Spatial Variation of P and N in Water and Sediments of Dianchi Lake, China

Dianchi Lake is one of the most eutrophic lakes in China. In order to understand this eutrophication and to help control the pollution, this research investigated the spatial distribution of Kjeldahl nitrogen (K-N) and total phosphorus(TP) through analysis of bottom water and sediment (3 depths) samples collected at 118 sites around Dianchi Lake. The concentrations of K-N and TP for the lake bottom water in the Caohai part of the lake were much higher than those in the Waihai part, generally decreasing from north to south. In the sediments, the K-N concentration was higher in the Caohai part and the middle of the Waihai part. On the other hand, TP in the sediments was greater in the southern and western parts. Both K-N and TP had similar spatial distributions for the sediment samples of three different depths.Vertically, the K-N and TP concentration in the sediments decreased with an increase in depth. This was evidence that eutrophication and pollution of Dianchi Lake was becoming gradually more severe. Exterior factors including uncontrolled input of domestic and industrial effluents as well as non-point pollution around the lake were the main reasons for serious eutrophication; therefore, controlling these was the first step in reducing eutrophication of Dianchi Lake.

Quantifying Responses of Winter Wheat Physiological Processes to Soil Water Stress for Use in Growth Simulation Modeling

A deep understanding of crop-water eco-physiological relations is the basis for quantifying plant physiological responses to soil water stress. Pot experiments were conducted to investigate the winter wheat crop-water relations under both drought and waterlogging conditions in two sequential growing seasons from 2000 to 2002, and then the data were used to develop and validate models simulating the responses of winter wheat growth to drought and waterlogging stress. The experiment consisted of four treatments, waterlogging (keep 1 to 2 cm water layer depth above soil surface), control (70%-80% field capacity), light drought (40%-50% field capacity) and severe drought (30%-40% field capacity) with six replicates at five stages in the 2000-2001 growth season. Three soil water content treatments (waterlogging, control and drought) with two replicates were designed in the 2001-2002 growth season. Waterlogging and control treatments are the same as in the 2000-2001 growth season. For the drought treatment, no water was supplied and the soil moisture decreased from field capacity to wilting point. Leaf net photosynthetic rate, transpiration rate, predawn leaf water potential, soil water potential, soil water content and dry matter weight of individual organs were measured. Based on crop-water eco-physiological relations, drought and waterlogging stress factors for winter wheat growth simulation model were put forward. Drought stress factors integrated soil water availability, the sensitivity of different development stages and the difference between physiological processes (such as photosynthesis, transpiration and partitioning). The quantification of waterlogging stress factor considered different crop species, soil water status, waterlogging days and sensitivity at different growth stages. Data sets from the pot experiments revealed favorable performance reliability for the simulation sub-models with the drought and waterlogging stress factors.

Revegetation of Copper Mine Tailings with Ryegrass and Willow

To restore vegetation on metal mine tailings is very difficult because theyoften contain high concentrations of heavy metals, low nutrient content and low water retentioncapacity. This study involved 3 experiments that evaluated the effects of 4 treatment amendments:montmorillonite, rice straw, organic manure and chemical fertilizer on the growth of ryegrass(Lolium perenne L.) and willow (Salix viminalis L.) with Cu and Zn mine tailings from two miningareas. The results showed that ryegrass was the most tolerant of 4 crops to Cu toxicity. Also whenorganic manure, which contained high concentrations of inorganic salts, was added to the minetailings, it significantly hindered ryegrass growth (P = 0.05). Meanwhile, with ryegrass organicmanure significantly increased (P = 0.05) the extractable Cu concentration in both mine tailings.When montmorillonite was used as a mine tailings amendment with willow, the height and tress numberat the 1st cut were significantly greater (P = 0.05) than a control without montmorillonite. Howeverthere was no significant difference for height, tress number, dry weight or root dry weight at the2nd cut. So, amendment applications to reduce metal toxicity and increase nutrients retention inmine tailings were essential during revegetation of mine tailings.

