Nowadays, asphalt mixtures can be complex and have many ingredients to meet economic, performance, and/or environmental requirements. Economic and environmental factors have been driving performance in the positive direction for rutting, but the negative direction for brittleness, cracking, and overall durability. Recent research has also shown that two of the national standards to assess aging or effects of environmental factors (AASHTO T283 and R30) do not always simulate the amount of aging or behaviors mentioned in the documents. Also, these methods generally view one environmental effect at a time, and do not consider simultaneous environmental effects on aging (e.g. oxidation, moisture, freeze-thaw effects). However, pavements are exposed to combined environmental effects. As such, there is a lack of understanding of the combined environmental effects on asphalt pavement, and improve methods are needed for laboratory settings, resulting in less than optimal design and materials selection protocols. This dissertation focuses on investigating combined environmental effects of oxidation, moisture, and freeze-thaw. The dissertation includes four years of field aging of plant mixed asphalt mixtures containing no recycled materials and three different warm mix technologies that were also exposed to eight laboratory conditioning protocols including individual and combined environmental effects of oxidation, moisture and freeze-thaw to investigate mixture properties measured at high, intermediate, and low temperatures with several mixture tests that were complimented with tests on recovered binder. Major findings are summarized below: • Cantabro mass loss captured individual and combined effects damage in laboratory and field conditions better than other mixture testing utilized herein and was recommended for mixture assessment. • Laboratory conditioning protocols with combined effects were the only ones able to consistently represent four or more years of field aging in the Mississippi climate. • Field aging of laboratory compacted specimens in PVC sleeves did not fully represent field aging of field placed pavement. Temperature and moisture conditions varied between the two cases. • Use of Cantabro mass loss and laboratory conditioning consisting of hot air, hot water, and freeze-thaw conditions was shown to provide combined effects improvements relative to at least some typical practices. Guidance was provided on how to use these tools to assess combined effects.

No presente trabalho, avaliou-se os efeitos individuais e combinados de nove enzimas comerciais sobre as propriedades reológicas de massa das farinhas de trigo, com o objetivo de identificar seus efeitos sinérgicos ou antagônicos e as suas concentrações ótimas, como alternativa para substituição de oxidantes químicos no tratamento de farinhas. α-Amilases de origem fúngica (AMY-F), bacteriana (AMY-B) e maltogênica (AMY-M), xilanases fúngica (XYL-F) e bacteriana (XYL-B), glucose oxidase (GOX), lacase (LAC), lipase (LIP) e transglutaminase (TG) foram testadas em dois tipos de farinha: uma farinha forte padrão (farinha A) e uma farinha fraca comum (farinha B). Inicialmente, as enzimas foram adicionadas individualmente na farinha onde, seus efeitos sobre Falling Number (FN), farinografia e alveografia, foram avaliados variando-se suas concentrações de 25 - 833 U.kg-1, a fim de se identificar as faixas de concentração ideais de cada uma delas. Identificou-se que as α-amilases afetaram principalmente as propriedades farinográficas, reduzindo a capacidade de absorção de água (WA) e tempo de estabilidade (ST) das massas. Para o ajuste de FN, AMY-B (150 U.kg-1) foi mais eficiente que AMY-F (583 U.kg-1) e AMY-M (583 U.kg-1). As xilanases melhoraram o valor de W (10-4 J) e razão P/L, sendo que em todos os testes XYL-B foi mais eficiente do que XYL-F. Na concentração de 25 U.kg-1, GOX e LAC melhoraram o ST, razão P/L e valor de W; no entanto, aumentaram o tempo de desenvolvimento (DT) das massas. LIP (150 U.kg-1) promoveu a melhora no W e DT, enquanto que TG não apresentou efeitos significativos na maioria dos parâmetros avaliados. A partir disso, os efeitos combinados das enzimas foram avaliados através de dois planejamentos experimentais sequenciais. Para farinha A, a combinação