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1.
Abstract

Intake and uptake of lead in the general population is mainly via the gastro-intestinal (Gl) tract. Those biological and biophysico-chemical factors operating in the Gl tract are the main determinants of Pb bioavailability. They include sites of Pb uptake, the physiology of uptake/transport to blood, the stage of development, interactions of Pb with nutrients, and Gl biochemical transformations of ingested material. Lead uptake occurs as ion or complex, from micelles and perhaps by pinocytosis in the infant. Uptake is mainly via the duodenum but other sites can participate, e.g. ileum (pinocytosis) and colon. Transport to blood is by active, carrier-mediated transport and passive diffusion. Uptake may include movement through intercellular tight junctions.

Lead uptake is affected by nutrients in the Gl tract, operating synergistically or antagonistically. Iron and calcium interactions are most important and augment those also occurring in vivo in tissues.

Liberation of lead from diverse ingested media, e.g. food, paint, soil and dust, mining waste, is affected by their chemical/physical forms, hydrolytic and oxidative processes in gastric fluid and other Gl sites. Such changes in vivo are poorly simulated by in vitro tests. The downward revision of blood lead (Pb-B) levels considered ‘safe’, to about 0.5 μmol L?1 (10μg dL?1) or lower, causes even sources of moderately bioavailable Pb to become important.  相似文献   

2.
Abstract

This paper considers selected field examples of physical and chemical properties of soil and some of the interactions with gut physiological processes that are related to lead bioavailability. The blood lead response to quantity of lead in mining and milling environments compared with urban and lead smelter conditions appears to be different. The emphasis of this paper is to understand the complexity of the urban environment.

Bioavailability appears to be related to physical and chemical qualities other than mere quantity of lead. Particle size is one physical quality that influences bioavailability. Compared to intact lead—based paint, small particle emissions from vehicles govern the general soil lead pattern in urban environments. Lead has accumulated in soils in proportion to city size, with the inner—city generally measuring the highest lead levels. The soil lead situation is further exacerbated by the chemical influence of other toxic substances such as zinc. In several cities, zinc levels of 1,500 ppm and higher, plus acid conditions (pH 5.4 and lower) have been observed. This condition is phytotoxic to plants and the deficiency of plant cover increases the likelihood for soil lead ingestion. After ingestion, nutritional status becomes an important factor with both iron and calcium deficiencies increasing lead bioavailability.

To complement the other discussions of the Gl tract and bioavailability in this volume, the following physiological responses of the gut that either increase or decrease soil lead bioavailability are described: (1) The role of the ‘normal’ microbial flora in altering baseline gut function, (2) effect of pH, (3) intestinal transit time, (4) role of mucus, and (5) barriers to lead transport. Physiologically there are nine physical and/or chemical barriers to soil lead absorption which tend to decrease bioavailability: any breakdown of or increased permeability in these barriers would have the opposite effect. The addition of a soil amendment, such as pathogen free processed sludge, would be expected to be a practical means for reducing soil lead bioavailability. The amendment should serve to bind lead and thus increase effective particle size. It would also have the benefit of improving plant growth as shown in the laboratory. Further study is needed to conduct toxicity testing and undertake field evaluation.  相似文献   

3.
Abstract

The purpose of this study was to determine the extent of absorption of lead (Pb) in mining waste soil from Butte, Montana. It is the first study to fully investigate the bioavailability of lead in soils containing mine waste using a soil dose response approach. Young 7–8 week-old male and female Sprague-Dawley rats (5 animals/sex/group) were given mining waste soil [810 ppm lead (Test Soil I) or 3,908 ppm lead (Test Soil III)] mixed in a purified diet (AIN—76?) at four different dose levels (0.2, 0.5, 2 and 5% dietary soil) for 30 consecutive days. The test soil dose levels at 2 and 5% were chosen to bracket a pica-for-soil child's soil exposure levels. A pica-for-soil child is a young child who eats large quantities of soil (10 g day?1). Standard groups included untreated controls and dosed feed soluble lead acetate groups (1, 10, 25, 100 and 250 μg Pb g?1 feed). The concentrations of lead acetate were chosen to bracket the test soil dose levels of lead. Liver, blood and femur, representing the three compartments in which lead is distributed in the body, were analyzed for total lead concentration using graphite furnace atomic absorption spectroscopy. Clinical signs, body weight, food consumption and liver weights for treated and standard groups were similar to control. Tissue lead concentrations from test soil animals were significantly lower than the tissue concentrations for the dosed feed lead acetate group. Group mean whole blood, bone and liver lead concentrations increased with increasing dose levels for most treatment groups. The increases in blood, bone and liver lead concentrations were not proportional with increasing dose levels and plateaued at the high dose levels. Relative percent bioavailability values, based on dosed feed soluble lead as the standard, were independent of the two different test soils, dose levels or sex, and only slightly dependent on the tissue (blood > bone, liver). Overall relative percent bioavailability values were 20% based on the blood data; 9% based on the bone data; and 8% based on the liver data (2 and 5% dose levels only). The results of this study will provide the scientific validity needed to determine the significance of lead exposure from Butte soils in assessing human health risks as part of the Superfund Remedial Investigation/Feasibility Study process.  相似文献   

