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PubMed2004

Electrokinetic remediation of a Cu contaminated red soil by conditioning catholyte pH with different enhancing chemical reagents.

The effect of enhancement reagents on the efficiency of electrokinetic remediation of Cu contaminated red soil is evaluated. The enhancement agents were a mix of organic acids, including lactic acid+NaOH, HAc-NaAc and HAc-NaAc+EDTA. The soil was prepared to an initial Cu concentration of 438 mgkg(-1) by incubating the soil with CuSO4 solution in a flooded condition for 1 month. Sequential extraction showed that Cu was partitioned in the soil as follows: 195 mgkg(-1) as water soluble and exchangeable, 71 mgkg(-1) as carbonate bound and 105 mgkg(-1) as Fe and Mn oxides. The results indicate that neutralizing the catholyte pH maintains a lower soil pH compared to that without electrokinetic treatment. The electric currents varied depending upon the conditioning solutions and increased with an increasing applied voltage potential. The electroosmotic flow rate changed significantly when different conditioning enhancing reagents were used. It was observed that lactic acid+NaOH treatments resulted in higher soil electric conductivities than HAc-NaAc and HAc-NaAc+EDTA treatments. Ultimately, enhancement by lactic acid+NaOH resulted in highest removal efficiency (81% Cu removal) from the red soil. The presence of EDTA did not enhance Cu removal efficiencies from the red soil, because EDTA complexed with Cu to form negatively charge complexes, which slowly migrated toward the anode chamber retarding Cu2+ transport towards the cathode.

Acetic Acid↗
PubMed2005

Effect of heavy metals on soil microbial activity and diversity in a reclaimed mining wasteland of red soil area.

The microbial biomass, basal respiration and substrate utilization pattern in copper mining wasteland of red soil area, southern China, were investigated. The results indicated that soil microflora were obviously different compared with that of the non-mine soil. Microbial biomass and basal respiration were negatively affected by the elevated heavy metal levels. Two important microbial ecophysiological parameters, namely, the ratio of microbial biomass C(Cmic)/organic C(Corg) and metabolic quotient(qCO2) were closely correlated to heavy metal stress. There was a significant decrease in the Cmic/Corg ratio and an increase in the metabolic quotient with increasing metal concentration. Multivariate analysis of Biolog data for sole carbon source utilization pattern demonstrated that heavy metal pollution had a significant impact on microbial community structure and functional diversity. All the results showed that soil microbiological parameters had great potential to become the early sensitive, effective and liable indicators of the stresses or perturbations in soils of mining ecosystems.

Analysis of Variance↗
PubMed2006

[Nutrient leaching and acidification of Southern China coniferous forest red soil under stimulated N deposition].

In an eight months interval leaching experiment with soil column (10 cm in diameter and 60 cm in height) at 20 degrees C, this paper studied the effects of N deposition on the leaching losses of soil NO -, NH4+ , H+, Ca2+, Mg2+ , K+, and Na+ , and on soil acidification. Soil columns were taken from the coniferous forest experimental plot at the Red Soil Ecological Experiment Station of Chinese Academy of Sciences in Southern China, and the N deposition loads were 0, 7.8, 26 and 52 mg N x month (-1) x column (-1) , respectively. The results indicated that the leaching losses of total exchangeable cations, Ca2+ , and Mg2+ increased with increasing N deposition loads, but K+ and Na+ were little affected. The proportion of net cations leaching loss (difference of cations in eluate and leachate) to total exchangeable cations was 13.9% , 18.6% , 31.8% and 57.9% under 0, 7.8, 26 and 52 mg N x month (-1) column (-1) deposition loads, respectively, and that for exchangeable Ca2+ and Mg2+ was 19. 6%, 25.8% , 45. 3% and 84.8% , and 4.4% , 6.1% , 10. 9% and 17.1% , respectively. The leaching losses of inorganic N, NO3- and H+ also increased with increasing N deposition loads. Topsoil pH decreased with increasing N deposition loads, being 3.85, 3.84, 3.80 and 3.75 under 0, 7.8, 26 and 52 mg N x month (-1) x column(-1) N deposition loads, respectively. N deposition could increase the apparent mineralization rate of soil organic nitrogen, and accelerate the nutrient losses and acidification of coniferous forest red soil.

