Retention of 137cesium in acid sulphate soils of South Central Thailand

Adsorption and desorption of ¹³⁷Cs by acid sulphate soils from the Nakhon Nayok province, South Central Plain of Thailand located near the Ongkarak Nuclear Research Center (ONRC) were investigated using a batch equilibration technique. The influence of added limestone (12 and 18 tons ha^-1) on ¹³⁷Cs adsorption-desorption was studied. Based on Freundlich isotherms, both adsorption and desorption of ¹³⁷Cs were nonlinear. A large portion (98.26-99.97%) of added ¹³⁷Cs (3.7 × 10³-7.03 × 10⁵ Bq l^-1) was sorbed by the soils with or without added lime. The higher lime treatments, however, favoured stronger adsorption of ¹³⁷Cs as compared with soil with no lime, which was supported by higher K_ads values. The addition of lime, the cation exchange capacity and pH of the soil increased and hence favoured the stronger adsorption of ¹³⁷Cs. Acid sulphate soils with a high clay content, medium to high organic matter, high CEC, and predominant clay types consisting of a mixture of illite, kaolinite, and montmorillonite were the main soil factors contributing to the high ¹³⁷Cs adsorption capacity. Competing cations such as NH₄⁺, K⁺, Na⁺, Ca²⁺, and Mg²⁺ had little influence on ¹³⁷Cs adsorption as compared with liming, where a significant positive correlation between K_ads and soil pH was observed. The ¹³⁷Cs adsorption-desorption characteristics of the acid sulphate soils studied exhibited a very strong irreversible sorption pattern. Only a small portion (0.09-0.58%) of ¹³⁷Cs adsorbed at the highest added initial ¹³⁷Cs concentration was desorbed by four successive soil extractions. Results clearly demonstrated that Nakhon Nayok province acid sulphate soils have a high ¹³⁷Cs adsorption capacity, which limits the ¹³⁷Cs bioavailability.     

Sorption and leaching behavior of hexaconazole as influenced bysoilproperties

Sorption and leaching behavior of hexaconazole in four different soils (alluvial, red, laterite, and black) was studied using a batch equilibration technique. The values of the Freundlich adsorption constant 1/n_ads ranged from 0.75 to 0.85 for all four soils, showing strong non-linear behavior. Upon stepwise desorption with CaCl₂ solution (10 mmol·L^?1), release of hexaconazole was maximum with the first elution, the amount decreasing with each subsequent one. The leaching behavior under saturated flow conditions was also studied with soil columns packed in polythene tubes. The mobility of hexaconazole was maximum in sandy loam and minimum in black soil.     

Adsorption‐desorption hysteresis of α‐endosulfan in tropical soils using isotopic techniques

This study was designed to evaluate the adsorption‐desorption hysteresis of endosulfan (1,2,3,4, 7,7‐hexachlorobicyclo[2,2,1]‐2‐heptene‐5,6‐bisoxymethylene sulfite) in selected tropical soils. Two major tropical soils from Thailand were selected, Rangsit lowland soils (Rangsit series) and Phrabat upland soils (Pakchong series). The soil types were sub‐divided into plow soils, 0–20cm depth from the surface, and subsoils, 20–40cm depth. Adsorption was determined in 24h batch equilibrium, with five different concentrations of ¹⁴C endosulfan ranging from 1.04 to 16.64 ng/mg soils. Four successive desorption studies were performed continuously after three adsorption concentrations, 24h for each successive. Adsorption coefficient values (K _ads) as determined by Freundlich model ranged from 0.02 to 0.14 and found to be higher in Rangsit soils as expected when compared with Phrabat soils. Desorption was hysteresis in every desorption study. Desorption coefficient values (K _des) were higher than adsorption (K _des).     

Cäsium-137 in Böden saarländischer Waldökosysteme

Scopes and main features

In order to explain the behaviour of the artificial radioisotope¹³⁷Cs towards landscape resources in the Saar-Lor-Lux-Region, the cross-border region between southwestern Germany/ Saarland, France/Lorraine and Luxembourg, regional distribution as well as downward translocation and depth functions of¹³⁷Cs in the main soil substrates of forest ecosystems in the Saarland were investigated.

