Seasonal variation of nitrogen and phosphorus in Xiaojiang River—A tributary of the Three Gorges Reservoir

A yearlong monitoring program in the backwater area of Xiaojiang River (XBA) was launched in order to investigate the eutrophication of backwater areas in tributaries of the Yangtze River in the Three Gorges Reservoir (TGR) in China, starting after the impoundment water level of the TGR reached 156 m. From March 2007 to March 2008, the average concentration of total nitrogen (TN) and total phosphorus (TP) were (1553±484) μg·L⁻¹ and (62±31) μg·L⁻¹, respectively. The mean value of chlorophyll was (9.07±0.91) μg·L⁻¹. The trophic level of XBA was meso-eutrophic, while the general nutrient limitation was phosphorus. The results indicated that XBA has a strong ability to purify itself and has non-point source pollution from terrestrial runoff. The variation of TN/TP ratio was caused by a variation in TN rather than in TP when TN/TP < 22. N-fixation from cyanobacteria occurred and became an important process in overcoming the nitrogen deficit under a low TN/TP ratio. When TN/TP ⩾ 22, the variation of TP affected the TN/TP ratio more significantly than TN. The increase of TP in XBA was caused mainly by particulate phosphorus, which could originate from a non-point source as adsorptive inorganic forms after heavy rainfall and surface runoff. An increase in the river’s flow could also contribute to an unstable environment for the growth of phytoplankton.     

Temporal and spatial variation of nitrogen and phosphorus and eutrophication assessment for a typical arid river—Fuyang River in northern China

Based on water quality surveys over 2 years(July to December,in 2014 and 2015) in a typical arid river in northern China the Xingtai segment of the Fuyang River basin — the variation of nitrogen(N) and phosphorus(P) was analyzed.The extent of water eutrophication of this segment was also assessed using a universal index formula for eutrophic evaluation and a logarithmic power function.The results showed that the average concentration of total N(TN) was 27.2 mg/L(NH_3-N,63.5%),total P(TP) was 2.0 mg/L(solution reactive phosphorus,68.8%).Temporal and spatial variations of N and P in this segment were observed.Concentrations of N and P in the arid season were higher than those in the rainy season.Spatially,the N and P concentrations followed the same trend;i.e.,higher in the city segment than in the suburbs,and decreasing along the river.The water eutrophication in the studied segment reached extremely high levels at all times(eutrophication index ≥76.3).Spatially,its trend was clearly linked with N and P.Water shortage,pollution accumulation and a weak self-purification function are the main reasons for the prominent eutrophication in this segment.     

Characteristics of phosphorus chemistry and its geographical distribution in the Haihe River valley,North China

ＣｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｐｈｏｓｐｈｏｒｕｓｃｈｅｍｉｓｔｒｙａｎｄｉｔｓｇｅｏｇｒａｐｈｉｃａｌｄｉｓｔｒｉｂｕｔｉｏｎｉｎｔｈｅＨａｉｈｅＲｉｖｅｒｖａｌｌｅｙ，ＮｏｒｔｈＣｈｉｎａＪｉａｎｇＧａｏｍｉｎｇ；ＨｕａｎｇＹｉｎｘｉａｏ；Ｌ...     

Agricultural non-point nitrogen pollution control function of different vegetation types in riparian wetlands： A case study in the Yellow River wetland in China

