Co-planting can phytoextract similar amounts of cadmium and zinc to mono-cropping from contaminated soils

Co-planting crops normally decreases the main crop yield due to the reduced soil surface area occupied by the main crop. However, in our previous experiments, co-planting Sedum alfredii, a shade-requiring, Cd and Zn-hyperaccumulating plant, with corn increased the biomass and metal phytoextraction of S. alfredii. This experiment was conducted to verify if co-planting another hyperaccumulator, Thlaspi caerulescens, with ryegrass (Lolium perenne) in a pot-trial could obtain a similar result. The soil was separated by two permeable nets with a 2 mm interface soil layer to obtain a shared rhizosphere zone. Soluble metal concentrations in the soil in different rooting zones were measured using 0.01 mol L^?1 CaCl₂ extraction. The results showed that the growth of T. caerulescens was significantly promoted by co-planting, with a growth increase of about 2-fold compared with monoculture growth. The total uptake of Cd and Zn by T. caerulescens was not decreased by co-planting, and resulted in similar phytoextraction rates for Cd (about 26.6% of the soil total Cd) and Zn (about 2.4% of the soil total Zn) when compared with monoculture, though the T. caerulescens population was decreased by 50% because of co-planting. Analysis of soil samples showed that T. caerulescens substantially reduced the concentrations of 0.01 mol L^?1 CaCl₂ extractable Cd and Zn throughout the soil, even in the interface area and the ryegrass rooting area. The ryegrass roots did not mobilize more metals for the co-planted T. caerulescens. Based on these results, existing grass on contaminated land could be partly left while planting metal hyperaccumulators for phytoremediation in order to reduce runoff from the contaminated soil. However a field scale trial would be required for these results to be verified.     

Potential of Ipomoea aquatica cultivars in phytoremediation of soils contaminated with di-n-butyl phthalate

Five different genotypic cultivars of Ipomoea aquatica commonly grown in Southeast Asia were cultivated to investigate their accumulation variation of di-n-butyl phthalate (DBP) and their potential for phytoremediation of three soils contaminated with DBP (4.5, 10.3 and 22.5 mg kg^?1). The results indicated different cultivar tolerance to DBP. DBP concentration in the shoots of the cultivars and residual DBP concentration in the soil were proportional to initial DBP concentrations in the soil and significantly different with different genotypic cultivars, indicating that the removal of DBP is cultivar-specific. DBP removal in the soil with indigenous DBP was higher than that in freshly DBP-spiked soils. The cultivars of local white-skin I. aquatica (cultivar V₅) and Taiwan filiform-leaf I. aquatica (cultivar V₁) presented the highest phytoremediation potential in the soil containing indigenous DBP and in freshly DBP-spiked soil, respectively. The translocation factor (TF, DBP concentration ratio of the shoots to the roots) and bioconcentration factor (BCF, DBP concentration ratio of the plant to the soil) also significantly varied with different cultivars, and they did not follow distribution profiles correlated to DBP removal indicating that phytoextraction was not the dominant DBP removal mechanism. Finally, the potential ability of different cultivars of enhancing biodegradation varied widely.     

Polycyclic aromatic hydrocarbons and phthalic acid esters in the soil-radish (Raphanus sativus) system with sewage sludge and compost application

We studied the accumulation of polycyclic aromatic hydrocarbons (PAHs) and phthalic acid esters (PAEs) in a latosolic red soil and radish (Raphanus sativus) with application of sewage sludge at rates of 10, 20 and 40 g kg(-1) soil or compost at rate of 10 g kg(-1) soil. In radish the concentrations of individual PAHs and PAEs varied from non-detectable to 803 microg kg(-1) dry weight (d.w.) and from non-detectable to 2048 microg kg(-1) d.w., respectively. Compared to the control, higher application rates of sewage sludge resulted in pronounced increases in shoot, root and soil concentrations of PAHs and PAEs. PAE concentrations in radish grown in soil spiked with sludge compost were higher while the PAH concentrations were comparable to those receiving 10 g kg(-1) of sewage sludge. However, the root biomass of radish in soil amended with compost was significantly higher and the shoot-to-root ratio was significantly lower than in the other treatments. The bioconcentration factors (BCFs, the ratio of contaminant concentration in plant tissue to the soil concentration) of di-n-butyl phthalate and di(2-ethylhexyl) phthalate in both shoots and roots and of total PAH concentrations in roots were less than 1.0, but some BCFs for individual PAHs were high with a maximum value of 80.     

