茶园土壤不同形态镍的含量及其影响因素

通过自然茶园土壤采样和室内实验分析,探讨浙江、江苏和安徽13个茶园土壤镍的污染状况、形态分布规律以及不同形态镍的含量与土壤镍总量和土壤理化性质的关系。结果表明：部分茶园土壤受到不同程度的镍污染;茶园土壤镍的形态分布有一定差异,按镍的含量多少排序,一般为残渣态＞交换态＞铁锰氧化物结合态＞有机结合态＞碳酸盐结合态;除了交换态以外的所有其他形态的镍含量均随土壤镍含量的增加而显著增加;碳酸盐结合态、铁锰氧化物结合态和残渣态镍含量随土壤pH的升高呈显著增加趋势,而交换态镍则呈减少趋势,但不显著;随土壤有机质含量的增加,铁锰氧化物结合态镍显著减少,而其他形态增加或减少的趋势均不显著;碳酸盐结合态、有机结合态和残渣态的镍含量均随阳离子交换量的增加显著增加;随粘粒含量的增加所有形态中的镍呈增加趋势,但除了残渣态外增加趋势均不显著。     

岩溶区典型石灰土Cd形态指示意义及风险评价——以桂林毛村为例

为了了解岩溶区石灰土中重金属Cd形态分配特征及富集情况,在桂林毛村采集了3种处于不同发育阶段的黑色、棕色和红色石灰土进行研究。通过原子光谱仪测试了Cd质量分数,运用改进的Tessier分析法测定了3种石灰土中Cd的可交换态(EXC)、碳酸盐结合态(CAB)、铁锰氧化物结合态(OXI)、有机结合态(ORG)、残渣态(RES)5种形态,并对其指示意义及风险进行了分析与评价,结果表明,3种石灰土中Cd质量分数从大到小依次为早期黑色石灰土、中期棕色石灰土、晚期红色石灰土。形态测试结果表明:黑色石灰土和棕色石灰土中Cd形态以铁锰氧化态和残渣态为主,占土壤Cd质量分数的63%以上,且5种形态质量分数从大到小顺序均为铁锰氧化态、残渣态、可交换态、碳酸盐结合态、有机结合态;红色石灰土Cd形态以残渣态为主,占土壤Cd质量分数的76%,形态分配特征从大到小为残渣态、铁锰氧化态、可交换态、碳酸盐结合态、有机结合态。Cd稳定度和富集程度评价结果表明:在黑色石灰土、棕色石灰土和红色石灰土中Cd稳定度逐渐减小,环境二次释放风险逐渐降低;富集程度从大到小依次为黑色石灰土、棕色石灰土、红色石灰土,其中Cd在黑色石灰土中呈显著富集状态,在棕色石灰土中呈中度富集状态,在红色石灰土中呈轻微富集状态。潜在生态风险评价和健康风险评价结果表明,由早期黑色石灰土到中期棕色石灰土和晚期红色石灰土,土壤中Cd的生态风险和健康风险均逐渐降低。研究结果可为岩溶区土壤重金属Cd污染修复与治理提供基础数据。     

类芽孢杆菌对铜陵新桥矿区土壤中Cu化学形态的影响

采用Tessier五步连续提取法和红外光谱技术,研究类芽孢杆菌对铜陵新桥矿区重金属污染土壤中Cu化学形态的影响,初步探讨了Cu形态变化的机理。结果表明,不同投入量的类芽孢杆菌接种到土壤培养一周后,土壤溶液pH值降低,土壤中可交换态、有机结合态Cu含量增加,碳酸盐结合态、铁锰氧化物结合态和残渣态Cu的含量降低。土壤中可交换态、铁锰氧化物结合态和残渣态Cu含量的变化主要受土壤溶液的pH值控制;有机结合态升高主要与类芽孢杆菌菌数及其代谢产生的低分子量有机酸有关。类芽孢杆菌可以改变矿区土壤中Cu的化学形态,影响Cu的生物有效性。     