4.
Anthropogenic sources of lead contamination in soils include mining and smelting activities, effluents and wastes, agricultural pesticides, domestic garbage dumps, and shooting ranges. While Pb is typically considered relatively insoluble in the soil environment, some fungi may potentially contribute to mobilization of heavy metal cations by means of secretion of low-molecular-weight organic acids (LMWOAs). We sought to better understand the potential for metal mobilization within an indigenous fungal community at an abandoned shooting range in Oak Ridge, TN, where soil Pb contamination levels ranged from 24 to >2,700 mg Pb kg dry soil(-1). We utilized culture-based assays to determine organic acid secretion and Pb-carbonate dissolution of a diverse collection of soil fungal isolates derived from the site and verified isolate distribution patterns within the community by 28S rRNA gene analysis of whole soils. The fungal isolates examined included both ascomycetes and basidiomycetes that excreted high levels (up to 27 mM) of a mixture of LMWOAs, including oxalic and citric acids, and several isolates demonstrated a marked ability to dissolve Pb-carbonate at high concentrations up to 10.5 g liter(-1) (18.5 mM) in laboratory assays. Fungi within the indigenous community of these highly Pb-contaminated soils are capable of LMWOA secretion at levels greater than those of well-studied model organisms, such as Aspergillus niger. Additionally, these organisms were found in high relative abundance (>1%) in some of the most heavily contaminated soils. Our data highlight the need to understand more about autochthonous fungal communities at Pb-contaminated sites and how they may impact Pb biogeochemistry, solubility, and bioavailability, thus consequently potentially impacting human and ecosystem health.  相似文献   

5.
Several anthropogenic and natural sources are considered as the primary sources of toxic metals in the environment. The current study investigates the level of heavy metals contamination in the flora associated with serpentine soil along the Mafic and Ultramafic rocks northern-Pakistan. Soil and wild native plant species were collected from chromites mining affected areas and analyzed for heavy metals (Cr, Ni, Fe, Mn, Co, Cu and Zn) using atomic absorption spectrometer (AAS-PEA-700). The heavy metal concentrations were significantly (p < 0.01) higher in mine affected soil as compared to reference soil, however Cr and Ni exceeded maximum allowable limit (250 and 60 mg kg?1, respectively) set by SEPA for soil. Inter-metal correlations between soil, roots and shoots showed that the sources of contamination of heavy metals were mainly associated with chromites mining. All the plant species accumulated significantly higher concentrations of heavy metals as compared to reference plant. The open dumping of mine wastes can create serious problems (food crops and drinking water contamination with heavy metals) for local community of the study area. The native wild plant species (Nepeta cataria, Impatiens bicolor royle, Tegetis minuta) growing on mining affected sites may be used for soil reclamation contaminated with heavy metals.  相似文献   

6.
Schaaf  W.  Gast  M.  Wilden  R.  Scherzer  J.  Blechschmidt  R.  Hüttl  R. F. 《Plant and Soil》1999,213(1-2):169-179
Lignite and pyrite contents in the dump materials of the Lusatian opencast mining district in East Germany result in high acidification and salinization potentials. These extreme conditions require considerable amounts of alkaline materials like ash or lime to enable recultivation and revegetation. Investigations at chronosequence sites on different mining substrates show characteristic developments of the soil solution chemistry. Processes like weathering of primary and formation of secondary mineral phases, acid production and buffering, and their impacts on both the solid and the liquid soil phase result in high temporal and spatial dynamics especially in the initial phase of soil and ecosystem development. To study these processes we continuously collected soil solutions from different soil depths at seven sites with two representative soil substrates. All sites were afforested with pine and cover stand ages from 1 to 60 yr. The results show that actual pyrite oxidation occurs at the youngest sites on lignite and pyrite containing substrates leading to extremely low pH values and high Fen+ and SO4 2- concentrations. The considerable acid production causes weathering of aluminium silicates resulting in high Aln+ concentrations. Ca2+ concentrations are unexpectedly high even at low pH showing no correlation to amelioration amounts or depths. Therefore it seems most probable that these mining substrates contain geogenic Ca sources. The transport of dissolved weathering products is limited due to low leaching rates enabling formation of secondary phases which control the actual composition of the soil solution. Depth gradients of the soil solution composition at the chronosequence sites point to a gradual transport and leaching of these secondary phases from the soil profiles. Soil solution composition and dynamics at lignite and pyrite free sites show completely different patterns and have a higher potential for successful sustainable recultivation. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

