Phosphorus Loss through Overland Flow and Interflow from Bare Weathered Granite Slopes in Southeast China

Deng Deng,Fei Fei,Zhang Zhang,Ni Ni,Fan Fan,Sun Sun

doi:10.3390/su11174644

Deng Deng, Fei Fei + Show 4 more

Open Access

https://doi.org/10.3390/su11174644

Copy DOI

Abstract

Phosphorus (P) is the key limiting factor for eutrophication, and the mechanism of P loss from hillslopes is complex. Few attempts have been made to study the processes of P loss through overland flow and interflow from bare weathered granite slopes in Southeast China. Therefore, artificial rainfall simulations were performed to evaluate P loss from bare weathered granite slopes with different slope angles (5°, 8°, 15°, 25°) and different rainfall intensities (1.5, 2.0, 2.5 mm/min). The results show that overland flow increased with rainfall intensity, while it declined with slope angle. Interflow exhibited a single-peak curve with time of runoff. The interflow accounted for 28.53–89.12% of the total runoff yield, and the percentage declined with rainfall intensity and increased with slope angle. Both total phosphorus (TP) concentration (CTP) and TP load (LTP) in overland flow increased with rainfall intensity, and the percentages of LTP in each rainfall event ranged from 51% to 92%. CTP in overland flow distinctly fluctuated, with the maximum appearing on the 25° slope, while the maximum in interflow was observed on the 5° slope. LTP in overland flow was the highest on the 8° slope, and was significantly affected by runoff yield and rainfall intensity (p < 0.01). LTP in interflow was small and was significantly affected by rainfall intensity (p < 0.01). Runoff P was mainly lost through overland flow, dominantly in the form of particulate phosphorus (PP), and P loss through interflow was an important supplementation, mainly in the form of dissolved phosphorus (DP). These results provide underlying insights and scientific background for the control of P loss in bare weathered granite areas.

Highlights

Non-point source (NPS) agricultural pollution is currently a major environmental problem that brings potential harm to human and environmental health [1,2]
Overland flow decreased with increasing slope angle, the maximum value being reached on the 8◦ slopes when rainfall intensity was uniform
The maximum interflow declined with rainfall intensity on the 5◦ and 8◦ slopes, while it displayed an opposite trend on the 15◦ and 25◦ slopes

Summary

Introduction

Non-point source (NPS) agricultural pollution is currently a major environmental problem that brings potential harm to human and environmental health [1,2]. Many studies have shown that NPS agricultural pollution is the main reason for eutrophication of water bodies [3]. Mechanisms of nutrient loss from the bare weathered granite slopes need to be further studied. The slopes with weathered granite have a wide distribution area in Southeast China. The area is one of the typical representatives of the most serious eroded slopes in the red soil hills, forming a large-scale degraded ecosystem [11,12]. Field nutrients from the slopes enter the receiving water bodies mainly through overland flow and interflow. There are many studies about runoff and nutrient loss from slopes with loess, red and purple soils in China. Few studies have investigated nutrient loss by interflow from bare weathered granite slopes. The migration of nutrients via downward seepage flow is closely related to soil properties because it is affected by the physical structure of soil and the characteristics of rainfall infiltration [17,18]

Objectives

Methods

Results

Conclusion