Acid Rain↗
PubMed2005

[Relationships between red soil enzyme activity and fertility].

Correlation and cluster analyses on the enzyme activities and chemical-biological properties of eight red soils showed that soil urease, invertase, phosphatase and catalase activities correlated significantly with soil organic carbon, total nitrogen and total phosphorous. Similar results of soil fertility evaluation were obtained by using soil enzyme activities and by using soil chemical-biological properties, indicating that soil enzyme activity could be used as an index of evaluating red soil fertility. The enzyme activities of fresh soil were generally greater than those of air-dried sample, and more closely correlated with soil fertility.

Catalase↗
PubMed2006

[Research advances in carbon balance in subtropical hilly red soil].

Carbon balance is becoming a hotspot in global change and geo-science studies. The subtropical hilly red soil area in China is an important production base of foodstuffs and tropical and subtropical economical crops and woods, and also, is very important in carbon balance research because of its special ecological and geographic characters. This paper discussed the significance of subtropical hilly red soil in carbon balance, and reviewed the related research advances and main results, including plant, litterfall, soil carbon storage, and soil respiration etc. The integrative research methods of carbon balance were summarized, and some issues and development directions in carbon balance research were discussed.

Carbon↗
PubMed2004

[Effects of different vegetation restoration of degraded red soil on earthworm population dynamics].

This study was conducted at the long-term experimental plots in Ecological Experimental Station of Red Soil in Yujiang County (28 degrees 15'30''N, 116 degrees 55'30''E ), Jiangxi Province, subtropical China. Earthworm population was investigated seasonally from May 1999 to February 2000, under different vegetations including four artificial woodlands [deciduous broadleaf woodland (Quercus chenii, Qc), evergreen broadleaf woodland (Schima superba, Ss), coniferous woodland (Pinus massonina, Pm) and mixed woodland (Schima superba-Pinus massonina, Sm)], two grasslands [gently-disturbed grassland (G1), undisturbed grassland (G2)] and control wasteland (CK). The results indicated that the population structure was very simple. Only Drawinda gisti characterized by pioneer was found. The seasonal averages of density and biomass were in the order of G2 > G1 > Qc > Ss > Pm > Sm > CK, and those of G2, G1 and Qc were significantly higher than those of the latters (P < 0.05). Seasonal fluctuations were obvious with dry-hot summer depressing the earthworm population sharply, leading to the aestivation of earthworm. Based on the variation coefficients of density and biomass, Qc had the highest ecosystem stability, followed by Sm and Ss, and G1, G2, and Pm had the lowest stability. The overall differentiation of earthworm population could be drawn through canonical discriminant analysis. There were significant correlations between earthworms and some soil properties (P < 0.01). Overall, the differentiation of earthworm population was driven by the quantity and quality of soil organic matter returned by the vegetations. Additionally, based on earthworm population, the importance of selecting appropriate vegetation types during the restoration of degraded red soil was emphasized.

Animals↗
PubMed2005

Water and heat transport in hilly red soil of southern China: II. Modeling and simulation.

Simulation models of heat and water transport have not been rigorously tested for the red soils of southern China. Based on the theory of nonisothermal water-heat coupled transfer, a simulation model, programmed in Visual Basic 6.0, was developed to predict the coupled transfer of water and heat in hilly red soil. A series of soil column experiments for soil water and heat transfer, including soil columns with closed and evaporating top end, were used to test the simulation model. Results showed that in the closed columns, the temporal and spatial distribution of moisture and heat could be very well predicted by the model, while in the evaporating columns, the simulated soil water contents were somewhat different from the observed ones. In the heat flow equation from Taylor and Lary (1964), the effects of soil water evaporation on the heat flow is not involved, which may be the main reason for the differences between simulated and observed results. The predicted temperatures were not in agreement with the observed one with thermal conductivities calculated by de Vries and Wierenga equations, so that it is suggested that K(h), soil heat conductivity, be multiplied by 8.0 for the first 6.5 h and by 1.2 later on. Sensitivity analysis of soil water and heat coefficients showed that the saturated hydraulic conductivity, K(S), and the water diffusivity, D(theta), had great effects on soil water transport; the variation of soil porosity led to the difference of soil thermal properties, and accordingly changed temperature redistribution, which would affect water redistribution.

