Identification of Groundwater Nitrate Contamination from Explosives Used in Road Construction: Isotopic, Chemical, and Hydrologic Evidence.
Environ Sci Technol
; 50(2): 593-603, 2016 Jan 19.
Article
em En
| MEDLINE
| ID: mdl-26709616
ABSTRACT
Explosives used in construction have been implicated as sources of NO3(-) contamination in groundwater, but direct forensic evidence is limited. Identification of blasting-related NO3(-) can be complicated by other NO3(-) sources, including agriculture and wastewater disposal, and by hydrogeologic factors affecting NO3(-) transport and stability. Here we describe a study that used hydrogeology, chemistry, stable isotopes, and mass balance calculations to evaluate groundwater NO3(-) sources and transport in areas surrounding a highway construction site with documented blasting in New Hampshire. Results indicate various groundwater responses to contamination (1) rapid breakthrough and flushing of synthetic NO3(-) (low δ(15)N, high δ(18)O) from dissolution of unexploded NH4NO3 blasting agents in oxic groundwater; (2) delayed and reduced breakthrough of synthetic NO3(-) subjected to partial denitrification (high δ(15)N, high δ(18)O); (3) relatively persistent concentrations of blasting-related biogenic NO3(-) derived from nitrification of NH4(+) (low δ(15)N, low δ(18)O); and (4) stable but spatially variable biogenic NO3(-) concentrations, consistent with recharge from septic systems (high δ(15)N, low δ(18)O), variably affected by denitrification. Source characteristics of denitrified samples were reconstructed from dissolved-gas data (Ar, N2) and isotopic fractionation trends associated with denitrification (Δδ(15)N/Δδ(18)O ≈ 1.31). Methods and data from this study are expected to be applicable in studies of other aquifers affected by explosives used in construction.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Poluentes Químicos da Água
/
Água Subterrânea
/
Substâncias Explosivas
/
Nitratos
Tipo de estudo:
Diagnostic_studies
/
Prognostic_studies
País/Região como assunto:
America do norte
Idioma:
En
Ano de publicação:
2016
Tipo de documento:
Article