Souza Claudete R, Vital Helenice, Melo Germano, Souza Cleuneide R, da Silva Nogueira Mary Lucia, Tabosa Werner Farkatt
Department of Geology, Geodynamic and Geophysics Programme, Federal University of Rio Grande do Norte, Campus UFRN, P.O. Box 1596, Natal, RN, 59072-970, Brazil,
Environ Monit Assess. 2015 Feb;187(2):18. doi: 10.1007/s10661-014-4232-5. Epub 2015 Jan 28.
Environmental monitoring studies were developed in an area located on the outer shelf in the Potiguar Basin, Brazilian equatorial margin. This tropical shelf represents a modern, highly dynamic mixed carbonate-siliciclastic system. Field sampling was carried out during 3 cruises surrounding a shallow-water exploratory well to compare sediment properties of the seafloor, including grain size, texture, mineral composition, carbonate content, and organic matter, prior to drilling with samples obtained 3 and 12 months after drilling. The sample grid used had 16 stations located along 4 radials from 50 m the well up to a distance of 500 m. Sediments were analyzed in the first 0-2 cm and 0-10 cm layers. The results show that sedimentary cover around the well is dominated by bioclastic sediments, poor to very poorly sorted. Only minor sedimentological variations occurred in the area affected by drilling operations. The most noticeable effects were observed during the second cruise, in terms of a change in grain size distribution associated to a slight increase in siliciclastic content. This impact occurred in the most surficial sediment (0-2 cm), in the radials closest to the well (50 m), and could suggest the effects of drilling. However, in the third cruise, 1 year after drilling, the sediments return to show the same characteristics as in the first cruise. These results show no significant sedimentological variations due to drilling activity and indicate that ocean dynamics in this area was high enough to recover the environment original characteristics.
环境监测研究是在巴西赤道边缘波蒂瓜尔盆地外陆架的一个区域开展的。这片热带陆架代表了一个现代的、高度动态的碳酸盐 - 硅质碎屑混合系统。在围绕一口浅水勘探井进行的3次巡航期间进行了实地采样，以比较海底沉积物的性质，包括粒度、质地、矿物成分、碳酸盐含量和有机质，采样时间为钻井前以及钻井后3个月和12个月。所使用的样本网格有16个站点，沿着从距离井口50米到500米的4条径向线分布。对沉积物的0 - 2厘米和0 - 10厘米表层进行了分析。结果表明，井口周围的沉积覆盖层以生物碎屑沉积物为主，分选性差至极差。在受钻井作业影响的区域仅出现了微小的沉积学变化。在第二次巡航期间观察到了最明显的影响，表现为粒度分布的变化以及硅质碎屑含量略有增加。这种影响发生在最表层的沉积物（0 - 2厘米）中，在距离井口最近的径向线（50米）上，这可能暗示了钻井的影响。然而，在钻井1年后的第三次巡航中，沉积物恢复到了与第一次巡航时相同的特征。这些结果表明，钻井活动没有导致显著的沉积学变化，并且表明该区域的海洋动力足够强大，能够使环境恢复到原始特征。
