共查询到20条相似文献,搜索用时 31 毫秒
1.
Tracing the source of mercury contamination in the Dorena Lake watershed, Western Oregon 总被引:2,自引:0,他引:2
Although fish in Dorena Lake are contaminated with mercury, the source of pollution in the watershed was unconfirmed until the present study. To trace the mercury to its source, fine-grained sediment samples were collected from the major streams of the watershed. A few samples of mine waste/tailings were also obtained from the Bohemia Mining District where mercury was historically used in processing gold and silver ore. Mercury concentrations in sediment from streams that do not drain the central mining district average 0.066 ppm, whereas samples taken downstream of the district contain 0.140-1.339 ppm. Mine waste/tailings contain 13.441 to >50 ppm mercury. The source of mercury contamination in the Dorena Lake watershed is thus the Bohemia Mining District. Historical and geological evidence strongly suggests that the mercury problem in the district resulted from gold-mercury amalgamation practices, but naturally high mercury content in mineralized areas cannot be ruled out with the data presented here. 相似文献
2.
D. S. Leigh 《Environmental Geology》1997,30(3-4):244-251
Gold was discovered in 1829 and mined until about 1940 in north Georgia, particularly within an area known as the Dahlonega
mining district. The mining operations there, which involved mercury amalgamation in stamp mills and sluices, delivered significant
quantities of mercury waste to streams. This paper focuses on the downstream dispersal and storage of mercury in streambank
sediments of two watersheds near Dahlonega, Georgia. Mercury concentrations for individual samples of historical sediment
range from 0.02 to 12.00 ppm, with average values in streambanks near the core of the mining district ranging from 0.2 to
0.6 ppm. Mercury levels rapidly decrease in the downstream direction to concentrations that are slightly above a background
level of 0.04±0.02 ppm. Mercury concentrations also appear to decrease with increasing distance from streambanks. Similar
levels of mercury contamination from former gold mines probably exist in many other parts of the gold-bearing rocks of the
Piedmont of the eastern United States. The bioavailability and environmental hazard posed by the contaminated sediment is
not certain.
Received: 8 January 1996 · Accepted: 29 May 1996 相似文献
3.
Mercury contamination of active channel sediment and floodplain deposits from historic gold mining at Gold Hill,North Carolina,USA 总被引:2,自引:1,他引:1
A reconnaissance investigation of mercury contamination associated with historic gold mining in North Carolina, USA, revealed
high concentrations of mercury in channel and floodplain sediments downstream from the Gold Hill mining district. The most
intense period of mining activities in this region occurred in the 1840s and 1850s when mercury amalgamation was used to recover
fine gold particles from milled ore. This paper evaluates mercury concentrations measured in active channel sediments and
two cores recovered from historic floodplain deposits of the lower portion of Dutch Buffalo Creek. Mercury concentrations
in these cores range from 0.01 to 2.2 mg/kg, with maximum concentrations more than 35 times background levels. A later peak
in copper concentrations is associated with the operation of a large copper mine between 1899 and 1906. Following the most
intense periods of mining, both mercury and copper concentrations decrease upcore to constant levels of about twice pre-mining
background concentrations. Results suggest that vertical trends in mercury and other trace metals provide a useful tool for
interpreting rates of historic floodplain sedimentation in the Piedmont of North Carolina. 相似文献
4.
Trace element concentrations in shallow marine sediments of the Buyat-Ratototok district of North Sulawesi, Indonesia, are
affected by submarine disposal of industrial gold mine tailings and unregulated dumping of tailings and wastewater from small-scale
gold mining using mercury amalgamation. Industrial mine tailings contained 590–690 ppm arsenic, 490–580 ppm antimony, and
0.8–5.8 ppm mercury. Tailings-affected sediment As and Sb concentrations were 20–30 times higher than in muddy sediments not
contaminated with tailings, and 50–60 times higher than pre-mining average. Highest mercury concentrations were observed in
sediments affected by small-scale mining using mercury amalgamation (5–29 ppm). Concentrations of most other trace elements
were comparable in sediments affected by both types of mining and were slightly higher than regional averages for sediments
collected before the onset of industrial mining. Elevated concentrations of both As and Sb in approximately equal proportions
suggest tailings dispersal of at least 3.5 km. Mercury released from artisanal gold mining dispersed up to 4 km from river
mouths. Slight increases in concentrations of non-mercury trace elements in areas affected by artisanal mining over pre-industrial
mining concentrations were probably caused by increased rates of erosion.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
5.
