Triton: stratospheric molecules and organic sediments

Hydrocarbons and nitriles are produced in Triton's stratosphere by energetic electrons from Neptune's magnetosphere and other charged particle sources. Laboratory plasma experiments reported here show a substantial yield of molecules from low pressure flows of 10(-3) CH4 in N2 appropriate to Triton if both CH4 and N2 are saturated at the surface. An active magnetosphere similar to that of Uranus would result in a flux approximately 0.3 erg cm-2 s-1 of 0.1-1 MeV electrons in Triton's stratosphere; molecular production rates are then 10(6)-10(8) cm-2 s-1 for NH3, C2H2, HCN, and NCCN; tens of hundreds of gm cm-2 of these compounds per 10(9) yr (and lesser quantities of at least eight other molecules experimentally detected) would freeze to fine-grained white condensates in the lower stratosphere and sediment to the surface. Along with dark/colored organic haze produced in the stratosphere and other heteropolymers produced at the surface, these condensates are subjects to redistribution by aeolian processes and may appear as lag deposits and/or sediment layers. A simple eddy diffusion model indicates abundances approximately 10(19) molec cm-2 for HCN and C2H2, and > 10(17) molec cm-2 for NCCN, CH3CCH, CH2CCH2, and CH3CN in the stratosphere; these and other organic molecules will be detectable by IRIS if the stratosphere is (as expected) heated through ultraviolet and visible light absorption by the haze.     

Nutrient fluxes induced by disturbance in Meiliang Bay of Lake Taihu

A wave flume experiment was conducted to study nutrient fluxes at water-sediment interface of Meiliang Bay under different hydrodynamic conditions. The results reveal that hydrodynamics has remarkable effects on nutrient fluxes in this area. With a bottom wave stress of 0.019 N m-2 (equivalent to disturbance caused by wind SE 5-7 m s-1 at the sediment sample site of Meiliang Bay), the fluxes of TN, TDN and NH4+-N were separately 1.92× 10-3, -1.81 × 10-4 and 5.28× 10-4 mg m-2 s-1(positive for upward and negative for downward), but for TP, TDP and SRP, the fluxes were 5.69 × 10-4, 1.68 × 10-4 and -1.29 × 10-4 mgm-2 s-1. In order to calculate the released amount of nutrients based on these results, statistic analysis on the long-term meteorological data was conducted.The result shows that the maximum lasting time for wind SE 5-7 m s-1 in this area is about 15 h in summer. Further calculation shows that 111 t TN, 32 t NH4+-N, 34 t TP and 10 t TDP can be released into water (the sediment area was 47.45% of the whole surface area), resulting in concentration increase of 0.025, 0.007, 0.007 and 0.002 mg L-1 separately. With stronger disturbance (bottom wave stress is 0.217 N m-2 which is equivalent to disturbance caused by wind SE 10-11 m s-1 at the same site), there has been significant increase of nutrient fluxes (1.16× 10-2, 6.76×10-3, 1.14× 10-2 and 2.14× 10-3 mgm-2 s-1 for TN, DTN and NH4+-N and TP). The exceptions were TDP with flux having a decrease (measured to be 9.54× 10-5 mgm-2 s-1 ) and SRP with flux having a small increase (measured to be 5.42 × 10-5 mgm-2 s-1). The same statistic analysis on meteorological data reveal that the maximum lasting time for wind SE 10-11 m s-1 is no more than 5 h. Based on the nutrient fluxes and the wind lasting-time, similar calculations were also made suggesting that 232 t TN, 134.9 t TDN, 228 t NH4+-N, 42.7 t TP, 2.0 t TDP and 1.1 t SRP will be released from sediment at this hydrodynamic condition resulting in the concentration increases of 0.050, 0.029, 0.049, 0.009, 0.0004 and 0.0002 mg L-1. Therefore in shallow lakes, surface disturbance can lead to significant increase of nutrient concentrations although some components in water column had negative flux with weak disturbance (e.g. TDN and SRP in this experiment). In this case, sediment looks to be a source of nutrients. These nutrients deposited in sediment can be carried or released into water with sediment resuspension or changes of environmental conditions at water-sediment interface, which can have great effects on aquatic ecosystem and is also the characteristics of shallow lakes.     

