Assessing Anthropogenic Impacts on Chemical and Biochemical Oxygen Demand in Different Spatial Scales with Bayesian Networks

Jing Xu,Yuming Mo,Hongwu Tang,Guangqiu Jin,Ling Li

doi:10.3390/w12010246

Abstract

In order to protect the water environment in seriously polluted basins, the impacts of anthropogenic activities (sewage outfalls and land use) on water quality should be assessed. The Bayesian network (BN) provides a convenient way to model these complex processes. In this study, anthropogenic impacts on chemical oxygen demand (COD) and biochemical oxygen demand (BOD) were evaluated in the Huaihe River basin (HRB) considering dry and wet seasons and different spatial scales. The results showed that anthropogenic activities had the most significant impacts on COD and BOD at the catchment scale. In dry seasons, sewage outfalls played an important role in organic pollution. Farmland became the most important source in wet seasons although it had a “sink” process in dry seasons. Intensive human activities in urban made significant contributions to increased COD levels. Grassland had a negative relationship with organic pollution, especially in dry seasons. Therefore, governments should implement strategies to control organic matters transported from urban and farmland regions. Increasing the efficiency of wastewater treatments and the percentage of grassland in the riparian zone could improve water quality. These results can enhance understanding of anthropogenic impacts on water quality and contribute to efficient management for river basins.

Highlights

The intensive anthropogenic disturbance degrades water quality and causes many environmental problems, such as eutrophication in rivers, hypoxic/anoxic episodes in bottom water, increased toxicity to aquatic organisms and declines in aquatic biodiversity [1,2,3]
The mean loads’ values of both chemical oxygen demand (COD) and biochemical oxygen demand (BOD) at all monitor stations were larger in wet seasons than in dry seasons
The most significant effects of land use and sewage outfalls on COD and BOD were at the catchment scale

Summary

Introduction

The intensive anthropogenic disturbance degrades water quality and causes many environmental problems, such as eutrophication in rivers, hypoxic/anoxic episodes in bottom water, increased toxicity to aquatic organisms and declines in aquatic biodiversity [1,2,3]. Water pollution has become a global environmental problem and poses severe risks to human and aquatic ecosystem health [4,5,6]. Contaminants come from both point and nonpoint sources, which are discharged into receiving water by sewage outfalls and transported to rivers by surface runoff from urban or agricultural lands, respectively [7,8]. Many influence factors are related to the complex processes between anthropogenic activities and water quality degradation. Researchers have analyzed the impacts of different human activities on water quality, such as agricultural fertilization, loss of woodland and grassland, urbanization and contaminations from

Objectives

Methods

Results

Discussion

Conclusion