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1.
This study sought to assess the influence of compost and earthworms (Dendrobaena veneta) upon the level of hydrocarbon catabolism in petroleum contaminated forecourt soil (extractable petroleum hydrocarbons (EPH) 10 + 1.8 g kg−1 and total 16 United States Environment Protection Agency (USEPA) polycyclic aromatic hydrocarbons (PAH) 1.62 ± 0.5 g kg−1). The catabolic activity of the indigenous microorganisms within uncombined materials (soil and compost) and within the combined treatments (soil plus compost; either with or without earthworms) was assessed by 14C-radiorespirometry (14C-hexadecane, 14C-toluene and 14C-phenanthrene). Maximum levels of catabolic activity were observed (at the end of the incubation period; 84 d) for all three compounds in the combined contaminated soil, compost and earthworm mixtures. Significant (p < 0.05) enhancement factors (relative to the soil only control) in catabolic activity in the combined treatments (soil:compost (1:0.5)) of 3.6 times, 1.5 times and 3.5 times were observed for 14C-hexadecane, 14C-phenanthrene and 14C-toluene, respectively; with maximum levels of catabolic activity for these substrates being 68.6 ± 1.7%, 37.9 ± 5.3% and 85.9 ± 1.3%.  相似文献   

2.
W.D. Nettleton  M.D. Mays 《CATENA》2007,69(3):220-229
There is much interest in predicting future carbon-soil degradation and that occurring today. We have National Soil Survey Laboratory data to assess some of the soil carbon degradation in the Great Basin and western Utah. For this we included data on 32 Nevada and Utah soils on Pleistocene geomorphic surfaces at elevations of 973 to 3172 m. Their mean annual precipitation (MAP) ranges from 20 to 55 cm and mean annual soil temperatures (MAST) from 5 to 12 °C. The MAP and MAST closely correlate with elevation (E) (r = 0.96 and − 0.97 respectively). Mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana (Rydb.) Beetle) dominates vegetation at the higher, colder elevations. Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle and Young) and juniper (Juniperus L.) dominate at intermediate elevations. Little sagebrush (Artemisia arbuscula Nutt.) and related desert species dominate at the lower, warmer elevations. We used acid dichromate digestion and FeSO4 titration to analyze for soil organic carbon (SOC) and bulk density and coarse fragments in the soils to put the data on a volume basis. The soils are well drained and uncultivated. Accumulation of organic carbon in each pedon (OCp) is correlated to MAP and MAST (r = 0.81, and − 0.78 respectively). We predicted OCp from the relationship,
(1)
r2 = 0.64, S.E. = 1.30, n = 32. The soil OC degradation that may have occurred through the Holocene ranges from 35% at sites of the present Aridisols and Vertisols to 22% for the sites of the Mollisols and Alfisols. Eq. (1) shows that today, MAST rises of 1 to 3 °C would produce further OCp degradation from today's levels of 1% to 13% in Aridisols and Vertisols and 12% to 25% in the Mollisols and Alfisols respectively. It also shows that if the MAST drop of 6 °C predicted for the Pleistocene occurred, many of the Aridisols and Vertisols likely would have been Mollisols or Alfisols during the Pleistocene. A temperature rise of 1 °C in a century would likely move the Mollisol–Aridisol boundary from its present 2300 m elevation to an elevation of about 2900 m. A temperature rise of 3 °C in a century would likely move the Mollisol–Aridisol boundary from its present 2300 m elevation to elevations of the highest elevations in Nevada and to the middle of Idaho. Increasing the temperature by 3 °C will likely also increase the area affected by severe desertification in the southern Great Basin north by about 20%.  相似文献   

