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71.
The primary factors that control the concentration of total reduced (inorganic) sulfide in coastal sediments are believed
to be the availability of reactive iron, dissolved sulfate and metabolizable organic carbon. We selected nine sites in shallow
(<3 m), close to sub-tropical, estuaries and bays along the central Texas coast that represented a range in sediment grain
size (a proxy for reactive iron), salinity (a proxy for dissolved sulfate), and total organic carbon (a proxy for metabolizable
organic carbon). Based on these parameters a prediction was made of which factor was likely to control total reduced sulfide
at each site and what the relative total reduced sulfide concentration was likely to be. To test the prediction, the sediments
were analyzed for total reduced sulfide, acid volatile sulfide, and citrate dithionate-extractable, HCl-extractable and total
Fe in the solid phase. Using solid-state gold–mercury amalgam microelectrodes and voltammetry, we determined pore water depth
profiles of Fe(II) and ΣH2S and presence or absence of FeS(aq). At five of the nine sites the calculated degree of sufildization of citrate dithionite-reactive-iron was close to or greater
than 1 indicating that rapidly reactive iron was probably the limiting factor for iron sulfide mineral formation. At one site
(salinity = 0.9) dissolved Fe(II) was high, ΣH2S was undetectable and the total reduced sulfide concentration was low indicating sulfate limitation. At the last three sites
a low degree of sulfidization and modest total reduced (inorganic) sulfide concentrations appeared to be the result of a limited
supply of metabolizable organic carbon. Fe(II)–S(-II) clusters (FeS(aq)) were undetectable in 10 out of 12 bay sediment profiles where ΣH2S was close to or below detection limits, but was observed in all other porewater profiles. Acid volatile sulfide, but not
total reduced sulfide, was well correlated with total organic carbon and ranged from being undetectable in some cores to representing
a major portion of total reduced sulfide in other cores. Although predicted controls on total reduced sulfide were good for
very low salinity water or sandy sediments, they were only right about half the time for the other sediments. The likely reasons
for the wrong predictions are the poor correlation of total organic carbon with grain size and differing fractions of metabolizable
organic carbon in different sedimentary environments. Differences in sediment accumulation rates may also play a role, but
these are difficult to determine in this region where hurricanes often resuspend and move sediments. This study demonstrates
the need to examine more complex and often difficult to determine parameters in anoxic “normal marine” sediments if we are
to understand what controls the concentration and distribution of sulfides. 相似文献
72.
The potential application of bio‐based ester oils for use as lubricants in metal working has been investigated for sustainable production processes in the future. When waste edible and animal fats came into focus as starting materials, it was already proven, that ester oils produced from plant fats performed very well as cooling lubricants. Waste fats were first characterized by analyzing and monitoring samples for one complete year. Inorganic and organic contaminations were found to be low and without seasonal variations. Fatty acid methyl esters (FAME) were produced by transesterification of the waste fats and they were separated into fractions with saturated FAME or unsaturated FAME by fractional crystallisation (winterisation). Further transesterification with 2‐ethylhexanol led to products that could be successfully tested as lubricants. The development of an extraction process aimed at the recycling of oil containing grinding mud by enabling the recirculation of lubricating oil and reutilization of oil‐free metal chips. 相似文献
73.
Trace metals in acid sediments and waters, Pimpama catchment, southeast Queensland, Australia 总被引:2,自引:1,他引:2
The Pimpama River floodplain has developed over the last several thousand years as a result of sea-level fluctuations that
shaped the lower catchment and enabled the formation of sedimentary pyrite. The subsequent production of sulfuric acid due
to the oxidation of this pyrite enhances the breakdown of metal-bearing sediments and can lead to leaching of major and trace
metals into the waters of the region. The seasonal pattern of rainfall and current land-use activities are important aspects
that intensify the natural production of acid and influence the release and distribution of metals. To identify the source
and migration of metals in the Pimpama catchment and to understand the impact of pyrite oxidation on the distribution of metals
in sediments and waters, several components of the drainage system were analyzed: bedrock, sediments from river bed and bank,
and water. The elements analyzed in this study (V, Cr, Co, Ni, Cu, Zn and Pb) are all present in the bedrock material which
explains their occurrence in the unconsolidated sediments of the floodplain. These metals concentrate in the upper section
of the sedimentary sequence and their presence is related to clay minerals such as smectite, organic matter and iron phases.
