Submarine groundwater discharge and seasonal hypoxia off the Changjiang River Estuary

Hypoxia is a common phenomenon in the sea adjacent to the Changjiang River Estuary(CJE),one of the global major estuaries.Submarine groundwater discharge(SGD)is a widely recognized pathway for terrestrial materials entering the sea,and has been found to be significant off the CJE.We used a^(222)Rn mass balance model to estimate the SGD fluxes off the CJE and showed that it is linked to seasonal dissolved oxygen(DO)variations.Average SGD fluxes were estimated to be(0.012±0.010)m^(3)/(m^(2)·d)in winter,(0.034±0.015)m^(3)/(m^(2)·d)in summer,and(0.020±0.010)m^(3)/(m^(2)·d)in autumn.We found a significant negative correlation between DO concentrations and SGD rates with groundwater discharge being highest in the summer flood season.In addition,distribution patterns of SGD and hypoxia zones in summer are spatially overlapped,indicating that SGD is an important contributor to summer hypoxia in this region.

Using Natural Radionuclides to Trace Sources of Suspended Particles in the Lower Reaches of the Yellow River

Natural radionuclides are powerful tools for understanding the sources and fate of suspended particulate matter(SPM).Particulate matter with different particle sizes behaves differently with respect to adsorption and desorption.We analyzed the activi-ties and distribution characteristics of multiple natural radionuclides(238U,226Ra,40K,228Ra,7Be and 210Pbex)on size-fractionated SPM at the Lijin Hydrographic Station(Huanghe or Yellow River)every month over a one-year period.Results showed that medium silt(16–32µm)was the main component.As expected,the activity of each radionuclide decreased with an increase of particle size.We examined the sources of SPM with different particle sizes using activity ratios of 226Ra/238U,228Ra/226Ra,40K/238U and 7Be/210Pbex,and concluded that SPM with different particle sizes originated from different sources.Our results indicate that fine SPM(<32µm)was mainly from the erosion of soil along the lower reaches of the Yellow River,while coarse SPM(>32µm)was mainly derived from resuspension of riverbed sediment.During high runoff periods,the concentration of SPM increased significantly,and the pro-portion of fine particles originating upstream increased.Naturally occurring radioactive isotopes,especially on size-fractionated par-ticles,are therefore seen as useful tracers to understand the sources and behaviors of riverine particles transported from land to sea.

Interaction between Downslope and Alongslope Processes on the Margins of Daihai Lake,North China:Implication for Deltaic Sedimentation Models of Lacustrine Rift Basin

Daihai Lake, a modern lacustrine rift basin, located in Inner Mongolia, North China, serves as an important modern analog for understanding deltaic depositional processes in an active rift setting. Two of the deltas （Yuanzigou delta and Bulianghe delta） on the margins of Daihai Lake were surveyed to compare and contrast stacking patterns using aerial photographs, field trenching and sediment sampling. Shallow cores and trench data collected from the margins of Daihai Lake indicate that a variety of depositional processes have been active since Daihai Lake formed. Two 3-D sedimentation models which employ chronostratigraphic correlation technique were generated. The chronostratigraphic sedimentation models predict and represent the architectures and sand-body continuity of sediments. Stratigraphical coincidence of the broad sheeted drifts and channel erosion suggests a coupling between downslope and alongslope processes. Distributary mouth bars are prevalent in the front of deltas on steeper slopes due to the dominance of down-slope flows. On the contrary, the along-slope currents favor the development of distal bar deposits with sheeted sandbodies on gentle depositional slopes. This study provides an insight into the architecture of complex sedimentary facies associated with highlighting key differences between downslope flows and alongslope currents. The distribution of sand within these deltas is of particular interests, with applications in understanding the architecture of hydrocarbon reservoirs formed in lacustrine rift basin.

Adaptive and local analysis of climate data

This paper focuses on how to extract physically meaningful information from climate data,with emphases placed on adaptive and local analysis. It is argued that many traditional statistical analysis methods with rigorous mathematical footing may not be efficient in extracting essential physical information from climate data;rather,adaptive and local analysis methods that agree well with fundamental physical principles are more capable of capturing key information of climate data. To illustrate the improved power of adaptive and local analysis of climate data,we also introduce briefly the empirical mode decomposition and its later developments.

