International audience | The desorption rate is an important factor determining cadmium (Cd) ecotoxicity and pollution remediation in soils. The pedotransfer functions (PTFs) of desorption rate coefficients of fresh Cd in soils have been developed in literature. We hypothesized that the aging of Cd pollution would alter Cd desorption process. Taking historically polluted soils as the object, this study aimed at testing the hypothesis and developing new PTFs of desorption rate coefficients for historical Cd. 15 d batch extraction experiments and 13 kinetic models were employed to define Cd desorption rate coefficients in 27 historically polluted soil samples. Compared with fresh Cd, the desorption rate coefficients of historical Cd were lower, and the break time of biphasic desorption processes was retarded to 3 d (4320 min). Different with the usual models for fresh Cd desorption (e.g. parabolic diffusion and two constant rate models), the best models to mimic the historical Cd desorption processes were the pseudo first order, logarithmic, Elovich, and simple Elovich models. The rate-limiting step controlling Cd desorption was changed from the intraparticle diffusion to the interface reaction with aging of pollution. New PTFs of desorption rate coefficients of historical Cd were established (R2 ≥ 0.71). Cd desorption rate coefficients increased with organic matter and clay contents, but decreased with oxalate extractable Fe content, solution pH, cation exchange capacity, and silt content. The key soil properties influencing desorption rate coefficients were not altered by the aging of pollution. The developed PTFs could guide us to adjusting the ecotoxicity and pollution remediation of Cd in historically polluted field soils.

The desorption rate is an important factor determining cadmium (Cd) ecotoxicity and pollution remediation in soils. The pedotransfer functions (PTFs) of desorption rate coefficients of fresh Cd in soils have been developed in literature. We hypothesized that the aging of Cd pollution would alter Cd desorption process. Taking historically polluted soils as the object, this study aimed at testing the hypothesis and developing new PTFs of desorption rate coefficients for historical Cd. 15 d batch extraction experiments and 13 kinetic models were employed to define Cd desorption rate coefficients in 27 historically polluted soil samples. Compared with fresh Cd, the desorption rate coefficients of historical Cd were lower, and the break time of biphasic desorption processes was retarded to 3 d (4320 min). Different with the usual models for fresh Cd desorption (e.g. parabolic diffusion and two constant rate models), the best models to mimic the historical Cd desorption processes were the pseudo first order, logarithmic, Elovich, and simple Elovich models. The rate-limiting step controlling Cd desorption was changed from the intraparticle diffusion to the interface reaction with aging of pollution. New PTFs of desorption rate coefficients of historical Cd were established (R² ≥ 0.71). Cd desorption rate coefficients increased with organic matter and clay contents, but decreased with oxalate extractable Fe content, solution pH, cation exchange capacity, and silt content. The key soil properties influencing desorption rate coefficients were not altered by the aging of pollution. The developed PTFs could guide us to adjusting the ecotoxicity and pollution remediation of Cd in historically polluted field soils.

International audience | While numerous studies have examined the effect of N deposition on ecosystem N retention, few have analyzed the involvement of plant species and climate warming in this process. We experimentally investigated the effects of increasing N deposition (Nexo) and climate warming on the fate of Nexo in a subalpine meadow and established the involvement of plant species. Using 15N tracer, we tracked Nexo sprayed on the vegetation in belowground and aboveground plant biomasses (AGB) and in bulk soil over three growing seasons. We assessed the Nexo absorption capacity of plant species and the contribution of Nexo to their AGB N pool. The meadow retained a large proportion of Nexo (≈65%, mostly in AGB) for depositions up to four times the background N rate. Nexo present in the meadow compartments in year 2 was still present in year 3, suggesting that the ecosystem was unsaturated after three years of high N input. Nexo retention resulted more from an increase in N concentration in plant tissues than from the increase in AGB. The species-specific Nexo absorption capacity was inversely related to their AGB N concentration. Nexo accounted for up to 40% of total AGB N depending on the species and the N treatments. The contribution of species to ecosystem Nexo retention more contingent on their AGB than on their relative cover in the community, ranked as follows: C. vulgaris (14.0%) > N. stricta (7.0%) > other Poaceae = C. caryophyllea (2.5%) > other Eudicotyledons (1.5%) > non-vascular species = P. erecta > Fabaceae (0.8–0.2%). Climate warming increased AGB and decreased tissue N concentration. No warming-Nexo interaction was observed. Thus, Pyrenean subalpine meadows that have not undergone a decline in plant species richness in recent decades paradoxically display a high potential to sequester atmospheric N deposition.

