Formative pre-Hispanic agricultural soils in northwest Argentina

Our study area is from an early agricultural archaeological site named “El Tolar” (1st to 9th century AD), located in Tafí Valley (Tucumán, northwest Argentina). The objective was to identify geochemical signatures generated by the sustained agrarian use of soils. Chemical and pedological studies were made in different archaeological contexts. Physical and chemical features, such as bulk density, pH, organic and inorganic phosphorus, and available copper, manganese and iron, were taken into account. The results suggested that a buried paleosol identified was contemporary with the occupation of the site. It also showed characteristics clearly related to pre-Hispanic agrarian production. The concentrations of organic phosphorus and iron in agricultural soils probably reflect the use of fertilizers. The application of geoscience techniques allowed us to obtain important information on their behaviour and socio-economic development. This paper constitutes the first pedogeochemical approach to the study of Argentinean pre-Hispanic agricultural soils.     

Chemical Characteristics of Snow-Firn Pack in Altai Mountains and Its Environmental Significance

In order to study the chemical characteristics of snow-firn pack in Altai Mountains and its environmental significance, a 1.5-m deep snow-firn pack was dug in the accumulation zone (3 300 m a.s.l.) of the Kanas Glacier in August 2009. A total of 15 samples were analyzed for major ions. Results show that the concentrations of major ions in the snow-firn pack are NH4+>SO42->Ca2+>NO3-> Na+>Cl->K+>Mg2+. NH4+ is the dominant cation with a medium value of 4.7 ueq·L-1, accounting for 39.8% of the total cations, an...     

瓦里关大气降水的化学特征

利用2007—2009年瓦里关本底台降水化学观测资料,分析了瓦里关降水的pH值、电导率及Cl-、NO-3、SO2-4、NH+4、K+、Na+、Ca2+、Mg2+等离子成分的分布特征。结果表明,瓦里关pH值和电导率的年平均值分别为6.60和21.26μs/cm,2007—2009年呈逐年升高趋势。根据pH值,瓦里关降水以中性降水为主,占总降水的65.13%,其次为碱性降水,酸雨最少。离子浓度大小排序依次为Ca2+SO2-4Na+NH+4Cl-Mg2+NO-3K+,且存在明显的季节变化特征,K+、Na+、Ca2+、Mg2+有相似的来源。瓦里关降水中SO2-4/NO3-的范围为0.35~16.48,平均值为3.07;2007—2009年SO2-4/NO-3值呈逐年下降趋势;SO2-4/NO-3全年存在两个峰值,分别在4月和9—10月。     

湄洲湾海域表层沉积物重金属含量的分布特征及潜在生态风险评价

根据2012年福建湄洲湾海域表层沉积物样品测定的7种重金属（Cr、Co、Ni、Cu、Zn、As、Pb）含量数据,研究重金属在沉积物中的含量和空间分布特征,然后运用主成分分析法分析各重金属的主要来源,最后采用潜在生态危害指数法评价其污染程度和潜在生态危害.结果表明,相对第一类海洋沉积物标准,Cu、Zn、As和Pb含量均未超标,Cr超标21.2%.大部分重金属含量平面分布总体呈现东北往西南递减的趋势,体现陆源输入的影响,As、Zn及Pb在7号站位、Cu在8号站位出现高值区可能更多地联系于研究区域本身的背景特征.Cr、Co、Ni和Zn含量之间相关性显著,且Co、As和Zn含量也两两表现出显著正相关.主成分分析表明岩石的自然风化和侵蚀是Cr、Co、Ni、Cu、Zn和As元素在研究区域表层沉积物的主要来源,Pb可能更多来源于海上交通航运和海水养殖.研究区域综合潜在生态危害为中等生态危害程度.     

Geochemical and isotopic (Sr, U) variations of lake waters in the Ol’khon Region, Siberia, Russia: Origin and paleoenvironmental implications

The geochemical study of springs and lake waters from the Ol’khon Region, Siberia, confirms the strong chemical variability of these water samples, more particularly regarding their salinity. Such variability does not result from a simple mixing process between surface freshwaters and deeper saline waters. The variability, observed at the scale of a few square kilometers, would preferentially result from a secondary concentration processes (evaporation and/or cryogenesis) of lake waters of variable intensity from one lake to another. The U-disequilibria data suggest that the duration of the secondary process is certainly an important parameter to be considered to account for the variable salinity of these lakes. The data indicate that the lakes, however modest in size, could be as old as several ky, confirming therefore that the lake sedimentary deposits could represent relevant paleoenvironmental recorders for the last thousands years.     

