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1.
This study aims to remove of Cu 2+, Cd 2+, and Pb 2+ ions from solution and to investigate the adsorption isotherms, adsorption kinetics, and ion‐exchange affinities of these metals using waste activated sludge (AS) biomass. The adsorptions of the metals on biomass were optimal at an acidic pH value of 6.0 based on its monolayer capacities. Maximum monolayer capacities of AS biomass ( qmax) were calculated as 0.478, 0.358, and 0.280 mmol g ?1 for Cu 2+, Cd 2+, and Pb 2+, respectively, and the adsorption equilibrium time was found as 60 min for each metal. The adsorbed amount of metal rose with increasing of initial metal ion concentration. The equilibrium adsorption capacity of AS for initial 0.25 mmol L ?1 metal concentration was determined as 0.200, 0.167, and 0.155 mmol g ?1 for Cu 2+, Cd 2+, and Pb 2+ ions, respectively. These relevant values were determined as 0.420, 0.305, and 0.282 mmol g ?1 for Cu 2+, Cd 2+, and Pb 2+ ions, respectively, when initial metal concentration was 0.50 mmol L ?1. In the multi‐metal sorption system, the adsorption capacity of AS biomass was observed in the order of Cu 2+ > Cd 2+ > Pb 2+. In the presence of 100 mmol L ?1 H + ion, the order of ion‐exchange affinity with H + was found as Cu 2+ > Cd 2+ > Pb 2+. The adsorption kinetics were also found to be well described by the pseudo‐second‐order and intraparticle diffusion models. Two different rate constants were obtained as ki1 and ki2 and ki1 (first stage) was found to be higher than ki2 (second stage). 相似文献
2.
The effects of various parameters such as initial concentration, adsorbent loading, pH, and contact time on kinetics and equilibrium of adsorption of Cd 2+ metal ion from its aqueous solution by castor seed hull (CSH) and also by activated carbon have been investigated by batch adsorption experiments. The amount of adsorption increases with initial metal ion concentration, contact time, solution pH, and the loading of adsorbent for both the systems. Kinetic experiments indicate that adsorption of cadmium metal ion on both CSH and on activated carbon consists of three steps – a rapid adsorption of cadmium metal ion, a transition phase, and an almost flat plateau region. This has also been confirmed by the intraparticle diffusion model. The lumped kinetic results show that the cadmium adsorption process follows a pseudo‐second order rate law. The kinetic parameters including the rate constant are determined at different initial metal ion concentrations, pH, amount, and type of adsorbent, respectively. The Langmuir and Freundlich adsorption isotherm models are used to describe the experimental data. The Langmuir model yields a better correlation coefficient than the other model. A comparison of the monolayer adsorption capacity ( qm) of CSH, activated carbon, and several other reported adsorbents has been provided. The value of separation factor ( RL) calculated from the Langmuir equation also gives an indication of favorable adsorption of the metal ion. From comparative studies, it has been found that CSH is a potentially attractive adsorbent than commercial activated carbon for cadmium metal ion (Cd 2+) removal. 相似文献
3.
In this paper, a novel composite material the silica grafted by poly( N‐vinyl imidazole) (PVI), i.e., PVI/SiO 2, was prepared using 3‐methacryloxypropyl trimethoxysilane (MPS) as intermedia through the “grafting from” method. The adsorption behavior of metal ions by PVI/SiO 2 was researched by both static and dynamic methods. Experimental results showed that PVI/SiO 2 possessed very strong adsorption ability for metal ions. For different metal ions, PVI/SiO 2 exhibited different adsorption abilities with the following order of adsorption capacity: Cu 2+ > Cd 2+ > Zn 2+. The adsorption material PVI/SiO 2 was especially good at adsorbing Cu(II) ion and the saturated adsorption capacity could reach up to 49.2 mg/g. The empirical Freundlich isotherm was found to describe well the equilibrium adsorption data. Higher temperatures facilitated the adsorption process and thus increased the adsorption capacity. The pH and grafting amount of PVI had great influence on the adsorption amount. In addition, PVI/SiO 2 particles had excellent eluting and regenerating property using diluted hydrochloric acid solution as eluent. The adsorption ability trended to steady during 10 cycles. 相似文献
4.