3.
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4.
No‐tillage management can increase soil surface layer organic C (OC) levels compared with conventional tillage. The mechanisms underlying this increase in highly weathered tropical soils, such as Ferralsols, are not well established. The objective of this study was therefore to evaluate the influence of mineralogy on aggregation and the apportionment of OC across aggregate size fractions in a Brazilian Ferralsol under native vegetation (NV) and no‐tillage management for 10 (NT10) or 20 (NT20) yrs. Under native vegetation, soil OC generally increased with increasing aggregate size while, in response to changing management, soil OC increased in the order NT10 (8.8 g/kg) < NT20 (12.7 g/kg) < NV (19.1 g/kg). There were no significant differences in the mineralogy of the clay size fractions among the three treatments, with the notable exception of the CBD‐extractable Fe oxide fraction (FeCBD). The FeCBD fraction comprises various pedogenic Fe(hydr)oxides and increased from NT10 (33.9 g/kg) to NT20 (64.2 g/kg). The OC/FeCBD mass ratio within aggregates increased in the order NT10 <  NT20 <  NV while R2 values for OC and FeCBD occurrence follow this same trend, with the NT10 soil showing a weaker correlation (R2 = 0.178) compared with the NV soil (R2 = 0.533). We propose that formation of organo‐Fe(III) oxide associations is promoted with implementation of NT management and the consequent reduction in macroaggregate turnover. The development of the OC‐Fe(III) oxide associations and their evolution over time within aggregates to more thermodynamically stable entities will strongly influence the long‐term preservation of soil OC.  相似文献   

5.

Purpose

Sediment cores provide a reliable record of mercury (Hg) contamination and can be used to study long-term Hg pollution and relevant environmental change. In the last hundred years, there were several events which may have contributed to the accumulation of Hg in Jade Bay and its catchment. This work was undertaken to assess the record in total Hg (THg) content in sediments of cores from Jade Bay and its catchment.

Materials and methods

A 5-m sediment core from Jade Bay, Lower Saxonian Wadden Sea, southern North Sea and a 12-m core from its catchment area (Wangerland, coastal zone of the Jade Bay) were used to study Hg contents in sediments. Total Hg, grain size distribution, aluminium (Al) and total organic carbon (TOC) were analysed on subsamples of both sediment cores. Total Hg was determined by oxygen combustion-gold amalgamation using DMA-80.

Results and discussion

As THg contents of the Jade Bay core were positively correlated to the sum of TOC and Al contents (r 2?=?0.86, p?<?0.001), the Hg data were interpreted using a regional normalisation function with the sum of Al and TOC as the normalisation parameters. Total Hg contents of the Wangerland core were correlated better to Al contents (r 2?=?0.70, p?<?0.001) than to the sum of TOC and Al contents (r 2?=?0.63, p?<?0.05). Therefore, Hg contents in sediments of the Wangerland core were normalised to Al contents. Comparison between enrichment factors and the background range of the sediment cores suggested that Jade Bay was contaminated about 50 years ago, and that Wangerland, or the catchment area of Jade Bay, was contaminated about 300 years ago, if no diagenetic remobilization occurred.

Conclusions

Total Hg contents of both cores were low and of no concern to the aquatic environment of Jade Bay. The Hg record was in good agreement with the history of industrial development in the region; thus, Hg deposition could have occurred through atmospheric input, ammunition residues of the Second World War and volcanic emanations, as well as through diagenetic remobilization.  相似文献   

6.
Undisturbed sediment cores from an oligotrophic lake were percolated with artificial porewater to examine the effects of isoetid macrophytes,Littorella uniflora, and benthic microalgae on daily dynamics of sediment retention of phosphorus (P) by either iron (Fe) or manganese (Mn). Retention of Fe and Mn was observed due to oxidation processes mediated by oxygen release fromL. uniflora roots and benthic microalgae. Therefore increased retention of P was observed because of P precipitation with oxidized Fe- and Mn-compounds. During light periods, the ratio between Fe and P precipitation in the sediment was positively correlated with the P uptake byL. uniflora (p < 0.001, r2 = 0.984). The atomic precipitation ratio between Fe and P was between I and 2. The ratio between oxidized Fe-compounds and Fe-bound phosphate in the sediment was positively correlated with the root density ofL. uniflora (p < 0 001. r2 = 0.995). The ratio between Mn and P precipitation was higher (26) than the ratio between Fe and P. The role of benthic primary producers on P retention in freshwater littoral sediments is discussed.  相似文献   

