Preparation of the sea water reference material for trace metals,NASS-1

The preparation of a sea water reference material, NASS-1, is described. The sea water is an open ocean sample, salinity 35.07‰, gathered at the 1300 metre level in the North Atlantic, south-east of Bermuda. It is acidified to pH 1.6 with nitric acid and bottled in 2 1 polyethylene bottles. Reliable values are available for 11 trace metals (As, Cd, Cr, Co, Cu, Fe, Pb, Mn, Mo, Ni and Zn). The results of a long-term sea water storage experiment are also described.     

Repeatability enhancement in deep-water permanent seismic installations: a dynamic correction for seawater velocity variations

With the increasing use of permanently installed seismic installations, many of the issues in time‐lapse seismic caused by the lack of repeatability can be reduced. However, a number of parameters still influence the degree of reliability of 4D seismic data. In this paper, the specific impact of seawater velocity variations on time‐lapse repeatability is investigated in a synthetic study. A zero‐lag time‐lapse seabed experiment with no change in the subsurface but with velocity changes in the water column is simulated. The velocity model in the water column is constant for the baseline survey while the model for the repeat survey is heterogeneous, designed from sea salinity and temperature measurements in the West of Shetlands. The difference section shows up to 80% of residual amplitude, which highlights the poor repeatability. A new dynamic correction which removes the effect of seawater velocity variations specifically for permanent installations is developed. When applied to the synthetic data, it reduces the difference residual amplitude to about 3%. This technique shows substantial improvement in repeatability beyond conventional time‐lapse cross‐equalization.     

Disintegration of Sludge by Sonication and Improvement of Methane Production Rates in Batch Anaerobic Digesters

Sludge pretreatment prior to anaerobic digestion has been found to reduce sludge production in wastewater treatment. Sludge disintegration using physical, chemical, biological, or mechanical methods can increase biogas production and reduce sludge quantities. Ultrasonication is one of the most effective means of mechanical disintegration. This study aims to investigate ultrasonication as a means for solubilizing waste activated sludge (WAS) to enhance its digestability. Sonication was applied by the use of two different probes providing different powers and energies into the sludge after which the soluble chemical oxygen demand (sCOD) increases were measured. The samples were then digested anaerobically in 250 mL serum bottles for about 50 days. Along with the biogas measurements, the rate of methane production is calculated to be able to quantify the effect of pretreatment and compare the results between different applications. The results showed that with the increase of sonication power and sonication time, sCOD increased. An introduction of higher sonication energy made the sCOD rise sharply, however, this increase was not indefinite; it became gradually lower with the further increase of energy. The results indicated that specific methane production, specific methane yield, and the first order methane generation rate increased with increasing energy input.     

Effect of organic matter source and salinity on dissolved organic matter isolation via ultrafiltration and solid phase extraction

In this study, samples were taken from three contrasting freshwater sources and amended with salt in order to determine the influence of salinity and dissolved organic matter (DOM) composition on DOM recovery via ultrafiltration and solid phase extraction (SPE) with C₁₈ disks. Salt addition caused variable recovery of DOM when using C₁₈ SPE, and ultraviolet–visible spectroscopic characterization of the extracted material showed spectral responses that varied among sample sources. In contrast, increasing sample salinity from 0 to 30 ppt consistently caused a 15–25% reduction in the amount of high molecular weight DOM isolated by ultrafiltration for both dissolved organic carbon (DOC) and chromophoric DOM (CDOM), regardless of DOM composition. We hypothesize that a change in conformation (such as coiling or disaggregation) of DOM molecules occurs in the presence of salt, allowing them to pass through the ultrafiltration membrane and thereby decreasing the DOM retained by ultrafiltration. These results are important because they demonstrate that changes in salinity can influence DOM recovery in estuaries. Interpretation of DOM characteristics along estuarine gradients needs to account for potential artifacts introduced by sample isolation techniques.     