Riparian wetland is the major transition zone of matter, energy and information transfer between aquatic and terrestrial ecosystems and has important functions of water purification and non-point pollution control. Using the field experiment method and an isotope tracing technique, the agricultural non-point nitrogen pollution control function of di erent vegetation types in riparian wetland was studied in the Kouma Section of the Yellow River. The results showed that the retention of agricultural non-point nitrogen pollution by riparian wetland soil occurs mainly in top 0–10 cm layer. The amount of nitrogen retained by surface soils associated with three types of vegetation are 0.045 mg/g for Phragmites communis Trin Linn, 0.036 mg/g for Scirpus triqueter Linn, and 0.032 mg/g for Typha angustifolia Linn, which account for 59.21%, 56.25%, and 56.14% of the total nitrogen interception, respectively. Exogenous nitrogen in 0–10 cm soil layer changes more quickly than in other layers. One month after adding K15NO3 to the tested vegetation, nitrogen content was 77.78% for P. communis Trin, 68.75% for T. angustifolia, and 8.33% for S. triqueter in the surface soil. After three months, nitrogen content was 93.33% for P. communis Trin, 72.22% for S. triqueter, and 37.50% for T. Angustifolia. There are large di erences among vegetation communities respecting to purification of agricultural non-point nitrogen pollution. The nitrogen uptake amount decreases in the sequence: new shoots of P. communis Trin (9.731 mg/g) > old P. communis Trin (4.939 mg/g) > S. triqueter (0.620 mg/g) > T. angustifolia (0.186 mg/g). Observations indicated that the presence of riparian wetlands as bu ers on and adjacent to stream banks could be recommended to control agricultural non-point pollution.     

Multiple isotopes reveal the driving mechanism of high NO–3 level and key processes of nitrogen cycling in the lower reaches of Yellow River

The continuous increase of nitrate (NO₃^–) level in rivers is a hot issue in the world.However,the driving mechanism of high NO₃^–level in large rivers is still lacking,which has limited the use of river water and increased the cost of water treatment.In this study,multiple isotopes and source resolution models are applied to identify the driving mechanism of high NO₃^–level and key processes of nitrogen cycling in the lower reaches ...     

Climate change adaptation strategies in the Mekong and Orange-Senqu basins: What determines the state-of-play?

The challenge of governing transboundary water resources is expected to increase with climate change and the resulting need to adapt to its impacts such as temperature increase, more precipitation in the wet season and less in the dry season. In a number of transboundary basins, international regimes, and in particular river basin commissions, are emerging to account for this and other challenges. Some basins are, however, rather advanced in terms of developing climate change adaptation strategies, while others are in a more nascent stage. For the two case studies of the Orange-Senqu and Mekong river basins, this paper attempts to explain the different degrees of progress towards climate change adaptation by applying regime effectiveness analysis. First, we analyze, using the Activity Diagram (AD) of the Management and Transition Framework (MTF), at which stage in the climate change adaptation policy formation process each of the two basins is. Then we attempt to explain the different degrees of progress towards adaptation by means of regime effectiveness theory. Variables indicating regime effectiveness are taken from the literature and further developed to suit the context of climate change adaptation. We find that the different degrees of progress can partially be explained by some variables of regime effectiveness such as the characteristics of rules and procedures, organizational structure, the role of riparian countries as well as international context. At the same time, the analysis points to the need for an analysis of additional factors that potentially shape decision-making and policy processes for climate change adaptation in international river basins such as (a) the hydrological, political and socio-economic setting, (b) underlying principles of regional cooperation (or conflict), (c) interests and values of the various actors in the negotiation process and (d) the possible linkages and trade-offs with other policy fields.     

Underestimation of phosphorus fraction change in the supernatant after phosphorus adsorption onto iron oxides and iron oxide–natural organic matter complexes

The phosphorus(P) fraction distribution and formation mechanism in the supernatant after P adsorption onto iron oxides and iron oxide-humic acid(HA) complexes were analyzed using the ultrafiltration method in this study.With an initial P concentration of 20 mg/L(I =0.01 mol/L and pH = 7),it was shown that the colloid(1 kDa-0.45 μm) component of P accounted for 10.6%,11.6%,6.5%,and 4.0%of remaining total P concentration in the supernatant after P adsorption onto ferrihydrite(FH),goethite(GE),ferrihydrite-humic acid complex(FH-HA),goethite-humic acid complex(GE-HA),respectively.The 1 kDa component of P was still the predominant fraction in the supernatant,and underestimated colloidal P accounted for 2.2%,55.1%,45.5%,and 38.7%of P adsorption onto the solid surface of FH,FH-HA,GE and GE-HA,respectively.Thus,the colloid P could not be neglected.Notably,it could be interpreted that Fe~(3+) hydrolysis from the adsorbents followed by the formation of colloidal hydrous ferric oxide aggregates was the main mechanism for the formation of the colloid P in the supernatant.And colloidal adsorbent particles co-existing in the supernatant were another important reason for it.Additionally,dissolve organic matter dissolved from iron oxide-HA complexes could occupy large adsorption sites of colloidal iron causing less colloid P in the supernatant.Ultimately,we believe that the findings can provide a new way to deeply interpret the geochemical cycling of P,even when considering other contaminants such as organic pollutants,heavy metal ions,and arsenate at the sediment/soil-water interface in the real environment.     

