Assessment of Calibration Parameters for an Aerial Gamma Spectrometry System using Monte-Carlo Technique

During a radiation emergency subsequent to a nuclear accident orweapon fallout, quick assessment of the ground contamination andthe resulting exposure is of prime importance in planning and execution of effective counter measures. For an online assessmentof ground contamination, it is essential to calibrate the detector system for several parameters viz. the source energy,source deployment matrix, the flight altitude and position abovethe contaminated surface. This article discusses the methodology to predict all the necessary parameters like photon fluence atvarious altitudes, the photo-peak counts in different energy windows, Air to Ground Correlation Factors (AGCF) and the doserate at any height due to air scattered gamma ray photons. Themethodology includes generation of theoretically simulated gammaspectra at a required detector position for a given source distribution on the ground using Monte-Carlo method provided by general purpose coupled neutron/photon transport code (MCNP CCC-200). Thus generated gamma spectra are analyzed to arrive at the required parameters mentioned above.     

Changes in Soil Properties of Abandoned Shrimp Ponds in Southern Thailand

Chemical soil properties between active shrimp ponds andabandoned ones on the Bangkok soil series were compared,at Ranote District, Songkhla Province in southern Thailand.Soil samples were collected at depth intervals of 0–10, 10–20, 20–30, 30–40 and 40–50 cm from pond bottoms at the same ponds used in a former study conducted in 1994, fora total of 6 ponds with 3 sampling sites for each pond. Theseponds were active during the previous study in 1994, abandonedin 1996 and investigated by this study in 1999. All the samples were analyzed for exchangeable Ca, Mg, K and Na electrical conductivity (EC), organic matter, S, P and pH, and statistically compared with the analytical results of theprevious study. An increase in amounts of Ca, Mg, K, Na and EC in the abandoned ponds as compared with the active ones by1.3–3.4, 1.4–2.1, 7.0–30.0, 1.2–6.3 and 1.3–10.9 timesrespectively was observed. That more of these elements weregained than lost each time the seawater was introduced intothe ponds, is explained by the Element Input/Output Consideration as proposed herein. Furthermore, a decreasein organic matter, S and P was also observed in the abandonedpond soils, and attributed to the absence of shrimp food and shrimp excreta following the cessation of shrimp raising activities. An unexpected decline in the soil pH of the abandoned ponds was found as well. Aerobic decomposition of organic matter during the absence of shrimp raising activitiescaused by soil microorganisms triggering SO₂ and H₂SO₄ formation probably played a more significantrole than the increase in the amounts of the basic elements (Ca, Mg, K, and Na) eventually reducing soil pH in the abandoned ponds. The significant depletion of the amounts of organic matter in the abandoned pond soils also supports this observation.     

Monitoring of Organochlorine Pesticide Residues in Summer and Winter Vegetables from Agra, India – A case study

Analysis of summer and winter vegetable samples during 2002–2003 for pesticidal contamination was carried out on Gas Chromatograph-Electron Capture Detector with capillary columns. The contamination levels of winter vegetables (average concentration of 4.57, 6.80 and 5.47 ppb respectively for Lindane, Endosulphan and DDT) were found to be slightly higher than the summer vegetables (average concentration of 4.47, 3.14 and 2.82 ppb respectively for Lindane, Endosulphan and DDT). The concentration of these organochlorine pesticides in summer and winter vegetables were well below the established tolerances but continuous consumption of such vegetables even with moderate contamination level can accumulate in the receptor's body and may lead to chronic effects that could be fatal.     

Assessing the bioremediation potential of arsenic tolerant bacterial strains in rice rhizosphere interface

The arsenic tolerant bacterial strains Staphylococcus arlettae(NBRIEAG-6), Staphylococcus sp.(NBRIEAG-8) and Brevibacillus sp.(NBRIEAG-9) were tested for their roles in enhancing plant growth and induction of stress-related enzymes in rice(Oryza sativa L. cv. NDR-359) plants at two different concentrations, 30 and 15 mg/kg of As(V) and As(III), respectively. An experiment was conducted to test the effect of these strains on plant growth promotion and arsenic uptake. We found 30%–40% reduction in total As uptake in bacteria-inoculated plants, with increased plant growth parameters compared to non-inoculated plants. Moreover, the bacteria-inoculated plants showed reduced activity of total glutathione(GSH) and glutathione reductase(GR) compared to their respective controls, which suggests the bacteria-mediated reduction of oxidative stress in plants. Thus, these strains were found to be beneficial in terms of the biochemical and physiological status of the plants under arsenic stress conditions.Furthermore, one-way ANOVA and principal component analysis(PCA) on enzymatic and non-enzymatic assays also revealed clear variations. The results support the distinction between control and treatments in both shoots and roots. Therefore, this study demonstrates the potential of rhizobacteria in alleviating arsenic stress in rice plants.     

福岛核泄漏事件对中国海污染的研究

2011年3月11日日本地震和海啸导致了日本福岛核电站核放射性物质泄漏事件.利用ROMS区域海洋模式对北太平洋环流进行模拟,并在此流场中加入核放射性污染物进行测试核放射性污染物是否能够输运到中国海域.在不考虑背景场浓度的情况下,福岛泄漏的核放射性物质在泄漏后4年能基本侵入整个中国海区,并且在10年内布满整个北太平洋区域,最大值区在北美的西岸外海.相较而言,将国际原子能的观测资料进行资料同化作为背景场使模拟更接近于观测事实.考虑了背景场的模拟显示,2019年进入东中国海的核放射性物质总量达到峰值.除此之外,还计算了各个海峡核放射性污染物通量及其随时间的变化,发现核放射性污染物主要通过吕宋海峡入侵南中国海;台湾海峡、台湾以东洋面为侵入东中国海的主要通道;核放射性污染物通过托克拉海峡、对马海峡流出东中国海.同时计算表明在未考虑径流的情况下,中国东部沿海地区的核放射性污染物浓度有着明显的季节特征,华南沿海冬春核污染物浓度高于夏秋两季,而华东沿海则相反.     

