Distribution of mercury in the sediments of Onondaga Lake,N.Y.

Sediment cores and surface grab samples were collected throughout Onondaga Lake, New York, to determine the concentrations and distribution of mercury (Hg) in the sediments. Horizontal distribution patterns show the effect of sediment focusing and localized sources, with generally low Hg concentrations in the littoral zone sediments, higher concentrations in the profundal sediments, and highest concentrations near known sources of Hg. Several cores were dated and reflect historical loading patterns, with low-level increases in Hg concentration starting in the early 1800s and a large increase in 1947 and decrease in 1970 related to the local chloralkali industry. These cores indicate that Hg has low mobility in profundal sediments and that the contaminated sediments are effectively being buried.     

云南滇池沉积物中重金属的形态分布特征

Fractionation of heavy metals in sediments can help in understanding potential hazards of heavy metals. The present study analyzed total concentrations and fractions of selected heavy metals （Cd, Cr, Cu, Pb, and Zn） in surface sediments from Dianchi Lake, Yunnan Province, China, as well as factors that may affect distributions of the various heavy metal fractions. Total concentrations of the heavy metals decreased in the order Zn 〉 Cu 〉 Pb 〉 Cr 〉 Cd. These heavy metals, except Cr, were much higher than their background levels, indicating that Dianchi Lake was polluted by Cd, Zn, Pb, and Cu. Cadmium occurred mainly as the non-residual fraction （sum of the HOAc-soluble, reducible, and oxidizable fractions） （97.6%）, and Zn （55.7%） was also predominantly found in the non-residual fraction. In contrast, most of the Cr （88.5%）, Pb （81.8%）, and Cu （59.2%） occurred in the residual fraction. Correlation analysis showed that total heavy metal concentrations, organic matter and reducible Fe were the main factors affecting the distributions of the various heavy metal fractions. In the Walhai section of Dianchi Lake （comprising 97% of the lake area）, the concentrations of Cd, Zn, Pb, and Cu in the non-residual fraction were significantly lower （P ≤ 0.01 or 0.05） than those of the Caohal section （3% of the lake area）. This indicated that potential heavy metal hazards in the Caohai section were greater than the Waihai section.     

中国太湖环境土壤磷测试与磷释放

A microtiter plate assay (MPA) for soluble reactive phosphorus (SRP) was applied to samples in overlying water and pore water as well as in three forms of environmental soil test phosphorus (P) types: water soluble phosphorus (WSP), diluted calcium chloride extractable phosphorus (PCaCl2), and Olsen-P in the sediments of Taihu Lake, China, where potential P release in response to pH was analyzed. MPA for rapid P analysis was shown to be promising when applied on samples of natural water and sediment extracts. Concentrations of WSP and PCaCl2 in the sediments were much lower than those of Olsen-P. Olsen-P levels in the littoral sediments along the north coast of Meiliang Bay in Taihu Lake (80 to 140 mg kg^-1) were much higher than those in the mouth of the bay (less than 50 mg kg^-1). The risk of P release in the mouth area of Meiliang Bay was lower than that in the north littoral zone with a risk of sediment P release induced by pH increases.     

滇池沉积物铵态氮的时空变化特征研究

沉积物在湖泊氮、磷循环和水体富营养化过程中起着重要作用。本研究应用GPS定位技术,于2003年5月至2004年5月,对滇池海埂、斗南、罗家村、新街、昆阳等5个代表性样点沉积物铵态氮含量进行为期1 a的动态监测,全面分析了滇池不同区域、不同层次、不同时期沉积物铵态氮的动态变化特征。结果表明,滇池沉积物铵态氮平均含量为74.57 mg kg-1,全湖沉积物铵态氮平均含量年变化范围是45.55~170.1mg kg-1。沉积物铵态氮因季节变化其变化幅度很大,各区域沉积物铵态氮含量总体趋势夏季高、冬季低,但不同位点变化高峰和趋势不同。不同层次沉积物铵态氮含量变化随季节而变化,夏季为表层(0~5 cm)中层(5~10 cm)底层(10~20 cm),冬季为中层表层和底层。表层、中层、底层沉积物铵态氮含量的变化范围分别为18.71~172.9mg kg-1、29.55~192.2mg kg-1、19.93~123.8mg kg-1。各区域沉积物铵态氮平均含量以罗家村最高,斗南最低。沉积物铵态氮与水体铵态氮、水体pH呈显著正相关,与沉积物有效磷呈显著负相关,暗示了沉积物铵态氮是水体氮的源和库,并影响着沉积物中磷的释放。     

