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Purpose: Ammonia oxidation-as the rate-limiting step of nitrification-has been found to be performed by both ammonia-oxidizing archaea (AOA) and bacteria (AOB). However, how ammonium content and oxidation-reduction status regulate the distribution of ammonia oxidizers in constructed wetlands and their contribution to potential ammonia oxidation rate are still in dispute. This study aimed to explore the effects of ammonium content and oxidation-reduction status on the abundances of AOA/AOB and examine the contributions of AOA and AOB populations to ammonia oxidation rates in the plant-bed/ditch system of a constructed wetland. Materials and methods: Sampling was carried out in the plant-bed/ditch system of the Shijiuyang Constructed Wetland, China. Three plant-bed soil cores were collected using a soil auger and sampled at depths of 0, 20, and 50 cm in 5-cm increments. Five ditch surface sediments (0-5 cm) were collected along the water flow direction. The abundances of AOA and AOB were investigated by quantitative polymerase chain reaction based on amoA genes. The potential ammonia oxidation rate was determined using the chlorate inhibition method. Results and discussion: The results showed that AOA outnumbered AOB in the plant-bed surface soil which had lower ammonium content (4.67-7.63 mg kg), but that AOB outnumbered AOA in the ditch surface sediment which had higher ammonium content (14.0-22.9 mg kg). Ammonium content was found to be the crucial factor influencing the relative abundances of AOA and AOB in the surface samples of the plant-bed/ditch system. In the deep layers of the plant bed, AOA abundance outnumbered AOB, though much lower oxidation-reduction potential occurred along the water flow direction. Thus, the oxidation-reduction potential may be another factor influencing the distributions of AOA and AOB in the deep layers of the plant bed without significant difference in ammonium content ( p < 0.05). Moreover, the potential ammonia oxidation rate was significantly dominated by AOB rather than AOA in the plant-bed/ditch system. Conclusions: The high ammonium content in the ditch sediment likely favored AOB. AOA seemed to persist more readily even under low oxidation-reduction potential in the deep layers of the plant bed. Ammonium content and the oxidation-reduction potential were important parameters influencing the distribution of AOA and AOB in the plant-bed/ditch system of Shijiuyang Constructed Wetland. AOB contributed more to ammonia oxidation than AOA, both in the plant-bed soils ( r = 0.592, p = 0.0096) and in the ditch sediments ( r = 0.873, p = 0.0002). [ABSTRACT FROM AUTHOR]

Evidence for anaerobic ammonium oxidation in a paddy field was obtained in Southern China using an isotope-pairing technique, quantitative PCR assays and 16S rRNA gene clone libraries, along with nutrient profiles of soil cores. A paddy field with a high load of slurry manure as fertilizer was selected for this study and was shown to contain a high amount of ammonium (6.2-178.8 mg kg−1). The anaerobic oxidation of ammonium (anammox) rates in this paddy soil ranged between 0.5 and 2.9 nmolN per gram of soil per hour in different depths of the soil core, and the specific cellular anammox activity observed in batch tests ranged from 2.9 to 21 fmol per cell per day. Anammox contributed 4-37% to soil N2 production, the remainder being due to denitrification. The 16S rRNA gene sequences of surface soil were closely related to the anammox bacteria 'Kuenenia', 'Anammoxoglobus' and 'Jettenia'. Most of the anammox 16S rRNA genes retrieved from the deeper soil were affiliated to 'Brocadia'. The retrieval of mainly bacterial amoA sequences in the upper part of the paddy soil indicated that nitrifying bacteria may be the major source of nitrite for anammox bacteria in the cultivated horizon. In the deeper oxygen-limited parts, only archaeal amoA sequences were found, indicating that archaea may produce nitrite in this part of the soil. It is estimated that a total loss of 76 g N m−2 per year is linked to anammox in the paddy field. [ABSTRACT FROM AUTHOR]

