Estimation of soil carbon sequestration in four urban squares of the city of Imperatriz

The presence of trees in urban squares provides a range of benefits, including improvements in users' physical and mental health, as well as offering spaces for recreation, exercise, and contact with nature. These areas also serve important socio-cultural and community cohesion roles, becoming venues for public gatherings and expressions. Environmentally, tree-lined urban squares contribute to climate change mitigation through atmospheric carbon sequestration, reduction of urban heat islands, thermal comfort, and improved air quality in surrounding areas, while also promoting urban biodiversity. In this context, the present study aimed to estimate the soil carbon stock in four urban squares located in the city of Imperatriz, Maranhão, Brazil. Soil samples were collected in triplicate at a depth of 0–20 cm. Several physical and chemical parameters of the soil were analyzed, including pH, point of zero charge (PZC), exchangeable acidity, and bulk density. Organic carbon and organic matter contents were determined using the Walkley & Black (1934) method, based on the oxidation of organic carbon with Cr⁶⁺. The organic matter content was estimated by multiplying the organic carbon content by a factor of 1.724, based on the assumption that organic matter contains 58% organic carbon. The study found that the investigated parameters did not significantly influence organic matter and carbon content. Among the sampled sites, União and Ferro de Gomar squares showed the highest soil carbon stocks under the studied conditions.