Supporting Information
Total Page:16
File Type:pdf, Size:1020Kb
1 Supporting Information 2 Intensification of phosphorus cycling in China since the 1600s 3 1 Temporal pattern of phosphorus cycle in China 4 We use the substance flow analysis (SFA) method (1, 2), which is based on the mass 5 balance principle, to depict phosphorus (P) cycle within China over the last four 6 centuries. This systematic approach has been widely applied to characterize 7 anthropogenic cycles of elements at different geographical scales based on static 8 analyses, reflecting part of elemental flows at a specific time point (3). In this study, we 9 take account of both major natural and anthropogenic activities to characterize the entire 10 P cycle over a time interval of over 400 years. 11 1.1 System boundaries 12 The geographical boundaries of this study are the territory area of China, excluding Hong 13 Kong, Macao and Taiwan. It is due to limited data availability since these regions were 14 once colonies of other countries for certain periods and are now under local jurisdictions. 15 The temporal scale is defined as 1600s-2012 for the following reasons: 1) Population in 16 China began to increase significantly since the 1600s (hereinafter referred to as a decade). 17 2) Around the 1600s, foreign crop types including maize and tubers were introduced into 18 China and thereafter the cropping systems in traditional agriculture became consistent 19 with the present situations. 3) In earlier times, human intervention was generally weaker 20 and P cycle was more stable as compared to nowadays. Possible natural calamities and - 1 - 21 human disasters that could cause change in P cycles have relatively low occurrence 22 frequencies (less than once per century). 4) The availability and reliability of data. 23 This study covers the past four centuries that witness the rise and fall of several Chinese 24 dynasties (4, 5), starting from the traditional Chinese society of agricultural base during 25 the 1600s when 120 million population were under the governance of the glorious Ming 26 Dynasty. The Ming regime deteriorated due to long periods of wars with other nations, 27 increasing power of eunuchs and continuous famine, and was finally taken over by the 28 Qing nomadic people from northeast China in the 1640s, when the domestic population 29 rapidly declined to less than 100 million. The multi-cultural Qing Empire dominated for 30 almost three centuries and boosted the national population to over 400 million at the 31 beginning of 1900s. The dramatic rise in population could be attributed to two reasons, 32 namely the long period of peaceful and stable regime in the 18th century and the 33 successful cultivation of new types of crops from America, such as peanuts, tubers and 34 maize. However, more and more social conflicts had emerged since the 1840s when the 35 First Opium War broke out. Although revolutionary measures were taken to save the 36 dying Qing Dynasty, it was eventually overthrown in 1911, which ended two thousand 37 years of Chinese feudal monarchy. China then shortly stayed in the turbulent Republican 38 Era (1912-1948), during which regimes waxed and waned through regional militarism 39 (1912-1927), the prosperous Nanjing Decade (1928-1937), the Second Sino-Japanese 40 War (1938-1945) and post-war rehabilitation (1946-1948). Ever since the Chinese 41 Communist Party took power in 1949, the national economy has developed speedily and 42 the living conditions have been greatly improved, especially after the economic reform 43 and opening-up policy in the late 1970s. - 2 - 44 1.2 Hierarchy of the Chinese phosphorus cycle model 45 The P biogeochemical cycle consists of P flows through different environmental media 46 and human interventions. Naturally, P is absorbed by biota through atmospheric 47 deposition, weathering and erosion, and finally becomes submarine sediments after river 48 transportation. It usually takes tens of millions years of tectonic uplift until it can be used 49 again. However, the increase of human populations and their demands for food have 50 accelerated P cycling. P rocks are mined and produced into various P-associated chemical 51 products to sustain plants, animals and human beings. 52 In this study, a total of fourteen major compartments are identified throughout P lifetime 53 metabolic process within the Chinese territory and denoted with Ni (i=1,…, 14, Fig. S2) 54 (6). The natural compartments include atmosphere (N1), non-arable land (N2), inland 55 waters (N3), and marine waters (N4). Anthropogenic P flows go through mining (N5), 56 chemical production (N6), cultivation (N7), animal husbandry (N8), aquaculture (N9), 57 agricultural product processing (N10), human consumption (N11), wastewater treatment 58 (N12) and solid waste disposal (N13). P-containing commodities are imported or exported 59 through international trade (N14). 