Dynamic response of chlorsulfuron herbicide to nitrogen mineralization and the ratio of microbial biomass nitrogen to nitrogen mineralization in the soil

ＩｎｔｒｏｄｕｃｔｉｏｎＨｅｒｂｉｃｉｄｅｓａｒｅｎｏｗｕｓｅｄｅｘｔｅｎｓｉｖｅｌｙｉｎｃｒｏｐｐｒｏｄｕｃｔｉｏｎ.Ｔｈｅｉｎｃｒｅａｓｉｎｇｕｓｅｏｆｈｅｒｂｉｃｉｄｅｓｗｉｔｈｎｉｔｒｏｇｅｎｆｅｒｔｉｌｉｚｅｒｓｈａｓｃｒｅａｔｅｄｓｅｒｉ?..     

Ecological and environmental water demand of the lakes in the Haihe-Luanhe Basin of North China

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅＨａｉｈｅ ＬｕａｎｈｅＢａｓｉｎｉｓｔｈｅｄｉｓｔｒｉｃｔｆａｃｉｎｇｔｈｅｐｒｏｂｌｅｍｏｆｗａｔｅｒｃｒｉｓｉｓｉｎｔｈｅＮｏｒｔｈＣｈｉｎａ.Ｗａｔｅｒｐｏｌｌｕｔｉｏｎｉｓｓｕｅｓａｎｄａｎｔｈｒｏｐｏｇｅｎｉｃｄｉｓｔｕｒｂａｎｃｅａｒｅｖｅｒｙｓｅｒｉｏｕｓａｔｔｈｅｓａｍｅｔｉｍｅ .Ｗａｔｅｒｄｅｆｉｃｉｅｎｃｙ ,ｐｏｌｌｕｔｉｏｎａｎｄｏｖｅｒｐｏｐｕｌａｔｉｏｎｈａｖｅｒｅｓｕｌｔｅｄｉｎｏｂｖｉｏｕｓｅｃｏｌｏｇｉｃａｌｄｅｇｒａｄａｔｉｏｎａｎ…     

Long-term nitrogen and phosphorus removal,shifts of functional bacteria and fate of resistance genes in bioretention systems under sulfamethoxazole stress

To understand the long-term performance of bioretention systems under sulfamethoxazole (SMX) stress, an unplanted bioretention system (BRS) and two modified BRSs with coconut-shell activated carbon (CAC) and CAC/zero-valent-iron (Fe0) granules (CAC-BRS and Fe/CAC-BRS) were established. Both CAC-BRS and Fe/CAC-BRS significantly outperformed BRS in removing total nitrogen (TN)(CAC-BRS:82.48%; Fe/CAC-BRS:78.08%; BRS:47.51%), total phosphorous (TP)(CAC-BRS:79.36%; Fe/CAC-BRS:98.26%; BRS:41.99%),and...     

Changes in nitrogen budget and potential risk to the environment over 20 years(1990–2010) in the agroecosystems of the Haihe Basin,China

