While the influence of climate change on the fate of persistent organic pollutants (POPs) is becoming a topic of global concern, it has yet to be demonstrated how POPs and their transformation products in soil respond to a changing climate at the local scale. We conducted a year-long field experiment with spiked soils to investigate the impact of climate on the dissipation of γ-hexachlorocyclohexane (γ-HCH) and p,p’-dichlorodiphenyltrichloroethane (p,p’-DDT) as well as the formation of their products. Four sites along an elevational gradient on the eastern Tibetan Plateau were selected to represent four scenarios ranging from a dry and cold to a warm and humid climate. Based on the measured concentrations of the two pesticides and their transformation products, we calculated the dissipation rates of γ-HCH and p,p’-DDT in soil using two biphasic kinetic models, and the formation rates of transformation products using a mid-point rectangular approximation method. The spiked γ-HCH generally showed the expected decrease in dissipation from soils with increasing altitudes, and therefore decreasing temperature and precipitation, whereas dissipation of p,p’-DDT was influenced more by photolysis and sequestration in soil. The formation rates of the primary products of γ-HCH (i.e. γ-HCH→PeCCH and γ-HCH→TeCCH) and p,p’-DDT (i.e. p,p’-DDT→p,p’-DDE and p,p’-DDT→p,p’-DDD) indicate that a warmer and wetter climate favors dechloroelimination (anaerobic biodegradation) over dehydrochlorination (aerobic biodegradation). The significantly longer dissipation half-lives of γ-HCH at the coldest site suggests that the fate of POPs in frozen regions (e.g. polar regions) needs more attention. Overall, the fate of more volatile chemicals (e.g. γ-HCH) might be more responsive to the climate change.

International audience | Diffuse phytosanitary pollution is a complex phenomenon to manage. Reducing this type of pollution is one of today’s key socio-economic and environmental challenges. At the regional level, few approaches enable the actors concerned to implement agricultural management strategies to reduce the use and impact of phytosanitary products. Our research problem focused on the consequences of intensive agriculture and, in particular, how to evaluate the impact of phytosanitary products on human health and the environment. In this article, we present the SimPhy simulation game which places the actors from a given region directly into a situation in which they manage farms whilst under pressure to reduce phytosanitaries (quantity and toxicity). The application focused on the Merja Zerga catchment area in Morocco. The region is dominated by intensive agriculture which is located upstream from a Ramsar-classified wetland area. The SimPhy simulation game is based on a decision support system-type tool. It allows us to anticipate the impact of regulations on farming systems. It also enables us to analyse the consequences of the actors’ strategies on farm economies, human health and the quality of ecosystems. Initial results from the SimPhy simulation game enabled the technicians from Agricultural Development Center (CDA) themselves to learn about managing agricultural production systems in a dynamic and interactive fashion. With the simulation game, it was possible to learn about the farmer's ability to adapt to new regulatory constraints, and the involved consequences for toxicity risks for human health and the environment.

The formation of evaporites associated with the final stages of the precipitation sequence, such as the case of halite, is frequent in marshes in arid areas, but it is not to be expected in those humid climates. This work, by means of the study of the hydrological, climatic and land use conditions, identifies the factors that allow the formation of saline precipitations in a marsh located in a humid climate area. The results obtained show that the exclusion of the marsh as a result of the embankment is the main reason for the presence of halite. It is to be expected that in the future the growth of the embanked marsh areas, together with the climatic and tidal condition tendencies recorded, will favour a higher rate of formation of evaporite salts. The identification of these factors makes it possible to set basic sustainable management guidelines to avoid soil salinisation.

In this study, 84 surface sediment samples, from 28 Iranian rivers, 45 surface sediment samples and 31 samples from one core in the southwest of the Caspian Sea were collected and analyzed for polycyclic aromatic hydrocarbons (PAHs). The results showed high variability of perylene in coastal surface sediments (1.3–123.6ngg−1dw) and river sediments (0.5–111.1ngg−1dw). Core samples revealed high levels of perylene which increased with depth. Three diagnostic ratios (DRs) for source identification of perylene (Per/TPAH, Per/PAI and Py/Per) revealed a dominance of biogenic inputs to the surface layers (coasts and rivers) and diagenetic production of perylene in the sediment core. Hyrcanian forests with humid climates favor wood-degrading fungi and the production of perylene and its precursors. Biogenic production of perylene as a land plant derived biomarker can be used for the reconstruction of paleoclimatic conditions of the southwest Caspian Sea.

