High concentrations of TNT and related nitroaromatic compounds (NAC) can still be found in the soils. To evaluate the alkaline hydrolysis of NAC as a new remediation technology, two highly contaminated soils were treated under alkaline conditions using Ca(OH)2 as base. However, instead of the expected decrease, a temporary or even permanent increase was observed for several NAC. The extent of the intensity was affected by Ca(OH)2 concentration, suggesting the existence of desorption processes in the soil. The extent of the increase also depends on the soil investigated, the highest being observed with 1,3,5-trinitrobenzene (239 mg kg−1 compared to the baseline concentration of 24 mg kg−1) in the HTNT2 soil. This indicates incomplete NAC extraction and, hence, too low NAC concentrations measured in soils when conventional extraction procedures are used.
Simultaneous Filtration and Solid-Phase Extraction Combined with Large-Volume Injection in GC/MS for Ultra-Trace Analysis of Polar Pesticides in Surface Water
A method combining simultaneous filtration and solid-phase extraction (SPE) with large-volume injection (LVI) in gas chromatography/mass spectrometry (GC/MS) was developed to determine 13 polar pesticides in surface water. The selected pesticides - 4 organophosphorus, 7 organonitrogens and 2 triazine degradation products - were extracted from 0.5-L samples of filtered and raw water using cartridges filled with a silica-bonded material (1 g of ISOLUTE triazine, C-18) and a depth filter. No obstruction was observed during the extraction of raw water drawn from the St. Lawrence River (concentration of suspended particulate matter (SPM) ranging from 2 to 58 mg L−1). Overall percent recoveries were satisfactory for all the target pesticides (>60%) except desisopropyl-atrazine (more polar), which varied from 29 to 46% according to sample pH. The coefficient of variation was below 10% for the majority of the target pesticides and detection limits ranged from 0.1 to 0.8 ng L−1. Applied to real samples drawn from the St. Lawrence River, this method allowed for the detection of atrazine, cyanazine, desethyl-atrazine (DEA), desisopropyl-atrazine (DIA), metolachlor and simazine, at concentrations of 6 to 91 ng L−1. Using atrazine and metolachlor as examples, the correlation between filtered and raw water samples was more significant for the former (r = 0.87) than for the latter (r = 0.67). Temporal variations in atrazine and metolachlor in filtered water drawn from the St. Lawrence River, for example, were similar whether using the established method, based on liquid-liquid large-volume extraction (LVE) combined with GC/NPD analysis, or the one proposed herein. The latter method, however, systematically found atrazine concentrations 62% higher than those obtained by the older one, applied to the same field samples. Thus, the switch to the new analytical method will require the application of a correction factor to the atrazine concentration time series acquired with the previously used method.
- International Journal of Environmental & Analytical Chemistry
- Citations: 0
- Jan 1, 2003