喀斯特石漠化区不同优势树种根际土壤有机碳及氮磷的变化

通过对贵州中部喀斯特石漠化区典型植被及土壤进行调查,探讨森林退化过程中不同群落优势树种根际土壤有机碳及氮磷含量的变化。结果表明:根际土壤有机碳及氮磷含量均高于非根际土壤;在不同植被类型之间,林木根际对土壤有机碳及氮磷的累积效应存在明显的差异性,其中土壤有机碳的累积效应表现最明显,其次是土壤磷素,而土壤氮素累积效应的差异性较小。在树木根基0～30cm水平范围内,根际土壤总有机碳、易氧化有机碳、全氮、有效氮和有效磷含量都明显高于30～90cm外围根际区。不同群落优势树种之间,根际土壤碳及氮磷总量的差异性表现为总有机碳＞全氮＞全磷,而碳及氮磷的生物有效态含量则表现为有效磷＞易氧化有机碳＞有效氮。森林退化过程中,群落优势树种根际土壤总有机碳、易氧化有机碳及有效磷含量出现显著的下降,从而明显地影响土壤的肥力水平。      

Nutrient (P, N) dynamics in the southwestern Kattegat, Scandinavia: sedimentation and resuspension effects

 The yearly nutrient supply from land and atmosphere to the study area in SW Kattegat is 10 900 tons of N and 365 tons of P. This is only few percent of the supply from adjacent marine areas, as the yearly transport through the study area is 218 000 tons of N and 18 250 tons of P. Yearly net deposition makes up 1340 tons of N (on average 2.5 g m^–2 yr^–1) and 477 ton of P (on average 0.9 g m^–2 yr^–1). Shallow-water parts of the study area have no net deposition because of frequent (>35% of the year) resuspension. Resuspension frequency in deep water is <1% of the year. Resuspension rates, as averages for the study area, are 10–17 times higher than net deposition rates. Because of resuspension, shallow-water sediments are coarse lag deposits with small amounts of organic matter (1.1%) and nutrients (0.04% N and 0.02% P). Deep-water sediments, in contrast, are fine grained with high levels of organic matter (11.7%) and nutrients (0.43% N and 0.15% P). Laboratory studies showed that resuspension changes the diffusive sediment water fluxes of nutrients, oxygen consumption, and penetration into the sediment. Fluxes of dissolved reactive phosphate from sediment to water after resuspension were negative in organic-rich sediments (13.2% organic matter) with low porosity (56) and close to zero in coarse sediments with a low organic matter content (2.3%) and high porosity (73). Fluxes of inorganic N after resuspension were reduced to 70% and 0–20% in relation to the rates before resuspension, respectively. Received: 10 July 1995 · Accepted: 19 January 1996     

喀斯特石漠化地区土壤Fe组成及其发生学意义

土壤中氧化铁的组成反映了土壤的成土过程和环境条件。通过对西南喀斯特石漠化地区不同石漠化阶段山地自然土壤和农田土壤Fe组成的分析,研究了土壤全铁、游离氧化铁和非晶形氧化铁的分布规律,探讨了喀斯特地区石漠化土壤的发育过程和Fe的指示作用。研究表明:①喀斯特地区土壤表层全铁含量在38.9～53.9g/kg之间,游离氧化铁含量在18.0～26.7g/kg之间,铁游离度在44.1%～73.4%之间,铁活度在7.2%～11.4%之间。②随着石漠化程度的加剧,土壤游离氧化铁和铁游离度呈增加的趋势,而铁活度呈降低的趋势。③在土体分布上,自然土壤剖面随深度的增加,土壤铁游离度和铁活度呈明显降低的趋势,而农田土壤铁游离度呈增加的趋势。④喀斯特地区的土壤是石灰岩溶蚀风化的产物,人为活动干扰下的自然土壤石漠化过程是在水力作用下的表土侵蚀过程,而农田土壤受水分垂直运动的影响,是土壤丢失的过程。     

Impacts of land use and land cover changes upon organic productivity values in Karst ecosystems: a case study of Northwest Guangxi, China