The anionic structure of magmatic liquids has been estimated at 1 atm and at pressures corresponding to those of the upper mantle. These estimates are based predominantly on spectroscopic data on binary metal oxide-silica and ternary metal oxide-silica-alumina melts. Structural information on melt compositions in aluminate-silica joins has been used to provide detailed information on the role of Al 3+ in natural magma at atmospheric and high pressure.Regardless of pressure, andesitic melts may be described as combinations of chain, sheet, and three-dimensional network units. Nearly all Al 3+ in the magmatic liquid resides in the three-dimensional network units. This Al 3+ is locally charge-balanced with Na +, K +, Ca 2+, and Mg 2+. In the latter two cases, Al 3+ and Si 4+ are ordered, whereas for Na + and K +, Si 4+ and Al 3+ are randomly mixed. Solution of water in natural magma results in the formation of new nonbridging oxygens in addition to OH groups attached to Si 4+ and metal cations.On the basis of determined solution mechanisms of CO 2 and H 2O in silicate melts, thermodynamic properties of HO+ CO2, fluids and hydrous silicate melts and melting phase relations in peridotite-H 2O-CO 2, systems, it is found that natural andesitic magma in equilibrium with spinel Iherzolite in the upper mantle (10–20 kbar) must contain at least 5–7 wt.% H 2O. Andesitic magma with 5–7 wt.% H 2O in solution may be described as a mixture of Al-free three-dimensional units, sheets, and chains with a small proportion (less than 10%) of monomers. 相似文献
5.
The stable isotopic composition of dissolved inorganic carbon (δ 13C‐DIC) was investigated as a potential tracer of streamflow generation processes at the Sleepers River Research Watershed, Vermont, USA. Downstream sampling showed δ 13C‐DIC increased between 3–5‰ from the stream source to the outlet weir approximately 0·5 km downstream, concomitant with increasing pH and decreasing PCO 2. An increase in δ 13C‐DIC of 2·4 ± 0·1‰ per log unit decrease of excess PCO 2 (stream PCO 2 normalized to atmospheric PCO 2) was observed from downstream transect data collected during snowmelt. Isotopic fractionation of DIC due to CO 2 outgassing rather than exchange with atmospheric CO 2 may be the primary cause of increased δ 13C‐DIC values downstream when PCO 2 of surface freshwater exceeds twice the atmospheric CO 2 concentration. Although CO 2 outgassing caused a general increase in stream δ 13C‐DIC values, points of localized groundwater seepage into the stream were identified by decreases in δ 13C‐DIC and increases in DIC concentration of the stream water superimposed upon the general downstream trend. In addition, comparison between snowmelt, early spring and summer seasons showed that DIC is flushed from shallow groundwater flowpaths during snowmelt and is replaced by a greater proportion of DIC derived from soil CO 2 during the early spring growing season. Thus, in spite of effects from CO 2 outgassing, δ 13C of DIC can be a useful indicator of groundwater additions to headwater streams and a tracer of carbon dynamics in catchments. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
6.
A new sorbent was prepared by loading rhodamine B on Amberlite IR‐120. Various physico‐chemical parameters such as effects of adsorbate concentration, contact time, pH, and temperature on the sorption of the dye have been studied. Thermodynamic parameters (Δ H° and Δ S°) were also evaluated for the sorption of dye. Kinetic studies revealed that the sorption of the dye was best fit for pseudo‐second‐order kinetic. The metal ion uptake in different solvent systems has been explored through column studies. On the basis of distribution coefficient ( Kd), some heavy metal ions of analytical interest from binary mixtures have been separated. The limit of detection (LOD) for the Ni 2+ and Fe 3+ metal ions was 0.81 and 0.60 µg L ?1, and the limit of quantification (LOQ) was found to be 2.72 and 2.0 µg L ?1. This sorbent has also been successfully applied in the analysis of multivitamin formulation. The applicability of the modified resin in the separation of heavy metals constituting real and synthetic samples has been explored. 相似文献
7.
