Comparisons between marine productivity and terrestrial input records in the Gulf of California over the last 28 ka

We study the marine and terrestrial contributions in the Gulf of California (GC) to understand the relationship between continental climate and oceanographic variability over the last 28 ka. In Core AII125-8-JPC-20, we examine aeolian and riverine inputs as nutrients for biological productivity. We use biogenic silica (%opal), total organic carbon (%TOC) and calcium carbonate (%CaCO₃) as proxies for primary productivity, and lithic fraction distributions as proxies for terrigenous transport. At the core site, biogenic and lithic components are in phase at millennial-scale in response to regional climate conditions. During the Late Pleistocene, the GC shelf area was above sea level and the western margin showed transient episodes of increased fluvial inputs. Episodic increases in %opal and reduced %TOC suggest upwelling events but ineffective C-export to the sediment. During stadial events (Heinrich 2, Heinrich 1, Younger Dryas), regional declines in %opal, but increases in %CaCO₃ and TOC, suggest efficient C-export by carbonate organisms. During most of the Holocene, dust inputs are higher. Episodic increases in %TOC suggest higher C-accumulation, although this is not controlled by siliceous or calcareous organisms. In the GC, besides upwelling and current advection, nutrient inputs driven by terrestrial climate have an impact on the biological C-pump. © 2020 John Wiley & Sons, Ltd.     

人类活动对太湖水环境影响的稳定氮同位素示踪

人类活动对湖泊环境变化的影响是目前全球变化研究的热点之一.识别水体中人为氮源的贡献对于研究人类活动对湖泊环境变化的影响十分重要.稳定氮同位素组成(δ15N)是水环境中人为氮源的有效示踪剂.太湖是我国典型的大型浅水富营养湖泊,位于人口稠密、经济发达的长江三角洲地区,是研究人类活动对水环境影响的理想对象.太湖水体δ15N值的空间分异规律大致反映了不同湖区人类活动影响水环境的方式,上游宜兴小流域及河口主要受农业活动影响,胥口湾和东太湖则主要是水产养殖的贡献,梅梁湾受城市生活污水影响较大.而且水体δ15N值的水平反映了人类活动的影响从南部湖区到北部湖区逐渐加强的趋势,表现为南部河口—东太湖—梅梁湾不同水体从草型水体到藻型水体δ15N值增加的趋势.另外,夏季(6月)太湖水体δ15N值的变化响应于初级生产力的变化,体现了生物作用的影响.在蓝藻水华暴发时期,利用水体δ15N值识别人为氮源的结果可能会受到生物过程的干扰.     

长联大跨摩擦摆支座隔震连续梁桥多维地震反应分析

结合长联大跨连续梁桥的特点,以1座(65+123+156+123+10×90+55)m长联大跨摩擦摆支座隔震连续梁桥为背景,建立了全桥三维有限元模型,运用非线性时程分析法,分析了地震动输入模式、地震动强度、摩擦摆支座参数对该桥内力、位移和能量响应的影响。研究结果表明:(1)长联大跨连续梁桥布置摩擦摆支座,可有效延滞固定墩顶有效主梁质量效应,实现全桥协同抗震。大部分地震能量可通过支座滞回耗能散耗,大幅降低了该桥固定墩地震能量耗散需求。(2)长联大跨连续梁桥减隔震设计中,建议采用水平单向+竖向地震组合进行内力设计,采用三向地震组合进行位移设计。(3)强震作用下,支座摩擦因数取0.029~0.034时该桥隔震性能最优。     

Increasing eutrophication in the coastal seas of China from 1970 to 2050

We analyzed the potential for eutrophication in major seas around China: the Bohai Gulf, Yellow Sea and South China Sea. We model the riverine inputs of nitrogen (N), phosphorus (P) and silica (Si) to coastal seas from 1970 to 2050. Between 1970 and 2000 dissolved N and P inputs to the three seas increased by a factor of 2–5. In contrast, inputs of particulate N and P and dissolved Si, decreased due to damming of rivers. Between 2000 and 2050, the total N and P inputs increase further by 30–200%. Sewage is the dominant source of dissolved N and P in the Bohai Gulf, while agriculture is the primary source in the other seas. In the future, the ratios of Si to N and P decrease, which increases the risk of harmful algal blooms. Sewage treatment may reduce this risk in the Bohai Gulf, and agricultural management in the other seas.     

