DESIGN FOR A STABLE CHANNEL IN COARSE ALLUVIUM FOR RIPARIAN ZONE RESTORATION1

Geomorphic, hydraulic and hydrologic principles are applied in the design of a stable stream channel for a badly disturbed portion of Badger Creek, Colorado, and its associated riparian and meadow complexes. The objective is to shorten the period of time required for a channel in coarse alluvium to recover from an impacted morphologic state to a regime condition representative of current watershed conditions. Channel geometry measurements describe the stream channel and the normal bankfull stage in relatively stable reaches. Critical shear stress equations were used to design a stable channel in noncohesive materials with dimensions which approximate those of less disturbed reaches. Gabion controls, spaced at approximately 300 m intervals, are recommended to help reduce the chance of lateral migration of the newly constructed channel. Controls are designed to allow for some vertical adjustment of the channel bed following increased bank stability due to revegetation. The flood plain is designed to dissipate flood flow energy and discourage multiple flood channels. The channel has approximately a 90 percent chance of remaining stable the first two years following construction, the time estimated for increased stability to occur due to revegetation.     

Hydrogen, carbon and sulphur isotope ratios in peat: the role of diagenessis and water regimes in reconstruction of past climates

We demonstrate that carbon, hydrogen and sulphur isotope ratios both, in the total peat (¹³C_tp=–25.52 to –28.27, D_tp=–78.67 and –109.24, ³⁴S=4.35 to 19.87), and in cellulose from the peat (¹³C_nc=–25.06 to –27.33 and D_nc=–92.43 to –118.02) are not affected by postdepositional changes. Therefore, the original isotope composition of plants are in general preserved in the peat and represent an archive of the past environmental variations. These can be supported by (i) good correlations between ¹³C_tp and ¹³C_nc, and between D_tp and D_nc, (ii) high horizontal homogeneity of ¹³C_tp and ¹³C_nc in the scale of one peat-bog – the same major factor(s) control(s) C isotopic ratios, (iii) no correlation between organic sulphur concentrations and ³⁴S value –³⁴S results from variations in the water level.This revised version was published online January 2005 with corrections to the title.     

The emergence of stable isotopes in environmental and forensic geochemistry studies: a review

In the past decade, environmental forensics has emerged as a discipline directed toward determining parties liable for causing spills of contaminants into the environment. Such investigations, while geared toward determining the guilty parties in order to recover costs of the cleanup and remediation, require various questions to be addressed. These include determination of the nature of the product; Where did it come from?; Extent of weathering, if any; How long has it been there?; and Is it degrading naturally? Traditionally, these studies have been addressed through utilization of techniques such as gas chromatography (GC) and gas chromatography–mass spectrometry (GCMS). However, in recent years, stable isotopes, primarily determined through the use of combined gas chromatography–isotope ratio mass spectrometry (GCIRMS), have emerged as an equally important tool in environmental forensics. For relatively low molecular, volatile compounds such as MTBE, BTEX, or chlorinated solvents, the isotopes, primarily carbon and hydrogen, have been used extensively for evaluating the onset of natural attenuation. For larger molecules such as PCBs or PAHs, in which the effects of biodegradation on the isotope composition of these molecules is minimal, the isotopic fingerprints of the individual compounds can be used for correlation purposes. In this paper, a brief introduction to isotope geochemistry will be given, followed by a review of applications of stable isotopes to a variety of environmental problems. While the review may not necessarily be exhaustive, it will provide a comprehensive overview of areas where isotopes have been used and potential applications for the future. Most of the review is concerned with carbon and hydrogen isotopes, although a brief overview of the emerging area of chlorine isotopes will also be discussed.     

