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Responses of organic phosphorus fractionation to environmental conditions and lake evolution Changwei Lü, Bing Wang, Jiang He, Rolf David Vogt, Bin Zhou, Rui Guan, Le Zuo, Weiying Wang, Zhilei Xie, Jinghua Wang, and Daohao Yan Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.5b05057 • Publication Date (Web): 22 Apr 2016 Downloaded from http://pubs.acs.org on April 24, 2016
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Environmental Science & Technology
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Responses of organic phosphorus fractionation to environmental conditions and lake evolution *
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Changwei Lü1, 2, 3, ∗, Bing Wang4, Jiang He1, 2, *, Rolf D. Vogt3, Bin Zhou3, 5, Rui Guan1, Le Zuo1, Weiying Wang1, Zhilei Xie1, Jinghua Wang1, Daohao Yan1
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1. College of Environment and Resources, Inner Mongolia University, Huhhot 010021, China.
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2. Institute of Environmental Geology, Inner Mongolia University, Huhhot 010021, China.
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3. Department of Chemistry, University of Oslo, N-0315, Norway.
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4. Forestry College, Inner Mongolia Agricultural University, Huhhot 010019, China.
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5. Tianjin Academy of Environmental Sciences, Tianjin, 300191, China.
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Abstract
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Geochemical fractionation is used to assess the significance of environmental factors on
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organic phosphorus (OP) pools in sediments. Labile, moderately labile and non-labile OP
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pools in the sediments from Lake Hulun, Inner Mongolia, were fractionated, and their
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responses to environmental conditions and lake evolution were investigated based on the
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spatial and vertical distribution of OP fractionations. In light of the recalcitrant characteristics
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of organic matter (OM) in different environmental conditions, the pH presents significant
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negative effects on amount of labile OP, while water depth shows important role in regulating
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the distribution between the moderately- and non-labile OP pools. A latitudinal zonation in
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the distribution of OP pools in surface sediments from different lakes was apparent with this
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zonation likely linked to the gradient effects of climate and anthropogenic activities on OM
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decomposition and thereby on the sediments capacity to hold phosphorous. These results
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show that OM plays a role in governing the impacts of weather and environmental factors on
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OP fractionation in aquatic environments. This work suggests that OP pools in sediment core
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could be used as an archive for the environmental conditions and lake evolution.
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Key words: organic phosphorus, fractionation, response, environmental conditions, lake
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evolution
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Corresponding author, Email:
[email protected],
[email protected] Tel:+86-471-4992210 Fax: +86-471-4992210 1
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Graphic Abstract 29
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Introduction
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Phosphorus (P), being a major growth limiting nutrient in the biosphere, usually plays a key
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role in governing the biological productivity of aquatic ecosystems.1 Eutrophication due to
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elevated P inputs to the aquatic environment therefore increases the risk of algae blooms and
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impact on water quality. Emphasis for many decades has been on the study of P
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fractionation,2, 3 allowing assessments of not only the abundance of P, but also the potential
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for transformation and bioavailability of P pools,4-6 and thereby better assessment of its
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impact on eutrophication through internal cycling.7,
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dissolved or particulate organic phosphorus (OP) is found to be of similar magnitude as
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inorganic P.9 Moreover, the OP is recently conceived as a potential pool for bioavailable P,
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spurring much research regarding OP decomposition,10,
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characterization of OP compounds using
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spectroscopy.14-18 These studies have enhanced our awareness of the abundance of OP
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In many waters and sediments,
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fractionation9,
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and
P nuclear magnetic resonance (NMR)
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fraction and understanding of their role in the environment.
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The pool of natural organic matter (OM) and OP are usually correlated in sediment
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environment. This is conceptually expected as OP is an inherent part of the OM pool. The
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amount of natural OM is in turn governed by the effects of environmental factors, such as
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climate change and/or anthropogenic activities in the environment.19-21 Vertical concentration
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profiles of total organic carbon (TOC), especially allochthonous OC (Allo-OC), in lacustrine
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sediments can therefore be used as a tool to reconstruct the paleo-environment and
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paleo-climate of lake basins.8, 19, 22, 23 Accordingly, the concentration and composition of OP
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pools in lake sediments are expected to be influenced by environmental factors, such as
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climate change, terrestrial inputs, and key explanatory parameters such as pH. Knowledge
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regarding the distribution of OP pools is therefore important in order to understand the burial,
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diagenesis, bioavailability and environmental geochemical significance of OP in sediments.