7.
Upon inundation, the soils in a hydroelectric reservoir are subjected to several years of physical, biological, and chemical changes as the transition from a terrestrial to an aquatic ecosystem is achieved. It is suspected that changes in soil Eh and pH alter the metal binding capacity of organic matter, reactive iron (Fe) oxides/oxyhydroxides, and clay minerals, and may cause the mercury associated with these phases to be remobilized. Four cores were collected along a transect from an unflooded forest soil to a pre-impoundment lake bottom sediment. They were subjected to a customized sequential extraction procedure to determine the distribution of Hg between three operationally-defined solid compartments: organic carbon, reactive Fe oxides/hydroxides, and the solid (clay and sulfide) residue. Results indicate that up to 80% of the Hg in the O-horizon of forest soils and flooded soils and up to 85% of the Hg in lake sediments is bound to the NaOH-extractable organic carbon fraction. Furthermore, it was observed that the highest Hg concentrations are associated with degraded organic matter. In the B-horizon of a podzol, 40–60% of the total Hg was found associated with reactive Fe minerals. In contrast, the flooded podzol contains almost no reactive Fe at any depth and associated Hg concentrations are low. We propose that upon inundation, Fe oxides are reduced and Hg released to the pore waters where it is rapidly bound to other available substrates. Analyses of the extractions residues suggest that there is an enrichment of Hg in this fraction immediately above the B-horizon in a flooded soil.  相似文献   

8.
Soil macroinvertebrates were studied in a Mediterranean-type forest on brown-pebble forest soils in southern Russia. At the site, 144 intact soil cores (76 cm2 each) forming a grid of 24 × 6 units were taken in order to determine animal spatial distribution. Abundance of isopods was 166.3 ± 16.0 indiv. m–2 and they constituted about 12% of the total macrofaunal abundance. Biomass of isopods was 3.5 g m–2, or about 21% of the total biomass of macrofauna. Three woodlice genera (Armadillidium, Cylisticus, and Trachelipus) were found at the site. The two latter genera formed almost all (93%) of the isopod population. We found that spatial distribution of woodlice was heterogeneous: areas with 4–5 individuals per sample were neighboring those without animals. In order to study soil factors influencing isopod distribution in the brown-pebble forest soil, the size of a sample was artificially increased by combining adjacent sample units. Litter mass (r = 0.41) and loss on ignition (LOI) (r = –0.55) significantly influenced isopod distribution. Soil pH was near neutral (6.79), LOI was 8.39, and the water holding capacity was 70.9%. Pebbles comprised up to 84% of the sample's mass. Ca. 40 samples are recommended for estimation of isopod abundance in brown forest soil.  相似文献   

9.
Feeding biology and thermal adaptations of the terrestrial isopod Mesoniscus graniger were studied. M. graniger is a depigmented isopod mainly inhabiting cave systems, although it has also been reported in endogeic (soil) habitats. Physiological adaptations are expected to reflect the unique environmental characteristics of caves, including restricted food sources, and stable microclimate with temperatures not exceeding about 10 °C and high relative humidity. The M. graniger from Domica and Ardovská caves (Slovakian Karst) were investigated. We identified organic deposits with associated microorganisms as sources exploited by M. graniger and assessed how these might supply essential polyunsaturated fatty acids (PUFA) in its nutrition. Algae, fungi and bat guano were found as the most important potential resources of PUFA for isopods. Digestive enzymes amylase, trehalase, saccharase and maltase were confirmed in the whole body homogenates of isopods; neither cellulolytic activity nor activities against xylan, laminaran and lichenan were observed. Amylase, maltase and cellobiase activities were also observed in bacterial strains isolated and cultured from isopod midgut, and may account for the measured whole-animal activities. In an artificial temperature gradient, M. graniger selected temperature 3.5 ± 5.4 °C with lower and upper extremes of –1.5 and 18.5 °C. Respiration, as measured by VO2, was almost independent of temperature between 5 and 10 °C, then increased between 10 and 30 °C. These ecophysiological measures are consistent with adaptation to a stenothermal environment.  相似文献   