7.
The bioavailability of lead from various milk diets was studied in 14 day old suckling rats. Human milk, infant formula, cow's milk, rat milk and deionized water labeled with 203Pb were given to rat pups by gastric intubation. Animals were killed after 2 or 6 h and the radioactivity in the tissues was measured. At 2 h after administration the lead bioavailability, defined as lead uptake in the body, excluding the gastrointestinal tract, was 47% from water, 42% from human milk, 40% from infant formula, 31% from cow's milk and 11% from rat milk. After 6 h the bioavailability of lead was about 50% from water and human milk, 45% from infant formula and cow's milk, and 36% from rat milk. The blood lead levels in the pups reflected the total body uptake and were also correlated to the brain lead levels. Thus, rat pups given lead in human milk had approximately twice as high lead levels in blood and brain than pups given lead in rat milk. The intestinal absorption of lead was dependent on the milk diet given to the sucklings. In duodenum, the highest uptake of lead was found in rats given water or human milk, whereas in rats given rat or cow's milk the highest uptake of lead was found in ileum. The distribution of lead in cream, whey and casein fractions of the milk diets after in vitro labeling with 203Pb was also studied. The casein fraction in cow's and rat milk contained 90–96% of the total amount of lead in the diet. In infant formula and human milk, 77 and 56% lead was found in the casein fraction, respectively. The higher lead bioavailability observed in the suckling rat fed human milk than in those fed rat and cow's milk may partly be explained by a lower proportion of lead bound to casein in human milk.  相似文献   

8.
Ecological systems are severely damaged by the anthropogenic disturbance of mining. Phosphate open-pit mining fields cover over 200 km2 of the Negev desert, Israel. However, the effects of the ongoing mine site restoration efforts on the plant community have not been studied. Plants and their seed banks have a major role in ecosystem processes and restoration. In this study, we focused on three mining sites, restored in different years, along Zin River valley. We compared the plant community of restored mining plots within these areas to adjacent natural plots. We asked whether plant community germination potential from the soil seed bank differs between the restored plots and the adjacent natural plots within a mining site. We hypothesized that: (1) there is a lack of seed bank in the restored plots; (2) the altered soil composition at the restored plots inhibits germination. We used soil samples collected from the different mining sites and set up greenhouse experiments. One experiment compared natural and restored areas with different soil treatments. In another experiment, we added native seeds to test their germination potential on restored soil. Our results indicate that lack of seed bank is the major limiting factor hindering germination and not the composition of the soil after restoration. Our findings shed light on the constraints of seed bank establishment in post-mining areas of hyper-arid regions. We suggest considering active restoration practices to facilitate natural dispersal and improve seed bank establishment.  相似文献   

9.
In the pharmaceutical industry, orally active compounds are required to have sufficient water solubility to enable dissolution within the gastrointestinal tract prior to absorption. Limited dissolution within the gastrointestinal tract often reduces the bioavailability of hydrophobic drugs. To improve gastrointestinal tract dissolution, nonaqueous solvents are often used in the form of emulsions and microemulsions. Here, we show that oil-free polyelectrolyte nanosystems (micellar dispersions and 100-300 nm particles) prepared from poly(ethylenimines) derivatized with cetyl chains and quaternary ammonium groups are able to encapsulate high levels of hydrophobic drug (0.20 g of drug per g of polymer) for over 9 months, as demonstrated using cyclosporine A (log P = 4.3). The polyelectrolytes facilitate the absorption of hydrophobic drugs within the gastrointestinal tract by promoting drug dissolution and by a hypothesized mechanism involving paracellular drug transport. Polyelectrolyte nanoparticle drug blood levels are similar to those obtained with commercial microemulsion formulations. The polyelectrolytes do not promote absorption by inhibition of the P-glycoprotein efflux pump.  相似文献   

