Uncertainty Analysis of Regional Mercury Exposure

A modeling system has been developed to simulate regional environmental exposure to mercury due to atmospheric deposition of mercury to watersheds. The atmospheric fate and transport of mercury is simulated using a comprehensive three-dimensional Eulerian model, the Trace Element Atmospheric Model (TEAM). The aquatic chemistry and bioaccumulation of mercury in fish are simulated using a model of mercury cycling in a lake/watershed system, the Regional Mercury Cycling Model (R-MCM). Fish consumption was derived from a review of available surveys. Previous work focused on an assessment of the environmental and inter-individual variability in key input data (Seigneur et al., 1997a). We address here the uncertainties associated with critical model input variables (e.g., atmospheric deposition velocities, precipitation rate, limnological characteristics). A probabilistic assessment is conducted to propagate the uncertainties in the input data through the modeling system and develop a probability distribution of the human mercury dose that reflects these uncertainties. The standard deviation of the distribution of the calculated human dose is about 50% of the mean value. For the example considered here (i.e., Park Lake in Michigan, U.S.A.), 80% of the uncertainty in the human dose was due to uncertainties in the speciation of mercury air emissions, pH and temperature of the lake, burial velocity of the sediments, and rate of fish consumption.     

白洋淀柱状沉积物磷形态及其分布特征研究

应用淡水沉积物磷形态的标准测试方法（SMT）,调查了白洋淀6个典型湖区柱状沉积物中的磷形态分布、垂向及在两种沉积物粒级（砂土和粉砂/粘土）上的变化特征,分析了各形态磷之间的相关性。结果表明,白洋淀各湖区柱状沉积物总磷（TP）的平均含量为531~1223mg.kg-1DW,无机磷（IP）是白洋淀沉积物中磷的主要成分,占TP的72~83。湖区水体的污染及富营养化程度影响着生物可利用的铁/铝结合态磷（Fe/Al-P）在白洋淀不同湖区沉积物中的分布,从各形态磷含量和百分含量的变化幅度来看,均是Fe/Al-P〉有机磷（OP）〉钙结合态磷（Ca-P）。在垂向分布和两种粒级沉积物颗粒上,白洋淀沉积物各形态磷都有一定的变化规律,但不同磷形态的变化趋势不同,差异性也不一致。各形态磷相关性分析表明,在平均含量、垂向及粒级分布上,IP和Ca-P之间呈较好相关性,说明稳定的Ca-P是IP的主体;而在平均含量和垂向分布上,TP与IP和Ca-P之间都存在着较好的相关性,说明沉积物中TP的含量主要来自IP中的Ca-P。研究结果对于探讨白洋淀水污染沉积历史及内源磷释放对水体富营养化的贡献具有重要意义。     

Manipulation of the Sediment-Water Interface of Extremely Acidic Mining Lakes with Potatoes: Laboratory Studies with Intact Sediment Cores

The water of flooded, abandoned, open-cast pits (Tagebauseen) in the Lusatia region of eastern Germany is characterised by a high acidity (Fe3+/H+), low pH (2.5-3.5) and low concentrations of dissolved phosphorus (SRP) and carbon (DIC). Investigations are investigating the use of amendments to assist in removal of acidity from Tagebauseen through controlled eutrophication. A simple system has been developed to investigate the effects of amendments on water chemistry around the sediment-water interface. Intact, little-disturbed sediment cores (diameter 5.5 cm) with overlying water (total volume 1.5 1) from one Tagebausee (Koschen: pH 3.1, Fe 15-20 mg/l) have been incubated at low temperature (6-10 °C) to investigate the effects of organic amendments (potato) on the concentrations of some major ions in the system. In particular, the dynamics of Fe, P, N and C over time in the presence or absence of organic amendment (potato) have been investigated. Addition of potatoes results in the rising of a sharp pH gradient from near the sediment surface, and an overall increase in dissolved Fe, P and C in the system. The Fe eventually precipitated as black particulates but the SRP remained in solution. Intact sediment cores provide a useful tool for studying changes in water column and sediment pore water chemistry and the potential effects of amendments on the sediments of Tagebauseen.     

