Site-specific spatiotemporal occurrence and molecular congener distributions of naphthenic acids in Athabasca oil sands wetlands of Alberta, Canada.

The Athabasca oil sands region (AOSR) of Alberta, Canada is notable for its considerable unconventional petroleum extraction projects, where bitumen is extracted from naturally-occurring oil sands ore. The large scale of these heavy crude oil developments raises concerns because of their potential to distribute and/or otherwise influence the occurrence, behaviour, and fate of environmental contaminants. Naphthenic acids (NAs) are one such contaminant class of concern in the AOSR, so studies have examined the occurrence and molecular profiles of NAs in the region. We catalogued the spatiotemporal occurrence and characteristics of NAs in boreal wetlands in the AOSR over a 7-year period, using derivatized liquid chromatography-tandem mass spectrometry (LC-MS/MS). Comparing median concentrations of NAs across these wetlands revealed a pattern of NAs suggesting NAs in surface waters derived from oil sands deposits. Opportunistic wetlands that formed adjacent to reclaimed overburden and other reclamation activities had the highest concentrations of NAs and consistent patterns suggestive of bitumen-derived inputs. However, similar patterns in the occurrence of NAs were also observed in undeveloped natural wetlands located above the known surface-mineable oil sands deposit that underlies the region. Intra-annual sampling results along with inter-annual comparisons across wetlands demonstrated that differences in the spatial and temporal NA concentrations were dependent on local factors, particularly when naturally occurring oil sands ores were observed in the wetland or drainage catchment.

Natural climate solutions for Canada.

Alongside the steep reductions needed in fossil fuel emissions, natural climate solutions (NCS) represent readily deployable options that can contribute to Canada's goals for emission reductions. We estimate the mitigation potential of 24 NCS related to the protection, management, and restoration of natural systems that can also deliver numerous co-benefits, such as enhanced soil productivity, clean air and water, and biodiversity conservation. NCS can provide up to 78.2 (41.0 to 115.1) Tg CO2e/year (95% CI) of mitigation annually in 2030 and 394.4 (173.2 to 612.4) Tg CO2e cumulatively between 2021 and 2030, with 34% available at ≤CAD 50/Mg CO2e. Avoided conversion of grassland, avoided peatland disturbance, cover crops, and improved forest management offer the largest mitigation opportunities. The mitigation identified here represents an important potential contribution to the Paris Agreement, such that NCS combined with existing mitigation plans could help Canada to meet or exceed its climate goals.

Reduced translocation of cadmium from roots is associated with increased production of phytochelatins and their precursors.

Cadmium (Cd) is a non-essential trace element and its environmental concentrations are approaching toxic levels, especially in some agricultural soils. Understanding how and where Cd is stored in plants is important for ensuring food safety. In this study, we examined two plant species that differ in the distribution of Cd among roots and leaves. Lettuce and barley were grown in nutrient solution under two conditions: chronic (4 weeks) exposure to a low, environmentally relevant concentration (1.0 µM) of Cd and acute (1 h) exposure to a high concentration (5.0 mM) of Cd. Seedlings grown in solution containing 1.0 µM CdCl2 did not show symptoms of toxicity and, at this concentration, 77% of the total Cd was translocated to leaves of lettuce, whereas only 24% of the total Cd was translocated to barley leaves. We tested the hypothesis that differential accumulation of Cd in roots and leaves is related to differential concentrations of phytochelatins (PCs), and its precursor peptides. The amounts of PCs and their precursor peptides in the roots and shoots were measured using HPLC. Each of PC2₋4 was synthesized in the barley root upon chronic exposure to Cd and did not increase further upon acute exposure. In the case of lettuce, no PCs were detected in the root given either Cd treatment. The high amounts of PCs produced in barley root could have contributed to preferential retention of Cd in barley roots.

Mycorrhizal colonization and grain Cd concentration of field-grown durum wheat in response to tillage, preceding crop and phosphorus fertilization.

BACKGROUND: A 3-year field trial was conducted to investigate the effect of agricultural management practices including tillage, preceding crop and phosphate fertilization on root colonization by arbuscular mycorrhizal (AM) fungi and grain cadmium (Cd) concentration of durum wheat (Triticum turgidum L.). The relationship between grain Cd and soil and plant variables was explored to determine the primary factors affecting grain Cd concentration. RESULTS: Mycorrhizal colonization of the roots was reduced by conventional tillage or when the preceding crop was canola (Brassica napus L.), compared to minimum tillage or when the preceding crop was flax (Linum usitatissimum L.). In contrast, grain Cd was not consistently affected by any treatment. Grain Cd was generally below the maximum permissible concentration (MPC) of 100 microg Cd kg(-1) proposed by WHO. Grain Cd varied substantially from year to year, and could be predicted with 70% of variance accounted for by using the model: grain Cd concentration = - 321.9 + 44.5x ln(grain yield) + 0.26x soil DTPA-Cd + 182.5x soil electrical conductivity (EC)- 0.98x grain Zn concentration. CONCLUSIONS: These common agricultural management practices had no effect on grain Cd concentration in durum wheat though they impacted mycorrhizal colonization of roots. Grain yield and to a lesser extent soil conditions of EC and DTPA-Cd and grain Zn influenced grain Cd, whereas mycorrhizal colonization levels did not.