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1.
The aim of this investigation was to study the temporal variation in phosphorus release from the sediments and its influence on water quality of stratified lakes. The concentrations of soluble reactive phosphorus (SRP), calcium and sulfate in the interstitial water and the pH in the wet sediments of dimictic lakes were investigated during the spring circulation and at the end of summer stratification. Multiple regression analysis using the calculated diffusive fluxes of SRP out of the sediments and the morphometric characteristics of the lakes (reduced water depth), explained 73 % of the variance of the SRP-accumulation in the hypolimnia during summer stagnation. At the end of surnmer stratification diffusive fluxes of SRP out of the sediments increased and pH-values and sulfate-concentrations decreased at the sediment surface (0–2 em) and in the hypolimnia. The maximum diffusive flux of SRP was calculated to be 5.8 mg/m2/d at the end of summer stagnation. Prob able reasons for these higher diffusive fluxes of SRP at the end of summer stagnation are higher supply of labile organic matter and thereby higher mineralization rates. lower redox potential and thus higher dissolution of redox sensitive P-binding forms and/or dissolution of phosphorus being bound to Ca-phases at lower pH.  相似文献   

2.
Purpose

To explore the mechanisms in the deposition and release of phosphorus (P) in the sediment of a shallow eutrophic lake using preserved samples, we investigated the vertical and temporal changes in P, manganese (Mn), sulfur (S), iron (Fe), aluminum (Al), calcium (Ca), and magnesium (Mg) in the sediment samples and the phosphate in the sediment pore water samples over a period of 6 years.

Materials and methods

The upper 15 cm of sediment from Lake Kasumigaura in Japan was collected monthly from 2003 to 2008 from the center of the lake. Sediment cores were divided into seven depth segments and were acid-digested for an elemental analysis via inductively coupled plasma atomic emission spectroscopy. Phosphate concentrations of the sediment pore water were determined using the molybdenum blue method. A multiple regression analysis was conducted by setting the P content as the response variable and Mn, S, Fe, Al, Ca, and Mg as explanatory variables.

Results and discussion

The results of the multiple regression analysis demonstrated that P co-precipitates with Fe and Al oxides and accumulates on the sediment surface. The vertical distributions of Mn and S suggest that Mn reduction occurs within the 0–1-cm-depth layer of the sediment and that iron sulfide is actively formed in the 6–10-cm-depth layer of the sediment. These findings imply that the layer in which ferric oxides are reduced to ferrous ions is present near the 1–6-cm-depth layer of the sediment. This layer corresponds to the layer in which the maximum phosphate concentration of the sediment pore water often occurred (the 2–6-cm-depth layer). These results indicate that vertical distributions of mineral elements are useful for assessing P dynamics in sediments.

Conclusions

The lake sediments record the dynamics of P in the sediment. Our analytical approach using long-term observation data demonstrated that the accumulation and release of P associated with a change in the redox state can be assessed based on the vertical distributions of mineral elements in the lake sediments.

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3.
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.  相似文献   

4.
The objective of this study was to verify in which way the ionic composition of the sediment and that of the overlying water column may have an effect on radiocaesium fixation, through possible structural modifications of the frayed edge sites (FES) pools of the sediments. Two experimental protocols have been considered: i) a condition in which sediments were homoionically saturated with either potassium, ammonium, calcium, magnesium or sodium ions. and ii) a mixed potassium-calcium scenario in the liquid phase. Nine freshwater sediments from four different locations were used in this study. For homoionic potassium and ammonium saturated sediments a nearly quantitative radiocaesium desorption (90–100%) was observed, whereas for calcium and magnesium the desorption yields scene about 20%. It appears that the action of strongly hydrated ions (Na+, Mg2+, Ca2+) leads to a pronounced enhancement of radiocaesium fixation in the solid phase, whereas poorly hydrated ions (K+, NH4 +) have the opposite effect and promote sorption reversibility. Another issue considered in this study concerns the effect of temperature and sediment drying on the radiocaesium fixation. Drying die sediments at 110°C leads to a significant increase in radiocaesium fixation levels, while drying the sediments at room temperature (25°C) has a very limited effect on radiocaesium fixation and appears to put a brake on the aging effects.  相似文献   