The boundary filtration effect of land/water ecotones with reed-bed/ditch systems under water level fluctuations was studied in Baiyangdian Lake of North China. It was found that the changes in reed bed areas which were primarily affected by water level fluctuations and the root channels in the wetland soils together largely determined boundary filtration efficiency. The ecotones displayed the greatest boundary effect at a moderate water level of about 8 m above sea level. The massive root channels in the wetland soils promoted water flowing into the reed beds as far as 8 m horizontally by subsurface in wet years. In dry years, when the water level was below the root channel distribution zone, the lateral water exchange width of ecotones was limited to 0.5 m along the fringe area. It is calculated that, at 8 m water level, the total boundary length of ecotones is 7,273 km and the boundary exchange volume is 5.8 × 106 m3. While at 6.5 m water level, the total boundary length of ecotones is reduced to 2,699 km and the boundary exchange volume is 1.1 × 105 m3. The standard capacity for phosphorus retention was 105.9 and 2.5 tonnes at water levels of 8 and 6.5 m, respectively. This suggests that the boundary filtration effect of reed-bed/ditch wetlands is important for improving the water quality of inland waters, and this effect should be considered in regulating and managing lake water levels. [ABSTRACT FROM AUTHOR]

The continuously deteriorating quality of source water is threatening the safety of drinking water in China. Various efforts have been made to update water treatment processes to decrease the pollution problems of drinking water, such as protection of drinking water sources, enhancement of conventional treatment processes, and development of new or advanced treatment technologies. This paper reviews a variety of protection and remediation methods for drinking water sources, development and application of drinking water treatment technologies, new technologies for special pollutants removal from groundwater, and the latest research progress on water distribution systems in China. [ABSTRACT FROM AUTHOR]

A field study was conducted to determine the effect of landscape spatial pattern and micro-topography on nutrient transfer via runoff from two catchments into Yuqiao Reservoir in north China. The surface runoff discharge was measured during rainfall events and water samples were analyzed in 2004 and 2005. The mean annual total nitrogen (TN) and total phosphorus (TP) exports per unit area from Caogezhuang catchment (C catchment) were 1.048 and 0.561 kg ha−1 year−1, respectively, while the TN and TP exports from Taohuasi catchment (T catchment) were 0.158 and 0.027 kg ha−1 year−1. In both catchments, village and vineyard shared the highest nutrient export ability due to the accumulated animal waste and heavy application of fertilizer and manure. In T catchment, the distance of village and vineyard was about 1,500 m away from the receiving water and in between were woodland and cropland. In the hydrological pathway, there were sink landscape structures of small stone dams, roadside swale, vegetated filter strip and dry ponds, which could detain water and nutrients. In C catchment, the distance between the village and the receiving water was about 200 m, and the hydrological pathway was compacted roads and ditches with no sink structures. It is suggested that the distance between the pollution source area and the receiving water and the micro-topographical features were the main factors to control the great difference in nutrient export rates. [ABSTRACT FROM AUTHOR]

Riparian wetlands are important components of the lake ecosystem, and they play essential roles in maintaining system health. Remediation of degraded lakeshore wetlands is an essential component of lake restoration. A study was conducted to investigate the restoration of lakeshore wetlands, which were converted to rice fields and then abandoned for 2, 5, 10 and 15 years, near Lake Taihu. Soil samples (0–20 cm and 20–40 cm) were taken and plant species were investigated. The carbon content in the soil had increased significantly, rising from 0.71% to 1.85% between 2 and 15 years. Organic matter accumulation improved soil texture, and water stable aggregate content (>0.25 mm) and soil porosity increased. Total nitrogen in the soil increased from 0.06% to 0.13%, and total Kjeldahl nitrogen increased from 124.4 mg kg−1 to 351.5 mg kg−1. Total phosphorus in the soil increased from 0.045% to 0.071%, and the Olsen- P value increased from 5.13 mg kg−1 to 16.0 mg kg−1. Results showed that phosphorous did not increase as much as nitrogen. In the vegetation restoration process, plant species composition moved towards a natural wetland community, and spatial heterogeneity and landscape diversity increased. The richness of plant biodiversity increased rapidly in the first 2 years, then more slowly in later restoration stages. The wetlands recovery process may be complicated by interactions of biota and soil and hydrological conditions. [ABSTRACT FROM AUTHOR]

Spatio-temporal distribution of nitrogen was examined along the gradient from open water to lakeshore in Lake Taihu, China. Two types of undulating littoral zones were selected: natural reed belt and bare lakeshore. The reed belt affected nitrogen transformation and was sink for internal-lake nitrogen, whereas the bare lakeshore showed little effect. During the growing season, NO-N concentration increased by up to 3–5 times from open water to reed belt, while NH-N concentration decreased. It suggested that nitrification was the main nitrogen process in reed belt. Total dissolved nitrogen (TDN) showed little spatial variation, indicating that most of nitrogen released from sediment did not move into open water again. Significant temporal variation of dissolved nitrogen occurred and was similar in both the littoral zone and the open water. Maximum TDN and NH-N concentrations occurred in January, and NO-N in March. Minimum NH-N and NO-N concentrations occurred in July and August, respectively. An increasing total soil nitrogen was found in the surface sediments from reed belt to open water. This further suggested that the reed-covered littoral zone had strong nitrogen transformation potential. [ABSTRACT FROM AUTHOR]