The long-term salinity field in San Francisco Bay

Data are presented on long-term salinity behaviour in San Francisco Bay, California. A two-level, width averaged model of the tidally averaged salinity and circulation has been written in order to interpret the long-term (days to decades) salinity variability. The model has been used to simulate daily averaged salinity in the upper and lower levels of a 51 segment discretization of the Bay over the 22-yr period 1967–1988. Monthly averaged surface salinity from observations and monthly-averaged simulated salinity are in reasonable agreement. Good agreement is obtained from comparison with daily averaged salinity measured in the upper reaches of North Bay.The salinity variability is driven primarily by freshwater inflow with relatively minor oceanic influence. All stations exhibit a marked seasonal cycle in accordance with the Mediterranean climate, as well as a rich spectrum of variability due to extreme inflow events and extended periods of drought. Monthly averaged salinity intrusion positions have a pronounced seasonal variability and show an approximately linear response to the logarithm of monthly averaged Delta inflow. Although few observed data are available for studies of long-term salinity stratification, modelled stratification is found to be strongly dependent on freshwater inflow; the nature of that dependence varies throughout the Bay. Near the Golden Gate, stratification tends to increase up to very high inflows. In the central reaches of North Bay, modelled stratification maximizes as a function of inflow and further inflow reduces stratification. Near the head of North Bay, lowest summer inflows are associated with the greatest modelled stratification. Observations from the central reaches of North Bay show marked spring-neap variations in stratification and gravitational circulation, both being stronger at neap tides. This spring-neap variation is simulated by the model. A feature of the modelled stratification is a hysteresis in which, for a given spring-neap tidal range and fairly steady inflows, the stratification is higher progressing from neaps to springs than from springs to neaps.The simulated responses of the Bay to perturbations in coastal sea salinity and Delta inflow have been used to further delineate the time-scales of salinity variability. Simulations have been performed about low inflow, steady-state conditions for both salinity and Delta inflow perturbations. For salinity perturbations a small, sinusoidal salinity signal with a period of 1 yr has been applied at the coastal boundary as well as a pulse of salinity with a duration of one day. For Delta inflow perturbations a small, sinusoidally varying inflow signal with a period of 1 yr has been superimposed on an otherwise constant Delta inflow, as well as a pulse of inflow with a duration of one day. Perturbations in coastal salinity dissipate as they move through the Bay. Seasonal perturbations require about 40–45 days to propagate from the coastal ocean to the Delta and to the head of South Bay. The response times of the model to perturbations in freshwater inflow are faster than this in North Bay and comparable in South Bay. In North Bay, time-scales are consistent with advection due to lower level, up-estuary transport of coastal salinity perturbations; for inflow perturbations, faster response times arise from both upper level, down-estuary advection and much faster, down-estuary migration of isohalines in response to inflow volume continuity. In South Bay, the dominant time-scales are governed by tidal dispersion.     

Upper mixed layer temperature anomalies at the North Atlantic storm-track zone

Synoptic sea surface temperature anomalies (SSTAs) were determined as a result of separation of time scales smaller than 183 days. The SSTAs were investigated using daily data of ocean weather station “C” (52.75°N; 35.5°W) from 1 January 1976 to 31 December 1980 (1827 days). There were 47 positive and 50 negative significant SSTAs (lifetime longer than 3 days, absolute value greater than 0.10 °C) with four main intervals of the lifetime repetitions: 1. 4–7 days (45% of all cases), 2. 9–13 days (20-25%), 3. 14–18 days (10-15%), and 4. 21–30 days (10-15%) and with a magnitude 1.5-2.0 °C. An upper layer balance model based on equations for temperature, salinity, mechanical energy (with advanced parametrization), state (density), and drift currents was used to simulate SSTA. The original method of modelling taking into account the mean observed temperature profiles proved to be very stable. The model SSTAs are in a good agreement with the observed amplitudes and phases of synoptic SSTAs during all 5 years. Surface heat flux anomalies are the main source of SSTAs. The influence of anomalous drift heat advection is about 30-50% of the SSTA, and the influence of salinity anomalies is about 10-25% and less. The influence of a large-scale ocean front was isolated only once in February-April 1978 during all 5 years. Synoptic SSTAs develop just in the upper half of the homogeneous layer at each winter. We suggest that there are two main causes of such active sublayer formation: 1. surface heat flux in the warm sectors of cyclones and 2. predominant heat transport by ocean currents from the south. All frequency functions of the ocean temperature synoptic response to heat and momentum surface fluxes are of integral character (red noise), though there is strong resonance with 20-days period of wind-driven horizontal heat advection with mixed layer temperature; there are some other peculiarities on the time scales from 5.5 to 13 days. Observed and modelled frequency functions seem to be in good agreement.     

