CAS-based Water Resources Optimal Allocation and Dynamic Simulation for Sewage Irrigation Area

Based on the theory of complex adaptive system(CAS),the optimal allocation model of water resources in sewage irrigation areas was established,which provided new ideas and application value for the rational utilization of agricultural production and waste water resources.The results demonstrated that the difference of crop energy capture mainly depended on the development stage.Waste water with a certain concentration was able to promote crop growth,while excessive concentration inhibited crop growth.The correlation between water absorption rate and leaf area index was close(R=0.9498,p<0.01).The amount of bad seeds increased at a speed of 34.7·d^-1,when system irrigated randomly in the seedling stage,while it tended to remain stable at a speed of 0.3·d^-1 after plants entering the mature stage which impacted the total yields of crops.

Determination of trace lead in rice of sewage irrigation by graphite furnace atomic-absorption spectrometry

The early literatures reported that a lot of matrix interference were encounted in the determination of lead content in various samples. Chlorides produced serious interference on analysis of lead content. All acids except phosphoric acid reduced sensitivity of determination of Pb. Hinderberger et al.reported that lead was determined without the interference could be removed by using NH4H2PO4 as matrix modifier in L’vov platform atomization. The combination of pyrolytic graphite tube with solid pyrolytic graphite platform and Zeeman background correction technique was used in our experiments for determination of lead content in rice samples, with 0.1% Mg(NO)and 2% NHHPOas matrix modifier.

Distribution of Arsenic in Sewage Irrigation Area of Pearl River Delta,China

The aim of the present work is to investigate the distribution of arsenic（As） in sewage ir-rigation area,to deduce the migration and transformation mechanism of As in soil and groundwater,and to infer the source of As in soil and groundwater.This study is carried out in a sewage irrigation area of the Pearl River Delta,China.Surface water samples,soil samples,and groundwater samples from sewage irrigation area were analyzed for As and other elements.As contents in water samples were analyzed by hydride generation-atomic fluorescence spectroscopy,and As fractionation in soil samples was extracted using a seven-step sequential extraction method according to a seven fraction scheme：water soluble,ion exchangeable,bound to carbonate,weakly bound to organic matter,associ-ated with oxides of iron（Fe） and manganese（Mn）,strongly bound to organic matter,and the residual fraction.Waste water has content of As up to 16.8 μg/L in the study area.Soil has enriched As due to the irrigation of soil with waste water,and the total content of As in soil is about 0.7 times higher than the background value.Sequential extraction method reveals that the mean content of residual fraction in soil is more than 70%,releasable fraction（weakly organic fraction,Fe-Mn oxide fraction,and car-bonate fraction） is about 20%-30%,whereas strongly organic and mobile fractions（water soluble and ion exchangeable） are within 0.2%.In the soil profile,the contents of water soluble,ion exchangeable,and carbonate fraction decrease with the depth,whereas the contents of other fractions are irregular with the depth.Using correlation analysis,it is concluded that water soluble fraction is easy to change into ion exchangeable and carbonate fraction,ion exchangeable fraction is easy to change into carbon-ate and Fe-Mn oxide fraction,and carbonate fraction is easy to change into weakly organic and Fe-Mn oxide fraction in the soil of study area.Organic matter and（hydr）oxides of Fe and aluminium（Al） in soil play an important role in controlling the distribution and mobility of As in soil.As concentrations in groundwater range from 2.8 to 21.0 μg/L,and it is inferred that As from waste water and the release of high As sediment（soil and aquifer medium） are the main sources for high As groundwater in study area.Using cluster analysis,it is concluded that reducing ground-water with slightly alkaline is beneficial to en-richment of As in groundwater,and hydroxides of Fe,Mn,and Al also play a key role for the en-richment of As in groundwater of the study area.