广西象州与横县碳酸盐岩分布区土壤中Cd形态分布特征及影响因素

广西壮族自治区碳酸盐岩分布面积为96 372 km2,约占全区陆地国土面积的407%。由碳酸盐岩风化形成的土壤中Cd、Pb、Hg等重金属元素普遍富集。初步评价发现,农作物籽实对Cd的吸收量与土壤Cd含量无对应关系,农作物Cd超标多出现在土壤Cd含量较低的地区。进一步研究发现,Cd高含量的土壤中普遍含有铝土矿、Fe Mn结核等颗粒。为了探索土壤中Cd存在形态及其影响因素,选择了含铝土矿和铁锰结核的横县土壤和无铝土矿与铁锰结核的象州土壤,系统研究了土壤Cd形态差异及其影响因素。结果表明：(1)象州土壤中Cd主要以活动态形式存在,生物可利用性高,横县土壤中Cd主要以稳定态形式存在,生物可利用性低。(2)pH值为60是象州土壤Cd活动态含量的突变点,pH值在60处含量达到最大值;而在横县,pH降低使活动态Cd比例增加。(3)象州土壤中活动态Cd随有机质增加而增加,表明Cd被有机质弱吸附;而横县土壤有机质含量与Cd形态无明显相关性。(4)由铝土矿导致的土壤高Cd含量,多以残渣态形式存在,不会对动植物造成危害。     

成都平原区水稻土成土剖面Cd形态分布特征及影响因素研究

成土过程中不同形态镉(Cd)迁移转化的影响因素研究对于了解Cd的地球化学行为具有非常重要的意义。以四川省成都平原区农田生态系统水稻土剖面中不同形态Cd分布特征为例,探讨成土过程中不同形态Cd的迁移转化影响因素及其生态危害性。结果表明:总量Cd、离子交换态Cd和碳酸盐Cd均表现出表层富集,深层含量稳定的特征;岷江流域和沱江流域水稻土Cd含量的背景值分别为0.147,0.215mg·kg-1。外源输入耕层土壤中Cd主要为活动态,其增加量占Cd总量增加量的60.71%~90.52%,向下垂向迁移能力非常弱。成土过程随着土壤中Cd总量增加,稳定态Cd含量显著增加,而活动态Cd含量明显降低。土壤的pH值主要对碳酸盐态Cd含量有影响,pH值越大,其含量越高;随着土壤成熟度增高,粉粒和粘粒含量增加的同时,残渣态Cd含量显著降低,而有机结合态Cd含量显著增高。耕层土壤中Cd的生物有效性系数高达0.59~0.65,已经严重地影响到农作物安全。     

土壤有毒元素镉污染修复方法探讨

植物中的镉含量与土壤溶液中的镉含量成正相关关系，与土壤的pH值成负相关关系，土壤的酸碱度对植物吸收重金属元素具有显著的控制作用。因此，通过提高呈酸性土壤的pH值可以降低植物中的镉含量，解决植物中的镉超标问题。在土壤中施用硅酸钙、碳酸钙、熟石灰、硅酸镁钙等农用石灰性物质，特别是熟石灰，是提高土壤pH值最有效、最经济、最可行的方法。利用我省丰富而廉价的粘土资源，配合施加碱性物质，可更进一步提高土壤“抵抗力”，确保重金属镉超标区植物的安全。     

Effects of natural and calcined oyster shells on Cd and Pb immobilization in contaminated soils