Seasonal metrics and environmental responses to forestry soil surface CO2 emission effluxes among three types of lower subtropical forests were consistently monitored over two years with static chamber-gas chromatograph techniques among three types of lower subtropical forests. Results showed that annual CO2 effluxes (S+L) reached 3942.20, 3422.36 and 2163.02 CO2 g·m−2·a−1, respectively in the monsoon evergreen broadleaf forest, mixed broadleaf-coniferous forest and coniferous forest. All the three types of forests revealed the same characteristics of seasonal changes with the CO2 effluxes peaking throughout June to August. During this peaking period, the effluxes were 35.9%, 38.1% and 40.2% of the total annual effluxes, respectively. The CO2 emission process responding to the environmental factors displayed significantly different patterns in forestry soils of the three types of forests. The coniferous forest (CF) was more sensitive to temperature than the other two types. The Q
10 values were higher, along with greater seasonal variations of the CO2 efflux, indicating that the structurally unique forestry ecosystem has disadvantage against interferences. All the three types of forestry CO2 effluxes showed significant correlation with the soil temperature (T
s), soil water content (M
s) and air pressure (P
a). However, stepwise regression analysis indicated no significant correlation between air pressure and the soil CO2 efflux. With an empirical model to measure soil temperature and water content in 5 cm beneath the soil surface, the CO2 effluxes accounting for 75.7%, 77.8% and 86.5% of the efflux variability respectively in soils of BF, MF and PF were calculated. This model can be better used to evaluate the CO2 emission of soils under water stress and arid or semi-arid conditions. 相似文献
8.
In this study, carboxymethylcellulose (CMC) based thermoresponsive nanocomposite hydrogel was synthesized for the removal of Cu 2+ and Pb 2+ ions from aqueous solutions. To prepare nanocomposite hydrogel, graft copolymerization of N‐isopropyl acrylamide (NIPAm) and acrylic acid (AA) onto CMC was carried out in Na‐montmorillonite (MMT)/water suspension media and ammonium persulfate (APS) used as initiator. The chemical structures of hydrogels were characterized by Fourier transform infrared (FT‐IR) and X‐ray diffraction spectroscopy (XRD). Lower critical solution temperature (LCST), pH responsivity, swelling, and deswelling properties of the hydrogels were also examined. In addition competitive and non‐competitive removal of Cu 2+ and Pb 2+ studies were carried out. According to heavy metal sorption studies results, removal capacities of nanocomposite hydrogel for both metal ions were found to be higher than those of pure hydrogel. The analyzed adsorption data showed that the adsorption process of Cu 2+ and Pb 2+ could be explained by pseudo‐second order kinetic model. Moreover, according to competitive sorption studies, it is found to be that both hydrogels are more selective to Cu 2+ ion rather than Pb 2+. 相似文献
9.
