In the humid Caribbean region characterized by high-intensity tropical rainfall, soil aggregate breakdown and pore blocking due to slaking pressures are major land degradation mechanisms. In this research, we investigated the susceptibility of soils to slaking pressures under rapid wetting as influenced by soil properties and the depositional origin from which the soil is formed using water-stable aggregates (WSAr) and percolation stability (PSc) as indices of the strength of aggregate inter-particle cohesion.
Materials and methodsWet sieving and percolation stability analyses were employed to investigate WSAr and pore blocking, respectively. The combined effect of soil properties of clay, organic matter (OM), cation exchange capacity (CEC), and exchangeable sodium percentage (ESP) was used to determine the slaking sensitivity score (SSc) of 14 physiogeographically important soils in Trinidad, comprising of nine alluvial and five residual soils.
Results and discussionResults showed that irrespective of alluvial or residual depositional nature of the parent material, samples had high SSc with an average WSAr of 37.8% and PSc of 6.0 mm/10 min. The linear relationships between SSc with WSAr (r2?=???0.12) and SSc with PSc (r2?=???0.012) of all the 14 soils although negative were weak. Clay content accounted for 94.0% of the variation in CEC in alluvial soils and had strong negative relationships with WSAr (r2?=???0.74) and PSc (r2?=???0.79) in residual soils. Additionally, OM with WSAr (r2?=?0.52) and PSc (r2?=?0.24), and CEC with WSAr (r2?=?0.46) and PSc (r2?=?0.39) showed significant positive linear relationships in residual soil.
ConclusionsThe predominantly micaceous and kaolinitic clay mineralogy of these soils, coupled with the low OM contents, increases the proneness of the soils to slaking. This suggests that clay mineralogy is responsible for the high slaking sensitivity rather than clay content or just the depositional origin of the soils. As CEC increases, an accompanying increase in OM is required to increase inter-particle cohesion and to impart partial hydrophobicity, which in turn decreases mineralogically induced susceptibility of individual aggregates to slaking.
相似文献Chelate-assisted phytoremediation with biodegradable chelates has been considered to be a promising technique to enhance phytoremediation efficiency, while little information is available on phytostabilization. This study aims to assess NTA-assisted phytostabilization of Pb-contaminated soils by Athyrium wardii (Hook.).
Materials and methodsA pot experiment was carried out to investigate the effects of different application days (1, 3, 5, 7, 10, 14, 21) of nitrilotriacetic acid (NTA) on plant growth, Pb accumulation, and Pb availability in rhizosphere soils of A. wardii grown in soils contaminated with low (200 mg kg?1) and high (800 mg kg?1) concentrations of Pb.
Results and discussionWith the application of NTA, better growth for A. wardii was observed when treated with NTA for 5–14 days for both low and high Pb soils, suggesting potential harvest time. Pb concentrations and Pb accumulation in underground parts of A. wardii grown in low and high Pb soils increased with increasing application time of NTA generally. Similar changes were also found for bioaccumulation coefficients (BCFs) of A. wardii. The greatest remediation factors (RFs) for underground parts and whole plant of A. wardii were observed for NTA application time of 7 and 5 days for low and high Pb soils, suggesting the greatest remediation efficiency. Furthermore, plant growth, BCF, and RF of A. wardii grown in low Pb-contaminated soils were greater than those grown in high Pb-contaminated soils. Pb availability in rhizosphere soils of A. wardii grown in low Pb soils was lower than those in high Pb-contaminated soils.
ConclusionsIt seems to be the optimum for A. wardii to phytostabilize slightly Pb-contaminated soils with the application of NTA for 7 days as taking plant growth, Pb remediation efficiency, and environmental risk into consideration.
相似文献Forests play a critical role in terrestrial ecosystem carbon cycling and the mitigation of global climate change. Intensive forest management and global climate change have had negative impacts on the quality of forest soils via soil acidification, reduction of soil organic carbon content, deterioration of soil biological properties, and reduction of soil biodiversity. The role of biochar in improving soil properties and the mitigation of greenhouse gas (GHG) emissions has been extensively documented in agricultural soils, while the effect of biochar application on forest soils remains poorly understood. Here, we review and summarize the available literature on the effects of biochar on soil properties and GHG emissions in forest soils.