REE in the Great Whale River estuary, northwest Quebec

We report rare earth element (REE) concentrations of a longitudinal profile within the estuary of the Great Whale River in northwest Quebec and in Hudson Bay. All of the measured REE have concentrations less than those predicted by conservative mixing of seawater and river water, demonstrating removal of the REE from solution. REE removal is rapid, occurring primarily at salinities less than 2‰. Removal of the REE is greatest for the light REE, and ranges from about 7% for the light REE to no more than 40% for the heavy REE. Fe removal is essentially complete at low salinity. The shape of the Fe and REE vs. salinity profiles is not consistent with a simple model of destabilization and coagulation of iron and REE-bearing colloidal material. A linear relationship between the activity of free ion REE³⁺ and pH is consistent with a simple ion-exchange model for REE removal.Surface and subsurface samples of Hudson Bay seawater are characterized by high REE concentrations and high La/Yb relative to average seawater. The subsurface sample has a Nd concentration of 100 pmol/kg and an ε_Nd of −29.3 ± 0.3. These characteristics are consistent with the high REE concentration, high La/Yb, and low ε_Nd of river inputs into Hudson Bay. These results indicate that rivers draining the Canadian Shield are a major source of non-radiogenic Nd and REE to the Atlantic Ocean. We estimate that outflow of water from Hudson Bay to the Labrador Sea could supply ≈ 30% of the non-radiogenic Nd in North Atlantic Deep Water.     

Dynamics of Microbiological Contamination at a Marine Recreational Site

Levels of bacterial indicators of pollution are related with marine salinity and turbidity at both high tide (HT) and low tide (LT). The salinity varied from values around 26.9 ppm at the LT and 28.6 ppm at the high tide but affected total and faecal coliform (FC) estimates. Salinity readings of 25–30 ppm produced microbial counts below 10⁻² MPN/100 ml total coliforms (TCs) whereas salinity of 15–22 ppm produced a TC level of 4.6×10⁻⁴ MPN/100 ml. Turbidity peaks in the samples are accompanied by peaks of microbial contamination of the seawater indicating that the contamination is normally deposited at the marine sediment rather than in the water column. In fact, samples collected under heavy stormy weather, in which the water agitation resulted in turbidity values up to 68.3 NTU, produced maximum microbial counts.     

Experimental study of loess disintegration characteristics

Loess structures with large joints and fissures often undergo natural disintegration when subjected to contact with water. The slaking of loess results in the formation of loess gullies, caves, and landslides. To study the disintegration properties and the factors influencing them, we carried out field and laboratory tests. First, we carried out an in situ disintegration test using different sample shapes obtained from Heifangtai and analysed the effect of soil sample shape on loess disintegration. We then developed an improved disintegrator and tested the effect of different factors on the disintegration of loess. The effects of water content, salinity, and composition on disintegration are discussed. The results show that the loess disintegration process can be divided into three broad stages – wetting, softening, and subsidence – the disintegration is mainly concentrated in the third stage, while the first two stages are short and show very weak disintegration. The main factors influencing the disintegration of loess samples are shape, size, and clay mineral content. During the in situ disintegration test, the edge angles of soil samples are disintegrated, to soften all their edges. Disintegration duration increases with increasing sample size, but the extent of disintegration was found to decrease. Disintegration duration is inversely proportional to the loess disintegration rate. The loess disintegration rate is positively correlated with water temperature within a certain range; however, the reverse is observed with soil sample size and initial water content, and salinity was found to have little effect on the disintegration rate. Higher clay content of cohesive soil and weaker permeability leads to a slower disintegration rate. Additionally, lower cementation may easily cause loess disintegration. © 2019 John Wiley & Sons, Ltd.     

