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An Emerging Frontier: Metal(loid) Soil Pollution Threat Under Global Climate Change.
Environmental Toxicology and Chemistry ( IF 4.1 ) Pub Date : 2020-06-01 , DOI: 10.1002/etc.4790
Anna A Paltseva 1, 2 , Alexander Neaman 3
Affiliation  

An important topic that has received very little attention is the impact of climate change, in particular global warming, and associated extreme events, on soil pollution and metal mobility in soils. The Commission on Pollution and Health found that all forms of pollution were responsible for approximately 9 million premature deaths, or 16% of all deaths globally in 2015. Thus, pollution is becoming the world's largest environmental cause of disease and premature death (Landrigan et al. 2017). To protect health, policy‐makers and regulators must consider how global climate change may influence chemical risks to humans and develop approaches to adequately assess and manage that risk. Because legacy pollutants (e.g., mercury, lead [Pb], and chromium) persist and bioaccumulate in the environment, long‐term environmental processes related to global climate change could influence their fate and transport and change ecosystem and human exposures (Balbus et al. 2013).

Global warming leads to increased soil and atmospheric temperatures, more frequent and severe extreme events (e.g., flooding, torrential rains, wildfires, droughts, hurricanes) and, consequently, soil erosion that, in turn, causes redistribution of metal(loid)s. Wildfires increase the atmospheric loadings of chemicals that create acid rain and also remobilize metals. Flooding disperses metal(loid)s from mines and industrial areas to residential and agricultural lands (Balbus et al. 2013). Accelerated melting of arctic ice causes increased mobilization of, for instance, Pb, leading to metal bioaccumulation in marine and terrestrial animals (Balbus et al. 2013). With excessive rainfalls, more contaminants will be redistributed laterally over larger areas. Existing mobile metal(loid)s will translocate downward in a soil profile, moving to lower horizons, which might be beneficial for healthy gardening and farming in topsoil. However, groundwater may become contaminated, causing other environmental problems, for example, pollution of drinking water. It is important to model the prediction of rainfall events to identify major areas of concern as well as to monitor changes in groundwater levels.

Increased precipitation may potentially mobilize, translocate, and transform soil contaminants. Metal(loid)s are more extractable in soils with low pH. Excess rainfall may result in soil acidification, which will make metal(loid)s more soluble and available for plant or human uptake. Furthermore, fertilizers and amendments applied in farm fields and gardens will be washed away or leached out, and as a result, contaminants will not be bound to phosphates to form stable (less bioavailable) minerals in soils. The development of methods that can rapidly and reliably assess metal bioaccessibility and phytoavailability in a constantly changing environment is vital to prevent human exposure. Improvement of our basic understanding of soil physics and chemistry, especially in cities with their heterogenous pedosphere and land management, is necessary for the successful development of such methods.

Changes in climate may also impact the amounts of time humans spend indoors and outdoors, influencing exposure to both indoor and outdoor contaminants (Balbus et al. 2013). Many studies indicate that urban soils contaminated with Pb become suspended in the atmosphere in the summer and autumn when evapotranspiration is at a maximum and soils are dry. These particles then settle down elsewhere, potentially contaminating clean soils. Correlational studies show increases in blood Pb concentrations during droughty periods when soil is dry and dusty and decreases in blood Pb concentrations during rainy periods when soil is wet and dust is settled (Laidlaw et al. 2017). Rapid assessment of soil and dust pollution by metal(loid)s using portable X‐ray fluorescence (XRF) is recommended to determine soil metal concentrations, to prevent future human exposures. These XRF determinations combined with atmospheric patterns (e.g., wind direction) can be used to predict potentially contaminated areas where dust will settle.

Droughts will lead to reduced soil microbial survival, colonization, diversity, and function. When plants are stunted under drought conditions, concentrations of trace metals can be elevated in the tissues (Fritioff et al. 2005). In metal‐polluted soils, elevated CO2 levels result in increased plant‐associated microbial populations protecting these microbes from metal stress. Thus, at higher levels of CO2 in metal‐polluted soils, plant‐associated microbes can improve plant growth and metal uptake, leading, for example, to potentially contaminated agricultural produce or enhanced metal uptake by plants. Crop concentrations of metals tend to increase when soil temperatures are higher (Antoniadis and Alloway 2001); however, it is not clear whether this is due to accelerated evapotranspiration, more rapid organic matter breakdown in soil, faster release from soil particles and diffusion to roots, or some combination of several factors.

Urban areas may be an excellent venue for simulation experiments because of the urban “heat island effect,” which may be viewed as a natural long‐term climate manipulation experiment. In the case of dry seasons with a limited amount of precipitation, metals will stay in topsoil or translocate from lower horizons upward to the rhizosphere due to increased evaporation rates, thus becoming more readily available for plant uptake. The addition of phosphate fertilizers, composts, and soil amendment will not form stable (and thus less bioavailable) forms of metal(loid)s due to the lack of water content required for chemical reactions to occur. Additional research is needed to determine the effect of metal contamination on microbial biodiversity and survival rates under drought conditions in different landscapes and along an urban–rural gradient. Modeling rates of decomposition of organic matter used to form organo–mineral complexes as a remediation practice is also necessary.