Results

The study shows that the highest¹³⁷Cs activities are found in the north of the Saarland, whereas the south and south-eastern regions show distinctly lower concentrations of¹³⁷Cs. Migration rates range between 0.25 cm/a and 1.0 cm/a. On an average, the highest migration rates were found in the clayey-silty substrates of the lime stone areas in theMuschelkalk regions (Middle Triassic) (0.66 cm/a), followed by the loamy substrates of Lower Permian clastic sediments (Unterrotliegendes) (0.53 cm/a) and the sandy substrates of theBuntsandstein areas (Lower Triassic sandstone) (0.41 cm/a). 90 to 95% of the¹³⁷Cs activities in the clay-poor soils of the Unterrotliegendes and the Buntsandstein were traced in the upper 10 cm of the humus topsoil. The substrates of the lime stone areas (Muschelkalk), in contrast to this, reveal a¹³⁷Cs activity of only 70–76% at the same depth.

Conclusions

Due to the fact that the primary and secondary pores of the soil pore system, in their function as translocation pathways, decrease with increasing soil depth, a significant reduction in the migration rates of¹³⁷Cs can be expected with increasing soil depth. On the other hand, the maximal migration depth of 40 cm found in shallow soils on jointed parent material, as well as on sites with high groundwater tables, implies a possible contamination of near-surface groundwater.

Future outlook

Based on the results of this study, a permanent monitoring of¹³⁷Cs was added to the long-term Soil Monitoring Program run by the Federal Administrative Office of Environment of the Saarland (Landesamt für Umweltschutz des Saarlandes)     

High immobilization of soil cesium using ball milling with nano-metallic Ca/CaO/NaH2PO4: implications for the remediation of radioactive soils

This report shows that cesium can be immobilized in soils with an efficiency of 96.4% by ball milling with nano-metallic Ca/PO₄. In Japan, the major concern on ¹³⁷Cs deposition and soil contamination due to the emission from the Fukushima Daiichi nuclear power plant showed up after a massive quake on March 11, 2011. The accident rated 7, the highest possible on the international nuclear event scale, released 160 petabecquerels (PBq) of iodine ¹³¹I and 15 PBq of ¹³⁷Cs according to the Japanese Nuclear and Industrial Safety Agency. Both ¹³⁷Cs and ¹³¹I radioactive nuclides are increasing cancer risk. Nonetheless, ¹³⁷Cs, with a half-life of about 30 years compared with 8 days for ¹³¹I, is a major threat for agriculture and stock farming and, in turn, human life for decades. Therefore, in Japan, the ¹³⁷Cs fixation and immobilization in contaminated soil is the most important problem, which should be solved by suitable technologies. Ball milling treatment is a promising treatment for the remediation of cesium-contaminated soil in dry conditions. Here, we studied the effect, factors and mechanisms of soil Cs immobilization by ball milling with the addition of nano-metallic Ca/CaO/NaH₂PO₄, termed “nano-metallic Ca/PO₄.” We used scanning electron microscopy combined with electron dispersive spectroscopy (SEM/EDS) and X-ray diffraction. Results show that immobilization efficiency increases from 56.4% in the absence of treatment to 89.9, 91.5, and 97.7 when the soil is ball-milled for 30, 60 and 120 min, respectively. The addition of nano-metallic Ca/PO₄ increased the immobilization efficiency to about 96.4% and decreased the ball milling time. SEM/EDS analysis allows us to observe that the amount of Cs decreased on soil particle surface. Use of nano-metallic Ca/PO₄ over a short milling time also decreases Cs leaching. Therefore, ball milling with nano-metallic Ca/PO₄ treatment may be potentially applicable for the remediation of radioactive Cs-contaminated soil in dry conditions.     

Geochemical Associations of Sellafield-Derived Radionuclides in Saltmarsh Deposits of the Solway Firth

This paper describes a study of the geochemical associations of Sellafield waste radionuclides in saltmarsh sediments from south-west s]Scotland. The contaminant radionuclides are transported to this environment in association with particulate material and ¹³⁷Cs was found to be predominantly (80-98%) non-extractable. In the case of ^239+240Pu there was a redistribution from the oxalate extractable oxide fraction to the pyrophosphate extractable organic fraction as a consequence of on-shore transfer of contaminated sediment. The relatively aggressive nature of the chemical extractants required to remove the radionuclides from the sediments suggests that they were in a form which was unlikely to result in their being released into the aquatic environment or taken up by plants. Plutonium had a greater potential mobility or bioavailability than Cs. Values of K^D for the desorption of ¹³⁷Cs from the sediment by freshwater, groundwater and seawater were all approximately 10⁵ L kg^-1, confirming its immobility in this environment. The desorption K_D values for stable ¹³³Cs were all approximately 10⁶ L kg^-1, so the stable Cs did not have a significant influence on the radiocaesium in this sediment.     

