Historic Trends and Future Prospects of Waste Generation and Recycling in China's Phosphorus Cycle.

Intensified human activities have generated a large amount of phosphorus-containing waste (P waste). Unrecycled P waste is lost to the environment and causes eutrophication, while the increasing phosphate consumption risks the depletion of phosphorus resources. The management of P waste is critical to solving these problems. In this study, we quantified the historic trends of P waste generation and recycling in China. From 1900 to 2015, the annual generation of P waste increased from 1 Mt P to 12 Mt P. Crop farming was the largest P waste source in most years, while P waste from phosphate mining and phosphorus chemical production increased the fastest. The total recycled P waste increased 5-fold, but phosphorus loss increased 26-fold. In 2015, 28% of the P waste was lost on cultivated land, and 21% was lost on nonarable land. The largest phosphorus contributor to inland water changed from crop farming to aquaculture. The full recycling of P waste would have reduced phosphate consumption by more than one-third in 2015. The results of a scenario analysis showed that a healthier diet would greatly increase the generation and loss of P waste, but balanced fertilization could reduce the generation of P waste by 17% and promoting waste recycling could reduce the phosphorus loss by 35%.

Animal based diets and environment: Perspective from phosphorus flow quantifications of livestock and poultry raising in China.

Identifying the key nodes of the phosphorus flows in animal raising system is fundamental to improve P utilization efficiency and reduce the P contamination. This study established a phosphorus flow analysis model for livestock and poultry raising, depicted P flows for major livestock and poultry under two raising modes, and further analyzed their spatial and temporal distributions. We find that around 15% of P input was transferred into the products, and in P output around 40% lost into the environment in 2015. The P flows have been increasing since 2000, and the main contributor is pigs followed by beef cattle. It should be noticed that P loss from livestock and poultry raising is huge with extensive prospect of recycling in some central provinces of China, and western region where ecological environment is fragile, has a higher P loss rate which need to change the dietary preference and adjust raising structure. As for diets, pork and eggs are better choices than milk or other kinds of meat in terms of reducing the P load, when producing per unit protein or energy. This study contributes to the understanding of P management in husbandry industry, the quantification of environmental loads of animal-based food and the identification of the potential of reducing P loss to realize sustainable utilization of P.

Phosphorus footprint in China over the 1961-2050 period: Historical perspective and future prospect.

The phosphorus footprint (PF) is a novel concept to analyze human burdens on phosphorus resources. However, research on PF approach is still limited, and current several PF studies include incomplete phosphorus sources and have limited quantitative interpretation about the drivers of PF changes, which can help understand future trends of PF. This study develops a more comprehensive PF model by considering crop, livestock and aquatic food, and non-food goods, which covers the mainly phosphorus containing products consumed by human. The model is applied to quantify China's PF from 1961 to 2014, and the results of the model are also used to analyze the factors driving the PF changes and explored China's PF scenarios for 2050 using an econometric analysis model (STIRPAT). The result shows that China's PF increased over 11-fold, from 0.9 to 10.6 Tg between 1961 and 2014. The PF of livestock food dominated China's PF, accounting for 57% of the total in 1961 and 45% in 2014. The key factors driving the increase in China's PF are the increase in population and urbanization rate, with contributions of 38% and 33%, respectively. We showed that in the baseline scenario, China's PF would increase by 70% during 2014-2050 and cause the depletion of China's phosphate reserves in 2045. However, in the best case scenario, China's PF would decrease by 15% in 2050 compared with that in 2014, and it would have 50% of current phosphate reserve remaining by 2050. Several mitigation measures are then proposed by considering China's realities from both production and consumption perspective, which can provide valuable policy insights to other rapid developing countries to mitigate the P footprint.

Human Perturbation of the Global Phosphorus Cycle: Changes and Consequences.

The phosphorus (P) cycle is an important Earth system process. While natural P mobilization is slow, humans have been altering P cycle by intensifying P releases from lithosphere to ecosystems. Here, we examined magnitudes of which humans have altered the P cycles by integrating the estimates from recent literatures, and furthermore illustrated the consequences. Based on our synthesis, human alterations have tripled the global P mobilization in land-water continuum and increased P accumulation in soil with 6.9 ± 3.3 Tg-P yr-1. Around 30% of atmospheric P transfer is caused by human activities, which plays a significant role than previously thought. Pathways involving with human alterations include phosphate extraction, fertilizers application, wastes generation, and P losses from cropland. This study highlights the importance of sustainable P supply as a control on future food security because of regional P scarcity, food demand increase and continuously P intensive food production. Besides, accelerated P loads are responsible for enhanced eutrophication worldwide, resulting in water quality impairment and aquatic biodiversity losses. Moreover, the P enrichment can definitely stimulate the cycling of carbon and nitrogen, implying the great need for incorporating P in models predicting the response of carbon and nitrogen cycles to global changes.

