地球化学指标在黄土环境演变研究中的应用进展

中国黄土沉积纪录了最近2．6Ma以来黄土高原及全球自然环境演变的历史。重建其演变历史以预测未来气候环境的变化趋势是指导该地区经济、生态环境建设的重要基础。黄土的地球化学指标是重建该地区环境演变历史的重要途径之一。基于进一步研究的目的,总结了黄土地球化学指标在环境演变研究中的应用和近年来取得的进展。     

成都经济区放射性环境评价分析研究

运用区域1/25万土壤化探数据中铀、钍、钾的含量数据,对成都经济区的放射性水平进行了评价。介绍了放射性核素含量分布情况和环境放射性水平,通过成都经济区地质情况和成都经济区放射性环境分布情况,分析了地质条件对成都经济区环境放射性的影响,并初步研究了地质条件影响放射性水平的原因。最后总结了成都经济区地质环境对天然放射性水平分布情况的影响规律:除龙门山褶皱带和峨眉山-瓦山断块少部分地区外,绝大部分地区γ射线内外照射指数都在国家建筑材料放射性核素限量标准控制式的范围内;地质构造、地表出露岩层和地表水对放射性水平有较大的影响。     

Genetic, abiotic and social influences on sex differentiation in cichlid fishes and the evolution of sequential hermaphroditism

Genetic and environmental factors may interact to control sex determination in fishes. A common pattern of initial female differentiation and subsequent male transformation before maturation in non‐hermaphroditic fishes and after maturation in sequentially hermaphroditic fishes has suggested that changes in developmental timing may be responsible for the evolution of various expressions of sexual lability. Sequential hermaphroditism is rare in freshwater fishes, but investigators report degrees of sexual lability at four distinct life stages in cichlid fishes. Some cichlids undergo genetic sex determination and are not labile. Lability at the larval stage allows temperature or pH to determine sex. Social interactions apparently determine sex at the juvenile stage in the Midas cichlid (Amphilophus citrinellus). Most reports of post‐maturational sex change in cichlids are anecdotal or unsubstantiated. The common occurrence of same‐sex spawning suggests that many species are incapable of sex change. Sequential hermaphroditism is concluded not to be typical, except for the checkerboard cichlid (Crenicara punctulata), which regularly undergoes functional female‐to‐male transformation. Expression of sexual lability at four life stages in one family of fishes corroborates a role for developmental timing in the evolution of sequential hermaphroditism as well as environmentally controlled sex determination. The broad phylogenetic distribution of sexual lability in cichlids indicates that processes capable of producing sex change are generally present. The rarity of sequential hermaphroditism in cichlids and possibly other freshwater fishes is likely due to unpredictability of food and therefore potential mate distributions compared with coral reef habitats.     

土壤碘的环境地球化学迁移研究

应用同位素（125I）示踪技术,在模拟条件下,通过淋溶试验,研究土壤碘的环境地球化学迁移特征及其影响因素.研究表明：土壤碘（125I）的迁移、挥发和被淋溶的数量与土壤质地有关,淋溶液的酸碱度对土壤碘的流失产生明显的影响.这些研究结果为提高作物吸收碘的效率,进而开辟生产化防治IDD的新途径提供重要的科学依据.     

安徽郎溪黄棕色土—红土二元结构土壤剖面的成因与长江流域第四纪晚期古气候演变

安徽宣郎广一带,黄棕色土-红土二元结构地貌十分常见。本文在郎溪选择了一个典型的黄棕色土-红土剖面,进行粒度组成和元素地球化学性状的研究,结果表明:(1)研究剖面上部黄棕色土的粒度组成和元素地球化学特征,与宣城、九江黄棕色土和镇江下蜀黄土十分一致,说明研究区域的黄棕色土确实与长江流域广泛分布的下蜀黄土同源。郎溪剖面粒度和元素地球化学特征的变化较均匀,尤其黄棕色土→埋藏红土(包括均质红土和网纹红土)间呈连续过渡,无沉积间断,表明埋藏红土的物源与黄棕色土和下蜀黄土相似,具典型的风积成因特性。(2)与黄棕色土相比,埋藏红土粒径偏细,风化成土作用显著增强。从埋藏红土逐渐过渡到黄棕色土,反映的可能是长江流域晚更新世初期,末次间冰期结束、末次冰期开始时的一次重大的古气候演变事件,但仍需确凿的年代学证据。     

三峡库区忠县-万州多目标调查土壤地球化学特征分析

通过对＂三峡库区响水滩等7幅1∶5万区域地质多目标调查＂取得的土壤元素进行分析统计,对比国内土壤元素和重庆沿江土壤元素含量数据,结果表明：调查区大多数元素含量处于正常水平,而Cd、Zr元素含量较高,Mo、Br、I偏低;通过对54项元素及指标相关性分析,发现部分元素如Sc-V、Fe-Ga、Nb-Ti、Sr-Na、Br-I、F-Li等元素对具有较强的相关性,而Ag、Au、Hg等较为分散;通过对每个地层的元素含量统计揭示出各种元素在各个地层单元中的分布特征。     