10.
A major landslide that occurred in 1569 in the Huangtuwa gully catchment within the Rolling Loess Plateau region of China, resulted in the creation of a landslide-dammed lake at the outlet of the small 0.1 km2 tributary valley of the Houxiaotan Gully. All the sediment transported to the outlet of this catchment was deposited in the lake. After about 30 years the dam failed and the lake deposits were dissected as the stream cut down to its former base level. Substantial remnants of the sediment deposits that accumulated over the ca. 30 year period are, however, preserved as terraces near the outlet of the catchment and a vertical section through these sediment deposits was investigated using stratigraphic and pollen tracing techniques. Individual flood couplets could be clearly distinguished and these permitted the establishment of a chronology for the sediment deposits and the estimation of the sediment yields associated with individual events and individual years. Pollen analysis undertaken on samples collected from the individual flood couplets also provided information on the variation of the pollen content of the sediment and the proportion of Artemisia pollen during the period represented by the deposits. Interpretation of the information assembled from the sediment section has made it possible to reconstruct the erosional history of the Houxiaotan catchment during the 31 year period following the landslide. The average sediment yield of the catchment in the late 16th century was very similar to its present-day sediment yield. The sediment yield from the catchment and the relative contribution of the inter-gully areas, as compared to the gully system, declined immediately after the landslide as a result of abandonment of the cultivated land within the catchment. The restoration of cultivation in the catchment after about 17 years resulted in an increase in sediment yield from ca. 9000 t km− 2 yr− 1 to ca. 30,000 t km− 2 yr− 1 and a substantial increase in the proportion of sediment contributed by the cultivated inter-gully areas. Scope exists to apply a similar approach to the sediment deposits that accumulated in other former landslide-dammed lakes within the Rolling Loess Plateau region of China, in order to develop an improved understanding of the erosion history of the region.  相似文献   

11.
In this paper, we demonstrate that reduction of Hg(II) to Hg0 under anaerobic conditions, followed by volatilization of Hg0 to the atmosphere, might be responsible for the removal of Hg from tropical hydromorphic soils. We conducted a series of kinetic batch experiments in which we added Hg(II) to anoxic suspensions of a soil clay fraction and haematite nanoparticles. The clay fraction came from three depths in a hydromorphic soil by the Leblond River in French Guiana, South America: close to the upper and lower boundaries (30–40 cm and 90–100 cm) and within the central part (60–70 cm) of the frequently water‐saturated clay horizon. We prepared a second set of soil clay fraction suspensions with Fe(III) citrate, whose reduction acted as a source of dissolved Fe(II) to investigate the influence of Fe(II) on the production of Hg0. Reduction of Hg(II) to Hg0 occurred with all samples amended with Fe(III) citrate. Laboratory experiments with haematite suspensions demonstrated that adsorption of Fe(II) to the haematite surface created very reactive sites for the reduction of Hg(II), while in the absence of haematite particles, no production of Hg0 occurred. The greatest production of Hg0 was found for the depth intervals 30–40 cm and 90–100 cm, where the total mercury concentration exhibits a local minimum. The observed pseudo‐first order rate constants for the 90–100 cm depth sample were close to rate constants reported for abiotic reduction of Hg(II) by Fe(II) adsorbed on mineral surfaces. Significant production of Hg0 was found for the 90–100 cm depth interval sample, both with and without Fe(III) citrate. A biotic pathway as well as abiotic reduction by Fe(II) might be involved in the reduction of Hg(II) to Hg0.  相似文献   

