施用磷石膏对碱化土壤氟含量及其吸附特性的影响

通过室内培养试验和田间试验就施用磷石膏对土壤氟含量和土壤对氟吸附特性的影响进行了研究．结果表明，经连续４年施用磷石膏改良土壤后，０—２０ｃｍ土层全氟积累现象明显．但是，土壤水溶性氟含量却随磷石膏施用量增加而降低．土壤对氟的吸附数据均能与Ｌａｎｇｍｕｉｒ，Ｆｒｅｕｎｄｉｌｉｃｈ和Ｔｅｍｋｉｎ方程很好地拟合，施用磷石膏处理土壤对氟的最大吸附量高于没有施用磷石膏处理的．影响土壤水溶性氟含量和吸附特性的主要因素可能是土壤钙含量的增加和ｐＨ值的降低．     

铬污染土壤的导电性、频谱激电性和介电特性的实验结果

研究了铬污染土壤的导电性、激电性和介电性,给出了在不同含水率、不同浓度铬盐污染物的情况下,铬污染土壤样品的电阻率、复电阻率和复介电常数与污染物浓度及含水率变化关系的一些实验观测结果.土样中的观测结果表明,所有污染样品的电阻率、复电阻率幅值均随污染浓度和含水率的增加而减小;但对反映土壤样品容性的复电阻率相位参数而言,则有...     

水分管理对水稻生长与根际激发效应的影响特征

作物根际沉积碳输入而引起的根际激发效应,对农田土壤碳排放通量和碳平衡起到关键的调控作用.在稻田生态系统中,由于频繁的干湿交替,土壤CO2 和CH4 排放以及根际激发效应明显有别于其他自然生态系统.因此,明确稻田生态系统干湿交替过程中水稻根际激发效应的方向与强度,对于减缓稻田温室气体排放具有重要意义.本研究采用13C-C...     

Chemistry of atmospheric dust and critical load assessment in Delhi region (India)

This is the first study in the Delhi region that assesses the critical load capacity of soil systems with respect to the atmospheric deposition and air quality, from July to October in 2012. Trend analysis of NO₂ and SO₂ in Delhi, using the Central Pollution Control Board (CPCB) data, showed interesting patterns matching with the trends in vehicular load in the city. This was followed by the calculation of the critical load of atmospheric acidity for sulphur and nitrogen in order to check the vulnerability of the soil systems in Delhi. Here, the steady state mass balance approach was majorly applied and the study conducted in the Agra region was taken as reference. The calculated values of critical loads of sulphur (225–275?eq/ha/yr) and nitrogen (298–303?eq/ha/yr), for the soil system in Delhi, were calculated with respect to three plant species, namely Anjan grass, Hibiscus and Black siris. The present loads of sulphur (PL(S)?=?26.40?eq/ha/yr) and nitrogen (PL(N)?=?36.51?eq/ha/yr) were found to be much lower than their respective critical loads. From the results, it can be concluded that the present loads of atmospheric acidic deposition in Delhi region do not pose any danger of acidification of soil system because it is countered by buffering capacity of soil generated dust. However, considering the pace at which the city is growing, it is likely that in coming decades, the present load will increase and thus the values evaluated in this study are likely to serve as an important reference for future assessment of the pollution scenario in the city.     

Spatial variability in soil water and salinity in Tamarix community in a semiarid saline region of the upper Yellow River北大核心CSCD

