Determination of orthophosphate in highly saline waters

Standard methods for the determination of phosphorus as phosphate ion are now well established for fresh and marine waters. In highly saline waters, however, salt effects due to ionic strength, or to particular ions present, may result in method interferences. Three methods of analysis of phosphate based on the formation of phosphomolybdenum blue complexes have been evaluated here for hypersaline waters. Stannous chloride reduction in aqueous media exhibits a substantial salt effect and its use is not recommended. Stannous chloride reduction following extraction into non aqueous solvents shows a significant salt effect (up to 30 per cent) in solutions of salinity >100 g L^–1. Dilution of hypersaline waters to below this salinity may overcome the salt effect but the method suffers from other disadvantages involving resource constraints and health and safety considerations. Ascorbic acid reduction, catalysed by antimony (III) ions, appears to offer the most promise for hypersaline waters. Turbidity in samples having high salinity (> 100 g L^–1) and high phosphorus concentrations (> 500 g P L^–1) changes the spectral characteristics of solutions but linear calibration curves still result for concentrations in the range 400 to 1,000 g P L^–1. The occurrence of turbidity is also affected by the ionic composition of hypersaline waters since solutions made from sea salt give different results to those made from sodium chloride. Dilution of samples, to give salinities less than 100 g L^–1 prior to reduction is recommended to avoid turbidity. The salt effect in these lower salinity waters is less than 3 per cent up to 100 g L^–1.     

银量法测定化学试剂氯化钠中氯化钠纯度的不确定度评定

针对银量法测定化学试剂氯化钠中氯化钠纯度,讨论了氯化钠纯度测定结果的测量不确定度的来源及评定方法,当K=2,氯化钠纯度测定结果的扩展不确定度为(99.70±0.64)%。     

Downstream geomorphic impacts of large dams: the case of Glenbawn Dam,NSW

Downstream hydrologic effects since the closure of Glenbawn Dam, a large dual-purpose storage for water conservation and flood mitigation, include: (i) a reduction in mean annual runoff of about 21 × 10⁶ m³; (ii) a change in the probability distribution of mean daily flows involving a truncation of flows >;8 × 10⁶ m³ d^?1, a much reduced frequency of flows >7 × 10⁵ m³ d^?1 and an increased frequency of flows <7 × 10⁵ m³ d^?1; and (iii) a reduction in flood magnitude of at least 80 per cent for all probabilities of exceedance. From suspended sediment samples collected before and after dam closure, sediment trap efficiency has been estimated at 99 per cent.An accommodation adjustment of the channel has occurred upstream of the first unregulated tributary because the bed is armoured, the banks are well vegetated, some bedrock and concrete controls are present and all regulated releases are incompetent to transport the bed material. Immediately downstream of the first unregulated tributary, the channel has contracted by up to 45 per cent and degraded by up to 69 per cent during lateral migration. Further downstream no channel changes were recorded although the bed material has progressively coarsened over time.     

Glacier mapping in the Cordillera Blanca,Peru, tropical Andes,using Sentinel‐2 and Landsat data

Sentinel‐2 images were used for mapping debris‐free glaciers for the first time in Cordillera Blanca. Landsat‐8 and Sentinel‐2 data were compared for glacier area estimation in 2016, obtaining comparable results. It was observed that normalized difference snow index method for glacier mapping using MSI data is less sensitive to cast shadows and steep terrain compared with Landsat data. Estimated total glacier areas in 1975, 1994, and 2016 were 726 ± 20.3 km², 576.9 ± 15.1 km² and 482.8 ± 7.4 km², respectively. Glacier area in 2016 using Landsat was slightly lower (475.7 ± 16.8 km²) compared to the area estimated using MSI data. Observed glacier shrinkage between 1975 and 2016 was 33.5 per cent, which is lower compared to observed glacier area loss in the eastern cordilleras of Peru. Glacier shrinkage was higher at northern and northeastern slopes (47.9 per cent and 48.1 per cent, respectively) compared to the south‐western slopes (11.1 per cent).     