Intensification of phosphorus cycling in China since the 1600s.

Phosphorus (P) is an essential nutrient for living systems with emerging sustainability challenges related to supply uncertainty and aquatic eutrophication. However, its long-term temporal dynamics and subsequent effects on freshwater ecosystems are still unclear. Here, we quantify the P pathways across China over the past four centuries with a life cycle process-balanced model and evaluate the concomitant potential for eutrophication with a spatial resolution of 5 arc-minutes in 2012. We find that P cycling in China has been artificially intensified during this period to sustain the increasing population and its demand for animal protein-based diets, with continuous accumulations in inland waters and lands. In the past decade, China's international trade of P involves net exports of P chemicals and net imports of downstream crops, specifically soybeans from the United States, Brazil, and Argentina. The contribution of crop products to per capita food P demand, namely, the P directly consumed by humans, declined from over 98% before the 1950s to 76% in 2012, even though there was little change in per capita food P demand. Anthropogenic P losses to freshwater and their eutrophication potential clustered in wealthy coastal regions with dense populations. We estimate that Chinese P reserve depletion could be postponed for over 20 y by more efficient life cycle P management. Our results highlight the importance of closing the P cycle to achieve the cobenefits of P resource conservation and eutrophication mitigation in the world's most rapidly developing economy.

Phosphorus Flow Patterns in the Chaohu Watershed from 1978 to 2012.

Understanding historical patterns of phosphorus (P) cycling is critical for sustainable P management and eutrophication mitigation in watersheds. This study built a bottom-up model using the substance flow analysis approach to quantify P cycling in the Chaohu watershed during 1978-2012. We found that P flows have been intensified, with a 5-fold increase of annual P inputs to sustain the expanding intensive agriculture. Annually, most P inputs (75%) were stored within the watershed, which caused accelerating buildup of legacy P in cultivated land (from 4.9 Gg to 6.5 × 10(2) Gg), uncultivated land (from 2.1 Gg to 1.3 × 10(2) Gg) and surface water (from 3.7 Gg to 2.6 × 10(2) Gg) during 1978-2012. The main legacy P sources include fertilizer application for cultivated land, phosphogypsum abandonment for uncultivated land, respectively. The animal husbandry contributed about 63-66% of total P inputs to surface water. The contribution of animal food-P increased greatly during 1978-2012, from 7% to 24% and from 1% to 8% for urban and rural residents, respectively. This work demonstrates principle for the buildup of legacy P at the watershed-scale, and advances the knowledge of sustainable P management, such as improving agricultural technologies to reduce fertilizer application.

Black soybean seed coat polyphenols prevent B(a)P-induced DNA damage through modulating drug-metabolizing enzymes in HepG2 cells and ICR mice.

Black soybean seed coat is a rich source of polyphenols that have been reported to have various physiological functions. The present study investigated the potential protective effects of polyphenolic extracts from black soybean seed coat on DNA damage in human hepatoma HepG2 cells and ICR mice. The results from micronucleus (MN) assay revealed that black soybean seed coat extract (BE) at concentrations up to 25µg/mL was non-genotoxic. It is noteworthy that BE (at 4.85µg/mL) and its main components, procyanidins (PCs) and cyanidin 3-glucoside (C3G), at 10µM significantly reduced the genotoxic effect induced by benzo[a]pyrene [B(a)P]. To obtain insights into the underlying mechanism, we investigated BE and its main components on drug-metabolizing enzyme expression. The results of this study demonstrate that BE and its main components, PCs and C3G, down-regulated B(a)P-induced cytochrome P4501A1 (CYP1A1) expression by inhibiting the transformation of aryl hydrocarbon receptor. Moreover, they increased expression of detoxifying defense enzymes, glutathione S-transferases (GSTs) via increasing the binding of nuclear factor-erythroid-2-related factor 2 to antioxidant response elements. Collectively, we found that PCs and C3G, which are the main active compounds of BE, down-regulated CYP1A1 and up-regulated GST expression to protect B(a)P-induced DNA damage in HepG2 cells and ICR mice effectively.