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Historical distribution and partitioning of phosphorus in sediment profile archived the
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information of pressure from environment, climate and anthropogenic activities.24 The
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biogeochemical processing and accumulation of P in the surface sediment are completely
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different from that in the depth layer. The current phosphorus status in surface sediments
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from different lakes may mainly response to the pressure of anthropogenic activities and the
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difference of environment and climate in the lake basin, while environment and climate
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conditions are the dominate factors to control the OP changes in the depth layer due to the
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fact of the high intensity of the anthropogenic input (e.g. phosphorus fertilizer ) in the recent
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50 years, and much low input in the past. Previous studies have mainly regarded the size of
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OP pools and its specific compounds in surface sediments/soils. So far there have been no
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publications describing the relationship of the vertical distribution of OP pools in sediments
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with the water depth, lake area, and the salinity, as influenced by changes in the environment
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and climate. The objects of this study were to (1) determine the size of OP pools by
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sequential extraction in sediments collected from Lake Hulun, China, and (2) discuss the
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responses of OP pools in sediment profile to the historical evolution of Lake Hulun on the
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basis of quantificational reconstruction of lake level, area and salinity over the past 4000
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years. These findings are then compared to (3) an assessment of regional factors revealing the
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main governing factors explaining the distribution of OP pools in surface sediments from 13 3
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Chinese lakes.
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Material and Methods
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Study Area
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Lake Hulun is located in northeastern Inner Mongolia, China. This is at the northeastern
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corner of the monsoon margin, and thus sensitive to small variations in the East Asian
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monsoon.25, 26 The highly variable climate is generally arid with an annual mean precipitation
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of 290 mm, of which three-fifths falls between July and August, an annual mean theoretical
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evaporation of 1600 mm, and an annual mean air temperature of -0.2°C. It once was the fifth
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largest lake in China with an area of 2339 km2 and an average depth of 5.7 m. During the last
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35-50 years the lake has experienced a dramatic reduction in its size and water depth due to
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climate change and human activities in the drainage area and rivers. In 2011, its area had
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shrank to 1770 km2 with a mean depth of 3.0-3.5 m. Two major permanent rivers, the Herlun
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(Kerulen or Kelulun) and Urshen (Orxon or Orshun), feed the lake from the southwest and
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east, respectively (Figure 1). The Dalanolom River, connected to the lake in the northeast,
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used to be an intermittent river. Since 1971 this river has been a channel used for water
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exchange between Lake Hulun and the Hailaer River. For most of the year, however, the
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water is stagnant and, occasionally, when its level is lower than 545.1m, there is a reverse
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flow of waters into the lake.27
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Figure 1 Locations of the 13 studied lakes in China and sampling sites in Lake Hulun Note: HLH: Lake Hulun, QL: Lake Qilu, EH: Lake Erhai, HF: Lake Hongfeng, CHH: Lake Chenghai, BH: Lake Baihua, LG: Lake Lugu, CH: Lake Chaohu, QHH: Lake Qinghai, WLSH: Lake Wuliangsuhai, WDL: Lake Wudalianchi, JP: Lake Jingpo, TH: Lake Taihu (including bays of Gonghu, Meiliang and Yuantouzh) 91 92
The size of OP pools in sediments from Lake Hulun and Wuliangsuhai were determined
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in this work, while data for OP pools from other Chinese lakes are compiled from previous
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publications28,
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located in the Yangtze River region,28 the Southwestern China Plateau,28 the Tibetan
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plateau,29 the Inner Mongolia-Xinjiang plateau and Northeast China Region,29 spanning a
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wide latitudinal gradient (see Figure 1 and Supporting Information (SI) Table S5).
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Sediment Sampling
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Sediments from Lake Hulun were sampled in August 2011. The surface sediments (0-10cm)
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were collected from 31 sites using a KC collector mod B (Swedaq), while a 80 cm sediment
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core was collected from the center of the lake (HLH15, Figure 1) using a SA Beeker collector
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equipped with vacuum membrane mounted on hand held rods (Eijkelkamp). The sediment
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in order to make a comparative study. The other 13 selected lakes are
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core was sectioned into 2-cm slices immediately after collection, stored in sealed
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polyethylene bags which were put in transport iceboxes (