Karst areas are one of the most fragile regions in the world. The Karst environment is very common in southwest China with severe poverty and environmental degradation. Therefore, it is necessary to monitor the Karst ecosystem and its ability to provide goods and services for society. In this paper, we analyzed the spatial distribution of organic productivity values (OPV) in Northwest Guangxi, China in 1985, 1990, 2000, and 2005 using remote sensing and geographic information system techniques. OPV showed a decreasing trend in the last 20 years though there were fluctuations. OPV was 184.85, 117.53, 163.66 and 177.25 million Yuan in 1985, 1990, 2000 and 2005, respectively. Woodland and shrub were the two largest contributors to total OPV. They accounted for 70.51%, 69.13%, 73.92% and 66.23%, respectively, in those four years. Conversely, OPVof residential and barren rock was low with a percentage of 0.70%, 0.56%, 0.57% and 0.90%, respectively. Spatially, OPVis higher in the west than in the east. However, OPV increased in typical Karst areas but decreased in non-Karst areas. Our study indicates that ecosystem conditions in Karst areas had improved because of the application of rocky desertification control policies.     

新疆西南部塔什库尔干地区赞坎铁矿综合信息预测模型及其在区域预测中的应用

赞坎铁矿位于塔什库尔干古元古界陆块中,受古元古界布伦阔勒群中深变质岩系的控制,属沉积变质型铁矿,具有明显的区域高磁和化探异常。在总结赞坎铁矿综合信息预测模型的基础上,利用区域地质、航磁、化探资料,提出了赞坎、苏巴什、提孜那甫找矿靶区,进而圈出了赞坎-苏巴什铁矿成矿带。     

锡和钨:西藏冈底斯带潜在的优势矿种

规模巨大的西藏冈底斯复合岩浆岩带近几年已被公认是我国又一个重要成矿带,拥有铜、铅、锌、金和富铁等优势矿种。除此之外,锡钨应是两个潜在的优势矿种。该带在中、新生代板块活动频繁而强烈,生成有弧花岗岩、碰撞造山花岗岩和后造山花岗岩。碰撞造山花岗岩源于陆壳的局部熔融,具有锡钨成矿专属性。它与弧花岗岩共同集中分布在南、中、北冈底斯3个花岗岩带中,时代以白垩纪至古近纪为主,数量每个岩带均有40个以上的岩体。据岩石学、岩石化学和稀土、微量元素地球化学特征可在每个壳熔花岗岩带中区分出期波下日、桑巴、雅唐那、鲁巴杠、鱼弄、更张等一批成锡花岗岩;据地层岩石的微量元素丰度判定出念青唐古拉岩群、下古生界、中上侏罗统和下白垩统等地层为锡、钨矿源层;加上众所周知的冈底斯带多期构造变动和发育的各种塑、脆性变形形迹,说明冈底斯带确有锡、钨成矿的优越条件。而已有的锡钨矿床、矿(化)点、找矿线索和找矿信息表明,在冈底斯带中确有这两种矿存在,且有进一步普查找矿前景。     

The characteristic and environmental pollution records of phosphorus species in different trophic regions of Taihu Lake, China

Total organic carbon (TOC), Total nitrogen (TN) and the phosphorus species concentrations of sediment cores taken from Zhushan Bay, Meiliang Bay, and East Taihu Lake regions in Taihu Lake, a large shallow lake in China, were determined. Experimental results showed a conspicuous eutrophication trend in the northern area of Taihu Lake. Inorganic P was found to be the main phosphorus form. Fe-bound P accounted for the largest proportion of Inorganic P in Meiliang Bay, an alga-type lake region. In East Taihu Lake, a macrophytic lake region, Ca-bound P was found in higher proportions than in other lake regions, with Organic P present in similarly large proportions. With respect to Taihu Lake sediment cores, the date at approximately 20 cm layer depth was roughly identified as 1950s, while upper 5 cm layers corresponded to the turn of the century. The drastic increase in phosphorus species concentration except for Ca-bound P was indicative of the large quantities of effluent discharge into Zhushan Bay owing to the increased industrial and agricultural production from the 1950s onwards. TN, Inorganic P, Organic P, and total phosphorus (TP) concentrations increased by over 2, 2.5, 2 and 2.5-fold, respectively, over the past five decades. A large proportion of Organic P accounted for TP, and high C/N ratios indicated that East Taihu Lake can be properly classified as an oligotrophic lake.     