In Korea, soils adjacent to abandoned mines are commonly contaminated by heavy metals present in mine tailings. Further, the disposal of oyster shell waste by oyster farm industries has been associated with serious environmental problems. In this study, we attempted to remediate cadmium (Cd)- and lead (Pb)-contaminated soils typical of those commonly found adjacent to abandoned mines using oyster shell waste as a soil stabilizer. Natural oyster shell powder (NOSP) and calcined oyster shell powder (COSP) were applied as soil amendments to immobilize Cd and Pb. The primary components of NOSP and COSP are calcium carbonate (CaCO₃) and calcium oxide (CaO), respectively. X-ray diffraction, X-ray fluorescence and scanning electron microscope analyses conducted in this study revealed that the calcination of NOSP at 770°C converted the less reactive CaCO₃ to the more reactive CaO. The calcination process also decreased the sodium content in COSP, indicating that it was advantageous to use COSP as a liming material in agricultural soil. After 30 days of incubation, we found that the 0.1 N HCl-extractable Cd and Pb contents in soil decreased significantly as a result of an increase in the soil pH and the formation of metal hydroxides. COSP was more effective in immobilizing Cd and Pb in the contaminated soil than NOSP. Overall, the results of this study suggest that oyster shell waste can be recycled into an effective soil ameliorant.     

宁沪高速公路句容段两侧土壤磁化率异常与重金属元素的关系研究

高速公路两侧土壤的磁化率从路中央向两侧具有逐渐降低的特征,相对应的样品中的重金属Cu、Pb、Zn、N i、Cr、Fe等元素的含量也具有从路中心向两侧逐渐降低的现象。相关分析表明,土壤磁化率与土壤中的Cu、Pb、Zn、N i、Cr、Fe的相关性显著,因而可以利用磁化率异常来指示高速公路两侧土壤的重金属污染状况。元素的赋存形态分析表明铁锰氧化物态与残渣态是Cu、Pb、Zn、N i、Cr、Fe的主要赋存形式;各元素的形态分析结果与土壤磁化率的相关统计分析表明,高速公路两侧土壤的磁化率与可交换态中的Cu、Pb、Zn、铁锰氧化物态中的Fe、Pb、Zn、有机还原态中的Cu、Cr、Fe、Zn和残渣态中的Cu、Pb、Zn、Cr、Co、N i具有明显的相关性。     

红壤中稀土元素结合形态的分布及分配

红壤剖面中稀土元素结合形态的分布研究表明,稀土元素的各种结合形态中以残渣态为主,其次为铁锰氧化物结合态,大部分稀土元素的可交换态、碳酸盐结合态、有机质结合态及酸溶态含量较为接近。稀土元素结合形态在剖面层中的分布大致可分为两类,一类以表层含量较高,如有机质结合态;另一类以深层含量较高,如可交换态、碳酸盐结合态、残渣态（大部分稀土元素表现为C层＞A层＞B层）和酸溶态（主要表现为C层＞B层＞A层）,而铁锰氧化物结合态变化较复杂,但主要集中在深层。不同母质对不同稀土元素各种结合形态的分布有一定的制约作用．表现为某些稀土元素的一些结合形态在一种或几种母质的红壤中占主导地位。稀土元素结合形态的分配研究表明,元素Pr、Tb、Tm、Yb、Lu的分异普遍比较显著,在不同结合形态中呈现富集或亏损,而Ce、Sm、Eu等元素则主要在某一种结合形态中发生分异。从稀土元素的各种结合形态与红壤的硅酸盐成分及其有机质含量、pH值间的相关分析认识到结合形态与红壤本身成分间的密切关系。     

Element fractionation by sequential extraction in a soil with high carbonate content

