Evidence of massive river pollution in the tropical megacity Jakarta as indicated by faecal steroid occurrence and the seasonal flushing out into the coastal ecosystem

In the rapidly growing coastal megacities of developing and emerging countries, the implementation of new sewage treatment facilities is often not keeping pace with the enormous population growth, leading to a deterioration of the urban water resources. Only very few studies discuss faecal water contamination in these urban areas. Our study area Jakarta, the capital of Indonesia, is such a megacity. We investigated chemical markers of faecal contamination in water and sediments from the rivers and canals flowing through Jakarta. Moreover, also the spatial distribution of faecal markers in Jakarta Bay, the coastal ecosystem that receives all urban river discharges, was assessed. The concentrations of the faecal steroid coprostanol in river water ranged from 0.45 to 24.2 µg L^?1, and in sediments from 0.3 to 400 µg g^?1, reflecting the problem of inadequate sewage treatment capacities in the city. The steroid distribution in Jakarta Bay in May 2013 as compared to dry season data indicates a flushing out of particle-associated pollutants from the urban rivers far offshore during the precedent rainy season, where the city experienced a severe flood. This flushing out of particle-associated pollutants during times of heavy rainfall as observed in our study is a pollutant transport mechanism that is important for all tropical coastal systems. The associated impacts on sensitive coastal habitats might become more severe in the future, as a consequence of the expected climate change effects on monsoon variability.     

Exceptionally high concentrations of the insect repellent N,N-diethyl-m-toluamide (DEET) in surface waters from Jakarta,Indonesia

Jakarta is a booming coastal megacity in Indonesia with over 10 million inhabitants. The rivers flowing through the city district receive enormous amounts of untreated wastewaters from households and industries and discharge high pollutant loads into Jakarta Bay. Applying a screening approach for the identification of characteristic site-specific and harmful organic contaminants, we frequently found the insect repellent N,N-diethyl-m-toluamide (DEET) in river water and seawater samples from Jakarta. The compound was previously reported as persistent aquatic contaminant in industrial countries, and we present here the first data set from a tropical megacity. Concentrations in river water and seawater from Jakarta were exceptionally high, up to 24,000 ng L^?1, and exceeded by far all published concentrations in surface waters worldwide. We explained this with massive usage of the compound, lack of wastewater treatment and low average river flow as compared to rivers in other tropical megacities. The usage and properties of DEET indicate its suitability as molecular marker of municipal wastewaters. Such markers are useful to trace emissions from specific pollution sources in aquatic systems as a basis for the investigation of related impacts. We show here that DEET is in particular useful to trace the long-range distribution of municipal wastewaters in tropical freshwater and coastal systems. This application is of great value for tracing such inputs in tropical coastal habitats which are sensitive to changing water quality like coral reefs. This assists to uncover whether specific conditions in these systems could be related to pollutant inputs from land.