overlying marine transition beds. Increased landderived input at the Late Permian Event Horizon may be due to offshore transport by tsunamis whose deposits have been recognized in India at this level.

Remote electric powering by germanium photovoltaic conversion of an Erbium-fiber laser beam

The commercially available 4000-Watt continuous-wave(CW)Erbium-doped-fiber laser,emitting at the 1567-nm wavelength where the atmosphere has high transmission,provides an opportunity for harvesting electric power at remote“off the grid”locations using a multi-module photovoltaic(PV)“receiver”panel.This paper proposes a 32-element monocrystalline thick-layer Germanium PV panel for efficient harvesting of a collimated 1.13-m-diam beam.The 0.78-m^(2) PV panel is constructed from commercial Ge wafers.For incident CW laser-beam power in the 4000 to 10,000 W range,our thermal,electrical,and infrared simulations predict 660 to 1510 Watts of electrical output at the panel temperatures of 350 to 423 K.

北美五大湖区晚更新世劳伦泰德冰盖演化年代学综述及石英光释光测年的初步尝试

北美五大湖区的安大略湖北岸Don Valley Brickyard、Scarborough Bluffs、Bowmanville Bluffs剖面共同构成了北美东北部最长也是最厚的陆地第四纪沉积记录,较完整地记录了晚更新世劳伦泰德冰盖(the Laurentide Ice Sheet)的演化.晚更新世劳伦泰德冰盖演化的重建有赖于这些经典剖面中重要沉积地层单元的准确年代学控制.传统的地层年代学主要是依靠少量14C年代,将主要的混杂堆积单元(diamicton)解释为气候变冷环境下的冰川扩张,并与指示全球冰量变化的深海氧同位素曲线一一比对建立起来的.这样建立起来的年代学存在很大的不确定性.20世纪80-90年代的少量热释光年代也不相吻合,最近的13个长石红外释光定年则只集中于Bowmanville Bluffs的一个分层,并未建立整个剖面的地层年代学,使这些经典沉积剖面的年代学一直没有得到系统的建立.应用石英光释光SAR-SGC法测试了Bow manville Bluffs剖面Glaciofluvial Sand单元的2个冰水沉积样品,年代结果分别为(41.6±3.8)ka、(48.1±4.4)ka,分析表明这一年代结果偏老,石英颗粒可能晒褪不完全.由于大测片无法识别晒褪不完全的颗粒,因此,测试更多的剖面序列的光释光年代并尝试采用粗颗粒小测片或单颗粒技术解决样品颗粒晒褪不完全的问题将是必要的.

Preservation of black carbon in the shelf sediments of the East China Sea

Concentrations and carbon isotopic(14C,13C) compositions of black carbon(BC) were measured for three sediment cores collected from the Changjiang River estuary and the shelf of the East China Sea. BC concentrations ranged from 0.02 to 0.14 mg/g(dry weight) ,and accounted for 5% to 26% of the sedimentary total organic carbon(TOC) pool. Among the three sediment cores collected at each site,sediment from the Changjiang River estuary had relatively high BC contents compared with the sedi-ments from the East China Sea shelf,suggesting that the Changjiang River discharge played an im-portant role in the delivery of BC to the coastal region. Radiocarbon measurements indicate that the ages of BC are in the range of 6910 to 12250 years old B.P.(before present) ,that is in general,3700 to 9000 years older than the 14C ages of TOC in the sediments. These variable radiocarbon ages suggest that the BC preserved in the sediments was derived from the products of both biomass fire and fossil fuel combustion,as well as from ancient rock weathering. Based on an isotopic mass balance model,we calculated that fossil fuel combustion contributed most(60%―80%) of the BC preserved in these sediments and varied with depth and locations. The deposition and burial of this "slow-cycling" BC in the sediments of the East China Sea shelf represent a significant pool of carbon sink and could greatly influence carbon cycling in the region.

热带地区的森林采伐:协调有关印度森林采伐量估算上的分歧

热带森林的大面积采伐将会导致深远的全球后果。如果森林采伐继续保持不变,我们很可能要面临气候模式和生物多样性分布的变化。农业和经济的可持续性很大程度上取决于对生存环境退化范围的了解和包容这种退化的策略发展。森林采伐的两种严重后果是温室气体的排放和生物多样性的丧失。热带森林的采伐和退化可能会引起二氧化碳等温室气体的升高。准确地估算森林的采伐和退化是清查和改善有关二氧化碳和其它温室气体排放的必要基础。而且。

Electric-field-induced quasi-phase-matched three-wave mixing in silicon-based superlattice-on-insulator integrated circuits

