The radioactivity measurements in soils and fertilizers using gamma spectrometry technique

Because of their mineral content, soils are naturally radioactive and one of the sources of radioactivity other than those of natural origin is mainly due to the extensive use of fertilizers. The main aim of this paper is to evaluate the fluxes of natural radionuclides in local production of phosphate fertilizers to determine the content of radioactivity in several commercial fertilizers produced in Algeria and to estimate their radiological impact in a cultivated soil even for the long-term exposure due to their application.For these purposes, virgin and fertilized soils were collected from outlying Setif region in Algeria and from phosphate fertilizers used in this area.Gamma spectrometry was exploited to determine activity concentration due to naturally occurring ²²⁶Ra, ²³²Th and ⁴⁰K in five types of samples (two different sorts of fertilizers, virgin and fertilized soils and well water used for irrigation) taken from Setif’s areas.The results show that these radionuclides were present in an average concentration of 134.7 ± 24.1, 131.8 ± 16.7, 11644 ± 550 Bq/kg for the first fertilizer NPK and 190.3 ± 30, 117.2 ± 10.3, 5312 ± 249 Bq/kg for the second fertilizer (NPKs). For the virgin and the fertilized soils, the corresponding values were respectively 47.01 ± 7.3, 33 ± 7, 329.4 ± 19.7 Bq/kg and 53.2 ± 10.6, 50.0 ± 7, 311.4 ± 18.7 Bq/kg. For well water, the values were 1.93 and 0.12 Bq/kg; however the third value was below the Minimum Detectable Activity (MDA).The radium equivalent activity (Raeq) and the representative level index I_γr for all samples were also calculated. The data were discussed and compared with those given in the literature.     

不同磷处理对污染土壤中有效态铅及磷迁移的影响

为了研究不同含磷化合物对污染土壤中铅有效性的影响及其在土壤剖面中的迁移状况,对3种不同性质的含磷化合物按含量为2500、5000 mg·kg-1进行了土柱试验.结果表明,对铅污染土壤施入磷酸氢钙(SSP)、磷矿粉(PR)及羟基磷灰石(HA)能显著降低土壤表层CaCl2(0.01 mol·L-1)提取态铅的含量,且有效铅的含量随磷施入含量的增加而显著降低.在施磷270 d后,施入含量为5000 mg·kg-1的磷酸氢钙(SSP5)、磷矿粉(PR5)及羟基磷灰石(HA5)处理土壤有效铅的含量分别比对照降低了86.6%、81.1%和89.7%.对不同深度土壤有效磷和全磷含量分析表明,土壤中施入不同溶解性质的磷显著增加了土壤表层(0～10 cm)的有效磷(Olsen-p)及全磷的含量,土壤中有效磷及全磷的含量随着土柱深度的增加而显著降低.除了SSP5处理外,上述不同磷处理对于大于50 cm深度的土壤中的有效磷和全磷变化没有显著影响,而所有处理对于大于70 cm深度的土壤中有效磷和全磷含量没有显著影响.这表明在铅污染土壤中施入不同性质的磷能显著降低土壤中CaCl2(0.01 mol·L-1)提取态铅的含量,而土壤中施入的磷在土壤垂直剖面的迁移却很少,即使是易溶性的磷酸氢钙(SSP)也不会造成大于70cm深度的土壤剖面中磷含量的显著性差异,其原因可能与土壤胶体对磷的强力吸附有关.     

Physiological and biochemical responses of Microcystis aeruginosa to phosphite

Phosphorus (P) is a key biological element and limiting nutrient in aquatic environments. Phosphate (+5) is traditionally associated with the P nutrient supply. However, phosphite (+3) has recently generated a great deal of interest, because of the possibility that it is a P source based on recognition of its vital role in the original life of the early earth. This study investigated whether phosphite can be an alternative P source for Microcystis aeruginosa PCC 7806, one of the predominant bloom species in freshwater systems. The results indicated that M. aeruginosa could not utilize phosphite as a sole P-nutrient directly for cell growth at any concentration, but that phosphite could boost cell numbers and chlorophyll a (Chl-a) content as long as phosphate was provided simultaneously. Specifically, Chl-a production increased sharply when 5.44 mg P L⁻¹ phosphite was added to 0.54 mg P L⁻¹ phosphate medium. Analysis of the maximum yield of PSII indicated that phosphite may stimulate the photosynthesis process of cells in phosphate-phosphite medium. In addition, phosphite failed to support cell growth, even though it more readily permeated the cells in P-deficient medium than in P-sufficient medium. Alkaline phosphatase activity (APA) analysis indicated that, unlike organic P, phosphite inhibits the response of cells to deficient P status, especially under P-deprived conditions.     