陕北黄土高原239+240Pu大气湿沉降历史重建

重建Pu同位素的大气沉降历史是开展Pu示踪应用以及核事故安全评价的重要基础。本研究根据东京年降水量和^239+240Pu年大气沉降数据,并结合经验模型对陕北黄土高原^239+240Pu年湿沉降通量进行初探。结果表明,1957~2005年间研究区^239+240Pu年湿沉降通量在0.000 2~4.116 7 Bq/m²之间,累计湿沉降通量为14.08 Bq/m²;通过与周边土壤剖面的Pu总量对比发现陕北黄土高原Pu同位素的干湿沉降比为1左右。在时间变化上,上世纪60年代初全球大规模核试验导致研究区1963年^239+240Pu湿沉降通量出现峰值,1964~2000年Pu湿沉降通量呈明显减小趋势,2001~2005年亚洲粉尘的地表再悬浮过程使得^239+240Pu年湿沉降通量有所增加。     

Geochronology and geochemistry of eclogites from the Mariánské Lázne Complex, Czech Republic: Implications for Variscan orogenesis

The Mariánské Lázn complex (MLC) is located in the Bohemian Massif along the north-western margin of the Teplá-Barrandian microplate and consists of metagabbro, amphibolite and eclogite, with subordinate amounts of serpentinite, felsic gneiss and calcsilicate rocks. The MLC is interpreted as a metaophiolite complex that marks the suture zone between the Saxothuringian rocks to the north-west and the Teplá-Barrandian microplate to the south-east. Sm-Nd geochronology of garnet-omphacite pairs from two eclogite samples yields ages of 377±7, and 367±4 Ma. Samples of eclogite and amphibolite do not define a whole rock Sm-Nd isochron, even though there is a large range in Sm/Nd ratio, implying that the suite of samples may not be cogenetic. Eclogites do not have correlated _Nd values and initial ⁸⁷Sr/⁸⁶Sr ratios. Five of the eight eclogite samples have high _Nd values (+10.2 to +7.1) consistent with derivation from a MORB-like source, but variable ⁸⁷Sr/⁸⁶Sr ratios (0.7033 to 0.7059) which probably reflect hydrothermal seawater alteration. Three other eclogite samples have lower _Nd values (+ 5.4 to –0.8) and widely variable ⁸⁷Sr/⁸⁶Sr ratios (0.7033 to 0.7096). Such low _Nd values are inconsistent with derivation from a MORB, source and may reflect a subduction or oceanic island basalt component in their source. The MLC is an important petrotectonic element in the Bohemian Massif, providing evidence for Cambro-Ordovician formation of oceanic crust and interaction with seawater, Late Devonian (Frasnian-Famennian) high- and medium-pressure metamorphism related to closure of a Saxothuringian ocean basin, Early Carboniferous (Viséan) thrusting of the Teplá terrane over Saxothuringian rocks and Late Viséan extension.     

岩溶流域地表水和地下水硝酸盐来源定量识别

选取岩溶地区花溪河流域典型农业区为研究对象,运用δ¹⁵N-NO₃^-,δ¹⁸O-NO₃^-和δ¹⁸O-H₂O同位素示踪技术和水化学分析方法,阐明了研究区地表水和地下水中硝酸盐的分布特征,并揭示其来源和形成过程,基于R语言下运行的贝叶斯模型（stable isotope analysis in R）,对研究区水体中各种硝酸盐来源的贡献比例进行了定量识别.结果显示：受碳酸岩盐风化的控制,流域内地表水和地下水的水化学类型以HCO₃-Ca型为主,硝酸盐在研究区水体中的空间分布特征受土地利用类型影响明显;在研究区水体硝酸盐形成过程中,硝化作用起主导作用,水体中的硝酸盐来源主要有化肥、降雨中的氨盐、土壤有机氮、粪便和污水,与地表水相比,地下水中硝酸盐受粪便和污水的影响较大;基于SIAR源解析模型分析,大气沉降、化肥、土壤有机氮和粪便污水对研究区地表水硝酸盐的贡献比例分别为3.97%、26.87%、36.80%和32.37%,对地下水硝酸盐的贡献比例分别为2.83%、13.96%、21.03%和62.18%.     