5.
Experiments conducted on selected minerals and headwater lake sediments showed that major acid neutralization reactions above pH 4.5 were reactions releasing Ca2+ and Mg2+ from the sediments. Analysis of the sediments and water from 97 headwater lakes in northern Ontario showed a predictable decrease in the exchangeable Ca+ Mg2+ of the sediments with decreasing lakewater pH. Estimates of the total potential buffering capacity for the sediments above PH 4.5 and for water in these headwater lakes were made, and it was found that, even when only the top 1 cm of sediment is considered, a substantial sediment buffering reserve is available.  相似文献   

6.
An intensive survey of mercury speciation was performed at a site on the Upper St. Lawrence River near Cornwall, Ontario, Canada with a history mercury contamination in sediments. Surface sediments were collected every 1.50 h. Total mercury (Hgtotal), methylmercury (MeHg), organic carbon, inorganic and organic sulphur were determined in the solid fraction. Dissolved Hgtotal, MeHg and dissolved organic carbon (DOC) were measured in pore waters. Concentrations of Hgtotal in the upper layers (first 5 cm) were high, ranging from 1.42 to 25.8 nmol g?1 in solids and from 125 to 449 pM in pore waters. MeHg levels were also high, ranging from 4.34 to 34.1 pmol g?1 in solids and from 40 to 96 pM in pore waters. This amounts to up to 1.4% of Hgtotal present as MeHg in solids and 64% in pore waters. A daily pattern for Hgtotal was observed in the solid fraction. The MeHg distribution in solids and pore waters was not correlated with Hgtotal or DOC, suggesting that the concentrations of MeHg are probably more influenced by the relative rates of methylation/demethylation reactions in the sediment–water interface. Acid volatile sulphide levels and DOC were inversely correlated with organic sulphur (Sorg) levels suggesting that both parameters are involved in the rapid production of Sorg. A positive correlation was also observed between Hgtotal and Sorg in solids (R?=?0.87, p?<?0.01) illustrating the importance of organic sulphur in the retention and distribution of Hg in the solid fraction of the sediments. The results suggest that variations of Hgtotal concentrations in Upper St. Lawrence River surface sediments were strongly influenced by the formation/deposition/retention of organic sulphur compounds in the sediment–water interface.  相似文献   

7.
Interstitial water profiles in epilimnetic sediments of lakes with varying water column alkalinities were collected to assess the origin and importance of sedimentary alkalinity in freshwater lakes. Release of Ca2+ and NH4 +, and consumption of SO4 ? are the most important contributors to alkalinity production m sediments of non-acidic lakes. In acidic lakes, Fe2+ and Mn2+ replace Ca2+ as the dominant cation contributors to alkalinity production. The sedimentary alkalinity flux is an important component of the acid neutralizing capacity of freshwater lakes. However, the presence of large alkalinity gradients in sediment porewaters does not necessarily indicate a large source of alkalinity for the lake, as a significant portion of the alkalinity iu associated with the formation of Fe2+, Mn2+ and NH4 + Oxidation of Fe2+ and Mn2+ at the anoxic-oxic interface and biological removal of NH4 + in the overlying water column results in consumption of the co-diffusing alkalinity.  相似文献   

8.
Nitrate reduction to NH4+ and incorporation into organic matter was investigated in sediment-water systems composed of a 2.4-cm layer of estuarine sediment covered by 2 cm of water. Between 15 and 28% of the 15N-labelled NO3? added to the sediment or floodwater of the systems was recovered as NH4+ and organic N. The results indicated that NO3? was reduced to NH4+ by a dissimilatory mechanism. A separate experiment examined the influence of redox potential (+300, 0 and ?200 mV) on NO3? reduction in sediment suspensions maintained at pH 7.5. Conversion of NO3? to NH4+ and organic N increased markedly with decreasing redox potential. The results suggested that although the reaction accounted for 35–42% of the NO3? reduced under intensely-reduced conditions (?200 mV), the significance of the reaction in nature was dependent upon NO3? movement into zones sufficiently reduced for reduction of NO3? to NH4+ instead of denitrification. Under conditions in which NO3? moved downward through a sediment-water column into a reduced sediment zone approximately 15% of the NO3? was reduced to NH4+ and recycled in the sediment.  相似文献   

