Evaluation of occurrence of NO3–, Coliform and atrazine in a karst aquifer, Colombo, PR

ABSTRACT The vulnerability of karst aquifers to contamination by agrochemical compounds was studied. Such contamination occurs due to its geomorphological structure. Despite the fact, aquifers are important to provide potable water, there is a lack of research about karst aquifers in Brazil. The aim of this study was to evaluate the occurrence of nitrates, fecal coliform bacteria and atrazine in shallow and deep wells in the karst aquifer in the State of Paraná, which is affected by agricultural activities. This study was conducted in an intensive agricultural area located inside the basin of the Upper Iguassu/Ribeira in the Municipality of Colombo, Paraná in Brazil. The sampling campaigns were carried out between 2014 and 2015 in fifteen shallow wells and seven deep wells. Nitrates, total and fecal coliforms and atrazine were analyzed. Nitrates were found in higher concentration in all shallow wells, ranging from 0.14 mg L-1 and 40.22 mg L-1. In deep wells, the lower concentrations were between 1.24 mg L-1 e 17.86 mg L-1. The analysis of total and fecal coliforms showed the bias for nitrates. Atrazine was detected in five shallow wells and in four deep wells. Physico-chemical characteristics of atrazine as well as fractures of the karstic aquifer and high hydraulic conductivity can be considered as determining factors in the fate of pesticides.

摘要 本研究针对喀斯特含水层（karst aquifer）受农用化学品污染的脆弱性展开探讨，此类污染的发生与其地貌结构密切相关。尽管含水层是饮用水供给的重要载体，但巴西境内针对喀斯特含水层的相关研究仍较为匮乏。本研究旨在评估受农业活动影响的巴西巴拉那州喀斯特含水层中，浅井与深井内硝酸盐、粪大肠菌群（fecal coliform bacteria）及莠去津（atrazine）的检出情况。本次研究的采样区域位于巴西巴拉那州科伦坡市境内的上伊瓜苏河/里贝拉河（Upper Iguassu/Ribeira）流域内的集约化农业区。采样工作于2014年至2015年间开展，共覆盖15口浅井与7口深井。研究对硝酸盐、总大肠菌群、粪大肠菌群及莠去津进行了检测分析。所有浅井中均检出硝酸盐，浓度范围为0.14 mg·L⁻¹至40.22 mg·L⁻¹；深井内的硝酸盐浓度则介于1.24 mg·L⁻¹至17.86 mg·L⁻¹之间。总大肠菌群与粪大肠菌群的检测结果与硝酸盐污染呈现显著关联。莠去津在5口浅井与4口深井中均有检出。莠去津的理化性质、喀斯特含水层的裂隙发育特征以及高水力传导度（hydraulic conductivity），均可被视为影响农药归趋的决定性因素。