To examine and compare historical accumulation of metal(loid)s in Mexican lakes and reservoirs, 210Pb and 137Cs dated sediment cores were evaluated: two from the remote Zempoala and Miramar Lagoons and three from Lake Pátzcuaro, and the Intermedia and Silva dams that are affected by human activities. Sediment ecotoxicology was assessed using consensus-based sediment quality guidelines for freshwater ecosystems. The +100 a sediment core from the remote Miramar Lagoon had the highest concentrations of Cr and Ni these being higher than the Probable Effect Levels (PELs). Zinc concentrations were also higher in the Miramar Lagoon compared to the other lakes and reservoirs, with concentrations higher than the Threshold Effect Level (TEL). Mercury concentrations from this lagoon were comparable to those for the Intermedia dam that receives water from urban, industrial and agricultural areas. The higher metal concentrations in the core from the Miramar Lagoon suggest that metal concentrations in the rocks of the watershed are high. Another explanation for the higher metal concentrations is the slow sediment accumulation that causes metals to be accumulated over longer time-periods at the sediment–water interface. A decrease in the concentration of As in the Intermedia dam was observed in sediments corresponding to the last decades. This may be due to an increase in sediment accumulation rate or to the reduction in sources of this metalloid in the watershed. In the Miramar Lagoon, an increase was observed in concentrations of As and Cr in more recent sediments, probably related to increased deforestation in the area or the eruption of El Chichonal volcano in 1982. Concentrations of Pb showed a decreasing tendency over the past decades in the Lake Pátzcuaro, Miramar and Zempoala Lagoons sediment cores while such behavior was not be observed for the Intermedia dam. This reduction in concentrations of Pb was attributed to the decrease in use of leaded gasoline. 相似文献
6.
Agustín Gómez-Alvarez Diana Meza-Figueroa Arturo I. Villalba-Atondo Jesús Leobardo Valenzuela-García Jorge Ramírez-Hernández Javier Almendariz-Tapia 《Environmental Geology》2009,57(7):1469-1479
The San Pedro River (SPR) is located in northern Sonora (Mexico) and southeastern Arizona (USA). SPR is a transboundary river
that develops along the Sonora (Mexico) and Arizona (USA) border, and is considered the main source of water for a variety
of users (human settlements, agriculture, livestock, and industry). The SPR originates in the historic Cananea mining area,
which hosts some of the most important copper mineralizations in Mexico. Acid mine drainage derived from mine tailings is
currently reaching a tributary of the SPR near Cananea City, resulting in the contamination of the SPR with heavy metals and
sulfates in water and sediments. This study documents the accumulation and distribution of heavy metals in surface water along
a segment of the SPR from 1993 to 2005. Total concentrations of Cd, Cu, Fe, Mn, Pb, and Zn in surface waters are above maximum
permissible levels in sampling sites near mine tailing deposits. Nevertheless, a significant decrease in the Fe and SO4
2− in surface water (SO4
2−: 7,180–460.39 mg/L; Fe: 1,600–9.51 mg/L) as well as a gradual decrease in the heavy and transition metal content were observed
during the period from 1994 to 2005. Approximately 2.3 km downstream of the mine tailings, the heavy metal content of the
water drops quickly following an increase in pH values due to the discharging of wastewater into the river. The attenuation
of the heavy metal content in surface waters is related to stream sediment precipitation (accompanied by metal coprecipitation
and sorption) and water dilution. Determining the heavy metal concentration led to the conclusion that the Cananea mining
area and the San Pedro River are ecosystems that are impacted by the mining industry and by untreated wastewater discharges
arising from the city of Cananea (Sonora, Mexico). 相似文献
7.