Continental/Cordilleran ice interactions: a dominant cause of westward super-elevation of the last glacial maximum continental ice limit in southwestern Alberta, Canada

In southwestern Alberta, Canada, a westward-rising last-glacial-maximum continental ice limit has been identified. This limit is defined by the upper elevation of Canadian Shield erratics deposited by last-glacial-maximum continental ice along the flanks of prominent ridges and buttes within the region. The interpolation between ice-limit data points has produced two distinct slope profiles: 2.9 m/km to the east, and 4.2 m/km to the west of Mokowan Butte. Three hypotheses are proposed to explain this westward rise of the last-glacial-maximum continental ice limit: (1) regional tectonic uplift, (2) glacio-isostatic uplift, and (3) continental ice-flow convergence due to topographic obstacles and interaction with montane ice. Inferred long-term rates of tectonic uplift and glacio-isostatic modelling show that these two mechanisms account for less than 25% of the observed absolute elevation increase of the limit between the Del Bonita uplands and Cloudy Ridge in southwestern Alberta. The remaining rise in elevation of the continental ice-sheet margin in this region is thought to result from continental ice-flow convergence due to the combined effects of the regional topography and interaction with montane glaciers to the west. The steeper rise in the former continental ice surface west of Mokowan Butte can be explained by the topographic obstruction and interaction with montane glaciers in the area of the Rocky Mountain front.     

中国北方草地植物群落碳、氮元素组成空间变化及其与土壤地球化学变化的关系

碳、氮元素是土壤中的关键元素.在我国黄土高原北部-宁夏中东部处于荒漠化初期阶段的草地中,土壤的碳、氮元素组成出现了异乎寻常的特征,即相对于碳含量,氮含量异常偏低.认识造成这一现象的原因对我国北方草地的保护和重建具有重要意义.植被的输入是土壤中碳、氮元素组成的最为重要的控制因素之一.为认识植被碳、氮含量的空间变化对上述现象产生的贡献,对包括草地碳、氮异常区在内的区域进行了沿线植物群落的化学组成研究.结果表明:1.植物群落平均碳含量约为40%～50%,不同植物群落类型碳含量以苦豆子、达乌里胡子枝群落最高(44.225%),蛛丝蓬、骆驼蓬群落最低(35.516%).绝大多数植物群落平均氮含量约为2%～4%,不同植物群落类型含氮量以猪毛菜、星状角果藜群落最高(4.482%),蛛丝蓬群落最低(1.356%);2.植物群落生物量空间分布与对应降雨量变化趋势一致,说明降雨量是限制群落地理分布的关键因子;3.植物群落与土壤C/N比值随纬度呈现不一致的变化规律,相关分析表明,两者呈现统计学上的显著负相关关系,相关系数为:r=-0.392(P＜0.05,n=32).上述结果表明,在研究地区荒漠化初期阶段的草地中,植被输入不是引起该区域土壤C/N异常升高的原因.     

Effects of climate change on relationship between water and salts of waters ecosystems in arid zone, China

The process of salinization has increased dramatically over the past several decades in the northwest arid zone of China. Soil salinization has been recognized as a major environmental problem for many years in the Tarim River Basin. It is the key issue of solving the soil salinization problem to study interaction between water and salt in arid zone, which will provide useful principle and methodology to its solution. Taking Tarim River and Bosten Lake for example, by systematically collecting the basic data of hydrogeology, meteorology, and social economy, we analyzed the interaction of water and salt of Tarim River and Bostan Lake in natural and artificial conditions in aspects of basins, oases, lakes and marshes. The results showed that： （1） Temperature and precipitation are both increasing gradually in the whole Tarim River Basin, the climate tends to be come warmer and wetter, but the water quality condition is not optimistic; （2） At the end of the 1950s, mineralization degree was less than 1.0 g/L from the upper reaches to the lower reaches of the Tarim River. At present, it is more than 3.0 g/L in Alaer Lake （the upper reaches of the Tarim River） except in July, August and October, during which it is less than 1.0 g/L. In Qiala （the lower reaches）, it is more than 1.0 g/L except in March, moreover, it is about 5.0 g/L in July and December. The eco-water conveyance project implementation has still not improved Tarim River＇s water quality condition; （3） Bostan Lake was a tiny salt-water lake in the late 1950s, but the water-soil development of the oasis has aggravated the salinization in recent thirty years. Since the West Pumping Station was brought into operation in 1982, the Bostan Lake which accumulated salt has begun to be desalted. We consider that climate may not be the key factor for salinization in this area. Instead, socio-economic factors relevant to human activities should be mainly responsible for such changes, as is confirmed by our further analysis. In order to improve present situation of water-soil salinization, water resources utilization and management should be strengthened, highly efficient and water-saving irrigating technology should be spread,     