Journal Article↗
PubMed2004

[Bio-environmental effects and index of remediation of multi-heavy metals polluted red soils].

A pot experiment was conducted to study the bio-environmental effects of lime and organic manure application on red soil and paddy soil derived from red sandstone and polluted by multi-heavy metals. The results indicated that liming decreased the content of soil bioavailable Cu and Pb extracted with 0.05 mol/L HCl, while applying hog manure increased that of Cd. Soil bioavailable heavy metals (HMs) showed an apparent relationship with soil dissolved carbon. Applying lime and organic manure has a positive physiological effect on soil microorganisms and sweet potato. Many indexes, i.e. the number of soil actinomycetes, the content of HMs in the root of sweet potato, showed the remarkable relationship with soil bioavailable Cu, Cd and Pb. However, some indexes of soil and plant only relative to one or two soil bioavailable HMs. For example, soil microbial biomass carbon correspondent with soil bioavailable Cd. Only the content of Cu in the stem and leaf showed a notable relationship with soil effective Cu. Soil effect Cu and Pb rather Cd showed remarkable relation with mean transpiration rate, total biomass and leaf area index of sweet potato. The daily mean value in the seedling stage showed a stronger relationship with soil bioavailable Cu and Pb. Therefore these two physiological indexes can reflect the change of soil metallic contamination.

Biodegradation, Environmental↗
PubMed2005

[Effects of earthworm activity on phosphorus fraction and available phosphorus content in red soil].

By the methods of incubation test and Hedley's phosphorus fractionation, this paper studied the effects of inoculating earthworm (Pheretinma pingi) on the phosphorus fractions and available phosphorus contents in red soil. The results showed that during a 100-day incubation, earthworm inoculation combined with organic materials (rice straw RS, peanut residue PR, and rape residue RR) amendment increased significantly the content of soil available phosphorus. Statistics analysis showed that there was a significant difference in soil available phosphorus content between treatments PR or RR with and without earthworm inoculation. Compared with the contents of anion-exchange resin P(trace), NaCO3-soluble P(14.5 mg x kg(-1)) and microbial P(1.0 mg x kg(-1)) in CK, those in treatments of earthworm inoculation plus organic materials amendment increased to 10.5 - 17.8 mg kg(-1), 23.5-35.6 mg x kg(-1), and 6.8 - 9.7 mg x kg(-1), respectively, organic phosphorus content enhanced from 37.9 mg x kg(-1) to 50.7-59.3 mg x kg(-1), whereas residual P was reduced. Earthworm performed an activated effect on the availability of phosphorus in red soil.

Animals↗
PubMed2000

Effect of applying chemical fertilizers on forms of lead and cadmium in red soil.

A three-month incubation study was undertaken to examine the influence of N, P and K on the various forms (soluble plus exchangeable (SE), weakly specifically adsorbed (WSA), Fe-Mn oxides bound (OX), organic matter complexed (OM) and residual fractions (RES)) of lead (Pb) and cadmium (Cd) in a red soil. Application of urea at the rate of 200 mg N/kg significantly lowered the SE fraction, but raised the WSA or OX fraction of both metals. Supply of 80 mg P/kg caused a decrease in the SE fraction of the two metals. The WSA fraction of Pb was reduced, whereas that of Cd increased by adding P. However, addition of 100 mg K/kg led to an increase in the SE fraction, but a decrease in the WSA fraction of Pb and Cd. Applying chemical fertilizers had no significant consistent influences on the other fractions of metals. These findings suggest that in heavy metal contaminated red soil, applying fertilizers does not only provide plant nutrients, but may also change the speciations and thus biovailability of heavy metals.

Agriculture↗
PubMedDate not supplied

Lead adsorption onto "red soils" as function of environmental conditions.

