Drug-loaded chitosan film prepared via facile solution casting and air-drying of plain water-based chitosan solution for ocular drug delivery

Chitosan is a nature-based polymer with low toxicity,excellent biocompatibility and biodegradability.However,the intractable solubility of chitosan in water and most conventional solvents hampers its biomedical applications.Following the dissolution method for dissolving chitosan in plain water developed by us,chitosan was dissolved in ionic liquid followed by overnight freezing at−20℃ and subsequent solvent exchange with plain water at room temperature.In this study,we fabricated a drug-carrying chitosan film via solution casting and air-drying by using the plain water-based chitosan solution.Specifically,brimonidine tartrate(BT),an antiglaucoma drug,was dissolved in the plain-water based solution and used to prepare BT-loaded chitosan film,i.e.,chitosan-BT film.The resulting film is transparent,structurally stable,and mucoadhesive.Micro-sized antiglaucoma BT drug crystals form and are well dispersed in the chitosan film.The chitosan-BT film enables BT to have a high corneal permeability with fast drug release kinetics for potential ocular drug delivery.

Exploration on compound water circulation system to solve water resources problems of North China Plain

In order to solve water resources problems in the North China Plain, this paper explored human-nature compound water circulation system from three aspects including urban flood control, surface drainage and saline water in the central and eastern of the North China Plain. Results show that:(1) The technical methods have achieved zero increase in rainwater runoff in urban areas,(2) surface drainage depletion problems can be solved through abandoned water and river water separation method,(3) and technical method through promoting rainwater infiltration would be used to solve problem of saline water in the central and eastern parts. This research provides a new perspective to the ultimate solutions to water resources problems in the North China Plain, and a fresh research direction for the development of hydro-geological science.

Experimental study on unsaturated soil water diffusivity in different soils in Hebei Piedmont Plain

Horizontal soil column method was used to determine the horizontal diffusion rate of sandy loam, loam and clay loam under the same bulk density. The results showed that the migration rates of different lithological wet fronts were different. The sandy loam had the fastest migration rate, the loam followed, and the clay loam was the slowest, but the law of change is the same among the three lithologies. The volumetric water content affects the change of Boltzmann parameter λ. When the volumetric water content is between 0.35-0.45 cm^3/cm^3,λ approaches stability. When the volumetric water content is less than 0.35 cm^3/cm^3, the λ value decreases rapidly with the decrease of water content. The water diffusion rate is related to the volumetric water content and particle size. The greater the moisture content is, the greater the diffusion rate will be. The larger the particle size, the larger the diffusion rate. The diffusivity of sandy loam is 10-30 times larger than that of loam and clay loam. The relationship between water content and diffusion rate is in accordance with the exponential function .

ESTIMATION AND EXPLOITATION OF WATER RESOURCES IN THE SANJIANG PLAIN

According to practical measurement and related data, the writer discusses the main features of rivers in the Sanjiang Plain and the change of water balance with time and space, and then estimates water resources of five types, namely, runoff, ground water, soil water, and water supplied by three rivers and lakes (or reservoirs).The total volume of the above-mentioned water resources can be up to 31.5 billion m3. But they are rather unevenly distributed and the annual change is considerable, too. Up to now, only 8.3% of water resources have been utilized. According to a programme, 17.5 billion m3 will be utilized in the future in the district. Rationally exploiting water resources in the district should be combined with protection and management, and the sole criterion for judging rationality of utilization is that whether it is beneficial to economic, ecologic and social aspects.

Distribution characteristics of dissolved organic carbon in annular wetland soil-water solutions through soil profiles in the Sanjiang Plain,Northeast China

Overwhelming evidence reveals that concentrations of dissolved organic carbon （DOC） have increased in streams which brings negative environmental impacts. DOC in stream flow is mainly originated from soil-water solutions of watershed. Wetlands prove to be the most sensitive areas as an important DOC reserve between terrestrial and fluvial biogeosystems. This reported study was focused on the distribution characteristics and the controlling factors of DOC in soil-water solutions of annular wetland, i.e., a dishing wetland and a forest wetland together, in the Sanjiang Plain, Northeast China. The results indicate that DOC concentrations in soilwater solutions decreased and then increased with increasing soil depth in the annular wetland. In the upper soil layers of 0-10 cm and 10-20 cm, DOC concentrations in soil-water solutions linearly increased from edge to center of the annular wetland （R^2 = 0.3122 and R^2 = 0.443）. The distribution variations were intimately linked to DOC production and utilization and DOC transport processes in annular wetland soil-water solutions. The concentrations of total organic carbon （TOC）, total carbon （TC） and Fe（II）, DOC mobility and continuous vertical and lateral flow affectext the distribution variations of DOC in soil-water solutions. The correlation coefficients between DOC concentrations and TOC, TC and Fe（II） were 0.974, 0.813 and 0.753 respectively. These distribution characteristics suggested a systematic response of the distribution variations of DOC in annular wetland soil-water solutions to the geometry of closed depressions on a scale of small catchments. However, the DOC in soil pore water of the annular wetland may be the potential source of DOC to stream flow on watershed scale. These observations also implied the fragmentation of wetland landscape could bring the spatial-temporal variations of DOC distribution and exports, which would bring negative environmental impacts in watersheds of the Sanjiang Plain.