The Dietary Importance of Kelp-Derived Detritus to Pelagic and Benthic Consumers along the West Coast of Vancouver Island, Canada

Stable isotope analysis was used to determine the relative dietary importance of kelp-derived detritus to plankton and benthic organisms along a gradient of kelp abundance driven by recovering sea otter populations along the west coast of Vancouver Island (WCVI), Canada. The study used region-specific kelp isotope values (δ13C and δ15N) and season-specific phytoplankton isotope values to model dietary contributions of kelp-derived detritus (KDD). In general, KDD contributions were moderate to high in most plankton size fractions during the summer and decreased during the winter, particularly in the kelp sparse region. Hypothesized regional and spatial (distance from the coast) differences in kelp detritus contributions to zooplankton were not evident. Modeled estimates of the KDD contribution to benthic invertebrates were high (>40%) and independent of the organism size, among regions and between seasons, with the exception of Astraea gibberosa in the kelp abundant region. Local oceanography, natural kelp isotope signature variation, and significant overlap between kelps’ and blooming phytoplankton isotope values led to a large uncertainty in the assessed KDD contributions in benthic organisms. These results highlighted the importance of the KDD as a widespread and stable year-round food source in coastal kelp populated regions.

Interaction between in situ stress states and tectonic faults:A comment

Understanding the in situ stress state is crucial in many engineering problems and earth science research.The present article presents new insights into the interaction mechanism between the stress state and faults.In situ stresses can be influenced by various factors,one of the most important being the existence of faults.A fault could significantly affect the value and direction of the stress components.Reorientation and magnitude changes in stresses exist adjacent to faults and stress jumps/discontinuities across the fault.By contrast,the change in the stress state may lead to the transformation of faulting type and potential fault reactivation.Qualitative fault reactivation assessment using characteristic parameters under the current stress environment provides a method to assess the slip tendency of faults.The correlation between in situ stresses and fault properties enhances the ability to predict the fault slip tendency via stress measurements,which can be used to further refine the assessment of the fault reactivation risk.In the future,stress measurements at greater depths and long-term continuous real-time stress monitoring near/on key parts of faults will be essential.In addition,much attention needs to be paid to distinguishing the genetic mechanisms of abnormal stress states and the type and scale of stress variations and exploring the mechanisms of pre-faulting anomaly and fault reactivation.

Impact of Reservoir Properties on the Production of the Mannville Coal Measures, South Central Alberta from a Numerical Modelling Parametric Analysis

Numerical simulations are used to investigate the impact of intrinsic and extrinsic reservoir properties on the production from coal and organic rich lithologies in the Lower Cretaceous Mannville coal measures of the Western Canadian Sedimentary Basin. The coal measures are complex reservoirs in which production is from horizontal wells drilled and completed in the thickest coal seam in the succession (1 m versus 3 m), which has production and pressure support from thinner coals in the adjacent stratigraphy and from organic-rich shales interbedded and over and underlying the coal seams. Numerical models provide insight as to the relative importance of the myriad of parameters that may impact production that are not self-evident or intuitive in complex coal measures.

A Velocity Dealiasing Scheme for C-band Weather Radar Systems

A dealiasing algorithm for radar radial velocity observed by C-band Doppler radars is presented as an extension of an existing S-band dealiasing algorithm. This has operational significance in that many portable and many commercial broadcast radars, as well as approximately one half of the Chinese weather radar network （CINRAD）, are C-band radars. With a wavelength of about 5 cm, the Nyquist interval of C-band radars is just about one half that of S-band radars （wavelength of about 10 cm） and thus has more velocity folding. The proposed algorithm includes seven modules to remove noisy data, find the starting radials, dealias velocities, and apply least squares error checking in both the radial and azimuth directions. The proposed velocity dealiasing method was applied to one widespread rain case and three strong convective cases from radars operating in China. It was found that, on average, 92.95% of the aliased radial velocity data could be correctly de-aliased by the algorithm, resulting in 96.65% of the data being valid.