While numerous studies have examined the effect of N deposition on ecosystem N retention, few have analyzed the involvement of plant species and climate warming in this process. We experimentally investigated the effects of increasing N deposition (Nexo) and climate warming on the fate of Nexo in a subalpine meadow and established the involvement of plant species. Using 15N tracer, we tracked Nexo sprayed on the vegetation in belowground and aboveground plant biomasses (AGB) and in bulk soil over three growing seasons. We assessed the Nexo absorption capacity of plant species and the contribution of Nexo to their AGB N pool. The meadow retained a large proportion of Nexo (≈65%, mostly in AGB) for depositions up to four times the background N rate. Nexo present in the meadow compartments in year 2 was still present in year 3, suggesting that the ecosystem was unsaturated after three years of high N input. Nexo retention resulted more from an increase in N concentration in plant tissues than from the increase in AGB. The species-specific Nexo absorption capacity was inversely related to their AGB N concentration. Nexo accounted for up to 40% of total AGB N depending on the species and the N treatments. The contribution of species to ecosystem Nexo retention more contingent on their AGB than on their relative cover in the community, ranked as follows: C. vulgaris (14.0%) > N. stricta (7.0%) > other Poaceae = C. caryophyllea (2.5%) > other Eudicotyledons (1.5%) > non-vascular species = P. erecta > Fabaceae (0.8–0.2%). Climate warming increased AGB and decreased tissue N concentration. No warming-Nexo interaction was observed. Thus, Pyrenean subalpine meadows that have not undergone a decline in plant species richness in recent decades paradoxically display a high potential to sequester atmospheric N deposition.

International audience | Mercury (Hg) is a pervasive contaminant reaching Antarctic environments through atmospheric transport and deposition. Seabirds as meso to top predators can accumulate high quantities of Hg through diet. Reproduction is one of the most sensitive endpoints of Hg toxicity in marine birds. Yet, few studies have explored Hg exposure and effects in Antarctic seabirds, where increasing environmental perturbations challenge animal populations. This study focuses on the Antarctic petrel Thalassoica antarctica from Svarthamaren, Antarctica, where the world's largest breeding population is thought to be in decline. Hg and the stable isotopes of carbon (δ13C, proxy of feeding habitat) and nitrogen (δ15N, trophic position/diet) were measured in red blood cells from 266 individuals over two breeding years (2012–13, 2013–14). Our aims were to 1) quantify the influence of individual traits (size and sex) and feeding ecology (foraging location, δ13C and δ15N values) on Hg exposure, and 2) test the relationship between Hg concentrations with body condition and breeding output (hatching success and chick survival). Hg concentrations in Antarctic petrels (mean ± SD, 0.84 ± 0.25, min-max, 0.42–2.71 μg g−1 dw) were relatively low when compared to other Antarctic seabirds. Hg concentrations increased significantly with δ15N values, indicating that individuals with a higher trophic level (i.e. feeding more on fish) had higher Hg exposure. By contrast, Hg exposure was not driven by feeding habitat (inferred from both foraging location and δ13C values), suggesting that Hg transfer to predators in Antarctic waters is relatively homogeneous over a large geographical scale. Hg concentrations were not related to body condition, hatching date and short-term breeding output. At present, Hg exposure is likely not of concern for this population. Nevertheless, further studies on other fitness parameters and long-term breeding output are warranted because Hg can have long-term population-level effects without consequences on current breeding success.

Mercury (Hg) is a pervasive contaminant reaching Antarctic environments through atmospheric transport and deposition. Seabirds as meso to top predators can accumulate high quantities of Hg through diet. Reproduction is one of the most sensitive endpoints of Hg toxicity in marine birds. Yet, few studies have explored Hg exposure and effects in Antarctic seabirds, where increasing environmental perturbations challenge animal populations. This study focuses on the Antarctic petrel Thalassoica antarctica from Svarthamaren, Antarctica, where the world's largest breeding population is thought to be in decline. Hg and the stable isotopes of carbon (δ13C, proxy of feeding habitat) and nitrogen (δ15N, trophic position/diet) were measured in red blood cells from 266 individuals over two breeding years (2012–13, 2013–14). Our aims were to 1) quantify the influence of individual traits (size and sex) and feeding ecology (foraging location, δ13C and δ15N values) on Hg exposure, and 2) test the relationship between Hg concentrations with body condition and breeding output (hatching success and chick survival). Hg concentrations in Antarctic petrels (mean ± SD, 0.84 ± 0.25, min-max, 0.42–2.71 μg g−1 dw) were relatively low when compared to other Antarctic seabirds. Hg concentrations increased significantly with δ15N values, indicating that individuals with a higher trophic level (i.e. feeding more on fish) had higher Hg exposure. By contrast, Hg exposure was not driven by feeding habitat (inferred from both foraging location and δ13C values), suggesting that Hg transfer to predators in Antarctic waters is relatively homogeneous over a large geographical scale. Hg concentrations were not related to body condition, hatching date and short-term breeding output. At present, Hg exposure is likely not of concern for this population. Nevertheless, further studies on other fitness parameters and long-term breeding output are warranted because Hg can have long-term population-level effects without consequences on current breeding success.