60 Atmosphere (N1) is defined as the atmospheric boundary layer, the lowest part of the 61 atmosphere that is usually around 1 kilometer (km) deep, since its behavior is directly 62 influenced by the contact with the ground surface within China’s territory. The air above 63 this layer, in which the large-scale atmospheric circulation happens, is excluded because 64 of the negligible effect of the earth's surface. - 3 - 65 Non-arable land (N2) is the part of the terrestrial land of China which cannot be used for 66 arable farming, including forest, grassland, construction land and unused land. However, 67 some non-arable land can be turned into arable land with advanced agricultural 68 techniques, such as installing irrigation facilities. 69 Inland waters (N3) primarily refer to a variety of freshwaters that are located within 70 China’s land boundaries, including rivers, lakes, reservoirs, wetlands and other water 71 storage systems. On the contrary, marine waters (N4) include seas and oceans under the 72 jurisdiction of China. Fishing in the inland and marine waters can catch natural aquatic 73 products, including fish, shrimp, crab, shell, seaweed, etc. 74 Mining (N5) is determined as the economic extraction of phosphate rocks from the 75 lithosphere, while P contained in other mineral resources, such as fossil fuels and metals 76 where P is regarded as impurities, is not taken into account. Mining can be further 77 divided into two sub-compartments: mining (N5.1) and beneficiation (N5.2). Raw P ores 78 are mined from lithosphere containing different amounts of phosphorus pentoxide (P2O5). 79 Phosphate rocks with the grade of P2O5 over 30% can be directly exported or used by P 80 chemical industries (N6), while the others need to go through beneficiation to increase the 81 grade of P2O5. 82 Chemical production (N6) includes the primary consumption activities of phosphate 83 rocks, namely fertilizer production (N6.1), feed additive production (N6.2), and elemental P 84 production (N6.3), while less than 10% of the mined phosphate rocks are used for other 85 purposes and not considered in this study. Elemental P is further utilized as the raw 86 material to produce various P containing chemicals with different manufacturing - 4 - 87 techniques, production scales and pollution levels. Although China holds a dominant 88 position in the international market of fine phosphorus chemical products, this study 89 considers only two important applications in detail, namely to produce organophosphate 90 pesticides (N6.3.1) and synthetic detergents (N6.3.2), where high amounts of elemental P are 91 consumed and P-containing wastes are generated. Elemental P used to produce other 92 various types of P for metal-surface treatments, steel production, wastewater treatment, etc. 93 or as flame retardants, plasticizers, food and feed additives, etc. is simplified as an input to 94 other chemicals (N6.3.3) but not further expanded in this study mainly because of its 95 relatively small contributions to the total P input and data limitation as well. 96 Cultivation (N7) in this study refers to the crop cultivation activities in the arable land of 97 China. Arable land is the land actually being cultivated to grow crops, including the area 98 of land with crop harvests, fallows, newly reclaimed land and abandoned land area within 99 three years. The upper soil layer (20 cm) is considered to be part of the cultivation 100 compartment since it is the ploughing depth where plants take up nutrients (7). Crop 101 categories include grains (rice, wheat, maize, millet, sorghum, etc.), beans, tubers, cotton 102 fibers and seeds, oil crops (peanut, rapeseed, sesame, sunflower, etc.), bast fibers, 103 sugarcane, sugar beet, tobacco and vegetable. 104 Animal husbandry (N8) here refers to the care and breeding of terrestrial animals, 105 including pig, cattle, sheep, poultry, horse, mule, donkey and rabbit, with no 106 differentiation of the feeding manners and waste disposals between household and 107 industrial livestock production. Aquaculture (N9) involves cultivating freshwater and 108 saltwater products (fish, shrimp and crabs) under controlled conditions in the inland and 109 marine waters, contrasting with the harvests of natural aquatic products through fishing. - 5 - 110 Agricultural product processing (N10) considers two major activities that demand for 111 harvested agricultural products, namely food processing (N10.1) and feed processing 112 (N10.2), whereas all the other less critical utilizations are simplified in compartment N10.3. 113 It should be noted that this study does include the food processing stage by covering the 114 first stage of processing of crops (husking, flouring, etc.) and animals (slaughtering). 115 However, the higher stages of processing are excluded due to the unavailability of 116 detailed production data for various forms of processed products. 117 Human consumption (N11) represents a group of human activities that residents consume 118 P-containing products and produce a multitude of wastes and wastewater. Due to rural 119 and urban residents’ discrepancy in consumer behaviors as well as waste disposal, we 120 analyze rural and urban households separately.