Grid-cell Aerosol Direct Shortwave Radiative Forcing Calculated Using the SBDART Model with MODIS and AERONET Observations：An Application in Winter and Summer in Eastern China

Taking winter and summer in eastern China as an example application, a grid-cell method of aerosol direct radiative forcing（ADRF） calculation is examined using the Santa Barbara DISORT Atmospheric Radiative Transfer（SBDART） model with inputs from MODIS and AERONET observations and reanalysis data. Results show that there are significant seasonal and regional differences in climatological mean aerosol optical parameters and ADRF. Higher aerosol optical depth（AOD）occurs in summer and two prominent high aerosol loading centers are observed. Higher single scattering albedo（SSA） in summer is likely associated with the weak absorbing secondary aerosols. SSA is higher in North China during summer but higher in South China during winter. Aerosols induce negative forcing at the top of the atmosphere（TOA） and surface during both winter and summer, which may be responsible for the decrease in temperature and the increase in relative humidity.Values of ADRF at the surface are four times stronger than those at the TOA. Both AOD and ADRF present strong interannual variations; however, their amplitudes are larger in summer. Moreover, patterns and trends of ADRF do not always correspond well to those of AOD. Differences in the spatial distributions of ADRF between strong and weak monsoon years are captured effectively. Generally, the present results justify that to calculate grid-cell ADRF at a large scale using the SBDART model with observational aerosol optical properties and reanalysis data is an effective approach.

Impacts of prior parameter distributions on Bayesian evaluation of groundwater model complexity

This study used the marginal likelihood and Bayesian posterior model probability for evaluation of model complexity in order to avoid using over-complex models for numerical simulations. It focused on investigation of the impacts of prior parameter distributions(involved in calculating the marginal likelihood) on the evaluation of model complexity. We argue that prior parameter distributions should define the parameter space in which numerical simulations are made. New perspectives on the prior parameter distribution and posterior model probability were demonstrated in an example of groundwater solute transport modeling with four models, each simulating four column experiments. The models had different levels of complexity in terms of their model structures and numbers of calibrated parameters. The posterior model probability was evaluated for four cases with different prior parameter distributions. While the distributions substantially impacted model ranking, the model ranking in each case was reasonable for the specific circumstances in which numerical simulations were made. For evaluation of model complexity, it is thus necessary to determine the parameter spaces for modeling, which can be done by conducting numerical simulation and usineg engineering judgment based on understanding of the system being studied.

The P-T-t-D evolution of the Mahabharat,east-central Nepal:The out-of-sequence development of the Himalaya

A garnet-bearing schist from the southernmost such exposure along the Himalaya in east central Nepal records prograde metamorphism at 32.4±0.3 Ma.Phase equilibria modelling,combined with Ti-in-biotite and quartz caxis thermometry,outline a tight-to-hairpin pressure-temperature(P-T)path extending from~515℃ and 5.5 kbar to peak conditions at~575℃ and 7 kbar followed by deformation during the retrograde phase at 480-515℃ and 6-7 kbar.The new geochronology data place an upper bound on the evolution of metamorphism and deformation in the frontal-most part of the Himalaya,which lasted until 17.5 Ma,as indicated by previously published ^(40)Ar/^(39)Ar data.The P-T-time data from this part of the Himalaya,as well as that from more hinterlandward portions of the orogen,outline a progressive,stepwise,commonly out-of-sequence evolution.Further data from along the orogen indicates that this evolution is not a local phenomenon,but instead characterizes the tectonics of this system as a whole.