12.
The aim was to describe Cd sorption in spatially variable sandy soils of the ‘Fuhrberger Feld’ catchment area as a prerequisite for prognosis of Cd transport in soil and of the threat of groundwater pollution. Thus, the possibility is evaluated to derive a generalized Freundlich equation based on multiple regressions relating the retention parameters k and M (from isotherm data of part 1 of this study) to basic soil properties (pedotransfer functions). For the parameter M (exponent), the correlation ‘measured vs estimated’ was weak (r2 < 0.5) whereas k was well predictable by pedotransfer functions. The best regression was obtained if organic carbon (OC). clay content and H+ activity were combined as independent variables (r2 up to 0.96). The obtained k values were much higher than those from comparable literature models, probably due to lower ionic strength and different composition of our background solutions used for the isotherms. As a critical evaluation, the estimates for k were used to derive solute Cd concentrations (Cest) which then were compared to measured data (range 0.1–3 μg L?1). The best but still unsatisfactory r2 was 0.77, obtained if Gest was compared to Cd in 0.01 Mc Ca(NO3)2 equilibria (Cd0). Cd in fresh soil solution (Cdz) showed no significant correlation with Cest, except for one relationship where OC had been excluded from the preceding multiple regression of k. Generally, the role of the variable OC remained unclear. Direct multiple regressions of measured solute Cd vs soil properties (bypassing k, no sorbed fraction) yielded much closer correlations, with r2 = 0.9 for Cd0 vs OC, H+ activity, clay (log data, OC decreases C) and r2 = 0.7 for Cd2 vs OC, H+ activity, clay (log data, OC enhances C).  相似文献   

13.
We tested the hypothesis whether organic matter in subsoils is a large contributor to organic carbon (OC) in terrestrial ecosystems and if survival of organic matter in subsoils is the result of an association with the soil mineral matrix. We approached this by analyzing two forest soil profiles, a Haplic Podzol and a Dystric Cambisol, for the depth distribution of OC, its distribution among density and particle‐size fractions, and the extractability of OC after destruction of the mineral phase by treatment with hydrofluoric acid (HF). The results were related to indicators of the soil mineralogy and the specific surface area. Finally, scanning electron microscopy combined with energy dispersive X‐ray spectroscopy (SEM‐EDX) was used to visualize the location of OC at mineral surfaces and associations with elements of mineral phases. The subsoils (B and C horizons) contained 40—50% of the soil OC including the organic forest floor layers. With increasing depth of soil profiles (1) the radiocarbon ages increased, and (2) increasing portions of OC were either HF‐soluble, or located in the density fraction d >1.6 g cm—3, or in the clay fraction. The proportions of OC in the density fraction d >1.6 g cm—3 were closely correlated to the contents of oxalate and dithionite‐citrate‐bicarbonate‐extractable Fe (r2 = 0.93 and 0.88, P <0.001). SEM‐EDX analyses suggested associations of OC with aluminum whereas silicon‐enriched regions were poor in OC. The specific surface area and the microporosity of the soil mineral matrix after destruction of organic matter were less closely correlated to OC than the extractable iron fractions. This is possibly due to variable surface loadings, depending on different OC inputs with depth. Our results imply that subsoils are important for the storage of OC in terrestrial ecosystems because of intimate association of organic matter with secondary hydrous aluminum and iron phases leading to stabilization against biological degradation.  相似文献   

