Black carbon in urban soils: land use and climate drive variation at the surface

IF 3.9 3区环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Carbon Balance and Management Pub Date : 2024-03-02 DOI:10.1186/s13021-024-00255-3

Molly Burke, Erika Marín-Spiotta, Alexandra G. Ponette-González

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Abstract

Background

Black carbon (BC) encompasses a range of carbonaceous materials––including soot, char, and charcoal––derived from the incomplete combustion of fossil fuels and biomass. Urban soils can become enriched in BC due to proximity to these combustion sources. We conducted a literature review of BC in urban soils globally and found 26 studies reporting BC and total organic carbon (TOC) content collected to a maximum of 578 cm depth in urban soils across 35 cities and 10 countries. We recorded data on city, climate, and land use/land cover characteristics to examine drivers of BC content and contribution to TOC in soil.

Results

All studies were conducted in the northern hemisphere, with 68% of the data points collected in China and the United States. Surface samples (0–20 cm) accounted for 62% of samples in the dataset. Therefore, we focused our analysis on 0–10 cm and 10–20 cm depths. Urban soil BC content ranged from 0–124 mg/g (median = 3 mg/g) at 0–10 cm and from 0–53 mg/g (median = 2.8 mg/g) at 10–20 cm depth. The median proportional contribution of BC to TOC was 23% and 15% at 0–10 cm and 10–20 cm, respectively. Surface soils sampled in industrial land use and near roads had the highest BC contents and proportions, whereas samples from residential sites had among the lowest. Soil BC content decreased with mean annual soil temperature.

Conclusions

Our review indicates that BC comprises a major fraction (nearly one quarter) of the TOC in urban surface soils, yet sampling bias towards the surface could hide the potential for BC storage at depth. Land use emerged as an importer driver of soil BC contents and proportions, whereas land cover effects remain uncertain. Warmer and wetter soils were found to have lower soil BC than cooler and drier soils, differences that likely reflect soil BC loss mechanisms. Additional research on urban soil BC at depth and from diverse climates is critical to better understand the role of cities in the global carbon cycle.

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城市土壤中的黑碳：土地利用和气候驱动地表变化。

背景：黑碳（BC）包括一系列碳质材料--包括烟尘、焦炭和木炭--由化石燃料和生物质不完全燃烧产生。由于靠近这些燃烧源，城市土壤中的生物碳可能会富集。我们对全球城市土壤中的 BC 进行了文献综述，发现有 26 项研究报告了在 35 个城市和 10 个国家的城市土壤中收集到的 BC 和总有机碳 (TOC) 含量，最大深度为 578 厘米。我们记录了有关城市、气候和土地利用/土地覆盖特征的数据，以研究土壤中 BC 含量和总有机碳含量的驱动因素：结果：所有研究都在北半球进行，其中 68% 的数据点在中国和美国采集。地表样本（0-20 厘米）占数据集中样本的 62%。因此，我们将分析重点放在 0-10 厘米和 10-20 厘米的深度上。城市土壤 BC 含量在 0-10 厘米处为 0-124 毫克/克（中位数 = 3 毫克/克），在 10-20 厘米处为 0-53 毫克/克（中位数 = 2.8 毫克/克）。在 0-10 厘米和 10-20 厘米处，BC 占总有机碳比例的中位数分别为 23% 和 15%。在工业用地和道路附近采样的表层土壤中，BC 含量和比例最高，而在居民点采样的土壤中，BC 含量和比例最低。土壤中的萃取物含量随着年平均土壤温度的升高而降低：我们的研究表明，萃取物占城市表层土壤总有机碳的主要部分（近四分之一），但对表层的取样偏差可能会掩盖萃取物在深层储存的潜力。土地利用是土壤中 BC 含量和比例的输入驱动因素，而土地覆盖的影响仍不确定。与凉爽干燥的土壤相比，较温暖潮湿的土壤中的土壤萃取物含量较低，这种差异可能反映了土壤萃取物的流失机制。要想更好地了解城市在全球碳循环中的作用，就必须对不同气候条件下的城市土壤BC进行更深入的研究。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Carbon Balance and Management Environmental Science-Management, Monitoring, Policy and Law

CiteScore

7.60

自引率

0.00%

发文量

审稿时长

14 weeks

期刊介绍： Carbon Balance and Management is an open access, peer-reviewed online journal that encompasses all aspects of research aimed at developing a comprehensive policy relevant to the understanding of the global carbon cycle. The global carbon cycle involves important couplings between climate, atmospheric CO2 and the terrestrial and oceanic biospheres. The current transformation of the carbon cycle due to changes in climate and atmospheric composition is widely recognized as potentially dangerous for the biosphere and for the well-being of humankind, and therefore monitoring, understanding and predicting the evolution of the carbon cycle in the context of the whole biosphere (both terrestrial and marine) is a challenge to the scientific community. This demands interdisciplinary research and new approaches for studying geographical and temporal distributions of carbon pools and fluxes, control and feedback mechanisms of the carbon-climate system, points of intervention and windows of opportunity for managing the carbon-climate-human system. Carbon Balance and Management is a medium for researchers in the field to convey the results of their research across disciplinary boundaries. Through this dissemination of research, the journal aims to support the work of the Intergovernmental Panel for Climate Change (IPCC) and to provide governmental and non-governmental organizations with instantaneous access to continually emerging knowledge, including paradigm shifts and consensual views.