The effect of titanium and phosphorus on ferric/ferrous ratio in silicate melts: an experimental study

The effect of TiO₂ and P₂O₅ on the ferric/ferrous ratio in silicate melts was investigated in model silicate melts at air conditions in the temperature range 1,400–1,550 °C at 1-atm total pressure. The base composition of the anorthite–diopside eutectic composition was modified with 10 wt % Fe₂O₃ and variable amounts of TiO₂ (up to 30 wt %) or P₂O₅ (up to 20 wt %). Some compositions also contained higher SiO₂ concentrations to compare the role of SiO₂, TiO₂, and P₂O₅ on the Fe³⁺/Fe²⁺ ratio. The ferric/ferrous ratio in experimental glasses was analyzed using a wet chemical technique with colorimetric detection of ferrous iron. It is shown that at constant temperature, an increase in SiO₂, TiO₂, and P₂O₅ content results in a decrease in the ferric/ferrous ratio. The effects of TiO₂ and SiO₂ on the Fe³⁺/Fe²⁺ ratio was found to be almost identical. In contrast, adding P₂O₅ was found to decrease ferric/ferrous ratio much more effectively than adding silica. The results were compared with the predictions from the published empirical equations forecasting Fe³⁺/Fe²⁺ ratio. It was demonstrated that the effects of TiO₂ are minor but that the effects of P₂O₅ should be included in models to better describe ferric/ferrous ratio in phosphorus-bearing silicate melts. Based on our observations, the determination of the prevailing fO₂ in magmas from the Fe³⁺/Fe²⁺ ratio in natural glasses using empirical equations published so far is discussed critically.     

西南喀斯特地区石漠化综合治理:成效、问题与对策

西南喀斯特地区石漠化与贫困问题相互交织,是该区域社会经济可持续发展的瓶颈。近二十年来,通过实施植被恢复、水土保持、生态移民等一系列治理措施,石漠化整体扩展的趋势得到初步遏制,由过去持续扩展转变为净减少,西南喀斯特地区生态状况呈良性发展态势,但防治形势仍很严峻,迫切需要寓经济发展于生态治理之中。本文在分析石漠化综合治理成效、存在问题的基础上,探讨了基于民生改善的石漠化防治对策。认为今后应在系统梳理和总结一期治理经验和不足的基础上,进一步加强石漠化演变规律及其关键驱动因子、喀斯特关键带结构与功能变化、植被与水文过程相互作用等基础研究,将植被恢复与生态服务提升、民生改善有机结合,健全“造血”功能,培育和发展与生态治理方向相适应的生态衍生产业,助力扶贫攻坚,实现生态治理与脱贫致富双赢,促进该区域社会经济协同发展及西南生态安全屏障建设。      

Seawater nutrient and carbonate ion concentrations recorded as P/Ca, Ba/Ca, and U/Ca in the deep-sea coral Desmophyllum dianthus