Experimental investigation of injectivity alteration due to salt precipitation during CO2 sequestration in saline aquifers

Injection of CO₂ into saline aquifers causes the geochemical reaction of rock-fluid and salt precipitation due to the evaporation of water as a physical process. Well injectivity is an important issue in carbon capture and storage (CCS) projects because large volumes of CO₂ must be stored for a long time and salt precipitation can significantly reduce injectivity by reducing the permeability. The impact of salt precipitation on the injectivity must therefore be specified in order to maintain the security of CCS projects and enable them to perform at a high level of practicality. The objective of this work is to investigate the influence of the injection rate and brine salinity on injectivity reduction due to evaporation and salt precipitation. In this study, we injected supercritical CO₂ into a sandstone rock sample fully saturated with NaCl brine to characterize the salt precipitation induced by the evaporation process.Evaporation is investigated by mass measurement of the water and vapor produced. The extension in time of salt precipitation and the precipitation profile are analyzed by drying rate measurement, Capillary number and Peclet number. The consequences of salt precipitation on injectivity are specified by permeability and relative permeability analysis. The results show that a high drying rate in the early stage of injection induces rapid salt precipitation. The level of salt precipitation increases with salinity, within a permeability reduction range of 21–66%, and decreases with the injection rate, within a permeability reduction range of 43–62%. The relative permeability of CO₂ is affected by both the injection rate and salinity.     

Evaluation of the mussel Perna perna as a biomonitor of polycyclic aromatic hydrocarbon (PAH) exposure and effects

The mussel Perna perna was used to monitor and assess areas suspected of oil contamination by transplanting animals from unimpacted to impacted sites and vice versa. The deployment lasted for three months during which total PAH were measured in seawater samples collected every 15 days. PAH concentrations were determined in mussel tissue monthly. The lysosomal neutral red assay and the condition index were used as biomarkers of the adverse biological effects. The PAH concentration in mussels at unimpacted sites, prior to deployment was ca. 100 microg kg(-1) but increased to 300 microg kg(-1) after three months at the contaminated site. Mussels transplanted to the uncontaminated site showed a decrease from 380 to 80 microg kg(-1). Significant changes in lysosomal stability occurred within one month of the beginning of the transposition; in contrast condition indexes were not correlated with the observed changes in PAH concentration.     

Spatial and temporal variability of seawater properties,current velocity and SPM concentration off Cassino Beach-Rio Grande-Southern Brazil

Water column profiles and near-bed time series of pressure, current velocity, suspended-particulate matter (SPM) concentration and seawater temperature and salinity were collected during three short cruises carried out in May 2005 in the shoreface and inner shelf area adjacent to Cassino Beach, southern Brazil. The measurements were part of the Cassino Experiment, a project conducted at an open, sandy coastal area known for the occurrence of patches of fairly large amounts of muddy sediments that are sporadically fluidized, transported onshore and eventually stranded on the beach. The study area is close to the Patos Lagoon mouth, being influenced by its water and suspended-sediment discharge. The presence of the Patos Lagoon outflow on the inner shelf was detected in one of the cruises (May 13) through measurements of near-surface salinity: while close to shore salinity was 29.4, a minimum value of 13.8 was measured at ∼10 km from the coast. Four days later, no trace of the plume was detected in the area. Regarding seawater temperature, no large temporal or spatial variability was documented with measured values ranging from 19.3 to 20 °C. Water column currents were prominently to N and NE, except at the outermost station, located ∼42 km from the coast, where NW-directed flows were observed at surface and mid-depth. Maximum near-bed current velocity oscillated between 18 and 42 cm s⁻¹ in the east–west direction and between 14 and 42 cm s⁻¹ in the north–south direction. Near-surface concentration of SPM oscillated between 11 and 99 mg L⁻¹, in general one order of magnitude lower than near-bed values. However, near-bed concentration of SPM showed large spatial variability: the highest value (2200 mg L⁻¹) was yielded by a water sample collected at ∼8 m water depth, at a station located ∼2 km away from the shoreline; two water samples collected 500 m, apart from this station, yielded SPM concentrations of 148 and 205 mg L⁻¹, one order of magnitude lower. Spectral analyses of near-bed current speed and SPM concentration indicate the relevance of oscillations in the low-frequency (<0.05 Hz) range. Detailed sampling of bottom sediment indicated that in May 2005 the mud patch was centered at ∼8.5 m water depth.     