The salinity of hypersaline brines: Concepts and misconceptions

Some widespread misconceptions about salinity are pointed out, explained and commented on. Definitions, units, and methods of salinity determination recommended for brines of moderate salinities may become unsuitable for highly saline brines. Various salinity units are examined and commented on, and density at a precisely monitored temperature is chosen as the preferable “substitute parameter” for salinity determination of hypersaline brines. It is shown that ambient air density during pycnometric measurements must be known as accurately as required of the brine's density, and that its value must be added to the direct pycnometric measurement. Variations of atmospheric pressure at the time of pycnometry must be taken into account if greater than 15 mB. For a salinity accuracy of ±0.02 per mille, as required for some physical and chemical studies, the temperature of the sample during salinity measurement must be monitored with an accuracy of at least 0.04°C. A definite curve in the ρ-S plane, corresponding to the conversion of salinity to density at a fixed temperature, andvice-versa, does not exist if the brine is saturated in one of its salts. Non-linearity in the equation of state is shown to affect the surface level drop due to evaporation; the effect is negligible at low salinities, but a 10 per cent correction is already required at the salinity found in the northern Red Sea (41 per mille). Reliable reference points for the conversion of absolute salinity to density of highly saline brines are not known, at present, as accurately as desirable; pending the accurate determination of such reference points, a substantial dilution of hypersaline brines (for the purpose of adapting them to conductivity measurements) would multiply the error range by more than a hundred fold. On the other hand, a minute dilution of hypersaline brine samples to prevent salt crystal formation is possible and would not bring about any major increase of the error range in their density (salinity) determination.     

钾肥生产中副产尾盐梯级利用试验研究

柴达木盆地是我国重要的钾肥基地,年产氯化钾超过700×10~4t,副产尾盐超过1 000×10~4t,尾盐的主要组分是氯化钠,并夹带少量的氯化钾。通过精制试验研究,进一步回收氯化钾,氯化钠则作为纯碱原料,实现了尾盐的梯级综合利用,对促进盐湖循环经济发展具有重要意义。试验表明,采用二段洗涤工艺,结合喷淋和搅拌两种洗涤方式处理钾肥生产浮选尾盐,浮选尾盐经二段洗涤所得产品中氯化钠含量达到92.54%,符合纯碱所需原盐指标要求;母液中的氯化钾富集到一定程度后,回收可作为钾肥生产原料。     

湘澧盐矿卤水50 ℃等温蒸发析盐规律研究

湘澧盐矿区位于江陵凹陷南缘,该地区卤水中溴和钾的含量都达到了工业品位。对采集的湘澧盐矿卤水样品进行了化学全分析,并对分析的结果进行了研究,查明了卤水中钾和溴等元素的富集机理;提出关于卤水综合利用的工艺路线及可行性建议。等温蒸发实验表明,整个蒸发过程中均有石盐析出,失水量达到31.23%时,芒硝开始析出;此后,石盐和芒硝共同析出。整个蒸发过程中该卤水的析盐规律为,首先析出氯化钠,再析出硫酸钠,最后析出硫酸钾。     

Eolian transport of salts—A case study in the area of Lake Ebinur (Xinjiang, Northwest China)

In the Ebinur region of Western Dzungaria, strong wind flows from Dzungarian Gate predetermine the widespread development of deflation processes. As a result of human-induced desiccation of Lake Ebinur, a new source of the loose material—the dry lakebed—has formed, which has intensified dust storms in this region. Annual dynamics of the frequency and intensity of dust storms and the amount and chemical composition of salts in the eolian material deposited in the area have been studied. The frequency of dust storms and the intensity of dust and salt deposition regularly decrease with an increase in the distance from the dry lake bottom (playa). The amount of dust deposition ranges from 600 (near the lake) to 70 (100–200 km from the lake) g/m²/a. The amount of salts precipitating with dust is mainly from 14 to 27 g/m²/a; the maximum registered amount of salt deposition is 77 g/m²/a. As shown in our study, the farther from the lake, the higher the portion of sulfate and calcium and the smaller the portion of chloride and sodium ions in the composition of salts.     

Mixed-oxide and perovskite-structure model mantles from 700–1200 km

Summary. The mantle between 700 and 1200 km is modelled using mixed oxides (MgO + FeO + SiO₂ (stishovite)) having olivine, pyroxene, and peridotite (67 per cent ol-33 per cent px) stoichiometries and third-order finite strain theory. It is possible to satisfy the densities, compressional and shear velocities, and bulk and shear moduli of seismic models B1 and PEM and to obtain adiabatic temperature profiles consistent with literature profiles with olivine and peridotite stoichiometries, but not with pyroxenes. Estimates of K and μ for stishovite satisfying Bl and PEM profiles indicate that the stishovite data of Mizutani, Hamano & Akimoto and Liebermann, Ringwood & Major are inconsistent with the assumed mixed-oxide assemblages, even with a large range of pressure and temperature derivatives for K and μ. Assuming perovskite structure materials below 700 km shows that pyroxenes transformed to the perovskite structure are too dense by 1–2.5 per cent. Taking a wide range of P and T derivatives for the K and μ of MgSiO₃ (perovskite) indicates that the seismic models can be satisfied with olivines and peridotites transformed to perovskites and oxides. The MgSiO₃ (perovskite) K and μ estimates bracket the systematics estimates of Liebermann, Jones & Ring-wood. We find only marginal evidence for relaxation of the shear modulus. The mean atomic weight calculated for the mixed-oxide models agrees with the results of Watt, Shankland & Mao for the same region and with previous estimates for the upper mantle. Thus, an increase in iron content below 700 km appears unlikely. This result and the corresponding temperatures (lower than the Clark & Ringwood conduction geotherm) are consistent with convection below 700 km.     