指纹技术识别泥沙来源:不确定性研究进展

泥沙指纹技术是近年来研究流域泥沙来源与动态变化的一项重要技术方法,其主要局限性在于诸多的前提假设与实践条件的差异带入了一系列不确定性。泥沙从源到汇的迁移过程受自然环境和人为干扰的影响,其源地特征、迁移路径以及泥沙性质的潜在变化等均是指纹技术应用的不确定性因素,而采样方案设计、指纹选择方法、混合模型应用的一些主观因素进一步增加了不确定性的来源。不确定性分析是泥沙指纹技术的重要组成部分,是评估泥沙来源指纹识别结果可靠性的主要依据。本文综述了泥沙指纹技术的诸多不确定性问题以及主要应对方法的研究进展,总结了当前不确定性定量评估的研究现状并提出了未来的研究展望。     

Heavy Metal Distribution in Sediment Cores from Western Ross Sea (Antarctica)

Seven sediments cores collected in the Western Ross Sea (Antarctica) were investigated for heavy metals (Cr, Ni, Ph, Cd, Co, Zn Cu and Fe. Mn), several major elements (Ca, Ba and AI), total and organic carbon, and isotopic composition in order to investigate vertical variability. Samples were analyzed by ET-AAS and ICP-AES for metals and by CF-IRMS for carbon content. Generally, concentrations at the background levels were higher with respect to recent ones excluding in this area any kind of anthropogenic contamination. Cluster and Factor Analysis were applied. Best correlations were obtained for the elements showing geochemical affinities.     

Mercury Concentration and Monomethylmercury Production in Sediment: Effect of Dredged Sediment Reuse on Bioconcentration for Ragworms

The effect of dredged sediment reuse on the production and bioconcentration of monomethylmercury (MMHg) was investigated by examining sediments and ragworms found in dredge material banks and surrounding sites in the Venice Lagoon, Italy. Total Hg concentrations in the surface 20 cm of sediments were higher in the banks than in the surrounding sites, but MMHg concentrations were similar, which suggests reduced MMHg production in the banks. Monomethylmercury content in ragworms was significantly lower (p?<?0.05) in the banks than in the surrounding sites. In pore water, concentrations of both sulfate and Fe decreased with depth in the upper 20 cm of the dredge banks. In contrast, sulfate concentrations were constant with depth and large amounts of dissolved Fe occurred in the upper 20 cm of sediments of surrounding sites. Continuous sulfate reduction and possible precipitation of iron sulfide may decrease the production and bioconcentration of MMHg in the dredge material banks compared to the surrounding sites. Overall, the production of MMHg in sediments and its bioconcentration in benthic organisms were connected to the process of sediment diagenesis of organic matter through the control of pore water and sediment geochemistry involving iron and sulfur.     

Influence of Sediment Preservation on Total Mercury and Methylmercury Analyses

Estuarine and riverine sediments from fourlocations showing different sediment structures wereanalysed as fresh, thawed and lyophilised samples fortotal mercury (TotHg) and methylmercury (MeHg)concentrations, and results were compared to addresseffects of sample preservation on Hg speciation. TotHg was measured by cold vapour atomic absorptionspectrometry (CVAAS). MeHg was isolated bydistillation and ion-exchange and analysed by coldvapour atomic fluorescence spectrometry (CVAFS) afterpreconcentration on a gold trap. No loss of TotHg norMeHg due to lyophilisation was found. Concentrationsof TotHg and MeHg respectively ranged from 92 to 267ng g^-1 dw and 1.1 to 2.9 ng g^-1 dw in freshsamples, from 94 to 215 ng g^-1 dw and 1.1 to 2.8ng g^-1 dw in thawed samples, and from 100 to 256ng g^-1 dw and 1.2 to 3.1 ng g^-1 dw inlyophilised samples. Lyophilised samples showedbetter homogeneity and better MeHg analysisreproducibility compared with wet samples.     

Historical Changes in Levels of Organic Pollutants in Sediment Cores from Brno Reservoir, Czech Republic

Results of a comprehensive study are presented on the spatial and depth-related distribution of persistent organic pollutants (POPs) in sediments of the Brno reservoir, Czech Republic. Based on sedimentological observations, three major historic phases were identified related to the evolution of the depositional environment, flow rate, and material input. Data on organic carbon, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and organochlorine pesticides showed specific distribution patterns in a 3-m-deep core. The analysis of the depth trends of the geochemical data combined with sedimentology made it possible to distinguish between remote sources of the pollutants, early weathering alterations of POPs, transport by river associated with organic matter as sorbent on one hand, and local sources weakly related to lithology on the other hand. The integrated sedimentological and environmental geochemical archive provided an improved dynamic view of the pollution in historical terms.     

