Global environmental change places unavoidable pressure on water resources and agronomic crop production systems. Irrigation development is a credible measure to alleviate the challenge of food safety under water shortages, but it needs sufficient basis. The aim of this study is to address the problem of balancing water scarcity with food requirements, which are the key components of water security in regions with population growth. Marginal water productivity (MWP) indices for irrigation water performance and productivity evaluation were established in the current study. Based on the analysis of the regional water-crop relationship and spatial differences of MWP in China, the priorities for developing irrigation areas in different types of regions are discussed in this study. The results show that high MWPs are mainly in semi-arid regions with precipitation (P) between 500 and 1000 mm, while low MWPs mostly occur in areas with P more than 1000 and less than 500 mm. The significance and spatial distribution patterns of MWP are different than those of conventional irrigation water use efficiency evaluation indices, so its role cannot be replaced for the real production capacity of irrigation water evaluation. The strategies for global environmental change adaptation suggested in this study are taking MWP for irrigation water productivity evaluation and the priority irrigation schemes for agronomic crop determination; increasing MWP by means of irrigation efficiency and crop variety improvement worldwide; and raising global food production through the expansion of irrigation area in the regions hold high MWP and abundant water resources.
Treatment of oilfield produced water was investigated using an anaerobic process coupled with micro-electrolysis (ME), focusing
on changes in chemical oxygen demand (COD) and biodegradability. Results showed that COD exhibited an abnormal change in
the single anaerobic system in which it increased within the first 168 hr, but then decreased to 222 mg/L after 360 hr. The biological
oxygen demand (five-day) (BOD5)/COD ratio of the water increased from 0.05 to 0.15. Hydrocarbons in the wastewater, such as pectin,
degraded to small molecules during the hydrolytic acidification process. Comparatively, the e ect of ME was also investigated. The
COD underwent a slight decrease and the BOD5/COD ratio of the water improved from 0.05 to 0.17 after ME. Removal of COD was
38.3% under the idealized ME conditions (pH 6.0), using iron and active carbon (80 and 40 g/L, respectively). Coupling the anaerobic
process with ME accelerated the COD removal ratio (average removal was 53.3%). Gas chromatography/mass spectrometry was used
to analyze organic species conversion. This integrated system appeared to be a useful option for the treatment of water produced in
oilfields. 相似文献
Adsorption and degradation of levonorgestrel (LNG) by two hydrophytes, Cyperus alternfolius (CA) and Eichhornia crassipes (EC), were investigated under light-shielding conditions in the water column. Variations of LNG concentrations in water, plant root epidermis, root, stem and leaf of the plants were analyzed. The results indicated that the removal efficiency of LNG by hydrophytes over the period of 50 days was significantly greater than the blank control (p 〈 0.05), with the removal rates of 79.80%± 3.10% and 78.86% ± 2.55% for CA and EC, respectively. Compared with bio-adsorption, bio-conversion of LNG was found to be the dominant elimination pathway, evidenced by relatively high conversion rates (77.31% ±2.68% for CA and 77.82% ± 2.95% for EC), while the adsorption rates were lower (1.77% ± 0.90% for CA and 1.05% ± 0.40% for EC). The bio-adsorption and conversion of LNG showed no significant differences between the two hydrophytes. Additionally, the mineralization on root epidermis played an important role in the reduction of LNG in water. 相似文献