As paleoceanographic archives, deep sea coral skeletons offer the potential for high temporal resolution and precise absolute dating, but have not been fully investigated for geochemical reconstructions of past ocean conditions. Here we assess the utility of skeletal P/Ca, Ba/Ca and U/Ca in the deep sea coral D. dianthus as proxies of dissolved phosphate (remineralized at shallow depths), dissolved barium (trace element with silicate-type distribution) and carbonate ion concentrations, respectively. Measurements of these proxies in globally distributed D. dianthus specimens show clear dependence on corresponding seawater properties. Linear regression fits of mean coral Element/Ca ratios against seawater properties yield the equations: P/Ca_coral (μmol/mol) = (0.6 ± 0.1) P/Ca_sw(μmol/mol) - (23 ± 18), R² = 0.6, n = 16 and Ba/Ca_coral(μmol/mol) = (1.4 ± 0.3) Ba/Ca_sw(μmol/mol) + (0 ± 2), R² = 0.6, n = 17; no significant relationship is observed between the residuals of each regression and seawater temperature, salinity, pressure, pH or carbonate ion concentrations, suggesting that these variables were not significant secondary dependencies of these proxies. Four D. dianthus specimens growing at locations with Ω_arag ? 0.6 displayed markedly depleted P/Ca compared to the regression based on the remaining samples, a behavior attributed to an undersaturation effect. These corals were excluded from the calibration. Coral U/Ca correlates with seawater carbonate ion: U/Ca_coral(μmol/mol) = (−0.016 ± 0.003) (μmol/kg) + (3.2 ± 0.3), R² = 0.6, n = 17. The residuals of the U/Ca calibration are not significantly related to temperature, salinity, or pressure. Scatter about the linear calibration lines is attributed to imperfect spatial-temporal matches between the selected globally distributed specimens and available water column chemical data, and potentially to unresolved additional effects. The uncertainties of these initial proxy calibration regressions predict that dissolved phosphate could be reconstructed to ±0.4 μmol/kg (for 1.3-1.9 μmol/kg phosphate), and dissolved Ba to ±19 nmol/kg (for 41-82 nmol/kg Ba_sw). Carbonate ion concentration derived from U/Ca has an uncertainty of ±31μmol/kg (for ). The effect of microskeletal variability on P/Ca, Ba/Ca, and U/Ca was also assessed, with emphasis on centers of calcification, Fe-Mn phases, and external contaminants. Overall, the results show strong potential for reconstructing aspects of water mass mixing and biogeochemical processes in intermediate and deep waters using fossil deep-sea corals.     

南苏鲁超高压带和高压带边界的准确限定——来自变质岩锆石中矿物包体的证据

南苏鲁地区由 4个岩片组成 ,自西北至东南依次为正片麻岩岩片 (Ⅰ )、表壳岩岩片 (Ⅱ )、含蓝晶石石英岩大理岩岩片 (Ⅲ )和副片麻岩变火山岩片岩岩片 (Ⅳ )。上述构造岩片均经历了强烈的角闪岩相绿片岩相退变质作用的改造。采用激光拉曼、阴极发光和电子探针分析技术 ,对南苏鲁方圆约 380 0km2 范围内 93件锆石样品中的矿物包体进行了系统鉴定。结果表明 ,在第Ⅰ和Ⅱ岩片样品的锆石中均发现以柯石英为代表的超高压 (UHP)矿物包体 ,而在第Ⅲ和Ⅳ岩片锆石中则保存以文石和多硅白云母为代表的高压 (HP)矿物包体。由此推断 ,第Ⅰ和Ⅱ岩片应归属超高压变质带 ,而第Ⅲ和Ⅳ岩片应归属高压变质带。结合变质作用温压条件的研究结果 ,确定超高压岩石峰期变质温压条件为t=72 3～ 85 2℃ ,p≥ 2 .8× 10 3 MPa ;而高压变质岩石峰期变质温压条件为t =5 0 0～ 6 0 0℃ ,p =1.2× 10 3 ～ 2 .5× 10 3 MPa。最新区域填图结果表明 ,南苏鲁东海地区超高压和高压带之间的接触界线为一典型的韧性剪切带。     

Rare Earth Element Patterns in the Karst Terrains of Guizhou Province, China: Implication for Water/Particle Interaction

The authors determine the concentrations of dissolved (<0.22 μm) rare earth elements (REE) and suspended particulate matter (SPM) of typical karst rivers in Guizhou Province, China during the high-flow period. The concentrations of acid-soluble REE extracted from SPM using diluted hydrochloric acid are also obtained to investigate water/particle interaction in the river water. The dissolved REE contents in the river water are extremely low in the rivers of the study. The dissolved REE distribution patterns normalized by the Post Archean Australia Shale (PAAS) in the karst rivers are not flat, show slight enrichment of heavy REE to light REE, and also have significant negative Ce and Eu anomalies. The acid-soluble REE appears to have similar distribution patterns as characterized by MREE enrichment and slight LREE depletion, with unremarkable Ce and Eu anomalies. The PAAS-normalized REE distribution patterns of SPM are flat with negative Eu anomalies. The contents and distribution patterns of REE in the SPM are closely related to the lithological character of the source rocks. The SPM contains almost all the REE produced in the process of surficial weathering. This demonstrates that particle-hosted REE are the most important form of REE occurrence. REE fractionation, which takes place during weathering and transport, leads to an obvious HREE enrichment in the dissolved loads relative to the SPM. Y/Ho ratio can be used to shed light on REE behaviors during water/particle interaction.     