Streamwater Particulate Mercury and Suspended Sediment Dynamics in a Forested Headwater Catchment

Due to the inherent differences in bioavailability and transport properties of particulate and dissolved mercury (Hg_P and Hg_D), it is important to understand the processes by which each is mobilized from soil to stream. Currently, there is a paucity of Hg_P data in the literature despite the fact that it can be the dominant fraction in some systems. We analyzed Hg_P in conjunction with volatile solids (VS, an estimate of organic content) and total suspended solids (TSS) and investigated the viability of using turbidity as a surrogate measure of Hg_P. Samples were collected for flow conditions ranging from 72 to 8,223 L?s^?1 during October 2009 through March 2010 in a 10.5-km² forested headwater catchment. Total Hg concentrations ranged from 0.28 to 49.60 ng L^?1, with the relative amount of Hg_P increasing with discharge from approximately 40% to 97%. Storm dynamics of Hg_P and Hg_D were not consistent, indicating unique controls on the export of each fraction. During high-flow events, Hg_P was consistently higher on the rising limb of the hydrograph compared with the receding limb for a range of discharge events, with this hysteresis contributing to a degraded relationship between Hg_P and streamflow. Overall, Hg_P was strongly positively correlated with VS (r ²?=?0.97), confirming the known association with organic carbon. Due to a consistent organic fraction of the suspended solids (34?±?6%), Hg_P was also well correlated with TSS (r ²?=?0.95), with an average of 0.10 ng of Hg_P per milligram of TSS in this system. Stream turbidity measured with an in situ sonde also had a strong correlation with TSS (r ²?=?0.91), enabling commutative association with VS (r ²?=?0.86) and Hg_P (r ²?=?0.76). Turbidity can explain more than twice the temporal variance in Hg_P concentrations (n?=?50) compared with discharge (r ²?=?0.76 versus 0.36), which leads to improved monitoring of Hg_P dynamics and quantification of mass fluxes.     

Surface-water Acidification and Reproducibility of Sediment Cores from Kejimkujik Lake, Nova Scotia, Canada

A total of nine sediment cores were collected from the five deep basins of Kejimkujik Lake, located in southwestern Nova Scotia, Canada, in order to track changes related to surface-water acidification and to test reproducibility of results between sediment cores from different basins in a large lake. Present-day and pre-industrial (c. 1850) samples were analyzed from all cores and detailed diatom profiles were undertaken on three cores to determine the timing of acidification. All three detailed diatom profiles show declines in inferred pH starting in the early 1930–1940s. Since the 1940s, diatom-inferred lakewater pH has declined from a background pH of ～5.8 (± 0.4) to a current diatom-inferred pH of ～4.9 (± 0.1). This corresponds to the current (2001–2002) range of measured lakewater pH?=?4.7–5.2 with a mean pH?=?4.9. Species diversity of diatoms also declines markedly in all cores with the Hill’s N2 index decreasing from ～5 to near 1. The pre-impact diatom assemblages were dominated by Aulacoseira spp. and have since changed to dominance by Asterionella ralfsii var. americana (>45 μm). All nine sediment cores showed similar changes in diatom assemblages, diatom-inferred pH, and timing of the onset of acidification. Thus, paleolimnological inferences from deepwater sediment cores were highly reproducible in this large, morphometrically complex lake system.     

渤海湾各形态重金属的地球化学特征及其环境意义

根据2008年对渤海湾的调查,重点研究了渤海湾湾内和湾口柱状沉积物重金属的生物地球化学特征,通过剖析不同形态重金属的特征,结合渤海湾生态环境信息的综合分析,系统探讨了渤海湾沉积物重金属的演变趋势、影响控制因素以及潜在生态风险。结果表明,湾内海河口附近沉积柱重金属含量有几次突变,20～22cm段极小值可对应1939年海河北系的洪水,10～12cm段极小值可对应1963年海河南系的洪水,1963年至今重金属含量有逐渐增加的趋势。不同形态重金属百分含量从大到小为：残渣态〉铁锰氧化物结合态〉碳酸盐结合态〉有机结合态〉可交换态,且重金属在海河口附近都表现出较高的可浸取态百分含量。风险评价结果表明,重金属总量富集因子由大到小为：Pb〉Cd〉Zn〉Cr〉V〉Co〉Cu〉Ni,其中Pb、Cd和Zn的富集因子均大于1,说明其有污染,但渤海湾沉积物总体质量良好,潜在生态风险较低。从重金属形态角度评价,V和Cr无污染,Zn、Co、Cu、Ni和Pb在湾内及湾外均有不同程度的污染,而Pb的污染最为严重。     

