Incorporating carbon sink of harvested wood products into ecological footprint accounting: model and case study

Ecological footprint (EF) accounting system is widely used in assessing environmental sustainability at various spatial scales. To improve the EF performance, a new EF calculation framework was established in this study, in which HWP is considered as carbon sinks and the model was then applied to the Yangtze River basin of China. Results showed that (1) carbon sink in the basin is about 2.99 Tg per year and it varies substantially across subbasins, which has a nonlinear relationship with net primary productivity; (2) available biocapacity calculated in the whole basin increases from 0.5068 to 0.5759 national ha (nha) per capita when incorporating the carbon sinks. In a few subbasins, the added biocapacity is even larger than the biocapacity estimated from the conventional approach; (3) the EF of the basin is 5.598 nha per capita and it is much larger than its biological carrying capacity (BC), indicating that ecological deficit is ubiquitous across the basin. If carbon sinks are considered, the ecological deficit would decrease by 3.2–14.3% for different regions in the basin. It is necessary to incorporate HWP and other potential terrestrial carbon sinks in the EF accounting, and more efforts are needed in improving carbon sink accuracy

Resistance mechanisms and remediation potential of hexavalent chromium in Pseudomonas sp. strain AN-B15

The understanding of bacterial resistance to hexavalent chromium [Cr(VI)] are crucial for the enhancement of Cr(VI)-polluted soil bioremediation. However, the mechanisms related to plant-associated bacteria remain largely unclear. In this study, we investigate the resistance mechanisms and remediation potential of Cr(VI) in a plant-associated strain, AN-B15. The results manifested that AN-B15 efficiently reduced Cr(VI) to soluble organo-Cr(III). Specifically, 84.3 % and 56.5 % of Cr(VI) was removed after 48 h in strain-inoculated solutions supplemented with 10 and 20 mg/L Cr(VI) concentrations, respectively. Transcriptome analyses revealed that multiple metabolic systems are responsible for Cr(VI) resistance at the transcriptional level. In response to Cr(VI) exposure, strain AN-B15 up-regulated the genes involved in central metabolism, providing the reducing power by which enzymes (ChrR and azoR) transformed Cr(VI) to Cr(III) in the cytoplasm. Genes involved in the alleviation of oxidative stress and DNA repair were significantly up-regulated to neutralize Cr(VI)-induced toxicity. Additionally, genes involved in organosulfur metabolism and certain ion transporters were up-regulated to counteract the starvation of sulfur, molybdate, iron, and manganese induced by Cr(VI) stress. Furthermore, a hydroponic culture experiment showed that toxicity and uptake of Cr(VI) by plants under Cr(VI) stress were reduced by strain AN-B15. Specifically, strain AN-B15 inoculation increased the fresh weights of the wheat root and shoot by 55.5 % and 18.8 %, respectively, under Cr(VI) stress (5 mg/L). The elucidation of bacterial resistance to Cr(VI) has an important implication for exploiting microorganism for the effective remediation of Cr(VI)-polluted soils