臭椿治理铜污染土壤的实验测定

臭椿（Ailanthus altissima）具有很强的抗逆性，能适应多种不良的环境，在中国广泛分布，是一个很有潜力的修复铜污染土壤的物种。通过种植实验检验臭椿修复铜污染土壤的能力。臭椿实生苗移植于4种不同铜的质量分数（0、29、57和86 mg·kg-1）、3种不同的施肥处理（对照、有机肥、无机肥）的土壤，经过5周种植，测量臭椿根、茎、叶的铜含量及各部分生物量。试验结果表明：1）土壤铜浓度的差异对臭椿生长没有显著影响；2）土壤施肥处理显著影响臭椿生长，施加无机肥生长最佳，对照次之，施有机肥最低；3）随土壤铜浓度增加，臭椿根、茎、叶的铜含量增加，然后趋缓，但似乎根、茎、叶的铜含量变化不同步；4）土壤肥力对臭椿茎、叶的铜含量没有显著影响，但对根的铜含量影响显著，施加无机肥的根中铜含量显著增加。臭椿经过短短5周处理，其体内铜的质量分数就到达120μg·g-1，且铜在各组织中的分布比为根：茎：叶＝2?1?2。相比一些超富集铜的草本植物，臭椿的铜吸收能力尚有距离，但其高生长、高抗逆性、深根系的特点，加之其对其他众多重金属元素的吸收能力使得这个物种在生物修复污染土壤方面的作用不容小觑。本研究丰富了治理土壤重金属污染的物种库，为进一步寻找重金属“超富集植物”，更有效的治理土壤污染提供一定的参考价值。     

Residue levels of organochlorine pesticides in cattle meat and organs slaughtered in selected towns in West Shoa Zone,Ethiopia

Residue levels of organochlorine pesticides (OCP) in a total of 90 cattle samples comprising meat, liver and kidney collected from carcasses slaughtered in six towns in West Shoa Zone, Ethiopia, (Ambo, Guder, Ginchi, Gedo, Holeta and Tikur Inchini), have been determined. The pesticides were extracted by solid phase extraction (SPE) and quantification was carried out using gas chromatography-mass spectrometry (GC-MS). A good linearity (r² > 0.998) was found in the range 0.001–7.00 mg/kg for the samples studied. Most of the pesticides had recoveries in the range 81–99% and values of relative standard deviation (RSD) <7.2% for repeatability and reproducibility, showing good accuracy and precision of the method. The concentration level of the studied organochlorines followed the order: p, p’ dichloro-diphenyl-trichloroethane (DDT) > endosulfan>o,p′-DDT >lindane>dieldrin>endrin>aldrin>chlorothanolin while the order of contamination in the analyzed organs was liver > kidney > meat. Heat treatment of the meat, kidney and liver samples (boiling for 90 min.) produced an overall reduction of 62.2%, 44.5%, 37.7%, 29%, 31%, 34.3% and 30.8% in lindane, o, p′-DDT, endosulfan, p, p′-DDT, chlorothanolin, aldrin, dieldrin, and endrin, respectively. Although the residual contents of the organochlorines detected in all the contaminated samples analyzed from the six cities were below the respective maximal permissible levels set by international organizations, samples from Holeta town were more contaminated and may necessitate effective monitoring as bioaccumulation of these residues may pose health problems in human beings.     

Examining Source-Receptor Relationships for Mercury in Scandinavia Modelled and Empirical Evidence

The atmosphere remains the major source of mercuryin Swedish ecosystems. Since the late eighties,atmospheric emissions of mercury have drasticallydecreased in Europe. Wet deposition of mercury hasdecreased over the last decade but still exhibitsa clear south-to-north gradient, greatlyinfluenced by source areas in northern and centralEurope. The decreases in emissions can beattributed to both direct measures to close knownpoint sources and a declining economy and energyconsumption in many East European countries.Further reductions of mercury emissions willrequire that other source categories such asindirect emissions from mercury-containingproducts and crematories are be considered.     

Heavy Metal Sediment Load from the City of Stockholm

A transect of upstream lake sitesand downstream coastal sites surrounding the cityof Stockholm, capital of Sweden, wereinvestigated for heavy metals in sediments.Concentrations of Cd, Cu, Hg, Pb and Zn increasedclose to the city. In the most central areas ofStockholm, sediment deposition was increasedabout 5-fold for Cd, Cu, Hg and Pb and 3-fold forZn, as compared to the surrounding areas. Thesediment load from the city was estimated bycorrecting for a background concentration. It canbe concluded that most of the load of Hg and Pbwas trapped in the sediments close to the citywhile Ni, Cu, Cd and Zn to a higher degree weretransported through the archipelago towards theBaltic Sea.     

新显色剂NPBPDT的合成及在环境监测中的应用研究

研究了1(4硝基苯基)3(5溴吡啶)三氮烯(NPBPDT)的合成及其与汞的显色反应。在TX100存在下,pH值为11.5的Na2B4O7NaOH缓冲溶液中,该试剂能与汞发生显色反应,汞与NPBPDT形成摩尔比为1∶2型的黄色配合物,在440nm处有一最大正吸收峰,在535nm处有一最大负吸收。以440nm为参比波长,535nm为测量波长进行双波长测定,表观摩尔吸光系数为2.80×105Lmol·cm,汞的浓度在0～12μg25mL范围内符合比尔定律。用拟定方法测定废水中的微量汞,有较高的准确度和精密度。