The nitrogen balance can serve as an indicator of the risk to the environment of nitrogen loss from agricultural land. To investigate the temporal and spatial changes in agricultural nitrogen application and its potential threat to the environment of the Haihe Basin in China, we used a database of county-level agricultural statistics to calculate agricultural nitrogen input, output,surplus intensity, and use efficiency. Chemical fertilizer nitrogen input increased by 51.7% from1990 to 2000 and by 37.2% from 2000 to 2010, concomitant with increasing crop yields.Simultaneously, the nitrogen surplus intensity increased by 53.5% from 1990 to 2000 and by16.5% from 2000 to 2010, presenting a continuously increased environmental risk. Nitrogen use efficiency decreased from 0.46 in 1990 to 0.42 in 2000 and remained constant at 0.42 in 2010,partly due to fertilizer composition and type improvement. This level indicates that more than half of nitrogen inputs are lost in agroecosystems. Our results suggest that although the improvement in fertilizer composition and types has partially offset the decrease in nitrogen use efficiency, the environmental risk has still increased gradually over the past 20 years, along with the increase in crop yields and nitrogen application. It is important to achieve a better nitrogen balance through more effective management to significantly reduce the environmental risk,decrease nitrogen surplus intensity, and increase nitrogen use efficiency without sacrificing crop yields.     

Speciation and distribution characteristics of heavy metals in the Changjiang River water

ＳｐｅｃｉａｔｉｏｎａｎｄｄｉｓｔｒｉｂｕｔｉｏｎｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｈｅａｖｙｍｅｔａｌｓｉｎｔｈｅＣｈａｎｇｊｉａｎｇＲｉｖｅｒｗａｔｅｒ￥ＣｈｅｎＸｉｂａｏ；ＺｈａｎｇＳｈｅｎ；ＤｏｎｇＷｅｎｊｉａｎｇ；ＺｈａｎｇＬｉｃｈｅｎｇ（...     

Changes in soil carbon storage due to over-grazing in Leymus chinensis steppe in the Xilin River Basin of Inner Mongolia

ＣｈａｎｇｅｓｉｎｓｏｉｌｃａｒｂｏｎｓｔｏｒａｇｅｄｕｅｔｏｏｖｅｒｇｒａｚｉｎｇｉｎＬｅｙｍｕｓｃｈｉｎｅｎｓｉｓｓｔｅｐｐｅｉｎｔｈｅＸｉｌｉｎＲｉｖｅｒＢａｓｉｎｏｆＩｎｎｅｒＭｏｎｇｏｌｉａＬｉＬｉｎｇｈａｏ，ＣｈｅｎＺｕｏｚｈｏｎｇ，Ｗ...     

Role of phosphorus on the biogeochemical behavior of cadmium in the contaminated soil under leaching and pot experiments

Phosphorus (P) is involved in various biochemical reactions in plant growth,so it is beneficial to plants growing in soils contaminated by metals,including cadmium (Cd).However,few studies have reported on the mechanistic roles of P in mitigating Cd toxicity to ryegrass root,and especially in alleviating the disruption of the mitochondrial function of living cells.In this study,the physiological and biochemical mechanisms associated with ryegrass growth under various Cd and P treatments were inv...     

River flood risk and adaptation in Europe—assessment of the present status

Flood disasters have had a devastating effect worldwide over the past century, both in terms of human suffering and material losses. The study of these events and development of more effective adaptation and mitigation policies has become a priority, both in Europe and other parts of the globe. This paper detects and presents the spatial distribution of river flood risks in Europe. The methodology we developed involves an assessment of three key risk components: exposure, vulnerability and hazard. A topography-based flood hazard map of Europe, identifying low-lying areas adjacent to rivers, is presented and used to identify risk, together with land-use data and damage-stage relationship for different land uses. The study covers river flood risk for the entire European continent. This methodology can be used to determine the level of future risk, using the estimations on Hazard, Exposure and Vulnerability from specific climate and economic development models. Annual average flood damage is estimated for European regions, in absolute monetary terms and in % of regional Gross Domestic Product (GDP). The results highlight regions where the threat to the economy from river flood hazard is of major concern.     