SOIL SALINITY CONTROI,REGARDING SUBSURFACE WATER REGULATION IN NORTH CHINA PLAIN

The North China Plain (NCP) lying along the eastern coastal area withgeogriaphical coordinates 100°to 120°and 30° to 40°W, is one of the mostimportan agncultural ngons in China. A problem in soil salmization has beenfound in vast areas along the lower reaches of the Yellow hiver and north of it. After30 years of work on saline soil amelioration, 2.0 million ha has been improved,accounting for over 60 percen of the total ongnal saline soil area. Ths achievetnenthas ban obtained in close relation to water conservancy work. The author analyzessalthezation amelioration by using measures concerning subsuffoce water regulation.Ih addition to water conservancy measures, thes paper also descnbes acomprehensive way to ameliorate salthezation in northem NCP. Finally, the authorstresses the necessity of combining all measures together into a whole system forsolving salinization problems in northem NCP.

An Analysis of Groundwater in Sinjar Plain (Northwest of Iraq) Using WQI Model

Sinjar plain-northwest Iraq has an abundant amount of groundwater. Due to the importance of this water source, the water quality index (WQI) model was used in the classification of groundwater in the western and eastern regions of Sinjar plain for beneficial use. Groundwater samples were chemically analyzed to calculate the values of WQI. This model consists of a single number of the integrated deviation from standard quality, which indicates the relative importance of each relevant variable for beneficial use. The results indicate that the WQI could be used to determine the particular uses of groundwater. The groundwater in the Sinjar plain is more suitable for irrigation than for livestock drinking and domestic use.

Groundwater Flow Simulation and its Application in Groundwater Resource Evaluation in the North China Plain,China

The purpose of this study is to establish a 3D groundwater flow modelling for evaluating groundwater resources of the North China Plain. First, the North China Plain was divided into three aquifers vertically through a characterization of hydrogeological conditions. Groundwater model software GMS was used for modeling to divide the area of simulation into a regular network of 164 rows and 148 lines. This model was verified through fitting of the observed and the simulated groundwater flow fields at deep and shallow layers and comparison between the observed and simulated hydrographs at 64 typical observation wells. Furthermore, water budget analysis was also performed during the simulation period （2002-2003）. Results of the established groundwater flow model showed that the average annual groundwater recharge of the North China Plain during 1991 to 2003 was 256.68x10s m3/yr with safe yield of groundwater resources up to 213.49x10s m3/yr, in which safe yield of shallow groundwater and that of deep groundwater was up to 191.65x10s m3/yr and 22.64x10s m~/yr respectively. Finally, this model was integrated with proposal for groundwater withdrawal in the study area after commencement of water supply by South-North Water Transfer Project, aiming to predict the changing trend of groundwater regime. As indicated by prediction results, South-North Water Transfer Project, which is favorable for effective control of expansion and intensification of existing depression cone, would play a positive role in alleviation of short supply of groundwater in the North China Plain as well as maintenance and protection of groundwater.

Effect of water fluctuation on agricultural production in the Huang-Huai-Hai Plain, China

The biggest load of water resources for agricultural economy in the Huang-Huai Plainwill only arcount for 67.1 % of the forecasted irrigated area in 2010. The irrigated area and thequantity of water diverting from the Huanghe River was 2.2 million hm2 and 10.8 billion m3respectively in the lowe reaches of the river in the 1990s. The annual amount of yield increase forgrain is 6.3 billion kg calculated by converting and the annual benefit of yield-increase is 4.4 billionRMB yuan in the irrigated area of the region. The daily economic losses of industry and agricultureby absence of flow in the area in the 1990s is 44. 1 million RMB yuan. The annual water quantity willbe increased by 9.9 billion m3 after diverting water from the Huanghe River and 12.6 billion m3 afterdiverting water from the Changjiang River respectively in the plain in 2010.