Abstract We review the carbon‐isotope data for finely disseminated carbonates from bioaltered, glassy pillow rims of basaltic lava flows from in situ slow‐ and intermediate‐spreading oceanic crust of the central Atlantic Ocean (CAO) and the Costa Rica Rift (CRR). The δ 13C values of the bioaltered glassy samples from the CAO show a large range, between ?17 and +3‰ (Vienna Peedee belemnite standard), whereas those from the CRR define a much narrower range, between ?17‰ and ?7‰. This variation can be interpreted as the product of different microbial metabolisms during microbial alteration of the glass. In the present study, the generally low δ 13C values (less than ?7‰) are attributed to carbonate precipitated from microbially produced CO 2 during oxidation of organic matter. Positive δ 13C values >0‰ likely result from lithotrophic utilization of CO 2 by methanogenic Archaea that produce CH 4 from H 2 and CO 2. High production of H 2 at the slow‐spreading CAO crust may be a consequence of fault‐bounded, high‐level serpentinized peridotites near or on the sea floor, in contrast to the CRR crust, which exhibits a layer‐cake pseudostratigraphy with much less faulting and supposedly less H 2 production. A comparison of the δ 13C data from glassy pillow margins in two ophiolites interpreted to have formed at different spreading rates supports this interpretation. The Jurassic Mirdita ophiolite complex in Albania shows a structural architecture similar to that of the slow‐spreading CAO crust, with a similar range in δ 13C values of biogenic carbonates. The Late Ordvician Solund–Stavfjord ophiolite complex in western Norway exhibits structural and geochemical evidence for evolution at an intermediate‐spreading mid‐ocean ridge and displays δ 13C signatures in biogenic carbonates similar to those of the CRR. Based on the results of this comparative study, it is tentatively concluded that the spreading rate‐dependent tectonic evolution of oceanic lithosphere has a significant control on the evolution of microbial life and hence on the δ 13C biosignatures preserved in disseminated biogenic carbonates in glassy, bioaltered lavas. 相似文献
10.
This study investigated CO 2 degassing and related carbon isotope fractionation effects in the Wiesent River that drains a catchment in the karst terrain of the Franconian Alb, Southern Germany. The river was investigated by physico‐chemical and stable isotope analyses of water and dissolved inorganic carbon during all seasons along 65‐km long downstream transects between source and mouth. Calculated pCO 2 values at the source were 21 400 ± 2400 µatm. The pCO 2 rapidly decreased in the river water and dropped to an average of 1240 ± 330 µatm near the mouth. About 90% of this decrease occurred within the first 6 km of the river. The river was supersaturated with respect to CO 2 over its entire course and must have acted as a continuous year‐round CO 2 source to the atmosphere. The average CO 2 flux from the karst river was estimated with 450 mmol m ?2 day ?1 with higher fluxes up to 5680 mmol m ?2 day ?1 at the source. At the source, δ13C DIC values showed no seasonal variations with an average of ?14.2 ± 0.2‰. This indicated that groundwater retained high pCO 2 mainly from soil CO 2. The contribution of soil CO 2 to dissolved inorganic carbon was estimated at 65% to 72%. The downstream CO 2 loss caused a positive shift in δ13C DIC values of 2‰ between source and mouth because of the preferential loss of the 12C isotope during degassing. Considering the findings of this study and the fact that carbonate lithology covers a significant part of the earth's surface, CO 2 evasion from karst regions might contribute notably to the annual carbon dioxide release from global freshwater systems. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
11.
A multi‐element ion‐pair extraction method was described for the preconcentration of Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Ni(II), Pb(II), and Zn(II) ions in environmental samples prior to their determinations by flame atomic absorption spectrometry (FAAS). As an ion‐pair ligand 2‐(4‐methoxybenzoyl)‐ N′‐benzylidene‐3‐(4‐methoxyphenyl)‐3‐oxo‐ N‐phenyl‐propono hydrazide (MBMP) was used. Some analytical parameters such as pH of sample solution, amount of MBMP, shaking time, sample volume, and type of counter ion were investigated to establish optimum experimental conditions. No interferences due to major components and some metal ions of the samples were observed. The detection limits of the proposed method were found in the range of 0.33–0.9 µg L ?1 for the analyte ions. Recoveries were found to be higher than 95% and the relative standard deviation (RSD) was less than 4%. The accuracy of the procedure was estimated by analyzing the two certified reference materials, LGC6019 river water and RTC‐CRM044 soil. The developed method was applied to several matrices such as water, hair, and food samples. 相似文献
12.