14.
Mercury concentrations were measured in samples of peat soils, sediments and clams (Rangia cuneata) from a peatland region of the Albemarle-Panlico Peninsula of North Carolina. Total Hg concentrations in peat cores ranged from 40 to 193 ng g?1 (dw); no depth-related trends were noted. Mercury concentrations in surface sediments from canals draining the peatlands and from the Pungo River that receives this drainage ranged from 8 to 20 ng g?1 (dw). Selective extractions of these peat and sediment samples revealed that the bulk of the Hg was associated with organic matter-associated fractions (particularly humic/fulvic acid bound and organic-sulfide bound fractions). No Hg was detected in the relatively mobile and bioavailable water-soluble or ion-exchangeable fractions. Total Hg concentrations in the soft tissues of clams from the Pungo River ranged from 25 to 32 ng g?1 (ww). No concentrations of methyl Hg above the detection limit of a 25 ng g?1 were measured in soils, sediments, or clams. These data indicate that Hg concentrations in this region are at the low end of the distribution of levels reported for uncontaminated systems and that mining of these peatlands is unlikely to significantly elevate Hg concentrations in the receiving estuarine system.  相似文献   

15.
Winter conditions with seasonally frozen soils may have profound effects on soil structure and erodibility, and consequently for runoff and erosion. Such effects on aggregate stability are poorly documented for Nordic winter conditions. The purpose of this study was to quantify the effect of variable freeze–thaw cycles and soil moisture conditions on aggregate stability of three soils (silt, structured clay loam—clay A and levelled silty clay loam—clay B), which are representative of two erosion prone areas in southeastern Norway. A second purpose was to compare aggregate stabilities measured by the Norwegian standard procedure (rainfall simulator) and the more widely used wet-sieving procedure. Surface soil was sampled in autumn. Field moist soil was sieved into the fraction 1–4 mm and packed into cylinders. The water content of the soil was adjusted, corresponding to matric potentials of − 0.75, − 2 and − 10 kPa. The soil cores were insulated and covered, and subjected to 0, 1, 3 or 6 freeze–thaw cycles: freezing at − 15 °C for 24 h and thawing at 9 °C for 48 h. Aggregate stability was measured in a rainfall simulator (all soils) and a wet-sieving apparatus (silt and clay B). The rainfall stability of silt was found to be significantly lower than of clay A and clay B. Clay A and clay B had similar rainfall stabilities, even though it was expected that the artificially levelled clay B would have lower stability. Freezing and thawing decreased the rainfall stability of all soils, but the effect was more severe on the silt soil. There was no evident effect of water content on the stability, probably due to experimental limitations. The same effects were observed for wet-sieved soil, but the wet-sieving resulted in less aggregate breakdown than the rainfall simulator. Rainfall impact seemed to be more detrimental than wet-sieving on more unstable soil, that is, on silt soil and soil subjected to many freeze–thaw cycles. Such conditions are expected to occur frequently during field conditions in unstable winters.  相似文献   

16.
Purpose

Select South Dakota, USA water bodies, including both natural lakes and man-made impoundments, were sampled and analyzed to assess mercury (Hg) dynamics and historical patterns of total Hg deposition.

Materials and methods

Sediment cores were collected from seven South Dakota lakes. Mercury concentrations and flux profiles were determined using lead (210Pb) dating and sedimentation rates.

Results and discussion

Most upper lake sediments contained variable heavy metal concentrations, but became more consistent with depth and age. Five of the seven lakes exhibited Hg accumulation fluxes that peaked between 1920 and 1960, while the remaining two lakes exhibited recent (1995–2009) Hg flux spikes. Historical sediment accumulation rates and Hg flux profiles demonstrate similar peak and stabilized values. Mercury in the sampled South Dakota lakes appears to emanate from watershed transport due to erosion from agricultural land use common to the Northern Great Plains.

Conclusions

For sampled South Dakota lakes, watershed inputs are more significant sources of Hg than atmospheric deposition.

