Hydrogeology Journal

, Volume 17, Issue 3, pp 735–747 | Cite as

Detecting groundwater contamination of a river in Georgia, USA using baseflow sampling

Report

Abstract

Algal blooms and fish kills were reported on a river in coastal Georgia (USA) downstream of a poultry-processing plant, prompting officials to conclude the problems resulted from overland flow associated with over-application of wastewater at the plant’s land application system (LAS). An investigation was undertaken to test the hypothesis that contaminated groundwater was also playing a significant role. Weekly samples were collected over a 12-month period along an 18 km reach of the river and key tributaries. Results showed elevated nitrogen concentrations in tributaries draining the plant and a tenfold increase in nitrate in the river between the tributary inputs. Because ammonia concentrations were low in this reach, it was concluded that nitrate was entering via groundwater discharge. Data from detailed river sampling and direct groundwater samples from springs and boreholes were used to isolate the entry point of the contaminant plume. Analysis showed two separate plumes, one associated with the plant’s unlined wastewater lagoon and another with its LAS spray fields. The continuous discharge of contaminated groundwater during summer low-flow conditions was found to have a more profound impact on river-water quality than periodic inputs by overland flow and tributary runoff.

Keywords

Contamination Groundwater/surface-water relations Nitrate Waste disposal USA 

Détection de la pollution par la nappe d’une rivière en Géorgie, USA mettant en œuvre l’échantillonnage de l’écoulement de base

Résumé

Des proliférations d’algues et des exterminations de poissons ont été signalées dans une rivière de la côte de Géorgie (USA) à l’aval d’une usine de conditionnement de volaille, ce qui a amené les autorités à conclure que les problèmes résultaient d’un écoulement d’origine terrestre associé à un apport d’eau usée excessif au niveau des champs d’épandage de l’usine (LAS).Une recherche a été entreprise dans le but de vérifier l’hypothèse que l’eau souterraine polluée jouait aussi un rôle significatif. Des prélèvements hebdomadaires ont été effectués pendant une période de 12 mois le long d’un tronçon de 18 km de la rivière et des principaux affluents. Les résultats ont montré des concentrations élevées en azote dans les affluents drainant l’usine et une augmentation d’un facteur dix des nitrates dans la rivière entre les apports des affluents. Parce que les concentrations en ammoniaque étaient basses sur ce tronçon, on a conclu que les nitrates étaient apportés par l’écoulement de la nappe. Des données provenant d’échantillonnage minutieux en rivière et d’échantillons ponctuels de sources et de forages ont été utilisées pour isoler le point d’entrée de la langue de pollution. L’analyse a mis en évidence deux langues séparées; l’une associée à la lagune d’eau usée non étanchée de l’usine et une autre à ses champs d’épandage LAS. On a trouvé que l’écoulement continu d’eau polluée de la nappe pendant les conditions estivales de basses eaux a un impact plus prononcé sur la qualité de l’eau de rivière que les apports périodiques d’écoulements d’origine terrestre et des affluents.

Detección de la contaminación de aguas subterráneas de un río en Georgia, EEUU utilizando el muestreo de caudal base

Resumen

La información de la floración de algas y de la mortandad de peces muertos en un río en las zonas costeras Georgia (EEUU), aguas abajo de una planta de procesamiento de aves de corral, impulsó a los funcionarios a concluir que los problemas eran el resultado del flujo superficial asociados con una sobre-aplicación de aguas residuales en el sistema de uso de la tierra de la planta. Se realizó una investigación para probar la hipótesis que las aguas subterráneas contaminadas también desempeñaban un papel significativo. Se colectaron muestras semanales durante un período de 12 meses a lo largo de un tramo de 18 km del río y de los afluentes principales. Los resultados mostraron concentraciones elevadas de nitrógeno en los afluentes que drenaban la planta y un aumento de 10 veces en los nitratos del río entre los puntos de ingreso de los afluentes. Debido a que las concentraciones de amoníaco fueron bajas en este tramo, se concluyó que el nitrato estaba entrando a través de la descarga de las aguas subterráneas. Se usaron datos de muestreos detallados del río y muestras directas de aguas subterráneas de manantiales y perforaciones para aislar el punto de entrada de la pluma de contaminantes. Los análisis mostraron dos plumas separadas, una asociada con las lagunas de aguas residuales no cubiertas de la planta y otro con los campos de aspersión del sistema de uso de la tierra. Se encontró que la continua descarga de agua subterránea contaminada en condiciones de flujos bajos durante el verano tenía un impacto más profundo en la calidad del agua del río que los ingresos periódicos del agua por flujo superficial y por escurrimiento de los afluentes.