Using GIS Spatial Distribution to Predict Soil Organic Carbon in Subtropical China

Spatial distribution of organic carbon in soils is difficult to estimatebecause of inherent spatial variability and insufficient data. A soil-landscape model for a region,based on 151 samples for parent material and topographic factors, was established using a GISspatial analysis technique and a digital elevation model (DEM) to reveal spatial distributioncharacteristics of soil organic carbon (SOC). Correlations between organic carbon and topographicfactors were analyzed and a regression model was established to predict SOC content. Results forsurface soils (0-20 cm) showed that the average SOC content was 12.8 g kg^(-1), with the SOC contentbetween 6 and 12 g kg^(-1) occupying the largest area and SOC over 24 g kg^(-1) the smallest. Also,soils derived from phyllite were the highest in the SOC content and area, while soils developed onpurple shale the lowest. Although parent material, elevation, and slope exposure were allsignificant topographic variables (P < 0.01), slope exposure had the highest correlation to SOCcontent (r = 0.66). Using a multiple regression model (R^2 = 0.611) and DEM (with a 30 m X 30 mgrid), spatial distribution of SOC could be forecasted.

Estimate of CH_4 Emissions from Year-Round Flooded Rice Fields During Rice Growing Season in China

A special kind of rice field exists in China that is flooded year-round. These rice fields have substantially large CH4 emissions during the rice-growing season and emit CH4 continuously in the non-rice growing season. CH4 emission factors were used to estimate the CH4 emissions from year-round flooded rice fields during the rice-growing season in China. The CH4 emissions for the year-round flooded rice fields in China for the rice growing season over a total area of 2.66 Mha were estimated to be 2.44 Tg CH…

Soil Organic Carbon Density in Hebei Province, China: Estimates and Uncertainty

In order to improve the precision of soil organic carbon (SOC) estimates, the sources of uncertainty in soil organic carbon density (SOCD) estimates and SOC stocks were examined using 363 soil profiles in Hebei Province, China, with three methods: the soil profile statistics (SPS), GIS-based soil type (GST), and kriging interpolation (KI). The GST method, utilizing both pedological professional knowledge and GIS technology, was considered the most accurate method of the three estimations, with SOCD estimates for SPS 10% lower and KI 10% higher. The SOCD range for GST was 84% wider than KI as KI smoothing effect narrowed the SOCD range. Nevertheless, the coefficient of variation for SOCD with KI (41.7%) was less than GST and SPS. Comparing SOCD’s lower estimates for SPS versus GST, the major sources of uncertainty were the conflicting area of proportional relations. Meanwhile, the fewer number of soil profiles and the necessity of using the smoothing effect with KI were its sources of uncertainty. Moreover, for local detailed variations of SOCD, GST was more advantageous in reflecting the distribution pattern than KI.

Chemical Criteria to Assess Risk of Phosphorus Leaching from Urban Soils

Soils from urban and suburban areas are normally enriched with phosphorus (P). Sixteen urban soils with a wide range of total P concentrations under typical urban land uses were sampled and analyzed for extractable P concentrations using water, sodium bicarbonate and citric acid. Meanwhile the soils were artificially leached in columns and P concentrations in the leachates were determined. With linear regression a two-stage linear relationship was found to exist between concentrations of P in the leachates …

Lake Sediments from Dianchi Lake:A Phosphorus Sink or Source?

Dianchi Lake is a highly eutrophic lake in southwestern China where phosphorus (P) is the limiting element for eutrophication and where lake sediments play an important role in the P cycle. One hundred and eighteen sites were sampled throughout Dianchi Lake in 2002 to investigate the P loading of the lake sediments, while fresh surface sediments were studied in the laboratory to clarify its role for phosphorus. The results showed that concentrations of total phosphorus (TP) in sediments were very high, with a maximum value of 6.66 g kg-1, and decreased with sediment depth. P adsorption on surface sediments was rapid with adsorption amounts higher in acidic than in alkaline conditions. The release experiments showed that P release increased as pH rose from 7.0 to 10.5. Additionally, compared with aerobic conditions, P release was much higher under anaerobic conditions, especially with low P content in the lake water. At present, the sediments in Dianchi Lake still function as a sink for phosphorus at high P levels in lake water. However, if the external P load was reduced and P content in lake water became low, the sediment would have a large potential for P release under anaerobic conditions.