资源植物罗布麻的愈伤组织诱导和植株再生研究

以罗布麻（Apocynum venetum L.）无菌苗的叶、茎和根作为外植体,在不同激素与浓度组合的MS培养基上进行愈伤组织诱导和植株再生研究。结果表明,在多个激素浓度配比的培养基中,罗布麻叶和茎的愈伤组织诱导率均可达到100%;但进一步将愈伤组织转接到含有不同激素组合的培养基进行不定芽分化时,叶和茎来源的愈伤组织的不定芽分化率有很大不同,茎来源的愈伤组织虽可在多个培养基中有不定芽分化,但最高诱导率仅达20%;而叶片来源的愈伤组织虽仅有4个激素组合培养基中有不定芽的分化,但最高分化率可达到35%。因此,构建罗布麻再生体系的最佳外植体应选择叶片。愈伤组织诱导与不定芽分化的最佳培养基均为：MS＋NAA0.1 mg/L＋6-BA 1.0 mg/L;不定芽在1/2MS＋NAA 0.2 mg/L生根培养基的生根效果最佳,不仅根群质量好,且生根率也高达100%;此再生苗的移栽成活率也最高,在适宜条件下可达75%。     

Cadmium Sorption Characteristics of Soil Amendments and its Relationship with the Cadmium Uptake by Hyperaccumulator and Normal Plants in Amended Soils

In order to select appropriate amendments for cropping hyperaccumulator or normal plants on contaminated soils and establish the relationship between Cd sorption characteristics of soil amendments and their capacity to reduce Cd uptake by plants, batch sorption experiments with 11 different clay minerals and organic materials and a pot experiment with the same amendments were carried out. The pot experiment was conducted with Sedum alfredii and maize (Zea mays) in a co-cropping system. The results showed that the highest sorption amount was by montmorillonite at 40.82 mg/g, while mica was the lowest at only 1.83 mg/g. There was a significant negative correlation between the n value of Freundlich equation and Cd uptake by plants, and between the logarithm of the stability constant K of the Langmuir equation and plant uptake. Humic acids (HAs) and mushroom manure increased Cd uptake by S. alfredii, but not maize, thus they are suitable as soil amendments for the co-cropping S. alfredii and maize. The stability constant K in these cases was 0.14–0.16 L/mg and n values were 1.51–2.19. The alkaline zeolite and mica had the best fixation abilities and significantly decreased Cd uptake by the both plants, with K ≥ 1.49 L/mg and n ≥ 3.59.     

Characterization of cadmium desorption in soils and its relationship to plant uptake and cadmium leaching

Experiments on Cd desorption were conducted with a range of water-to-soil ratios to assess the desorption characteristics of Cd in soils and the availability of Cd for absorption by plant roots and leaching to groundwater, Soil samples were collected from sites contaminated by a former Pb and Zn smelter, by sewage irrigation, or with artificial additions of Cd and sewage sludge. Glasshouse pot experiments were conducted in which the yield and Cd uptake of crop plants were determined. Cadmium leached from soil columns was also studied using soil lysimeters. The soil solution Cd concentration decreased with increasing solution-to-soil ratio and followed a negative power function. Two constants obtained from logarithmic linear regression were identified. The intercept (C₁) was Cd concentration in the soil solution where the solution/soil ratio was equal to 1 and this constant was the intensity factor of the initial element supply in the soil. The slope (a) showed a decreasing trend for Cd concentration in the soil solution which was related to the soil buffering capacity. A corrected concentration (C₁/a) is proposed for expressing soil desorption ability. This combined index was significantly correlated with Cd uptake by plants and also with Cd leached from soil columns.     

减少农业对水体污染的对策与措施

水体富营养化是一个全球关注的问题。逐渐增加的化肥施用量和畜禽养殖业产生的粪便进一步引起营养流失,进而产生了N、P营养物质的不平衡。因此农业面源污染已被视为水体富营养化的主要污染源。本文简要地概述了农业面源污染对造成水体富营养化的危害,同时介绍了国内外防治农业面源污染的主要措施,包括面源控制措施和转移转化措施。指出了建立稳定、和谐与良性循环的农业生态系统是治理农业面源污染的长久之计。     

植物地上部氮素损失及其机理研究现状与展望

植物地上部气态氮化合物挥发是氮素损失的重要途径, 同时也是大气NH₃和N₂O的重要来源, 因此, 研究植物氮素挥发损失对于大气环境保护和提高氮肥利用率具有重要意义。该文综述了各种气态氮化物(NH₃、NO、NO₂、N₂O和N₂)损失及其机理, 结果表明, 活性氮源积累和同化的不平衡, 是植物氮素挥发损失的主要因素; 环境条件(光、温、水、肥、气)和植物生理病害、衰老等因素, 均可引起植物活性氮源积累和同化的不平衡, 导致植物地上部氮素的挥发损失, 但各种气体氮化物能否从叶面挥发, 还要取决于气体氮化物的补偿点; NH₃和N₂O是主要的植物氮素损失形态, 主要氮素挥发损失发生在生育后期, 但不同氮素损失形态对植物生育期的响应并未完全相同。该文较完整地归纳总结了植物氮素挥发损失的作用机理, 指出了目前研究尚需要解决的重要问题: 1)氮素损失形态间的内在关系并不清楚, 尚不能完整地解释植物氮素挥发损失机制, 尤其是酶催化协同机制; 2)植物叶际气态氮化物交换(包括吸收和释放)作用及其机理也未完全清楚, 因而难以正确评估植物氮素的挥发损失; 3)植物衰老对增强氮素挥发损失有明显促进效果, 但有关其生理机制尚不完全清楚; 4)缺乏可行的抑制植物氮素挥发技术方法, 故还难以有效缓解肥料氮的挥发损失, 提高氮肥利用率。