10.
Current soil quality evaluation does not include an assessment of metal bioavailability to organisms. However, sentinel soil-dwelling invertebrates can be used for such an assessment. This study aims to establish the modulating soil parameter of metal bioavailability to snails and a procedure for ranking field sites (n = 9; 43 plots) based on the evaluation of the transfer of metals to the land snails used as indicators of metal zooavailability. Multivariate regressions identify soil pH, organic carbon and iron oxides influence cadmium, chromium, copper, lead and zinc zooavailability to snails underlining the need to consider other parameter than total soil concentration during bioavailability assessment. However, for As, no influence of soil parameter on it bioavailability to snails was identified. Internal Concentrations of Reference (CIRef) of Cd, Pb, As, Cr, Cu and Zn were determined in Cantareus aspersus that were caged on unpolluted plots. CIRef allow for the identification of contaminated sites. CIRef have revealed unexpected metal transfer on some “unpolluted” sites and a lack of transfer on some contaminated sites, thus confirming the necessity for biological measures to evaluate metal mobility. The Sum of Excess of Transfers (SET) index ranked the industrially impacted sites as the top priorities for management.We recommend that the SET methodology be used for future environmental risk assessment. By highlighting real metal transfers and considering the numerous parameters influencing environmental bioavailability, the snails watch provides information on environmental quality.  相似文献   

11.
We present the rationale for a cross‐disciplinary investigation addressing the ‘Devonian plant hypothesis’ which proposes that the evolutionary appearance of trees with deep, complex rooting systems represents one of the major biotic feedbacks on geochemical carbon cycling during the Phanerozoic. According to this hypothesis, trees have dramatically enhanced mineral weathering driving an increased flux of Ca2+ to the oceans and, ultimately, a 90% decline in atmospheric CO2 levels through the Palaeozoic. Furthermore, experimental studies indicate a key role for arbuscular mycorrhizal fungi in soil–plant processes and especially in unlocking the limiting nutrient phosphorus in soil via Ca‐phosphate dissolution mineral weathering. This suggests co‐evolution of roots and symbiotic fungi since the Early Devonian could well have triggered positive feedbacks on weathering rates whereby root–fungal P release supports higher biomass forested ecosystems. Long‐standing areas of uncertainty in this paradigm include the following: (1) limited fossil record documenting the origin and timeline of the evolution of tree‐sized plants through the Devonian; and (2) the effects of the evolutionary advance of trees and their in situ rooting structures on palaeosol geochemistry. We are addressing these issues by integrating palaeobotanical studies with geochemical and mineralogical analyses of palaeosol sequences at selected sites across eastern North America with a particular focus on drill cores from Middle Devonian forests in Greene County, New York State.  相似文献   

12.
The application of biological processes in restoring oil polluted sites is growing due to their efficiency in removing different classes of pollutants. The aim of this study was to determine the ability of microorganisms present in a drilling-waste polluted soil (36,200 mg TPH kg?1 soil) to remove weathered hydrocarbons under stimulated and non-stimulated soil conditions. The hypothesis under study was whether petroleum hydrocarbons removal could be enhanced by manipulating C/N ratio, water content and addition of three agroindustrial wastes. A Box-Behnken design was employed to evaluate the effect of each variable. Results demonstrated that, for orange peels and banana trunk treatments, the variable with the largest effect (p < 0.01) on hydrocarbon removal was the C/N ratio, indicating that higher ratio (100/3) improved removal (79.5–82%). The largest effect (p < 0.001) on hydrocarbon removal for pineapple wastes was observed with higher water content (60%) achieving the highest removal (89%). After 90 days of experimentation, the type of agricultural waste and the agricultural waste/soil ratio were not statistically significant in any treatment. However, their addition was important relative to non-stimulated soil, which showed a hydrocarbon removal of 17%. Data reported in this study showed the application of bioremediation in clay and drilling waste-polluted soils.  相似文献   