Tamarix is widely distributed in semiarid saline regions of the upper Yellow River. The community of Tamarix affects the spatial distribution of soil water and salinity. It is important to explore the dynamic response relationship of Tamarix community and spatial distribution of soil water and salinity in order to evaluate the effects of vegetation community construction and ecological restoration in this region. The natural Tamarix community in the secondary saline-alkali land of the Ningxia Yellow River Irrigation Area was investigated in July 2016. Classical statistics and geostatistics were used to analyze the spatial distribution characteristics of soil water and salinity. The results showed that the soil water content was relatively low (1.98%-7.55%), whereas the soil salinity was high (average conductivity 10.28-25.38 mS/cm) in the study area. The variability coefficient range of soil water and salinity was 36.1%-83.7%, both with moderate variations. Furthermore, the variation degree of soil salinity decreased with the increase in soil depth. The soil water and salinity had obvious spatial structure characteristics, which was mainly affected by structural factors or structural factors associated with stochastic factors. The coefficients of nugget were 0.04%-49.88%, indicating the strong spatial correlation. The spatial distribution of soil water and salinity in Tamarix community showed a patchy pattern; the soil water and salinity distribution in the areas with high Tamarix growing density were considerably high. The correlation analysis showed that there was a positive correlation between soil water and salinity in the study area. In conclusion, soil water and salinity restrict the distribution and growth of Tamarix. Furthermore, the distribution and growth of Tamarix enhanced the spatial variability of soil water and salinity. Keywords. © 2018 Science Press. All rights reserved.     

Dioxins,chlorophenols and other chlorinated organic pollutants in colloidal and water fractions of groundwater from a contaminated sawmill site

BACKGROUND, AIM, AND SCOPE: The distribution of chlorinated organic contaminants in groundwater and the importance of colloids were studied in groundwater from a sawmill site contaminated by chlorophenol preservatives. MATERIALS AND METHODS: The groundwater was fractionated into three different size ranges: (1) >0.7 mum, (2) 0.4-0.7 mum and (3) 0.2-0.4 mum and the filtered water phase. The concentrations of chlorophenols (CP), chlorinated phenoxy phenols (PCPP), chlorinated diphenyl ethers (PCDE), chlorinated dibenzofurans (PCDF) and chlorinated dibenzo-p-dioxins (PCDD) were determined in each fraction. The colloids were characterised regarding the chemical composition using X-ray photoelectron spectroscopy (XPS). RESULTS: Chlorophenols were mostly found in the water fraction and PCDD/Fs were found almost exclusively in the particulate fractions. For example, the filtered water phase contained 2,100 mug l(-1) and 0.72 ng l(-1) for CPs and PCDD/Fs, respectively, and the particulate fractions contained 27 mug l(-1) and 32 ng l(-1) for CPs and PCDD/Fs, respectively. XPS evaluation of the particulate phases showed no correlation between the surface chemistry of the particle properties and the distribution of chlorinated compounds. DISCUSSION: The results suggest that groundwater transport of CPs, PCPPs, PCDEs and PCDD/Fs may occur from contaminated sawmill sites and that the colloid-facilitated transport, especially of PCDD/Fs, is substantial. The results correlated well with previous studies of compounds sorbed to dissolved organic carbon, which indicate that dissolved and colloidal organic carbon facilitated the transport of PCDEs, PCDFs and PCDDs particularly. CONCLUSIONS: Several classes of chlorinated compounds were readily detected in the groundwater samples. Due to the differences in their physicochemical properties, CPs, PCPPs, PCDEs and PCDD/Fs vary in their partitioning between colloidal fractions and the filtered groundwater. The proportion of the bound fraction increased with an increasing hydrophobicity of the chlorinated compounds. The groundwater transport of colloid-associated pollutants from the site may be significant. RECOMMENDATIONS AND PERSPECTIVES: The results imply that colloidal particles <0.7 mum are freely mobile in groundwater from this site. The groundwater transport of colloid-associated pollutants may be significant. However, the extent of the problem is not yet known and, thus, further research is needed to evaluate the impact of colloidal transport of hydrophobic organic contaminants. In Sweden alone, 400 to 500 sawmill sites are estimated to be contaminated with PCDD/Fs as a result of the former use of CP-based wood preservatives. The widespread use of CP mixtures for a variety of applications, including wood preservation, indicates that potential colloidal transport will be an issue of concern in many countries.     

