LEAD CONTAMINATION AND BEHAVIOR IN SOIL OF UNSATURATED ZONE, YOGYAKARTA CITY AND SURROUNDING AREA, INDONESIA

AUNG ZAW AYE, SAW , Dr. Ir. Heru Hendrayana

2016 | Disertasi | S3 Teknik Geologi

Kota Yogyakarta terletak di Jawa Tengah berada di lereng Gunung Merapi. Pertumbuhan urbanisasi dan pembangunan perkotaan di Kota Yogyakarta terus meningkat dengan aktivitas manusia. Kontaminasi Timbal (Pb) dapat terjadi pada tanah di kota Yogyakarta. Kontaminasi timbal dapat berasal dari sumber-sumber alam atau sumber antropogenik. Tujuan dari penelitian ini adalah untuk menentukan konsentrasi timbal dalam tanah dari zona tak jenuh di kota Yogyakarta, untuk mengidentifikasi fraksi geokimia dan perilaku timbal dalam tanah zona tak jenuh dan untuk menentukan sumber kontaminasi timbal di tanah zona tak jenuh yang berkaitan dengan sumber daya alam atau sumber antropogenik. Sampel tanah permukaan dikumpulkan di lereng selatan Gunung Merapi dari dekat Merapi puncak ke kota Yogyakarta. Sampel tanah di zona tak jenuh dikumpulkan melalui pengeboran lubang bor di tiga lokasi di kota Yogyakarta seperti Catur Tunggal, Mantrijeron dan Kotagede. Mineralogi dan kimia komposisi tanah ditandai dengan XRD dan XRF analisis. Konsentrasi timbal dilakukan melalui pengujian pencucian, dan fraksi geokimia dilakukan melalui pengujian ekstraksi berurutan. Sumber kontaminasi timbal diidentifikasi melalui fraksi geokimia timbal dalam tanah alami dan zona tak jenuh di daerah perkotaan. Plagioklas, hornblende, kuarsa, augit dan kalsit dominan pada sampel tanah. Plagioklas, haloisit, illite, smektit dan kalsit terdapat dalam sampel fraksi liat. Didominasi oleh SiO2 dan diikuti oleh Al2O3, Fe2O3 dan unsur-unsur lainnya termasuk dalam jumlah kecil di tanah daerah penelitian. Tanah di daerah penelitian mungkin telah mengalami tingkat pelapukan kimia rendah sampai sedang. Konsentrasi rata-rata timbal di permukaan tanah masing-masing adalah 9,96 ppm di daerah perkotaan, 3.02 ppm di daerah Pakem dan 2,42 di daerah Merapi. Konsentrasi timbal dalam tanah permukaan di daerah perkotaan adalah tiga kali lebih tinggi dari daerah Pakem dan Merapi. Terjadi potensi kontaminasi timbal di kota Yogyakarta. Konsentrasi rata-rata timbal di zona tak jenuh di daerah perkotaan adalah (9,82 ppm) di Kotagede, (6.52 ppm) di Mantrijeron dan (3.00ppm) di Caturtunggal. Konsentrasi timbal ditemukan nilai tertinggi di Kotagede (perkotaan tua) dan diikuti oleh Mantrijeron (urban muda) dan Caturtunggal (urban baru). Dari hasil fraksi geokimia, timbal utamanya diserap oleh oksida besi. Kandungan timbal dalam fraksi oksida besi di daerah perkotaan lebih tinggi dari daerah Pakem dan wilayah Merapi. Konsentrasi timbal dalam fraksi non-residual lebih dari 80% dalam tanah jenuh perkotaan dan tanah Pakem. Hal ini menunjukkan bahwa Timbal berasal dari sumber antropogenik. Sebaliknya, fraksi residual timah di tanah alami Merapi adalah sekitar 50%. Timbal di tanah Merapi berasal dari sumber alami. Konsentrasi tinggi timbal dalam tanah perkotaan sangat dipengaruhi oleh aktivitas antropogenik. Timbal memiliki bioavailable yang rendah di zona tak jenuh di daerah perkotaan karena Timbal terkonsentrasi tinggi di bagian oksida besi. Perilaku timbal di zona tak jenuh secara kimia dikendalikan oleh oksida besi melalui nilai pH. Kemungkinan sumber timbal terkontaminasi tidak hanya dari emisi lalu lintas dari hasil pembakaran bahan bakar tetapi juga dari pembuangan rumah penduduk, industri domestik, dll. Menurut hubungan konsentrasi timbal, kepadatan penduduk dan usia pembangunan perkotaan, sumber kontaminasi timbal di daerah zona jenuh tidak berhubungan langsung dengan kepadatan penduduk tetapi berhubungan langsung dengan usia pembangunan perkotaan. Di kota Yogyakarta, Konsentrasi timbal adalah yang tertinggi di Kotagede (tua perkotaan), dan diikuti oleh Mantrijeron (muda urban) dan Caturtunggal (urban baru).