  相似文献   

17.
Reiji Kimura  Long Bai  Jiemin Wang 《CATENA》2009,77(3):292-296
We analyzed relationships among dust outbreaks, Normalized Difference Vegetation Indices (NDVI), and surface soil water content (0 to 2 cm depth) on the Loess Plateau, a significant dust source area of East Asia. World Surface Data for wind speed and current weather, coarse-resolution data for NDVI, and a three-layer soil model for surface soil water content were used. The threshold NDVI for preventing dust outbreaks was about 0.2 when the wind speed ranged from 7 to 8 m s− 1. This threshold NDVI corresponds to a vegetation cover of 18%. The threshold ratio of surface soil water content to the field capacity (θr) was about 0.2. Conditions facilitating dust outbreaks on the Loess Plateau are when NDVI is less than 0.2 with wind speed  7 m s− 1 and θr < 0.2, and when NDVI is greater than 0.2 with wind speed  9 m s− 1 and θr < 0.2.  相似文献   

18.
We studied the behavior of the trace elements (TE) As, Cu, Pb and Zn associated with sulphide minerals in tailings of different age at the Guanajuato mining district, Mexico. The objective was to determine the dominant fractions into which the TE move as tailings age and to identify how much time is needed until the dominant metal fractions approach equilibrium. We collected 21 samples from the surface of mine waste deposits of different ages (0, 2 , 4, 16, 70, 75, and 100 years), and measured their aqua regia extractable contents of As, Cu, Pb and Zn. We also applied a sequential extraction procedure to quantify water soluble TE as well as TE associated with carbonates, iron oxides, sulphides and the residual fraction. The mineralogy was analysed by X-ray diffraction, and selected samples were studied on polished specimens through a stereoscopic microscope. The TE in samples extracted with aqua regia ranged between 10 and 168 mg kg− 1 for As, 12 to 194 mg kg− 1 for Cu, 31 to 308 mg kg− 1 for Pb, and 122 to 1129 mg kg− 1 for Zn, and varied in a wide range within each age group of tailings. Water soluble Cu, Pb and Zn contents were below detection limits in almost all samples, which was attributed to the alkaline pH (7.17 to 8.61) in the tailings. Water extractable As was detected only in tailings older than 16 years, and concentrations ranged between 0.06 and 7.58 mg kg− 1. The proportion of TE associated with sulphides decreased in the tailings as they age, while the proportion of TE associated with iron oxides increased with time of exposure to the atmosphere, approximating equilibrium after 60 years for As, Cu and Zn, and after 40 years for Pb. Observations of polished specimens suggests that oxidation proceeds until coatings of secondary minerals cover and protect sulphide mineral grains from further weathering. First order rate equations were adjusted to the proportions of TE associated with either sulphides or iron oxides. Assuming that the TE in sulphide fractions correspond to arsenopyrite (FeAsS), chalcopyrite (CuFeS2), galena (PbS) and sphalerite (ZnS), the relative oxidation rate of sulphides followed the order: PbS > ZnS > FeAsS ≈ CuFeS2, while the relative affinity of the elements with iron oxides followed the sequence Cu ≈ Zn > As > Pb.  相似文献   