Application of GRACE to the estimation of groundwater storage change in a data-poor region: A case study of Ngadda catchment in the Lake Chad Basin

The present study is to explore the feasibility of GRACE-based estimation of a groundwater storage change in a data-poor region using a case study of the Ngadda catchment in the Lake Chad Basin. Although the Ngadda catchment has only one set of in situ time series data of groundwater from 2006 to 2009 and a limited number of groundwater measurements in 2005 and 2009, GRACE-based groundwater storage change can be evaluated against the in situ groundwater measurements combined with specific yield data. The cross-correlation analysis in the Ngadda catchment shows that maximum rainfall reached in July and August, whereas both the maximum total water storage anomaly and the maximum groundwater storage anomaly occurred 2months later. Whereas the mean annual amplitude of total water storage anomaly is about 17cm from both the average total water storage anomaly from three mascon products and the one from three spherical harmonic products, the mean annual amplitude of soil moisture storage anomaly is substantially varied from 5.58cm for CLM to about 14cm for NOAH and Mosaic. The goodness-of-fit tests show that CLM soil moisture produces the closest estimation of groundwater storage anomaly to the in situ groundwater measurements. The present study shows that GRACE-based estimation for groundwater storage anomaly can be a cost-effective and alternative tool to observe how groundwater changes in a basin scale under the limitation of modelling and in situ data availability.     

Geothermal constraints on the hydrological regime of the TAG active hydrothermal mound, inferred from long-term monitoring

During August 1994 to March 1995, a period that included ODP Leg 158 drilling, bottom-water and sub-bottom temperatures were continuously logged by a long-term temperature monitoring system ‘Daibutsu’ at the base of the central black-smoker complex (CBC) and within the low heat flow zone at the TAG hydrothermal mound on the Mid-Atlantic Ridge. The temperature of hydrothermal fluid at CBC was also measured with a small high-temperature probe ‘Hobo’. Bottom-water temperature variations measured with Daibutsu at both sites have predominant semi-diurnal periods, causing the sub-bottom temperatures to fluctuate at these periods with reduced amplitudes and phase delays at sub-bottom depths. Seawater entrainment into the mound has been previously suggested at the low heat flow zone. We quantitatively evaluate the seawater entrainment rate at both sites from a one-dimensional numerical model, combined with a heat conduction model for the semi-diurnal variations. The entrainment rate of seawater at the base of CBC is estimated as 1.3±0.5×10⁻⁵ m/s, at least from August 17 to 30, 1994. On the other hand, the seawater entrainment rate at the low heat flow zone was undetected by long-term temperature monitoring at shallow sub-bottom depth. Nevertheless an increase in heat flow observed at the low heat flow zone during ODP drilling can be interpreted as a decrease in the entrainment rate of seawater. Before ODP Leg 158, Daibutsu measured three sub-bottom temperature anomalies at the base of CBC not derived from bottom-water temperature variations and Hobo also detected a CBC fluid temperature anomaly, indicating some natural changes in fluid flow within the mound. Daibutsu and Hobo also measured temperature anomalies during and after drilling at the ODP TAG-1 area. The Hobo temperature anomalies are inferred to have occurred when the cold fluid entrained through the drill holes at TAG-1 site reached or cooled the main fluid path to CBC. The entrained seawater through the drill holes appears to have contributed to dissolution and precipitation of anhydrite within the mound and perhaps affected the local permeability structure inside the mound. The temperature anomalies measured with Daibutsu at the base of CBC may have been induced by the change in the fluid flow pattern as a result of such permeability changes within the mound.     