Biosolids application affects the competitive sorption and lability of cadmium,copper, nickel,lead, and zinc in fluvial and calcareous soils

The objective of this research was to investigate the effects of biosolids on the competitive sorption and lability of the sorbed Cd, Cu, Ni, Pb, and Zn in fluvial and calcareous soils. Competitive sorption isotherms were developed, and the lability of these metals was estimated by DTPA extraction following their sorption. Sorption of all metals was higher in the fluvial than in the calcareous soil. Sorption of Cu and Pb was stronger than that of Cd, Ni, and Zn in all soils. Biosolids application (2.5%) reduced the sorption of all metals especially Cu and Pb (28–43%) in both soils (especially the calcareous soil) at the lower added metal concentrations (50 and 100 mg L^?1). However, it increased the sorption of all metals especially Pb and Cu in both soils (especially the calcareous soil; 15.5-fold for Cu) at the higher added concentrations (250 and 300 mg L^?1). Nickel showed the highest lability followed by Cd, Zn, and Pb in both soils. Biosolids increased the lability of the sorbed Ni in the fluvial soils at all added concentrations and the lability of Cd, Pb, and Zn at 50 mg L^?1, but decreased the lability of Cd, Pb, and Zn at 250 and 300 mg L^?1 in both soils. We conclude that at low loading rate (e.g., 50 mg L^?1) biosolids treatment might increase the lability and environmental risk of Cd, Cu, Pb, and Zn. However, at high loading rate (e.g., 300 mg L^?1) biosolids may be used as an immobilizing agent for Cd, Cu, Pb, Zn and mobilizing agent for Ni.     

Adsorption and movement of carbaryl in soils: A verification of cosolvent theory and comparison of batch equilibrium and soil thin layer chromatography results

Batch equilibrium and soil thin layer chromatography (TLC) techniques were used to investigate the influence of different volume fractions of organic cosolvents (acetone and methanol) on the adsorption and movement of carbaryl in four different types of Indian soils. L-shaped isotherms were obtained for both the cosolvent–water mixtures at all f _s values and were in close agreement with the Freundlich equation. Higher adsorption was observed on F.R.I. soil (FSL) followed by Alampur soil (ASL), Kalai soil (KL), and Bhoran soil (BSL) at all f _s values for both the cosolvent systems as was anticipated from the K and K _D values. The K and K _D values also confirmed that carbaryl adsorption was higher in methanol–water mixture than acetone–water mixture and decreased with increasing f _s values. The frontal R _f values obtained from soil TLC studies were inversely proportional to the K and K _D values for both the cosolvent systems. The higher K and K _D values and lower R _f values in methanol–water mixtures relative to acetone–water mixtures for all the soils indicated that acetone had a greater potential for ground water contamination compared to methanol. The adsorption data were used to evaluate the cosolvent theory for describing adsorption of carbaryl in acetone–water and methanol–water mixtures. The aqueous phase partition coefficients, K _DW (mol g^?1), normalized with respect to f _oc for carbaryl was evaluated by extrapolating f _s → 0.     

Phenanthrene adsorption by soils treated with humic substances under different pH and temperature conditions