enzimática ótima foi AMY-B (166 U.kg-1), AMY-M (133 U.kg-1), XYL-B (150 U.kg-1), GOX (8 U. kg-1) e LIP (150 U.kg-1). Identificou-se um efeito sinérgico entre XYL-B e GOX na melhoria do W e razão P/L. Para a farinha B, a combinação enzimática ótima foi AMY-B (150 U.kg-1), LIP (150 U.kg-1), GOX (100 U.kg-1) e LAC (200 U.kg-1), sendo que GOX e LAC apresentaram um efeito cooperativo, quando usadas em concentrações opostas. As combinações enzimáticas foram mais eficientes do que a azodicarbonamida, cujo efeito, mesmo na concentração máxima (40 ppm) permitida pela legislação, não melhorou os parâmetros reológicos das massas. Foi demonstrado que é possível a substituição de oxidantes químicos por enzimas para o tratamento de farinhas, a fim de melhorar a reologia das massas, mesmo para uma farinha fraca, tornando-a adequada para panificação. / In the present work, it was evaluated the individual and combined effects of nine commercial enzymes on the rheological properties of dough wheat flour, aiming to identify synergistic and antagonist effects between the enzymes and their optimal concentrations as substitutes of chemical oxidants. Fungal (AMY-F), bacterial (AMY-B) and maltogenic (AMY-M) -amylases, fungal (XYL-F) and bacterial (XYL-B) xylanases, glucose oxidase (GOX), laccase (LAC), lipase (LIP) and transglutaminase (TG) were tested in two types of flour: standard strong flour (flour A) and common weak flour (flour B). Initially, Falling Number, farinography and alveography analysis were carried out varying the enzymes concentrations from 25 to 833 U.kg-1, to identify the ideal ranges of each of them to improve the rheological characteristics of dough wheat flour. It was identified that α-amylases affected mainly the farinographic properties, reducing the water absorption (WA) and stability time (ST). AMY-B was the most effective enzyme for setting the FN, requiring 150 U.kg-1, while for AMY-F and AMY-M it was necessary 583 U.kg-1. In all tests, XYL-B was more efficient than XYL-F, but both improved the W (10-4 J) value and P/L ratio. At 25 U.kg-1, GOX and LAC had important improves on the ST, P/L ratio and W value, however increased undesirably the development time (DT). LIP (150 U.kg 1) promoted the improvement in W value and DT, while TG had not significant effects on most of the evaluated parameters. After that, the combined effects of enzymes were evaluated through two sequential experimental designs. For flour A, the optimal combination of enzymes was AMY-B (166 U.kg-1), AMY-M (133 U.kg-1), XYL-B (150 U.kg-1), GOX (8 U.kg-1) and LIP (150 U.kg-1). It was identified a synergistic effect between XYL-B and GOX to improvement of W value (10-4 J) and the P/L ratio. For the flour B, the optimal combination of enzymes was AMY-B (150 U.kg-1), LIP (150 U.kg-1), GOX (100 U.kg-1) and LAC (200 U.kg-1). GOX and LAC presented a cooperative effect, when they were used at opposite concentrations. The enzymes mixtures were compared with chemical oxidant azodicarbonamide, and, even at the maximum concentration (40 ppm) allowed by Brazilian Health Surveillance Agency, the enzyme mixture was more effective. It was demonstrated that it is possible to perform the complete substitution of chemical oxidants by enzymes in order to adequate and improve the rheological parameters of dough wheat flours, even for a weak flour, making it suitable for bakery.

No description available.

No presente trabalho, avaliou-se os efeitos individuais e combinados de nove enzimas comerciais sobre as propriedades reológicas de massa das farinhas de trigo, com o objetivo de identificar seus efeitos sinérgicos ou antagônicos e as suas concentrações ótimas, como alternativa para substituição de oxidantes químicos no tratamento de farinhas. α-Amilases de origem fúngica (AMY-F), bacteriana (AMY-B) e maltogênica (AMY-M), xilanases fúngica (XYL-F) e bacteriana (XYL-B), glucose oxidase (GOX), lacase (LAC), lipase (LIP) e transglutaminase (TG) foram testadas em dois tipos de farinha: uma farinha forte padrão (farinha A) e uma farinha fraca comum (farinha B). Inicialmente, as enzimas foram adicionadas individualmente na farinha onde, seus efeitos sobre Falling Number (FN), farinografia e alveografia, foram avaliados variando-se suas concentrações de 25 - 833 U.kg-1, a fim de