The adsorption characteristics of the "Red Soil" with respect to lead were studied as function of different experimental conditions. Lead adsorption was investigated as function of the complexing capacity of the liquid phase (background electrolyte NaClO4, NaCl, CH3COONa e EDTA), pH (experimental range 4-7) and ionic strength (experimental range 0.001-0.35 M), by determining the adsorption isotherms at the different conditions. Experimental results allowed to identify the presence of different sorption sites, acting on lead removal through different mechanisms (ion exchange and surface complexation). These sorption sites are differently affected by changing the experimental conditions. Adsorption representation in terms of free metal was not able to describe the experimental behaviour, especially when different charged species can be formed and might be sorbed at the surface with different affinities. Particular attention was given to the optimisation of the experimental system based on the flow-through reactor set-up, in order to carry out adsorption tests more representative of the field situation.

Adsorption↗
PubMed2005

[Degradation regulation of fenthion and chlorfenvinfos combined pollutants in red soil].

The degrading regulations of combined pollutants of chlorfenvinfos and fenthion in red soil were studied, in which soil incubation, gas chromatography with nitrogen-phosphorus detection for analysis are utilized. The main conclusions drawn are as follows: under combined pollution condition, the degrading amount of fenthion was significantly higher than that of fenthion alone in soil; under saturated soil humidity, the degrading amount of fenthion was less changed, while that of chlorfenvinfos was increased by 33.3% - 1250%. Soil drought made degradation amount of fenthion decreased a little, while made chlorfenvinfos increased significantly prior to the 21st day after addition of pesticide; nitrogen fertilizer application stimulated both fenthion and chlorfenvinfos degraded; the chemical degrading amount of fenthion in soil with organic matter eliminated was decreased by 22.4% - 30.8%, while that of chlorfenvinfos was increased 42.1% - 2370% at the earlier stage, and was decreased 11% - 17.3% at the later stage. Therefore, there are differences of degrading regulation between single pesticide pollutant and combined pesticide pollutants in soil, and the degradation of organophosphorus pesticides in combined pollutants are influenced with each other.

Biodegradation, Environmental↗
PubMed2003

[Properties of potassium loss from red soil slope land in different farming systems].

The properties of potassium loss in red soil slope field under six cultivations were studied. The results showed that potassium lost mainly with bed load and runoff on surface of soil. The potassium lost mostly with runoff in slope field under contour, contour dam cultivated ways with less sediment except the fallow, under which the loss of potassium with bed load equaled to the loss of potassium with runoff. The potassium lost mostly with bed load in slope field under straight, grass strip and contour ditch cultivated ways with more sediment, and particulate potassium was the main form of potassium lost in runoff. Compared with straight cultivated way, other cultivated ways reduced soil potassium loss significantly. Contour, fallow, and contour dam cultivated ways were better than straight and grass stripe cultivated ways on controlling potassium loss. In the year of 2000, the potassium loss was mainly occurred during May to August accounting for 87.24-100% of total annual lost.

Agriculture↗
PubMed2005

Pilot-scale electrokinetic treatment of a Cu contaminated red soil.

A pilot-scale experiment for electrokinetic treatment of 700 kg of copper contaminated red soil was conducted using a constant voltage of 80 V. Dynamic removal percentages of Cu from the soil and energy consumption during the treatment were evaluated together with changes of soil pH, electrical conductivity and soil microbial functional diversity before and after the electrokinetic treatment. The results indicate that 76% of Cu was successfully removed from the soil after 140 d of treatment when lactic acid was used as enhancing reagent for adjusting the catholyte pH and dissolving soil Cu by complexation, and the pilot-scale electrokinetic experiment consumed electric energy of 224 kW h t-1 soil. The post-treatment soil pH values decreased about 0.1-1.6 units compared with the initial value (pH 4.8), and soil electrical conductivities in most of soil sections also significantly decreased. Soil microbial functional diversity varied after the electrokinetic treatment, particularly the increase of substrate richness index, which is possibly due to the stimulation of lactic acid that was introduced into the soil column during the experiment.