9.
[目的]通过对滨海地区盐碱土水盐动态变化规律的研究,为该地区的土壤利用以及植树造林提供科学依据。[方法]以天津大港地区刺槐林土壤为研究对象,研究不同土层的土壤水盐年份变化和盐分离子分布特征。[结果]试验地土壤全年含水量变化范围在11.9%~28.8%;含盐量变化范围在4.2%~18.4%。春(3—5月)秋(9—11月)季节土壤含水量低,含盐量高,土壤盐分含量随土层深度增加逐渐降低;夏季(6—8月),土壤含水量高,含盐量低,土壤盐分含量随土层深度的增加逐渐升高。pH值在7.37~8.39之间,土壤中K+,Na+,Ca2+,Mg2+和Cl-春季表层土壤(0—10cm)含量最高,分别为0.04,4.27,2.69,1.04和10.03g/kg。除SO2-4和HCO-3外,其他盐分离子在春季变异系数(29.99~162.98)明显大于夏秋季节(2.87~88.13)。[结论]不同土层的土壤含水量和含盐量随当地降雨量呈明显的季节性变化;试验地区土壤属于碱性土壤,随季节变化不明显;K+,Na+,Ca2+,Mg2+和Cl-与含盐量变化趋势保持一致,SO2-4和HCO-3随季节变化没有明显的规律性;春季各盐分离子在土壤中分布极为不均。  相似文献   

10.
Acid rain impacts on the small forested watershed in northern Tama Hills in the western Tokyo metropolitan area Japan were investigated by surveying the trends of major inorganic species in rain and spring water during the years from 1991 to 1997. The ecosystem had been stressed by the annual H+-deposition of around 0.43 kmol/ha. The spring water outflow corresponded to ca. 27% of the precipitation. Budgets for the precipitation input and spring water output gave good balance for Cl?,?0.01 ±0.09 kmol/ha, net gains for H+, NO3 ? and SO4 2?, and to the contrary, relatively large net losses for Na+, Mg2+, Ca2+, Si(as H4SiO4) and HCO3 ?, thus suggesting the dissolution of chemical weathered products of silicate minerals. Further, in spring water, some concentration relationships were found: CNa+ = 376.5?2.05CCl? (R2=0.748), CNa+=12.69+0.5556CHCO3 ? (R2=0.872) and CH4SiO4=130.0 + 1.108CHCO3 ? (R2=0.816). Evidently, the spring water chemistry reflected probable geochemical changes in the soil layer of the watershed. Mass balance in the ecosystem and estimation of the spring water output of chemical weathered products were investigated  相似文献   

11.
Pyrite and siderite oxidation in swamp sediments   总被引：3，自引：0，他引：3  
Differences in the processes of pyrite and siderite oxidation, in reclaimed swamp sediments of the Skjernå delta (Denmark), are described from sediment chemistry, mineralogy and pore water chemistry. Pyrite oxidation leads to extreme soil acidification, with pH dropping to about 2, the release of large amounts of weathering products to the pore water, and the precipitation ofiron oxides, jarosite and gypsum. Siderite oxidation results only in moderate soil acidification where the pH does not drop below 3.5, while part of the acidification is due to the oxidation of small amounts of sulphur compounds together with siderite. The release of weathering products to the pore water is limited and only iron oxide is precipitated. Calculations indicate that equilibrium with amorphous FeOOH, gypsum and amorphous Al(OH)3 sets an upper limit to the Fe3+, SO4 and Al concentrations in the pore water.  相似文献   

12.

Purpose

Stormwater discharges include contaminated sediments that accumulate in the receiving water body. It is thus important to investigate sediment and pollutant processes and pathways from the catchment to, and within, the receiving water. These processes may be influenced by seasonal changes. The objective of this study was to investigate the stormwater impact on receiving waters in the Luleå area, Northern Sweden; seasonal changes in contamination loads in the receiving waters due to snowmelt; and factors influencing the pollutant pathways in the receiving waters.

Materials and methods

In front of three storm sewer outlets in Luleå, samples of bottom sediment (surface layer 0–2 cm) were collected from the connecting ditches and the downstream water body in autumn and spring (before and after the snow season 2009/2010). The characteristics of the receiving waters differed in geomorphology and vegetation. The sediment was analyzed for loss-on-ignition (LOI), grain size, and bulk concentrations of SiO2, Al2O3, CaO, Fe2O3, MnO, Na2O, P2O5, TiO2, As, Cd, Co, Cr, Cu, Hg, Ni, Pb, S, V, and Zn. The sediment contamination was compared to concentrations at a reference point in Luleå where the bottom sediment was not affected by stormwater discharges and with Swedish environmental quality guidelines. Pearson’s correlation and a principal component analysis were used to further evaluate the results.