Kyanite far from equilibrium dissolution rate at 0–22℃ and pH of 3.5–7.5

Kyanite is an important and slow-dissolving mineral. Earlier work has measured its dissolution rate at high temperature and acidic pH, but experimental measurements at low temperature and near neutral p H were lacking. The rate equation by Palandri and Kharaka(A compilation of rate parameters of water–mineral interaction kinetics for application to geochemical modeling. US Geological Survey, Open File Report 2004-1068, 2004) indicates that the rate of kyanite dissolution at room temperature and near neutral pH is on the order of 10^-17 mol m^-2 s^-1, orders of magnitudes slower than most common silicate minerals such as albite and quartz. This study used an externallystirred mixed-flow reactor, which allows high solid:solution ratios, to measure the dissolution rate of kyanite at 0–22 ℃ and pH of 3.5–7.5. The measured dissolution rate of kyanite is 4.6–7.6 9 10-13 mol m^-2 s^-1 at 22℃, and the apparent activation energy is 73.5 kJ mol^-1. This dissolution rate is close to the rate of quartz dissolution and four orders of magnitude faster than the prediction by rate equation of Palandri and Kharaka(2004).Based on our new experimental data, we recommend the following rate equation for modeling the dissolution of kyanite at ambient temperatures.r=ke(-Ea)/R(1/T-1/(298.15))where k = 5.08 9 10-13 mol m^-2 s^-1, and Ea= 73.5 kJ mol^-1. Review of literature data(Carroll in The dissolution behavior of corundum, kaolinite, and andalusite: a surface complex reaction model for the dissolution of aluminosilicate minerals in diagenetic and weathering environs. Dissertation, Northwestern University, 1989) led to a recommended rate equation for andalusite as for T = 25℃ and pH = 2–10:r=k1aH+^n1+k2+k3aH^+^n3where k1= 4.04 9 10^-10 mol m^-2 s^-1, k2= 7.95×10^-10 mol m^-2 s^-1, k3= 1.01×10^-17 mol m^-2 s^-1, n1= 1.2 and n3=-0.6.     

Determination of O2(a1 delta g) and O2(b1 sigma+ g) yields in the reaction O + ClO --> Cl + O2: implications for photochemistry in the atmosphere of Venus

A discharge flow apparatus with chemiluminescence detector has been used to study the reaction O + ClO --> Cl + O2, where O2 = O2(a1 delta g) or O2(b1 sigma+ g). The measured quantum yields for producing O2(a1 delta g) and O2(b1 sigma+ g) in the above reaction are less than 2.5 x 10(-2) and equal to (4.4 +/- 1.1) x 10(-4), respectively. The observed O2(a1 delta g) airglow of Venus cannot be explained in the context of standard photochemistry using our experimental results and those reported in recent literature. The possibility of an alternative source of O atoms derived from SO2 photolysis in the mesosphere of Venus is suggested.     

Cloud Point Extraction for the Preconcentration of Silver and Palladium in Real Samples and Determination by Atomic Absorption Spectrometry

A cloud point extraction procedure is presented for the preconcentration and simultaneous determination of Ag⁺ and Pd²⁺ in various samples. After complexation with 2‐((2‐((1H‐benzo[d]imidazole‐2‐yl)methoxy)phenoxy)methyl)‐1H‐benzo[d]imidazol (BIMPI), which was used as a new chelating agent, analyte ions were quantitatively extracted to a phase rich in Triton X‐114 following centrifugation, and determination was carried out by flame atomic absorption spectrometry (FAAS). Under the optimum experimental conditions (i. e., pH = 7.0, 15.0·10^–5 mol/L BIMPI and 0.036% (w/v) Triton X‐114), calibration graphs were linear in the range of 28.0–430.0 μg/L and 57.0–720.0 μg/L with detection limits of 10.0 and 25.0 μg/L for Ag⁺ and Pd²⁺, respectively. The enrichment factors were 35.0 and 28.0 for Ag⁺ and Pd²⁺, respectively. The method has been successfully applied to evaluate these metals in some real samples, including waste water, soil and hydrogenation catalyst samples.     

电离层极风的EISCAT-VHF雷达观测

极风现象从理论上提出已20多年了,实验上一直没有充分地证实这种现象的存在,以及它的形成区域位于高纬顶部电离层中.我们利用欧洲非相干散射协会（EISCAT）的VHF雷达（在挪威Tromsφ）,对H⁺离子极风进行了首次实验研究,结果表明,实验期间观测到H⁺离子在顶部电离层中的运动速度始终向上,且随高度的增加而增大,从而证实在高纬顶部电离层中确实存在着一个永久向上的H⁺离子流,即H⁺离子极风,其速度在1000km 高度上达到1km/s,其通量在此高度上接近于饱和,达到10¹²m^s（-1）,而温度小于0.26eV.在我们的探测高度上仍未发展成超声速极风.     