元氏石榴品质与岩土地球化学特征关系研究

从农业地质研究的角度出发,探讨了成土母岩、土壤地球化学元素对元氏县石榴品质的影响.调查研究发现,在元氏县山区,品质好、产量高的石榴主要分布在黑云斜长片麻岩区,其主要原因是黑云斜长片麻岩风化层厚,裂隙发育,P、Sr、Mn、Zn含量高,Cr、Ni含量低,K含量虽低但主要以易被植物吸收的缓效态存在于黑云母中.土壤地球化学背景分析表明,优质石榴分布区与P、Sr、Mn、Zn的富集区吻合性最好,这也验证了元氏石榴优质产区分布和成土母岩黑云斜长片麻岩分布的一致性.     

Heavy metals in European soils: A geostatistical analysis of the FOREGS Geochemical database

This paper presents the results of modeling the distribution of eight critical heavy metals (arsenic, cadmium, chromium, copper, mercury, nickel, lead and zinc) in topsoils using 1588 georeferenced samples from the Forum of European Geological Surveys Geochemical database (26 European countries). The concentrations were mapped using regression-kriging (RK) and accuracy of predictions evaluated using the leave-one-out cross validation method. A large number of auxiliary raster maps (topographic indexes, land cover, geology, vegetation indexes, night lights images and earth quake magnitudes) were used to improve the predictions. These were first converted to 36 principal components and then used to explain spatial distribution of heavy metals. The study revealed that this database is suitable for geostatistical analyses: the predictors explained from 21% (Cr) to 35% (Pb) of variability; the residuals showed spatial autocorrelation. The Principal Component Analysis of the mapped heavy metals revealed that the administrative units (NUTS level3) with highest overall concentrations are: (1) Liege (Arrondissement) (BE), Attiki (GR), Darlington (UK), Coventry (UK), Sunderland (UK), Kozani (GR), Grevena (GR), Hartlepool & Stockton (UK), Huy (BE), Aachen (DE) (As, Cd, Hg and Pb) and (2) central Greece and Liguria region in Italy (Cr, Cu and Ni). The evaluation of the mapping accuracy showed that the RK models for As, Ni and Pb can be considered satisfactory (prediction accuracy 45-52% of total variance), marginally satisfactory for Cr, Cu, Hg and Zn (36-41%), while the model for Cd is unsatisfactorily accurate (30%). The critical elements limiting the mapping accuracy are: (a) the problem of sporadic high values (hot-spots); and (b) relatively coarse resolution of the input maps. Automation of the geostatistical mapping and use of auxiliary spatial layers opens a possibility to develop mapping systems that can automatically update outputs by including new field observations and higher quality auxiliary maps. This approach also demonstrates the benefits of organizing standardized joint European monitoring projects, in comparison to the merging of several national monitoring projects.     

Fertilization effects on organic matter of arable soils in diverse environmental conditions of the Czech Republic

Site specific variables and anthropogenic factors influence composition of soil organic matter (SOM). We evaluated quantity and quality of SOM under different fertilization regimes and site conditions. The study combines data based on repeated measurements obtained from six long-term field experiments, which have been established between 1955 and 1983 at ten locations, resulting in thirteen site and experiment combinations. The experimental sites cover a wide spectrum of pedological and climatic conditions of the Czech Republic. Four basic fertilization regimes were selected: unfertilized plots, mineral-only fertilized plots, plots with application of farmyard manure, and both organic and mineral fertilized plots. The study employs compositional data analysis, principal component analysis, and mixed effect linear models for statistical inference. Under combined organic and mineral fertilization, total soil organic C (SOC) increased by 1?3 g kg^?1. Evidence of possible priming effect was obtained for mineral-only fertilization. Local site conditions were the dominant factor shaping SOM properties. The positive relationship between proportion of clay in soil and decomposition index (DI) was confirmed. In the absence of fertilization, DI was eleven times higher in clay-rich than in clay-poor soil. This effect was moderated by fertilization, decreasing to a seven-fold difference under the full fertilization regime.     

钾素循环及其农业利用

钾素是农作物生长的三大要素之一,钾素缺乏严重影响我国农业生产的发展。贵州喀斯特地区拥有储量丰富的钾矿资源,但至今没有得到有效利用。针对贵州农业生产中钾肥资源短缺的问题,通过对钾元素地球化学循环、土壤矿物钾的存在状态及其释放特点、贵州农业生产中钾素收支状况等方面的分析,提出开发贵州钾矿资源的紧迫性和必要性,通过对比分析含钾矿物的三种利用途径,强调生物法在矿物钾开发中的潜力和应用前景。