Influence of the sewage irrigation on the agricultural soil properties in Tongliao City, China

Increasing shortages of fresh water has led to greater use of treated wastewater for irrigation of crops. This study evaluates the spatial variability of soil proper- ties after irrigation with wastewater and freshwater. Geostatistical techniques were used to identify the variability of soil properties at the different sites. A set of physical and chemical soil properties were measured including total nitrogen （TN）, total phosphorus （TP）, organic matter （OM） and soil moisture. The TN concen- tration levels varied from 567 to 700 mg. kg-1, while OC levels ranged from 7.3 to 16.3 mg.kg-1 in wastewater- irrigated zones. The concentration levels of TP were between 371.53 and 402.88 mg-kg-1 for the wastewater- irrigated sites. Wastewater irrigation resulted in higher TN, TP and OM concentrations by 18.4%, 8% and 25%, respectively. The highest TN and OM occurred along the wastewater trunk. It was also observed that nitrogen concentrations correlate with the soil＇s organic matter. The increase of salinity may be associated with the increase of pH, which might suggest that a reduction of pH will be beneficial for plant growth due to the decrease of salinity. The average concentrations of nitrogen in topsoil were higher than those in subsurface soils in irrigated areas. Such differences of the N profile might be due to variations in organic matter content and microbial populations. Consistent with TN and OM, soil C：N decreased significantly with an increase of depth. This phenomenon possibly reflects a greater degree of breakdown and the older age of humus stored in the deeper soil layers. The analysis of pH levels at different depths for the three sites showed that pH values for wastewater irrigation were slightly lower than the controlled sites at the same depths.

The soil displacement measurement of mercury emission flux of the sewage irrigation farmlands in Northern China

Mercury fate of sewage irrigation in farmlands deserves attention with increasing scarcity of freshwater resources for agriculture in the worldwide.Soil-air total gaseous mercury(TGM)fluxes from four-sewage and one-fresh water irrigated farmlands were determined simultaneously.During maize-wheat rotation,soil-air TGM fluxes showed patterns of both emission and deposition during different growth stages.It enhanced one-order of magnitude emission with increased Hg contamination from historical sewage irrigation.A linear response relationship of TGM fluxes with soil Hg concentration was found,which showed greater TGM emission potential comparing with those from forest and urban soils.However,the ratio of soil-air TGM flux in daytime to nighttime were 3.94 in maize-season and 3.41 in wheat-season,respectively,which were little related to the change in soil Hg concentration.Furthermore,soil temperature and moisture,ambient-air TGM concentration all effected TGM evasion from sewage-irrigated soils.The data presented here suggest that evasion of TGMfromhistorical sewage irrigation farmlands with high Hg concentrations may be potential hotspots for Hg emission in atmosphere,and it was likely to underestimate Hg emissions from farmlands in existing emissions inventory.Additional regionalinvestigations and process-level researches are needed to better understand role of sewage irrigation farmlands in local-global Hg-biogeochemical-cycles.

Temporal-spatial distribution and variability of cadmium contamination in soils in Shenyang Zhangshi irrigation area,China

Heavy metal contamination in soils has been of wide concern in China in the last several decades. The heavy metal contamination was caused by sewage irrigation, mining and inappropriate utilization of various agrochemicals and pesticides and so on. The Shenyang Zhangshi irrigation area （SZIA） in China is a representative area of heavy metal contamination of soils resulting from sewage irrigation for about 30 years duration. This study investigated the spatial distribution and temporal variation of soil cadmium contamination in the SZIA. The soil samples were collected from the SZIA in 1990 and 2004; Cd of soils was analyzed and then the spatial distribution and temporal variation of Cd in soils was modelled using kriging methods. The kriging map showed that long-term sewage irrigation had caused serious Cd contamination in topsoil and subsoil. In 2004, the Cd mean concentrations were 1.698 and 0.741 mg/kg, and the maxima 10.150 and 7.567 mg/kg in topsoils （0-20 cm） and subsoils （20-40 cm） respectively. These values are markedly more than the Cd levels in the second grade soil standard in China. In 1990, the Cd means were 1.023 and 0.331 mg/kg, and the maxima 9.400 and 3.156 mg/kg, in topsoils and subsoils respectively. The soil area in 1990 with Cd more than 1.5 mg/kg was 2701 and 206.4 hnl2 in topsoils and subsoils respectively; and in 2004, it was 7592 and 1583 hm^2, respectively. Compared with that in 1990, the mean and maximum concentration of Cd, as well as the soil area with Cd more than 1.5 mg/kg had all increased in 2004, both in topsoils and subsoils.