se identificar as faixas de concentração ideais de cada uma delas. Identificou-se que as α-amilases afetaram principalmente as propriedades farinográficas, reduzindo a capacidade de absorção de água (WA) e tempo de estabilidade (ST) das massas. Para o ajuste de FN, AMY-B (150 U.kg-1) foi mais eficiente que AMY-F (583 U.kg-1) e AMY-M (583 U.kg-1). As xilanases melhoraram o valor de W (10-4 J) e razão P/L, sendo que em todos os testes XYL-B foi mais eficiente do que XYL-F. Na concentração de 25 U.kg-1, GOX e LAC melhoraram o ST, razão P/L e valor de W; no entanto, aumentaram o tempo de desenvolvimento (DT) das massas. LIP (150 U.kg-1) promoveu a melhora no W e DT, enquanto que TG não apresentou efeitos significativos na maioria dos parâmetros avaliados. A partir disso, os efeitos combinados das enzimas foram avaliados através de dois planejamentos experimentais sequenciais. Para farinha A, a combinação enzimática ótima foi AMY-B (166 U.kg-1), AMY-M (133 U.kg-1), XYL-B (150 U.kg-1), GOX (8 U. kg-1) e LIP (150 U.kg-1). Identificou-se um efeito sinérgico entre XYL-B e GOX na melhoria do W e razão P/L. Para a farinha B, a combinação enzimática ótima foi AMY-B (150 U.kg-1), LIP (150 U.kg-1), GOX (100 U.kg-1) e LAC (200 U.kg-1), sendo que GOX e LAC apresentaram um efeito cooperativo, quando usadas em concentrações opostas. As combinações enzimáticas foram mais eficientes do que a azodicarbonamida, cujo efeito, mesmo na concentração máxima (40 ppm) permitida pela legislação, não melhorou os parâmetros reológicos das massas. Foi demonstrado que é possível a substituição de oxidantes químicos por enzimas para o tratamento de farinhas, a fim de melhorar a reologia das massas, mesmo para uma farinha fraca, tornando-a adequada para panificação. / In the present work, it was evaluated the individual and combined effects of nine commercial enzymes on the rheological properties of dough wheat flour, aiming to identify synergistic and antagonist effects between the enzymes and their optimal concentrations as substitutes of chemical oxidants. Fungal (AMY-F), bacterial (AMY-B) and maltogenic (AMY-M) -amylases, fungal (XYL-F) and bacterial (XYL-B) xylanases, glucose oxidase (GOX), laccase (LAC), lipase (LIP) and transglutaminase (TG) were tested in two types of flour: standard strong flour (flour A) and common weak flour (flour B). Initially, Falling Number, farinography and alveography analysis were carried out varying the enzymes concentrations from 25 to 833 U.kg-1, to identify the ideal ranges of each of them to improve the rheological characteristics of dough wheat flour. It was identified that α-amylases affected mainly the farinographic properties, reducing the water absorption (WA) and stability time (ST). AMY-B was the most effective enzyme for setting the FN, requiring 150 U.kg-1, while for AMY-F and AMY-M it was necessary 583 U.kg-1. In all tests, XYL-B was more efficient than XYL-F, but both improved the W (10-4 J) value and P/L ratio. At 25 U.kg-1, GOX and LAC had important improves on the ST, P/L ratio and W value, however increased undesirably the development time (DT). LIP (150 U.kg 1) promoted the improvement in W value and DT, while TG had not significant effects on most of the evaluated parameters. After that, the combined effects of enzymes were evaluated through two sequential experimental designs. For flour A, the optimal combination of enzymes was AMY-B (166 U.kg-1), AMY-M (133 U.kg-1), XYL-B (150 U.kg-1), GOX (8 U.kg-1) and LIP (150 U.kg-1). It was identified a synergistic effect between XYL-B and GOX to improvement of W value (10-4 J) and the P/L ratio. For the flour B, the optimal combination of enzymes was AMY-B (150 U.kg-1), LIP (150 U.kg-1), GOX (100 U.kg-1) and LAC (200 U.kg-1). GOX and LAC presented a cooperative effect, when they were used at opposite concentrations. The enzymes mixtures were compared with chemical oxidant azodicarbonamide, and, even at the maximum concentration (40 ppm) allowed by Brazilian Health Surveillance Agency, the enzyme mixture was more effective. It was demonstrated that it is possible to perform the complete substitution of chemical oxidants by enzymes in order to adequate and improve the rheological parameters of dough wheat flours, even for a weak flour, making it suitable for bakery.

