State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing, 100875, China.
Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China.
Environ Sci Pollut Res Int. 2020 Mar;27(8):8082-8090. doi: 10.1007/s11356-019-07518-4. Epub 2020 Jan 2.
To understand the potential environmental influence of animal manure under freeze-thaw cycles, pig manure was used to conduct a simulation experiment to explore the effects of freeze-thaw cycles on heavy metal distribution and form transformation. Thirty cycles of freezing and thawing were performed alternately by freezing at - 18 ± 2 °C for 24 h and thawing at 20 ± 2 °C for 24 h. By a serial wet sieving procedure, manure samples were separated into different sizes of 1000, 250, 75, 38, and < 38 μm. Solid samples were collected from the dry matter at each stage of sieve; then the washing waters were collected as liquid samples accordingly. The concentrations of heavy metals in solid/liquid samples and their five forms were analyzed. It showed that the concentrations of heavy metals in the solid and liquid samples gradually increased because of organic matter degradation during freezing and thawing cycles. The distribution of heavy metals on particles of different sizes was also affected by the degradation and breakup of pig manure; the metals showed a tendency to aggregate in small particles (< 38 μm). Among them, the percentage of Cu and Zn on < 38 μm particles increased by 162.3% and 554.1%, respectively. After several freeze-thaw cycles, the concentrations of EXCH-X (metals of exchangeable form) increased significantly, those of CARB-X (carbonate-bound form) and Fe/Mn-X (Fe/Mn oxide-bound form) decreased accordingly. These form transformations may be largely influenced by the enhancement of dissolved organic matter (DOM) and the reduction of pH value. Therefore, frequent freeze-thaw cycles may promote the mobility and bioavailability of heavy metals in pig manure. The results are significant for understanding the pollution risk of pig manure in the freeze-thaw regions.
为了了解动物粪便在冻融循环下的潜在环境影响，采用猪粪进行模拟实验，探讨了冻融循环对重金属分布和形态转化的影响。通过交替进行 30 个冻融循环，将猪粪在-18±2°C下冷冻 24 小时，然后在 20±2°C下解冻 24 小时。通过连续的湿筛程序，将粪便样品分离成不同大小的 1000、250、75、38 和 <38 μm。从每个筛阶段的干物质中收集固体样品；然后相应地收集洗涤水作为液体样品。分析了固体/液体样品中重金属的浓度及其五种形态。结果表明，由于冻融循环过程中有机物的降解，固体和液体样品中重金属的浓度逐渐增加。重金属在不同粒径颗粒上的分布也受到猪粪降解和破碎的影响；金属有在小颗粒(<38 μm)中聚集的趋势。其中，Cu 和 Zn 在<38 μm 颗粒上的百分比分别增加了 162.3%和 554.1%。经过几次冻融循环后，EXCH-X（可交换态）的浓度显著增加，CARB-X（碳酸盐结合态）和 Fe/Mn-X（Fe/Mn 氧化物结合态）的浓度相应降低。这些形态转化可能主要受到溶解有机质（DOM）增强和 pH 值降低的影响。因此，频繁的冻融循环可能会促进猪粪中重金属的迁移性和生物可利用性。这些结果对于了解冻融区猪粪的污染风险具有重要意义。
