Lhr's Ph.D. study was part of a larger project on the Ijen Crater Lake on East Java, Indonesia. This crater lake is the largest collection of volcanic water in the world and is extremely acidic (pH 0.1). The acidic water slowly seeps away, and despite dilution by two tributaries in the area the pH of the river water remains very low. This water is used for agricultural and household purposes, which sometimes leads to the rice harvests failing. The very high aluminium content of the water associated with the acidity also plays an important role in this. Other elements such as fluorine, in the form of fluoride, form a direct threat for public health. The levels are not only alarmingly high in the river water but also in the groundwater and drinking water wells.
Within the large project scientists studied the geochemical and hydrological processes as well as the health risks. Ansje Lhr investigated the ecological effects of the acidic water. As well as having a harmful effect on the well-being of the local population, it adversely affects the biodiversity.
Lhr sampled the water at various locations. She observed that the neutral river water contained normal aquatic fauna, but that only mosquito larvae could survive the extremely acidic water. The diversity of microorganisms and algae was also very low. The inhibited breakdown of organic material was another ecological effect measured. Lhr established this using packs containing jati and bamboo leaves, which she suspended in the river at various locations. She determined the loss dry matter over a period of several months.
Contact: Ansje Lhr
Netherlands Organization for Scientific Research