行星际磁场脉动能谱随日心距离变化的模式

空间飞船Helios 1和Helios 2的磁场探测发现,太阳风高速流中磁场脉动在低频区的能谱的谱指数是随日心距离r而变化的,谱密度的空间梯度是随频率f而变化的,现有关于行星际磁场脉动的理论都不能解释上述现象。本文提出了一个计算行星际磁场能谱径向发展的理论模式。假设在不同频率的脉动之间有由低频向高频传输的能流存在,在这一基础上建立了谱方程,并得到了谱方程的数值解。数值解表明,由0.3AU至1AU,低频区的谱指数增加,而高频区的谱指数近似保持为常数（-1.6）;低频区平均谱密度随着日心距离的变化为r^-3.5,在高频区为r^-4.1,所有这些都与观测相符合。串级的能量很可能最后传输到质子回旋频率范围,由于回旋共振而耗散,最后加热太阳风质子。这一模式有可能用来计算太阳风的加速问题。     

武汉九峰地震台超导重力仪观测分析研究

连续重力观测和GPS的技术结合能够监测到物质迁移和地壳垂直形变之间的量化关系.和相对重力测量以及绝对重力测量技术相比,其避免了时间分辨率和观测精度低,无法精细描述观测周期内的物质迁移过程问题.本文利用武汉九峰地震台超导重力仪SGC053超过13000 h连续重力观测数据;同址观测的绝对重力仪观测结果;气压数据;周边GPS观测结果;GRACE卫星的时变重力场;全球水储量模型等资料,采用同址观测技术、调和分析法、相关分析方法在扣除九峰地震台潮汐、气压、极移和仪器漂移的基础上,利用重力残差时间序列和GPS垂直位移研究物质迁移和地壳垂直形变之间的量化关系.结果表明:在改正连续重力观测数据的潮汐、气压、极移的影响后,不仅准确观测到2009年的夏秋两季由于水负荷引起的约(6~8)×10^-8m·s^-2短期的重力变化.而且在扣除2.18×10^-8(m·s^-2)/a仪器漂移和水负荷的影响后,验证了本地区长短趋势垂直形变和重力变化之间具有一致的负相关性规律.同时长趋势表明该地区地壳处于下沉,重力处于增大过程,增加速率约为1.79×10^-8(m·s^-2)/a.武汉地区重力梯度关系约为-354×10^-8(m·s^-2)/m.     

水对高应变率扭剪变形实验中大理岩强度的影响

利用 Kolsky 扭转棒作为实验装置,笔者在常温常压条件下对干燥的和潮湿的大理岩试样进行了一系列的动态简单剪切的实验变形研究,以期了解在高应变率(373-1-1736-1)时岩石中孔隙水对于岩石抗剪强度的影响.结果表明,孔隙水的存在不但没有降低,反而稍微提高了岩石的抗剪强度.结合前人在静态条件下的实验研究资料,笔者认为水对岩石变形的作用机制随应变率的变化而改变.在低应变率(例如:10-9-1)时,水对岩石变形的影响分别表现为压溶作用、应力侵蚀作用和降低有效应力的效应.压溶作用和应力侵蚀作用导致岩石强度的降低;而有效应力的降低则导致岩石强度的相对提高.      

The diffusive boundary layer of sediments: oxygen microgradients over a microbial mat

Oxygen microelectrodes were used to analyze the distribution of the diffusive boundary layer (DBL) at the sediment-water interface in relation to surface topography and flow velocity. The sediment, collected from saline ponds, was covered by a microbial mat that had high oxygen consumption rate and well-defined surface structure. Diffusion through the DBL constituted an important rate limitation to the oxygen uptake of the sediment. The mean effective DBL thickness decreased from 0.59 to 0.16 mm as the flow velocity of the overlying water was increased from 0.3 to 7.7 cm s-1 (measured 1 cm above the mat). The oxygen uptake rate concurrently increased from 3.9 to 9.4 nmol cm-2 min-1. The effects of surface roughness and topography on the thickness and distribution of the DBL were studied by three-dimensional mapping of the sediment-water interface and the upper DBL boundary at 0.1-mm spatial resolution. The DBL boundary followed mat structures that had characteristic dimensions > 1/2 DBL thickness but the DBL had a dampened relief relative to the mat. The effective surface area of the sediment-water interface and of the upper DBL boundary were 31 and 14% larger, respectively, than a flat plane. Surface topography thereby increased the oxygen flux across the sediment-water interface by 49% relative to a one-dimensional diffusion flux calculated from the vertical oxygen microgradients.     