The influence of carbonate and other buffering substances in soils on the results of a 3-step sequential extraction procedure (BCR) used for metal fractionation was investigated. Deviating from the original extraction scheme, where the extracts are analysed only for a limited number of metals, almost all elements in the soils were quantified by X-ray fluorescence spectroscopy, in the initial samples as well as in the residues of all extraction steps. Additionally, the mineral contents were determined by X-ray diffractometry. Using this methodology, it was possible to correlate changes in soil composition caused by the extraction procedure with the release of elements. Furthermore, the pH values of all extracts were monitored, and certain extraction steps were repeated until no significant pH-rise occurred. A soil with high dolomite content (27%) and a carbonate free soil were extracted. Applying the original BCR-sequence to the calcareous soil, carbonate was found in the residues of the first two steps and extract pH-values rose by around two units in the first and second step, caused mainly by carbonate dissolution. This led to wrong assignment of the carbonate elements Ca, Mg, Sr, Ba, and also to decreased desorption and increased re-adsorption of ions in those steps. After repetition of the acetic acid step until extract pH remained low, the carbonate was completely destroyed and the distributions of the elements Ca, Mg, Sr, Ba as well as those of Co, Ni, Cu, Zn and Pb were found to be quite different to those determined in the original extraction. Furthermore, it could be shown that the effectiveness of the reduction process in step two was reduced by increasing pH: Fe oxides were not significantly attacked by the repeated acetic acid treatments, but a 10-fold amount of Fe was mobilized by hydroxylamine hydrochloride after complete carbonate destruction. On the other hand, only small amounts of Fe were released anyway. Even repeated reduction steps did not destroy the amorphous Fe oxides completely, showing that 0.1 mol L⁻¹ hydroxylamine hydrochloride was not strong enough to attack these oxides effectively.The extraction sequences were carried out not only on the soil samples, but also on their coarse and fine fractions (> or <2 μm). The fine fraction of the calcareous soil contained only 10% dolomite, but was enriched in organic matter and clay minerals, which also resulted in increased extract pH-values during the sequential extraction. Hence, the effects on ion release in the fine fraction were similar to those of the whole soil. Since the destruction of the organic matter was incomplete after regular oxidation, the H₂O₂-treatment of the fine fraction had to be repeated. The addition of the extractable amounts of the two fractions showed good agreement to the results obtained for extraction of the whole soils. Likewise the pH-values of the carbonate-free soil extracts did not increase significantly, therefore it was concluded that repetitions of extraction steps for this soil were not necessary.Extract-pHs should always be controlled so that extraction conditions are comparable; to be able to use the BCR extraction scheme or similar ones for carbonate- and organic-rich samples this is mandatory. Single extraction steps should be repeated if pH rises too much; additionally the oxidizing step should be performed more than twice for samples rich in organic substances, depending upon the violence of the reaction with H₂O₂. If these precautions are neglected the validity of the extraction data is likely to be questionable.     

Assessment of degradation of agricultural soils arising from brick burning in selected soil profiles

The study was conducted with the selected soil profile of burnt (soil around brick kilns) and unburnt (agricultural land) soils in the Dinajpur, Rangpur, Rajshahi, Khulna and Patuakhali districts at the western part of Bangladesh to evaluate the effects of brick kilns on soil degradation and environmental pollution. The pH values of the unburnt soils increased as a function of the soil depth for Rangpur, Khulna and Patuakhali, while decreased for the soil profiles in Dinajpur. Burning of soils significantly (p<0.05) decreased the average pH values of soils by 0.4 pH units (7 % increased over average content = IOAC), but strikingly increased the average EC values from 0.26 to 1.77 mS/cm (592 % IOAC) and the effect was pronounced with the depth function. The average sand content of the soil profiles increased by 330%, while the silt and clay contents decreased by 49 and 40 %, respectively. The average losses arising from the burning of agricultural soils were amounted to 63% for organic matter, 56 to 86 % and 23 to 88 % for available and total N, P, K and S, respectively. This huge loss through the burning of 1 m deep soil profile, i.e. almost 3/4^th of the deterioration of soil fertility is not only reducing the crop production but also polluting the associated environment and atmosphere. The burning of enormous C, N and S not only degrade the agricultural soils but also contributing to the changes in the global climate.     