The effects of climate change on soil pollution with metals (i.e., their concentrations, mobility, and distribution) have been understudied and require immediate attention to prevent future human and ecosystem damage. We recommend developing metal(loid) fate and transport models encompassing factors such as atmospheric and soil temperature, precipitation, atmospheric circulation patterns, soil chemistry, groundwater levels, and degradation pathways integrating GIS tools for visualization. We encourage studies that explicitly relate the effects of temperature on metal behavior in soils due to global warming/climate change.



中文翻译:

新兴领域:全球气候变化下的金属(类)土壤污染威胁。

很少引起关注的一个重要主题是气候变化(尤其是全球变暖)和相关极端事件对土壤污染和土壤中金属迁移率的影响。污染与健康委员会发现,各种形式的污染导致2015年约900万人过早死亡,占全球所有死亡的16%。因此,污染正成为世界上造成疾病和过早死亡的最大环境原因(Landrigan等人。  2017年)。为了保护健康,政策制定者和监管者必须考虑全球气候变化如何影响对人类的化学风险,并制定适当评估和管理该风险的方法。由于遗留污染物(例如汞,铅[Pb]和铬)在环境中持续存在和生物富集,因此与全球气候变化有关的长期环境过程可能会影响其命运和运输,并改变生态系统和人类暴露(Balbus等。  2013)。

全球变暖导致土壤和大气温度升高,发生更频繁和更严重的极端事件(例如洪水,暴雨,野火,干旱,飓风),进而造成土壤侵蚀,进而导致金属(胶体)的重新分布。野火增加了大气中化学物质的负荷,这些化学物质会产生酸雨并迁移金属。洪水将金属(胶体)从矿山和工业区散布到居民和农业用地(Balbus等人,  2013年)。北极冰层融化的加速导致铅等离子的迁移增加,从而导致海洋和陆生动物体内金属生物富集(Balbus等人,  2013年)。)。随着降雨过多,更多的污染物将在更大的区域横向分布。现有的可移动金属(金属)会在土壤剖面中向下移位,移动到较低的水平,这可能有益于健康的园艺和表土耕作。但是,地下水可能会被污染,导致其他环境问题,例如饮用水污染。对降雨事件的预测进行建模以识别主要关注区域并监控地下水位的变化非常重要。

降水增加可能会动员,迁移和转化土壤污染物。在低pH值的土壤中,金属(金属)的提取率更高。过多的降雨可能导致土壤酸化,这将使金属(胶体)更易溶解,可被植物或人类吸收。此外,用于农田和花园的肥料和改良剂将被冲走或沥滤掉,结果,污染物将不会与磷酸盐结合,从而在土壤中形成稳定的(生物利用度较低的)矿物质。能够在不断变化的环境中快速,可靠地评估金属生物利用度和植物利用度的方法的开发对于防止人体暴露至关重要。改善我们对土壤物理和化学的基本理解,尤其是在城市的土壤圈和土壤管理不均的情况下,

气候变化也可能影响人类在室内和室外度过的时间,影响室内和室外污染物的暴露(Balbus等人,  2013年)。许多研究表明,当蒸散量最大且土壤干燥时,在夏季和秋季,受铅污染的城市土壤会悬浮在大气中。这些颗粒然后沉降到其他地方,可能污染干净的土壤。相关性研究表明,在土壤干燥多尘的干旱时期,血液中Pb的浓度升高;在土壤潮湿且尘埃沉降的雨季中,血液中Pb的浓度降低(Laidlaw等人,  2017)。建议使用便携式X射线荧光(XRF)快速评估金属(土壤)对土壤和灰尘的污染,以测定土壤中的金属浓度,以防止人类未来接触。这些XRF确定值与大气模式(例如,风向)相结合可用于预测灰尘将沉积的潜在污染区域。

干旱将导致土壤微生物生存,定植,多样性和功能降低。当植物在干旱条件下发育不良时,组织中痕量金属的浓度会升高(Fritioff等,  2005)。在金属污染的土壤中,CO 2含量升高会导致植物相关的微生物种群增加,从而保护这些微生物免受金属胁迫。因此,在金属污染的土壤中较高的CO 2水平下,与植物相关的微生物可以改善植物的生长和金属的吸收,从而导致潜在的农产品污染或植物对金属的吸收增加。当土壤温度升高时,金属作物的浓度往往会增加(Antoniadis and Alloway  2001); 然而,尚不清楚这是由于加速蒸散,土壤中有机物分解更快,从土壤颗粒中释放更快,扩散到根部还是多种因素的组合。

由于城市的“热岛效应”,城市地区可能是进行模拟实验的绝佳场所,这可以看作是自然的长期气候操纵实验。在降水量有限的干旱季节,由于蒸发速率增加,金属将留在表土中或从较低的地层向上迁移到根际,因此更容易被植物吸收。由于缺乏发生化学反应所需的水分,添加磷酸盐肥料,堆肥和土壤改良剂将不会形成稳定的(因此生物利用度较低)形式的金属(胶体)形式。需要进行更多的研究来确定金属污染对不同景观以及沿城乡梯度干旱条件下微生物多样性和存活率的影响。

气候变化对金属土壤污染的影响(即金属的浓度,迁移率和分布)尚未得到充分研究,需要立即注意以防止未来对人类和生态系统的破坏。我们建议您开发包含诸如大气和土壤温度,降水,大气环流模式,土壤化学,地下水位和降解路径的因素(结合GIS工具进行可视化)的金属(类)命运和运输模型。我们鼓励开展研究,明确将温度对由于全球变暖/气候变化导致的土壤中金属行为的影响联系起来。

更新日期:2020-06-01
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