Molecular biomarker record of paleooceanographic environment in the East China Sea during the last 35000 years

By reference of the δ¹⁸O and δ¹³C isotopic compositions of G.sacculifer and accelerator mass spectrometry (AMS)¹⁴C dates, the U _K ³⁷ , ∑C _– ²¹ /∑C _+- ²² and Pr/Pn in core DGKS9603 have been used to characterize the changes of paleooceanographic environment occurring in the East China Sea (ECS) during the last 35000 years. The stratigraphic records of these proxies have shown that during the last 35 ka the Okinawa Trough has gone through 7 stronger cold-climate events (C₁–C₇) and 9 terrigenous matter-decreasing events (e₂–e₉), of which, the C₁ corresponds to the cold episode occurring in the middle late Holocene, C₂–C₄ and C₇ correspond to the H₁–H₄ events, respectively. e₁ and e₃–e₈ correspond to the decrease of sea surface temperature (SST), respectively. The terrigenous inputs increased when Heinrich events occurred. Climate colding resulted in the decrease of terrigenous matter transported by rivers, and the increase of that transported by winter monsoon. Heinrich events are closely related to East Asia monsoon. During the Last Glacial Maximum (LGM, 15.5–25.8 Cal ka BP), reduction environment fluctuated strongly, bringing forth three stronger reduction events (R₁–R₃) and one weaker reduction event (O), of which, R₁–R₃ correspond to the decrease of SST and increase of terrigenous nutrient and O corresponds to the decrease of terrigenous nutrient. The fluctuation of reduction condition must be related to the change of sea surface productivity.     

The significance of atmospheric nutrient inputs and canopy interception of precipitation during ecosystem development in piñon–juniper woodlands of the southwestern USA

In arid ecosystems, widely spaced vegetation and prolonged dry periods may enhance canopy capture of nutrients from dry deposition. Additionally, differences in precipitation type, plant canopy architecture, and soil nutrient limitation could affect canopy exchange of atmospherically derived nutrients. We collected bulk precipitation and throughfall underneath piñon pine (Pinus edulis) and one-seed juniper (Juniperus monosperma) along a substrate age gradient to determine if canopy interception or throughfall chemistry differed among tree species, season, or substrate age. The Substrate Age Gradient of Arizona consists of four sites with substrate ages ranging from 1 ky to 3000 ky-old, which exhibit classic variations in soil nitrogen (N) and phosphorus (P) availability with substrate age. Greater nutrient inputs below canopies than in intercanopy areas suggest throughfall contributes to the “islands of fertility” effect. Canopy interception of precipitation did not differ between tree species, but was greater in the summer/fall than winter/spring. We found that net canopy retention of atmospherically derived N was generally greater when N availability in the soil was low, but retention also occurred when N availability was relatively high. Taken together, our results were inconclusive in determining whether the degree of soil nutrient limitation alters canopy exchange of plant growth-limiting nutrients.     