Effects of contamination of single and combined cadmium and mercury on the soil microbial community structural diversity and functional diversity

To assess the effects of single and combined pollution of cadmium (Cd) and mercury (Hg) on soil micro-bial community structural and functional diversities, an incubation experiment was conducted, by employing two soils, namely, the marine sediment silty loam soil and the yellowish-red soil, in which five levels of Cd, Hg and Cd and Hg in combination were added. After being incubated for 56 days, the phospholipid fatty acids (PLFAs) profile and sole carbon source utilization pattern (BIOLOG) of the samples were tested. The results showed that the compo-sition of the microbial communities changed significantly at different levels of metals application. The principal component analyses (PCA) of PLFAs indicated that the structure of the microbial community was also significantly altered with increasing levels of metals, with increasing PLFAs biomarkers for fungi and actinomycetes, and in-creasing ratio of Gram-positive to Gram-negative bacteria. Sole carbon source utilization pattern analysis revealed that single and combined application of Cd and Hg inhibited significantly the functional activity of soil microorgan-isms, the functional diversity indices [Richness (S), Shannon-Wiener indices (H) and Evenness (EH)] were signifi-cantly lower in polluted soils than those in non-polluted soils, which also significantly altered with increasing levels of metals. PCA for the sole carbon source utilization pattern also indicated that the metal contamination could result in a variable soil microbial community. The results revealed that the combination of Cd and Hg had higher toxicity to soil microbial community structural and functional diversities than the individual application of Cd or Hg.     

岩溶区典型土壤对Cd2+的吸附特性

文章采用有序批试验,就岩溶区两种典型石灰土（棕色、黑色石灰土）对Cd2+的吸附行为进行研究。试验结果表明:石灰土对重金属Cd2+具有较强的吸附能力（平均吸附率范围89.84~98.84）,黑色石灰土的吸附能力高于棕色石灰土,吸附量随平衡浓度的增加而增大;Langmuir和Freundlich方程均能很好地描述两种石灰土对Cd2+的等温吸附过程,Freundlich方程拟合最优;两种石灰土吸附镉的动力学特征相似,吸附过程可分为快速反应、慢速反应和吸附平衡3个阶段,棕色石灰土对Cd2+吸附动力学的最优模型为Elovich方程和双常数方程（R>0.9）,黑色石灰土仅在Cd2+初始浓度为100 mg/L条件下,Elovich方程、双常数方程和W-M方程的模拟达到较显著水平（R>0.8）;有机质、碳酸钙含量及CEC值是影响石灰土对Cd2+吸附能力的主控因素,铁、铝、硅氧化物含量对Cd2+吸附影响不大;综合热力学、动力学及影响因素分析认为石灰土对Cd2+吸附机理包括土壤颗粒表面官能团的专性吸附及不均匀粒内扩散、静电作用等非专性吸附过程。      

Accumulation of trace elements in paddy topsoil of the Wudang County, Southwest China: parent materials and anthropogenic controls

The properties of soils derived from carbonate rock, red residua, and sand-shale in Guizhou province, China are essentially different. However, the effects of parent material and anthropogenic activities on the concentration of trace elements when the soils are converted into paddy soils are unknown. A total of 319 paddy topsoil samples (0–20 cm) were collected in a typical region to determine their relative contribution to the concentrations of trace elements in the soil. The results indicated that the contents of trace elements were far beyond the uncultivated soil background and the input of organic fertilizers was presumably responsible for accumulation of trace elements. In addition, principal component analysis showed that the first component included Cd, Cr, and As, which strongly associated with anthropogenic activities. Pb and Hg formed the second component, which related to both parent materials and anthropogenic input. Furthermore, the Cr and Hg contents in paddy soil derived from carbonate rock have higher values than other types of soils partly because of the high background values as well as slightly alkaline condition. In the paddy soil derived from red residua, high physical clay content accounted for enrichment of Pb.     