Copper accumulation by bacteria and transfer to scallop larvae

A bacterial copper-resistant strain was isolated from a hatchery-conditioned adult of the scallop Argopecten purpuratus and was identified as Vibrio sp. according to its physiological characteristics. The lowest concentration of Cu2+ required for its complete inhibition in VNSS medium was 50 microg ml(-1). The Vibrio strain was found to accumulate copper, exhibiting cellular and loosely bound copper levels of 201.14 and 493.21 microg g(-1) dry weight, respectively, after 24 h of incubation in VNSS medium supplemented with 15 microg ml(-1) of Cu2+, with cellular concentration factors of 10.17 and 14.35 after 12 and 24 h of exposure. When a scallop larvae culture was exposed to a concentration of 6.46 x 10(2) CFU ml(-1) of Cu-enriched Vibrio, they accumulated 20.42 +/- 1.12 and 30.96 +/- 1.85 microg Cu2+ g(-1) dry weight after 12 and 24 h, respectively. This study suggests that bacterial copper accumulation could be very active in marine environments increasing the occurrence of copper transfer to marine food chains.     

Methane and nitrous oxide fluxes in the polluted Adyar River and estuary, SE India

We measured dissolved N(2)O, CH(4), O(2), NH(4)(+), NO(3)(-) and NO(2)(-) on 7 transects along the polluted Adyar River-estuary, SE India and estimated N(2)O and CH(4) emissions using a gas exchange relation and a floating chamber. High NO(2)(-) implied some nitrification of a large anthropogenic NH(4)(+) pool. In the lower catchment CH(4) was maximal (6.3+/-4.3 x 10(4)nM), exceeding the ebullition threshold, whereas strong undersaturation of N(2)O and O(2) implied intense denitrification. Emissions fluxes for the whole Adyar system approximately 2.5 x 10(8) g CH(4)yr(-1) and approximately 2.4 x 10(6)gN(2)O yr(-1) estimated with a gas exchange relation and approximately 2 x 10(9) g CH(4)yr(-1) derived with a floating chamber illustrate the importance of CH(4) ebullition. An equivalent CO(2) flux approximately 1-10 x 10(10)gy r(-1) derived using global warming potentials is equivalent to total Chennai motor vehicle CO(2) emissions in one month. Studies such as this may inform more effective waste management and future compliance with international emissions agreements.     

Dependence of reaction rate of pyrite oxidation on temperature, pH and oxidant concentration

Pyrite is a common sulfide mineral, particularly abundant in mining waste. It is a focus of mine envi-ronmental concern because the oxidation of exposed pyrite may lead to acid drainage and poisonous mate-rials (like As and heavy metals) release. In the United States, approximately $1000000 per day is spent in alleviating acid mine drainage[1], while the Canadian mining community has environmental liabilities that exceed $2 billion for disposal, management, and rec-lamation of mine waste[2]. …     

Hydrated cluster ion formation rates and winter anomaly

Expressions for the effective cluster formation rates are written in terms of neutral densities and recent laboratory data on reaction rate coefficients. At D-region heights these parameters show seasonal variations due to mesospheric temperature changes. Reduction in cluster formation rates for winter months would result in a decrease in the concentration of hydrated ions and hence reduced effective recombination coefficient for electrons. The results show latitude and seasonal variations which are similar to that of a normal winter anomaly in radio wave absorption.     

Effects of pelagic food web structure and nutrient concentration on anaerobic methane metabolism in lake sediments

