不同活化剂对铜冶炼厂污染土壤中铜的活化

采用等浓度的不同有机酸、有机盐、人工螯合剂和不同pH水溶液活化污染土中铜,研究比较了各有机活化剂与不同pH水溶液的活化能力与活化特性。结果表明,四种有机酸活化量排序在不同污染程度土中稍有不同,在2号土(污染较重)中为柠檬酸>草酸>酒石酸>DL-苹果酸;在1号土(污染较轻)中为草酸>柠檬酸>酒石酸>DL-苹果酸。而有机盐的活化量在不同污染程度土中排序一致,即EDTA>柠檬酸三钠>草酸钠>酒石酸钾钠。另外,所有有机酸的活化能力都比其相应的盐大。不过同是活化量大的草酸、柠檬酸和EDTA,它们的活化特性不一样,EDTA属于速效型强活化剂,草酸属于缓效型强活化剂,而柠檬酸在2号土中表现为速效型,在1号土中表现为缓效型。pH1、pH2、pH13、pH14的水溶液活化量较大,pH2的水溶液在2号土中活化效果良好,而在1号土中与其它pH值溶液一样,由于土壤的缓冲作用,滤液的pH均趋于中性,铜的活化效果不明显。

Enhanced electrokinetic remediation of cadmium-contaminated natural clay using organophosphonates in comparison with EDTA

Soil contamination by metals is a worldwide environmental problem. Electrokinetic extraction is a promising technology for in-situ remediation of contaminated soils of low hydraulic permeability. However, the extraction of metals is usually hindered by the high buffer capacity of natural soils. Organophosphonates are strong metal chelates as ethylenediaminetetraacetic acid(EDTA) which has been widely studied in the enhancement of electrokinetic remediation. In this study, batch desorption experiments and bench-scale electrokinetic extraction experiments were carried out to study the effect of two organophosphonates, i.e.,(nitrilotrimethylene)triphosphonate(NTMP) &(ethylenedinitrilo)-tetramethylenephosphonate(EDTMP), on the extraction of cadmium from a natural clay in comparison with EDTA. Results of the batch desorption experiments showed that more than 75% of the sorbed cadmium could be dissolved into solution using 0.1 mol·L^(-1) organophosphonates or EDTA in the wide p H range of 1–11. Results of the electrokinetic extraction experiments showed that the cadmium spiked in the specimen migrated towards the anode with the enhancement of NTMP,EDTMP, and EDTA under a constant voltage gradient of approximately 1.0 V·cm-1. Although cadmium mobilization enhanced by EDTA was more efficient than that by the organophosphonates, accumulation of cadmium was observed in the vicinity of the anode. The average removal efficiencies of cadmium from the soil after approximately 5 days of electrokinetic extraction enhanced by 0.1 mol·L-1 NTMP(22.8%) and EDTMP(22.4%) were higher than that by 0.1 mol·L^(-1) EDTA(15.1%).

Can Cadmium Uptake by Chinese Cabbage be Reduced After Growing Cd-Accumulating Rapeseed?

Rapeseed （Brassica campestris L.）, a Cd-accumulating crop, is effective in reducing plant-available Cd from soil. A pot experiment was conducted to test the hypothesis that the Cd uptake by Chinese cabbage （Brassica pekinensis Rupr.） grown in rotation with rapeseed would be reduced due to the efficient removal of bioavailable Cd from soil solution by the rapeseed crops. The Cd removal by shoot for the rapeseed cultivar Zhucang Huazi ranged from 0.24% to 0.99% in natural Cd-contaminated soil （soil A） and from 0.63% to 1.23% in artificial Cd-contaminated soil （soil B） during the growth period of 4 7 weeks; whereas that for the rapeseed cultivar Chuanyou Ⅱ-93 ranged from 0.25% to 0.66% and from 0.38% to 1.02%, respectively. Chinese cabbage grown in the pots with soil A for five weeks after harvesting rapeseed exhibited a significantly lower Cd concentration compared to that grown in the control pots （uncropped with rapeseed）. However, the rotation of rapeseed did not lower the Cd concentration of Chinese cabbage on soil B. Although an increase of Cd uptake was observed in the rapeseed cultivars with growth time, and the decrease of soil NH4OAc-extractable Cd was found only in the natural rather than artificial Cd-contaminated soil.

Natural Attenuation and Biostimulation of Biodiesel Contaminated Soils from Southern Brazil with Different Particle Sizes

Biodiesel bioremediation in soils may occur by natural attenuation or by engineered techniques, such as biostimulation and bioaugmentation. The present study evaluated the degradation of biodiesel in two soils with different particle size characteristics by the bioremediation processes of natural attenuation and biostimulation. The experiment was carried out ex situ, with the factors temperature, moisture content, and pH being controlled for the experimental period of 110 days. The study aimed at evaluating the biodegradation of a clayey soil （A） and a sandy soil （B）, both contaminated with pure biodiesel, by using the analytical methods of respirometry and gas chromatography. Biostimulation treatments using nitrogen, phosphorus, and potassium solutions （NPK） promoted higher microbiological activity in both soils. At the end of the experiment, it was observed that biostimulation was more efficient when compared to natural attenuation, showing higher biodiesel degradation for both soils A （59.76%） and B （90.41%）.

Assisted Natural Remediation of a Trace Element-Contaminated Acid Soil:An Eight-Year Field Study

There are many remediation techniques for organic contaminated soils,but relatively few of them are applicable to trace elementcontaminated soils.A field experiment was carried out to investigate assisted natural remediation(ANR) of an acid soil contaminated by As,Cd,Cu,Zn and Pb using one inorganic amendment,sugar beet lime(SL),and two organic amendments,biosolid compost(BC)and leonardeite(LE).The experiment was arranged in a completely randomized block design with four treatments in three replicates:1) a non-amended control(NA);2) SL amended at 30 Mg ha^(-1) year^(-1);3) BC amended at 30 Mg ha^(-1) year^(-1) and 4) LE amended at 20 Mg ha^(-1) year^(-1) plus SL amended at 10 Mg ha^(-1) year^(-1)(LESL).The amended plots received two doses of each amendment(DO2):one in October 2002 and another in October 2003.The plots were then divided in half into two subpolts and one subplot received another two doses of the same amendments(DO4) in October 2005 and October 2006.In 2011,the pH values of the amended soils were greater than that of the NA soil,with the SL-amended soil showing the highest pH.Total organic carbon(TOC) was also greater in the amended soil,and greater with DO4 than with DO2.Amendments reduced the concentrations of 0.01 mol L^(-1) CaCl_2-extractable Cd,Cu and Zn,especially in the SL-amended soil.Plant cover of colonizing vegetation was enhanced by amendments,but was independent of amendment doses.Changes in soil properties from 2003 to 2011 showed that the first amendment application of DO2 caused a high differentiation between all the amendment treatments and the NA treatment.After the second application of DO2,soil pH and TOC continued increasing slowly.Further two applications of amendments(DO4) caused differences only in the organic treatments.Plant cover increased over time in all the treatments including NA.It could be concluded that the slow and steady natural remediation of this soil could be enhanced by amendment application(ANR).