Predicting and quantifying impacts of potential carbon dioxide (CO 2) leakage into shallow aquifers that overlie geologic CO 2 storage formations is an important part of developing reliable carbon storage techniques. Leakage of CO 2 through fractures, faults or faulty wellbores can reduce groundwater pH, inducing geochemical reactions that release solutes into the groundwater and pose a risk of degrading groundwater quality. In order to help quantify this risk, predictions of metal concentrations are needed during geologic storage of CO 2. Here, we present regional-scale reactive transport simulations, at relatively fine-scale, of CO 2 leakage into shallow aquifers run on the PFLOTRAN platform using high-performance computing. Multiple realizations of heterogeneous permeability distributions were generated using standard geostatistical methods. Increased statistical anisotropy of the permeability field resulted in more lateral and vertical spreading of the plume of impacted water, leading to increased Pb 2+ (lead) concentrations and lower pH at a well down gradient of the CO 2 leak. Pb 2+ concentrations were higher in simulations where calcite was the source of Pb 2+ compared to galena. The low solubility of galena effectively buffered the Pb 2+ concentrations as galena reached saturation under reducing conditions along the flow path. In all cases, Pb 2+ concentrations remained below the maximum contaminant level set by the EPA. Results from this study, compared to natural variability observed in aquifers, suggest that bicarbonate (HCO 3−) concentrations may be a better geochemical indicator of a CO 2 leak under the conditions simulated here. 相似文献
13.
Stable isotopic ( δD VSMOW and δ18O VSMOW) and geochemical signatures were employed to constrain the geochemical evolution and sources of groundwater recharge in the arid Shule River Basin, Northwestern China, where extensive groundwater extraction occurs for agricultural and domestic supply. Springs in the mountain front of the Qilian Mountains, the Yumen‐Tashi groundwater (YTG), and the Guazhou groundwater (GZG) were Ca‐HCO 3, Ca‐Mg‐HCO 3‐SO 4 and Na‐Mg‐SO 4‐Cl type waters, respectively. Total dissolved solids (TDS) and major ion (Mg 2+, Na +, Ca 2+, K +, SO 42?, Cl ? and NO 3?) concentrations of groundwater gradually increase from the mountain front to the lower reaches of the Guazhou Basin. Geochemical evolution in groundwater was possibly due to a combination of mineral dissolution, mixing processes and evapotranspiration along groundwater flow paths. The isotopic and geochemical variations in melt water, springs, river water, YTG and GZG, together with the end‐member mixing analysis (EMMA) indicate that the springs in the mountain front mainly originate from precipitation, the infiltration of melt water and river in the upper reaches; the lateral groundwater from the mountain front and river water in the middle reaches are probably effective recharge sources for the YTG, while contribution of precipitation to YTG is extremely limited; the GZG is mainly recharged by lateral groundwater flow from the Yumen‐Tashi Basin and irrigation return flow. The general characteristics of groundwater in the Shule River Basin have been initially identified, and the results should facilitate integrated management of groundwater and surface water resources in the study area. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
14.
Soil CO 2 efflux in forest and grassland over 5 years from 2005 to 2009 in a semiarid mountain area of the Loess plateau, China, was measured. The aim was to compare the soil respiration and its annual and inter‐annual responses to the changes in soil temperature and soil water content between the two vegetation types for observing soil quality evolution. The differences among the five study years were the annual precipitation (320.1, 370.5, 508.8, 341.6, and 567.4 mm in 2005–2009, respectively) and annual distribution. The results showed that the seasonal change of soil respiration in both vegetation types was similar and controlled by soil temperature and soil water content. The mean soil respiration across 5 years in the forest (3.78 ± 2.68 µmol CO 2 m ?2 s ?1) was less than that in the grassland (4.04 ± 3.06 µmol CO 2 m ?2 s ?1), and the difference was significant. The drought soil in summer depressed soil respiration substantially. The Q10 value across 5‐year measurements was 2.89 and 2.94 for forest and grassland. When soil water content was between wilting point (WP) and field capacity (FC), the Q10 in both types increased with increasing soil water content, and when soil water content dropped to below WP, soil respiration and the Q10 decreased substantially. Although an exponential model was well fitted to predict the annual mean soil respiration for each single year data, it overestimated and underestimated soil respiration, respectively, in drought conditions and after rain for short periods of time during the year. The two‐variable models including temperature and water content variables could be well used to predict soil respiration for both types in all weather conditions. The models proposed are useful for understanding and predicting potential changes in the eastern part of Loess plateau in response to climate change. 相似文献
15.