Although anaerobic metabolism in lake sediments is strongly related to organic material from the trophogenic layer, little is known about the role of food web structure in this respect. We tested the influence of planktivorous fish (treatments with or without fish, ±F) and nutrients (treatments with or without fertilization, ±N) on chlorophyll a, zooplankton, sedimentation of particulate organic carbon (POC), and methane accumulation in large enclosures with anoxic hypolimnia (10 m diameter, 8 m deep, 2 × 2 factorial design). Additionally, methane production potential from settled material was estimated in laboratory experiments. In the enclosures, methane accumulation rate increased in the order +F/−N, −F/+N, −F/−N, and +F/+N, while POC sedimentation was similar in all treatments. Settled POC was more efficiently transformed into methane in −F/−N than in +F/−N treatments. However, an opposite effect was observed between −F/+N and +F/+N treatments. In the laboratory, methane production potential was higher when (1) POC content in settled matter increased, and (2) no fish were present. This corresponded well only to field results obtained in −F/−N and +F/−N treatments. The unexpectedly high methane accumulation in the +F/+N treatment was very likely related to abrupt depletion of other electron acceptors in the hypolimnion, which attenuated effects of food web structure. In conclusion, our results indicate that food web structure indirectly affects anaerobic microbial activity primarily due to changes in the decomposition potential of settled organic matter.     

Preservation of extraterrestrial 3He in 480-Ma-old marine limestones.

We have measured the helium abundance and isotopic composition of a suite of Lower Ordovician marine limestones and associated fossil meteorites from Kinnekulle, Sweden. Limestone 3He/4He ratios as high as 11.5 times the atmospheric value in fused samples and up to 23 times atmospheric in a single step-heat fraction indicate the presence of extraterrestrial helium, and demonstrate that at least a fraction of the extraterrestrial 3He carried by interplanetary dust particles must be retained against diffusive and diagenetic losses for up to 480 Ma. The carrier phase has not been identified but is not magnetic. Extrapolation of high-temperature 3He diffusivities in these sediments is consistent with strong retention of extraterrestrial 3He under ambient Earth-surface conditions. Combination of the observed helium concentrations with sedimentation rates estimated from conodont biostratigraphy suggest that the flux of extraterrestrial 3He in the Early Ordovician was about 0.5 x 10(-12) cm3 STP cm-2 ka-1, ignoring potential post-deposition helium loss. This value is indistinguishable from the average 3He flux estimated for the Cenozoic Era. In contrast, previous studies of fossil meteorites, Ir abundances, and Os isotopic ratios in the limestone suggest that the total accretion rate of extraterrestrial material during the studied interval was at least an order of magnitude higher than the Cenozoic average. This disparity may reflect significant post-depositional loss of 3He from IDPs within these old limestones; if so, the match between the Ordovician flux and the Cenozoic average would be fortuitous. Alternatively, the size distribution of infalling objects during the Early Ordovician may have been enriched only in extraterrestrial material too large to retain 3He during atmospheric entry heating (> approximately 30 micrometers). The fossil meteorites themselves also preserve extraterrestrial helium. Meteorite 3He concentrations of 2 to 9 x 10(-12) cm3 STP g-1 are several orders of magnitude lower than found in most modern meteorites, suggesting very substantial helium loss (probably >99.9%) from these chemically altered objects. The Meteorites carry 3He concentrations only a factor of a few higher than the host limestones. The meteorites themselves cannot be the source of the extraterrestrial 3He observed in the limestones.     

铸铁管道胶圈承插接口抗震性能试验研究

铸铁管道是城市供水工程常用的管材,其接口的抗震性能是地震多发地区供水管网设计必须考虑的因素之一。为研究胶圈承插接口的力学性能参数,采用了原型拉拔试验,测定了管道胶圈接口拉拔力与接口变形量,通过试验数据分析,证明了胶圈承插接口具有良好的抗震性能,接头最大允许变形量可达3～4 cm,测定出铸铁管胶圈承插接口单位接触面积弹簧系数值在32～125 N/(cm.cm-2)之间、单位接触面积接头最大抗力为45～75 N/cm2。     

利用面波频散与接收函数联合反演青藏高原东南缘地壳上地幔速度结构

青藏高原东南缘对于青藏高原的隆升、增厚和物质逃逸等问题有着重要的研究价值.本文对研究区内布设的大型流动地震台阵的观测记录进行处理,联合反演面波频散与接收函数数据,获得了地壳厚度、沉积层厚度分布情况以及地壳上地幔高精度S波速度结构.联合反演的结果表明:(1)研究区域内地壳厚度变化很大,从西北往东南方向地壳厚度逐渐变薄;(2)沉积层厚度与研究区内沉积盆地的分布情况较为一致;(3)在研究区中下地壳内由北向南呈条带状分布有两条主要的壳内低速体,其中一条从川西北次级块体向南延伸,穿过丽江断裂到达滇中次级块体下方,另一条低速体沿小江断裂分布,向南延伸到24°N左右,两条低速体在中地壳范围被四川盆地及峨眉山大火成岩省内带下方的高速异常所隔开.     