The mobility of phenanthrene (PHE) in soils depends on its sorption and is influenced by either the existing soil humus or exogenous humic substances. Exogenous humic acids (HAs) were added to soil to enhance the amount of soil organic carbon (SOC) by 2.5, 5.0, and 10.0 g kg⁻¹. PHE desorption of the treated soils was determined at two pH levels (3.0 and 6.0) and temperatures (15 and 25 °C). Soil PHE adsorption was related to pH and the type and quantity of added HAs. Humic acid (HA) and fulvic acid (FA) derived from peat had different effects on adsorption of PHE. Adsorption increased at first and then decreased with increasing quantity of exogenous FA. When the soil solution pH (in 0.005 M CaCl₂) was 4.5 or 3.0, the turning points were 2.5 g FA kg⁻¹ at pH 3.0 and 5 g FA kg⁻¹ at pH 4.5. When soil solution pH was 6, the amount of adsorbed PHE was enhanced with increasing exogenous HAs (HA or FA) and amount of adsorption by soil treated with FA was higher than with HA. Adsorption of PHE in the FA treatment at 10.0 g kg⁻¹ was lower than the controls (untreated soil or treatment with HAs at 0 g kg⁻¹) when the soil solution pH was 3.0. This suggests that FA adsorbed by soil was desorbed at low pH and would then increase PHE solubility, and PHE then combined with FA. PHE adsorption was usually higher under lower pH and/or lower temperature conditions. PHE sorption fitted the Freundlich isotherm, indicating that exogenous humic substances influenced adsorption of phenanthrene, which in turn was affected by environmental conditions such as pH and temperature. Thus, exogenous humic substances can be used to control the mobility of soil PAHs under appropriate conditions to decrease PAH contamination.     

Natural and synthesised iron-rich amendments for As and Pb immobilisation in agricultural soil

The immobilisation of heavy metals in contaminated soils is a promising alternative to conventional remediation techniques. Very few studies have focused on the use of iron-rich nanomaterials and natural materials for the adsorption of toxic metals in soils. Synthesised iron-rich nanomaterials (Fe and Zr–Fe oxides) and natural iron-rich materials (natural red earth; NRE) were used to immobilise As and Pb in contaminated agricultural soil. Total concentrations of As and Pb in the initial soil (as control) were 170.76 and 1945.11 mg kg^?1, respectively. Amendments were applied into the soil at 1, 2.5 and 5% (w/w) in triplicate and incubated for 150 days. Except for the NRE-amended soil, soil pH decreased from 5.6 to 4.9 with increasing application rates of Fe and Zr–Fe oxides. With addition of Fe and Zr–Fe oxides at 5%, the ammonium acetate (NHO₄Ac)-extractable Pb was greatly decreased by 83 and 65% compared with NRE addition (43%). All subjected amendments also led to a decrease in NHO₄Ac-extractable As in the soils, indicating the high capacity of As immobilisation. Soil amended with NRE showed a lower ratio of cy19:0 to 18:1ω7c, indicating decreased microbial stress. The toxicity characteristic leaching procedure produced results similar to the NHO₄Ac extraction for As and Pb. The NRE addition is recommended for immobilising heavy metals and maintaining biological soil properties.     

A novel extraction method for analysing available sulfamethoxazole in soil

A novel extraction method was established to determine the water-extractable (available) content of sulfamethoxazole (SMX) in soil. The SMX imprinted polymers (MIPs) were synthesised and the performance was evaluated by Fourier transform infrared spectroscopy, scanning electron microscopy and binding experiments. Results showed that the MIPs exhibited good selectivity for SMX, so the MIPs were applied as a sorbent. SMX in soil was extracted by water, sorbed from the extract to MIPs and analysed with a high performance liquid chromatography (HPLC) after its desorption from MIPs. Meanwhile, the classic organic solvent extraction was employed to measure the total SMX content in soil. Results showed that when SMX level in spiked soils varying from 1.0–500?μg?kg^?1, the observed recoveries of available SMX contents ranged from 63.27?±?3.11% to 82.11?±?2.77% (n?=?3), while the total SMX varied between 89.59?±?1.65% and 97.64?±?3.92% (n?=?3). The detection limit of the developed method for SMX in soils was 0.05?μg?kg^?1. Available SMX contents in five field soil samples ranged from 0.13 to 4.14?μg?kg^?1, which were only 0.35–25.40% of the respective total SMX contents. Results from this study manifest the importance of the extents of SMX immobilisation with different soils for assessing SMX's ecological and human health risks.     

