Demand for hydropower is increasing, yet the water footprints (WFs) of reservoirs and hydropower,
and their contributions to water scarcity, are poorly understood. Here, we calculate reservoir WFs
(freshwater that evaporates from reservoirs) and hydropower WFs (the WF of hydroelectricity) in
China based on data from 875 representative reservoirs (209 with power plants). In 2010, the
reservoir WF totaled
27.9 × 109 m3 (Gm3),
or 22% of China’s total water consumption. Ignoring the reservoir WF seriously
underestimates human water appropriation. The reservoir WF associated with industrial, domestic and
agricultural WFs caused water scarcity in 6 of the 10 major Chinese river basins from 2 to 12 months
annually. The hydropower WF was 6.6 Gm3 yr−1 or
3.6 m3 of water to produce a GJ (109 J) of
electricity. Hydropower is a water intensive energy carrier. As a response to global climate change,
the Chinese government has promoted a further increase in hydropower energy by 70% by 2020 compared
to 2012. This energy policy imposes pressure on available freshwater resources and increases water
scarcity. The water-energy nexus requires strategic and coordinated implementations of hydropower
development among geographical regions, as well as trade-off analysis between rising energy demand
and water use sustainability.
Nanopores have become
one of the most important tools for single-molecule
sensing, but the challenge for selective detection of specific biomolecules
still exists. In this contribution, we develop a new technique for
sensing carcinoembryonic antigen (CEA), one of the important cancer
biomarkers, using solid-state nanopores as a tool. The method is based
on the specific affinity between aptamer (Apt) modified magnetic Fe3O4–Au nanoparticles (MNPs) and CEA, and
the formed CEA–Apt–MNPs and remaining Apt–MNPs
can transport the nanopores by applying a positive potential after
magnetic separation. Due to the obvious particle size difference between
CEA–Apt–MNPs and Apt-MPs, their corresponding blockage
signals could be distinguished completely by the degree of the current
decline. Moreover, the frequency of the blockage signals for CEA–Apt–MNPs
is proportional to the concentration of CEA within certain limits,
indicating that our designed nanopore sensing strategy can quantitatively
detect CEA in complex samples. This work demonstrates that our designed
nanopore-based strategy can be used for CEA sensing with good selectivity
and sensitivity and also can be used to analyze other protein biomarkers
for early diagnosis and monitoring of cancer, though the detection
limit (0.6 ng/mL) is not relatively low. In future works, we plan
to improve our detection limit by the improvement of the nanopipette
preparation technology and detection method.
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