Remediation of potentially toxic trace elements (PTEs) in paddy fields is fundamental for crop safety. In situ application of chemical amendments has been widely adapted because of its cost-effectiveness and environmental safety. The main purpose of this research was to (1) evaluate the reduction in dissolved concentrations of cadmium (Cd) and arsenic (As) with the application of chemical amendments and (2) monitor microbial activity in the soil to determine the remediation efficiency. Three different chemical amendments, lime stone, steel slag, and acid mine drainage sludge, were applied to paddy fields, and rice (Oryza sativa L. Milyang 23) was cultivated. The application of chemical amendments immobilized both Cd and As in soil. Between the two PTEs, As reduction was significant (p < 0.05) with the addition of chemical amendments, whereas no significant reduction was observed for Cd than that for the control. Among six soil-related variables, PTE concentration showed a negative correlation with soil pH (r = ?0.70 for As and r = ?0.54 for Cd) and soil respiration (SR) (r = ?0.88 for As and r = ?0.45 for Cd). This result indicated that immobilization of PTEs in soil is dependent on soil pH and reduces PTE toxicity. Overall, the application of chemical amendments could be utilized for decreasing PTE (As and Cd) bioavailability and increasing microbial activity in the soil. 相似文献
The spontaneous oxidation process of pristine silicon (Si) limits its application as photocatalyst or electrode in aqueous solution or moist air. Covering a protection layer on Si surface is an effective approach to overcome this disadvantage. In this paper, α-Fe2O3 is demonstrated to be an excellent alternative as a protection material. α-Fe2O3 layer was deposited around each p-type Si micropillar (SiMP) in well-ordered array by chemical bath deposition method. The diameter of SiMP was 5 mm and the thickness of α-Fe2O3 layer was about 20 nm. The photoeletrochemical stability of SiMP/α-Fe2O3 was proved by 10 circles cyclic voltammetry testing. Compared with SiMP, its optical absorption and photocurrent density improved 2 times and 4 times, respectively, and its onset potential for hydrogen evolution moved positively about 0.4 V. These improved performances could be ascribed to the enhanced photogenerated-charge-separation efficiency deriving from built-in electric field at the interface between Si and α-Fe2O3. The above results show an effective strategy to utilize Si material as photocatalyst or electrode in aqueous solution or moist air.
Conventional biological removal of nitrogen and phosphorus is usually limited due to the lack of biodegradable carbon source, therefore, new methods are needed. In this study, a new alternative consisting of enhanced biological phosphorus removal (EBPR) followed by partial nitritationanammox (PN/A), is proposed to enhance nutrients removal from municipal wastewater. Research was carried out in a laboratory-scale system of combined two sequencing batch reactors (SBRs). In SBR1, phosphorus removal was achieved under an alternating anaerobic-aerobic condition and ammonium concentration stayed the same since nitrifiers were washed out from the reactor under short sludge retention time of 2–3 d. The remaining ammonium was further treated in SBR2 where PN/A was established by inoculation. A maximum of nitrogen removal rate of 0.12 kg N?m–3?d–1 was finally achieved. During the stable period, effluent concentrations of total phosphorus and total nitrogen were 0.25 and 10.8 mg?L–1, respectively. This study suggests EBPR-PN/A process is feasible to enhance nutrients removal from municipal wastewater of low influent carbon source.
An ideal off-grid island can become 100% energy-sufficient if one installs renewable energy systems such as solar photovoltaic (PV) and wind turbine (WT) systems. However, the intermittent and uncertain nature of the power supply from renewable energy systems hinders a 100% autonomy level (AL) without an infinite energy storage capacity. The thermoeconomic installation limit (TEIL) of a PV/WT hybrid energy system was studied using hourly weather data and the energy demand profile for off-grid islands. An appropriate battery size for the TEIL was also determined. Given the current installation cost of the hybrid energy system and the battery unit, the AL for a PV/WT hybrid energy system at the TEIL is calculated to be approximately 70%. Above the limit, the size of the energy storage unit and, correspondingly, the total annual cost of the PV/WT hybrid energy system increase sharply. 相似文献
In order to assist and optimize the operation of a clean water diversion project for the medium-sized inland rivers in Chaohu, China, an integrated hydrodynamic and water quality model was used in this study. Sixteen diversion scenarios and five sewage interception scenarios were defined to assess the improvement of water quality parameters including ammonia nitrogen (NH3-N), total phosphorus (TP) and chemical oxygen demand (COD) under different diverted water flows, diverting times, diverting points, diverting routines and sewage interception proportions. An index of pollutant removal rate per unit diverted water flow (PRUWF) was proposed to evaluate the effect of the clean water diversion. Results show that operating conditions played important roles in water quality improvement of medium-sized inland rivers. The optimal clean water diversion was operated under the conditions of a flow rate of 5 m3/s for 48 h with an additional constructed bridge sluice. A global sensitivity analysis using the Latin Hypercube One-Factor-at-a-Time (LH-OAT) method was conducted to distinguish the contributions of various driving forces to inland river water restoration. Results show that sewage interception was more important than diverted water flow and diverting time with respect to water quality improvement, especially for COD. 相似文献
The hydrogeochemical processes and fuzzy GIS techniques were used to evaluate the groundwater quality in the Yeonjegu district of Busan Metropolitan City, Korea. The highest concentrations of major ions were mainly related to the local geology. The seawater intrusion into the river water and municipal contaminants were secondary contamination sources of groundwater in the study area. Factor analysis represented the contamination sources of the mineral dissolution of the host rocks and domestic influences. The Gibbs plot exhibited that the major ions were derived from the rock weathering condition. Piper’s trilinear diagram showed that the groundwater quality was classified into five types of CaHCO3, NaHCO3, NaCl, CaCl2, and CaSO4 types in that order. The ionic relationship and the saturation mineral index of the ions indicated that the evaporation, dissolution, and precipitation processes controlled the groundwater chemistry. The fuzzy GIS map showed that highly contaminated groundwater occurred in the northeastern and the central parts and that the groundwater of medium quality appeared in most parts of the study area. It suggested that the groundwater quality of the study area was influenced by local geology, seawater intrusion, and municipal contaminants. This research clearly demonstrated that the geochemical analyses and fuzzy GIS method were very useful to identify the contaminant sources and the location of good groundwater quality.