The measurement of reactive silicate in saline-hypersaline lakes: examples of the problem

The analysis of reactive silicate or H₄SiO₄ in saline lake waters using the silicomolybdic acid method developed by Mullin and Riley (1955) suffers from a rather severe salt interference. Our data show that the interference occurs in waters where both chloride and sulfate are the major anions. The interference leads to lower than actual values (by as much as 50 per cent). Until the chemical mechanism of the interference is quantitatively understood, dilution with deionized water appears to be the best approach to obtaining reliable data. This may limit the technique's usage in waters of high TDS, and low reactive silicate.     

中图分类号：O642.3 文献标识码：A 文章编号：

不同形态硼酸盐焓、熵、吉布斯自由能等热力学参数极为缺乏,其准确测定对丰富和发展盐湖硼酸盐化学理论至关重要。本文采用TAM IV微量热计测定了五水合五硼酸钠(NaB₅O₈.5H₂O)溶解热。根据设计的热化学循环,结合Pitzer电解质模型和热力学基本公式,首次获得了NaB₅O₈.5H₂O在298.15 K下标准生成焓(, -5189.4820 kJ×mol^_-1)、标准生成熵(, 4380.4771 kJ×mol^_-1)、标准生成吉布斯自由能(, 4380.4771 kJ×mol^_-1)等热力学参数。这些尚未见报道的热力学参数对丰富无机盐热力学数据和促进盐湖资源综合利用具有重要的科学价值。     

基于地统计学和GIS技术的呼伦湖溶解氧的空间变异特征分析

呼伦湖是内蒙古第一大湖,在草原生态环境保护中举足轻重。在气候变化和人类活动的影响下,呼伦湖的水环境状况不容乐观。为了掌握呼伦湖水体的水质状况,在实地采样的基础上,基于地统计学半方差函数理论和GIS克立格空间插值方法,定量分析了呼伦湖水体溶解氧含量的空间变异特征及分布格局。结果表明：溶解氧的半方差拟合最优模型为球面模型,该水质参数具有强烈的空间自相关性;空间分布上,结合地表水环境质量标准,呼伦湖大部分水域的水质为IV类;考虑到鱼类等水生生物的生存需要,呼伦湖整体的溶解氧状况基本适合鱼类的生长,其中比较适合的区域分布在湖中部。     

The analysis of nitrate in highly saline waters

The analysis of nitrate in seawater and hypersaline waters should take account of a significant “salt effect”. Procedures developed for fresh water and marine waters must be applied cautiously to highly saline waters. The most widely used standard method for the determination of nitrate-nitrogen (NO₃-N) in fresh and marine waters involves the quantitative reduction of nitrate by the Cd column technique followed by colorimetric procedures. In our study, three approaches to estimate NO₃-N in highly saline waters were examined. The first involved dilution. This approach overcame the salt effect but dilution limited the detection of low concentrations of nitrate in highly saline waters. The second involved the use of standard nitrate solutions in saline water. This method is not recommended because of nitrate impurities in AR grade salts. The third- and preferred approach-involved the use of standard additions. “Spikes” of a known volume of NO₃-N standard solution were added to natural saline waters. Nitrate values estimated by the stadard addition method were used to calculate an equation for salt error correction at different salinities applicable to waters with the same relative ionic composition as seawater. This could then be used to correct nitrate determinations in highly saline waters where standards made in distilled water were used for calibration. Many previously published data for NO₃-N in saline water used methods of analysis which do not take account of salt error and are therefore probably in error.     