No presente trabalho, avaliou-se os efeitos individuais e combinados de nove enzimas comerciais sobre as propriedades reológicas de massa das farinhas de trigo, com o objetivo de identificar seus efeitos sinérgicos ou antagônicos e as suas concentrações ótimas, como alternativa para substituição de oxidantes químicos no tratamento de farinhas. α-Amilases de origem fúngica (AMY-F), bacteriana (AMY-B) e maltogênica (AMY-M), xilanases fúngica (XYL-F) e bacteriana (XYL-B), glucose oxidase (GOX), lacase (LAC), lipase (LIP) e transglutaminase (TG) foram testadas em dois tipos de farinha: uma farinha forte padrão (farinha A) e uma farinha fraca comum (farinha B). Inicialmente, as enzimas foram adicionadas individualmente na farinha onde, seus efeitos sobre Falling Number (FN), farinografia e alveografia, foram avaliados variando-se suas concentrações de 25 - 833 U.kg-1, a fim de se identificar as faixas de concentração ideais de cada uma delas. Identificou-se que as α-amilases afetaram principalmente as propriedades farinográficas, reduzindo a capacidade de absorção de água (WA) e tempo de estabilidade (ST) das massas. Para o ajuste de FN, AMY-B (150 U.kg-1) foi mais eficiente que AMY-F (583 U.kg-1) e AMY-M (583 U.kg-1). As xilanases melhoraram o valor de W (10-4 J) e razão P/L, sendo que em todos os testes XYL-B foi mais eficiente do que XYL-F. Na concentração de 25 U.kg-1, GOX e LAC melhoraram o ST, razão P/L e valor de W; no entanto, aumentaram o tempo de desenvolvimento (DT) das massas. LIP (150 U.kg-1) promoveu a melhora no W e DT, enquanto que TG não apresentou efeitos significativos na maioria dos parâmetros avaliados. A partir disso, os efeitos combinados das enzimas foram avaliados através de dois planejamentos experimentais sequenciais. Para farinha A, a combinação enzimática ótima foi AMY-B (166 U.kg-1), AMY-M (133 U.kg-1), XYL-B (150 U.kg-1), GOX (8 U. kg-1) e LIP (150 U.kg-1). Identificou-se um efeito sinérgico entre XYL-B e GOX na melhoria do W e razão P/L. Para a farinha B, a combinação enzimática ótima foi AMY-B (150 U.kg-1), LIP (150 U.kg-1), GOX (100 U.kg-1) e LAC (200 U.kg-1), sendo que GOX e LAC apresentaram um efeito cooperativo, quando usadas em concentrações opostas. As combinações enzimáticas foram mais eficientes do que a azodicarbonamida, cujo efeito, mesmo na concentração máxima (40 ppm) permitida pela legislação, não melhorou os parâmetros reológicos das massas. Foi demonstrado que é possível a substituição de oxidantes químicos por enzimas para o tratamento de farinhas, a fim de melhorar a reologia das massas, mesmo para uma farinha fraca, tornando-a adequada para panificação. / In the present work, it was evaluated the individual and combined effects of nine commercial enzymes on the rheological properties of dough wheat flour, aiming to identify synergistic and antagonist effects between the enzymes and their optimal concentrations as substitutes of chemical oxidants. Fungal (AMY-F), bacterial (AMY-B) and maltogenic (AMY-M) -amylases, fungal (XYL-F) and bacterial (XYL-B) xylanases, glucose oxidase (GOX), laccase (LAC), lipase (LIP) and transglutaminase (TG) were tested in two types of flour: standard strong flour (flour A) and common weak flour (flour B). Initially, Falling Number, farinography and alveography analysis were carried out varying the enzymes concentrations from 25 to 833 U.kg-1, to identify the ideal ranges of each of them to improve the rheological characteristics of dough wheat flour. It was identified that α-amylases affected mainly the farinographic properties, reducing the water absorption (WA) and stability time (ST). AMY-B was the most effective enzyme for setting the FN, requiring 150 U.kg-1, while for AMY-F and AMY-M it was necessary 583 U.kg-1. In all tests, XYL-B was more efficient than XYL-F, but both improved the W (10-4 J) value and P/L ratio. At 25 U.kg-1, GOX and LAC had important improves on the ST, P/L ratio and W value, however increased undesirably the development time (DT). LIP (150 U.kg 1) promoted the improvement in W value and DT, while TG had not significant effects on most of the evaluated parameters. After that, the combined effects of enzymes were evaluated through two sequential experimental designs. For flour A, the optimal combination of enzymes was AMY-B (166 U.kg-1), AMY-M (133 U.kg-1), XYL-B (150 U.kg-1), GOX (8 U.kg-1) and LIP (150 U.kg-1). It was identified a synergistic effect between XYL-B and GOX to improvement of W value (10-4 J) and the P/L ratio. For the flour B, the optimal combination of enzymes was AMY-B (150 U.kg-1), LIP (150 U.kg-1), GOX (100 U.kg-1) and LAC (200 U.kg-1). GOX and LAC presented a cooperative effect, when they were used at opposite concentrations. The enzymes mixtures were compared with chemical oxidant azodicarbonamide, and, even at the maximum concentration (40 ppm) allowed by Brazilian Health Surveillance Agency, the enzyme mixture was more effective. It was demonstrated that it is possible to perform the complete substitution of chemical oxidants by enzymes in order to adequate and improve the rheological parameters of dough wheat flours, even for a weak flour, making it suitable for bakery.

