Lake Limboto is one of the major lakes in Sulawesi, Indonesia. It is currently undergoing serious degradation due to population pressure. As more residential areas have been established around the lake, the sedimentation rate has increased because of the contribution of anthropogenic particles. In this study, the lithogenic and anthropogenic components in surface sediments from 17 points in the lake were studied and identified using a combination of magnetic and geochemical analyses. The results showed that although the magnetic susceptibility values in R (residential) and NR (non-residential) areas were relatively similar, the values of saturation isothermal remanent magnetization (SIRM) as well as those of SIRM/χ_LF differed significantly, implying that the magnetic characteristics of the lithogenic component (in the NR area) differ from those of the anthropogenic component (in the R area). The discrepancy between the anthropogenic and lithogenic contributions was further supported by trace metals and rare earth element (REE) contents. Sediment samples in the R area contained higher levels of Mn, La, Pr, and Gd, while in the NR area they contained higher levels of Fe, Sc, Nd, and Ce. The magnetic susceptibility also correlated strongly with Fe, Cu, Zn, and Mn contents in the NR area. A similar correlation was not observed in the R area. The results above imply that a combination of magnetic and geochemical analyses can successfully differentiate lithogenic and anthropogenic components or contributions in lake sediments.

The Citarum River has a volcanic catchment area in West Java Province, and is one of the nationally strategic rivers in tropical Indonesia due to its roles in water supply and in power generation. The river is economically important, but it is also polluted by industrial, agricultural, and residential wastes. Suspended sediment samples were collected along a certain section of the Citarum River, starting in Balekambang through the area of Bandung Regency to the downstream village of Nanjung, where the river is dammed. Similar samples were also collected from seven tributaries of the Citarum River. Magnetic and heavy metal analyses show that unlike river sediments from a non-volcanic catchment area in temperate climates, magnetic susceptibility values tend to decrease downstream, showing that the magnetic minerals in the upstream area are mostly lithogenic in origin, containing more Fe-bearing minerals compared to those in tributary samples which are anthropogenic in origin. Anthropogenic pollution is also represented by the increase of Zn content along the river. The results suggest that applying magnetic methods for monitoring river pollution in the tropics or in the volcanic areas should be carefully analyzed and interpreted.

Kalimantan Selatan is proud of the Martapura River's natural and cultural history. Martapura tributaries include Riam Kanan and Kiwa. The Martapura River is essential because it provides clean water and a livelihood for riverside residents. Human-caused river pollution grows with population density (also known as anthropogenic pollutants). This study characterizes surface sediment magnetic characteristics and heavy metal contents along the Riam Kanan, Riam Kiwa, and Martapura rivers. The purpose of this research is to evaluate the magnetic signal with respect to heavy metal contents found in surface sediments taken from rivers and to confirm the use of the rock magnetism method in environmental studies in the study area. Surface sediment samples were gathered and tested for magnetic, heavy metal, and mineralogical content. According to the findings, the pseudo-single domain (PSD) magnetite mineral predominates among the magnetic minerals that can be found in the surface sediments of the rivers Riam Kanan, Riam Kiwa, and Martapura. This substantially greater grain size may be due to magnetic particles produced by erosion along the river banks. The mass-specific magnetic susceptibility of surface sediments ranges from 103.11 to 1403.64 × 10⁻⁸ m³/kg, with an average value of 355.67 × 10⁻⁸ m³/kg due to the peatland environment. Magnetic susceptibility strongly negatively correlates with heavy contents like Cu, Zn, and Hg, according to Pearson correlation analysis. Due to this correlation, magnetic susceptibility may indicate heavy metal pollution in certain rivers. This current study demonstrates the novelty of the relationship between magnetic susceptibility and the contents of heavy metals in surface sediments from rivers in peatland and tropical environments by illustrating how the relationship affects the magnetic susceptibility of the sediments.

Rock magnetic studies often require analysing extracted magnetic grains so that the mineralogy, granulometry, and concentration of magnetic minerals could be determined accurately. Magnetic extraction is often cumbersome, tedious, and subjective as this process is carried out manually by placing strong magnet inside sediment slurries. Moreover, the magnetic mineral content in sediment is generally much less than 1% of its weight. In this study, the effectiveness of mechanical magnetic extraction using magnetic stirrer is tested for riverine and lacustrine sediments. The samples are sediments from Citarum River in West Java and from Brantas River in East Java as well as surface sediment from Lake Towuti in South Sulawesi. The effectiveness tests were carried out by comparing the magnetic properties of bulk samples with that of extracted magnetic grains. Additional tests were also carried out in the form of SEM (scanning electron microscopy) and XRD (X-Ray diffraction) analyses. Apart from the expected higher values of mass-specific magnetic susceptibility, the extracted samples also tend to have larger magnetic grains than that of bulk samples. The predominant magnetic mineral in bulk and extracted samples is magnetite, although other type of magnetic minerals might be present in extracted samples. The presence of SP (superparamagnetic) grains in extracted samples is also negligible unlike that in bulk samples. SEM and XRD analyses support these findings. Magnetite grains could easily be identified in extracted samples.

Landasan Ulin is a center for vegetable production, and it has an important role in producing vegetables for the city of Banjarbaru. Agricultural soil in this study was assessed for heavy metal contamination using the geoaccumulation index (Igeo), contamination factor (Cfi), the degree of contamination (Cd), the degree of modified contamination (mCd), and the Pollution Load Index (PLI) as well as magnetic susceptibility. Samples were collected from topsoil and analyzed using magnetic susceptibility and Atomic Absorption Spectrophotometer (AAS). The average concentration of heavy metals in the sampling area A is Fe>Zn>Mn>Cu>Hg, and the area B is Fe>Mn>Zn>Cu>Hg. Magnetic susceptibility values in area A is higher than in area B and the value of magnetic susceptibility can be used as a proxy for monitoring heavy metal concentrations, especially Zn in this area. Zn and Cu exceeded the threshold set by the Indonesian Standards Institute. Igeo results show that the research area is moderately contaminated with Cu, Zn, and Hg. According to Cfi, the soil was classified as low contaminated with Fe, Zn, Cu, Mn, and Hg, as well as Cd and mCd. The PLI results show that in both area, drastic corrective action is not required.