滇池水和沉积物中氮磷空间变化

Dianchi Lake is one of the most eutrophic lakes in China. In order to understand this eutrophication and to help control the pollution, this research investigated the spatial distribution of Kjeldahl nitrogen (K-N) and total phosphorus (TP) through analysis of bottom water and sediment (3 depths) samples collected at 118 sites around Dianchi Lake. The concentrations of K-N and TP for the lake bottom water in the Caohai part of the lake were much higher than those in the Waihai part, generally decreasing from north to south. In the sediments, the K-N concentration was higher in the Caohai part and the middle of the Waihai part. On the other hand, TP in the sediments was greater in the southern and western parts. Both K-N and TP had similar spatial distributions for the sediment samples of three different depths.Vertically, the KoN and TP concentration in the sediments decreased with an increase in depth. This was evidence that eutrophication and pollution of Dianchi Lake was becoming gradually more severe. Exterior factors including uncontrolled input of domestic and industrial effluents as well as non-point pollution around the lake were the main reasons for serious eutrophication; therefore, controlling these was the first step in reducing eutrophication of Dianchi Lake.     

南四湖湿地生态系统能值分析与区域发展

为评估南四湖湿地生态系统的能量流动状况及其经济价值,采用H.T.Odum建立的能值分析理论,计算南四湖湿地生态系统多年平均的能值投入/产出,绘制南四湖湿地生态系统能值图,分析南四湖湿地生态系统结构和功能的整体特征。结果表明:南四湖湿地的投入量太阳能值为1.11×1021sej,产出量太阳能值为1.73×1020sej,初级生产力为1.61×1020sej,不可再生能源或资源(包括底泥和水体)为1.03×1021sej;同时,南四湖在水生维管束植物、以及鱼类产出方面生态效益价值显著。南四湖湿地能值投资率为0.000 9,净能值产出率为165.23,环境负载率为14.22,能值投资率低,净能值产出率高,环境负载率高,表明南四湖湿地对经济的贡献很大,区域经济发展水平较低,对环境依赖性强。     

鄱阳湖生态经济区农业系统的干旱脆弱性评价

干旱是鄱阳湖生态经济区面临的主要的生态问题之一。建立旱灾预警机制,需要深入理解旱灾发生的机理,评价干旱可能造成的损失,以便为政策的制定提供科学依据。选择代表干旱暴露度、敏感性与适应能力的14个因子,通过层次分析法确定了各因子的权重,运用综合指数法生成了研究区农业生态系统的干旱脆弱性指数。应用ArcGIS9.3软件绘制了研究区的干旱脆弱性空间分布图,结果表明该区域的对干旱以中度脆弱性为主;在空间分布上具有明显的南北分异规律,北部县市农业系统的干旱脆弱性总体上比南部县市的高。结合暴露度、敏感性与适应能力的空间分布深入分析了干旱脆弱性形成的机理,在此基础上对未来该区域的干旱防治与管理提出了针对性的建议。     

Modeling the elemental mercury cycle in Pallette Lake,Wisconsin, USA

The spatial and temporal distribution of elemental Hg (Hg°) and reactive Hg (Hg_R) has been studied on Pallette Lake, Wisconsin during May – August, 1993 and May, 1994. In general, Hg° concentrations near the lake surface greatly exceeded saturation with respect to atmospheric Hg° indicating a flux out (?) of the lake. Evasional losses were estimated using a thin film model and averaged ?101 pmol m^?2 d^?1 during July and August, 1993. A large portion of atmospherically deposited Hg is re-emitted. Thus, in-lake Hg° production' and evasion to the atmosphere will significantly reduce the amount of Hg which is transported to the sediments, the principal site of methylation. Laboratory experiments were conducted to ascertain the rate of Hg° formation from Hg(II). Reduction was significantly lower in heat sterilized lakewater suggesting Hg° production was biologically mediated. The temporal distribution of epilimnetic Hg°, as measured at the lake center, was influenced by Hg° evasion, Hg° production and advective transport of water parcels of differing Hg content. Spatial gradients in Hg° and Hg_R were identified and a transport model was employed to estimate the advective flux of Hg°. The importance of atmospheric deposition and sediment-water interaction as sources of Hg_R to epilimnetic waters were examined. Porewater concentrations of Hg° and Hg_R were determined on several occasions. During May, 1994, the depletion of lakewater Hg_R following a input pulse due to rain was observed and the estimated removal rate (16–20% d^?1) agrees well with reduction rates obtained in the laboratory (23% d^?1).     