Results and discussion

Relative to the reference point, elevated trace metal concentrations were detected in sediments at all three sampling stations. At two of the stations, seasonal variations in ditch sediment grain size, LOI, and contaminant concentrations were observed, originating from stormwater sediment. Snowmelt runoff caused an increased proportion of fine-grained sediment fractions (<0.063 mm) in spring, mainly due to changes in runoff intensity and high sediment loads in the snowmelt runoff. The retention of metals appeared to be due to low turbulence in the water and the presence of organic material.

Conclusions

Stormwater discharge affected the contaminant concentrations in the bottom sediments. The observed seasonal variation of contaminants indicated that relatively high amounts of contaminants are discharged during snowmelt and then reallocated within the receiving water body, either directly or after some temporal retention, depending on the characteristics of the receiving water. A calm water column and the presence of organic material in the receiving water body were crucial for the retention of metals.
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13.
Ambient particle and gas concentrations, wet deposition and dry deposition were measured in Warren, MI between December 18, 1983 and April 6, 1984. Dry deposition was measured to various surfaces in a cutoff bucket, including a snow surface, a snow/water surface during melting and a deionized water surface. Dry deposition velocities were calculated for various species from the ratio of the dry flux to the ambient concentrations. The dry deposition velocities measured to a snow surface were 0.082 cm s?1 SO2 2.0 for HNO3, 0.083 for NH4 +, 2.0 for Ca++ and 4.3 for Cl?. The values were not significantly different for a snow/water surface during melting compared to a snow surface. However, higher values of 0.69 cm s?1 for SO2, 6.2 for HNO3, 0.33 for NH4 +, and 4.2 for Ca++ were found to a deionized water surface in the spring. These higher values could be due to the higher air temperature, the pH of the liquid or to increased atmospheric mixing during this period.  相似文献   

14.
Specific rates of Hg (203HgCl2) methylation and McHg (14CH3HgI) demethylation in aerobic and anaerobic conditions were determined in samples of surface sediments (0 to 2 cm) taken from five small headwater lakes in Southern Finland. The highest rates of methylation were measured in anaerobic conditions. However, the importance of aerobic methylation increased with increasing Fe and Mn content in sediment. There was little difference between aerobic and anaerobic demethylation. The results demonstrate that the net McHg production in lake sediments depends on the individual characteristics of the lake, particularly pH and and sediment properties. These characteristics seem to affect demethylation in anaerobic conditions and methylation in aerobic conditions.  相似文献   

15.
Studies were conducted at the deepest location of the meromictic Piaseczno pit lake, southern Poland, which was created in abandoned sulphur opencast. Pearson correlation and PCA were used to established the relationship between the elements and physico-chemical parameters of the water, whereas discriminant test to study vertical and time differentiation of Cd, Pb, Sr, Cu, Zn, Mn, and Fe concentrations. The results indicated both vertical (except Cu and Zn) and time differentiations of studied elements in the lake water. The highest concentrations of Cd, Pb, and Sr were found in the monimolimnion, that of Mn and Fe in the anoxic water. Depth profiles of Cu and Zn did not show any pronounced trend. Pb and Sr distributions in the water were related to alkalinity, Cl? and COD, Cd to alkalinity and Cl?, Mn and Fe to the redox conditions, Mn to water pH, and Fe to the alkalinity. The upper (0–15 cm) layer of the sediment consisted mainly of S (24.2 Atom%), Fe (21.62%), Ca (18.4%), Si (14.3%), and (Al 6.3%) and reflected mainly processes proceeded in the anoxic water-sediment interface. Calculated accumulation coefficients (K d) of the elements in the sediment are discussed.  相似文献   

16.

Purpose

The aim of this study was to assess the applicability of ionic liquids (ILs) in the extraction of organic contaminants from sediments and in passive sampling as a receiving phase material.