Sediment storage and severity of contamination in a shallow reservoir affected by historical lead and zinc mining 总被引:1,自引:0,他引:1
Kyle E. Juracek 《Environmental Geology》2008,54(7):1447-1463
A combination of sediment-thickness measurement and bottom-sediment coring was used to investigate sediment storage and severity
of contamination in Empire Lake (Kansas), a shallow reservoir affected by historical Pb and Zn mining. Cd, Pb, and Zn concentrations
in the contaminated bottom sediment typically exceeded baseline concentrations by at least an order of magnitude. Moreover,
the concentrations of Cd, Pb, and Zn typically far exceeded probable-effects guidelines, which represent the concentrations
above which toxic biological effects usually or frequently occur. Despite a pre-1954 decrease in sediment concentrations likely
related to the end of major mining activity upstream by about 1920, concentrations have remained relatively stable and persistently
greater than the probable-effects guidelines for at least the last 50 years. Cesium-137 evidence from sediment cores indicated
that most of the bottom sediment in the reservoir was deposited prior to 1954. Thus, the ability of the reservoir to store
the contaminated sediment has declined over time. Because of the limited storage capacity, Empire Lake likely is a net source
of contaminated sediment during high-inflow periods. The contaminated sediment that passes through, or originates from, Empire
Lake will be deposited in downstream environments likely as far as Grand Lake O’ the Cherokees (Oklahoma). 相似文献
8.
Michael Owor Tina Hartwig Andrew Muwanga Dieter Zachmann Walter Pohl 《Environmental Geology》2007,51(6):1065-1075
The abandoned Kilembe copper mine in western Uganda is a source of contaminants, mobilised from mine tailings into R. Rukoki
flowing through a belt of wetlands into Lake George. Water and sediments were investigated on the lakeshore and the lakebed.
Metal associations in the sediments reflect the Kilembe sulphide mineralisation. Enrichment of metals was compared between
lakebed sediments, both for wet and dry seasons. Total C in a lakebed core shows a general increment, while Cu and Co decrease
with depth. The contaminants are predominant (> 65%) in the ≤ 63 μm sediment size range with elevated Cu and Zn (> 28%), while
Ni, Pb and Co are low (< 18%) in all the fractions. Sequential extraction of Fe for lakeshore sediment samples reveals low
Fe mobility. Relatively higher mobility and biological availability is seen for Co, Cu and S. Heavy metal contents in lake
waters are not an immediate risk to the aquatic environment. 相似文献
9.
P. Conde Bueno E. Bellido J. A. Martín Rubí R. Jiménez Ballesta 《Environmental Geology》2009,56(5):815-824
Mercury (Hg) is one of the elements with increasing environmental significance. A total of 22 samples (soils, rocks and gels)
were collected along a 6 km transect around the Valdeazogues River valley in the southwest of the Iberian Peninsula (Almadén,
Spain). Samples were characterized by different soil types of depositional sequences associated with mining tailings, type
and system tracts: 15 surface soil samples included in the transect; 3 of a Haploxerept soil profile developed on slates;
2 of quartzite and slates rocks (reference rocks in the area). Moreover, two of a gel substance (in the lower tract of the
river). Soil samples were analyzed for Hg, Cu, Ni, Cr, V, Pb, Cd and As, as well as for organic matter, pH abrasion and calcium
carbonate content. All samples were collected from the Almadén mining district. The level of occurrence of the elements (especially
Hg) and the effect of some properties on its concentration distributions were investigated. The total mercury contents varied
in the range 7,315–3.44 mg kg−1. The mean concentration of total mercury in soils and rocks was 477.03 mg kg−1dry mass. This value is very high compared to the regional background value of other areas. Only rarely is it higher than
1%: in one sample (7,315 mg kg−1) it was almost eight times in comparison with the affected zones, with a high value of 1,000 mg kg−1. Significant differences between samples were found in the total content of mercury. A large percentage of the samples registered
detectable levels of V, Cr, Ni, Pb, As and Cu. Cd readings were below the detectable range for all samples tested. Cr mean
concentration was 216.95 mg kg−1 (minimun concentration 86, maximun 358); V mean concentration was 119.09 mg kg−1 (minimun concentration 69, maximun 1,209); As mean concentration was 51.24 mg kg−1 (minimun 13.3 and maximun 319.4); Ni mean concentration was 45.64 mg kg−1 (minimun concentration 21.2 and maximun 125.6); Cu mean concentration was 33.25 mg kg−1 (minimun concentration 19.3 and maximun 135); Pb mean concentration was 15.19 mg kg−1 (minimun 1.12 and maximun 1013). Metal distribution generally showed spatial variability ascribed to significant anthropogenic
perturbation by mining tailing type. Hg showed vertical profile characterized by surface enrichment, with concentrations in
the upper layer (93.7–82.2 mg kg−1 in front of 3.4 of the rock value) exceeding, in several occasions, the background value. The results obtained denote a potential
toxicity of some heavy metals in some of the studied samples. Water-soluble mercury could enter the aquatic system and accumulate
in sediments. Mercury and other heavy metals contamination depended on the duration and intensity of mining activities. 相似文献
10.