北江沉积物汞污染现状与评价初步研究

为了了解北江沉积物中汞污染现状、来源并评价其污染程度,在北江流域共采集19个沉积物样,用原子吸收法（AAS）和冷原子荧光法（CVAFS）分别测定了其总汞（THg）和甲基汞（MeHg）含量,比较了甲基化率,并用污染指数法对测定结果进行了评价。结果表明,北江沉积物THg含量为73.7～3 517 ng·g^-1（干重）,均值为607.6 ng·g^-1,MeHg含量为 0.392～2.384 ng·g^-1,均值为1.302 ng·g^-1,韶关冶炼厂为重要污染点源。各采样点甲基化率差异较大,进一步研究影响甲基化的因素具有重要意义。沉积物中THg、MeHg平均污染指数分别为3.04、26.04,表明均为中度污染。     

Factors Regulating the Flux of Phosphate at the Sediment - Water Interface of a Subtropical Calcareous Lake: a Simulation Study with Intact Sediment Cores

Different factors which interactively control the flux of soluble reactive phosphorus (SRP) at the sediment water irterface (SWI) of Lake Kinneret were studied seasonally. The influence of pH, Eh and microbial activity on SRP flux at the SWI was investigated by manipulating the conditions in the overlying water of intact sediment cores. The calculated diffusive SRP flux out of the sediment was lower in cores sampled during winter and spring than during the period of amixis. Potential SRP release, as measured in the absence of microbial activity, was strongly enhanced upon the transition from oxic to anoxic conditions indicating P release from iron(III)-bound phosphorus. In spring and summer cores, an enhanced SRP flux from sediments at pH 7 in comparison to pH 8 indicated P release from carbonate-bound P which sedimented previously as result of high pH values during the algal spring bloom. Microbial uptake at the SWI was the most important sink for SRP and no net-flux occured under oxic conditions. The higher net-flux of P under anoxic conditions was linked to carbon limitation ofthe bacteria at the SWI.     

Mercury in Lake Vänern, Sweden Distribution In Surface Sediment And Catchment Budget

Lake Vänern is Sweden's largest lake and freshwater reservoir. Large quantities of mercury were released into the lake during a large part of the 20th century, resulting in serious contamination. The main load originated from one single point source — a chlor-alkali industry. Its releases were drastically reduced in the early 1970's, but nearby sediments displayed alarmingly high concentrations. During summer 2001, fifty-one sediment cores were taken, and analysed for total mercury. It was found that mercury concentrations in surface sediments have decreased significantly between 1974 and 2001, but the influence of the former single point source was still reflected in the concentration patterns. Thirty years ago, sediments around the dominant point source displayed the highest concentrations. Today, the highest concentrations in surface sediments were still found close to it, but also in deep waters in the central part of the lake. Surprisingly, the gradient from the point source is stronger today compared to 1974. A mercury budget, based on the annual sediment accumulation rate, the bulk density, atmospheric load and outflow of mercury, was formed. The surface sediments (0—1 cm, on average corresponding to ～5 yr according to ¹³⁷Cs dating) in accumulation bottoms (water depth >40m) contained approximately 530 kg Hg (corresponding value for year 1974 was 4100 kg Hg). A majority of the present additions of mercury to the lake originates from atmospheric deposition. It was also found that the lake acts as a sink for mercury. In fact, approximately 90—95% of the incoming mercury was retained within the catchment or in the sediments.     

