High-Frequency Monitoring of Suspended Sediment Variations for Water Quality Evaluation at Deep Bay, Pearl River Estuary, China: Influence Factors and Implications for Sampling Strategy

Abstract

Suspended sediment (SS) is an important water quality indicator of coastal and estuarine ecosystems. Field measurement and satellite remote sensing are the most common approaches for water quality monitoring. However, the efficiency and precision of both methods are typically affected by their sampling strategy (time and interval), especially in highly dynamic coastal and estuarine waters, because only limited measurements are available to analyze the short-term variations or the long-term trends of SS. Dramatic variations of SS were observed, with standard deviation coefficients of 48.9% and 54.1%, at two fixed stations in Deep Bay, China. Therefore, it is crucial to resolve the temporal variations of SS and its main influencing factors, and thus to develop an improved sampling strategy for estuarine ecosystems. Based on two years of continuous high-frequency measurements of SS and concurrent tidal and meteorological data, we demonstrated that the tide is the dominant factor influencing the SS variation among tide, wind (speed and direction), and rainfall in Deep Bay, China. For the monitoring of maximum suspended sediment concentration (SSC), the recommended optimum sampling time coincides with the occurrence of the ebb tides, whereas multiple sampling times are recommended for monitoring of minimum SSC. Although variations of SS are also affected by other factors, the recommended sampling strategy could capture the maximum and minimum SSC variations exactly more than 85% days in a year on average in Deep Bay. This study provides a baseline of SS variation and direct sampling strategy guidance for future SS monitoring and could be extended to other coastal or estuarine waters with similar climatological/tidal exposures.

An Unstructured-Grid Based Morphodynamic Model for Sandbar Simulation in the Modaomen Estuary, China

“…So it can be concluded that the tide is the dominant factor influencing the variation of suspended sediment concentration. Similar results were found in Deep Bay, Pearl River Estuary, China [30]. Besides, the diffusion phenomenon of suspended load is well reproduced in Figure 9.…”

Assessing the Potential of Geostationary Himawari-8 for Mapping Surface Total Suspended Solids and Its Diurnal Changes

“…This study examines the potential of the AHI sensor for monitoring the coastal surface TSS, as the AHI sensor is deployed with suitable wavebands of visible, Near Infrared (NIR) and Shortwave Infrared (SWIR), and high temporal resolution (every 10 min). The Pearl River Estuary (PRE) and neighboring coastal waters were selected, showing relatively strong daily sedimentary and runoff variations [33]. Additionally, the marine ecosystem adjacent to the PRE is disturbed by the problem of sediment and effluent runoff from rapid industrial and urban development [34]; high-frequency mapping of TSS is, thus, critical for monitoring the coastal ecosystem.…”

Assessment of Water Quality Evolution in the Pearl River Estuary (South Guangzhou) from 2008 to 2017

“…In estuaries, flood and ebb tides normally lead to the mixing of inland riverine water with seawater from the surrounding bay as well as the surface and bottom water [31,32]. In our study, the concentrations of F. Coli and physiochemical parameters in the surface and bottom water were generally consistent during flood and ebb tides ( Figure 2), suggesting that the effect of tides on hydrological exchange in the sampling sites was very weak.…”