Evaluation of sequentially-coupled POP fluxes estimated from simultaneous measurements in multiple compartments of an air–water–sediment system

Abstract

Bulk atmospheric deposition fluxes, air-water exchange fluxes, particle settling fluxes out of the upper water column, sediment trap fluxes in deep waters, and sediment burial fluxes of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) were simultaneously measured in the Koster Fjord, eastern Skagerak, on the Swedish west coast. The aim of the study was to compare the magnitude and direction of the compound fluxes in the system in order to diagnose key fate processes. The PCB and PAH fluxes via net atmospheric deposition, settling particles out of the surface and through deep waters, as well as into the accreting underlying sediments were shown to be remarkably similar, agreeing within a factor of a few for any given target compound. Fluxes of all PCB and PAH target compounds remained fairly constant with water column depth. Thus there was no evidence for net desorption from sinking particles. The net unidirectional and near balancing of vertical fluxes suggests a net transport of PCBs and PAHs from the atmosphere to the continental shelf sediments in the Koster Fjord, which is consistent with the hypothesis that the shelf sediments are important sinks for these compounds.

Inter-compartmental transport of organophosphate and pyrethroid pesticides in South China: Implications for a regional risk assessment

“…It should be noted, however, that the estimation used in the present study was based on annual atmospheric and water concentrations within a limited time scale so the conclusions do not represent the absolute transport directions. The airewater gaseous exchange processes were also controlled by environmental conditions, like temperature and wind speed, and seasonal variation in directions of airewater gaseous exchange has been observed in previous studies (McConnell et al, 1997;Palm et al, 2004). Contaminants found in the water did not only experience volatilization into the air, but also accumulated into sediments due to the sinking of suspended particles, sediment burial processes and water-sediment diffusion (Meijer et al, 2006).…”

“…Chlorpyrifos had a higher gaseous exchange flux compared to the pyrethroids, which was due to not only its higher total atmospheric concentrations, but also its higher vapor pressure and subsequently higher percentage of compound in the gas phase relative to the particles (Li et al, 2014). This result was supported by the research conducted by Palm et al (2004). Surprisingly, chlorpyrifos had lower water concentrations than cypermethrin and permethrin, which was contradictory to its higher usage amount and air to water flux.…”

“…The fluxes of pesticides into water bodies from soil runoff, estimated from soil concentrations and soil erosion rates during rain events, were 13.3, 6.60, 23.7, 394 and 17.8 mg/km 2 /d for chlorpyrifos, bifenthrin, lambda-cyhalothrin, cypermethrin and permethrin, respectively (Table 2). After entering surface water, the CUPs will re-distribute between the freely dissolved and particle-bound forms (Palm et al, 2004) and experience different transport processes (e.g. remain in the water column or be deposited in the sediment).…”

“…Atmospheric deposition of dry and wet particle-bound chlorpyrifos (29.1 mg/km 2 /d), however, was 26 times less than the flux of suspended particles being deposited into the sediments (756 mg/km 2 /d), suggesting that atmospheric particle-bound chlorpyrifos only accounted for a small portion of the particle-bound chlorpyrifos found in the water column. Since the contaminants can re-distribute between the unbound and particle-bound forms after they are deposited into water (Palm et al, 2004), this complicates the balance of chlorpyrifos within the airewater-sediment system.…”

“…By identifying the most critical media for a contaminant, the output of fate models provides a means to integrate transport dynamics of the contaminants into regional risk assessments (Cowan et al, 1995;Lammel et al, 2007). To date, attempts to assess inter-compartmental transport have focused on persistent organic pollutants, like polycyclic aromatic hydrocarbons (Palm et al, 2004), polychlorobiphenyls (Meijer et al, 2006;Palm et al, 2004), polybrominated diphenyl ethers (Guan et al, 2009) and organochlorine pesticides (Lammel et al, 2007;Zhang et al, 2011).…”