利用基流取样探测美国乔治亚州某河流的地下水污染

摘要

在位于美国乔治亚州沿海地区某家禽加工厂下游的河流中发生藻华和鱼类死亡的现象见诸报道后, 政府断定问题系由与该厂土地处理系统 (LAS) 废水过量引起的坡面流所致。为了检验污染地下水是否也起到了重要作用, 我们进行了专门调查。每周对18 km长的河段及其重点支流进行取样, 为期12个月。结果显示, 排泄该处理厂尾水的支流中氮浓度升高, 两支流之间的河段硝酸根增加了十倍。由于该河段氨浓度较低, 故推断硝酸盐系通过地下水的排泄而进入河中。根据详细的河水取样和由泉、钻孔直接取得的地下水样数据, 找出了污染羽的源头。分析表明存在两个独立的污染羽, 一个与该厂无衬砌废水塘有关, 另一个与该厂LAS的喷雾场地有关。夏季径流量较小时污染地下水向河流的持续排泄对河流水质的影响要大于周期性的坡面流和支流的径流补给。

Detecção da contaminação de água subterrânea num rio na Geórgia, EUA, utilizando amostragens do caudal de base

Resumo

Foram detectados fenómenos de explosão de algas e de morte de peixes num rio localizado na zona costeira da Geórgia, a jusante de uma fábrica de processamento de aves. Relatórios técnicos confirmaram que aqueles problemas resultaram de um escoamento superficial ou sub-superficial associado a uma sobre-aplicação de águas residuais envolvidas num sistema de aplicação desses resíduos no solo (plant’s land application system, LAS). De forma a estudar a hipótese de que aquela contaminação tenha também a sua origem em descargas de água subterrânea, foi efectuada uma investigação que consistiu na recolha de amostras semanais por um período de 12 meses ao longo dos 18 km do rio e dos seus afluentes. Os resultados das análises mostraram existir elevadas concentrações de compostos azotados nos rios tributários que drenam a área da fábrica e a decuplicação dos valores de nitrato no rio entre aqueles tributários. Porque as concentrações de amonia se revelaram baixas neste troço, concluiu-se que a origem da contaminação por nitrato provém de descarga de água subterrânea contaminada. Foi assim realizada uma amostragem detalhada no rio, em nascentes e em poços, com o objectivo de localizar o ponto de entrada da pluma de contaminação. A análise mostrou existirem duas plumas distintas, uma associada à lagoa das águas residuais da fábrica e outra associada com os dispositivos de dispersão de rega no campo (LAS). A descarga contínua de água subterrânea contaminada durante os períodos de caudal reduzido na época de Verão mostrou ter um maior impacte na qualidadae da água do rio do que as entradas periódicas de caudal superficial e sub-superficial arrastado dos terrenos agrícolas e do que escoamento proveniente dos tributários.

Notes

Acknowledgements

The authors would like to thank the Associate Editor and two anonymous reviewers for their critical review of the manuscript. Thanks are also extended to the Managing Editor, Professor Craig Simmons, who welcomed and encouraged the new focus of this report.

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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  1. 1.Department of Geology and GeographyGeorgia Southern UniversityStatesboroUSA
  2. 2.StatesboroUSA

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