Deterioration of water quality of Surma river

Surma River is polluted day by day by human activities, poor structured sewerage and drainage system, discharging industrial and household wastes. The charas (natural channels) are responsible for surface runoff conveyance from its urban catchments to the receiving Surma River. Water samples have been collected from a part of Surma River along different points and analyzed for various water quality parameters during dry and monsoon periods. Effects of industrial wastes, municipal sewage, and agricultural runoff on river water quality have been investigated. The study was conducted within the Chattak to Sunamganj portion of Surma River, which is significant due to the presence of two major industries – a paper mill and a cement factory. The other significant feature is the conveyors that travel from India to Chattak. The river was found to be highly turbid in the monsoon season. But BOD and fecal coliform concentration was found higher in the dry season. The water was found slightly acidic. The mean values of parameters were Conductivity 84–805 μs; DO: dry-5.52 mg/l, monsoon-5.72 mg/l; BOD: dry-1mg/l, monsoon-0.878 mg/l; Total Solid: dry-149.4 mg/l, monsoon-145.7 mg/l. In this study, an effort has been taken to investigate the status of concentration of phosphate (PO⁻⁴) and ammonia–nitrogen (NH₄–N) at four entrance points of Malnichara to the city, Guali chara, Gaviar khal and Bolramer khal. Data has been collected from March–April and September–October of 2004. Concentrations have been measured using UV Spectrophotometer. Although the phosphate concentration has been found within the limit set by DOE for fishing, irrigation and recreational purposes, however ammonia–nitrogen has been found to exceed the limit.     

流动注射氯化亚锡还原光度法测定水中总磷

建立了流动注射氯化亚锡还原光度法测定水中总磷的方法.改进了氯化亚锡的配制方法,优化了试验条件,方法检出限为0.02 mg/L,精密度与准确度均符合要求.应用该方法测定天然水样,分析速度加快,结果令人满意.     

Extraction of arsenic in a synthetic arsenic-contaminated soil using phosphate

An environment-friendly and cost-effective extraction method has been studied for the removal of arsenic from contaminated soil. A yellow-brown forest soil was contaminated with arsenic(V) and used as a model soil. Among various potassium and sodium salts, potassium phosphate was most effective in extracting arsenic, attaining more than 40% extraction in the pH range of 6–8 with minimum damage to the soil properties. Exchange mechanism is proposed for the extraction of arsenic from soil by phosphate. Sequential extraction shows that phosphate is effective in extracting arsenic of Al- and Fe-bound forms. Arsenic of residual form was not extracted. Arsenic was efficiently extracted by phosphate solution of pH 6.0 at 300 mM phosphate concentration and at 40°C.     

成都施用磷肥中镭（^226Ra）含量调查及对农田环境影响评价

本文报道了成都磷肥及其原料矿石中外照射剂量水平；用国家标准规定的方法测定了磷肥及其矿石中＾２２６Ｒａ含量；调查了同一生产厂家不同批号磷肥中＾２２６Ｒａ含量变化情况；估算出施用磷肥后可能带来的放射性环境污染，并对磷肥中＾２２６Ｒａ可能导致的农田环境影响作了简要评价? ?     

Revegetation of serpentine substrates: Response to phosphate application

Revegetation was studied on stockpiled serpentine substrate. The native vegetation surrounding the revegetation site is annual grassland. The seed mixture applied to both subsoil and topsoil plots was largely ineffective for revegetation. No growth occurred in the subsoil plots and most of the growth in the topsoil plots was from indigenous seed. Phosphate application (100 kg P ha^–1 as NaH₂PO₄ · H₂O) to the topsoil plots resulted in a significant increase in total above-ground productivity. Annual legumes (mostlyLotus subpinnatus Lag.) and, to a lesser degree,Plantago erecta Morris responded to the added phosphate with an increased above-ground productivity. Other annual forbs and annual grasses showed no significant response. The legumes also increased in abundance. Mycorrhizal root colonization forPlantago was not significantly affected by phosphate application, but was lower in this disturbed serpentine site compared to other undisturbed serpentine annual grassland sites nearby.     

Adsorption of sulfamethoxazole on functionalized carbon nanotubes as affected by cations and anions

The environmental risks of antibiotics have attracted lots of research attention, but their environmental behavior is not clear yet. Functionalized carbon nanotubes (CNTs) were used as model adsorbents and sulfamethoxazole (SMX) was used as a model antibiotic to investigate the effect of both cations (Ca²⁺, Cs⁺) and anions (phosphate) on antibiotics adsorption. Various mechanisms (such as electrostatic interaction, hydrophobic interaction, π-π and hydrogen bonds) play roles in SMX adsorption. Cations and anions could “wedge into” these mechanisms and thus alter SMX adsorption. This study emphasized that both increased and decreased SMX adsorption could be observed with the addition of cations/anions, depending on environmental conditions (such as pH in this current study). The net effect is the balance between the increased and decreased effects. The contribution of different mechanisms to the overall antibiotic adsorption on solid particles should be identified to accurately predict the apparent effect by cations and anions.     

The arbuscular mycorrhizal fungus Glomus mosseae can enhance arsenic tolerance in Medicago truncatula by increasing plant phosphorus status and restricting arsenate uptake

A pot experiment examined the biomass and As uptake of Medicago truncatula colonized by the arbuscular mycorrhizal (AM) fungus Glomus mosseae in low-P soil experimentally contaminated with different levels of arsenate. The biomass of G. mosseae external mycelium was unaffected by the highest addition level of As studied (200 mg kg⁻¹) but shoot and root biomass declined in both mycorrhizal and non-mycorrhizal plants, indicating that the AM fungus was more tolerant than M. truncatula to arsenate. Mycorrhizal inoculation increased shoot and root dry weights by enhancing host plant P nutrition and lowering shoot and root As concentrations compared with uninoculated plants. The AM fungus may have been highly tolerant to As and conferred enhanced tolerance to arsenate on the host plant by enhancing P nutrition and restricting root As uptake.