Contribution to Gas Production from Minor Coal Seams and Adjacent Shales: Numerical Modelling Results for the Mannville Coal Measures, South Central Alberta

The contribution to production of the gas stored within the coal and shale beds adjacent to the main coal seam in the Mannville Group, in which a lateral is drilled, was investigated through a series of numerical simulations. The results indicate that the added gas from the minor coal seams, with interbedded shales with no gas, results in 1.4 times (×) more produced gas and 3.0× more produced water after 25 years of production than when only the main Mannville coal seam is considered. Including gas in the shales results in 1.7× more produced gas and 2.5× more produced water after 25 years of production than when only the main coal seam is considered. The produced gas recovered from the shales exceeds the produced gas recovered from the coals after ~8.5 years, resulting in 2.1× more produced shale gas than coal gas after 25 years of production. Over half (56%) of the produced coal gas after 25 years of production is recovered from the main coal seam while a quarter (22%) is recovered from the L1 seam, which is the thickest and nearest minor coal seam to the horizontal wellbore located in the main seam. The results from the numerical simulations provide insights that are not intuitive or otherwise predictable in developing complex reservoirs. Although the results are specifically for the Mannville producing fairway, undoubtedly the production from minor coal seams and interbedded gas shales should be considered in other producing and potential coal gas reservoirs to identify higher producible reserves and optimize drilling and completions strategies.

Submarine groundwater discharge and benthic biogeochemical zonation in the Huanghe River Estuary

Submarine groundwater discharge(SGD)has received increasing attention by studies on coastal areas;however,its effects on biogeochemical zonation have not been investigated to date.The Huanghe River Estuary(HRE)is a world class river estuary with high turbidity,and heavy human regulation.This study investigated how SGD is related to the benthic biogeochemistry of the HRE.Based on the distribution of several parameters(e.g.,salinity,temperature,dissolved oxygen(DO)levels,p H,radium isotopes,and nutrients),the HRE was subdivided into six different zones,and the SGD fluxes within each zone were quantified and compared.The highest SGD flux was found in the northwest nearshore zone,where it was more than one order of magnitude higher than in the offshore zone.High SGD resulted in low DO and p H,but high nutrient levels in the benthic boundary layer.The southeast nearshore zone was also characterized by high SGD flux,but benthic waters were more oxic because of the dominating inputs by the Huanghe River.These data suggest that such a zonation would help to understand benthic biogeochemical processes.High SGD may not only contribute to the estuarine nutrient budget,but may also contribute to the formation of hypoxia and acidification.

Foodweb Trophic Level and Diet Inference Using an Extended Bayesian Stable Isotope Mixing Model

You are what you eat (diet) and where you eat (trophic level) in the food web. The relative abundance of pairs of stable isotopes of the organic elements carbon (e.g., the isotope ratio of 13C vs 12C), nitrogen, and sulfur, among others, in the tissues of a consumer reflects a weighted-average of the isotope ratios in the sources it consumes, after some corrections for the processes of digestion and assimilation. We extended a Bayesian mixing model to infer trophic positions of consumer organisms in a food web in addition to the degree to which distinct resource pools (diet sources) support consumers. The novel features in this work include: 1) trophic level estimation (vertical position in foodweb) and 2) the Bayesian exposition of a biologically realistic model [1] including stable isotope ratios and concentrations of carbon, nitrogen, and sulfur, isotopic fractionations, elemental assimilation efficiencies, as well as extensive use of prior information. We discuss issues of parameter identifiability in the complex and most realistic model. We apply our model to simulated data and to bottlenose dolphins (Tursiops truncatus) feeding on several numerically abundant fish species, which in turn feed on other fish and primary producing plants and algae present in St. George Sound, FL, USA. Finally, we discuss extensions from other work that apply to this model and three important general ecological applications. Online supplementary materials include data, OpenBUGS scripts, and simulation details.

Maximum Magnitude of Seismicity Induced by a Hydraulic Fracturing Stage in a Shale Reservoir: Insights from Numerical Simulations

A key unknown limiting assessment of risk posed by inducing anomalous seismicity during hydraulic fracturing is the potential maximum magnitude of an event. To provide insights into the variation in maximum magnitude that can be induced by a hydraulic fracturing stage, worst-case scenarios were simulated in 2D using coupled hydro-geomechanical models. The sensitivity of the magnitude to the hydro-geomechanical properties of the fault and matrix rock were quantitatively compared through parametric analysis. Our base model predicts a maximum event with moment magnitude (Mw) 4.31 and Mw values range from 3.97 to 4.56 for the series of simulations. The highest magnitude is predicted for the model with a longer fault and the lowest magnitude for the model with a smaller Young’s modulus. For our models, the magnitude is most sensitive to changes in the Young’s modulus and length of the fault and least sensitive to changes in the initial reservoir pressure (i.e. pore pressure) and the Poisson’s ratio.

