Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal.
Department of Soil Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
PLoS One. 2020 Mar 5;15(3):e0229794. doi: 10.1371/journal.pone.0229794. eCollection 2020.
In soil metal ecotoxicology research, dosing is usually performed with metal salts, followed by leaching to remove excess salinity. This process also removes some metals, affecting metal mixture ratios as different metals are removed by leaching at different rates. Consequently, alternative dosing methods must be considered for fixed ratio metal mixture research. In this study three different metal mixture dosing methods (nitrate, oxide and annealed metal dosing) were examined for metal concentrations and toxicity. In the nitrate metal dosing method leaching reduced total metal retention and was affected by soil pH and cation exchange capacity (CEC). Acidic soils 3.22 (pH 3.4, CEC 8 meq/100g) and WTRS (pH 4.6, CEC 16 meq/100g) lost more than 75 and 64% of their total metals to leaching respectively while Elora (6.7 pH, CEC 21 meq/100g) and KUBC (pH 5.6, CEC 28 meq/100g) with higher pH and CEC only lost 13.6% and 12.2% total metals respectively. Metal losses were highest for Ni, Zn and Co (46.0%, 63.7% and 48.4% metal loss respectively) whereas Pb and Cu (5.6% and 20.0% metal loss respectively) were mostly retained, affecting mixture ratios. Comparatively, oxide and annealed metal dosing which do not require leaching had higher total metal concentrations, closer to nominal doses and maintained better mixture ratios (percent of nominal concentrations for the oxide metal dosing were Pb = 109.9%, Cu = 84.6%, Ni = 101.9%, Zn = 82.3% and Co = 97.8% and for the annealed metal dosing were Pb = 81.7%, Cu = 80.3%, Ni = 100.5%, Zn = 89.2% and Co = 101.3%). Relative to their total metal concentrations, nitrate metal dosing (lowest metal concentrations) was the most toxic followed by metal oxides dosing while the annealed dosing method was generally non-toxic. Due to the lack of toxicity of the annealed metals and their higher dosing effort, metal oxides, are the most appropriate of the tested dosing methods, for fixed-ratio metal mixtures studies with soil invertebrates.
在土壤金属毒理学研究中，通常使用金属盐进行给药，然后进行浸提以去除多余的盐分。这个过程也会去除一些金属，因为不同的金属以不同的速率浸出，从而影响金属混合物的比例。因此，对于固定比例金属混合物的研究，必须考虑替代的给药方法。在这项研究中，我们研究了三种不同的金属混合物给药方法（硝酸盐、氧化物和退火金属给药），以考察金属浓度和毒性。在硝酸盐金属给药方法中，浸提会降低总金属保留量，并受土壤 pH 值和阳离子交换容量（CEC）的影响。酸性土壤（pH 值 3.4，CEC 值 8 meq/100g）和 WTRS（pH 值 4.6，CEC 值 16 meq/100g）分别损失了超过 75%和 64%的总金属，而 Elora（pH 值 6.7，CEC 值 21 meq/100g）和 KUBC（pH 值 5.6，CEC 值 28 meq/100g）的 pH 值和 CEC 值较高，仅损失了 13.6%和 12.2%的总金属。金属损失最高的是 Ni、Zn 和 Co（分别为 46.0%、63.7%和 48.4%的金属损失），而 Pb 和 Cu（分别为 5.6%和 20.0%的金属损失）则大部分被保留，从而影响了混合物的比例。相比之下，不需要浸提的氧化物和退火金属给药方法具有更高的总金属浓度，更接近名义剂量，并能更好地保持混合物的比例（氧化物金属给药的名义浓度百分比为 Pb = 109.9%、Cu = 84.6%、Ni = 101.9%、Zn = 82.3%和 Co = 97.8%，而退火金属给药的名义浓度百分比为 Pb = 81.7%、Cu = 80.3%、Ni = 100.5%、Zn = 89.2%和 Co = 101.3%）。相对于总金属浓度，硝酸盐金属给药（最低金属浓度）的毒性最大，其次是金属氧化物给药，而退火给药方法通常没有毒性。由于退火金属缺乏毒性及其较高的给药工作量，对于土壤无脊椎动物的固定比例金属混合物研究，金属氧化物是最适合的给药方法。
