Assessment of water, soil contamination and land cover changes in Sims and Vince Bayou urban watersheds of Houston, Texas

Abstract

Intense urbanization and increased industrialization in urban and suburban watersheds result in the decrease of vegetation and increase in impermeable surfaces contributing to the decline of soil and water quality. The goal of this study is to investigate the impact of urbanization and industrialization on urban watersheds. The specific objectives are to, 1) determine nutrient and heavy metal concentrations in soil and water samples along Sims Bayou (SB) and Vince Bayou (VB), 2) analyze land cover changes over the last 3 decades in each watershed and 3) evaluate socio-economic characteristics and human health risks within these watersheds. Triplicate soil and water samples were collected from downstream, midstream, and upstream locations during the fall and spring seasons along both bayous. The samples were analyzed to determine elemental concentrations using inductive coupled plasma mass spectrometer (ICP-MS) and total carbon and nitrogen (TCN) analyzer. Landsat 5 TM and Landsat 8 OLI/TIRS images were used to derive thematic land cover maps using ERDAS Imagine v16.5 software. The elemental concentrations were interpolated to spatial maps for distribution analysis using ESRI ArcGIS-10.8 software. The chemical analysis of water samples collected from SB and VB revealed that the N, P, Cu, Ni, Pb, and Zn concentrations were found at elevated levels that can pose threat for aquatic organisms. Among soil samples, the concentrations of Cr, Cu, Ni, Pb and Zn exceeded the levels of soil background concentrations of Texas. Land cover change patterns were similar for both watersheds with high vegetative surfaces decreasing and low vegetative surfaces increasing significantly over the past three decades. Both watersheds experienced an increase in total population with SB watershed increasing 27.9% and VB watershed increasing 9.1% from 1990 to 2020. Health risk assessments revealed risks for Cd, Cr, and Ni in soil via ingestion for children under age 6 in both bayous. This research is critical in improving our understanding on the impact of natural and human activities on Houston watersheds.