However, Zn, Mo and Co occur in higher amounts than the local background and within standard shale. This comparison suggests
that the diagenetic processes alone cannot explain the higher concentrations and it is concluded that these metals also have
an anthropogenic source. The formation of sulfuric acid creates conditions for higher mobility of some metals, such as Cr,
Co, Ni, Cu, Zn, but does not affect less mobile ones such as Mo and Pb. Over the longterm, the production of acid influences
the breakdown of mineral phases and enhances the process of weathering. Over the short term, every rain event leaches acid
from sediments and mobilizes metals resulting in a substantial reduction in the quality of river water.
Received: 2 October 1998 · Accepted: 16 February 1999 相似文献
74.
Yearly changes in the seasonal frequency and duration of short-term acid pulses in some Nova Scotia, Canada streams 总被引:1,自引:0,他引:1
The seasonal frequency and duration of low pH events at three sites located in southwestern Nova Scotia were analyzed using
measured and synthetic daily pH data. The basins varied in size from 0.3 to 300 km2 and were subject to frequent snowmelt events in winter and spring, as well as occasional runoff events during summer and
fall. Results showed that, in order to fill in missing data from periods where collection was interrupted, statistical approximations
using discharge were not totally acceptable, as generated data consistently missed the extreme values measured. Despite a
lack of totally accurate event pH estimates for periods where daily data were missing, analysis showed that in this region,
low pH episodes can occur year-round including summer. The highest probabilities of low pH episodes nevertheless occurred
in the winter and spring when snowmelts were frequent.
Received: 12 November 1999 · Accepted: 18 July 2000 相似文献
75.
Controls on the nature and distribution of an alga in coal mine-waste environments and its potential impact on water quality 总被引:2,自引:0,他引:2
A dominant non-bacterial microorganism that may strongly impact environmental conditions in acid mine drainage at several
Indiana coal mine sites is a single-celled protozoan, Euglena mutabilis. Field data suggest E. mutabilis has high tolerance for elevated total dissolved solids (TDS), to 18 g/l, and acid conditions to pH 1.7. Distribution is restricted
to unmixed effluent pH<4.6, with prolific growth between pH 3.0 and 3.5. Additional factors influencing E. mutabilis include preference for areas with lower mineral/colloidal precipitation rates and a stable substrate of iron-rich precipitates.
Initial studies indicate that in areas of prolific growth it contributes to oversaturation of dissolved oxygen by up to 200%.
The presence of small orange intracellular crystalline-like structures, similar in color to iron oxyhydroxides, suggests that E. mutabilis may be sequestering iron, and possibly other metals. Further work is needed to determine if E. mutabilis contributes to natural mitigation of poor water quality at these and other coal mine sites.
Received: 13 January 2000 · Accepted: 2 May 2000 相似文献
76.
Partitioning of heavy metals on soil samples from column tests 总被引:3,自引:0,他引:3
R. N. Yong W. Z. W. Yaacob S. P. Bentley C. Harris B. K. Tan 《Engineering Geology》2001,60(1-4):307-322
In this study, column tests were used to determine the retention capability of three types of estuarine alluvia collected adjacent to landfill sites in South Wales. Selective sequential extraction (SSE) was used to study the retention mechanisms of heavy metals in the soil columns obtained from leaching experiments. Acid digestion was later used to check the validity of the SSE results. Breakthrough curves show good retention of heavy metal ions (Pb, Cu, and Zn) by all soils, where almost 99% of heavy metals were retained with the Ce/Co values in the order of 10−3. The retention strength of these soils was observed to be constant up to five pore volumes (PV). This corresponds with the pH of the effluents and pore water of soil slices, which also show good buffering capacity against very acidic leachate up to 5PV. The heavy metal extraction profiles from SSE show very similar trends with the retention profiles from the leaching experiments, where heavy metals were retained mainly at the top part where the leachate entered the column. SSE indicates qualitatively that heavy metals precipitated with carbonates and amorphous materials (oxides/hydroxides) are higher than heavy metal retention via exchangeable mechanisms. The mass balance calculation gives range of deviation of 1–16% of the total soil extraction. The distribution of the heavy metals with various soil constituents are ranked in the following order: Carbonates>Amorphous oxides hydroxides>Organic matter>Exchangeable phases. 相似文献
77.