In Situ Filtration Rates of Blue Mussels(Mytilus edulis)Measured by an Open-Top Chamber Method

Blue mussels, Mytilus edulis , form dense beds of both commercial and ecological importance, and many attempts have been made to determine their filtration rate. The total time in which mussels actually utilise their filtration capacity in nature varies greatly, making in situ methods for filtration rate measurements relevant. Further, it is being debated to what extend filtration rates measured in the laboratory using cultivated algal cells may apply for mussels in nature. In the present study, we have used an open-top chamber setup in order to allow repeated in situ filtration rate measurements of M. edulis using ambient natural phytoplankton and free-living bacteria. We found that the in situ measured filtration rates are comparable to filtration rates obtained in laboratory studies using different methods and controlled diets of cultivated algal cells. Further, we found that the retention efficiency of free-living bacteria was between 22.2% and 29.9%, in good agreement with values from laboratory studies. Our findings support the assumption that mussels in nature tend to use their filtration capacity when the phytoplankton concentration is above a certain lower trigger level.

胶东新立构造蚀变岩型金矿床元素地球化学行为

新立金矿位于华北克拉通东部胶东金矿省内,是一个典型的蚀变岩型(焦家型)金矿床,矿床受区域三山岛-仓上断裂带控制,产出于蚀变的玲珑花岗岩中。在主断裂带下盘蚀变矿化发育,可以划分为五个阶段:钾长石化阶段、绢英岩化阶段、黄铁绢英岩矿化阶段、多金属硫化物矿化阶段和碳酸盐化阶段。不同的蚀变矿化过程导致各阶段样品具有不同的矿物组合和地球化学特征。钾长石化花岗岩以高钾钠含量为特征,因为样品中含有新生成的二次钾长石及残留的钠长石;绢英岩的钙钠含量明显低于钾长石化花岗岩,是绢英岩化阶段斜长石蚀变分解所致;黄铁绢英岩FeT2O3含量普遍较高且SiO 2含量波动明显,与该阶段样品中大量黄铁矿的产出及部分样品中包含石英团块或石英脉相一致;多金属硫化物矿化样品的元素含量与黄铁绢英岩基本类似;碳酸盐化蚀变样品以高CaO含量为特征,与该阶段大量沉淀析出的方解石相符。在原始地幔标准化微量元素配分图上,不同阶段矿化蚀变样品,大离子亲石元素Rb、Ba、K、Sr差异性明显,而高场强元素Zr、Hf、Nb、Ta、P差异性较小,表明热液蚀变过程中大离子亲石元素活动性较强,高场强元素相对稳定。在稀土元素球粒陨石标准化图中,不同阶段样品均呈明显的右倾性,蚀变早期(钾长石化阶段)样品铕异常不明显,蚀变矿化主期(绢英岩化阶段至多金属硫化物矿化阶段)样品普遍具有负铕异常,而蚀变晚期(碳酸盐化阶段)样品普遍具有正铕异常。元素相关性分析表明,金与银、砷、铋和硫具明显正相关,与铜、铅具有一定的相关性。成矿元素因子分析也显示出金与砷、硫、铁、钴在矿化过程中具有类似的地球化学行为。实测剖面上不同位置样品元素地球化学特征的差异性主要受构造及蚀变矿化类型、强度控制,成矿元素在主断裂附近达到峰值,在远离主断裂方向上,其含量整体呈下降趋势,但在次级矿化断裂发育地段,含量又明显回升;另外在断裂附近由于微裂隙及节理相对发育,有利于热液的渗透,蚀变较强,对成矿元素的空间分布亦具有控制作用。

Molecular signatures of soil-derived dissolved organic matter constrained by mineral weathering