Effect of maize sowing area changes on agricultural water consumption from 2000 to 2010 in the West Liaohe Plain, China

The West Liaohe Plain is located in the eastern Inner Mongolia, known as the golden maize belt in China, where maize acreage has continued to rise in recent years. Water is the main limiting factor for maize production in the region, therefore, this study calculated the effect of maize sowing area changes on agricultural water consumption in the West Liaohe Plain in 2000, 2005 and 2010, based on remote sensing and meteorological data. Maize remote sensing classification was con- structed based on moderate-resolution imaging spectroradiometer, normalized difference vegatation index （MODIS NDVI） data. Then the maize sown area and water requirement and irrigation water resources were investigated. Finally, the effect of the maize sowing area changes on agricultural water consumption in the West Liaohe Plain was systematically analyzed in 2000, 2005, and 2010. The results showed that maize sown areas rose from 2000 to 2010 and were concentrated in the center of the West Liaohe Plain. Average per unit maize water deficit amount also increased in an uneven distribution, increasing from the south, east and north to the center and west of the West Liaohe Plain. The per unit area maize water deficit increased from 2000 to 2010, and reached 266 mm in 2000, 272 mm in 2005 and 273 mm in 2010, respectively. and the study concluded that water deficit during the whole growth period of maize in the West Liaohe Plain was defined by a single peak curve. The maize water requirements increased with maize sowing area changes from 2000 to 2010, and the maize water requirements increased from 0.89 billion m3 in 2000 to 1.19 billion m3 in 2005, and 1.21 billion m3 in 2010.

Assessment of deep groundwater over-exploitation in the North China Plain

A series of environmental—geological problems have been caused by over-exploitation of deep groundwater（i.e.,confined aquifer water） in the North China Plain.In order to better understand the status of deep groundwater over-exploitation and the resultant environmental—geological problems on a regional scale,the over-exploitation of groundwater has been assessed by way of the groundwater exploitation potential coefficient（i.e.,the ratio of exploitable amount of deep groundwater to current exploitation）, cumulative land subsidence,and long-term average lowering rate of the groundwater table.There is a good correlation among the results calculated by the different methods.On a regional scale,deep groundwater has been over-exploited and there is no further exploitation potential under the current conditions.The groundwater exploitation degree index takes the exploitation in 2003 as the reference for the calculations, so the results mainly reflect the degree of current groundwater exploitation.The results of over-exploitation of deep groundwater obtained by land subsidence data and long-term average rate of depression of the water table mainly reflect environmental—geological problems caused by exploitation of deep groundwater.

The supporting capability of Water and land resources for sustainable increase of yield in North China Plain

The potential of yield increase in the North China Plain is about 30 billion kg by ameliorating the low yield and medium low yield farmlands and 4 billion kg by reclaiming unused land. Water shortage will be the main limitation to the further increase of grain crop yield. The amount of water shortage is 8 200 million m3 at present, and will be 17 720 million m3 in 2 000. Yield increase can not be realized by using more water in the future. Other factors such as decrease of the area of cultivated land and the grain crop growing area, deterioration of environment and destruction of resources will also affect the development of grain production. Some suggestions have been proposed in the paper for attaining sustainable increase of yield in the plain.

The renewability and quality of shallow groundwater in Sanjiang and Songnen Plain, Northeast China

Groundwater is a key component for water resources in Sanjiang and Songnen Plain, an important agriculture basement in China. The quality and the renewability of irrigation groundwater are essential for the stock raising and agricultural production. Shallow groundwater was sampled and analyzed for various variables. The salinity sodium concentration and bicarbonate hazard, were examined with regard to the United States Department of Agriculture （USDA） irrigation water standards. The concentration of chlorofluorocarbons （CFCs） was determined to analyze the age of groundwater. Most groundwater samples labeled as excellent to good for irrigation with low salinity hazard or medium salinity hazard. Four groundwater samples were good and suspected for irrigation with high salinity hazard. Generally groundwater in Sanjiang Plain was younger than the groundwater in Songnen Plain. Meanwhile, groundwater nearby river is younger than the groundwater further away inside the watershed. The mean age of groundwater in Sanjiang Plain is in average of 44.1,47.9 and 32.8 years by CFC-11 （CCI3F）, CFC-12 （CCI2F2） and CFC-113 （C2CI3F3）, respectively. The mean ages of groundwater in Songnen Plain is in average of 46.1, 53.4, and 40.7 years by CFC-11, CFC-12 and CFC-113, respectively. Thus, groundwater nearby rivers could be directly exploited as irrigation water. Partial groundwater has to be processed to lower the salt concentration rather than directly utilized as irrigation water in Songnen Plain. Both water quality and renewability should be put in mind for sustainable agricultural development and water resources management.