地磁总强度资料在地震预报中的应用

本文应用地磁总强度资料,用两台差消除地磁场短周期变化,同时亦削弱了长期变影响,从而使年变呈线性变化。然后采用趋势面法求得剩余长期变地区性改正量。资料处理后,显示唐山大震前可能有一年半以上的异常,变化幅度约10伽马,对台网中其它几个6级左右地震亦有较好的异常反应。     

Modelling the effect of evaporation on the salinity-Sr/Sr relationship in modern and ancient marginal-marine systems: the Mediterranean Messinian Salinity Crisis

Palaeosalinity reconstructions in marginal marine environments based on Sr isotope data assume simple two end-member mixing of river and ocean water. An improved model that incorporates the effect of evaporation is used to demonstrate that this approach is not valid in evaporation-dominated systems. However, Sr isotope records combined with faunal and lithological constraints on salinity can be used to assess the palaeohydrological conditions of ancient marginal marine systems. This new method is used to interpret deviations from the global seawater Sr isotope curve, observed in Mediterranean successions during, and up to 3 Myr prior to, Messinian evaporite deposition. Results suggest that no absolute change in the net evaporation flux is required to explain the three- to four-fold rise in salinity of Mediterranean water at the carbonate-evaporite transition. Modelled Sr isotope records indicate that this increase in salinity was synchronous with an increase in the dominance of Atlantic water inflow in the hydrological budget of the Mediterranean. The Messinian Salinity Crisis may therefore have been the response to a marine transgression.     

Cd concentration in the soft tissue vs. the nacreous layer of Mytilus californianus

The soft tissue of Mytilus californianus has the capacity to decrease its Cd concentration in the order of days. However, for medium-term (months) pollution surveys it is necessary to find alternative structures capable of integrating Cd concentrations during longer periods of time. The recently deposited nacreous layer of the shell of M. californianus is proposed as such a structure. Daily variability of Cd concentration in the soft tissue and in the recently deposited nacreous layer of a natural population of mussels was compared during a period of 26 days in organisms collected from an upwelling zone of British Columbia. Statistical analysis of the Cd concentrations indicated that the nacreous layer presented less significant differences between days than the associated soft tissue. Only one shell sample showed significant differences in Cd concentrations, probably related to environmental conditions and stress arising from mussel population density. Experimental results carried out in the laboratory confirmed that the recently deposited nacreous layer of M. californianus is a better medium-term indicator of Cd in seawater, especially at low concentration exposures of this element, those similar to the ones encountered in natural environments.     

The removal rates of234Th and228Th from waters of the New York Bight

The mean residence time (τ) of thorium with respect to non-radioactive removal from water was determined as a function of location in three traverses of the New York Bight using both²³⁴Th/²³⁸U and²²⁸Th/²²⁸Ra. τ correlates well with salinity increasing from about ten days near shore to 70 days at the shelf break. It shows a much weaker correlation with suspended matter concentrations both because suspended matter varies in its scavenging efficiency and because salinity is a longer-term integrator of scavenging potential.τ's computed from²²⁸Th/²²⁸Ra were often higher than those computed from²³⁴Th/²³⁸U either because of the detrital matter present as reflected in the²³²Th concentrations or because the water parcels had recently arrived from environments of lower scavenging efficiency.Anomalous isotopic concentrations found in three adjacent samples can best be explained as the result of an episodic release of²²⁸Ra from bottom sediments at a rate 200 times the normal one.     

应用GPS数据和Slepian基函数反演川云渝地区陆地水储量变化

局部Slepian函数是将局部区域内的地球物理信号转化为空间谱的一种方法,其可以保证在球面上局部范围内获得最优谱平滑解,非常适用于局部范围地球物理信号的研究.本文利用中国陆态网西南地区72 个测站的连续GPS观测资料分析川云渝地区陆地水负荷形变特征,并基于Slepian函数方法解算 60 阶的空间谱基函数,结合弹性质量...