杭州市静稳天气指数构建及应用研究

采用杭州市近7年的气象与环保监测资料,综合考虑2 m相对湿度、10 m水平风速、日均海平面气压、24 h变压、24 h变温、低层逆温等气象因子,通过历史样本统计划分阈值范围再权重求和的方法,构建了静稳天气指数（SWI）.经过实况回算检验,分析所建指数与污染天气的对应关系,并应用到重污染天气成因分析、空气质量预报和污染减排评估等方面.结果表明：①SWI可以综合反映大气静稳程度,与PM_2.5浓度有较好对应关系,SWI越大越容易出现污染天气,SWI大值最易出现在冬季,其次为秋季和春季,夏季主要污染物往往是臭氧,不易发生中度以上的污染天气.②SWI可用于判断杭州秋冬季重度及以上污染天气的成因,平均而言SWI<6.7时不易出现重度及以上污染;若SWI<6.7时仍出现重污染天气,可判断主导风向上游的外来污染物输入是引起重污染的主要原因,根据前期SWI的相对大小可判断有无叠加前期本地污染物积累;若SWI持续大于6.7且出现重度及以上污染天气,可判断由大气静稳而产生的本地污染物堆积是主要成因.③依据预报数据计算的SWI对空气质量分级预报有较好的参考价值,在短期和中期预报时效内均有表现力.④将SWI应用到G20会议期间污染减排效果评估中发现,在气象条件静稳程度相当时,减排措施有效降低了污染程度.     

典型岩溶槽谷区土壤水δD和δ18O时空分布特征:以重庆市中梁山岩溶槽谷为例

为了揭示岩溶槽谷区土壤水氢氧同位素的时空分布特征,以重庆市北碚区中梁山为研究基地,于2017年5月和2017年9月收集降水及3种不同土地利用方式(耕地、草地和林地)不同深度的土壤水,利用稳定同位素技术研究不同土地利用方式下0~15 cm、15~45 cm土壤剖面的土壤水氢氧同位素时空变化特征.结果表明:(1)土壤水δD和δ~(18)O的平均值分别为-50.0‰±33.6‰和-7.9‰±4.3‰,其值均在大气降水线(LMWL)周围,说明降水是该区土壤水的主要补给来源;(2)土壤水δD和δ~(18)O具有明显的季节变化,5月(土壤水δD和δ~(18)O的平均值-19.4‰±6.8‰和-4.1‰±1.0‰)9月(土壤水δD和δ~(18)O的平均值-82.2‰±14.0‰和-11.9‰±2.2‰);(3)土壤水δD和δ~(18)O在不同土地利用方式下没有表现出明显差异;(4)土壤水δD和δ~(18)O随土壤深度呈梯度变化,5月耕地、草地和林地土壤水稳定同位素以垂直递减趋势为主,9月耕地和林地以递增趋势为主,草地以递减的趋势为主.     

Mercury bioaccumulation in aquatic biota along a salinity gradient in the Saint John River estuary

Although estuaries are critical habitats for many aquatic species, the spatial trends of toxic methylmercury(MeHg) in biota from fresh to marine waters are poorly understood. Our objective was to determine if MeHg concentrations in biota changed along a salinity gradient in an estuary. Fourspine Stickleback(Apeltes quadracus), invertebrates(snails,amphipods, and chironomids), sediments, and water were collected from ten sites along the Saint John River estuary, New Brunswick, Canada in 2015 and 2016, with salinities ranging from 0.06 to 6.96. Total mercury(proxy for MeHg) was measured in whole fish and MeHg was measured in a subset of fish, pooled invertebrates, sediments, and water. Stable sulfur(δ~(34)S), carbon(δ~(13) C), and nitrogen(δ~(15)N) isotope values were measured to assess energy sources(S, C) and relative trophic level(N). There were increases in biotic δ~(13)C and δ~(34)S from fresh to more saline sites and these measures were correlated with salinity.Though aqueous MeHg was higher at the freshwater than more saline sites, only chironomid MeHg increased significantly with salinity. In the Saint John River estuary, there was little evidence that MeHg and its associated risks increased along a salinity gradient.     

袋式除尘实现燃煤电厂锅炉烟尘“恒稳低排”的思考

针对燃煤电厂锅炉烟气实现低排放的目标,阐述了燃煤电厂采用袋式除尘的有效性和趋势性;通过几个典型工程案例的对比分析,阐明了燃煤电厂袋式除尘的先进性、可靠性及其实现"恒稳低排"的可行性,并就采用袋式除尘实现燃煤锅炉烟尘"恒稳低排"的技术措施提出了一些思考和建议。