Information on net primary production in tropical forests is needed for the development of realistic global carbon budgets, for projecting how these ecosystems will be affected by climatic and atmospheric changes, and for evaluating eddy covariance measurements of tropical forest carbon flux. However, a review of the database commonly used to address these issues shows that it has serious flaws. In this paper we synthesize the data in the primary literature on NPP in old-growth tropical forests to produce a consistent data set on NPP for these forests. Studies in this biome have addressed only a few NPP components, all aboveground. Given the limited scope of the direct field measurements, we sought relationships in the existing data that allow estimation of unmeasured aspects of production from those that are more easily assessed. We found a predictive relationship between annual litterfall and aboveground biomass increment. For 39 diverse tropical forest sites, we then developed consistent, documented estimates of the upper and lower bounds around total NPP to serve as benchmarks for calibrating and validating biogeochemical models with respect to this biome. We developed these estimates based on existing field measurements, current understanding of aboveground consumption and biogenic volatile organic carbon emissions, and our judgment that belowground production is bounded by the range 0.2-1.2 ϫ ANPP (aboveground NPP). Across this broad spectrum of tropical forests (dry to wet, lowland to montane, nutrient-rich to nutrient-poor soils), our estimates of lower and upper bounds on total NPP range from 1.7 to 11.8 Mg C·ha Ϫ1 ·yr Ϫ1 (lower bounds) and from 3.1 to 21.7 Mg C·ha Ϫ1 ·yr Ϫ1 (upper bounds). We also showed that two relationships that have been used for estimating NPP (the Bray-Gorham relationship based on leaf litterfall and the Miami model based on temperature or precipitation) are not valid for the tropical forest biome.

Because of the water swelling of graphene oxide (GO) membranes, the rejection of metal ions is generally low, especially for monovalent metal cations. We prepared a thermally reduced graphene (TrGO) membrane with excellent separation performance of water and NaCl by heat treating GO membranes. Its blocking ability for Na+ is 1529 times larger than that of the GO membrane with the same amount of GO, and it is also much better than the reduced GO membranes prepared by NH3 or HI reduction. Using 3 M sucrose as the draw solution, the 795 nm thick TrGO membrane has an ultrahigh rejection of more than 99.56% for Na+ and maintains a water flux of 0.42 L m–2 h–1. TrGO membranes maintain high stability during the penetration of a high-concentration salt solution, and they have good mechanical properties to maintain operational stability and can be used for a longer time. We characterized and analyzed the separation mechanism of the TrGO membranes and believe that the inner channels form three zones with different hydrophobicity and uniform distribution. The ratio of the three zones can be changed by adjusting the heat-treatment temperature, the duration to swelling force, and the π–π attraction force.

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