Search

In this study, laboratory experiments were used to compare the effects of two LED light sources (blue and red) combined with fiber membranes on the increase of Dissolved Oxygen (DO) in eutrophic water bodies for improvement of water quality. The results showed that the application of these two LED light sources can increase the DO concentration and oxidation-reduction potential (ORP), and eliminate the NH4+-N in water bodies and the phosphorus release from the sediment, resulting in the improvement of sediment. Specifically, the blue LED light source is more benefitable to the increase of the DO concentration than the red LED light source. After 28 days, the DO concentration increases to 10 mg/L, and the redox potential is higher than 50 mV with the elimination of NH4+-N. This study illustrated that LED light sources can significantly increase the DO and effectively improve the water quality in eutrophic water bodies.

Aquaculture has become one of the major sources of lake eutrophication, due to the lack of direct and efficient technologies for pollution control and remediation. This study proposes a novel ecological dam (Eco-dam) system, which consists of biofilter floating beds and plant floating beds that form an enclosure (the test zone) around the breeding area that allows lake water to pass through. A pilot-scale test was conducted to test pollution control and in situ bioremediation during breeding of Chinese mitten crab (Eriocheir sinensis) in Yangcheng Lake, China. The results showed slight improvement of water quality in the test zone compared with the breeding zone. The biofilm that formed on the biofilter played a major role in removal of organic pollutants and nitrogen (0.609 kg COD/(m2·d), 0.512 kg NH4+-N/(m2·d), 0.482 kg NO2−-N/(m2·d), and 0.112 kg NO3−-N/(m2·d)). Both proteins and volatile suspended solids (VSS) in the Eco-dam biofilm decreased from the water surface towards the lake bottom, especially below 0.5 m depth. The average ratio of VSS to suspended solids in the biofilm was 0.337 ± 0.025 g/g. Analysis with the Illumina MiSeq System confirmed the presence of a diverse microbe population in the biofilm, performing organic carbon removal and nitrification and denitrification, with limited photosynthesis near the lake surface and methane oxidation near the lake bottom.

To enhance water quality in eutrophic urban ponds, the effects of a portable water circulation device, equipped with biological oxidation carriers and light-emitting diodes (LEDs), on dissolved oxygen (DO), water transparency, total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD), and plankton community in laboratory and field mesocosms were examined. In the laboratory, water quality was monitored in vessels containing water and mud collected from an urban pond, which were subjected to different treatments (control, device without LEDs, and device with LEDs) for 28 days. In the treatments using the device (with and without LEDs), DO increased by aeration, whereas TP decreased by mitigation of mud anoxia. Reductions in TN and the presence of phyto- and zooplankton were observed in those treatments with LEDs, in which periphyton growth was stimulated in the carriers. Under field conditions, water quality of the pond was monitored for 40 days in enclosures. Clear increases in DO and transparency and reductions in TN, TP, and COD were detected in the treatments using the device. Reductions in cyanobacteria and increases in diatoms, green algae, and zooplankton were observed in the treatments with LEDs. Thus, the circulation device effectively improved oxygen condition of the bottom and nutrient flux between sediment and overlying water. In addition, these results suggest that the COD removal and growth of diatoms and green algae by LEDs in carriers play roles on developing periphyton at the bottom and suitable phytoplankton community in the water column.

Three kinds of representative sediments were obtained from a macrophyte-dominated bay (East Lake Taihu) and two algae-dominated regions (Western Lake Taihu and Meiliang Bay). Physiological responses of Vallisneria asiatica to these sediments were compared. Results from 20 days exposures showed no obvious differences in malondialdehyde (MDA) in roots, while the MDA content in leaves of plants exposed to Western Lake Taihu sediment was significantly (p

The accuracy of methods for estimating evapotranspiration at upland in a humid area was investigated at a soybean field. First, hourly evapotranspiration were estimated using the Bowen ratio method, Brown‐Rosenberg method, Batholic method and Monteith method. Second, daily evapotranspiration were estimated using the Ostromeki method, Makkink method, Stephens method, Turc method, Jensen method, van Bavel method, van Bavel‐Businger method and Penman method. Correlativity between estimated and observed values was compared, and superiority of these methods was discussed. When hourly meteorological data were available, the Batholic method was accurate next to the Bowen ratio method. And when daily meteorological data were available, the Stephens method showed high accuracy next to the Penman method, though this method only use average daily temperature and daily solar radiation.

In the arid and semi‐arid areas where soil water holding capacity is small, research in the soil water characteristics such as the hydraulic conductivity, diffusivity and water retention is important for the proper irrigation scheduling to provide the sustainable and steady crop production. In this research, the permeability of the soil in Tenggeli desert was measured, and a numerical study of the infiltration process was conducted. The available moisture was 10.3% for the original desert sand. But it was proved that available moisture increased up to 27.5% in an irrigated field because of cultivation with the water supply from the Yellow river. The unsaturated hydraulic conductivity in drying process ranged from 10 –3 to

The occurrence and distribution of microcystins were investigated in Lake Taihu, the third largest lake in China. An extensive survey, larger and broader in scale than previous studies, was conducted in summer 2010. The highest microcystin concentration was found at southern part of Taihu, which was newly included in this survey. In northern coastal areas, total cellular concentrations of 20 to 44 μg/L were observed. In northern offshore waters, levels were up to 4.8 μg/L. Microcystin occurrence was highly correlated with chemical oxygen demand, turbidity, and chlorophyll-a. Extracellular/total cellular microcystin (E/T) ratios were calculated and compared to other water quality parameters. A higher correlation was found using E/T ratios than original microcystin values. These results show that algal blooms are having a severe impact on Lake Taihu, and further and extensive monitoring and research are required to suppress blooms effectively.

Lowland area at seacoast of the Arikake Bay in Japan is famous for rotational use of creek water for rice production. About 40 years ago, almost whole area was covered with rice paddy in summer season. For the purpose of regulating the rice production, about 40 % of rice fields have been used for upland crop production. In addition to the changes of agricultural style, the inflow of the contaminated drainage water has been increased by the development of urbanization. To keep the sustainable agriculture in this area, it is requested to establish the regional control system to keep the creek water clean. The objective of this study is to evaluate the effect of the rice paddy, upland crop, and greenhouse cultivations on the water quality. First, the effects of water management, fertilizer management, crop management on the nitrogen and phosphate loads to creek water were studied experimentally at the study site about 10 ha. Water purification functions of rice paddy were evaluated quantitatively. From this result, it was advocated to prepare water ponded fallow fields through out the year for cleaning creek water. Additionally, the effectiveness for water purification by some vegetables planted in the fallow paddy are introduced. Second, daily changes of creek water qualities were monitored with the automatic sampler at the end of creek networks. Using the data, the relationships between land use condition and water quality along the main creek were simulated with the support of GIS.