Materials and methods

Solutions of two water-soluble ionic liquids (WSILs)—1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIm]BF4) and N-butyl-3-methyl pyridinium tetrafluoroborate ([BMPy]BF4)—were used for the extraction of endocrine-disrupting chemicals (EDCs), including bisphenol A (BPA), 17β-estradiol (E2), and nonylphenol (NP), from different sediments. Furthermore, a hydrophobic IL (1-hexadecyl-3-methyl imidazolium hexafluorophosphate) was filled in a polyethylene (PE) membrane tubing to build an IL-PE passive sampler for sediment pore water. Uptake kinetics were studied by exposing samplers to sediments artificially contaminated by EDCs and identified by exposing samplers to field-contaminated sediments.

Results and discussion

EDCs were efficiently extracted by WSIL solutions from the two artificially contaminated sediments, with maximum extraction efficiencies of 84.2–104.6 % by the [BMIm]BF4 solution and 74.9–103.7 % by the [BMPy]BF4 solution. However, WSIL solutions are not suitable for EDC extraction from sediment with very low organic carbon contents. EDCs in sediment pore water can be efficiently taken up by the IL-PE sampler, with uptake rate constants of 2.08?×?10?2?l?g?1?day?1 (BPA), 5.74?×?10?2?l?g?1?day?1 (E2), and 2.10 l?g?1?day?1(NP).

Conclusion

BPA, E2, and NP can be extracted efficiently by IL water solution from most of the artificially and field-contaminated sediments used in this study. The IL ([HDMIm]PF6)-PE passive sampler can be used to monitor EDCs in the pore water of sediments. A good match between the calculated and measured concentrations of BPA and E2 in pore water of field-contaminated sediments was observed.  相似文献   

17.
Li  Kun  Wang  Peifang  Qian  Jin  Wang  Chao  Xing  Linghang  Liu  Jingjing  Tian  Xin  Lu  Bianhe  Tang  Wenyi 《Journal of Soils and Sediments》2019,19(4):2034-2047
Purpose

Here, the roles of sediment components in perfluorooctane sulfonate (PFOS) adsorption onto aquatic sediments and relevant adsorption mechanisms were investigated in terms of adsorption isotherms and influences of TiO2 nanoparticles (NPs) contamination.

Materials and methods

Due to the complexity of the sediments, instead of randomly selecting different component sediments, the selective dissolution method was used to better explore the effects of sediment compositions, such as sediment organic matter (SOM) and ferric oxides (dithionite–citrate–bicarbonate [DCB] Fe), and TiO2 NPs pollution on PFOS adsorption. Mathematical equations (Freundlich, Langmuir, and Temkin) were used to describe the adsorption behavior of PFOS on different sediments and adsorption mechanisms of multiple pollutant interactions. Moreover, the characterization methods of zeta potential, nitrogen (N2) adsorption–desorption, and scanning electron microscopy (SEM) analysis, as well as Fourier transform infrared (FT-IR) spectroscopy, explained effects of the sediment components and TiO2 NPs on PFOS adsorption properties in view of physicochemical theories.

Results and discussion

The adsorption isotherms of PFOS on six tested sediments were all nonlinear (Freundlich model, R2 = 0.992~1.000). The Freundlich sorption affinities (KF) of PFOS on S (original sediments), S1 (sediment organic matter (SOM)-removed S), and S2 (ferric oxides (DCB Fe)-removed S1) were 0.232, 0.179, and 0.120, respectively. Both SOM and DCB Fe influenced the physicochemical properties of the sediments, e.g., zeta potential, specific surface area, and permanent negative charge. The addition of TiO2 NPs increased the KF of PFOS for S, S1, and S2 by approximately 9.9%, 14.5%, and 26.7%, respectively, by increasing the zeta potential and specific surface area (SBET, Sext, and Smicro) and by changing the water and oil properties of the three sediments. However, the addition of TiO2 NPs decreased the linearity of the sorption isotherm (1/n). FT-IR spectroscopy showed that hydrophobicity, ion exchange, surface complexation, and hydrogen bonding interactions (non-fingerprint region) could all play a role in PFOS sorption onto tested sediments. However, the hypothesis of hydrogen bonding to promote PFOS adsorption on sediment layer silicates (fingerprint region) should be studied further.

