| 1. |
- Yu, ChaoQing, et al.
(author)
-
Managing nitrogen to restore water quality in China
- 2019
-
In: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 567:7749, s. 516-520
-
Journal article (peer-reviewed)abstract
- The nitrogen cycle has been radically changed by human activities(1). China consumes nearly one third of the world's nitrogen fertilizers. The excessive application of fertilizers(2,3) and increased nitrogen discharge from livestock, domestic and industrial sources have resulted in pervasive water pollution. Quantifying a nitrogen 'boundary'(4) in heterogeneous environments is important for the effective management of local water quality. Here we use a combination of water-quality observations and simulated nitrogen discharge from agricultural and other sources to estimate spatial patterns of nitrogen discharge into water bodies across China from 1955 to 2014. We find that the critical surface-water quality standard (1.0 milligrams of nitrogen per litre) was being exceeded in most provinces by the mid-1980s, and that current rates of anthropogenic nitrogen discharge (14.5 +/- 3.1 megatonnes of nitrogen per year) to fresh water are about 2.7 times the estimated 'safe' nitrogen discharge threshold (5.2 +/- 0.7 megatonnes of nitrogen per year). Current efforts to reduce pollution through wastewater treatment and by improving cropland nitrogen management can partially remedy this situation. Domestic wastewater treatment has helped to reduce net discharge by 0.7 +/- 0.1 megatonnes in 2014, but at high monetary and energy costs. Improved cropland nitrogen management could remove another 2.3 +/- 0.3 megatonnes of nitrogen per year-about 25 per cent of the excess discharge to fresh water. Successfully restoring a clean water environment in China will further require transformational changes to boost the national nutrient recycling rate from its current average of 36 per cent to about 87 per cent, which is a level typical of traditional Chinese agriculture. Although ambitious, such a high level of nitrogen recycling is technologically achievable at an estimated capital cost of approximately 100 billion US dollars and operating costs of 18-29 billion US dollars per year, and could provide co-benefits such as recycled wastewater for crop irrigation and improved environmental quality and ecosystem services.
|
|
| 2. |
- Lin, Li'na, et al.
(author)
-
GEOCHRONOLOGIC AND GEOCHEMICAL EVIDENCE FOR PERSISTENCE OF SOUTH-DIPPING SUBDUCTION TO LATE PERMIAN TIME, LANGSHAN AREA, INNER MONGOLIA (CHINA) : SIGNIFICANCE FOR TERMINATION OF ACCRETIONARY OROGENESIS IN THE SOUTHERN ALTAIDS
- 2014
-
In: American Journal of Science. - : American Journal of Science (AJS). - 0002-9599 .- 1945-452X. ; 314:2, s. 679-703
-
Journal article (peer-reviewed)abstract
- The Langshan area in Inner Mongolia is situated in the southern Altaids between the Beishan suture to the west and the Solonker suture to the east. This paper addresses the poorly known tectonic evolution that led to formation of the terminal Solonker suture. Dating of deformed porphyries and undeformed dolerites and gabbros constrains the timing of the relevant NE-E-striking and north-vergent deformation. Deformed granitic-granodioritic porphyries in this area are characterized by high SiO2 (65.38-78.00%), low TFe2O3 (1.29-5.07%), MgO (0.13-0.63%), and variable K2O (0.534.14%) and Na2O (2.05-4.62%). All samples have enriched LREE (La/Yb 6-18) and negative Nb anomalies (Nb-N/Th(N)0.09-0.48), but different Eu anomalies (Eu* <0.7 or similar to 1); these geochemical features can be ascribed to a heterogeneous source in a subduction-related environment. Gabbros and dolerites have 42.33 to 52.03 percent SiO2. All mafic samples have similar La/Yb ratios of 4 to 6 and negative Nb anomalies (Nb-N/Th-N) ratios of 0.2 to 0.8, suggestive of a subduction-related setting. Two granitic porphyries yielded U-238/Pb-206 weighted mean ages of 284.7 +/- 2.1 Ma with MSWD of 1.6 and 291.7 +/- 2: 2.1 Ma with MSWD of 1.14; these ages are consistent with U-235/Pb-207 and U-238/Pb-206 concordia ages of 281 +/- 17 Ma with MSWD of 0.87 and 289.8 +/- 9.2 Ma with MSWD of 0.66. A dolerite yielded concordia ages of 256.2 +/- 2.6 Ma with MSWD of 0.44 and 256 +/- 2.5 Ma with MSWD 0.45. The ages and geochemistry of the deformed porphyries indicate that in the early Permian there was important deformation and recrystallization in a subduction-related setting. The isotopic and geochemical signatures of all the rocks indicate that they formed during subduction-related conditions. We propose that Langshan was a Permian active continental margin arc built on the edge of the North China Craton by southward subduction, which led to closure of the ocean, concomitant formation of the Solonker suture in the late Permian-early Triassic, and termination of the accretion-subduction orogen of the southern Altaids.
|
|