Geochemistry and quality of groundwater of the Yarmouk basin aquifer,north Jordan

Quality of groundwater in the Yarmouk basin, Jordan has been assessed through the study of hydrogeochemical characteristics and the water chemistry as it is considered the main source for drinking and agriculture activities in the region. The results of the relationship between Ca²⁺ + Mg²⁺ versus HCO₃^? + CO₃^2?, Ca²⁺ + Mg²⁺ versus total cations, Na⁺ + K⁺ versus total cations, Cl^? + SO₄^2? versus Na⁺ + K⁺, Na⁺ versus Cl^?, Na⁺ versus HCO₃^? + CO₃^2?, Na⁺ versus Ca²⁺, and Na⁺: Cl^? versus EC describe the mineral dissolution mechanism through the strong relationship between water with rocks in alkaline conditions with the release of Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^?, CO₃^2?, SO₄^2?, and F^? ions in the groundwater for enrichment. Furthermore, evaporation processes, groundwater depletion, and ion exchange contribute to the increased concentration of Na⁺ and Cl^? ions in groundwater. Anthropogenic sources are one of the main reasons for contamination of groundwater in the study area and for increasing the concentration of Mg²⁺, Na⁺, Cl^?, SO₄^2?, and NO₃^? ions. Results show the quality of groundwater in the study area is categorized as follows: HCO₃^? + CO₃^2? > Cl^? > SO₄^2? > NO₃^? > F^? and Na⁺ > Ca²⁺ > Mg²⁺ > K⁺. In conclusion, the results of TDS, TH, and chemical composition showed that 26% of the groundwater samples were unsuitable for drinking. About 28% of groundwater samples in the study area have a high concentration of Mg²⁺, Na⁺, and NO₃^? above the acceptable limit. Also, based on high SAR, 10% of the groundwater samples were not suitable for irrigation purposes.     

Sediment accumulation and bio-diffusion mixing rates derived from excess <Superscript>210</Superscript>Pb and <Superscript>137</Superscript>Cs profiles in sediment cores of Mumbai Harbor Bay

Bio-diffusion mixing rates (D_b) were estimated from depth profiles of excess ²¹⁰Pb and ¹³⁷Cs in three sediment cores collected from Mumbai Harbour Bay (MHB) using a steady state vertical advection - diffusion model. The mean of ²¹⁰Pb and ¹³⁷Cs derived D_b values along the studied area were obtained to be about 23 and 36 cm²y^?1 respectively. These derived values were within the range of literature values reported for other equivalent environment internationally. The relatively higher D_b values for ¹³⁷Cs profiles demonstrated that particles have diffused more intensely within the surface layer of sediments over 1 year. Conversely, low D_b values for ²¹⁰Pb indicate slow mixing rates in the sediment profile which might be resulted from low ²¹⁰Pb flux and diffusion of ²²²Rn to the seafloor. The significant differences between ²¹⁰Pb and ¹³⁷Cs derived D_b values among cores indicate that there appeared to be as regional differences in sediment properties and local variability in the intensity of seafloor mixing. Furthermore, D_b values also depend on differences in characteristic time and depth scales of radionuclides in cores, benthic fauna abundances, organic carbon flux to the sediments and primary production in overlying surface waters. Comparison of ²¹⁰Pb derived D_b values with those calculated from ¹³⁷Cs distributions reveals better agreement for core 2 than core 1 and 3. The agreement may be fortuitous because ¹³⁷Cs appears significantly deeper than ²¹⁰Pb in all cores. It was also observed that D_b values increases as sediment accumulation rate increases for both radionuclide.     

Adsorption and desorption of tetraalkyllead and dibutyltin compounds on contaminated soils

Adsorption and desorption of di-n-butyltin (IV) (DBT), tetramethyllead (TML), and tetraethyllead (TEL) on four types of soil were studied. Although, all K _d values for desorption are higher than the K _d values for adsorptions, which shows that the adsorption process is reversible, the lower percentages of desorption indicate that very low concentration of these organometallic compounds can be more easily leached from the soil. The adsorption ranging between 48.8% and 88.3% for DBT, between 9.1% and 38.3% for TEL, and between 24.9% and 44.2% for TML was measured. The desorption was obtained between 9.4% and 23.7% for DBT, between 19.3% and 38.9% for TEL, and between 21.5% and 32.7% for TML. These results show that the nonpolar (TML, TEL) organometallic compounds can be easier leached than the ionic forms (DBT). Adsorption kinetics and adsorption as a function of pH were also evaluated. DBT and tetraalkyllead adsorption equilibrium were reached after 12 and 24 h, respectively. The tetraalkyllead is strongly adsorbed at pH 7–8 and DBT at pH 6.     

Seasonal variation of the concentrations of 137Cs in sediment,sea water,and some organisms collected from Izmir Bay and Didim

¹³⁷Cs in the marine environment mainly originates from fallout of atmospheric nuclear weapon tests, accidental releases from nuclear facilities, and from the Chernobyl accident. After the latter accident, many studies have been carried out in Turkey. The objective of this study is to assess the spatial distribution of ¹³⁷Cs in the coastal marine environment of the Aegean Sea.

