Heavy Metal Risk Assessment from Agriculture in Shallow Tropical Karst Lake, Gunungsewu Karst Area, Java Island, Indonesia

This research investigates the heavy metal pollution in karst lakes, crucial for fisheries, agriculture, and domestic activities. Target metals include Pb, Cd, Cr, Fe, Zn, and Cu. Objectives comprise assessing pollution levels via the Heavy Metal Pollution Index (HPI) and conducting an ecological risk assessment, incorporating the Enrichment Factor, Geoaccumulation Index, and Ecological Risk Index. The Pearson’s correlation and cluster analysis were performed to analyze the connection between samples. Results reveal strong correlations between metals in soil and sediment, such as Pb in soil correlating with Cu in sediment (r = 0.88), Zn in soil with Cu in sediment (r = 0.75), and Zn in soil with Pb in sediment (r = 0.81). Kedokan Lake emerges as the most representative observation (distance 13.1), while Kepleng Lake is the least representative (distance 535). Cluster analysis identifies two distinct clusters: Cluster 1 encompasses Ngrejek Lake, Kedokan Lake, Sodong Lake, Kanigoro Lake, and Ngampelombo Lake. HPI calculations reveal varying contamination levels in lake water and underground river samples within the Bribin Underground River Catchment Area. Notably, one location in Kedokan Lake is categorized as contaminated (HPI value of 188.05). Mean Enrichment Factor values range from no enrichment factor (<1) to low enrichment factor (1–3). Geoaccumulation Index (Igeo) indicates an overall unpolluted classification (Igeo<0) across all sampling sites. These findings underscore the nuanced pollution status in the studied area, emphasizing the importance of continued monitoring and intervention to ensure the sustainability of karst lakes in the face of heavy metal contamination.