Search

Soil phosphomonoesterase plays a critical role in controlling phosphorus (P) cycling for crop nutrition, especially in P-deficient soils. A 6-year field experiment was conducted to evaluate soil phosphomonoesterase activities, kinetics and thermodynamics during rice growth stages after consistent swine manure application, to understand the impacts of swine manure amendment rates on soil chemical and enzymatic properties, and to investigate the correlations between soil enzymatic and chemical variables. The experiment was set out in a randomized complete block design with three replicates and five treatments including three swine manure rates (26, 39, and 52 kg P ha−1, representing low, middle, and high application rates, respectively) and two controls (no-fertilizer and superphosphate at 26 kg P ha−1). The results indicated that the grain yield and soil chemical properties were significantly improved with the application of P-based swine manure from 0 to 39 kg P ha−1; however, the differences between the 39 (M39) and 52 kg P ha−1treatments (M52) were not significant. The enzymatic property analysis indicated that acid phosphomonoesterase was the predominant phosphomonoesterase in the tested soil. The M39and M52treatments had relatively high initial velocity (V0), maximal velocity (Vmax), and activation grade (lgNa) but low Michaelis constant (Km), temperature coefficient (Q10), activation energy (Ea), and activation enthalpy (ΔH), implying that the M39and M52treatments could stimulate the enzyme-catalyzed reactions more easily than all other treatments. The correlation analysis showed that the distribution of soil phosphomonoesterase activities mainly followed the distributions of total C and total N. Based on these results, 39 kg P ha−1could be recommended as the most appropriate rate of swine manure amendment.

The comprehensive assessment of environmental quality is useful for comparison of environmental quality and identification of pollution trends. In the comprehensive assessment methods, many studies proved that grey clustering method is accurate and effective. However, the zero-weight problem occurs in the traditional grey clustering method (TGCM). This flaw may lead to the assessment result distortion. To solve this problem, this paper proposes a modified grey clustering method (MGCM) in which the linear whitening functions in the traditional grey clustering method is replaced by exponential functions. The modified method was applied to assess water quality of four monitoring sections in the Yuhang section of the Tiaoxi River. Then, the results were compared with those obtained with the TGCM. The comparisons show that solving the zero-weight problem can lead to different assessment results and the MGCM is effective to solve the zero-weight problem. The MGCM is more accurate than the TGCM.

A field experiment was conducted to remove the potential eutrophication effect of N and P from rural wastewater (RW) during the whole rice growing season of 2010. Commercial fertilizer and RW were applied to furnish 40 kg P ha-1except CK. Results showed TN concentration of the floodwater in the paddy wetland system decreased quickly after transplanting, rosed significantly (P = 0.05) after two N topdressings, and then decreased gradually as the following sequences: SW > GW > DW > BW > CK. Total P (TP) concentration had significantly declined after P application, from October 15 there were no significant increases in TP concentration in the floodwater. Meanwhile, the yield for CK was significantly less (P =0.05) than SW, GW, DW, and BW, with the yield of BW significantly greater (P = 0.05) than other treatments. It is feasible to remove N and P from RW by the paddy wetland system and can be widely used to improve the yield of rice.

A near‐trench paddy field experiment with five urea application rates (0–360 kg N ha−1in 90‐kg increments) was conducted on a paddy soil in the Taihu Lake Region of China to elucidate N losses through lateral seepage during three rice (Oryza sativaL.) growing seasons. The total N (Nt), NH4+–N, and NO3−‐N concentrations in the lateral seepage water increased with increasing N rates. The seasonal Ntfluxes by lateral seepage varied from 6.8 to 25.6 kg N ha−1for urea application rates of 90 to 360 kg N ha−1Lateral seepage accounted for 4.7 to 6.6% of the Ntapplied, implying that lateral seepage was an important pathway of N loss from near‐trench paddy fields. The cumulative N loss via lateral seepage was significantly related to N fertilization rate (P= 0.05). Floodwater level was also identified as a main factor affecting N losses via lateral seepage from paddy fields, as indicated by a positive linear relationship (R2= 0.43) between floodwater level and daily lateral flow during the flooded period (P= 0.05). Under the conditions of these experiments, a shallow floodwater depth of 50 mm, urea application rates of 90 kg N ha−1or less, and no rainfall within 1 wk after N application reduced N losses by lateral seepage from paddy fields.

Electricity consumption increases rapidly with the rapid development of China. The environmental damage costs of electricity generation are very important for both policy analysis and the proper management of the environment. A method was developed in this work to estimate gross environmental damage costs according to emission inventory and environmental cost factors, and to extend the costs from provincial to national level with population density. In this paper, sulfur dioxide (SO2), nitrogen oxides (NOx), particulate matter less than 10 μm in diameter (PM10), and carbon dioxide (CO2) from fossil fired power plants over 6000 kW were selected as index pollutants to quantify the environmental costs of damages on human health and global warming. With the new developed method, environmental damage costs, caused by 3 types of fired power plants in 30 provinces and 6 economic sectors during the years 2000 to 2003, were evaluated and analyzed. It can be seen that the calculated total national environmental damage costs of electricity have rapidly increased from 94930.87 × 106USD in 2000 to about 141041.39 × 106USD in 2003, with an average annual growth rate of 14.11%. Environmental damage costs of SO2, NOx, PM10, and CO2are 69475.69 × 106, 30079.29 × 106, 28931.84 × 106, and 12554.57 × 106USD and account for 49.26%, 21.33%, 20.51%, and 8.90% of total environmental costs in fossil electricity generation, respectively. With regard to regional distribution, external costs caused by fossil electricity generation are mainly concentrated in the more populated and industrialized areas of China, i.e., the Eastern Central and Southeastern areas.