The fixation of slightly soluble substances on inert carriers offers the possibility to examine the exchange of heavy metals at these phases under dynamic conditions. Investigations are presented for the exchange of Zinc under various conditions (pH, different concentrations of other cations such as Na + and Ca 2+ or of NTA as a chelating agent) on fixed MnO 2-hydrate, Fe(OH 3), CaCO 3 and a natural clay-slate. Batch-experiments showed that all phases are able to sorb Zinc with MnO 2-hydrate as the best sorbent for this metal (highest sorption constant and capacity). Column desorption experiments demonstrate that a decrease of the pH of the aqueous phase or an addition of NTA remobilise Zinc from MnO 2-hydrate, Fe(OH) 3, CaCO 3 and also from the clay-slate. The same effect of releasing sorbed metal (with exception of the CaCO 3-phase) show Na + or Ca 2+ containing solutions. Therefore Zinc is bonded under natural conditions on the oxihydrates and the clay-slate in a labile, ion-exchangeable form in contrast to CaCO 3, on which Zinc is sorbed probably as the carbonate. 相似文献
16.
This study involved a baseline evaluation of fluvial carbon export and degas rates in three nested rural catchments (1 to 80 km 2) in Taboão, a representative experimental catchment of the Upper Uruguay River Basin. Analyses of the carbon content in stream waters and the catchment carbon yield were based on 4‐year monthly in situ data and statistical modeling using the United States Geological Survey load estimator model. We also estimated p CO 2 and degas fluxes using carbonate equilibrium and gas‐exchange formulas. Our results indicated that the water was consistently p CO 2 saturated (~90% of the cases) and that the steep terrain favors high gas evasion rates. The mean calculated fluvial export was 5.4 tC·km ?2·year ?1 with inorganic carbon dominating (dissolved inorganic carbon:dissolved organic carbon ratio >4), and degas rates (~40 tC km ?2·year ?1) were nearly sevenfold higher than the downstream export. The homogeneous land use in this nested catchment system results in similar water‐quality characteristics, and therefore, export rates are expected to be closely related to the rainfall–runoff relationships at each scale. Although the sampling campaigns did not fully reproduce storm‐event conditions and related effects such as flushing or dilution of in‐stream carbon, our results indicated a potential link between dissolved inorganic carbon and slower hydrological pathways related to subsurface water storage and movement. 相似文献
17.
Removal of copper, nickel, and zinc ions from synthetic electroplating rinse water was investigated using cationic exchange resin (Ceralite IR 120). Batch ion exchange studies were carried out to optimize the various experimental parameters (such as contact time, pH, and dosage). Influence of co‐existing cations, chelating agent EDTA on the removal of metal ion of interest was also studied. Sorption isotherm data obtained at different experimental conditions were fitted with Langmuir, Freundlich, Redlich–Peterson, and Toth models. A maximum adsorption capacity of 164 mg g ?1 for Cu(II), 109 mg g ?1 for Ni(II), and 105 mg g ?1 for Zn(II) was observed at optimum experimental conditions according to Langmuir model. The kinetic data for metal ions adsorption process follows pseudo second‐order. Presence of EDTA and co‐ions markedly alters the metal ion removal. Continuous column ion exchange experiments were also conducted. The breakeven point of the column was obtained after recovering effectively several liters of rinse water. The treated rinse water could be recycled in rinsing operations. The Thomas and Adams–Bohart models were applied to column studies and the constants were evaluated. Desorption of the adsorbed metal ions from the resin column was studied by conducting a model experiments with Cu(II) ions loaded ion exchange resin column using sulfuric acid as eluant. A novel lead oxide coated Ti substrate dimensionally stable (DSA) anode was prepared for recovery of copper ions as metal foil from regenerated liquor by electro winning at different current densities (50–300 A cm ?2). 相似文献
18.