The concentrations of ¹³⁷Cs in sediment, sea water, mussel (Mytilus galloprovincialis), and fish samples collected from the coast of the Aegean Sea at Izmir Bay and near Didim (Akbük) have been monitored for seasonal variability by the means of gamma spectroscopy: they vary between 0.10 ± 0.01 and 1.5 ± 0.3 Bq kg^?1, 1.3 ± 0.1 and 4.3 ± 0.4 Bq m^?3, <0.2 and 1.3 ± 0.3 Bq kg^?1, and 0.20 ± 0.03 and 1.8 ± 0.3 Bq kg^?1, respectively.     

Arachis hypogaea derived activated carbon steered remediation of Benzimidazole based fungicide adsorbed soils

Sorption characteristics of the Benzimidazole fungicide Carbendazim were assessed in seven different soils using batch equilibrium method and analysed by UV-Vis spectrophotometer. The values of adsorption co-efficient K_d ranged from 14.3 to 39.8?µg/mL depending upon unique physiochemical properties of soils. Negative values for Gibbs free energy (ΔG) proposed an exothermic and low interaction between Carbendazim and soil samples leading to physiosorption. Statistical analysis showed a negative correlation of soil pH and K_d (R²= ?0.80) and a positive correlation with organic matter (R^2?=?0.77). Activated carbon prepared from Arachis hypogaea (peanut shells) by acid activation for Carbendazim removal from soils was characterised by FTIR spectrometry, indicating the change in functional groups. The highest percentage removal observed was 70% in 5?ppm initial Carbendazim concentration while 65% in 7.5?ppm concentration. This method can be implied in agricultural soils as an efficient and cheap technique for removing the hazardous pesticides from the environment.     

Effect of low molecular weight organic acids on adsorption and desorption of fluoride on variable charge soils

The effect of four low molecular weight organic acids on F⁻ adsorption by two variable charge soils was investigated using a batch method. The organic acids reduced F⁻ adsorption through competition by the acids with F⁻ for sorption sites. Oxalic and malonic acids, both of which have simpler chemical structures, were more effective than citric or malic acid. The effect of organic acids on F⁻ adsorption was more prominent at higher pH values and with larger amounts of the organic acids. The desorption study showed that the organic acids enhanced the desorption of F⁻ adsorbed by the soils. In the control and malic acid systems, desorption increased sharply with decreasing pH, while in the oxalic acid system, desorption rose slightly with decreasing pH. Desorption also increased with increasing amount of organic acid added. There are two possible mechanisms for the effect of the organic acids on F⁻ adsorption and desorption: (1)␣competition of the organic acids with F⁻ for adsorption sites and (2) dissolution of the adsorbents, especially dissolution of soil Al.     

土壤水溶态铜对小白菜的毒害效应及其预测模型

土壤中铜(Cu)重金属的生物毒性/有效性主要取决于它们在土壤液相中含量和土壤溶液的性质。探寻土壤有效态Cu的生物毒害效应,表征量化其与土壤溶液性质关系,可为土壤Cu的环境风险评价提供参考。选取17种典型农田土壤,探讨了有效态Cu(土壤孔隙水以及CaCl_2浸提态)对小白菜生长的毒性效应及其预测模型。结果表明:土壤孔隙水中Cu对小白菜生长10%抑制的毒性阈值值(EC_(10))和50%抑制的毒性阈值(EC_(50)),最大值与最小值相差为14.7和14.6倍;同样,对于CaCl_2提取态Cu的EC_(10)和EC_(50),最大值与最小值相差12.7和7.7倍,表明土壤溶液性质对水溶性Cu对小白菜的毒性阈值影响很大。建立了土壤溶液的重要因子(溶解性有机碳、土壤溶液pH值、电导率、全硫含量、Ca~(2+)、Mg~(2+)、K~+、Na~+)和水溶性Cu阈值之间的多元回归关系,结果显示,土壤溶液性质可以较好地预测水溶性Cu对小白菜的毒性阈值。同时,土壤溶液中Mg~(2+)、K~+和S的含量是控制孔隙水中Cu对小白菜生长毒性的最重要因子,单一的S能分别解释34%的EC_(10)变异,K~+解释26%的EC_(50)变化。本研究结果可为陆地环境中水溶性Cu的风险评价提供基础。     