降雨空间分布不均匀性对流域径流和泥沙模拟影响研究

对降雨空间分布变化的不完全理解，以及缺乏足够的数据来描述降雨的空间分布．阻碍了分布式水文模型的发展。以黄河下游洛河卢氏水文站以上流域为研究区．在GIS技术支持下．采用目前分布式水文模型中应用广泛的Thiessen多边形法确定降雨空间分布，选取分布式水文模型SWAT(Soil and Water Assessnlent Tools)研究降雨空间分布不均匀性对流域径流和泥沙模拟的影响。结果表明雨量站密度、雨量站分布和降雨空间分布变化均对模拟结果产生了较大影响．这在一定程度上限制了分布式水文模型的应用和参数识别。此外，Thiessen多边形法对面雨量的估算结果是令人满意的，但对降雨空间分布的描述能力较差。     

基于Crystal Ball的泥沙来源指纹判别及不确定性评价

土壤固有的空间变异性及对侵蚀强度响应程度的不同,造成利用采集的少量样品中指纹因子的平均值或中位数来表征物源或泥沙时存在较大的不确定性,进而影响物源贡献判别结果的可靠性。已有的蒙特卡洛模拟算法通常基于较为复杂的计算机语言,对一般研究者来说具有一定的挑战性。介绍一种简便快捷的分析软件Crystal Ball,并结合实例分析了其在流域泥沙来源判别中的应用。     

Rhizoliths in Devonian and Early Carboniferous Paleosols and Their Paleoecological Interpretation

Eurasian Soil Science - Collected in situ rhizoliths (&gt;20) from Devonian and Early Carboniferous paleosols in the southern part of the Russian Platform (Kaluga, Belgorod, and Voronezh...     

Evaluating the Contribution of Long-Range Transport of Heavy Metals from the Asian Continent to Their Concentrations in Sediment Cores from Lake Shinji,Western Japan

The historical trend of heavy metal pollution recorded in sediment cores from Lake Shinji, western Japan, was investigated to evaluate the contribution of increasing long-range transport of heavy metals from the Asian continent in recent years. The concentrations of Cd, Co, Cr, Cu, Ni, Pb, Sb, and Zn and lead isotope ratios were determined for sediment cores collected at two sites in the lake. Among the metals, Cd, Sb, and Zn showed markedly high concentrations since the 1970s. Moreover, a high Pb concentration and less radiogenic lead isotope ratios have been observed since the 1980s in the core from a site close to the mouth of a major river. Air masses from the Asian continent, including China, Russia, and South Korea, have less radiogenic lead isotope ratios than those from Japan. This suggests that the recent increase in Pb concentration in the sediment core is primarily due to the long-range transport of heavy metals from the Asian continent, followed by their deposition in the catchment area of the river. The concentration ratios of Pb/Cd, Pb/Sb, and Pb/Zn of the sediment around 2000 were calculated on the basis of the metal concentrations in excess of those before 1940. They were then compared with the volume-weighted annual average concentration ratios of Pb/Cd, Pb/Sb, and Pb/Zn of rain samples collected on the shore of the lake for 1999–2001. The result showed that the ratios of the former to the latter are 1.0 for Cd, 0.69 for Sb, and 0.31 for Zn. Thus, it is likely that the long-range transport of Cd and Sb from the Asian continent also contributes significantly to the recent increase in the concentrations of these metals in the sediment core from Lake Shinji. For Zn, however, the contribution from the Asian continent was evaluated to be small, suggesting the importance of local sources such as effluent discharges.     

Phosphorus Fractionation in Sediment Cores Collected In 2005 Before and After Onset of an Aphanizomenon flos-aquae Bloom in Upper Klamath Lake, OR, USA

We tested the hypothesis that there would be measurable losses of phosphorus (P) from surficial sediments of Upper Klamath Lake (UKL), Oregon, if sediments were a source of P during an algal bloom. We compared concentrations of total and forms of P at various depths in cores collected before and after the onset of a large Aphanizomenon flos-aquae bloom. Concentrations of inorganic P were determined in extraction solutions of MgCl₂ (1 M, pH 8), citrate-dithionite-bicarbonate, and 1 M HCl. Sediments below 2 cm were dominated by residual P which is defined as total P minus inorganic P. During the study period, data from the top 2-cm of sediment indicated (a) significant decrease in total P concentration, primarily associated with iron oxyhydroxides at one site, and (b) significant increase in total P concentration associated with residual P at a second site. Data from two other sites indicated no net changes in concentrations of total P.     

淤地坝赋存信息在流域侵蚀产沙研究中的应用

黄土高原淤地坝在拦蓄大量泥沙的同时,也赋存了大量环境变化信息。该文从淤地坝赋存信息在小流域侵蚀产沙速率、泥沙来源和泥沙输移比研究方面的作用进行了归纳和总结,分析了目前研究中存在的问题,提出了今后研究的发展方向,以期能为更好地利用这些赋存信息,发挥其在黄土高原土壤侵蚀和环境演变过程研究中的作用提供参考。