Responses of Two New Hampshire (USA) Lakes to Human Impacts in Recent Centuries

This study contrasts the effects of human disturbances on two very different lake/catchment systems: Hatch Pond and Beaver Lake, New Hampshire. Hatch is in a steep mountain catchment remote from urban/industrial centers, and is a small, relatively deep, primarily seepage lake with moderate flushing rate. The catchment has been continuously forested, but disturbed by partial loggings and a forest fire. Beaver’s more extensive and gently sloping catchment is much closer to urban/industrial centers, and has been agricultural and recently suburban. Beaver is a larger but shallower drainage lake with much more rapid flushing than Hatch. We compared the sedimentary records and inferred limnological responses to catchment land uses and air pollution inputs of these mesotrophic lakes, and interpreted differing responses as a function of basic differences between the lakes and their catchments. Some chemical and biological variables in the sediment of both lakes respond sensitively to the first disturbances of the catchments by Euro-American settlers. Diatom-inferred Cl at both lakes indicates a modest increase of salinity at this time. Hatch sediment contains a record of soil erosion starting 1810 with first logging and fire. For ~125 years, erosion was largely of upper eluviated soil, but by 1935 it reached deeper into the illuviated (enriched) horizon. Maximal lake trophic state based on diatom-inferred limnological variables occurred in the mid-1900’s period of maximum sedimentation of illuviated soil. The sediment record since 1964 reflects forest maturation, and soil stabilization and acidification, but not lake acidification. At Beaver, the limnological effects of forest clearance and agriculture starting ~1700 were relatively mild due to gentleness of slopes and soil characteristics favoring stability. A near doubling of earth elements, and major increases in trace metal pollutants and coal combustion particles (CCP) occurred in sediment dating around 1900. Landscape analysis as well as historical and sedimentary records preclude the catchment as the major source of these increases. The most likely source is atmospheric fallout of CCP with its metal load. Despite controls on CCP and other emissions starting 1960, concentrations of earth elements and trace metals in Beaver sediment remain high due to soil mobilization by residential development of the catchment. The trophic state of Beaver Lake has increased, but the relative increase has been smaller than at Hatch, despite more intensive land uses and greater aerial inputs at Beaver. We propose that this lesser eutrophication is due to rapid flushing of Beaver Lake with stream water from relatively undeveloped parts of the extensive catchment, and lower sensitivity to nutrient inputs of this naturally more eutrophic lake. A major shift from unicellular to colonial chrysophytes at Hatch starts in the late-1800’s, and at Beaver in the early 1900’s. Colonial taxa in lesser quantities appear at the time of first settlement of the Beaver catchment. At both lakes the shifts are correlated with increasing metal fluxes from the opening of catchment biogeochemical cycles, as with the aforementioned erosional sequence at Hatch. But at Hatch aerial inputs of trace metals, and at Beaver aerial inputs major and trace metals associated with CCP are also correlated with the major chrysophyte shift. It appears that the chrysophytes have responded to stressors associated with both catchment disturbance and regional atmospheric inputs.     

4福建省电子信息产业R＆D投入与产出效益分析

利用福建省电子信息产业大中型以上规模企业2000-2008年的R＆D活动相关数据,对福建省电子信息产业R＆D活动投入产出相关指标及效益进行分析．结果表明：福建省电子信息产业R＆D经费和R＆D人员投入对产出均有明显影响,但R＆D经费投入对于产出增长的贡献更为明显,其弹性系数为0．835．在此基础上,针对性地提出提升福建省电子信息产业R＆D投入产出效益的对策建议,如加大对电子信息产业的资金支持力度,提升R＆D人员投入层次,提高专利产出转化为产值的效率等．     

Investigation of natural and anthropogenic hydrocarbon inputs in sediments using geochemical markers. II. Sao Sebastião, SP--Brazil

The S?o Sebasti?o Channel, NE S?o Paulo State, Brazil, is an area of environmental interest of that state not only because of the tourism, but also because of the presence of the most important oil terminal of Brazil, the PETROBRAS Maritime Terminal (DTCS). Sediment samples were collected at 15 sites in the channel, extracted and analyzed by GC/FID and GC/MS for composition and levels of the following organic geochemical markers: aliphatic hydrocarbons (normal and isoprenoid alkanes), petroleum biomarkers, linear alkylbenzenes (LABs) and polycyclic aromatic hydrocarbons (PAHs). The total concentrations varied from 0.04 to 8.53 micorg g(-1) for aliphatics, from 51.1 to 422.0 ng g(-1) for petroleum biomarkers, from 12.6 to 27.7 ng g(-1) for LABs and from 20.4 to 200.3 ng g(-1) for PAHs. The PETROBRAS Maritime Terminal (DTCS), Sao Sebasti?o Harbor and sewage outfalls along the area had clear influences on the geochemical marker concentrations, especially at locales in the central and north parts of the channel.     

Sensitivity analysis of submersibles’ manoeuvrability and its application to the design of actuator inputs

The influences of hydrodynamic coefficients on the prediction of manoeuvrability were examined by sensitivity analysis (SA) of direct method. The equations of motion used were the standard equations of motion for submarine [Gertler, M., Hagen, G.R., 1967. Standard equations of motion for submarine simulation. DTNSRDC Report], and three submersibles with different appendages were considered. Numerical simulations of three types of sea trials are performed to obtain the sensitivities of motions to hydrodynamic coefficients. Since the accuracy of hydrodynamic coefficients’ estimates is increased by the use of sensitivity-maximizing inputs, the sensitivity-optimal actuator commands that are sequences of bang-bang type inputs were deduced with genetic algorithm (GA) optimization technique.