Jurujuba Sound pore water and sediment Data - RJ - Brazil
Description
The Jurujuba Sound is located within Guanabara Bay (Rio de Janeiro - Brazil), this overpopulated region probably may have contributed to the accumulation of chemical compounds in the sediments by diffuse sources (the Cachoeira and Icaraí rivers). Jurujuba Sound also supports a considerable area of mussel farms. In this research two main investigation approaches had been chosen, interstitial water nutrients and mercury in the sediments. This work aims to indicate the characteristic distribution of the superficial sediment (pH, Eh, particular size, carbonate, organic matter and phosphorus, total mercury (THg) and methylmercury (MeHg)) and nutrients present in pore-water (C, N, P) along Jurujuba Sound area. . The pH and Eh were measured in-situ using a Hanna Multiparameter probe. In the laboratory, nutrients in pore-ware water were measured by the colorimetric method with a KASUAKI UV / VIS spectrometer at different wavelengths for phosphate (and total phosphorous) (880 nm), nitrate (505 nm), nitrite (540 nm), and ammonium (630 nm). The grain size analysis was determined on a laser analyzer, carbonate was performed by mass difference. Total mercury analyses were carried out by the US-EPA (1998) method 7473. 180 An aliquot of the freeze-dried sediment was placed into a controlled heating oxygenated 181 decomposition furnace of the Lumex PYRO-915 + ® accessory, that released mercury 182 vapors to the Zeeman RA-915M Lumex® Atomic Absorption Spectrophotometer which 183 recorded the concentrations. Methylmercury extraction was carried out on a 50-mg freeze-dried sample with 187 3 mL of a 25% solution (w/v) of KOH in methanol for 6 hours at 70°C. The 188 measurements of methylmercury in solution were made with the US-EPA (2001) method 189 1630 and the determination was carried out in an Atomic Fluorescence 190 Spectrophotometry coupled with a gas chromatographer (AFS-GC, MERX-M, Brooks 10 Rand Instruments® 191 ). Spatial distribution maps were produced for each parameter and a principal component analysis was carried out, to assess THg and MeHg behavior and their relationships with other parameters. The highest THg concentrations were observed in the mussel-farm area (656.1 ng g-1) and were related to fine grain size and elevated organic carbon values. High MeHg concentrations also occurred in the center of the cove, probably favored by high organic carbon content (low-energy environment). The results demonstrate high N and P concentrations in pore water, indicating the possible release of the relevant nutrient amount in the water column. The high rate of domestic effluent input (Confirmed by TOC/TN ratio) led to high nutrient levels in sediments and porewater, potential release from the bottom sea could cause fish mortality events and other toxic effects.
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Steps to reproduce
1° Step - Sampling sediment at the field (carried out with a van-veen sampler) 2° Step - Laboratory analyses processing 3° Step – Spatial distribution maps production.