This study examined the sensitivity of reference crop evapotranspiration (ET₀) to climatic variables in a humid region in Iran. ET₀ was estimated using the FAO-56 Penman–Monteith (PMF-56), Blaney–Criddle (BC), and Hargreaves–Samani (HG) methods. Sensitivity analysis was performed by two distinct methods which were (i) changing the value of a certain climatic parameter in a range between ± 20% of its long-term mean with an increment of 5%, and calculating the percentage of change in ET₀, while the other parameter values were kept constant; and (ii) calculating the sensitivity coefficients (SCs) for each of the climatic variables. For each of the climatic parameters, the Iso-SC maps were plotted using the Arc-GIS software. Results indicated that the most sensitive parameter for ET₀ was the maximum air temperature (Tₘₐₓ) by PMF-56 and HG methods. Increasing Tₘₐₓ up to 20% led to an increase in ET₀ between 8.5 and 15%, at the selected stations by PMF-56. In contrast, the less sensitive parameter for ET₀ was the minimum air temperature (Tₘᵢₙ) for PMF-56 and Tₘₑₐₙ for HG. For PMF-56, increasing the minimum relative humidity (RHₘᵢₙ) to 20% led to a decrease in ET₀ in the range between 0.5 and 5%. The highest values of SC in the cases of Tₘₐₓ and Tₘᵢₙ were found to be equal to 0.8 and 0.53, respectively. Similarly, the SC in the case of RHₘᵢₙ varied between − 0.29 and − 0.0038. This range for wind speed was between 0.06 and 0.22 and in the case of sunshine hours it was between 0.272 and 0.385. These findings would be useful in the scientific management of water resources in the region.

High levels of heavy metals in soils may impose serious impacts on terrestrial organisms. In Brazil, the prevention values for evaluating the ecological risk of these elements are based only on soil chemical analyses and/or on data from ecotoxicological assays performed in soils of temperate regions. However, the attributes of the Brazilian highly-weathered tropical soils can influence the availability of heavy metals for soil fauna, resulting in different toxic values. To provide more accurate ecotoxicological risk values for arsenic (As) in tropical soils, we assessed the impacts of sodium arsenate (Na₂HAsO₄·7H₂O) on the reproduction of earthworms (Eisenia andrei) and collembolans (Folsomia candida), as well as on As bioaccumulation and growth (weight loss) of E. andrei in a tropical artificial soil (TAS) and in an Oxisol. In TAS, As doses reduced the reproduction of the species and promoted weight loss of earthworms. On the other hand, the reproductions of the species as well as the earthworm growth were not altered by As in the Oxisol. The effective concentrations that reduce the reproduction of E. andrei and F. candida by 50 % (EC₅₀) obtained in TAS (22.7 and 26.1 mg of As kg⁻¹ of dry soil, respectively) were lower than those in the Oxisol (>135 mg kg⁻¹, for both species). Although there was As bioaccumulation in earthworms in both soils, the internal concentrations in the earthworms were much higher in the oligochaetes exposed to arsenic in TAS. All these differences were attributed to the higher availability of As in the TAS, compared to the Oxisol, which increased the exposure of the species to the metal. The lower availability in the Oxisol was related to higher contents of type 1:1 silicate minerals and Fe and Al oxides and hydroxides, which strongly bind to As. These results highlight the importance of using tropical soils of humid regions to derive the Brazilian ecological risk prevention values for heavy metals, since the toxicity values are specific for these soils.

Atmospheric precipitation is a very important link in the water cycle. The characteristics of major ions (n = 341) and stable isotopes (δ²H, δ¹⁸O; n = 157) were analysed in Hangzhou and Huzhou, which are economically prosperous cities in East China. The δ²H and δ¹⁸O values of precipitation ranged from − 109.70 to 21.30‰ and from − 14.87 to − 0.95‰, respectively. Compared with the local meteoric water line (LMWL) of China, the slope and intercept of the LMWL were much higher in Hangzhou and Huzhou, which is related to the effects of the humid climate and less secondary evaporation. The δ²H and δ¹⁸O values were highest in spring because of the influence of air masses from the northern Asian continent and other nearby sources. In contrast, the air masses from the South China Sea and the western Pacific Ocean in the summer had the lowest δ²H and δ¹⁸O. The dominant ions in precipitation indicate that Ca²⁺, HCO₃⁻, SO₄²⁻, NH₄⁺ and NO₃⁻ are the main ions of precipitation in Hangzhou and Huzhou, and the dilution of precipitation leads to lower concentrations of ions in spring and summer, similar to the values found in most Chinese cities. The increase in motor vehicle use resulted in a lower [SO₄²⁻]/[NO₃⁻] ratio (1.64) of precipitation, indicating mixed acid rain in Hangzhou and Huzhou (HZS). Based on a combination of the correlation analysis, enrichment factors and source contributions, we determined that SO₄²⁻ and NO₃⁻ were introduced mainly from anthropogenic activities such as coal combustion and vehicle exhaust, accounting for 89% and 99%, respectively. The strong correlation between Cl⁻ and Na⁺, as well as Ca²⁺, Mg²⁺ and K⁺, indicates that these ions commonly have marine and crustal origins, respectively, and 40% of Mg²⁺ comes from a marine source.