Dissolved organic matter(DOM)in soils drives biogeochemical cycling and soil functions in different directions depending on its molecular signature.Notably,there is a distinct paucity of information concerning how the molecular signatures of soil DOM vary with different degrees of weathering across wide geographic scales.Herein,we resolved the DOM molecular signatures from 22 diverse Chinese reference soils and linked them with soil organic matter and weathering-related mineralogical properties.The mixed-effects models revealed that the yields of DOM were determined by soil organic carbon content,whereas the molecular signature of DOM was primarily constrained by the weathering-related dimension.The soil weathering index showed a positive effect on the lability and a negative effect on the aromaticity of DOM.Specifically,DOM in highly weathered acidic soils featured more amino sugars,carbohydrates,and aliphatics,as well as less O-rich polyphenols and condensed aromatics,thereby conferring a higher DOM biolability and lower DOM aromaticity.This study highlights the dominance of the weathering-related dimension in constraining the molecular signatures and potential functions of DOM in soils across a wide geographic scale.

Impact of FY-3A MWTS radiances on prediction in GRAPES with comparison of two quality control schemes

The impact of Microwave Temperature Sounder （MWTS） radiances on the prediction of the Chinese Numerical Weather prediction （NWP） system-GRAPES （Global and Regional Assimilation and PrEdiction System） with comparison of two Quality Control （QC） schemes was researched. The main differences between the two schemes are cloud detection, O-B （brightness temperature difference between observation and model simulation） check and thinning. To evaluate the impact of the two QC schemes on GRAPES, a typhoon case study and cycle experiments were conducted. In the typhoon case study, two experiments were conducted using both the new and old QC schemes. The results show that outliers are removed in the new QC while they exist in the old QC. The analysis and the model forecast are subsequently generated after assimilating data from the two QC schemes. The model-predicted steering flows more southward with the new QC scheme, and as a result, the forecast track in the experiments is more southward, i.e., closer to the best track than the old scheme. In addition to the case study, four impact cycle experiments were conducted for 25-day periods. The results show that the new QC scheme removed nearly all the biases whereas the old scheme could not. Furthermore, the mean and standard deviation of analysis increments with the new scheme is much smaller than those of O-B. In contrast, the old scheme values are either slightly smaller or the same. Verifications indicate that forecast skill is improved after applying the new scheme. The largest improvements are found in the Southern Hemisphere. According to the results above, MWTS with the new QC scheme can improve the GRAPES forecast.

Oxygen isotopic variations in modern cetacean teeth and bones： implications for ecological, paleoecological, and paleoclimatic studies

The oxygen isotope ratios(d18O) preserved in marine sediments have been widely used to reconstruct past ocean temperatures. However, there remain significant uncertainties associated with this method, owing to assumptions about the d18 O of ancient seawater which affects the temperature inferred from sediment d18 O records. In this study, oxygen isotope compositions of phosphate in teeth and bones from five different modern cetacean species, including sperm whale, pygmy sperm whale, short-finned pilot whale, killer whale, and Cuvier's beaked whale, and three fossil whales were determined. The data were used to assess whether the oxygen isotope ratios of biogenic phosphate(d18Op) from cetaceans are a reliable proxy for the oxygen isotopic composition of ocean water(d18Ow). The d18 Opvalues of modern cetaceans range from15.5 % to 21.3 %, averaging(19.6 %± 0.8 %)(n = 136).Using a greatly expanded global cetacean d18 Opdataset, the following regression equation is derived for cetaceans:d18Ow= 0.95317(±0.03293) d18Op- 17.971(±0.605),r = 0.97253. The new equation, when applied to fossil teeth and bones, yielded reasonable estimates of ancient seawater d18 Owvalues. Intra-tooth isotopic variations were observed within individual teeth. Among the selected species, the killer whale(O. orca) has the lowest d18 Opvalues and the largest intra-tooth d18 Opvariation, reflecting its habitat preference and migratory behavior. The results show that oxygen isotope analysis of phosphate in cetacean teeth and dense ear bones provides a useful tool for reconstructing the oxygen isotopic composition of seawater and for examining environmental preferences(including migratory behavior)of both modern and ancient whales.