## 1 Introduction  
The construction of artificial impoundments has been on the rise over the last few decades. The construction of dams or veins results in hydrologic alteration, which impacts trophic levels, sedimentation rates, and the quantity and quality of freshwater sediments [1, 2, 3, 4]. The amount of sediments retained by impoundment structures has reached 4-5 Gt/yr, which corresponds to approximately 25-30% of the global land-ocean transfer of sediments by rivers [5]. An extensive river restoration project conducted in Korea during the period of 2010-2011 included the construction of veins and the enlargement of river channels, which led to the dredging of a large amount of benthic sediment from riverbeds and riverside floodplains.  
Sediments are important components in the study of heavy metal contamination in rivers because many contaminants and particle-reactive elements are eventually deposited in the bottom sediment [6, 7]. Trace metals may reach water systems from lithogenic or anthropogenic sources, such as industrial waste, fossil fuel combustion, sewage wastewater, energy production, and construction. Because trace metals are mainly adsorbed and accumulated at the bottom of the sediments, the sediments act as both a sink and source of trace metals, which may be released again into water bodies through various remobilization processes, resulting in potential environmental and human health issues [8]. Hence, sediments can be used as indicators of local pollution.  
Several analytical techniques, such as Atomic Absorption Spectrometry (AAS), X-ray fluorescence spectroscopy, and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), have been applied to the identification of trace metals in soil and sediment samples. Conventional analysis techniques and complicated sample preprocessing methods, such as fusion dissolution and microwave digestion, are costly and time-consuming. To overcome these limitations, we employed Laser-Induced Breakdown Spectroscopy (LIBS) as a fast and minimally destructive measurement technique for analyzing trace metals in sediments.  
LIBS has been used in various fields, particularly for soil analyses. The authors of [9] applied LIBS to investigate the feasibility of detecting heavy metals in sand matrices. Dry synthetic sand samples were used in the test stage for a field application. The authors of [10] quantitatively identified the total content of heavy metals in reference soil samples by comparing their results with those obtained using Inductively Coupled Plasma (ICP) spectroscopy. The authors of [11] studied a set of heavy metals, particularly chromium, in soil and sewage sludge based on a constructed calibration curve. Furthermore, multivariate statistical analysis techniques coupled with LIBS were applied to reduce spectrum noise. The authors of [12] employed principal component analysis (PCA) for the discrimination of varieties of soil. The authors of [13] tested a calibration method and scatter diagram of principal components (PCs) to extract the correlation and discriminate between soils contaminated with heavy metals (or oils) and clean soils.  
The objective of this study was to understand and evaluate heavy metal pollution in sediments by collecting surface sediments from the vicinity of weirs constructed across four rivers, considering that many potential pollutants in the sediments significantly influence the river environment. Multivariate chemometrics based on LIBS data were utilized for the determination and quantification of heavy metals in the sediments. PCA was applied to distinguish the characteristics of the sediment samples. The concentrations of heavy metals, particularly Cd, Cr, and Pb were evaluated by using the Savitzky-Golay (SG) derivative and partial least squares regression (PLSR) methods. For the stability of the measurement, starch was mixed into the sample preparation process.