摘要
以第四纪红黏土红壤和长江冲积物形成的高砂土为供试土壤 ,分别加入 3个浓度的 Cu2 + (1 0 0 ,2 0 0 ,40 0 mg/kg)或 Cd2 + (5 ,1 0 ,2 0 mg/kg)模拟土壤污染 ,设置接种蚯蚓 (Pheretima sp.)处理与不加蚯蚓对照 ,并种植黑麦草 (Lolium multiflorum) ,研究蚯蚓活动对土壤中 Cu、Cd生物有效性的影响 ,以揭示蚯蚓在植物修复重金属污染土壤中的作用。结果表明 :蚯蚓活动显著增加红壤中 DTPA提取态 Cu的含量 ,只有在浓度低于 2 0 0 mg/kg Cu的处理中 ,才能增加 Ca Cl2 提取态 Cu的含量 ,对 H2 O提取态 Cu影响甚微 ;而对高砂土上 Cu、Cd的各种形态影响均不显著 ;除红壤中浓度高于 40 0 mg/kg Cu和 1 0 mg/kg Cd处理外 ,蚯蚓活动显著提高了两种土壤上黑麦草地上部的生物量 ;接种蚯蚓后各种重金属处理中黑麦草对 Cu的吸收量也显著增加 ,而 Cd的吸收量变化不大。
Phytoremediation of heavy metals in contaminated soil has been widely accepted as a cost-effective, environmental-friendly technology. Metal-accumulating plants are usually planted to remove metals from soils by concentrating them in the harvestable parts, while the efficiency depends on the amount of aboveground biomass and the bioavailabililty of metals. Though addition of chelating agents has been shown to increase metal bioavailabililty and phytoremediation efficiency, it costs too much and shows environmental risk.;Beneficial roles of earthworms on soil fertility, nutrient cycling and plant growth have been commonly observed. Earthworms can influence metal mobility in soil through burrowing and casting activity. The question arises whether earthworm activity can actually increase metal bioavailability and hence promote the uptake by plants, or whether earthworms have a positive effect on phytoremediation. The objective of this study was to investigate the effect of earthworm on the bioavailability of Cu and Cd in soils through a pot experiment. ;Two soils, red soil from Jiangxi Province and Orthic aquisols from Jiangsu Province, were used in the pot experiment. Each soil was divided into seven equal parts of 6^0 kg each and amended respectively to contain 0, 100, 200, 400 mg Cu/kg and 5, 10 and 20 mg Cd/kg by adding appropriate concentrations of CuSO-4 and CdCl-2. After two-month incubation, metal-treated soil samples were divided into two groups with 3 pots for each group as replicates (1 kg soil/pot). One group received six earthworms (Pheretima sp.) for each pot, the other group did not contain any earthworms. All earthworms were collected from an uncontaminated soil in Nanjing Agricultural University and had a mean fresh weight of 0^6g. Each pot was added to 0^3333g KH-2PO-4 and 0^3477g Urea as mineral nutrients and received 15 pre-germinated ryegrass seeds (Lolium multiflorum). The pots were put in greenhouse and were incubated for one month. ;After one month, aboveground ryegrass biomass was weighed. Soil pH (2g soil in 10ml 0^01 mol/L CaCl-2) was tested using a Beckman pH meter. Concentrations of Cu and Cd in ryegrass were determined by using atomic absorption spectrophotometey (AAS) after cineration-digestion. Fractions of the metal in soils were also tested using sequential extraction procedures: (1)Water-soluble Cu and Cd: extracted with deionized water, with a water:soil ratio of 10∶1; (2)CaCl-2-extractable Cu and Cd: extracted with 0^01mol/L CaCl-2, with a solution:soil ratio of 10∶1; (3)DTPA-extractable Cu and Cd: extracted with DTPA, pH 7^3, with a solution:soil ratio of 2∶1. Cu and Cd brought into solution were measured by AAS.;It was found that earthworm activity significantly decreased the pH for the Red soil, a key chemical factor affecting bioavailability of nutrient elements and heavy metals in soil, but had little effect on pH for the Orthic aquisols. Aboveground biomass of the ryegrass increased dramatically from 33% to 96% in the presence of earthworms except for the treatments with 400 mg Cu/kg soil and 10 mg Cd/kg soil. Earthworm activity markedly increased concentrations of DTPA-extractable Cu and water-soluble Cd for the red soil, however, it did not affect three fractions of Cu or Cd for the Orthic aquisols . Total uptake of Cu by the ryegrass was enhanced by earthworm activity in the two soils, while no significant difference was observed in concentration of Cu or Cd in plant tissue between treatments with and without earthworm addition.;It is very likely that earthworm activity can increase phytoremediation efficiency by improving soil conditions and enhancing plant growth and the uptake of heavy metals by plant. But this effect of earthworm appeared to be metal and soil specific.
出处
《生态学报》
CAS
CSCD
北大核心
2003年第5期922-928,共7页
Acta Ecologica Sinica
基金
国家自然科学基金资助项目 (40 2 71 0 68)~~
关键词
蚯蚓
土壤
铜
镉
生物有效性
污染
植物修复
earthworm
soil contamination by Cu or Cd
bio-availability of heavy metals
phytoremediation