南四湖流域土地利用及其景观格局变化分析

以1987年、2000年、2014年的Landsat影像数据为基础,借助ENVI,ArcGIS,Fragstats等软件,提取了土地利用信息,计算了景观指数,定量分析了流域土地利用变化及其对景观格局的影响。结果表明:（1） 近30年来,南四湖流域土地利用变化突出表现为耕地向建设用地的转化,耕地面积减少1 069.15 km²,建设用地面积增加1 573.26 km²。2000—2014年,土地利用综合动态度为0.461%,是1987—2000年的4倍。（2） 景观结构上,耕地是流域的主导斑块,面积约占70%,30年来占景观面积的比例降低了3.85%,斑块形状趋于复杂;建设用地日益发展为优势斑块,占景观面积的比例指数增加了6.1%。耕地与建设用地斑块在景观中的变迁,使得流域自然生态功能受到较为严重的干扰。（3） 流域总体的景观特征表现为优势斑块明显,景观比较完整,但空间异质性较高而连通性较低。近30年来景观结构由较完整的大斑块主导、演化成小斑块圈点状穿孔于大斑块的格局,景观破碎化较为严重。     

High-resolution imaging of phosphorus mobilization and iron redox cycling in sediments from Honghu Lake,China

Journal of Soils and Sediments - Phosphorus (P) pollution is a significant environmental problem in lakes, especially in lakes highly impacted by human activities, e.g., Honghu Lake. Years of...     

The importance of geological controls on the natural distribution of mercury in lake and stream sediments across Canada

The Geological Survey of Canada (GSC) has surveyed a significant portion of Canada using systematic stream and lake surveys under the National Geochemical Reconnaissance (NGR) program. Total mercury (Hg) data, available for most of the sites, reveal significant natural variation. Much of the observed variation in Hg concentration can be directly related to the composition of the bedrock, regolith and glacial deposits in the surrounding watershed. Some of the highest Hg values within the sediments of Ontario lakes occur southwest of Thunder Bay in an area underlain by shales known to be naturally enriched in Hg and other trace metals.     

Hydropower reservoirs enhanced the accumulation of heavy metals towards surface sediments and aggravated ecological risks in Jiulong River Basin,China

Journal of Soils and Sediments - In complex watersheds with multiple types of waterbodies, the effect of river damming on the distribution pattern of heavy metals in sediments and their potential...     

Seasonal changes of mercury speciation in the coastal sediments

Purpose

Mercury speciation in sediments is linked to environmental conditions and processes. Domination of particular mercury species depends on its source, displays considerable seasonal behavior, and may be further modified due to oxygen levels, icing conditions, or the input of fresh organic matter. The purpose of this study was to examine the coastal area of the Gulf of Gdańsk in terms of mercury contamination and the influence of seasonal environmental changes on its speciation.

Materials and methods

In three highly dynamic coastal sites, mercury speciation in sediments was studied in relation to other environmental parameters (redox conditions, organic matter concentration, bacteria abundance, etc.). Sediment and water samples were collected monthly during a 3-year study. Sequential extraction of sediments was used for identification of four inorganic mercury species: dissolved, bound with fulvic and humic acids, mercury sulfide, and residual fraction. Cold vapor atomic fluorescence spectrometry (CV-AFS) was used for extracts and liquid sample analysis. Total mercury in sediments was measured with atomic absorption spectrometry (AAS). Changes in salinity were analyzed by measurements of chloride and sulfate ion concentrations using ion chromatography. Bacteria number and biomass were measured by direct counting using epifluorescence microscopy.

Results and discussion

Seasonal changes in mercury speciation were observed at all sites and attributed to different processes. Labile mercury fraction contribution varied from 0 to 80%. The speciation patterns varied locally as the stations selected for the study are diversified in terms of anthropogenic impact, water dynamics, and output from land. Mercury concentrations at all stations fluctuated during phytoplankton blooms, icing of marine waters, precipitation, or increased surface runoff from the land. In this local scale, the global climate changes are visible already as environmental conditions in studied area changed in comparison to elder research.

Conclusions

Obtained results suggest that although mercury emissions to the environment have decreased in recent years, local weather conditions, which may be intensified by climate change, seriously affect the bioavailability of past mercury deposits in coastal sediments.