Responses of Different Pakchoi (Brassica chinensis L.) Cultivars to Cu Toxicity

Two pot experiments with a completely random design and 4 replications were performed in a greenhouse to examine the response difference of 17 cultivars of pakchoi (Brassica chinensis L.) grown in a Cu-spiked and a clean soil to Cu. The response of pakchoi to Cu toxicity varied with the cultivars. The biomass in cultivars of Gaogengbai , Siyueman and Suzhouqing were sensitive to soil Cu pollution, but the cultivars of Heixinwu , Huoqingcai and HKcaixin were relatively tolerant. When the 17 cultiva…

Interaction of NPK Fertilizers During Their Transformation in Soils: Ⅲ. Transformations of Monocalcium Phosphate

Interactions of N, P and K fertilizers in soil-plant systems are widelyrecognized. This study focused on the transformations of monocalcium phosphate (Ca(H_2PO_4)_2) (MCP)with co-application of ammonium and potassium fertilizers in three different soils. The resultsshowed that after 1 d incubation a large portion of the MCP applied in the paddy, calcareous and redsoils became the water-insoluble form and the recoveries of P applied as Olsen P varied greatly inthese three soils. Application of ammonium sulfate ((NH_4)_2SO_4) (AS) or potassium chloride (KCl)reduced WSP significantly the soils with AS more effective than KCl in the calcareous soil, whilethe reverse occurred in the red soil. Meanwhile, in the paddy soil, co-application of the twofertilizers reduced WSP more than when the fertilizers were applied individually. The co-applicationof AS with MCP in the paddy and calcareous soils significantly reduced Olsen P, but the oppositeoccurred in the red soil. The experiment on the effect of different accompanying anions showed thatthe ammonium fertilizers (PNCl and PNS) reduced WSP more effectively than the correspondingpotassium fertilizers (PKCl and PKS) in the calcareous soil due to the difference of the cations,whereas in the red soil, the chlorides reduced WSP more effectively than the sulfates. Overall,co-application of ammonium or potassium fertilizers with MCP significantly decreased availability ofP from MCP during its transformation in soils, especially when MCP was applied in combination withammonium in the calcareous soil.

Atmospheric Sulfur Deposition on Farmland in East China

Atmospheric sulfur deposition onto typical farmland in East China was investigated using both field measurements and numerical modeling. The field measurements were conducted at the Experiment Station of Red Soil Ecology, Chinese Academy of Sciences, 10 km from Yingtan, Jiangxi Province, East China, between November 1998 and October 1999, and at the Changshu Ecological Experiment Station, Chinese Academy of Sciences, in a rapidly developing region of Jiangsu Province, East China, between April 2001 and Marc…

Cadmium adsorption in montmorillonite as affected by glyphosate

Behaviors of soil heavy metals are often affected by coexisting herbicides due to their physical and chemical interaction. Effect of glyphosate, an herbicide containing -PO 2- 3 and -COOH groups, on cadmium adsorption in montmorillonite was studied in detail. The results showed that the cadmium adsorption quantity in montmorillonite increased with increasing soil solution pH and cadmium concentration as usual, but decreased with glyphosate, which is due to the formation of a low affinity complex of Cd and glyphosate and decreasing solution pH induced by glyphosate addition. When the equilibrium solution pH was below 6.7, glyphosate has little effect on cadmium adsorption, but when the equilibrium solution pH was above 6.7, glyphosate significantly decreased cadmium adsorption quantity in montmorillonite. In addition, the adding order of Cd and glyphosate also influenced Cd adsorption quantity in montmorillonite.