Copper↗
PubMed2006

Effect of heavy metals on substrate utilization pattern, biomass, and activity of microbial communities in a reclaimed mining wasteland of red soil area.

The microbial biomass, basal respiration, and substrate utilization pattern in a copper mining wasteland of red soil area, southern China, were investigated, and indicated that soil microflora were obviously affected by heavy metals. Microbial biomass and basal respiration were negatively affected by comparatively high heavy metal levels. Two important microbial ecophysiological parameters, namely, the microbial biomass C (C(mic))/microbial biomass N (N(mic)) ratio and the metabolic quotient (qCO(2)) were significantly correlated to heavy metal stress. There was a significant decrease in the C(mic)/N(mic) ratio and an increase in the metabolic quotient with increasing metal concentration. Multivariate analysis of Biolog data for sole carbon source utilization pattern demonstrated that heavy metal pollution had a significant impact on microbial community structure and functional diversity. All the results showed that soil microbiological parameters could have great potential as sensitive, effective, and liable indicators of the stresses or perturbations in soils of mining ecosystems.

Biodegradation, Environmental↗
PubMed2005

[Fine-root character and its action mechanism of forest at its initial reestablished stage on degraded red soil].

This paper studied the fine-root character and its action mechanism of forest reestablished by different models for 10 years on a seriously degraded red soil, and analyzed their correlation with soil property. The results showed that fine-roots mostly distributed in 0-20 cm soil layer, accounted for 73.39% -87.41% of those in 0-40 cm soil layer. There were notable differences in nutrient storage of fine-roots under different reestablishment models. The fine- roots of medium density pure Pinus serotina forest had a much higher storage of total nitrogen, phosphorus and potassium, with the content of total nitrogen, phosphorus, potassium, calcium and magnesium being 84.47, 5.55, 38.42, 17.00 and 10.76 kg hm(-2), respectively. Soil organic matter, total nitrogen, available nitrogen, available potassium and pH had significant correlations with fine-root biomass (P < 0.05). The effects of fine-roots on soil physical properties mainly reflected on soil capillary porosity and total porosity. Fine-roots obviously increased the contents of > 0.25 mm and > 5 mm soil waterstable aggregates, and improved soil structure-stability. The correlations between fine-roots and soil bacteria and microbial quantities were significant.

Carbon↗
PubMed2000

[Boron balance in agroecosystem on brown-red soil of south Hubei Province].

Five sequential cropping systems including rape/soybean-rice, wheat/watermelon-rice, rape/corn-soybean, wheat-sesame and soybean-sesame, were selected study the boron balance in agroecosystem on brown-red soil of south Hubei Province. The results show that the main output of boron was runoff and leaching, which accounted for 48-53% and 41% of the total respectively, while the output by products accounted for 3.4-10.1%. The main inputs were from rainfall, irrigation, fertilization seeds and seedlings, and natural return.

Boron↗
PubMed2003

[Change of superficial shape and cell microstructure of milk-vetch (Astragalus L.) root under simulated Cu pollution in a red soil].

This study carried out experiments to investigate changes of shape, inter-structures and cell microstructures of milk-vetch root under simulated Cu stress at non- or contaminated levels in a red soil using observation and bio-microscopic technique. It resulted that when Cu concentration ranged from 0 to 40 mg.kg-1 soil, the milk-vetch grew well and it had a whole root which worked normally. When Cu concentration reached 50 mg.kg-1 soil, the growth of milk-vetch began to get influence with decline of biomass, the taproot crooked and was less branched, root became short and hazel and had fewer shorter hairs, tubby appeared, epidermis began to shrink and cell wall cockled slightly and unevenly, the boundary between plasmalemma and organelle blurred as well. When treatment concentration reaching to 200 mg.kg-1 soil, milk-vetch roots became rotted and black, the cell wall broke and cytoplasm shrank so severely that plasmolysis happened and the plant died. So the critical Cu concentration in experimented soil was 50 mg.kg-1 soil, and the resistance of milk-vetch root to Cu contamination buildup with the growth of aboveground part, and cell wall was the main part to Cu tolerance.

Astragalus Plant↗