Conclusions

The content of both SOM and DCB Fe affected the physicochemical properties of sediment. Both SOM and DCB Fe showed a positive relationship with sorption of PFOS on sediment. The addition of TiO2 NPs increased PFOS sorption by altering the sediment surface properties. Hydrophobic interactions certainly impelled and ligand and ion exchange and hydrogen bonding (non-fingerprint region) could promote PFOS sorption on the sediments.

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18.
Although Lake Anna, an impoundment in Central Virginia, receives acid mine drainage (AMD) from Contrary Creek, the effects of the AMD pollution on the lake are less severe than expected. Previous work at Lake Anna has shown that bacterial sulfate reduction in the lake sediments plays an important role in the recovery of the lake from the AMD inputs. Sulfate removal rates were measured in sediment microcosms under a variety of experimental conditions to determine the factors controlling the rate of sulfate and acidity removal from the lake water. Sulfate removal rates were not significantly different over the short term (3 weeks) in summer sediment microcosms incubated at 6 vs 26 °C. Winter sediment microcosms showed no significant sulfate removal during the 18 day experiment when incubated at either 6 or 28 °C. Thus there is a strong seasonal temperature effect in Lake Anna sediments but no significant short term effect. Simulated AMD, with and without Fe, was added to sediment microcosms collected from an unpolluted part of the lake. The microcosms with Fe had significantly higher rates of sulfate removal indicating that Fe plays an important role in transporting sulfate to the sediment and/or in preventing oxidation of the reduced sulfide. After 27 days, from 54 to 96% of the added sulfate in the simulated AMD was recovered as FeS or S0 in the top 4 cm of sediment. In a separate experiment, 35S-SO inf4 sup2? was found to attach to precipitating Fe oxyhydroxides (1.5 to 4.7 mol SO inf4 sup2? mol?1 Fe precipitate) upon mixing Contrary Creek (AMD) and Lake Anna waters. Results of this study suggest that sulfate removal may be more rapid in metal rich AMD systems thans in metal poor systems characteristic of those which receive acidic deposition.  相似文献   

19.

Purpose

High groundwater arsenic (As) and salinity have been detected in aquifers of the Hetao Basin in Mongolia which have caused serious public health concerns. The objective of this study was to characterize the distributions of the soluble components in sediment in different lithologies and depths and to assess the relationship between soluble As in sediments and dissolved As in groundwater.

Materials and methods

One hundred and one sediment samples and 13 groundwater samples were collected from four boreholes at varied depths. In addition to total chemicals and mineralogical phases of sediments, the soluble components (including major ions and As, Fe, and Mn) in sediments and dissolved chemicals in groundwater were analyzed.

Results and discussion

Clay or silty clay had relatively higher EC values (189–805 μS cm?1) than aquifer sands (approximately 92–261 μS cm?1). The major soluble components were Na+, Ca2+, HCO3 ?, and SO4 2?, which were more variable in clay samples than fine sand samples. Soluble As concentrations ranged between 2 and 950 μS cm?1, and high contents generally occurred in clay sediments with high contents of soluble Fe and Mn. A comparison of chemicals between soluble components in sediments and dissolved species in groundwaters at matched depths showed that chemicals were preferentially partitioned into sediments at the mountain front and deep aquifers (>60 m), while partitioned into groundwater in the shallow aquifers (<60 m) of the flat plain. Arsenic was preferentially partitioned into groundwater in aquifers with relatively low dissolved SO4 2?.

Conclusions

Groundwater components were mostly sourced from corresponding sediments. In clay sediments, As was desorbed from the surface sites along with other soluble components. Under reducing conditions, reduction of Fe oxides with high surface sites for As adsorption led to a weak association of As with other phases (such as carbonates), and therefore resulted in high dissolved As concentrations and low As partition between sediments and groundwater in deep aquifers.
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20.
Preparations for neutralization of two acidic lakes in the southwest Adirondacks included determination of base neutralization capacity for sediments as well as the water column. For sediments this involved assessing vertical and horizontal gradients in sediment properties related to sediment-bound acidity. The analyses showed significant variance vertically (depth within the sediment profile) and horizontally (due mainly to depth of overlying water) in both lakes. Base requirements, equivalent to the acidity present 3in 2 cm of sediments ranged between 0.011 and 0.022 kg CaCO3 m?3 for the two lakes. Preliminary observations indicate pH3 values and Ca content increased in the surficial sediments of both lakes after treatment.  相似文献   

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