Shallow marine sediments of the Buyat-Ratototok district of North Sulawesi, Indonesia, are affected by submarine disposal
of industrial gold mine tailings and small-scale gold mining using mercury amalgamation. Industrial mine tailings contained
590–660 ppm arsenic, 490–580 ppm antimony, and 0.8–5.8 ppm mercury. Electron microprobe survey found both colloidal iron–arsenic-phases
without sulphur and arsenian pyrite in tailings and sites to which tailings had dispersed, but only arsenopyrite in sediments
affected by artisanal mining. Antimony in tailings was present as antimony oxides, colloidal iron–antimony phases, colloidal
iron–antimony phases, and stibnite in sediments affected by both types of mining. A sequential extraction found that 2% of
arsenic held in tailings and tailings-contaminated sediments was exchangeable, 20–30% was labile, including weakly adsorbed,
carbonate- and arsenate bound, 20–30% was metastable, probably incorporated into iron or manganese oxyhydroxides, or strongly
adsorbed to silicate minerals, and 40–48% was relatively insoluble, probably incorporated into sulphides or silicates. Arsenic
in sediments affected by artisanal gold mining was 75–95% relatively insoluble. Antimony in all sediments was >90% relatively
insoluble. Relative solubility patterns of most other metals did not differ between industrial tailings-affected, artisanal-mining
affected areas, and fluvial sediments. Results suggest that submarine tailings disposal is not suitable for refractory Carlin-like
gold deposits because ore processing converts arsenic to forms unstable in anoxic marine sediments.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
11.
Mercury (Hg) and methylmercury (CH3Hg+) concentrations in streambed sediment and water were determined at 27 locations throughout the Sacramento River Basin, CA. Mercury in sediment was elevated at locations downstream of either Hg mining or Au mining activities where Hg was used in the recovery of Au. Methylmercury in sediment was highest (2.84 ng/g) at a location with the greatest wetland land cover, in spite of lower total Hg at that site relative to other river sites. Mercury in unfiltered water was measured at 4 locations on the Sacramento River and at tributaries draining the mining regions, as well as agricultural regions. The highest levels of Hg in unfiltered water (2248 ng/l) were measured at a site downstream of a historic Hg mining area, and the highest levels at all sites were measured in samples collected during high streamflow when the levels of suspended sediment were also elevated. Mercury in unfiltered water exceeded the current federal and state recommended criterion for protection of aquatic life (50 ng/l as total Hg in unfiltered water) only during high streamflow conditions. The highest loading of Hg to the San Francisco Bay system was attributed to sources within the Cache Creek watershed, which are downstream of historic Hg mines, and to an unknown source or sources to the mainstem of the Sacramento River upstream of historic Au mining regions. That unknown source is possibly associated with a volcanic deposit. Methylmercury concentrations also were dependent on season and hydrologic conditions. The highest levels (1.98 ng/l) in the Sacramento River, during the period of study, were measured during a major flood event. The reactivity of Hg in unfiltered water was assessed by measuring the amount available for reaction by a strong reducing agent. Although most Hg was found to be nonreactive, the highest reactivity (7.8% of the total Hg in water) was measured in the sample collected from the same site with high CH3Hg+ in sediment, and during the time of year when that site was under continual flooded conditions. Although Hg concentrations in water downstream of the Hg mining operations were measured as high as 2248 ng/l during stormwater runoff events, the transported Hg was found to have a low potential for geochemical transformations, as indicated by the low reactivity to the reducing agent (0.0001% of the total), probably because most of the Hg in the unfiltered water sample was in the mercury sulfide form. 相似文献
12.