13.
Chemical fractionation methods may be capable of providing an inexpensive estimate of contaminant bioavailability and risk in smelter-contaminated soil. In this study, the relationship between metal fractionation and methods used to estimate bioavailability of these metal contaminants in soil was evaluated. The Potentially BioAvailable Sequential Extraction (PBASE) was used for Cd, Pb, and Zn fractionation in 12 soils contaminated from Pb and Zn mining and smelting activities. The PBASE procedure is a four-step sequential extraction: extraction 1 (E1) is 0.5 M Ca(NO3)2, E2 is 1.0 M NaOAc, E3 is 0.1 M Na2EDTA, and E4 is 4 M HNO3. Metal bioavailability for two human exposure pathways, plant uptake (phytoavailability) and incidental ingestion (gastrointestinal, Gl, availability), was estimated using a lettuce (Lactuca sativa L.) bioassay and the in vitro-Gl Physiologically Based Extraction Test(PBET). Metal in the PBASE E1 fraction was correlated with lettuce Cd (P < 0.001) and Zn (P < 0.05) and was the best predictor of Cd and Zn phytoavailability. Only total metal content or the sum of all PBASE fractions, ΣE1–4, were correlated (P < 0.001) with PBET gastric phase for Pb. The sum of the first two PBASE fractions, ΣE1–2, was strongly correlated (P < 0.001) with Pb extracted by the PBET intestinal phase. The PBASE extraction method can provide information on Cd and Zn phytoavailability and Gl availability of Pb in smelter-contaminated soils.  相似文献   

14.
Soils contaminated with toxic metals may be environmental hazards and sources of exposure to human population. Soils in mining areas are among the most heavily contaminated by metals from the mining activity. This study was focused on metals of interest in bioavailability studies using single and sequential extraction methods. Results of geochemical fractionation suggest that changes in soil characteristics may enhance the mobilization of Cu, Cr, Zn, and Al. The observed metals’ availability pattern was Cr > Cu > Zn > Al. However, the pattern of total contents of metals in soils was Al > Cr > Zn > Cu. Risks to human adults and children from selected metals through soil ingestion was assessed in terms of incremental lifetime average daily dose (LADD), hazard quotient (HQ), and hazard index (HI). The estimated LADDs and HI were within acceptable reference doses and less than 1, respectively, indicating low risk to human populations from the studied metals through soil ingestion in the studied mine area. The generated data may be useful in remediation of contaminated soils with metals.  相似文献   

15.
Column‐scale oil flushing of a sandy loam contaminated with either Pb(II) (500 mg/kg Pb), PbSO4 (10,000 mg/kg Pb), PbCO3 (10,000 mg/kg Pb), or Pb‐naphthalene (400 mg/kg Pb, 333 mg/kg naphthalene) was investigated. HCl (0.1 N), EDTA (0.01 M), and CaCl2 (1.0 M) were selected as the soil‐flushing solutions based on soil‐washing experiments. For the Pb‐only tests, Pb removal efficiencies were 85, 100, and 78% for HCl, EDTA, and CaCl2, respectively. For PbSO4 (s), Pb removal efficiencies were 32, 100, and 96% for HCl, EDTA, and CaCl2, respectively, and for PbCO3 were 97, 100, and 14% for HCl, EDTA, and CaCl2, respectively. Larger amounts of flushing solutions were required for the remediation of PbSO4‐and PbCO3‐contaminated soils compared with the Pb‐only tests, most likely because of slower dissolution kinetics and the neutralization of HCl by CO3 ‐2 For Pb‐naphthalene, Pb removal efficiencies were 78 and 72% for HCl and EDTA, respectively, which compared well with soil‐washing results but were less than those observed in Pb‐only column studies.  相似文献   

16.
The bioavailability of trace elements in soils is conditioned by both physico-chemical and biological parameters. In this study, the accumulation kinetics of cadmium (Cd), lead (Pb), arsenic (As) and antimony (Sb) were determined for 3 industrially impacted sites to assess the bioavailability of these contaminants to the garden snail (Cantareus aspersus). Mono and multivariate regressions allowed the identification of cation exchange capacity (CEC), silts and organic carbon content as the soil parameters modulating the in situ bioavailability of Cd and Pb. For all elements, the total concentrations in the soils were not good predictor (not significant correlation) of the bioavailability to snails. The Cd, As and Sb assimilation fluxes were correlated with the calcium chloride (CaCl2) extract concentrations, but this correlation was not observed with Pb. The total soil concentration coupled with soil properties best explained the variation in Pb assimilation, whereas their influences on Cd bioavailability were lower, signifying that other parameters such as contamination sources may modulate Cd bioavailability. Here, the As and Sb in situ accumulation kinetics are described for the first time and highlighted a slight bioavailability to snails at the studied sites. The absence of a correlation between the As or Sb assimilation fluxes and total metals in the soil coupled with the absence of influence of soil properties on their bioavailability may result from the speciation of these metalloids, which are known to modulate their mobility in soils. This study highlights the need to consider both physico-chemical and biological aspects of metal and metalloid bioavailability to assess the risk of metal transfer from soil to organisms.  相似文献   