Estimate of the stress field in Kilauea's South Flank, Hawaii

We estimated stress and seismic strain tensors for the Kilauea volcano's south flank. the stress orientation inversion and the seismic strain calculation were performed using fault-plane solutions. the principal stress and seismic strain directions are approximately uniformly distributed in space and time during the interval covered by the data. However, the σ1, σ3 plane is approximately orthogonal to the 1, 3 plane. Therefore, a weak layer may exist beneath the south flank. σ1 has a plunge of 59° and an azimuth of 152°, with a 10° 95 per cent confidence range. We also developed a stress magnitude inversion to estimate magnitudes of boundary and interior stresses. In this inversion, the principal stress directions were taken as constraints in the seismic volume, and surface geodetic observations were used as data. the maximum magmatic pressure in Kilauea's rift zone is about 160 MPa. the direction of σ1 can be interpreted as the superposition of hydrostatic stress ( pgh ) and magmatic pressure. Without the constraint imposed by the direction of σ1, the estimated pressure is only 60MPa, the distribution of magmatic pressure may be similar to that of pgh . In contrast, the upper rift zone may be in tension. the shear stress in the rift zone is about one order of magnitude smaller than the maximum compressive stress, supporting the interpretation of magmatic flow as fluid in dikes or channels. the combination of stress orientation inversion, seismic strain calculation, and stress magnitude inversion performed in this study provides a means by which to estimate the stress state in seismic areas.     

Hydrobiology of a salt pan from the Peninsula of Baja California, Mexico

The study site, a salt pan in the northwest of Baja California, Mexico,has a surface area of 33.2 ha and water capacity of 216,072m³. It is intermittently isolated from the adjacent ocean by asand bar, so that flooding via the coastal plain is a low frequency eventassociated with extreme storm conditions. Temporal changes in water volumewere represented by a particular expression of the mass conservationequation having as variables the volumetric capacity of the system, waterinputs by pluvial precipitation, runoff and infiltration, and water loss byevaporation; the numerical model explained over 80 per cent of observedfluctuations. The hydrobiological study covered a three-year period and twohydrological cycles; the first one was of mixed marine and pluvial origin,and the second, continental. Throughout the first cycle, phosphate andnitrate concentrations were up to one order of magnitude higher as weretotal particulate protein, chlorophyll a and phytoplankton abundance. Ingeneral, nannoplankton abundance was up to three orders of magnitude greaterthan the microphlanktonic fraction. In the former, 29 different cell formswere observed; two halophytic bacteria constituted 60–80 per cent ofthat fraction. In the microplankton, there were 27 different forms; mostwere benthic diatoms. The zooplanktonic assemblages of the first cycle hadmarine and continental elements; at 141 per mille, Artemia sp. firstappeared; at 240 per mille, it was the only faunistic element in the system.During the second cycle, Artemia was always present, co-existing with othercontinental species up to a salinity of 99 per mille. The morphology andmorphometry of Artemia were similar to those of Artemia franciscana.     

A model for underpressure development in a glacial valley,an example from Adventdalen,Svalbard

The underpressure observed in the glacial valley Adventdalen at Svalbard is studied numerically with a basin model and analytically with a compartment model. The pressure equation used in the basin model, which accounts for underpressure generation, is derived from mass conservation of pore fluid and solid, in addition to constitutive equations. The compartment model is derived as a similar pressure equation, which is based on a simplified representation of the basin geometry. It is used to derive analytical expressions for the underpressure (overpressure) from a series of unloading (loading) intervals. The compartment model gives a characteristic time for underpressure generation of each interval, which tells when the pressure state is transient or stationary. The transient pressure is linear in time for short‐time spans compared to the characteristic time, and then it is proportional to the weight removed from the surface. We compare different contributions to the underpressure generation and find that porosity rebound from unloading is more important than the decompression of the pore fluid during unloading and the thermal contraction of the pore fluid during cooling of the subsurface. Our modelling shows that the unloading from the last deglaciation can explain the present day underpressure. The basin model simulates the subsurface pressure resulting from erosion and unloading in addition to the fluid flow driven by the topography. Basin modelling indicates that the mountains surrounding the valley are more important for the topographic‐driven flow in the aquifer than the recharging in the neighbour valley. The compartment model turns out to be useful to estimate the orders of magnitude for system properties like seal and aquifer permeabilities and decompaction coefficients, despite its geometric simplicity. We estimate that the DeGeerdalen aquifer cannot have a permeability that is higher than 1 · 10^?18 m², as otherwise, the fluid flow in the aquifer becomes dominated by topographic‐driven flow. The upper value for the seal permeability is estimated to be 1 · 10^?20 m², as higher values preclude the generation and preservation of underpressure. The porosity rebound is estimated to be <0.1% during the last deglaciation using a decompaction coefficient α_r = 1 · 10^?9 Pa^?1.     