Dynamic influence of Holocene characteristics on vadose water in typical region of central North China Plain

In the typical region of central North China Plain, vadose sediments are Holocene sediment strata. With samples from field drillings, the study analyzes the sedimentary characteristics of vadose zone. The study takes the content of silty sand as the basis for sedimentary environment analysis, and the content of clay and sand as the sensitive indicator for sedimentary characteristics. Combining palynology analysis, the study divides vadose zone from top to bottom into diluvia oxbow lacustrine sediments, lacustrine sediments, lacustrine and swamp sediments, weak palaeohydrodynamic lacustrine sediments and alluvial sediments. Based on the sedimentary characteristics of Holocene strata, it analyzes the changes across depth of vadose zone water potential and matrix potential, obtaining the influence of vadose zone sedimentary characteristics on the migration of water in typical region of central North China Plain.

Study on sea water intrusion into palaeochannels on south coastal plain of the Laizhou Bay by the Bohai Sea

The palaeochannel evolution in the study region is divided into four stages by such methods as 14C dating. Sea water intrusion through palaeochannels has been studied as a focal point. Palaeochannels are the main passageways through which the sea water intrudes at a higher speed, through many means and in a changeable dynamic state.

Analysis on water supply and demand of North China Plain

A water supply model and a water demand model are developed to exercise resources budgets of the North China Plain with a planning horizon of the year 2030. The budgets indicate that the North China Plain would face serious water stress from 1993 to 2000, and water resources available in the region can not meet the needs of the socioeconomic development and environment from 2000 to 2030. The south/north Water transfer project is the only option to solve the emerging water crisis.

Water use, growth and yield of green gram under rainfed upland crop sequences in Gangetic Plains of Indian sub-tropics

A field experiment was conducted to study the effect of different crop sequences on water use, growth and yield of green gram (Vigna radiate (L) Wilezek) during 1992–93 and 1993–94 under rainfed upland condition in Indo-Gangetic plains of West Bengal. Green gram sown in the month of March as pre-rainy (summer) season crop, as and when the winter crops vacated the land, produced highest dry matter of 372 gm-2 which was significantly highest in black gram-yellow sarson sequence. The results of the field experimentation revealed that green gram gave highest grain yield to the extent of 10.80 q/ha when sown after black gram (rainy season) followed by yellow sarson (winter season) while the crop produced 10.63 q/ha under sesame-yellow sarson sequence. Highest water use of 267 mm was achieved in green gram under black gram-yellow sarson sequence and the crop gave water use efficiency of 4.07 kg ha-1mm-1 under black gram-yellow sarson sequences.

Dynamic Water and Salt Changes in Saline Wasteland on the Lower Edge of Plain Reservoirs in the Desert Oasis Region

In order to reveal the distribution characteristics of water and salt in the non-irrigated saline wasteland and the growth zone of the windbreaks surrounding the plain reservoir,the groundwater and soil monitoring points were set up around the south area of Duolang Reservoir in the desert oasis.Monthly groundwater depth monitoring and soil water content and salt content fixed-point sampling for a period of 2 years were conducted.The results showed that the groundwater depth of salt wasteland in the area around the reservoir area changed slightly during the monitoring period of 2 years,and the average is 1.28 m.The soil moisture content increased with the increase of soil depth,and soil water content of 60-100 cm was larger than that of other soil layers.The salt content of the soil in the salt wasteland varied between 0.48 g/kg and8.86 g/kg in the two years,and the total salt content of different soil decreased with the increase of soil depth.The soil salt content changed greatly in 0-40 cm soil layers,with significant salt accumulation phenomenon.The soil salt content of windbreaks was significantly lower than that of the natural ecological forest.

Application of River Network Hydrodynamic Model in Determining Water Distribution Scale of Haishu Plain

The water distribution network is an important part of the plain water environment improvement system. To make efficient use of the regional water diversion source, scientifically distribute the water diversion flow and improve the water environment carrying capacity of Haishu Plain, the river network hydrodynamic model is used in this paper to simulate the water intake location, reasonable water quantity and influence range of water transfer in Haishu Plain. The simulation results have high accuracy, which can provide a scientific basis for the scale, water transfer mechanism and project layout of water transfer construction in Haishu Plain and show a strong reference value for the study of water diversion and distribution scheme of coastal plain river network.