Geochemical morphology of the North Mid-Atlantic Ridge, 10°–24°N: Trace element-isotope complementarity

The new data presented here from a 10–24°N segment of the North Mid-Atlantic Ridge show that this segment is the most depleted of the 10–70°N ridge section. They also show the existence of: (1) a geochemical gradient from the 14°N anomaly to 17°10′N; (2) a very depleted mantle source (the lowest Sr isotopic ratios found so far in the North Atlantic); and (3) a geochemical limit located at about 17°10′N without any obvious relation with any structural feature. The 15°20′N fracture zone does not show any relationship with respect to this gradient. The basalts located north of 17°10′N have very homogeneous features, which allow their characteristics to be averaged (i.e., ⁸⁷Sr/⁸⁶Sr= 0.70238 ± 0.00004, (Nb/Zr)_N = 0.28 ± 0.1) and they are defined as normal mid-ocean ridge basalts. The basaltic glasses located south of 17°10′N present a wide spectrum of isotopic compositions and extended rare earth element patterns (from depleted to enriched). Despite this, they have a constant K/Nb of 233 ± 9 (1s_M, n = 18) whereas this ratio is 344 ± 29 north of 17°10′N. These observations illustrate the strong coherence of behaviour between K and Nb (Ta) during the petrogenic processes involved in the generation of these mid-ocean ridge basalts and also their fractionation during previous mantle processes. Possible interpretations of mixing processes are discussed and sources at the ridge segment scale are favoured. However, when looking in detail, local heterogeneities are still common and can even be traced back off-axis to 115 my.

Placed in the context of the North Atlantic Ridge from 10° to 70°N, the Sr isotopic ratios reveal the Azores superstructure (23–50°N), whereas the trace element ratios (La/Sm-Nb/Zr) trace the second-order structures (33–40°N, 42–48°N) superimposed on the superstructure. This study illustrates the complementarity of information given by certain well chosen trace element ratios on the one hand and by isotopic ratios on the other. Since there is evidence of decoupling between isotopic ratios and/or trace element ratios, it introduces the notion of complementary “chemical memory” as recorded by a given type of trace element ratio or a given type of isotopic ratio     

Sources of salinity in ground water from Jericho area, Jordan Valley

One of the major problems in the lower Jordan Valley is the increasing salinization (i.e., chloride content) of local ground water. The high levels of salinity limit the utilization of ground water for both domestic and agriculture applications. This joint collaborative study evaluates the sources and mechanisms for salinization in the Jericho area. We employ diagnostic geochemical fingerprinting methods to trace the potential sources of the salinity in (1) the deep confined subaquifer system (K2) of Lower Cenomanian age; (2) the upper subaquifer system (K1) of Upper Cenomanian and Turonian ages; and (3) the shallow aquifer system (Q) of Plio-Pleistocene ages. The chemical composition of the saline ground water from the two Cenomanian subaquifers (K1 and K2) point to a single saline source with Na/Cl approximately 0.5 and Br/Cl approximately 7 x 10(-3). This composition is similar to that of thermal hypersaline spring that are found along the western shore of the Dead Sea (e.g., En Gedi thermal spring). We suggest that the increasing salinity in both K1 and K2 subaquifers is derived from mixing with deep-seated brines that flow through the Rift fault system. The salinization rate depends on the discharge volume of the fresh meteoric water in the Cenomanian Aquifer. In contrast, the chemical composition of ground water from the Plio-Pleistocene Aquifer shows a wide range of Cl- (100-2000 mg/L), Na/Cl (0.4-1.0), Br/Cl (2-6 x 10(-3)), and SO4/Cl (0.01-0.4) ratios. These variations, together with the high SO4(2-), K+, and NO3- concentrations, suggest that the salinity in the shallow aquifer is derived from the combination of (1) upconing of deep brines as reflected by low Na/Cl and high Br/Cl ratios; (2) leaching of salts from the Lisan Formation within the Plio-Pleistocene Aquifer, as suggested by the high SO4(2-) concentrations; and (3) anthropogenic contamination of agriculture return flow and sewage effluents with distinctive high K+ (80 mg/L) and NO3- (80 mg/l) contents and low Br/Cl ratios (2 x 10(-3)). Our data demonstrates that the chemical composition of salinized ground water can be used to delineate the sources of salinity and hence to establish the conceptual model for explaining salinization processes.