Chemically Induced Bioremediation of Heavy MetalContaminated Sewage-irrigated Soils in Tianjin Municipality

Festuca arundinacea L.was planted in sewage-irrigated soils from the sewage irrigation regions of Tianjin.Different concentrations of nitrilotriacetic acid（NTA）and sodium dodecylsulphate（SDS）were applied in bioremediation of Cd,Cu and Zn in sewage irrigation regions.According to the results,under the treatment of 15 mmol/kg NTA＋1 mmol/kg SDS,the concentrations of Cd and Zn reached the highest in shoots of F.arundinacea,which were 3.03 and 9.28 times over that in control,respectively;the concentrations of Cd and Zn in roots of F.arundinacea displayed the same trend as shoots.The combined addition of surfactant SDS and chelator NTA significantly increased Cd concentration in F.arundinacea,but the effect was not significant on Cu enrichment.Considering comprehensively the biomass,bioaccumulation effect and economic cost,it is economical and effective to remediate heavy metal-contaminated sewage-irrigated soils with 5mmol/kg NTA＋1 mmol/kg SDS or 10 mmol/kg NTA＋1 mmol/kg SDS.

Ecological engineering land treatment systems──A new development in China

This paper elucidated the necessity and possibility of developing the technology of land treatment on the basis of the analysis of shortage and pollution status of water resources in China.The historical development of this technology in the world was briefly reviewed and the distinction between land treatment and conventional wastewater irrigation was discussed in details. The fundamental characteristics and functions as well as the integrity and compatibility of this ecological engineering were also summarized. It was finally concluded that this technology for wastewater treatment has broad prospects of application in China.

Distribution and migration of lead in soil of Xiao River, Shijiazhuang, Hebei Province

The Xiao River sewage irrigation area in Luancheng where wastewater from Shijiazhuang flows through was taken as the research area. Five groundwater monitoring wells were set perpendicular to Xiao River, the research reveals the migration law and distribution characteristics of poisonous metal lead, through collecting and analyzing soil samples at different depths, investigating lithologic structure and pollution. The result shows that soil type has great impact on vertical lead distribution in aeration zone, which means that lead concentrates more in clay than in sand. Lead migrates fast in silty soil and silty clay, but slow in sand. The content of lead soil adsorbed decreases with grain size increasing. The most important factor influencing the distribution of lead is the soil type.

Distribution of rare earth elements in sewage-irrigated soil profiles in Tianjin,China

The concentrations of rare earth elements （REEs） in the soil extracts and soil solutions from two different alluvial soil profiles irrigated with sewage were measured using inductively coupled plasma-mass spectrometry. The results showed that the REE concentrations in the soil extracts from soil samples affected by sewage irrigation were much higher than those in virgin soil samples. The REE concentrations in the soil extracts of the rhizophere soil were higher than those of the non-rhizophere soil. The shale-normalized REE patterns in the soil extracts from the upper soil layer affected by sewage irrigation shown middle REE （MREE） enrichment relative to light REE （LREE） and heavy REE （HREE）. This result was attributed to the MREE-rich organic colloidal material, REE-HM （humic and fulvic acids） and phosphate-REE complexations. The REE patterns in the soil extracts from deep soil little-affected by sewage irrigation showed HREE enrichment relative to LREE, which might have been caused by the preferential complexation of HREE with carbonate. The normalized La/Yb ratios in the soil extracts increased with the decrease in depth. The sewage irrigation did not affect the total REE contents and REE pattern in the soil profiles.