为研究滇黔桂卡林型金矿区水系沉积物和岩石中金的地球化学时空分布及其与金矿规模的对应关系,系统收集了该区1:20万区域化探全国扫面计划水系沉积物和全国地球化学基准计划岩石金的地球化学数据,绘制了水系沉积物和岩石金的地球化学分布图。滇黔桂卡林型金矿区以水系沉积物金地球化学异常面积大于1000 km^2为准,共圈定5处金的地球化学省,这些金的地球化学省同时也是矿床大规模产出的部位。区内右江盆地水系沉积物金背景值(1.94×10^–9)高于扬子克拉通(1.68×10^9),其内以泥岩、页岩、砂岩、灰岩为代表的容矿岩石金背景值(0.51×10^–9)也高于扬子克拉通(0.39×10^–9)。研究区不同构造单元及沉积相中水系沉积物金背景值受岩石金背景值的制约。金的地球化学省是地壳演化过程中不均匀分布的高金背景岩石、金矿化作用及金矿床次生风化作用相互叠加的结果。该研究有助于有效判断异常成因、识别成矿作用存在,对研究金的区域成矿规律和聚焦找矿靶区具有重要意义。 相似文献
78.
You YI Zhaonan CAI Yi LIU Shuangxi FANG Yuli ZHANG Dongxu YANG Yong WANG Miao LIANG Maohua WANG 《大气科学进展》2020,37(6):608-616
The balloon-borne Aircore campaign was conducted in Inner Mongolia,China,on June 13 and 14 2018,which detected carbon dioxide(CO_2) and carbon monoxide(CO) profiles from surface to 24 km,showing strong positive and negative correlations between 8 km and 10 km on 13 and 14 June,respectively.Backward trajectories,meteorological analyses,and CO_2 horizontal distributions were combined to interpret this phenomenon.The results indicated that the source region experienced a stratospheric intrusion and exhibited a large horizontal CO_2 gradient;namely,lower CO concentrations corresponded to higher CO_2 concentrations and vice versa.The laminar structure with multiple origins resulted in the highly negative correlation between CO_2 and CO in the upper troposphere on 14 June.The contribution of stratospheric air mass to the upper troposphere and that of tropospheric air mass to the lower stratosphere were 26.7% and24.3%,respectively,based on a mass balance approach.Another interesting phenomenon is that CO_2 and CO concentrations increased substantially at approximately 8 km on 13 June.An analysis based on the backward trajectory implied that the air mass possibly came from anthropogenic sources.The slope of CO_2/CO representing the anthropogenic sources was 87.3 ppm ppm~(-1).In addition,the CO_2 profile showed that there was a large CO_2 gradient of 4 ppm km-1 within the boundary layer on 13 June,and this gradient disappeared on 14 June. 相似文献
79.
S. T. Trudgill 《水文研究》1987,1(2):149-170
Three fluorescent dyes (Rhodamine WT, Lissamine FF and Amino G Acid) are compared for use in soil water tracing. Severe limitations are evident, but practical applications are possible. Background fluorescence, adsorption, desorption, pH and other non-adsorptive effects are reviewed in the contexts of soil column work and field tracing of soil water. Lissamine FF and Amino G Acid are to be preferred for soil column work because of their lower adsorption; Rhodamine WT exhibits higher adsorption but is useful in field situations where organic fluorescence backgrounds are high. Semi-quantitative work may be undertaken in soil columns once a priming and flushing procedure has been adopted. 相似文献
80.
Jane?M.?HammarstromEmail author Robert?R.?SealII Allen?L.?Meier John?C.?Jackson 《Environmental Geology》2003,45(1):35-57
Metal cycling via physical and chemical weathering of discrete sources (copper mines) and regional (non-point) sources (sulfide-rich shale) is evaluated by examining the mineralogy and chemistry of weathering products in Great Smoky Mountains National Park, Tennessee, and North Carolina, USA. The elements in copper mine waste, secondary minerals, stream sediments, and waters that are most likely to have negative impacts on aquatic ecosystems are aluminum, copper, zinc, and arsenic because these elements locally exceed toxicity guidelines for surface waters or for stream sediments. Acid-mine drainage has not developed in streams draining inactive copper mines. Acid-rock drainage and chemical weathering processes that accompany debris flows or human disturbances of sulfidic rocks are comparable to processes that develop acid-mine drainage elsewhere. Despite the high rainfall in the mountain range, sheltered areas and intermittent dry spells provide local venues for development of secondary weathering products that can impact aquatic ecosystems.Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.
相似文献
Jane M. HammarstromEmail: Phone: +1-703-6486165Fax: +1-703-6486252 |