Assessment of the phytoextraction potential of high biomass crop plants

A hydroponic screening method was used to identify high biomass crop plants with the ability to accumulate metals. Highest values of shoot accumulation were found in maize cv. Ranchero, rapeseed cv. Karat, and cardoon cv. Peralta for Pb (18 753 mg kg(-1)), Zn (10 916 mg kg(-1)), and Cd (242 mg kg(-1)), respectively. Subsequently, we tested the potential of these three cultivars for the phytoextraction of a metal spiked compost, finding out that, in cardoon and maize plants, increasing Zn and Cd concentrations led to lower values of root and shoot DW. By contrast, rapeseed shoot growth was not significantly affected by Cd concentration. Finally, a metal polluted soil was used to check these cultivars' phytoextraction capacity. Although the soil was phytotoxic enough to prevent the growth of cardoon and rapeseed plants, maize plants phytoextracted 3.7 mg Zn pot(-1). We concluded that the phytoextraction performance of cultivars varies depending on the screening method used.     

Effects of three pesticides on the avoidance behavior of earthworms in laboratory tests performed under temperate and tropical conditions

Little research has been performed on the impact of pesticides on earthworms under tropical conditions. Taking into consideration the often-limited resources in tropical countries, simple screening tests are needed. Therefore, it was investigated whether three pesticides relevant for the Brazilian Amazon (benomyl, carbendazim, lambda-cyhalothrin) affect the avoidance behavior of the earthworm Eisenia fetida. The tests were performed for two days according to ISO guideline 17512 but were adapted to tropical conditions (i.e. test substrate, test organism and temperature). The results indicate that this test gives reproducible and reliable results. Toxicity values (NOEC, EC50) are lower than those determined in 14 day-acute mortality tests and are approximately in the same range such as those found in 56 day-chronic reproduction tests with the same earthworm species, which were performed in parallel. Therefore, the use of the earthworm avoidance tests is recommended as a screening tool for the risk assessment of pesticides.     

Potentially toxic metal contamination of urban soils and roadside dust in Shanghai, China

A detailed investigation was conducted to understand the contamination characteristics of a selected set of potentially toxic metals in Shanghai. The amount of Pb, Zn, Cu, Cr, Cd and Ni were determined from 273 soil/dust samples collected within urban area. The results indicated that concentration of all metals except Ni in soils was significant, and metal pollution was even severer in roadside dust. A series of metal spatial distribution maps were created through geostatistical analysis, and the pollution hotspots tended to associate with city core area, major road junctions, and the regions close to industrial zones. In attempt of identifying the source of metals through geostatistical and multivariate statistical analyses, it was concluded as follows: Pb, Zn and Cu mainly originated from traffic contaminants; soil Ni was associated with natural concentration; Cd largely came from point-sourced industrial pollution; and Cr, Ni in dust were mainly related to atmospheric deposition.     

Removal of Eu3+, Ce3+, Sr2+, and Cs+ ions from radioactive waste solutions by modified activated carbon prepared from coconut shells

As a biomass agricultural waste material, coconut shells were used for the preparation of high-quality modified activated carbon. Chemical modification of the surface of the prepared activated carbon is done by oxidation using H₂O₂ and HNO₃, respectively. The surface area and pore volume of the coconut shells activated carbon are increased by the chemical modification, and followingly the removal of the metals is improved. The structural morphology and composition of the modified activated carbon coconut shells (MACCS) were evaluated by Fourier transform infrared (FTIR) spectra, thermogravimetric analysis–differential thermal analysis (TGA-DTA), scanning electron microscope (SEM), X-ray diffraction (XRD), surface area analysis (SAA), X-ray fluorescence (XRF), and carbon, hydrogen, nitrogen, and sulfur (CHNS) elemental analysis. The prepared MACCS has reasonably good chemical stability. The influence of solution pH, contact time, adsorbent dosage, adsorption temperature, initial metal concentrations, and interfering ions on the adsorption performance of the investigated ions onto the prepared sorbent was examined by a batch method. The selectivity sequence for sorption of Eu³⁺, Ce³⁺, Sr²⁺, and Cs⁺ ions on MACCS was found to be Eu^3+?>?Ce^3+?>?Sr^2+?>?Cs⁺. The saturation capacities of MACCS for the studied metal ions were found to be 136.84, 85.55, 69.85, and 60.00?mg?g^?1 for Eu³⁺, Ce³⁺, Sr²⁺, and Cs⁺ ions, respectively. The thermodynamic parameters, ΔH°, ΔS°, and ΔG° were also evaluated.