Spatial and temporal variations of free CO 2 concentrations in surface waters are mainly controlled by dynamic processes encompassing terrestrial inputs and in‐stream biotic cycling. Free CO 2 can be expressed as ‘excess partial pressure of CO 2’ ( epCO 2), indicating supersaturation or under‐saturation with respect to atmospheric CO 2. Seasonal patterns of epCO 2 at sites draining nested upland catchments between 3·40 and 1837 km 2 were assessed within the River Dee basin in NE Scotland. EpCO 2 values ranged from 0·14 at the lowermost site on the mainstem in autumn to 12·7 on a major tributary during spring. A seasonality index was derived to describe contrasting winter/spring maxima and summer/autumn minima as annual mean epCO 2 values could not clearly distinguish between different sites. Seasonal differences tended to increase downstream as progressive changes in physicochemical conditions enhanced the influence of autotrophic communities. However, perturbations to this continuum occurred as CO 2 inputs from high DOC, heterotrophic tributaries and land‐use changes between open moorland and forest affected downstream continuity. Major tributaries showed reduced differences between seasons compared to the mainstem. Smaller headwaters indicated a lack of seasonality as high connectivity of responsive, peaty soils enabled continual inputs of terrestrially derived free CO 2 to streams concomitant with limited autotrophic CO 2 removal, maintaining epCO 2 > 1 throughout. Seasonality of epCO 2 was mainly driven by the ability of in‐stream biota to consume CO 2 during optimal conditions in summer/autumn. This was confirmed by multiple linear regression analysis, which indicated that, apart from catchment area, baseflow and biotic activity indicators were the best predictors of epCO 2 seasonality characteristics at any particular stage of the river system. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
19.
In static bioassays the toxicity of heavy metal ions against Lymnaea acuminata over 24 … 96 h is tested. The values of the LC 50,96h for the metals tested are, in mg/l: Hg 2+ ?0.023; Cu 2+-0.034, Cd 2+ ?0.872, Ni 2+ ?2.78, Cr 6+ ?5.97 and Zn 2+ ?10.49. In the combined solutions of Cu 2+, Ni 2+ and Zn 2+ at least an additive effect of toxicity occurs in the presence of two metals. The same holds for the presence of the three metals; in this case, the relative toxicity against the mixture of two metallic salt solutions appears to be slightly reduced. The acute manifestation of the toxic effect occurs within 48 h, subsequently the relative mortality decreases especially in the mixed solutions. 相似文献
20.
Three techniques for obtaining soil water solutions (gravitational and matrical waters extracted using both in situ tension lysimeters and in vitro pressure chambers) and their later chemical analysis were performed in order to know the evolution of the soil‐solution composition when water moves down through the soil, from the Ah soil horizon to the BwC‐ or C‐horizons of forest soils located in western Spain. Additionally, ion concentrations and water volumes of input waters to soil (canopy washout) and exported waters (drainage solutions from C‐horizons) were determined to establish the net balance of solutes in order to determine the rates of leaching or retention of ions. A generalized process of sorption or retention of most components (even Cl ?) was observed, from the soil surface to the C‐horizon, in both gravitational and matrical waters, with H 4SiO 4, Mn 2+, Na +, and SO 42? being the net exported components from the soil through the groundwater. These results enhance the role of the recycling effect in these forest soils. The net percentages of elements retained in these forest soils, considering the inputs and the outputs balance, were 68% K +, 85% Ca 2+, 58% Mg 2+, 7% Al 3+, 5% Fe 3+, 34% Zn 2+, 57% Cl ?, and 20% NO 3?, and about 75% of dissolved organic carbon was mineralized. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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