17.
Abstract

The chemical fractionation of lead, cobalt, chromium, nickel, zinc, cadmium and copper in soils around Lakwa oil field, Assam, India was studied using a sequential extraction method. It is evident from the study that the residual fraction is the most important phase for the seven heavy metals under study. Among non-residual fractions metals are mostly associated with the Fe–Mn oxides fraction. The association of heavy metals with organic matter was observed in the following order: copper> cadmium> zinc> lead. The concentration of Pb in the carbonate fraction for both the seasons is higher compared with other metals, which may pose environmental problems due to its highly toxic nature. The comparatively low concentration of metals in the exchangeable fraction indicates low bioavailability. Correlations between physicochemical parameters and metal fractions of soil do not show consistent behaviour. The local mean values of metals when compared with the accepted values of normal abundance and geochemical background, indicates two to four fold increases in this area. However, the values are within the range of normal abundance. As well as from natural soil geochemical behaviour, anthropogenic influence might have a close bearing on the association of metals with the soil system in the studied area.  相似文献   

18.
The vast majority of antibiotic resistant genes (ARG) acquired by human pathogens have originated from the natural environment. Therefore, understanding factors that influence intrinsic levels of ARG in the environment could be epidemiologically significant. The selection for metal resistance often promotes AR in exposed organisms; however, the relationship between metal levels in nature and the intrinsic presence of ARG has not been fully assessed. Here, we quantified, using qPCR, the abundance of eleven ARG and compared their levels with geochemical conditions in randomly selected soils from a Scottish archive. Many ARG positively correlated with soil copper levels, with approximately half being highly significant (p<0.05); whereas chromium, nickel, lead, and iron also significantly correlated with specific ARG. Results show that geochemical metal conditions innately influence the potential for AR in soil. We suggest soil geochemical data might be used to estimate baseline gene presence on local, regional and global scales within epidemiological risk studies related to AR transmission from the environment.  相似文献   

19.
Salt marshes near urban, industrial and mining areas are often affected both by heavy metals and by eutrophic water. The aim of this study was to assess and evaluate the main processes involved in the decrease of nitrate concentration in pore water of mine wastes flooded with eutrophic water, considering the presence or absence of plant rhizhosphere. Basic (pH ∼ 7.8) carbonated loam mine wastes and free-carbonated acidic (pH ∼ 6.2) sandy-loam mine wastes were collected from polluted coastal salt marshes of SE Spain which regularly receive nutrient-enriched water. The wastes were put in pots and flooded for 15 weeks with eutrophic water (dissolved organic carbon ∼26 mg L−1, PO43− ∼23 mg L−1, NO3 ∼180 mg L−1). Three treatments were assayed for each type of waste: pots with Sarcocornia fruticosa, pots with Phragmites australis and unvegetated pots. Soluble organic carbon, nitrate, soluble Cd, Pb and Zn, pH and Eh were monitored. But the 2nd day of flooding, nitrate concentrations had decreased between 70% and 90% (equivalent to 1.01-1.12 g N-NO3 m−2 day−1) with respect to the content in the water used for flooding, except in unvegetated pots with acidic wastes. Denitrification was the main mechanism associated with the removal of nitrate. The role of vegetation in improving the rhizospheric environment was relevant in the acidic wastes because higher sand content, lower pH and higher soluble metal concentrations might strongly hinder microbial activity Hence, revegetation of salt marshes polluted by acidic sandy mining wastes might improve the capacity of this type of environment to act as a green filter against excessive nitrate contents flowing through them.  相似文献   

20.
Carabid beetles were monthly sampled with pitfall traps in the ancient Pb-Zn mining area of Plombières during one year. Based on the total soil concentrations of lead, zinc, cadmium and copper, it was expected that zinc would probably have the most adverse effects on the populations. Activity and species richness of carabid beetles were, however, not significantly correlated with total zinc concentration nor with the water soluble and the calciumchloride extractable concentration. In fact, despite the high soil concentrations, carabid beetles did not seem to be affected in the study area. The apparent lack of effects at the high observed zinc concentrations is probably caused by the low bioavailability of zinc to the beetles in the litter of the study sites which was also reflected in the low observed water soluble zinc concentrations.  相似文献   

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