An early Paleoproterozoic high-K intrusive complex in southwestern Tarim Block, NW China: Age, geochemistry, and tectonic implications

Systematic geochronologic, geochemical, and Nd isotopic analyses were carried out for an early Paleoproterozoic high-K intrusive complex exposed in southwestern Tarim, NW China. The results provide a better understanding of the Paleoproterozoic tectonic evolution of the Tarim Block. Zircon U–Pb age dating indicates two Paleoproterozoic magmatic episodes occurring at ca. 2.41 Ga and ca. 2.34 Ga respectively, which were followed by a ca. 1.9 Ga metamorphic event. The 2.41 Ga granodiorite–adamellite suite shares characteristics of late to post-orogenic metaluminous A-type granites in its high alkalinity (Na₂O + K₂O = 7.6–9.3%), total REE (410–788 ppm), Zr (370–660 ppm), and Y (21.7–58.4 ppm) contents. εNd(t) values for the suite range from − 3.22 to − 4.71 and accordingly the Nd modal ages (T_2DM) vary between 3.05 Ga and 3.17 Ga. Based on geochemical data, the 2.34 Ga suite can be subdivided into two sub-suites, namely A-type and S-type. However, both types have comparable Nd isotope compositions (εNd(t) ≈ − 0.41 to − 2.08) and similar narrow T_2DM ranges (2.76–2.91 Ga).Geochemical and Nd isotopic data for the high-K intrusive complex, in conjunction with the regional geological setting, suggest that both the 2.41 Ga suite and the 2.34 Ga A-type sub-suite might have been produced by partial melting of the Archean mafic crust in a continental rift environment. The S-type sub-suite is thought to have formed by partial melting of felsic pelites and/or metagreywackes recycled from Archean crust (TTG?). Gabbro enclaves with positive εNd(t) value (2.15) have been found to be intermingling within the 2.34 Ga suite; ca. 2.34–2.36 Ga gabbroic dykes and adamellites have previously been documented in eastern Tarim. These observations indicate that the high-K intrusions may reflect the emergence of depleted mantle upwelling beneath the Tarim Block at that time. We suggest a three-stages model for the Precambrian crustal evolution in the Tarim Block: (1) the formation of proto-crust (TTG) by ca. 2.5 Ga, (2) episodes of felsic magmatism possibly occurring in continental rift environments at ca. 2.41 Ga and ca. 2.34–2.36 Ga, and (3) ca. 1.9 Ga metamorphism that may represent the solidification of the Precambrian basement of the Tarim Block.     

三江中段两古陆铅同位素地球化学边界的厘定

根据三江中段及周边邻区火成岩铅同位素数据,确认了三江中段扬子陆块与冈瓦纳古陆的边界。两古陆的铅同位素地球化学边界为^206Pb/^204Pb=18．583、^208Pb／^204Pb=38．575和V1=60、V2=52,低于界线值的属扬子陆块,高于界线值的属冈瓦纳古陆。三江中段两古陆的铅同位素地球化学边界在地理上对应于德钦鲁春-红坡牛场一线,以东属扬子陆块,以西为冈瓦纳古陆;在构造上对应于德钦-字呷断裂带;在构造-岩浆带上对应于金沙江构造岩浆带与澜沧江构造岩浆带的分界线;在成矿上则对应于德钦羊拉-鲁春-红坡牛场铜多金属成矿带。     

Dynamics of nutrient elements in three estuaries of North China: The Luanhe, Shuangtaizihe, and Yalujiang