Copper Residue in Animal Manures and the Potential Pollution Risk in Northeast China

A total of 224 animal manures and feeds, randomly sampled from different sizes of intensive farms in three northeastern provinces, were analyzed to determine Cu concentration. At the same time, the load of animal manure Cu on farmlands and loss to rivers in sewage irrigation areas of Liaoning Province was estimated. The results showed that the mean Cu concentrations in pig, cattle, and chicken feeds were 179.8, 16.6 and 20.8 mg kg-1, respectively. Cu concentrations in manures ranged from 1.5 to 1521.2 mg kg-1. The mean value of 642.1 mg kg-1 in pig manure was higher than the mean values of 65.6 mg kg-1 and 31.1 mg kg-1 in chicken and cattle manures, respectively. The load of animal manure Cu on farmland in the study area ranged from 12.3-35.4 kg km-2 annually. In particular, the Xiaolinghe area received a higher level than the other areas. The possible amount of manure Cu entering river water as a result of soil erosion was lower than 0.76 kg km-2. The highest loss rates were found in the south of Anshan and the west of Jinzhou. It is suggested that animal manures contain a high level of Cu. Long-term agricultural application of animal manure may increase the potential risk of Cu pollution in soil and surface water.

Heavy Metal Contamination of Agricultural Soils in Taiyuan, China

To evaluate the current state of the environmental quality of agricultural soils in Taiyuan City, a hotspot for China's industrial development, the concentrations of 8 heavy metals in soils were investigated by means of extensive sampling in farmlands, forestlands,and grasslands in the city. Statistical analyses and spatial distribution maps were used to identify the most significant heavy metal pollutants. The mean concentrations of As, Cd, Cu, Hg, Pb, Zn, Ni, and Cr were slightly higher than their background values in Taiyuan's topsoil, but were lower than the maximum permissible concentrations in the Chinese Environmental Quality Standard for agricultural soils. Farmland soils in Taiyuan had the highest average Cd, Cu, Hg, Pb, Zn, and Cr concentrations, but the As and Ni concentrations did not differ significantly among the farmland, forestland, and grasslands. Soil contamination by Cd, Cu, Hg, Pb,Zn, and Cr was mainly derived from farming practices, especially the use of sewage water for irrigation. In contrast, As and Ni might derive mainly from the soil parent material. The identification of heavy metal sources in agricultural soils may provide a basis for taking appropriate action to protect soil quality.

Modeling Cadmium Transport in Neutral and Alkaline Soil Columns at Various Depths

Human health has been potentially threatened by cadmium (Cd) contained in sewage irrigation water.Previous studies of Cd transport in soils were mainly conducted using small soil cores with pH values less than 6.The objectives of this study were to determine the parameters of the convection-dispersion equation (CDE) for Cd transport in relatively larger columns with neutral and alkaline soils,and to investigate the parameters' variability with depth.The soil columns were 50 cm in length and 12.5 cm in diameter.Ceramic suction lysimeters were buried at depths of 2.5,7.5,17.5,27.5,and 37.5 cm to abstract soil solution.Cd concentration in the soil solution samples were subsequently analyzed to obtain breakthrough curves (BTCs).Equilibrium and nonequilibrium models in CXTFIT program were used to estimate parameters of the CDE.The results suggested that both equilibrium and non-equilibrium models performed well in modeling Cd transport.The hydrodynamic dispersion coefficient (D) ranged from 0.18 to 10.70 cm 2 h 1,showing large differences among different depths.The retardation factor (R d) ranged from 25.4 to 54.7 and the standard deviation of R d value was lower than 30% of the mean value.Precipitation coefficient (R p) decreased consistently with increasing depth,varying from 1.000 × 10 10 to 0.661 h 1.Sensitivity tests showed that D was less sensitive than R d.These results would be helpful in understanding the transport and retention of Cd in non-acidic soils.