Yogyakarta city is located in Central Java on the base of Merapi volcano slope. The growth of urbanization and urban development in Yogyakarta City is still increasing with human activities. Lead (Pb) contamination can be occurred in soil in Yogyakarta city. Lead contamination can be derived from natural sources or anthropogenic sources. The objective of the research is to determine the concentration of lead in soil of unsaturated zone in Yogyakarta city, to identify the geochemical fraction and behavior of lead in soil of unsaturated zone and to determine the source of lead contamination in soil of unsaturated zone which is related to natural sources or anthropogenic source. Surface soil samples were collected on the southern slope of Merapi volcano from near Merapi peak to Yogyakarta city. Soil samples in unsaturated zone were collected by borehole drilling at three locations in Yogyakarta city such as Caturtunggal, Mantrijeron and Kotagede. Mineralogy and chemical composition of soil was characterized by XRD and XRF analysis. The concentration of lead was conducted by leaching experiment and the geochemical fraction was carried out by sequential extraction experiment. The source of lead contamination was identified by the geochemical fraction of lead in natural soil and unsaturated zone in urban area. Plagioclase, hornblende, quartz, augite and calcite are dominant in bulk sample of soil. Plagioclase, halloysite, illite, smectite and calcite are composed in clay fraction sample of soil. SiO2 is dominant and it is followed by Al2O3, Fe2O3 and the other elements include in small amount in soil of the study area. Soil in the study area may have been subjected to a low to moderate degree of chemical weathering. The average concentration of lead in the surface soil is 9.96 ppm in urban area, 3.02 ppm in Pakem area and 2.42 in Merapi area respectively. Lead concentration in the surface soil in urban area is three times higher than Pakem and Merapi area. The potential contamination of lead is occurred in Yogyakarta city. The average concentration of lead in unsaturated zone in urban area is (9.82 ppm) in Kotagede, (6.52 ppm) in Mantrijeron and (3.00ppm) in Caturtunggal. Lead concentration is found the highest value in Kotagede (old urban) and it is followed by Mantrijeron (young urban) and Caturtunggal (new urban). From the result of geochemical fractions, lead is mainly adsorbed by iron oxide. Lead content in iron oxide fraction in urban area is higher than Pakem area and Merapi area. Lead concentration in non-residual fraction is more than 80% in urban unsaturated soil and Pakem soil. It indicates that Lead is originated from anthropogenic sources. In contrast, the residual fraction of lead in Merapi natural soil is about 50%. Lead in Merapi soil is originated from natural sources. The high concentration of lead in urban soil is highly influenced by anthropogenic activities. Lead is poorly bioavailable in unsaturated zone in urban area because Lead is high concentrated in iron oxide fraction. The behavior of lead in unsaturated zone is chemically controlled by iron oxide with respect ot pH value. The possible source of lead is contaminated not only from traffic emission of fuel combustion but also from discharge of resident house, domestic industries, etc. According to the relationship of lead concentration, population density and age of urban development, lead contamination in the unsaturated zone is not directly related to population density but it directly related to the age of urban development. In Yogyakarta city, lead concentration is the highest in Kotagede (old urban), and followed by Mantrijeron (young urban) and Caturtunggal (new urban).

Kata Kunci : Lead contamination, behavior, unsaturated zone, geochemical fraction, Yogyakarta city