Assessment of earthworm activity on Cu, Cd, Pb and Zn bioavailability in contaminated soils using biota to soil accumulation factor and DTPA extraction

Abstract

The study aims to investigate effect of earthworm activity on metal bioavailability in soils using their BSAF-metals. Based on a microcosmic laboratory experiment, epigeic species Amynthas corticis (A. corticis) and endogeic species Amynthas robustus (A. robustus) were cultured in two types of soils contaminated by Cd, Zn, Pb and Cu for 120 days. Earthworm characteristics (i.e. numbers, biomass and BSAF), soil properties (i.e. pH, organic C and N contents along with their components such as mineralization and microbial masses) and DTPA extracted metals in soil were determined. After the incubation, the biomass and survival numbers of both earthworm species decreased significantly (P < 0.05). The accumulation of Cd, Zn and Pb in earthworm tissues and BSAF-metals were earthworm species dependent. According to two-way ANOVA, BSAF-Pb clearly showed the effect of different species of earthworms while BSAF-Cu indicated an interactive effect of earthworms and soil type. Earthworms changed soil properties significantly, especially for mineralized C (C min), dissolved N (N dis) and pH (P < 0.05). Earthworm activity increase DTPA extracted Zn and Cu, and the effect of A. robustus were stronger than for A. corticis. Redundancy analysis (RDA) showed that BSAF-Cu and BSAF-Pb contributed for respectively 51.9% and 51.7% of soil properties and DTPA metal changes, indicating that the effects of BSAF-Cu and BSAF-Pb on soil properties and on metal bioavailability in soil were similar. BSAF-Cu, indicating the interactive effect of earthworms and soil, accounted for 38.5% and 45.1% of soil properties and soil metal bioavailability changes. BSAF-Pb, representing the effect of earthworm species, accounted for 13.3% and 6.6% of soil property and soil metal bioavailability variations. Stepwise regression indicated that earthworm might change soil properties through their activities and interactions with soil, and hence increase heavy metal bioavailability. It suggested that BSAF is an important indicator for evaluating the effect of earthworm activity on soil metal bioavailability and designing remediation strategies.

The Effect of Soil Amendments on Trace Elements’ Bioavailability and Toxicity to Earthworms in Contaminated Soils

“…The data on metal toxicity in contaminated soils are scarce and difficult to interpret due to multiple contaminations, the diverse ages of contamination, and the effects of the soil properties on metal availability. There are studies [8,28,30,36,45,46] explaining the mechanisms of earthworms' survival under stress conditions, which are supported by efficient innate immune mechanisms based on the cellular activities of coelomycetes and humoral immune proteins.…”

“…For this purpose, earthworms are considered to be the most important bio-indicators due to their intimate (external and internal) contact with the soil and the possibility they offer of evaluating the potential of TE bioaccumulation and food-chain transfer [7,13,31,33,34]. Studies published in recent years pointed out that the variation in the TE bioaccumulation in worms may be dependent on their bioavailability [35][36][37][38][39][40], it is as affected by soil factors influencing metal solubility (pH and redox) and complexation with organic matter [41][42][43] However, these factors and mechanisms are still poorly understood. Moreover, earthworm studies in contaminated areas have mainly focused on the analysis of the assimilation of TE by earthworms in artificially contaminated soils.…”

Metal mobility and toxicity of reclaimed copper smelting fly ash and smelting slag

“…Metal bioavailability tests on RCS y ash and smelting slag were tested using the Wear and Evans method, as well as the method proposed by Lindsay and Norvell. For the Wear and Evans method, 2.0 g of RCS y ash and smelting slag were placed in a 50 mL centrifuge tube and mixed with 20 mL 0.05 mol L À1 EDTA at pH 7.0, respectively, as well as shaking the suspension in an oscillating device for 1 h. For the Lindsay and Norvell method, 10 g of the RCS y ash and smelting slag were mixed in a 50 mL centrifuge tube and mixed with 20 mL 0.005 mol L À1 DTPA and 0.01 mol L À1 CaCl 2 at pH 7.3, respectively, 32,33 as well as shaking the suspension in a oscillating device for 2 h. Aer extraction, the suspensions were centrifuged at 3000 rpm for 20 min, and the suspensions were then ltered using a 0.45 mm microporous membrane and tested using ICPOES. All the tests were repeated three times, and the mean value of the three experiments was obtained without error bars in this study.…”

Advances in nutrient metabolism and emission of livestock and poultry dietary trace elements

“…mg/kg~600 mg/kg [138] 。 重金属元素改变土壤中微生物组成并影响作物生长，甚至随生物链富集造 成人和动物金属元素的慢性中毒 [139] 。土壤中锌浓度过高对微生物生长和酶活性 都造成不利影响，锌直接影响土壤的物理化学性质和导致植物发育不良，研究 显示在高锌土壤中燕麦和白芥末的生长几乎完全受到抑制 [140] 。氧化锌纳米颗粒 也因毒性作用导致土壤微环境微生物结构变异 [141] 。铜浓度小于 100 mg/kg 时菌 群丰度和多样性随铜含量增加而增加，但当铜浓度大于 500 mg/kg 时铜元素的 积累显著降低了土壤微生物的多样性并极大地影响了土壤菌群组成，重金属铜 对土壤微生物结构的影响还直接降低了土壤对抗干湿变化的能力 [142] 。土壤中铅、 镉、锌等元素积累除了降低土壤细菌菌群多样性还会影响土壤真菌的群落结构 [143] 。锌、铜、镉、铅等金属元素与土壤中软体动物之间存在相互作用改变土壤 物理化学性质 [144] 。大多数植物都是土壤中重金属元素的积累载体，各种重金属 元素通过植物生长富集威胁人类健康 [145] 。如富含镉和钴的土壤导致农作物中钴、 铅含量超标，而水稻玉米等主要粮食作物能超量蓄积铜和铬元素，食用富含铬 的主食极大地提高了人地患癌风险 [146] 。在我国和一些发展中国家，重金属污染 土壤的问题非常严重，在我国长江流域大约 37%，16%，60%和 70%的稻谷分…”