Conceptual model to analyze the effects caused by technological disaster on the physical-chemical state of the lower Doce River waters, Brazil.

Research has shown the effort to develop conceptual models that relate anthropic stressors to changes in aquatic environment state. Several of these models come from the structure Drivers, Pressures, State, Impact and Response (DPSIR), which has been used since the 1990s. However, there is a lack of conceptual models that consider in its structure the connection between the damages caused in the aquatic environment and technological disasters. This research develops a general conceptual model based on the DPSIR structure incorporating technological disasters. Based on the general conceptual model guidelines and the methodological procedure associated with it, a model was developed to assess the Lower Doce River waters' state, by considering Fundão's iron-ore dam failure scenario, which took place in November 2015, in the municipality of Mariana, state of Minas Gerais, Brazil. The relevant aspects of this adaptation of the DPSIR structure were: I) it considers the combined effect of drivers and pressures that already existed in the study area with those originated from the technological disaster; and II) the causal relationships among elements of the model were explicited through a systemic conceptual map, allowing a more holistic and integrated view of the problem. The application of the conceptual model to Doce River's scenario before the disaster allowed us to verify that a set of environmental pressures was already acting in a way to stress it, making the river vulnerable. For the post-disaster scenario, it was possible to determine that the already existing vulnerability condition, caused by urbanization, agriculture and mining, had been intensified by adding new pressures due to the tailings dam failure.