Materials and methodsThis review focuses on (1) the effect of biochar application on soil physical, chemical, and microbial properties in forest ecosystems; (2) the effect of biochar application on soil GHG emissions in forest ecosystems; and (3) knowledge gaps concerning the effect of biochar application on biogeochemical and ecological processes in forest soils.
Results and discussionBiochar application to forests generally increases soil porosity, soil moisture retention, and aggregate stability while reducing soil bulk density. In addition, it typically enhances soil chemical properties including pH, organic carbon stock, cation exchange capacity, and the concentration of available phosphorous and potassium. Further, biochar application alters microbial community structure in forest soils, while the increase of soil microbial biomass is only a short-term effect of biochar application. Biochar effects on GHG emissions have been shown to be variable as reflected in significantly decreasing soil N2O emissions, increasing soil CH4 uptake, and complex (negative, positive, or negligible) changes of soil CO2 emissions. Moreover, all of the aforementioned effects are biochar-, soil-, and plant-specific.
ConclusionsThe application of biochars to forest soils generally results in the improvement of soil physical, chemical, and microbial properties while also mitigating soil GHG emissions. Therefore, we propose that the application of biochar in forest soils has considerable advantages, and this is especially true for plantation soils with low fertility.
相似文献Vanadium (V) contamination in soil can cause diverse damage to soil ecosystem and has attracted research interests in exploring soil V stabilization methods, but only a few materials were proposed and studied. Here, a pot experiment was firstly conducted to estimate the efficiency of nano-hydroxyapatite (n-HAP) in stabilizing V in soil. To verify the impact of n-HAP on soil V bioavailability and phytotoxicity, cabbages (Brassica chinensis L.) were grown in V-spiked soils after n-HAP amendment.
Materials and methodsSoils were sampled from a farmland in China, and the n-HAP was prepared in the laboratory. In each pot of soil spiked with 0, 75, 150, 300, and 600 mg/kg V, 2% n-HAP was amended for 30 days, while soils without n-HAP amendment were set as controls. The stabilization effect of n-HAP on V in soil was estimated by the water-extractable and bioavailable V concentrations in soils. Cabbages were grown in pots subsequently. The V(V/IV) concentrations in cabbage leaves and roots, the organic bound V concentrations in cabbage roots, and the chlorophyll concentrations in leaves were determined. Bioconcentration factor and translocation factor were calculated. The composition of organic bound V in leaf was characterized by fluorescence excitation–emission matrix.
Results and discussionIn soils spiked with 150 mg/kg V, n-HAP amendment yielded the highest stabilization rates of 51.0% and 42.4% for water-extractable and bioavailable V, respectively. In 75, 150, and 300 mg/kg V-spiked soil, the plant weight, plant height, and root length of cabbage after 60-day growing decreased 54.6%/89.6%, 30.9%/45.5%, and 41.5%/51.4% in groups with/without n-HAP, respectively. Cabbage leaf chlorophyll concentrations descend firstly then ascend with rising soil V concentration. Leaf V speciation analysis revealed that less leaf V was reduced to V(IV) in groups amended with n-HAP than groups without n-HAP amendment. In 150 and 300 mg/kg V-spiked soil, n-HAP effectively reduced the V content and the V bioconcentration factor of cabbage root. Tyrosine-like and humic acid-like analogues composed the principal part of V complex.
ConclusionsIn general, n-HAP amendments are potential to decrease the mobility of V in soils, as well as inhibit the bioavailability and phytotoxicity of V to cabbage. In V-spiked soils, n-HAP amendment can alleviate the toxicity of V to the cabbage. Overall, 2% n-HAP is efficient for the amendment of slight V-polluted (150–300 mg/kg) soils to alleviate the soil V stress to cabbage.
相似文献Rhizosphere and fertilization might affect soil microbial activities, biomass, and community. This study aimed to evaluate the impacts of Phyllostachys edulis (moso bamboo) rhizospheres on soil nutrient contents and microbial properties in a moso bamboo forest with different fertilizer applications and to link soil microbial activities with abiotic and biotic factors.
