Residual tembotrione and atrazine in carrot

Carrot (Daucus carota L.) is a vegetable crop that is grown throughout the year across various regions of Brazil in rotation or in succession to other cultures. Herbicide residual effect has emerged as a concern, because of the possibility of carryover. Thus, the objective of this study was to evaluate the effect of tembotrione and atrazine residues – in mixture and isolated – on carrot planted in succession to corn. The experiment was designed in randomized blocks with five replications. Treatments consisted of tembotrione (50.4 g ha^?1), tembotrione (100.8 g ha^?1), tembotrione + atrazine (50.4 g ha^?1+ 2 L ha^?1), tembotrione + atrazine (100.8 g ha^?1+ 2 L ha^?1), and atrazine (2.00 L ha^?1) applied eight months before carrot seeding, plus a control treatment with no herbicide application. Investigated variables were shoot dry mass, productivity, and classification of carrot roots. The presence of atrazine and tembotrione decreased dry mass in the area, and only tembotrione reduced total root productivity. Thus, there is a carryover effect to tembotrione application that reduces the dry matter accumulation of shoot and total productivity, and an atrazine + tembotrione (100.8 g ha^?1) mixture reduces the total productivity after application of these herbicides to soil.     

不同质量浓度黄莒蒲和狭叶香蒲对铜绿微囊藻的化感作用

分别采用黄菖蒲（IrispseudacorusL．）、狭叶香蒲（TyphaangustifoliaL．）和铜绿微囊藻（Microcystisaeruginosa）共生培养的实验方法研究了不同质量浓度黄菖蒲、狭叶香蒲对铜绿微囊藻的化感作用。结果表明,黄菖蒲在质量浓度大于10g／L时对初始密度为1．0×10^7ind／mL的铜绿微囊藻具有较好的抑制作用,表现为黄菖蒲质量浓度为10、20和40g／L时,第15天对铜绿微囊藻的抑制率分别为30．1％、51．8％和84．0％;狭叶香蒲在质量浓度大于20g／L时对铜绿微囊藻有明显的抑制作用,表现为狭叶香蒲质量浓度为20g／L和40g／L时,第15天对铜绿微囊藻的抑制率分别为34．2％和77．7％,实验过程中,铜绿微囊藻叶绿素a含量逐渐减少,而藻密度、SOD活性及MDA含量先增加后逐渐降低,表明经过一段时间持续地化感胁迫,黄菖蒲和狭叶香蒲可以诱导铜绿微囊藻产生氧化胁迫,导致细胞结构严重损伤和叶绿素大量分解,从而强烈抑制铜绿微囊藻的生长。     

The response of Chenopodium album L. and Abutilon theophrasti Medik. to reduced doses of mesotrione

Limited toxicity data are available for estuarine and marine species and the widely used pyrethroid insecticide, permethrin. This study determined acute effects of permethrin on survival, lipid peroxidation, acetylcholinesterase activity, and splenocyte proliferation for two fish species found in South Carolina estuaries; juvenile red drum (Sciaenops ocellatus) and adult mummichog (Fundulus heteroclitus). Juvenile S. ocellatus were significantly more sensitive than adult F. heteroclitus to permethrin exposure, with a 96-h LC50 value of 8 μg/L determined for red drum compared to 23 μg/L for mummichog. Lipid peroxidation activity of the liver increased in permethrin-treated fish compared to control animals after 24 h and decreased after 96 h. Permethrin had no effect on acetylcholinesterase activity of the brain at the concentrations tested. Permethrin exposure significantly inhibited splenocyte proliferation, indicating an immunosuppressive effect. Most of the effects of permethrin on fish cellular stress enzymes and survival occurred at concentrations much higher than those typically measured in the environment. However, inhibition of splenocyte proliferation in juvenile red drum occurred at approximately twice that of measured permethrin concentrations in surface water. These findings may prove useful to the future management and regulation of pyrethroid insecticide use near estuarine habitats.     

Dissipation of pendimethalin in the soil of field pea (Pisum sativum L.) and detection of terminal residues in plants

Dissipation of pendimethalin in the soil of field peas (Pisum sativum L.) at 0 to 110 days, and terminal residues in green and mature pea were studied under field conditions. Pendimethalin was applied as pre-emergence herbicide at 750, to 185 g a.i. ha^?1 in winter, in field peas. Dissipation of pendimethalin in the soil at 0 to 110 days followed first-order kinetics showing a half-life of 19.83 days averaged over all doses. Low pendimethalin residues were found in mature pea grain (0.004, 0.003, <0.001 μg g^?1), and straw (0.007, 0.002, <0.001 μg g^?1) at 750, 350 and 185 g a.i. ha^?1 treatments, respectively. The study indicated that residues of pendimethalin in green and mature pea were within the prescribed MRL limits.     