Atmospheric Sulfur Deposition for a Red Soil Broadleaf Forest in Southern China

A two-year study in a typical red soil region of Southern China was conductedto determine 1) the dry deposition velocity (V_d) for SO_2 and particulate SO_4^(2-) above abroadleaf forest, and 2) atmospheric sulfur fluxes so as to estimate the contribution of variousfractions in the total. Using a resistance model based on continuous hourly meteorological data,atmospheric dry sulfur deposition in a forest was estimated according to V_d and concentrations ofboth atmospheric SO_2 and particulate SO_4^(2-). Meanwhile, wet S deposition was estimated based onrainfall and sulfate concentrations in the rainwater. Results showed that about 99% of the drysulfur deposition flux in the forest resulted from SO_2 dry deposition. In addition, the observeddry S deposition was greater in 2002 than in 2000 because of a higher average concentration of SO_2in 2002 than in 2000 and not because of the average dry deposition velocity which was lower for SO_2in 2002. Also, dry SO_2 deposition was the dominant fraction of deposited atmospheric sulfur inforests, contributing over 69% of the total annual sulfur deposition. Thus, dry SO_2 depositionshould be considered when estimating sulfur balance in forest ecological systems.

Electrokinetic removal of chromium and copper from contaminated soils by lactic acid enhancement in the catholyte

The electrokinetic removal of chromium and copper from contaminated soils by adding lactic acid in cathode chamber as an enhancing reagent was evaluated. Two sets of duplicate experiments with chromium contaminated kaolinite and with a silty soil sampled from a superfund site in California of USA and polluted by Cr and Cu, were carried out in a constant current mode. Changes of soil water content and soil pH before and after the electrokinetic experiments, and variations of voltage drop and electroosmosis flow during the treatments were examined. The results indicated that Cr, spiked as Cr(Ⅵ) in the kaolinite, was accumulated mainly in the anode chamber, and some of Cr and metal hydroxides precipitated in the soil sections in contact with the cathode, which significantly increased electrical energy consumption. Treatment of the soil collected from the site showed accumulation of large amounts of Cr and Cu in the anode chamber while none was detected in the cathode one. The results suggested that the two metals either complexed with the injected lactic acid at the cathode or existed as negatively charged complex, and electromigrated toward the anode under a voltage gradient.

IMPLEMENTATION OF CLEANER PRODUCTION STRATEGIES TOWARDS A SUSTAINABLE CITY

Rapid urbanization and growing size of cities will have an increasing impact on the global environment in the 21st century. As an engine of urban development to drive economic growth and technological innovations, industry has moved its focus from controlling environmental hazards to stimulating sustainable industrial development throughout the entire product lifecycle. These process- and technology-driven innovations for industrial production are prerequisites for enhancement of urban environment and sustainable development of cities. In this review, problems of environment and resources scarcity associated with rapid urbanization are demonstrated. And, on the basis of expatiations on the concepts and policies of the cleaner production(CP) and other similar initiatives with the goal of preventing pollution at the source and of managing the raw material more efficiently, two different ways to link the practice of cleaner production in industrial sector with performance of urban environment are discussed in detail. Then, the introduction, practice and legislation of CP strategies in China are outlined, and possibility for China to develop CPC (Cleaner Practices for Cities) approaches in the demonstration cities is discussed. Finally, some suggestions on implementation of CPC strategies are put forward.

Reference benchmarks relating to great groups of genetic soil classification of China with soil taxonomy

Soil classification forms the basis for the ex-change and extension of research findings in soil science and for the modernization of management of soil resources. This paper systematically reviews the compatibility of the genetic soil classification of China (GSCC) and soil taxonomy (ST). This includes a study of the evolution and consummation of the GSCC and assessment of the databases and methods of the study. Using the 揝oil Species of China (six volumes) and some provincial soil species as the basic material, the authors gathered information from 2540 soil species. Based on the key described in ST, the 2540 soil species were taxo-nomically classified into corresponding soil orders, suborders, great groups and subgroups and then matched with corre-sponding map units in the 1︰1000000 digital soil map of China. Using the high-level classification units of the two soil classification systems, and the attributes of each soil species, the sizes of distribution areas were mapped. The soil distri-bution results were analyzed and compared statistically. The reference compatibility between the great groups used in GSCC system and the soil orders of the ST is discussed. It is believed that 20 great groups display maximum referencibil-ity >95% and 15 great groups depict maximum referencibil-ity in the range of 70%—95%, which can be cited as refer-ence benchmarks. The remaining 25 great groups are less compatible (with maximum referencibility <70%) and need further study, or require referencing at lower classification levels or at a regional level to help to improve the accuracy of the reference.