Mercury contribution to an adirondack lake 总被引:1,自引:0,他引:1
Elevated copper, lead, and zinc concentrations in the upper 10 to 20 cm of sediment sampled from Cranberry Lake, a large Adirondack
lake, are attributed to atmospheric contributions. Pb-210 and pollen core data, however, suggest Cranberry Lake also received
mercury discharges during the turn of the century when the area was the center of extensive lumbering and related activities.
Elevated mercury concentrations in Cranberry Lake smallmouth bass derived from remobilization from mercury-contaminated bottom
sediments which increased the bioavailability to Cranberry Lake organisms. Mercury remobilization and accumulation by fish
are promoted by fluctuating pH values resulting from acid precipilation. 相似文献
13.
A lake sediment core from Vermillion Lake, Sudbury, Ontario was tightly sampled and analyzed for a wide range of trace elements as well as for Pb isotopes. The data resolve multiple historical events in the 140-a history of logging and mining in the Sudbury area in unprecedented detail. Lead-210 data, 137Cs activity and historical information on the start of anthropogenic activities in the Sudbury area were combined to derive an age model for the sedimentary column. Using the age information, it is possible to identify sediment sections enriched and depleted in trace metal(loid)s, particularly Ni and Cu, the two most relevant metals in the Sudbury area. Maxima and minima in the chronology of Ni and Cu coincide well with local production values for both elements until environmental regulations in the 1990s resulted in a decrease in their emission and drainage into Vermillion Lake. Differences in the deposition rates of Ni and Cu, trace-metal distribution patterns throughout the sedimentary column, Pb-isotope data, and comparison with data for local rocks and ores in the Sudbury area were used to identify the sources of pollutants in the early and late periods of mining activities. In addition, the environmental impact on the sediment itself was also studied via the variation of water content and organic matter. Finally, a surficial Fe–Mn-enriched layer with elevated concentrations of the oxy-anions (PO4)3−, (AsO4)4−, and (MoO4)2− was identified. This can be distinguished from accumulation of Zn and an increase in the Y / Ho ratio in the upper core sections, which likely imply increasing drainage of fertilizers into the Vermillion River watershed. The chemistry, mineralogy, and isotope composition of the Vermillion Lake sediment column thus contain a very detailed >140-a account of initial severe anthropogenic disturbance, the efforts of remediation and the effects of changing land use towards agricultural and recreational activities. 相似文献
14.
The Tinto and Odiel rivers drain 100 km from the Rio Tinto sulphide mining district, and join at a 20-km long estuary entering the Atlantic Ocean. A reconnaissance study of heavy metal anomalies in channel sand and overbank mud of the river and estuary by semi-quantitative emission dc-arc spectrographic analysis shows the following upstream to downstream ranges in ppm (μg g?1): As 3,000 to <200, Cd 30 to <0.1, Cu 1,500 to 10, Pb 2,000 to <10, Sb 3000 to <150, and Zn 3,000 to <200. Organic-rich (1.3–2.6% total organic carbon, TOC), sandysilty overbank clay has been analyzed to represent suspended load materials. The high content of heavy metals in the overbank clay throughout the river and estuary systems indicates the importance of suspended sediment transport for dispersing heavy metals from natural erosion and anthropogenic mining activities of the sulfide deposit. The organic-poor (0.21–0.37% TOC) river bed sand has been analyzed to represent bedload transport of naturally-occurring sulfide minerals. The sand has high concentrations of metals upstream but these decrease an order of magnitude in the lower estuary. Although heavy metal contamination of estuary mouth beach sand has been diluted to background levels estuary mud exhibits increased contamination apparently related to finer grain size, higher organic carbon content, precipitation of river-borne dissolved solids, and input of anthropogenic heavy metals from industrial sources. The contaminated estuary mud disperses to the inner shelf mud belt and offshore suspended sediment, which exhibit metal anomalies from natural erosion and mining of upstream Rio Tinto sulphide lode sources (Pb, Cu, Zn) and industrial activities within the estuary (Fe, Cr, Ti). Because heavy metal contamination of Tinto-Odiel river sediment reaches or exceeds the highest levels encountered in other river sediments of Spain and Europe, a detailed analysis of metals in water and suspended sediment throughout the system, and epidemiological analysis of heavy metal effects in humans is appropriate. 相似文献
15.