A fluorometric method to determine rainfastness,volatilization and photostability of glyphosate from glass slides,after application of vision® with two adjuvants

Abstract

A fluorometric method was developed to quantify glyphosate loss from glass surfaces after exposure to the natural forest environment. The method was based on the principle of converting glyphosate into glycine, followed by the fluorogenic labeling with o‐phthalaldehyde. A fluorometer (with λ _Ex = 360 nm / λ_Em =430 nm) was used to quantify the derivatized fluorogenic compound. Response was linear over the concentration range of 143, 286, 572, 858 and 1144 μg of glyphosate (acid equivalent, AE) per mL of the diluted Vision® formulation. Three end‐use mixtures of Vision® were prepared, each at a concentration of 28.6 g AE/L, without and with two adjuvants, Ethomeen® T/25 at 4.5 mL/L and Silwet^® L‐77 at 1.5 mL/L. Several dilutions of the end‐use mixtures were applied on glass slides without and with the coating of cuticular wax extracted from trembling aspen foliage. The slides were left for 5 days in a forest opening to determine rainfastness, volatilization and photostability of glyphosate. The residues were quantified using the method developed. Three calibration curves were required because Silwet decreased the fluorometric response of glyphosate, whereas Ethomeen increased it. The minimum detection limit was 143 μg of glyphosate/mL. Glyphosate was resistant to volatilization and sunlight‐mediated degradation, regardless of the presence of wax coating or the adjuvants. About 64% of the applied glyphosate was washed off after a 9.6 mm rainfall when no adjuvant was present. Both adjuvants provided some amount of rain‐protection to glyphosate, but Silwet reduced the washoff to a greater extent (46%) than Ethomeen (55%).     

Cadmium accumulation in and tolerance of rice (Oryza sativa L.) varieties with different rates of radial oxygen loss

Cadmium (Cd) uptake and tolerance were investigated among 20 rice cultivars based on a field experiment (1.2 mg Cd kg⁻¹ in soil) and a soil pot trial (control, 100 mg Cd kg⁻¹), and rates of radial oxygen loss (ROL) were measured under a deoxygenated solution. Significant differences were found among the cultivars in: (1) brown rice Cd concentrations (0.11-0.29 mg kg⁻¹) in a field soil, (2) grain Cd tolerance (34-113%) and concentrations (2.1-6.5 mg kg⁻¹) in a pot trial, and (3) rates of ROL (15-31 mmol O₂ kg⁻¹ root d.w. h⁻¹). Target hazard quotients were calculated for the field experiment to assess potential Cd risk. Significant negative relationships were found between rates of ROL and concentrations of Cd in brown rice or straw under field and greenhouse conditions, indicating that rice cultivars with higher rates of ROL had higher capacities for limiting the transfer of Cd to rice and straw.     

苜蓿对多环芳烃菲污染土壤的修复作用研究

采用盆栽试验方法,研究了苜蓿(Medicago sativa L.)对多环芳烃菲污染土壤的修复作用.结果表明,多环芳烃菲对苜蓿的生长具有抑制作用,土壤中菲初始浓度越高抑制作用越明显.445.22 mg/kg条件下苜蓿茎叶和根的生物量最小,仅为无污染对照土壤的57.31%和31.20%.经过60 d的修复试验,苜蓿能够明显促进土壤中菲的降解.根际和非根际土壤中菲的去除率分别为85.68%～91.40%和75.25%～86.61%.同处理中根际土壤中菲残留浓度低于非根际土壤,而脱氢酶活性高于非根际土壤.无论是在非根际还是根际土壤中随着菲初始浓度增大,菲降解率和脱氢酶活性降低.脱氢酶活性与降解率的关系表明,脱氢酶活性与菲降解率显著正相关.所以植物根系的存在能够有效促进土壤中多环芳烃菲的降解.     

Mineral economics: Overview of a discipline

Mineral economics is the academic discipline that investigates and promotes understanding of economic and policy issues associated with the production and use of mineral commodities. While its origins can be traced back at least 200 years to the writings of David Ricardo and other early Classical economists, it emerged as a separate academic field only after World War II and then primarily in the United States. As a separate academic discipline, its roots are found in mining schools that needed to consider the milieu in which minerals are sold. While geologists, mining engineers, and others with technical backgrounds were largely responsible for creating the first stand-alone mineral-economics programs, ultimately trained economists became participants as well. Moreover, even after the rise of mineral-economics departments, most of the research in the field continued and continues to be carried out in other academic units, including traditional economic departments and engineering schools, as well as in government agencies, nonprofit research organizations, consulting firms, and international organizations.     

The supply behaviour of state mining enterprises: A case study of the Jordanian phosphate industry

An important feature of export-oriented production in mineral-rich developing countries for almost three decades after 1960 was the growth of state-owned enterprises. For the phosphate industry, this was reflected in the expansion of companies such as Office Cherifienne des Phosphate (OCP) in Morocco and the Jordan Phosphate Mines Company (JPMC). There was a strategic importance of the industry for these nations and the large capital outlays necessary for phosphate and fertilizer production expansion often required considerable government assistance because of the perceived high risks of private investment in the industry.     

重庆三峡库区重楼属药用植物资源调查

经调查鉴定,重庆三峡库区有重楼属药用植物6种9变种,其中以巫溪分布的种类最多,华重楼、七叶一枝花分布最广。重点介绍了它们的地理分布、资源状况及其开发前景,为更好地开发利用三峡库区重楼属药用植物资源提供科学依据。