We present a theoretical investigation,based on the tight-binding Hamiltonian,of efficient electric-field-induced three-waves mixing(EFIM)in an undoped lattice-matched short-period superlattice(SL)that integrates quasi-phase-matched(QPM)SL straight waveguides and SL racetrack resonators on an opto-electronic chip.Periodically reversed DC voltage is applied to electrode segments on each side of the strip waveguide.The spectra ofχ_(xxxx)^((3))and of the linear suscepti-bility have been simulated as a function of the number of the atomic monolayers for“non-relaxed”heterointerfaces,and by considering all the transitions between valence and conduction bands.The large ob-tained values ofχ_(xxxx)^((3))make the(ZnS)3/(Si2)3 short-period SL a good candidate for realizing large effective second-order nonlinearity,en-abling future high-performance of the SLOI PICs and OEICs in the 1000-nm and 2000-nm wavelengths ranges.We have made detailed calculations of the efficiency of second-harmonic generation and of the performances of the optical parametric oscillator(OPO).The re-sults indicate that the(ZnS)N/(Si2)M QPM is competitive with present PPLN technologies and is practical for classical and quantum appli-cations.

Design of low-energy on-chip electro-optical 1 × M wavelength-selective switches

A theoretical design is presented for a 1 × M wavelength-selective switch(WSS) that routes any one of N incoming wavelength signals to any one of M output ports. This planar on-chip device comprises of a 1 × N demultiplexer, a group of N switching "trees" actuated by electro-optical or thermo-optical means, and an M-fold set of N × 1multiplexers. Trees utilize 1 × 2 switches. The WSS insertion loss is proportional to [log_2(M+N +1)]. Along with cross talk from trees, cross talk is present at each cross-illuminated waveguide intersection within the WSS, and there are at most N-1 such crossings per path. These loss and cross talk properties will likely place a practical limit of N=M=16 upon the WSS size. By constraining the 1 × 2 switching energy to^1 f J∕bit, we find that resonant, narrowband 1 × 2 switches are required. The 1 × 2 devices proposed here are nanobeam Mach–Zehnders and asymmetric contra-directional couplers with grating assistance.

Classical and quantum photonic sources based upon a nonlinear GaP/Si-superlattice micro-ring resonator

We present a theoretical investigation,based on the tight-binding Hamiltonian,of efficient second-and third-order nonlinear optical processes in the lattice-matched undoped(GaP)N/(Si 2)M short-period superlattice that is waveguide-integrated in a microring resonator on an opto-electronic chip.The nonlinear superlattice structures are sit-uated on the optically pumped input area of a heterogeneous“XOI”chip based on silicon.The spectra ofχ(2)zzz(2ω,ω,ω),χ(2)xzx(2ω,ω,ω),χ(3)xxxx(3ω,ω,ω,ω)and the Kerr refractive index(n 2),have been simu-lated as a function of the number of the atomic monolayers for“non-relaxed”heterointerfaces;These nonlinearities are induced by transi-tions between valence and conduction bands.The large obtained val-ues make the(GaP)N/(Si 2)M short-period superlattice a good can-didate for future high-performance XOI photonic integrated chips that may include Si 3 N 4 or SiC or AlGaAs or Si.Near or at the 810-nm and 1550-nm wavelengths,we have made detailed calculations of the efficiency of second-and third-harmonic generation as well as the performances of entangled photon-pair quantum sources that are based upon spontaneous parametric down conversion and sponta-neous four-wave mixing.The results indicate that the(GaP)N/(Si 2)M short-period superlattice is competitive with present technologies and is practical for classical and quantum applications.

Mid-infrared 2×2 electro-optical switching by silicon and germanium three-waveguide and four-waveguide directional couplers using free-carrier injection

New designs are proposed for 2×2 electro-optical switching in the 1.3–12μm wavelength range.Directional couplers are analyzed using a two-dimensional effective-index approximation.It is shown that three or four side-coupled Si or Ge channel waveguides can provide complete crossbar broad-spectrum switching when the central waveguides are injected with electrons and holes to modify the waveguides’core index by an amountΔn+iΔk.The four-waveguide device is found to have a required active length L that is 50%shorter than L for the three-waveguide switch.A rule ofΔβL>28 for 3w andΔβL>14 for 4w is deduced to promise insertion loss<1.5 dB and crosstalk<−15 dB at the bar state.At an injection ofΔNe=ΔNh=5×10^(17)cm^(−3),the predicted L decreased from∼2 to∼0.5 mm asλincreased from 1.32 to 12μm.Because of Ge’s largeΔk,the Ge bar loss is high in 4w but is acceptable in 3w.