Split-step complex Padé-Fourier depth migration

We present a split-step complex Padé-Fourier migration method based on the one-way wave equation. The downward-continuation operator is split into two downward-continuation operators: one operator is a phase-shift operator and the other operator is a finite-difference operator. A complex treatment of the propagation operator is applied to mitigate inaccuracies and instabilities due to evanescent waves. It produces high-quality images of complex structures with fewer numerical artefacts than those obtained using a real approximation of a square-root operator in the one-way wave equation. Tests on zero-offset data from the SEG/EAGE salt data show that the method improves the image quality at the cost of an additional 10 per cent computational time compared to the conventional Fourier finite-difference method.     

Baptiste Lake,Alberta — A late Holocene history of changes in a lake and its catchment in the southern Boreal forest

Lead-210 assay and dating are subject to several sources of error, including natural variation, the statistical nature of measuring radioactivity, and estimation of the supported fraction. These measurable errors are considered in calculating confidence intervals for ²¹⁰Pb dates. Several sources of error, including the effect of blunders or misapplication of the mathematical model, are not included in the quantitative analysis. First-order error analysis and Monte Carlo simulation (of cores from Florida PIRLA lakes) are used as independent estimates of dating uncertainty. CRS-model dates average less than 1% older than Monte Carlo median dates, but the difference increases non-linearly with age to a maximum of 11% at 160 years. First-order errors increase exponentially with calculated CRS-model dates, with the largest 95% confidence interval in the bottommost datable section being 155±90 years, and the smallest being 128±8 years. Monte Carlo intervals also increase exponentially with age, but the largest 95% occurrence interval is 152±44 years. Confidence intervals calculated by first-order methods and ranges of Monte Carlo dates agree fairly well until the ²¹⁰Pb date is about 130 years old. Older dates are unreliable because of this divergence. Ninety-five per cent confidence intervals range from about 1–2 years at 10 years of age, 10–20 at 100 years, and 8–90 at 150 years old.This is the third of a series of papers to be published by this journal which is a contribution of the Paleoecological Investigation of Recent Lake Acidification (PIRLA) project. Drs. D.F. Charles and D.R. Whitehead are guest editors for this series.     

Littoral benthos of the saline crater lakes of the basin of Oriental, Mexico

Two saline crater lakes in the basin of Oriental, Puebla-Tlaxcala-Veracruz, were investigated for littoral benthic macroinvertebrates. Fifty taxa were identified with the oligochaetes, amphipods, chironomids and leeches the dominant organisms. These four taxa made up to 99 per cent in both number and biomass.Limnodrilus hoffmeisteri, Hyalella azteca, Tanypus (Apelopia) sp. andStictochironomus sp. were the most abundant organisms. Unlike other saline lakes which have a littoral benthos dominated by chironomids, Alchichica and Atexcac were dominated by oligochaetes (70–73 per cent). The gastropod,Physa sp., was found up to a salinity of 8 g L⁻¹; in other studies, it has been found in lower salinities.L. hoffmeisteri is also a typical inhabitant of freshwater lakes, particularly of deep waters. It was dominant in the shallow, saline waters of the two lakes studied. Salinity did not affect species richness. Alchichica, the most saline of the six crater lakes of Puebla (salinity, 7.4 g L⁻¹), had 30 per cent more species than the freshwater lakes, and double the species number of Atexcac. It seems the main factor controlling species richness and the density and biomass of organisms in Alchichica and Atexcac is the presence of aquatic vegetation. It does this by increasing habitat heterogeneity and providing food and protection against predators.     

Time series assessment on landslide occurrences in an area undergoing development

This study assesses the influence of development on landslide occurrences in a rapidly developing area, Kota Kinabalu in Sabah Malaysia, across three assessment years (1978, 1994 and 2010). Two development indicators, land use and road density, were used to measure the influence of development on landslide occurrence. Land use was classified into four categories (barren, forest, developed and other), and road density was classified into low (< 50 m/40 000 m²), moderate (50–150 m/40 000 m²) and high (> 150 m/40 000 m²). Landslide density analysis was used to calculate the concentration of landslide for the different land use and road density categories. The number of landslides in developed areas increased from 19 landslides/100 km² in 1978, to 29 landslides/100 km² in 1994 and to 50 landslides/100 km² in 2010, mirroring an increase in land use for development purposes from 8 per cent in 1978 to 27 per cent in 2010. Landslide density also gradually increased in the high road density class from 10 landslides/100 km² in 1978, to 30 landslides/100 km² in 1994 and 62 landslides/100 km² in 2010. These results show that road construction activities influence landslide occurrences.