MERCURY IN THE SEDIMENT OF THE UPPER PARNAÍBA RIVER

ABSTRACT The contamination of aquatic environments with chemical trace elements can be evaluated by their accumulation in sediments of the water body. Studies on mercury require the use of exclusive extraction techniques that have relatively high costs when compared to the analysis of other trace elements. This study was conducted aiming at determining the mercury concentration in sediments of the Upper Parnaíba River basin, located in a region of agricultural expansion between the states of Piauí and Maranhão. The sediment was collected at 12 sites in the basin. After drying, the quantification of total mercury was performed by the Zeeman atomic absorption spectrometry coupled to a pyrolysis reactor. Mercury concentrations in sediments of the Parnaíba River ranged from 4.2 to 58.5 ng g−1 and presented a low probability of adverse effects on biota. Mercury had no correlation with the variables clay, silt, sand, total organic carbon, iron, and aluminum, demonstrating its possible anthropogenic origin. Although mercury concentrations have a low probability to disturb the balance of the local ecosystem, there is a need for monitoring the region in order to quantify the risks to biota and human health.

摘要 化学微量元素在水体沉积物中的累积情况，可用于评估水生环境的污染程度。相较于其他微量元素的分析检测，汞的相关研究需采用专属萃取技术，此类技术的成本相对较高。本研究旨在测定位于巴西皮奥伊州与马拉尼昂州之间农业扩张区域的上帕尔纳伊巴河流域沉积物中的汞浓度。研究于该流域内的12个采样点采集沉积物样品，样品经干燥处理后，采用耦合热解反应器（pyrolysis reactor）的塞曼原子吸收光谱法（Zeeman atomic absorption spectrometry）对总汞进行定量分析。结果显示，帕尔纳伊巴河流域沉积物中的汞浓度范围为4.2至58.5纳克每克，对水生生物群落产生不利影响的概率较低。汞浓度与黏土、粉砂、砂粒、总有机碳、铁及铝等环境变量均无显著相关性，表明其可能为人为来源。尽管当前汞浓度对当地生态系统平衡造成干扰的概率较低，但仍需对该区域开展持续监测，以量化其对生物群落及人类健康的潜在风险。