Bruno Gouteux

Analysis of six relevant toxaphene congeners in biological samples using ion trap MS/MS.

The quantification of six polychlorinated bornanes (CHBs) was studied using ion trap MS/MS. The significance of the selection of parent ions (Ip) and daughter ions (Id) on the detection of these toxaphene congeners was assessed in standard solution and biological samples. Our results indicate that different Ip and Id, selected at either low or high mass-to-charge (m/z) ratios, influence drastically the response factor of the CHBs and the chemical noise observed. For the octachlorinated toxaphene congeners (Parlar-26 (P-26), Parlar-40/41 (P-40/41), Parlar-44 (P-44)), the detection performance of the ion trap MS/MS is similar whether Ip and Id were chosen at low or high m/z ratios. However, the selection of Ip and Id at high m/z ratios clearly enhances the detection of the nonachlorinated toxaphene congeners (Parlar-50 (P-50), Parlar-62 (P-62)). The improved method, which selects Ip and Id at low m/z ratios for P-26, P-40/41 and P-44 and at high m/z ratios for P-50 and P-62, permitted to obtain low detection limits as well as repeatable and accurate results.

Sorption and competition of two persistent organic pesticides onto marine sediments: Relevance to their distribution in aquatic system

Sorption is a key process in the distribution of substances between environmental compartments in marine ecosystems. Two persistent organic pesticides, also known as toxaphene congeners, namely B8-1413 (P26) and B9-1679 (P50), are of special interest because they are not detected in sediments while relatively concentrated in marine mammals. Sorption-desorption, entrapment and competition behaviors of these pesticides onto marine sediments were studied to explain their environmental distribution. Data obtained under marine experimental conditions were fitted to sorption models to evaluate sorption coefficients and to assess the degree of B8-1413/B9-1679 entrapment of the two toxaphene congeners in sediments. Carbon normalized sorption coefficients (Koc) of both congeners were similar under in cold (2°C) marine (30 psu) conditions with high values ranging from 1.53×10(5) to 3.28×10(5) mL g(-1)indicative of a strong affinity to marine sediments However, the sorption-desorption investigations indicate that B8-1413/B9-1679 were on average 2.5 times less entrapped in sediments compared to B7-1450, a toxaphene congener known to accumulate predominantly in sediments. These results suggest that the low entrapment of B8-1413 and B9-1679 favor their availability and transfer to biological matrices.

Sorption of Pesticides on Natural Geosorbents

Pesticides are chemicals used to manage pest organisms in both agricultural and non-agricultural environments. They include important classes of compounds such as herbicides, insecticides, fungicides, and biocides (Table 1). Their dispersion into agricultural environments occurs through a variety of methods including air and ground spraying. Relatively few pesticide applications are made directly and exclusively to a target pest, and most application methods rely on the use of an appreciable quantity of pesticides to the environment so that exposure to the pest species reaches effective levels. Estimates for some scenarios indicate that less than 0.1% of the applied materials reach the target pest (Pimentel & Levitan, 1986), the other important fraction of the discharged pesticide is dispersed in the environment. Considering the inherent toxicity and the possible deleterious effects of pesticides, it is of paramount importance to study the pathway and behaviour of excess pesticides released into the environment. Soils and sediments, also called geosorbents, are important sinks for pesticides because of their tremendous quantities and their ability to accumulate, or sorb, large amounts of harmful compounds. How long does a pesticide remain in soils or in sediments depends on how fast it is volatilized, solubilized or degraded, but also on how strongly it is bound by soils or sediment components (Arias-Estevez et al., 2008). Increasing amounts of research reveal that sorption is a key process for deciding the ultimate transport, persistence, bioactivity, and risk exposition of organisms to pesticides in the environment. The extent of sorption is related to structural and chemical characteristics of the pesticides (Table 1) that control some environmentally important physicochemical parameters such as volatility, water solubility, and octanol-water partition coefficient. Moreover, various soil or sediment properties including organic matter content, type and amount of clay content, ion exchange capacity and pH also modulate the magnitude of the sorption on geosorbents. A way to describe the subtle interactions of pesticides with natural geosorbents is to discuss their compositions and the interactions involved in the sorption process and the key equations that describe the sorption in an environmental perspective. The main objective of this brief review is to examine the processes of sorption on natural solids, the geosorbents, which strongly determine the persistence, mobility and bioavailability of pesticides in the environment.

Investigations on the sorption of a toxaphene model congener, the B7-1450, on marine sediments

Sorption is a natural process that takes place in sediments or soils and changes the mobility and availability of hydrophobic organic compounds, such as toxaphene pesticide in the environment. The sorption of the 2-exo,3-endo,5-exo,8,9,10,10-heptachlorobornane (B7-1450), used as a model compound of the toxaphene heptachlorobornane congeners found in sediments, was investigated for the first time through a series of batch sorption experiments. The losses of B7-1450 due to adsorption onto glass walls and to evaporation occurring during analytical treatment steps were corrected. The study showed that these specific losses ranged from 2% to 3.5% for the glass walls adsorption and can be as high as 15% for the evaporation treatment. The sorption coefficients, K(d) and K(oc), of B7-1450 could be overestimated by >30%, particularly for low-concentration samples, if the losses were not corrected. Loss correction equations were established, validated and applied to determine sorption coefficients for the B7-1450 congener. The K(oc) values for B7-1450 determined over a gradient of concentrations ranged from 3.5x10(4) to 6.5x10(4)mlg(-1), revealing a strong affinity of B7-1450 for marine sediments.

Sorption behaviors of a persistent toxaphene congener on marine sediments under different physicochemical conditions

Sorptive processes are important parameters affecting the mobility, availability and fate of persistent organic pollutants (POPs), such as toxaphene, in aquatic systems. The sorption and desorption behaviors of the B7-1450, a stable toxaphene congener in environment, on marine sediment was studied under different temperature and salinity conditions to better understand the B-1450 distribution in estuarine systems. The data were fitted to different sorption models to characterize sorption behaviors by evaluating sorption coefficients and sequestrated fraction of B7-1450 on sediments. High carbon-normalized sorption coefficients (Koc) of the B7-1450 were observed with values ranging from 3.2×104 to 6.0×104 mL g(-1) under experimental conditions. The data showed an increase of B7-1450 sorption coefficients with the salinity and a decrease with temperature. These investigations indicate that B7-1450 is three times more sequestred on sediments in cold (2°C, 30 psu) than in warm marine conditions (20°C, 30 psu). These results suggest that the mobility and bioavailable of B7-1450 or other POPs from the sediments could be less important in cold marine comparatively in warm marine and warm freshwater media. As a result of climate changes, the warming of mid and high latitudes coastal waters could enhance the mobility of POPs.