Changes in nitrogen budget and potential risk to the environment over 20 years (1990–2010) in the agroecosystems of the Haihe Basin,China

The nitrogen balance can serve as an indicator of the risk to the environment of nitrogen loss from agricultural land. To investigate the temporal and spatial changes in agricultural nitrogen application and its potential threat to the environment of the Haihe Basin in China, we used a database of county-level agricultural statistics to calculate agricultural nitrogen input, output, surplus intensity, and use efficiency. Chemical fertilizer nitrogen input increased by 51.7% from 1990 to 2000 and by 37.2% from 2000 to 2010, concomitant with increasing crop yields. Simultaneously, the nitrogen surplus intensity increased by 53.5% from 1990 to 2000 and by 16.5% from 2000 to 2010, presenting a continuously increased environmental risk. Nitrogen use efficiency decreased from 0.46 in 1990 to 0.42 in 2000 and remained constant at 0.42 in 2010, partly due to fertilizer composition and type improvement. This level indicates that more than half of nitrogen inputs are lost in agroecosystems. Our results suggest that although the improvement in fertilizer composition and types has partially offset the decrease in nitrogen use efficiency, the environmental risk has still increased gradually over the past 20 years, along with the increase in crop yields and nitrogen application. It is important to achieve a better nitrogen balance through more effective management to significantly reduce the environmental risk, decrease nitrogen surplus intensity, and increase nitrogen use efficiency without sacrificing crop yields.     

Vertical and temporal distribution of nitrogen and phosphorus and relationship with their influencing factors in aquatic-terrestrial ecotone： a case study in Taihu Lake, China

Vertical and temporal distributions of N and P in soil solution in aquatic-terrestrial ecotone （ATE） of Taihu Lake were investigated, and the relations among N, P, ORP （oxidation reduction potential）, TOC, root system biomass and microorganism were studied. As a whole, significant declines in TN, NO3^--N, DON （dissolved organic nitrogen） and TP concentration in soil solution have occurred with increase of the depth, and reached their minima at 60 cm depth, except for NH4^＋-N, which increased with depth. The concentration of TP increased gradually from spring to winter in the topsoil, the maximum 0.08 mg/L presented in the winter while the minimum 0.03 mg/L in spring. In the deeper layer, the concentration value of TP fluctuated little. As for the NO3^--N, its seasonal variation was significant at 20 cm depth, its concentration increased gradually from spring to autumn, and decreased markedly in winter. Vertical and temporal distribution of DON is contrary to that of NO3^--N. The results also show that the variation of N and P in the percolate between adjacent layers is obviously different. The vertical variation ofTN, TP, NO3^--N, NH4^＋-N and DON is significant, of which the variation coefficient of NO3^--N along the depth reaches 100.23%, the highest; while the variation coefficient of DON is 41.14%, the smallest. The results of correlation analysis show that the concentration of nitrogen and phosphorus correlate significantly with TOC, ORP, root biomass and counts of nitrifying bacteria. Most nutrients altered much from 20 to 40 cm along the depth. However, DON changed more between 60 and 80 cm. Results show that soil of 0-60 cm depth is active rhizoplane, with strong capability to remove the nitrogen and phosphorus in ATE. It may suggest that there exists the optimum ecological efficiency in the depth of above 60 cm in reed wetland. This will be very significant for ecological restoration and reestablishment.     

Impacts of climate change on development rate and production of corn in the northeastern China

In this paper, the impacts of climate change on development rate and production of corn in the northeastern China are discussed. The results show that the higher the temperature is, the faster the development rate will be. And the more the precipitation is, the slower the development rate will be. Of which, air temperature is the controlling factor of corn development rate. The influences of development rate on corn yield are remarkable. The impacts of development rate on production in first and last periods are great, and small in the middle two periods. The development rate is positive by relate with corn production from sowing to emergence stage and negative during other periods. So, it is very important to arrange a suitable sowing time for com cultivating in the northeastern China.     

The curve of ion exchange ratio(%)-pH of the interaction between suspended particles with Cd(Ⅱ) in the Yellow River

Ｔｈｅｃｕｒｖｅｏｆｉｏｎｅｘｃｈａｎｇｅｒａｔｉｏ（％）ｐＨｏｆｔｈｅｉｎｔｅｒａｃｔｉｏｎｂｅｔｗｅｎｓｕｓｐｅｎｄｅｄｐａｒｔｉｃｌｅｓｗｉｔｈＣｄ（Ⅱ）ｉｎｔｈｅＹｅｌｏｗＲｉｖｅｒＹａｎｇＨｏｎｇｗｅｉ，ＪｉａｏＸｉａｏｂａｏ，Ｇｕ...