     

137Cs dating of lacustrine sediments and human impacts on Dalian Lake,Qinghai Province,China

¹³⁷Cs and grain-size analyses indicate the total amounts of ¹³⁷Cs deposited by wind and water in the Dalian Lake of Gonghe Basin, Qinghai Province. The vertical profile of ¹³⁷Cs in the lacustrine sediments shows three ¹³⁷Cs activity peaks and one trough: the main peak corresponds to the global ¹³⁷Cs fallout in 1963; the two secondary peaks correspond to the leakage of the Chernobyl reactor in 1986 and complete desiccation of the lake in 1994. The trough corresponds to aeolian deposition caused by extensive reclamation of farmland in late 1980s and early 1990s. The ¹³⁷Cs dating was used to evaluate sedimentation rates in Dalian Lake since 1963. They are divided into three periods: two with slow deposition (1963–1986 and 1994–1998), and one with rapid deposition (1986–1994). ¹³⁷Cs seems to have the same potential for indicating environmental changes and human interference in the arid and semiarid regions as in humid regions.     

Impact of sedimentation history for As distribution in Late Pleistocene-Holocene sediments in the Hetao Basin,China

Journal of Soils and Sediments - To understand the impact of geochemical sedimentation history for arsenic (As) distribution in the sediment profiles of the Hetao Basin, we (1) evaluated sediments...     

Seasonal variations of concentrations, profiles and possible sources of polycyclic aromatic hydrocarbons in sediments from Taihu Lake, China

Purpose

Obtaining a better understanding of the concentrations and origins of polycyclic aromatic hydrocarbons (PAHs) in the sediments Taihu Lake, China, is of paramount importance for the environmental protection and remediation of this lake. To investigate temporal and spatial variations in PAH concentrations, composition and possible source categories, 29 sediment samples were collected from Taihu Lake during both the flooding and dry seasons of the lake.

Materials and methods

Fifteen US Environmental Protection Agency priority PAHs were detected in 58 surface sediments (29 for each season) by gas chromatograph/mass selective detection, following extraction by accelerated solvent extraction.

Results and discussion

The concentrations of the total and individual PAHs in the flooding season were higher than those in the dry season, suggesting that high levels of fishing activity may be an important contributor to PAH pollution in the flooding season. The fractions of high molecular weight PAHs in the flooding season ranged from 63?% to 71?% and were higher than those in the dry season (which ranged from 52?% to 65?%). These results indicate that vehicle exhaust may be a more important pollutant source in the flooding season than in the dry season. Diagnostic ratios, principal component analysis and hierarchical cluster analysis were used to study possible source categories in the different seasons. Consistent results were obtained for all techniques. Seasonal and spatial variations were also investigated by the coefficient of divergence method. The results of previous studies support the conclusion of source identification.

Conclusions

Vehicle emissions were the dominant contributor to PAHs in the flooding season, while PAHs in the dry season sediments may have come from multiple sources. The findings of this study may provide a theoretical basis for seasonal PAH control strategies for Taihu Lake.     

Wet deposition of mercury and ambient mercury concentrations at a site in the Lake Champlain basin

The “Great Waters” program, established in the 1990 Clean Air Act Amendments, mandated that atmospheric deposition of hazardous air pollutants to Lake Champlain (including Hg) be assessed. An assessment of the magnitude and seasonal variation of atmospheric Hg deposition in the Lake Champlain basin was initiated in December 1992 with one year of event precipitation collection, as well as collection of vapor and particle phase Hg in ambient air. Samples were collected at the Vermont Monitoring Cooperative air monitoring site at the Proctor Maple Research Center in Underhill Center, VT. The average volume-weighted concentration for Hg in precipitation was 8.3 ng/L for the sampling year and the average amount of Hg deposited with each precipitation event was 0.069 μg/m². The total amount of Hg deposited through precipitation during 1993 was 9.26 μg/m²/yr. A seasonal pattern for Hg in precipitation was evident, with increased concentrations and deposition during spring and summer months. Meteorological analysis indicated the highest levels of Hg in precipitation were associated with regional transport from the south regardless of season, and with transport from the west, southwest and northwest during spring and summer months. Concentrations of ambient vapor phase Hg were typical of rural locations and consistent across seasons. Ambient particulate Hg concentrations averaged 11 pg/m³ with highest concentrations during the winter months.     

Historical distribution of DDT residues in pond sediments in an intensive agricultural watershed in the Yangtze-Huaihe region,China

Purpose

The extensive use of chemical pesticides on farmlands during the last several decades in China has led to a rapid deterioration of environmental water quality in recent years. The aims of this study were to: reconstruct the history of pesticide residues, determine the input load and residual load of dichlorodiphenyltrichloroethane (DDT) pesticides, and assess the risk of pesticide residues to aquatic ecosystem and human health.