Tidal freshwater marshes exist at the interface between watersheds and estuaries, and thus may serve as critical buffers
protecting estuaries from anthropogenic metal pollution. Bi-weekly samples of newly deposited marsh sediments were collected
and analyzed for Cu, Zn, and Fe concentrations over 21 months from July 1995 to March 1997 in five distinct habitats at the
head of Bush River, Maryland. Bi-weekly anthropogenic metal enrichments ranged from 0.9–4.7. Anthropogenic excess metal loadings
averaged over 1996 ranged from 6–306 and 25–1302 μg cm−2 year−1 between sites for Cu and Zn, respectively. Based on Fe-normalized trace metal signatures, Susquehanna River sediment does
not significantly contribute to upper Bush River. Organic matter was found to dilute total metal concentrations, whereas past
studies suggested organics enhance labile metal content. Analysis of metal input pathways shows that marsh metals are primarily
imported from nearby subtidal accumulations of historic watershed material by tidal flushing.
Received: 29 April 1999 / Accepted: 7 December 1999 相似文献
16.
Previous studies in the Amazon Basin and the Upper Pantanal show widespread mercury contamination of fish and water as a result
of gold mining, and subsequent volatilization of mercury during the recovery process. A study was initiated to assess whether
atmospheric transport of mercury to the south has resulted in elevated levels in water and fish in the Lower Pantanal. Water
samples were collected from streams and rivers from the Pantanal (Mato Grosso do Sul) down into the southernmost state of
Brazil (Rio Grande do Sul) for total Hg concentration and oxygen isotopic analyses. Based on oxygen isotopes and conductivity,
surface water samples can be considered as mixtures of three endmembers: groundwater, rain and “aged” surface water. Lowest
concentrations (<2 ng/L) of total Hg were observed in the northernmost samples, especially those associated with the groundwater
sources. Further south, Hg concentrations tended to increase, but higher concentrations (>2 ng/L) likely reflect direct input
from more localized watershed sources. Fish collected from streams in the Pantanal had extremely low concentrations of total
Hg regardless of their size or feeding habit, although one large carnivorous fish (>2 kg) had concentrations approaching 400 ng/g
wet wt. All concentrations, however, were considerably lower than those observed in similar species from the region of the
Amazon Basin affected by gold mining. 相似文献
17.
Ben K. Odhiambo Virginia Brown Gayle Armentrout Leanna C. Giancarlo Chelsea Wegner 《Environmental Earth Sciences》2013,69(6):2103-2117
Damming of the North Anna River in 1972 created Lake Anna, a cooling water source for the Dominion nuclear power plant as well as a popular recreation site in Spotsylvania and Orange counties, Virginia, USA. Previously dated (210-Pb) sediment cores from seven locations within the lake and three locations in the adjoining Waste Heat Treatment Facilities (WHTF) were analyzed for trace metals (Al, Ba, Zn, Cd, Cu, Fe, Mn and Pb) and polychlorinated biphenyls (PCBs) to examine the environmental evolution of the reservoir system. The reservoir has a history of mining activities in its watershed and unusually elevated concentrations of PCBs were found in fish tissues from previous studies. Therefore, dated sediment cores provided the framework for both the temporal and spatial analysis of possible sources and flux histories for both trace metals and PCBs. The trace metals results suggest that, though the upper reaches are relatively less impacted, the old mine tailings from the now ceased mining activities in the watershed of Contrary Creek tributary continue to dominate the sediment chemistry of the lower portion of the lake basin, signified by sediment enrichment of Pb, Cd, Cu, and Zn. Lagoon-2 of the WHTF also seems to be receiving unusually high loadings of Cd (12.5 ± 1.07 μg/g) that is probably associated with waste materials from the nuclear power plant that maintains the lagoons. PCB sediment concentrations were relatively low in the lower sections of the basins with values typically being <3.5 ng/g. The upper reaches of the basin had several PCB hotspots, with the surface sediments of Terry’s Run tributary having values as high as 53.13 ng/g. The spatial distribution of PCBs seems to suggest the upper reaches of the basin as the probable source, with the unusually high concentrations near bridges suggesting a possible link between the PCBs and old bridge fill materials. The oldest lacustrine sediments also had relatively high trace metals and PCB values signifying a probable role of soil disruption and sediment reconcentration during reservoir construction. 相似文献
18.