19.
On 26 December 2004, a tsunami caused extensive loss of life, damaged property and degraded agricultural land in the province of Aceh, Indonesia. While some of the associated soil chemical changes have been documented, information on soil physical properties is sparse. The objective of this study was to quantify physical properties of some tsunami-affected upland agricultural soils in Aceh, Indonesia. Soil was sampled approximately 21/2 years after the tsunami, from the 0–0.1 m, 0.1–0.3 m and 0.3–0.5 m depths in four sites in the villages of Kling Cot Aroun in Aceh Besar sub-district, Kuta Kruen in Aceh Utara sub-district, Udjong Blang Mesjid in Bireuen sub-district and Meue in Pidie Jaya sub-district on the east coast of Aceh. These sites were located within 1 km from the sea at elevations ranging from 0 to 5 m ASL. The soils were Ultisols except for Meue, which was an Entisol. Soil properties measured were bulk density, structural stability and particle size distribution. Soil water retention, pore-size distribution and saturated hydraulic conductivity were estimated by inserting the values of bulk density, clay, sand and silt contents into pedotransfer functions from the literature. The analyses conducted during this study did not permit us to ascertain what proportion of the soil particles were of tsunami-origin. Nonetheless, deposition of finer-textured material may have occurred in two of the sites. In comparison with the greyish-white, coarse textured soil in the rest of the profile, a finer-textured yellow horizon was present in the lower slopes of the Udjong Blang Mesjid site. At Meue, clay and silt contents were higher in the surface 0.3 m than in the 0.3–0.5 m depth, although a distinct horizon was absent. Particle size distribution in all sites was dominated by the sand fraction, although clay and silt contents were relatively high (20–30 g 100 g− 1) at Kuta Kruen. Among the sand fractions, fine sand (0.02–0.25 mm) was highest at Kling Cot Aroun, Kuta Kruen and in the “yellow horizon” at Udjong Blang Mesjid, making them more prone to hardsetting and compaction after intensive tillage. Soil compaction was present in all sites with that in the “yellow horizon” at Udjong Blang Mesjid being highest. The relatively low porosity in this layer may be beneficial, as it is likely to reduce the high rates of water drainage and nutrient leaching in this sandy soil. The more compacted soils were characterised by higher numbers of micropores (r, pore radius < 4.3 μm), lower water retention at saturation, smaller numbers of macropores (r > 14.3 μm), lower hydraulic conductivity and intensive gleying, indicating frequent waterlogging. The soils in all depths from Kling Cot Aroun and the “yellow horizon” at Udjong Blang Mesjid were very dispersive, that at Meue moderately dispersive in the 0.3–0.5 m depth but stable in the 0–0.1 m depth, and at Kuta Kruen very stable in all depths. Soil physical degradation was a feature of the soils examined, and its amelioration will be the key to improving and sustaining crop yields in these soils. Possible management interventions include organic amendments such as compost or manure, and minimum tillage options such permanent beds or zero tillage with retention of crop residues as in situ mulch together with suitable cover crops.  相似文献   

20.
A study was carried out on the adsorption of Co2+, Cu2+, Pb2+, and Zn2+ ions on mixed Fe-Al oxides inthe absence or presence of increasing concentrations of oxalate or tartrate. Mixed Fe-Al oxides were prepared by precipitating at pH 5.5 mixtures of Fe and Al ions at initial Fe/Al molar ratios (R) of 0, 1, 2, 4, 10 and ∞ (R0, R1, R2, R4, R10 and R∞).The oxides aged 7 days at 20 °C or 30 days at 50 °C showed different chemical composition and physico-chemical and mineralogical properties. All the mixed Fe-Al oxides showed presence of poorly crystalline materials (ferrihydrite) even after prolonged aging. The heavy metals wereselectively adsorbed on the oxides. For all the precipitates aged7 days at 20 °C, the selectivity sequence wasPb2+> Cu2+ > Zn2+ > Co2+, but the pH at which 50% ofeach cation was adsorbed (pH50) was different from sample tosample. It was found that usually the greater the amounts of Fe in Fe-Al gels the lower the pH50 for each metal, but the adsorption of a heavy metal was not linearly related to Fe content. The pH50 usually did not change significantly when the oxides were aged 30 days at 50 °C. Competitive adsorption of Cu and Zn on ferrihydrite (R∞) showed thatCu strongly prevented Zn adsorption even at an initial Zn/Cu molar ratio of 8, whereas Cu sorption was not inhibited. In thepresence of oxalate (OX) or tartrate (TR) (organic ligand/Pb molar ratio (rL) from 0 to 7) the quantities of Pb adsorbedon the Fe-Al oxides usually increased with increasing rL. The adsorption increase of Pb was particularly high on the oxidesricher in Fe (R4-R∞), but a significant increase was also observed on R0-R2 samples. The adsorption of Pb on the oxides hasbeen influenced not only by the presence and concentration of organic ligands but also by the sequence of addition of Pb and tartrate on the sorbents. It has been ascertained that on each oxide the greater amounts of Pb were adsorbed when tartrate wasadded before Pb and usually according to the following sequence: Tr before Pb > Pb before Tr > Pb + Tr > Pb.  相似文献   

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