Salicylic acid determination in estuarine and riverine waters using hollow fiber liquid-phase microextraction and capillary zone electrophoresis.

A low-cost methodology using hollow fiber liquid-phase microextraction (HF-LPME) and capillary zone electrophoresis (CZE) with UV-Vis detector was developed to analyze the salicylic acid (SA) in estuarine and riverine waters. The technique is easy-to-use and rapid, and demands little volume of organic solvent. The extraction was carried out using a polypropylene membrane supporting into octan-1-ol. HF-LPME under optimized conditions (donor solution sample pH 2, acceptor solution pH 14, sample volume 25 mL, fiber length 10 cm, acceptor volume 25 µL, extraction time 3 h and stirring speed 350 rpm) presented high enrichment factor (407 times) and good recovery in real water samples (from 88 to 110%). A limit of detection of 2.6 µg L-1 was achieved using CZE with UV-Vis detector as quantification method. The method was applied to direct quantification of SA in environmental complex estuarine and riverine water matrices.

Elemental gaseous mercury flux at the water/air interface over the Negro River basin, Amazon, Brazil.

The amount of dissolved gaseous mercury (DGM) released annually into the atmosphere by water bodies in each of the 18 major sub-basins of the Negro River tributaries has been estimated for the wet season and adopted for the entire year. Using Remote Sensors (RS) and the Geographic Information System (GIS), an estimate was made for the total flooded area during the period of the wet season (May-July), which corresponds to around 10% of the total basin area. The estimates of DGM evasive flux values were made during four scientific campaigns and ranged from 0.09 to 14 mug m(-2) y(-1). Mercury wet deposition to the same area was estimated using average values of the metal concentration in the rainwater (9.8 ng L(-1)), which varies from 17 to 27 microg m(-2) year(-1). Considering the flooded area of the Negro River Basin as 69,000 km(2), the total amount of mercury emitted by all bodies of water reaches nearly 0.26 ton year(-1), which represents not more than 2% of the total mercury found in wet deposition in this same area.