Materials and methods

Caesium-137 was used to date sediment cores collected from ponds representing four land use types of an agricultural watershed with high-yield grain production and characterized by multipond systems in the Yangtze-Huaihe region of China. These ponds were selected to establish the historic pattern of DDT pesticide residues.

Results and discussion

(1) The mean total concentration of DDT residues including p,?p?′-dichlorodiphenyldichloroethylene (p,p′-DDE), p,?p?′-dichlorodiphenyldichloroethane ( p,p′-DDD), o,p′-DDT, and p,p′-DDT in sediment in the watershed was 82 μg kg^?1, ranging from under the detection limit to 457 μg kg^?1, which was mostly contributed by p,?p′-DDE (57 μg kg^?1 on average). Spatially, total concentrations of DDT residues in farmland pond sediment were the highest, reaching as high as 457 μg kg^?1. Temporally, an inflection point appeared in the 1970s, prior to which DDT contents increased with time, after which concentrations showed a decreasing trend. (2) In total, 323 kg DDT pesticide was applied to the Liuchahe Watershed since 1955. The total retention of four DDT residues in the multipond system was 14 kg (～4 % of the input), and most DDT pesticide was degraded to p,?p?′-DDE. (3) More than 80 % of sediment DDT residues exceeded their interim freshwater sediment quality guidelines, and the percentages of DDT,DDD, and DDE residues exceeding probable effect limit (PEL) values were 57, 29, and 70 %, respectively, which indicated a moderate to high ecological risk of DDT in this watershed.

Conclusions

Our results clearly reveal that the extensive use of pesticides has resulted in significant pesticide residual pollution in this watershed, which could severely deteriorate water quality and threaten aquatic ecosystem and human health in the watershed and, thus, remain a cause for concern.     

汞沉淀对黑麦草中汞含量及其分布的影响

A grass(Italian rye grass)experiment with complete desing of three factos(Hg,grass and exposure)and two levels(with and withou the factor tested)was carried out in Goeteborg,Sweden from May to September,1995,toward understanding the effect of mercury deposition on plant Hg content and its distribution.It has been found that besides the two general pathways of Hg absorption,i.e.root uptake and foliar absorption,mercury deposition can aslo signifcantly incease Hg content and total load in grass.Such effects seem to be confined only within the above-ground parts of grass plant.Estimate has been made to make clear of the contributions of different pathways to Hg Content and total Hg load in the upper part of grass.Results showed that the contribution of Hg deposition accounted for 27%-32%,of Hg content in the above-ground parts of grass plant without adding Hg to the soil.decreasing with the increase of soil and/or air Hg concentrations.The increment of Hg load in the upper part of grass plant caused by Hg deposition during an interval of two weeks varied between 0.01-0.07μg pt^-1,contributing to 17%-48% of the total Hg load in grass plant exposed.     

Distribution of mercury in the aquatic food web of Onondaga Lake,New York

Historical discharges of mercury (Hg) to Onondaga Lake, New York, have resulted in elevated Hg concentrations in lake fishes. In 1990, a remedial investigation and feasibility study (RI/FS) was initiated to evaluate problems related to Hg and other hazardous substances in the lake. As part of the RI/FS, the distribution of Hg in the aquatic food web was determined to provide input to a site-specific model of Hg cycling and to evaluate potential ecological risks of Hg in the lake. Mercury concentrations were measured in surficial sediments, sediment interstitial water, lake water, phytoplankton, Zooplankton, benthic macroinvertebrates, and fishes (including planktivores, benthivores, and piscivores). The percentage of total Hg accounted for by methyl-Hg (CH₃Hg) generally increased with higher trophic levels, confirming that CH₃Hg is more efficiently transferred to higher trophic levels than is inorganic Hg. Concentrations of total Hg in amphipods and chironomids were closely related to concentrations of total Hg in sediments, suggesting that sediments are a likely source of Hg for benthic macroinvertebrates. Mercury concentrations in edible muscle tissue (fillets) of lake fishes have declined substantially from values found in the early 1970s, reflecting the large reductions in Hg discharges to the lake that have occurred since that time. The CH₃Hg concentrations in fillets and whole bodies of fishes generally were similar, indicating that concentrations in fillets often can provide estimates of concentrations in whole bodies. Methyl-Hg concentrations and bioaccumulation factors increased with higher trophic levels in both the pelagic and benthic components of the lake food web.