The landscape structure of a multipond system, runoff type and P-pollutant transport in an experimental watershed was studied during 1995 and 1998. A multipond system is a wetland system composed with many tiny ponds and ditches. In this watershed, it was found that such a system effectively controls the hydrological process through its huge storage capacity. The multipond system has a high interaction of land/water ecotones, which decreases the flow velocity systematically and results in a high sedimentation of the particulate matters. The multipond system intercepts runoff and creates either continuous or discontinuous flow. The retention efficiency of the system was very high in both cases but differed in nature. During continuous runoff on 1 May 1998, in a subwatershed Baojiatang, the retention rates of water, total phosphorus (TP), dissolved phosphorus (DP) and suspended solids (SS) by the multipond system were 83.0, 93.9, 90.9 and 94.9%, respectively. During discontinuous runoff on 29 June 1998, runoff volume generated from all lands was 1841 m3, but no surface water was exported and the system retention rates of TP, DP and SS were nearly complete. The removal of particulate phosphorus by the system was more effective than removal of DP and thus DP was the main form of phosphorus exported from the watershed during continuous flow. Because of such control, the export amount of phosphorus was greatly reduced. The output of TP and DP was 0.013 and 0.012 kg ha-1, respectively, from Liuchahe watershed in 1995, and they were 0.037 and 0.030 kg ha-1 in 1998 correspondingly. [ABSTRACT FROM AUTHOR]

The influence of land-based source pollutants to marine ecological environment is principally in coastal or enclosed sea wates. Flux of land-based source pollutants into the sea will be effected due to social and economic development in the Tumen River basin. Pollutant type and primary pollution factor of the Tumen River in Northeast China is described by weighted coefficient method in this paper. The results indicate that the river is organic pollution type and primary pollution factor is COD. Fresh water fraction proves that the estuary is not affected by tide cycle. COD annual flux entering the Sea of Japan calculated by zero-dimension model in 1993 was 90.50 × 103 tons. It is estimated with emission coefficient method that the COD will be 176.4 × 103 and 458.6 × 103 tons for the years of 2000 and 2010 respectively. [ABSTRACT FROM AUTHOR]

Denitrification has long been regarded as the only pathway for terrestrial nitrogen (N) loss to the atmosphere. Here we demonstrate that large-scale anaerobic ammonium oxidation (anammox), an overlooked N loss process alternative to denitrification which bypasses nitrous oxide (N2O), is ubiquitous in inland waters of China and contributes significantly to N loss. Anammox rates in aquatic systems show different levels (1.0-975.9 μmol N m−2 h−1, n = 256) with hotspots occurring at oxic-anoxic interfaces and harboring distinct biogeochemical and biogeographical features. Extrapolation of these results to the China-national level shows that anammox could contribute about 2.0 Tg N yr−1, which equals averagely 11.4% of the total N loss from China's inland waters. Our results indicate that a significant amount of the nitrogen lost from inland waters bypasses denitrification, which is important for constructing more accurate climate models and may significantly reduce potential N2O emission risk at a large scale. [ABSTRACT FROM AUTHOR]

Diffuse pollution from agricultural land is one of the main causes for lake eutrophication. Multipond systems, an ancient invention in China, are composed of many tiny ponds and ditches, scattered in agricultural fields. After a long period of research in an experimental watershed in Liuchahe, it was found that multipond systems constitute diffuse pollution control. They have a large capacity for water storageand serve to control the export of water, suspended matter, and phosphorus. Multipond systems significantly reduce runoff velocity. Sediments and phosphorus retained in the Liuchahe watershed were 14.38 x 106 and 7016 kg yr-1 respectively (area 691.6 ha). Irrigation provides an effective way to recycle and remove phosphorus. The use of multipond systems is a sustainable way to recycle valuable nutrients and reduce their discharge and thus pollution of downstream lakes. [ABSTRACT FROM AUTHOR]