Concentrations of nutrients (NO₃ ^?, NO₂ ^?, NH₄ ⁺, PO₄ ^3?, and dissolved SiO₂) were examined in three North China estuaries—the Luanhe, Shuangtaizihe, and Yalujiang. These riverine-estuarine systems provide distinct geographic and hydrodynamic conditions, that is, a shallow water zone embraced by shoals and sandbars (Luanhe), the confluence of two streams in the upper estuary with different water and sediment loads, and a turbidity maximum in the upper estuarine mixing zone (Yalujiang). Nutrient element concentrations in these rivers are high in comparison with large, less disturbed systems but similar to those from polluted and/or eutrophic European and North American rivers. This is attributed to intensive weathering and erosion and extensive use of chemical fertilizers. In the fresh-marine waters mixing zone, nutrient species can behave either conservatively or nonconservatively, or both. Wherever nonconservative behaviours of nutrient elements are observed, remobilization from solid phases is probably the predominant mechanism. The extrapolation of dilution curves to the fresh water end-members gives estimated riverine concentrations, which can be between two and ten times higher than those from field observations. Taking into account the high N:P ratios (10²–10⁴) from North China rivers and very low concentrations of nitrogen species in the Northwest Pacific coastal oceans (e.g., Yellow Sea), the estuaries in this study may act as regions in which production is limited by phosphorus to regions in which production is limited by nitrogen.     

喀斯特生态系统生物地球化学过程与物质循环研究:重要性、现状与趋势

喀斯特地质与生态系统是地球表层系统中的重要组成部分,其变化将对其他地区以及整个地球系统产生影响.生物地球化学循环是全球和区域变化研究的核心内容,而生态系统的演化与系统内水分和养分的生物地球化学循环密切相关。因此,我们有必要将喀斯特生态系统纳入到更大区域或全球生态系统中进行分析研究,在充分研究认识整个喀斯特生态系统物质生物地球化学循环规律的基础上,进一步研究喀斯特生态系统的全球变化响应或影响机制,为喀斯特生态系统优化调控对策和措施提供科学基础。研究生态系统演化过程中物质的生物地球化学循环规律,是研究植物适生性、物种优化配置和适应性生态系统调控机理的关键基础。在介绍前人工作基础的同时,本文全面而概括地总结了我们近年利用元素、同位素(如δ13C、δ15N、δ34S、87Sr/86Sr)示踪和化学计量学理论和方法对喀斯特生态系统中不同界面和流域中物质的生物地球化学循环及其生态环境效应的研究成果。认识到:喀斯特流域生物地球化学循环活跃,相互耦合,并与流域生态环境变化相互制约;人类活动正干预流域物质的自然生物地球化学循环过程,并导致相应的生态和环境效应;全球变化科学深化有赖于区域生态环境变化及物质生物地球化学循环的研究。这些认识是我们将来系统深入开展喀斯特以及其他流域生态系统物质生物地球化学循环研究的重要方向。     

西南天山二叠纪中酸性侵入岩的地质学和地球化学：岩石成因和构造背景

选择3个典型岩体,即位于西南天山东段的拜城县英买来岩体和位于西段阔克萨岭区的川乌鲁岩体、巴雷公岩体（为了对比,也选择了位于塔里木盆地西北缘的麻扎山岩体）,进行了岩石学和地球化学研究。结果表明,这些岩体具有不同的特点。英买来岩体为黑云母花岗岩和二云母花岗岩,具有高的SiO2含量,弱过铝,高的Sr同位素初始值（约0.710）和负的εNd(t)值（-4～-6）,属于S—A型之间的过渡类型。麻扎山岩体由正长岩组成,属于碱性岩,微量元素标准化图解和其他岩体明显不同的是没有明显的Nb和Ta的负异常。川乌鲁岩体是一个由3个不同期次岩石组成的杂岩体,主体为正长岩-二长岩,地球化学特征显示是由基性岩浆和酸性岩浆不同程度混合形成的。位于同一构造区的巴雷公岩体则与川乌鲁岩体中的花岗斑岩的地球化学特征相似。综合岩石学和地球化学特征推测,南天山东段的英买来岩体是地壳熔融的结果,没有任何地幔物质加入的地球化学信息,西段的阔克萨岭地区酸性岩浆的形成则可能是来自于幔源底侵的基性岩浆导致薄的地壳发生熔融的结果。麻扎山岩体则完全是不同构造背景的产物,有可能与发生在塔里木盆地的二叠纪大规模的岩浆活动有关。因此,二叠纪岩浆活动的性质主要受地壳成分和结构的控制。