Impact of the Eastern Mediterranean Transient on the distribution of anthropogenic CO2 and first estimate of acidification for the Mediterranean Sea

In the Mediterranean Sea the carbon chemistry is poorly known. However, the impact of the regional and large-scale anthropogenic pressures on this fragile environment rapidly modifies the distribution of the carbonate system key properties like C_T (total dissolved inorganic carbon), A_T (total alkalinity), C_ANT (anthropogenic CO₂), and pH. This leads inexorably to the acidification of its waters. In order to improve our knowledge, we first develop interpolation procedures to estimate C_T and A_T from oxygen, salinity, and temperature data using all available data from the EU/MEDAR/MEDATLAS II database. The acceptable levels of precision obtained for these estimates (6.11 ??mol-kg⁻¹ for C_T and 6.08 ??mol kg⁻¹ for A_T) allow us to draw the distribution of C_ANT (with an uncertainty of 6.75 ??mol kg⁻¹) using the Tracer combining Oxygen, inorganic Carbon, and total Alkalinity (TrOCA) approach. The results indicate that: 1) all Mediterranean water bodies are contaminated by anthropogenic carbon; 2) the lowest concentration of C_ANT is 37.5 ??mol kg⁻¹; and 3) the western basin is more contaminated than the Eastern basin. After reconstructing the distribution of key properties (C_T, A_T, C_ANT) for four periods of time (between 1986 and 2001) along a west-east section throughout the whole Mediterranean Sea, we analyze the impact of the Eastern Mediterranean Transient (EMT). Not only has the concentration of C_ANT increased (especially in the intermediate and the bottom layers of the eastern basin, during and after the EMT), but also the distribution of all properties has been considerably perturbed. This is discussed in detail. For the first time, the level of acidification is estimated for the Mediterranean Sea. Our results indicate that for the year 2001 all waters (even the deepest) have been acidified by values ranging from −0.14 to −0.05 pH unit since the beginning of the industrial era, which is clearly higher than elsewhere in the open ocean. Given that the pH of seawater may affect a very large number of chemical and biological processes, our results stress the necessity to develop new programs of research to understand and then predict the evolution of the carbonate system properties in the Mediterranean Sea.     

西藏甲玛矿床硅钙界面对矽卡岩成岩及多金属成矿的影响

西藏甲玛铜多金属矿床为冈底斯成矿带的超大型矿床之一,其矽卡岩型主矿体受林布宗组砂板岩、角岩(硅铝质岩石)和多底沟组大理岩(钙质岩石)的岩性界面所控制。基于岩、矿心地质编录,开展矽卡岩岩石、矿物分带及矽卡岩地球化学、矿物化学研究,探讨硅钙岩性界面对矽卡岩及多金属矿体形成的影响。从顶板至底板由石榴子石矽卡岩、硅灰石石榴子石矽卡岩至硅灰石矽卡岩表现出Si O2、Ca O逐渐增加和Al2O3、Fe2O3+Fe O逐渐减少的趋势,石榴子石矽卡岩、硅灰石矽卡岩的稀土元素和微量元素特征对顶板、底板岩石表现出明显的继承性。靠近顶板的矽卡岩中石榴子石属于钙铝-钙铁过渡系列,由石榴石核部向外环带具有Al含量减少、Fe含量增加的特点;靠近底板矽卡岩相对于靠近顶板具有钙铁榴石比例增加、钙铝榴石比例减少特征,由核部向外围未见明显的环带成分演变特征。矽卡岩是流体与硅铝质、钙质岩石水岩反应的产物,沿硅钙界面流体减压沸腾、地下水混合作用和界面内垂向的流体地球化学障是主要的致矿机制。硅、铝质岩石化学性质、物理性质差异是界面控矿的主要因素,硅钙面复合张性构造带、岩浆热事件增加界面渗透率差异有利于矿体规模的增加和品位提高。     

Petrogenesis,geochronology, and tectonic significance of granitoids in the Tongshan intrusion,Anhui Province,Middle–Lower Yangtze River Valley,eastern China

