Factors controlling phosphorus export from agricultural/forest and residential systems to rivers in eastern China, 1980–2011

Abstract

s u m m a r yThis study quantified long-term response of riverine total phosphorus (TP) export to changes in land-use, climate, and net anthropogenic phosphorus inputs to agricultural/forest (NAPI AF ) and residential (NAPI R ) systems for the upper Jiaojiang watershed in eastern China. Annual NAPI AF rose by 73% in 1980-1999 followed by a 41% decline in 2000-2011, while NAPI R continuously increased by 122% over the 1980-2011 period. Land-use showed a 63% increase in developed land area (D%) and a 91% increase in use of efficient drainage systems on agricultural land area (AD%) over the study period. Although no significant trends were observed in annual river discharge or precipitation, the annual number of storm events rose by 90% along with a 34% increase in the coefficient of variation of daily rainfall. In response to changes of NAPI AF , NAPI R , land-use and precipitation patterns, riverine TP flux increased 16.0-fold over the 32-year record. Phosphorus export via erosion and leaching was the dominant pathway for P delivery to rivers. An empirical model incorporating annual NAPI AF , NAPI R , precipitation, D%, and AD% was developed (R 2 = 0.96) for apportioning riverine TP sources and predicting annual riverine TP fluxes. The model estimated that NAPI AF , NAPI R and legacy P sources contributed 19-56%, 16-67% and 13-32% of annual riverine TP flux in 1980-2011, respectively. Compared to reduction of NAPI AF , reduction of NAPI R was predicted to have a greater immediate impact on decreasing riverine TP fluxes. Changes in anthropogenic P input sources (NAPI AF vs. NAPI R ), land-use, and precipitation patterns as well as the legacy P source can amplify P export from landscapes to rivers and should be considered in developing P management strategies to reduce riverine P fluxes.

Deteriorated Water Quality of Agricultural Catchments in South China by Net Anthropogenic Phosphorus Inputs

“…The percentage of riverine exports of NAPI ranged from 2.3 to 7.9%. This estimation consistent with previous studies in the America, Europe, and China (1-14%; [4,7,29]), suggesting that the major part of cumulative NAPI was retained in cropland soils [11,30]. In this study, soil TP and Olsen-P contents exhibited a linear positive correlation with NAPI c .…”

“…To more clearly attribute NAPI to particular anthropogenic activities and land uses, the NAPI was divided into two components: cropland and residential land (Figure 2). Cropland (NAPIc, kg P ha −1 year −1 ) and residential land (NAPIr, kg P ha −1 year −1 ) budget estimations were modified from the standard NAPI method [4,11]:…”

Legacy Nutrient Dynamics at the Watershed Scale: Principles, Modeling, and Implications

“…As indicated in many case studies worldwide, several years to decades will be required to drawdown the legacy N and P stores in soils, sediments, vadose zone, and groundwater via crop uptake, hydrological loss, and gaseous removal, even if new anthropogenic N and P inputs were totally eliminated (Chen et al, 2014a(Chen et al, , 2016bHowden et al, 2011;Sharpley et al, 2013;Van Meter et al, 2016;Withers and Bhadeshia, 2001). Previous studies suggest that legacy nutrients from past anthropogenic inputs present a large and potentially long-term source of nutrients to receiving waters, as well as a potentially important nutrient source for future crop production that could reduce reliance on inorganic fertilizers.…”

“…(3%-6%) in residential landscapes Chen et al (2016b) zone and groundwater is the major N loss form, and subsurface flow and groundwater recharge are the major loss pathways for legacy N loss; and (v) anthropogenic (e.g., land use, dam/reservoir development or removal, and cropland management measures) and natural (e.g., precipitation, storm events, and climate change) disturbances can enhance legacy nutrient release and loss by influencing hydrological and biogeochemical processes.…”

Impacts of land use and population density on seasonal surface water quality using a modified geographically weighted regression

“…It's particularly apparent in China due to the rapid processes of urbanization and economic development (Chen et al, 2016a(Chen et al, , 2016bMei et al, 2014). Nonpoint source pollution is of great importance due to its prevalence on surface water impairment and the difficulty of identifying specific sources for remediation (Dowd et al, 2008;Zhang et al, 2011;Sun et al, 2013;Huisman et al, 2013).…”