Recent Lake Tanganyika Hg deposition records were derived using 14C and excess 210Pb geochronometers in sediment cores collected from two contrasting depositional environments: the Kalya Platform, located mid-lake and more removed from watershed impacts, and the Nyasanga/Kahama River delta region, located close to the lake’s shoreline north of Kigoma. At the Kalya Platform area, pre-industrial Hg concentrations are 23 ± 0.2 ng/g, increasing to 74 ng/g in modern surface sediment, and the Hg accumulation rate has increased from 1.0 to 7.2 μg/m2/a from pre-industrial to present, which overall represents a 6-fold increase in Hg concentration and accumulation. At the Nyasanga/Kahama delta region, pre-industrial Hg concentrations are 20 ± 3 ng/g, increasing to 46 ng/g in surface sediment. Mercury accumulation rate has increased from 30 to 70 μg/m2/a at this site, representing a 2–3-fold increase in Hg concentration and accumulation. There is a lack of correlation between charcoal abundance and Hg accumulation rate in the sediment cores, demonstrating that local biomass burning has little relationship with the observed Hg concentration or Hg accumulation rates. Examined using a sediment focusing-corrected mass accumulation rate approach, the cores have similar anthropogenic atmospheric Hg deposition profiles, suggesting that after accounting for background sediment concentrations the source of accumulating Hg is predominantly atmospheric in origin. In summary, the data document an increase of Hg flux to the Lake Tanganyika ecosystem that is consistent with increasing watershed sediment delivery with background-level Hg contamination, and regional as well as global increases in atmospheric Hg deposition. 相似文献
19.
Alain Plouffe 《Environmental Geology》1998,33(2-3):183-196
Abundant cinnabar (HgS) mineralization is associated with the Pinchi Fault in central British Columbia. Two formerly producing
mercury mines have been developed on this fault: Pinchi and Bralorne Takla. The mercury content of till (a sediment type directly
deposited by glaciers) in the area of this fault is primarily controlled by the occurrence of cinnabar mineralization in bedrock
and the direction of ice flow. Cinnabar-bearing bedrock was eroded by glaciers, transported in the direction of ice flow,
and deposited "down-ice" from its source. An example of such a dispersal train is documented for the Pinchi Mine area where
mercury ore was transported over a distance of 12 km, as measured in the clay-sized fraction (< 0.002 mm) of till, and could
have been transported over 24 km according to heavy mineral concentrates (specific gravity >3.3) of this same sediment. Antimony,
chromium, and nickel dispersal trains were also detected in the region. These data indicate that natural glacial processes
can result in the "mobilization" of metals in the surficial environment, a factor which has to be considered at mine sites
in glaciated terrain, where mine reclamation and remediation measures are now required.
Received: 31 October 1996 · Accepted: 27 May 1997 相似文献
20.
Application of allochthonous organic carbon and phosphorus forms in the interpretation of past environmental conditions 总被引:2,自引:0,他引:2
Changwei Lü Jiang He Huimin Sun Hongxi Xue Ying Liang Saruli Bai Ying Sun Lili Shen Qingyun Fan 《Environmental Geology》2008,55(6):1279-1289
Organic matter in sediments, for instance, carbon, nitrogen and phosphorus, can be used to reconstruct the paleoecological
and pollution history of lakes and their catchment basins. In this paper, the contents of allochthonous organic carbon (allochthonous
OC) and autochthonous organic carbon (autochthonous OC) in sediment cores taken from Wuliangsuhai Lake and Daihai Lake in
northern China are quantified by using a binary model, and phosphorus forms in the sediment cores from the two lakes are extracted
by sequential extraction techniques. The results indicate that the palaeoenvironment and paleoclimate of Daihai Lake and
its catchment basin in the recent 250 years can be well reconstructed based on the content of allochthonous OC. The climate
was relatively humid and warm in the period of 1865–2005, while relatively dry and cold in the period of 1765–1865. The sedimentary
information of allochthonous OC in the 22–42-cm portion of the sediment cores in Daihai Lake corresponds to the final cold
fluctuation of the Little Ice Age that occurred since the Middle Holocene. The difference of phosphorus forms in the sediment
cores between the two lakes indicates that phosphorus input to the lakes and the correlation between phosphorus forms and
distribution and the changes of environment are influenced by the eutrophication mechanisms and environmental conditions of
the two lakes. 相似文献