Fate and Origin of 1,2-Dichloropropane in an Unconfined Shallow Aquifer

Abstract

A shallow aquifer with different redox zones overlain by intensive agricultural activity was monitored for the occurrence of 1,2-dichloropropane (DCP) to assess the fate and origin of this pollutant. DCP was detected more frequently in groundwater samples collected in aerobic and nitrate-reducing zones than those collected from iron-reducing zones. Simulated DCP concentrations for groundwater entering an iron-reducing zone were calculated from a fate and transport model that included dispersion, sorption, and hydrolysis but not degradation. Simulated concentrations were well in excess of measured values, suggesting that microbial degradation occurred in the iron-reducing zone. Microcosm experiments were conducted using aquifer samples collected from iron-reducing and aerobic zones to evaluate the potential for microbial degradation of DCP and to explain field observations. Hydrogenolysis of DCP and production of monochlorinated propanes in microcosm experiments occurred only with aquifer materials collected from the iron-reducing zone, and no dechlorination was observed in microcosms established with aquifer materials collected from the aerobic zones. Careful analyses of the DCP/1,2,2-trichloropropane ratios in groundwater indicated that older fumigant formulations were responsible for the high levels of DCP present in this aquifer.

Populations Implicated in Anaerobic Reductive Dechlorination of 1,2-Dichloropropane in Highly Enriched Bacterial Communities

“…Most of the contamination with 1,2-D has occurred in oxygen-limited or anaerobic subsurface environments, where reductive processes are more probable (17,34). In a previous study, the reductive dechlorination (i.e., hydrogenolysis) of 1,2-D to monochlorinated propanes and subsequent dehydrochlorination to propene was demonstrated in microcosms derived from river sediment (17).…”

Biodegradability of chlorinated solvents and related chlorinated aliphatic compounds

“…The half-life of 1,3-DCPrpE in soil treated with manure was only 0.5 d (Dungan et al 2001). In sediments, evidence for 1,2-DCPrpA degradation was observed in an iron-reducing zone of an aquifer contaminated by agricultural activity (Tesoriero et al 2001). The field evidence indicated that no degradation was occurring in aerobic or denitrifying zones.…”

The Geochemistry of Pesticides

“…For example, Burow et al (1999) used data on the occurrence of DBCP and two of its transformation products to examine the relative importance of physical and chemical processes in controlling the fate of the fumigant in groundwater. Tesoriero et al (2001) employed a combination of field and laboratory studies to demonstrate the importance of redox conditions in controlling the fate of another fumigant, 1,2-dichloropropane, in groundwater ( Figure 19). Data on the occurrence of atrazine and DEA (also abbreviated as 'CIAT' by some authors; e.g., Erickson and Lee, 1989) in surface and groundwaters across the United States have provided persuasive evidence that the 'DEA fraction' (i.e., the molar proportion of atrazine-derived compounds that is present in a given environmental medium as DEA) increases with increasing residence time in the vadose zone (Barbash and Kolpin, 2010).…”