南海诸岛土壤的形成和年龄

本文在阐明南海珊瑚诸岛土壤的生物集聚过程、积盐和脱盐过程,以及有关的土壤诊断特性基础上,进一步介绍了那里的磷质石灰土和滨海盐土两大土壤类型,它们的空间分布及其与岛屿结构、地形、植被和鸟类活动之间的关系。最后,作者针对南海珊瑚岛土壤的特征,运用(１４)Ｃ方法探讨了它的年龄及其与土壤形成、发育之间的相互关系。     

广西南流江流域土壤-水稻系统Cd生物有效性及影响因素

广西南流江流域第四系发育形成的土壤中Cd等重金属含量较低,但水稻籽实Cd超标率很高。为了查清Cd在南流江流域土壤-水稻系统中的分布和迁移规律及其生物有效性的影响因素,按照不同成土母质物源分区,系统采集了水稻及其对应的根系土样品,测试了水稻籽实Cd、土壤Cd、pH、Corg、N、S、Mn及氧化物等指标,部分土壤样品进行了七步顺序提取法实验。结果表明,不同母质根系土Cd总量大小顺序为碳酸盐岩区>水系上游第四系区>水系中游第四系区>水系下游第四系区>碎屑岩区,而水稻籽实中Cd含量顺序却基本相反,两者之间不具有明显相关性(r=-0.030,p=0.84 )。形态数据显示,水溶态Cd与籽实Cd相关性较好,能够较好指示研究区Cd的生物有效性,同时,土壤水溶态Cd占比受土壤pH、土壤CaO、Mn、有机碳(Corg)等土壤指标的控制。     

Effect of simulated acid rain on soil acidification and rare earth elements leaching loss in soils of rare earth mining area in southern Jiangxi Province of China

Acid rain has long been a great concern because of environmental and ecological problems; however, the effect of acid rain on soil acidification, loss of rare earth elements (REEs) via the leaching process, and transformation are rarely reported in rare earth mining areas. Through a simulated acid rain leaching experience, the effect of acid rain was studied on soil acidification and REEs leaching loss. The results showed that the tested soil had certain buffering capacity against nearly neutral rainwater. However, simulated acid rain of low and very low pH (pH ≤ 3.5) had a greater impact on soil acidification. After eluviating by simulated acid rain of pH 3.5 for 36 h, the pH of tailings, garden soil, paddy soil, and alluvial soil decreased by 20.41, 32.03, 13.60, 16.88, and 15.83 %, respectively, from the original values. For simulated acid rain of pH 2.5, it was 31.89, 44.76, 31.26, 29.87, and 29.15 %, respectively. After simulated acid rain eluviations of low and very low pH (pH ≤ 3.5), the order of the leaching rate of REEs in the tested soil was as follows: garden soil > tailings > paddy soil > alluvial soil. For nearly neutral rainwater (pH 4.5 simulated acid rain and pH 5.6 deionized water), the order was tailings > garden soil > paddy soil > alluvial soil. For simulated acid rain of the same pH, the leaching amounts of REEs in tailings and garden soil were higher than those in paddy soil and alluvial soil. After leaching by low and very low pH-simulated acid rain (pH ≤ 3.5), the peak value of the leaching amount of REEs in all tested soil appeared at 2 h, and then gradually reduced and reached a stable leaching state 20 h after leaching. On leaching by simulated acid rain of pH 2.5, the maximum REEs contents of leachate in tailings, garden soil, paddy soil, and alluvial soil were 156.35, 145.82, 99.88, and 85.97 mg/L, respectively. For pH 3.5 of simulated acid rain, it was 130.49, 110.49, 80.57, and 62.73 mg/L, respectively. On leaching by simulated acid rain of pH 4.5, the maximum contents of REEs in the leachate were 53.46 and 29.82 mg/L, respectively, which were observed after leaching for 6 h in tailings and garden soil that became stable 12 h after leaching. The contents of leached REEs in paddy soil and alluvial soil were always in a lower and stable state. After eluviations with deionized water of pH 5.6, the contents of leached REEs in other soils were lower, except for the slight fluctuations in tailings. The maximum content in the leachate of REEs was in the water-soluble and exchangeable fraction. When bound to carbonate fractions, REEs were not detected in the leachate. REEs bound to iron-manganese (Fe–Mn) oxides fraction and to organic matter fraction in the leachate possibly came from the tested soil or from the REEs transformation during the migration process. The content of residual fraction REEs in the leachate was very low.     