Materials and methodsThe experiment included three treatments: (1) application of 45% slag fertilizer (45%-SF); (2) application of special compound fertilizer for bamboos (SCF); and (3) the control without any fertilizer application (CK). Simultaneously, bulk soils and 0.5, 2.5, 4.5, and 6.5-year-old (y) bamboo rhizosphere soils were selected. Soil nutrient contents were analyzed. Microbial activities were evaluated based on the activities of soil enzymes including β-glucosidase, urease, protease, phosphatase, and catalase. The total microbial biomass and community were assessed with the phospholipid fatty acids (PLFAs) method.
Results and discussionIn the CK and SCF treatments, organic matter contents of rhizosphere soils were significantly higher than those of bulk soils. Soil β-glucosidase, urease, protease, phosphatase, and catalase activities in rhizosphere soils were higher than those of bulk soils, with the sole exception of β-glucosidase of 0.5 y rhizosphere soil in the 45%-SF treatment. Compared with the CK treatment, fertilizer applications tended to increase soil total PLFAs contents and changed soil microbial community. Moso bamboo rhizospheres did not significantly increase the total microbial biomass. In the SCF treatment, the Shannon index of bulk soil was significantly lower than those of rhizosphere soils.
ConclusionsOur results suggested that both rhizospheres and fertilizer applications could change the soil microbial community structures and that moso bamboo rhizosphere could increase microbial activity rather than biomass in the forest soils with different fertilizer applications.
相似文献Information about particle size distribution (PSD) and soil texture is essential for understanding soil drainage, porosity, nutrient availability, and trafficability. The sieve-pipette/gravimetric method traditionally used for particle size analysis is labour-intensive and resource-intensive. X-ray fluorescence (XRF) spectrometry may provide a rapid alternative. The study’s aim was to examine the use of XRF for rapid determination of PSD in Irish soils.
MethodsSoils (n?=?355) from existing archives in Ireland were analysed with a benchtop energy-dispersive XRF (EDXRF). Correlation and regression analyses were determined to compare Rb, Fe, Al, and Si concentrations to % clay, % silt, and % sand. Also, linear regression models were developed to compare % clay, % sand, and % silt measured by the gravimetric method to values predicted by EDXRF.
ResultsThe relationship between element concentration and PSD was dependent on parent material. Rb, Al, and Fe showed a significant (p?<?0.05) correlation (r?>?0.50) with % clay and % sand in soils derived from limestone and siliceous stone parent materials. Rb was the best predictor for % clay (R2?=?0.49, RMSE?=?10.20) in soils derived from limestone and siliceous stone-derived soils.
ConclusionGeochemistry and clay mineralogy of the soils’ parent material strongly influenced the EDXRF’s ability to predict particle size. The EDXRF could predict % clay in soils from parent materials which weather easily, but the opposite was true for soils with parent material recalcitrant to weathering. In conclusion, this study has shown that the EDXRF can screen % clay in soils derived from limestone and siliceous stone parent materials.
相似文献The purpose of this paper is to study the responses of soil biological parameters as indicator of ecological status on PAH-contaminated soil.
Materials and methodsStudies are conducted on the soils and natural grassy vegetation of monitoring plots subjected to Novocherkassk power station (NPS) emissions. Monitoring plots were established at different distances from the NPS (1.0–20.0 km).
Results and discussionThe level of polycyclic aromatic hydrocarbons (PAHs) around NPS is the highest at the monitoring plot located at distance 1.6 km to the northwest through the prevailing wind direction. Gradually, decrease of PAHs was observed while increasing the distance from the NPS through the prevailing wind direction. Calculation of correlations between PAH level and biological activity parameters of soils showed lack of dependence with total and every PAH content in all 12 studied monitoring plots. The most significant correlations were found between PAH content and enzyme activity in the monitoring plots situated through the prevailing wind direction from NPS.
ConclusionsThe main pollution source in the studied area is NPS. It was found that contamination of soil by PAHs has a direct dependence on the activity of all biological communities in chernozems, as well as the activities of dehydrogenase and the phytotoxicity of soils. Inverse correlations have been revealed between the PAH contamination and abundance of soil bacteria.
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