Analisis Kimiawi Air Tanah Akibat Pemompaan Berlebih di Cilincing-Koja-Kelapa Gading, Jakarta Utara

Abstract

ABSTRAK

Masyarakat Kawasan Cilincing-Koja-Kelapa Gading menggunakan air tanah hanya untuk mandi-cuci-kakus (MCK) saja, sedangkan untuk makan-minum membeli air galon (40 liter) untuk dua hari. Penelitian ini untuk mengetahui penyebab air tanah tidak digunakan untuk kebutuhan sehari-hari. Metode yang digunakan di antaranya pemetaan muka air tanah (MAT) sumur gali/pantek, pengambilan contoh air, pengukuran sifat fisik air tanah dan analisis kimiawi air tanah. Sebaran MAT menghasilkan cone of depression (Kelapa Gading Utara). Ini menunjukkan telah terjadi pengambilan air tanah berlebih menggunakan mesin pompa. Fasies ion dominan (70%) HCO3 + SO4 /Cl pada 7 lokasi fasies Cl + SO4 (30%) di 3 lokasi dan ion logam yang dikaji hanya ion Mn menggunakan baku mutu PerMenKes No 492/MEN.KES/PER/IV/2010. Salinitas mengacu kadar TDS umumnya masuk kategori tawar (<1.000 mg/l), dan 3 lokasi kategori payau (1.000-10.000 mg/l). Analisis konsentrasi Cl pada 5 lokasi masuk kategori payau (100-1.000 mg/l), 3 lokasi kategori asin Cl >1.000 mg/l yaitu 2 lokasi Barat dan 1 lokasi Timur dan hanya 2 lokasi masuk kategori tawar (Cl <100 mg/l) terletak di bagian tengah serta utara. Air tanah fasies awal NaK-HCO3 mengalir ke arah selatan terjadi perubahan menjadi fasies NaK-Cl. Beberapa lokasi mempunyai kandungan ion Mn telah melampaui baku mutu di antaranya Mn; 3 lokasi di Barat dan 1 lokasi di Timur, sedangkan lokasi lainnya masih di bawah baku mutu yang disyaratkan. Lokasi Kelapa Gading Utara dan Marunda mempunyai kadar TDS (<500 mg/l) dan Klorida/Cl (<100 mg/l) yang digunakan masyarakat sebagai sumber air baku untuk makan-minum, karena rasa air tanahnya tawar. Sedangkan lokasi air tanah (SG/SP) lainnya, tidak dapat digunakan masyarakat sebagai air baku untuk makan-minum, karena tingginya nilai TDS di atas normal berkisar 500 - 4020 mg/l yang mempunyai rasa air payau hingga asin.

Kata kunci: air tanah, fasies hidrokimia, Jakarta Utara, kimiawi air tanah, muka air tanah, TDS

ABSTRACT

People of the Cilincing-Koja-Kelapa Gading area use groundwater only for bathing-washing-toilet, while for eating and drinking they buy water gallon (40 litres) for 2 days. This study is to determine the cause of groundwater not being used for daily needs. The methods used include mapping the groundwater level of dug wells, taking water samples, measuring the physical properties of groundwater and chemical analysis of groundwater. The distribution of groundwater levels shows a cone of depression (North Kelapa Gading). This indicates that there has been excess groundwater extraction using a pump machine. Dominant ion facies (70%), HCO3 + SO4 / Cl at 7 locations Cl + SO4 facies (30%) in 3 locations and only metal ions studied were Mn ions using the quality standard of PerMenKes No 492/MEN.KES/PER/IV/2010. Salinity refers to the levels of TDS, generally are in the fresh category (<1,000 mg / l), and 3 locations in the brackish category (1,000 - 10,000 mg / l). Analysis of chloride / Cl concentrations at 5 locations are in the brackish category (100 - 1,000 mg / l), 3 locations in the salty category of Cl> 1,000 mg / l, which are 2 locations in the West and 1 in the East and only 2 locations in the fresh category (Cl <100 mg / l) which are located in the Central and North. The initial NaK - HCO3 facies groundwater flows to the South and changes to NaK - Cl facies. Several locations that contain Mn ions have exceeded the quality standard, including Mn; 3 locations in the West and 1 location in the East, while the other locations are still below the required quality standard. The locations of Kelapa Gading Utara and Marunda have levels of TDS (<500 mg/l) and chloride/Cl (<100 mg/l) which are used by the community as a source of raw water for food and drink because the groundwater tastes fresh. Meanwhile, other groundwater (SG/SP) locations cannot be used by the community as raw water for food and drink, because the high TDS value above normal ranges from 500 - 4020 mg/l, which has a brackish to salty taste.

Keywords: groundwater, chemical facies, North Jakarta, chemical groundwater, groundwater level, TDS