我国不同区域农田养分平衡对土壤肥力时空演变的影响

区域农田养分盈亏是驱动农田土壤肥力时空变化的主要因素。对我国6个农业生态试验站（海伦、沈阳、 栾城、长武、常熟、鹰潭）站区农田土壤肥力在近年来时空演变的研究表明,除了海伦站黑土和常熟站水稻土的有机质和全氮平均含量下降外,其他站区均呈现增加趋势,主要原因是黑土和乌栅土有机质和全氮含量较高,目前农田有机C和N投入水平无法维持其平衡;6个站区土壤速效磷有增有减,而土壤速效钾除了栾城和鹰潭站区域外均呈降低趋势。从站区农田养分的年平衡与土壤养分的年变化量关系看,农田氮、磷、钾的盈亏量决定了土壤养分的变化方向。土壤有机碳和全氮的初始含量过高（分别超过15.1 g/kg和1.60 g/kg）时,也会导致其年际间的变化方向从增加变为降低。农田氮素盈亏量与土壤全氮变化量之间相关不显著,主要是由于化肥投入和作物籽粒输出的农田氮平衡不能完全代表土壤氮素的真实盈亏情况;而农田磷素和钾素的盈亏量与土壤速效磷和速效钾的年变化量的显著相关。     

Remediation of soil co-contaminated with pyrene and cadmium by growing maize (Zea mays L.)

Sites co-contaminated with organic and metal pollutants are common and considered to be a more complex problem as the two components often causes a synergistic effect on cytotoxicity. Phytoremediation has been proposed as a cost-effective technology for treating heavy metal or organic contamination and may be suitable for remediation of co-contaminated soil. This study investigated the concurrent removal of pyrene and cadmium in co-contaminated soil by growing maize in a pot experiment. At the end of 60 day culture, pyrene in spiked soil diminished significantly, accounting for 21–31 % of the initial extractable concentration in unplanted soil and 12–27 % in planted soil. With the increment of cadmium level, the residual pyrene both in unplanted and planted soil tended to increase. Although the presence of cadmium increased the accumulation of pyrene in maize, plant accumulation only account for less than 0.30 % of the total amount of the dissipated pyrene in vegetated soils. It implied that plant-promoted microbial biodegradation was the predominant contribution to the plant-enhanced dissipation of pyrene in co-contaminated soil. Unlike pyrene, heavy metal cadmium cannot be degraded. It was observed that maize can concurrently removed about on the average 0.70 % of the total cadmium amount in soil by plant uptake, but cadmium phytoextraction would be inhibited under contamination of pyrene. Maize CT38 can normally grow in the co-contaminated soil with high level cadmium and pyrene and can effectively remedy the sites co-contaminated with these two types of contamination, which suggest the possibility of simultaneous phytoremediation of two different contaminant types.     

Shear Modulus and Damping Ratio of Organic Soils

The paper presents results from a laboratory investigation into the dynamic properties of natural intact and model organic soils by means of resonant-column tests. The natural intact organic soils were sands, cohesive soils and peats with varying content of calcium carbonate. The model organic soils were formed in laboratory by mixing kaolinite and paper pulp. The influence of various soil parameters, such as strain level, confining stress, void ratio, plasticity index, organic content and secondary consolidation time on shear modulus, G, and damping ratio, DT, is presented and discussed. The test results on natural organic soils show that only high organic contents (OC ≥ 25%) have significant influence on G and DT at both small and high shear strains. For the model organic soils, however, a significant influence of even lower values of organic content (5% ≤ OC ≤ 20%) on G at small strains and DT at both small and high strains is observed.