The Tongshan copper deposit in Anhui Province is a typical mid-sized skarn and porphyry type deposit in the Anqing–Guichi district along the Middle–Lower Yangtze River Valley, eastern China. The Tongshan intrusion is closely related to this mineralization. The intrusion mainly comprises rocks that are quartz diorite porphyry, quartz monzonite porphyry, and granodiorite porphyry. Plagioclase in these rocks is mostly andesine (An = 31.0–42.9), along with minor oligoclase. Biotite is magnesium-rich [Mg/(Mg + Fe) = 0.52–0.67] and aluminum-poor (Al₂O₃ = 12.32–14.09 wt.%), and can be classified as magnesio-biotite. Hornblende is TiO₂-poor (<1.96 wt.%) and magnesium-rich [Mg/(Mg + Fe) > 0.60], and is magnesio-hornblende or edenite. The SHRIMP zircon U–Pb age of the quartz monzonite porphyry is 145.1 ± 1.2 Ma, which corresponds to the middle Yanshanian period. Whole-rock geochemical results show that the rocks are silica-rich (SiO₂ = 60.23–66.23 wt.%) and alkali-rich (K₂O + Na₂O = 4.97–8.72 wt.%), and low in calcium (CaO = 2.61–5.66 wt.%). Trace element results show enrichments in large ion lithophile element (e.g., K, Rb, and Ba) and depletions in some high field strength elements (e.g., Nb, Ta, P, and Ti). The total rare earth element (REE) content of the rocks is low (ΣREE < 200 μg/g), and they exhibit light REE enrichment [(La/Yb)_N > 10] and small positive Eu anomalies (average δEu = 1.16). These mineralogical, geochronological, and geochemical results show that the intrusion has a mixed crust–mantle source. The Tongshan intrusion was formed by multiple emplacements of crustally contaminated basaltic magma generated by varying degrees of partial melting of enriched lithospheric mantle and lower crust. Hornblende thermobarometry yielded magmatic crystallization temperatures of 652–788 °C and an average crystallization pressure of 1.4 kbar, which corresponds to a depth of approx. 4.7 km. Biotite thermobarometry yielded similar temperatures and lower pressures of 735–775 °C and 0.6 kbar (depth 2.1 km), respectively. The parental magma had a high oxygen fugacity and was produced in a volcanic arc setting related to subduction of the paleo-Pacific plate.     

The solute budget of a forest catchment and solute fluxes within a Pinus radiata and a secondary native forest site,southern Chile

Solute concentrations and fluxes in rainfall, throughfall and stemflow in two forest types, and stream flow in a 90 ha catchment in southern Chile (39°44′S, 73°10′W) were measured. Bulk precipitation pH was 6·1 and conductivity was low. Cation concentrations in rainfall were low (0·58 mg Ca²⁺ l^?1, 0·13 mg K⁺ l^?1, 0·11 mg Mg²⁺ l^?1 and <0·08 mg NH₄–N l^?1), except for sodium (1·10 mg l^?1). Unexpected high levels of nitrate deposition in rainfall (mean concentration 0·38 mg NO₃–N l^?1, total flux 6·3 kg NO₃–N ha^?1) were measured. Concentrations of soluble phosphorous in bulk precipitation and stream flow were below detection limits (<0·09 mg l^?1) for all events. Stream‐flow pH was 6·3 and conductivity was 28·3 μs. Stream‐water chemistry was also dominated by sodium (2·70 mg l^?1) followed by Ca, Mg and K (1·31, 0·70 and 0·36 mg l^?1). The solute budget indicated a net loss of 3·8 kg Na⁺ ha^?1 year^?1, 5·4 kg Mg²⁺ ha^?1 year^?1, 1·5 kg Ca²⁺ ha^?1 year^?1 and 0·9 kg K⁺ ha^?1 year^?1, while 4·9 kg NO₃–N ha^?1 year^?1 was retained by the ecosystem. Stream water is not suitable for domestic use owing to high manganese and, especially, iron concentrations. Throughfall and stemflow chemistry at a pine stand (Pinus radiata D. Don) and a native forest site (Siempreverde type), both located within the catchment, were compared. Nitrate fluxes within both forest sites were similar (1·3 kg NO₃–N ha^?1 year^?1 as throughfall). Cation fluxes in net rainfall (throughfall plus stemflow) at the pine stand generally were higher (34·8 kg Na⁺ ha^?1 year^?1, 21·5 kg K⁺ ha^?1 year^?1, 5·1 kg Mg²⁺ ha^?1 year^?1) compared with the secondary native forest site (24·7 kg Na⁺ ha^?1 year^?1, 18·9 kg K⁺ ha^?1 year^?1 and 4·4 kg Mg²⁺ ha^?1 year^?1). However, calcium deposition beneath the native forest stand was higher (15·9 kg Ca²⁺ ha^?1 year^?1) compared with the pine stand (12·6 kg Ca²⁺ ha^?1 year^?1). Copyright © 2002 John Wiley & Sons, Ltd.     

Reflectance spectra and chemical structure of Titan's tholins: Application to the analysis of Cassini-Huygens observations

Titan's tholins are used as analogs of Titan's aerosols and N-rich organic solids present on many icy surfaces. However, it is not clear whether or not they are relevant analogs, and which kind of tholins should be used among a wide set available in literature. This paper presents reflectance spectral data of two tholins selected as end-members of a series of samples covering a very wide range of continuous chemical and optical properties. These samples were formed under experimental conditions fairly consistent with Titan's stratosphere. A general framework for using these laboratory data to the analysis of spectral observation of Titan's surface or other objects is suggested. Furthermore, the study reports the first in situ unambiguous identification of aromatics compounds and evidences variations in the sp² carbon structure, which controls the absorption properties in the visible/NIR. These results also point out it is very unlikely to derive quantitative chemical information (e.g., N content, sp²/sp³ ratio) from remote sensing reflectance data.