Environmental impact of CO<Subscript>2</Subscript>, Rn,Hg degassing from the rupture zones produced by Wenchuan <Emphasis Type="Italic">M</Emphasis><Subscript>s</Subscript> 8.0 earthquake in western Sichuan,China

The concentrations and flux of CO₂, ²²²Radon (Rn), and gaseous elemental mercury (Hg) in soil gas were investigated based on the field measurements in June 2010 at ten sites along the seismic rupture zones produced by the May 12, 2008, Wenchuan M _s 8.0 earthquake in order to assess the environmental impact of degassing of CO₂, Rn and Hg. Soil gas concentrations of 344 sampling points were obtained. Seventy measurements of CO₂, Rn and Hg flux by the static accumulation chamber method were performed. The results of risk assessment of CO₂, Rn and Hg concentration in soil gas showed that (1) the concentration of CO₂ in the epicenter of Wenchuan M _s 8.0 earthquake and north end of seismic ruptures had low risk of asphyxia; (2) the concentrations of Rn in the north segment of seismic ruptures had high levels of radon, Maximum was up to level 4, according to Chinese code (GB 50325-2001); (3) the average geoaccumulation index I _geo of soil Hg denoted the lack of soil contamination, and maximum values classified the soil gas as moderately to strongly polluted in the epicenter. The investigation of soil gas CO₂, Rn and Hg degassing rate indicated that (1) the CO₂ in soil gas was characterized by a mean \(\updelta^{13}C_{CO2}\) of ?20.4 ‰ and by a mean CO₂ flux of 88.1 g m^?2 day^?1, which were in the range of the typical values for biologic CO₂ degassing. The maximum of soil CO₂ flux reached values of 399 g m^?2 day^?1 in the epicenter; (2) the soil Rn had higher exhalation in the north segment of seismic ruptures, the maximum reached value of 1976 m Bq m^?2 s^?1; (3) the soil Hg flux was lower, ranging from ?2.5 to 18.7 n g m^?2 h^?1 and increased from south to north. The mean flux over the all profiles was 4.2 n g m^?2 h^?1. The total output of CO₂ and Hg degassing estimated along seismic ruptures for a survey area of 18.17 km² were approximately 0.57 Mt year^?1 and 688.19 g year^?1. It is recommended that land-use planners should incorporate soil gas and/or gas flux measurements in the environmental assessment of areas of possible risk. A survey of all houses along seismic ruptures is advised as structural measures to prevent the ingress of soil gases, including CO₂ and Rn, were needed in some houses.     

Application of eggshell waste for the immobilization of cadmium and lead in a contaminated soil

Liming materials have been used to immobilize heavy metals in contaminated soils. However, no studies have evaluated the use of eggshell waste as a source of calcium carbonate (CaCO₃) to immobilize both cadmium (Cd) and lead (Pb) in soils. This study was conducted to evaluate the effectiveness of eggshell waste on the immobilization of Cd and Pb and to determine the metal availability following various single extraction techniques. Incubation experiments were conducted by mixing 0–5% powdered eggshell waste and curing the soil (1,246 mg Pb kg^?1 soil and 17 mg Cd kg^?1 soil) for 30 days. Five extractants, 0.01 M calcium chloride (CaCl₂), 1 M CaCl₂, 0.1 M hydrochloric acid (HCl), 0.43 M acetic acid (CH₃COOH), and 0.05 M ethylendiaminetetraacetic acid (EDTA), were used to determine the extractability of Cd and Pb following treatments with CaCO₃ and eggshell waste. Generally, the extractability of Cd and Pb in the soils decreased in response to treatments with CaCO₃ and eggshell waste, regardless of extractant. Using CaCl₂ extraction, the lowest Cd concentration was achieved upon both CaCO₃ and eggshell waste treatments, while the lowest Pb concentration was observed using HCl extraction. The highest amount of immobilized Cd and Pb was extracted by CH₃COOH or EDTA in soils treated with CaCO₃ and eggshell waste, indicating that remobilization of Cd and Pb may occur under acidic conditions. Based on the findings obtained, eggshell waste can be used as an alternative to CaCO₃ for the immobilization of heavy metals in soils.