For decades, humans have impacted marine ecosystems in a variety of ways including contamination by pollution, fishing, and physical destruction of habitats. Global change has, and will, lead to alterations in in a number of abiotic factors of our ocean in particular reduced oxygen saturation, salinity changes, elevated temperature (ocean warming or OW) and elevated carbon dioxide (ocean acidification or OA). Now and in the future, OA and OW will operate together with local anthropogenic drivers such as oil pollution. And yet, at present, very little is known about their potential combined interactive effects on physiological performance and tolerance of marine organisms. Therefore, multiple driver experiments are required if we are to understand and predict future vulnerability of species, populations and ecosystems. Early life stages of invertebrates are generally considered most vulnerable to environmental stress. However, few studies consider the combined effects OA and OW on survival and growth during early development of marine invertebrates, and to our knowledge, there is no information on the additional effects of oil pollution. Therefore, the aim of this thesis was to investigate the effects of combined exposure to OA, OW, and incorporating local drivers such as oil pollution on the development, morphology and physiology of three economically and ecologically important marine invertebrates. These are Northern shrimp Pandalus borealis, Northern krill Meganyctiphanes norvegica, and the green sea urchin Strongylocentrotus droebachiensis. All are cold-water species, assumed to have a narrower tolerance than more temperate species, and so could be particular sensitive to combined stressor affects. Both Northern krill and to a lesser extent Northern shrimp larvae survived experimental conditions, mirroring those predicted under a future global change scenario (combined OA and OW exposure). Neither was hatching success affected. Both shrimp and krill larvae exhibited accelerated developmental rates and incurred greater maintenance costs as a result of exposure to these stressors. Shrimp larvae showed accelerated developmental rates (-9 days), increased metabolic rates (+20 %), and increased feeding rates (+20 %), but reduced growth (- 9 %) when exposed to OW compared with the control. OA increased development rate but only at the control temperature. Although juvenile mortality of krill was not affected by predicted OA/OW conditions, metabolic rate increased significantly (+ 36 %), as did larval developmental rate, while number of moults, feeding rate and growth (- 67 %) decreased significantly (- 67 %, - 60 % and -8 % respectively). Accelerated development was accompanied by greater maintenance costs possibly due to experience a mismatch between energy supply and demand. Both species had an excess of food, and so growth reduction was more likely to be associated with higher metabolic demands in the future global change treatments. Food shortage in situ, due to variable food availability in the sea and/or mismatch with key prey species (algae and zooplankton) could result in more negative effects on growth and ultimately survival. Green sea urchins were also able to survive OA exposure, without detectable effects on hatching success. However, at day 44 post-fertilization, larval body length in the OA treatment was 9 % lower compared to the control. Furthermore, there was a significant tendency of urchin larvae to increase swimming activity in the OA conditions that might indicate compensatory feeding. Elevated maintenance and repair costs as a result of exposure to multi-stressors affected the energy budget of all the three species studied here resulting in reduced growth. Global drivers (OA and OW) resulted in trade-offs with more energy reallocated to swimming activity and metabolism, rather than growth. Exposure to oil reduced the acquisition of energy by reduced feeding which in turn resulted in less energy being available for growth. Both shrimp and sea urchin larvae showed reduced activity and feeding when exposed to oil. It is possible that the reduced swimming activity observed may be due to a narcotic effect of the oil. Furthermore, early stage sea urchin larvae showed increased mortality when exposed to oil while the older larvae did not, indicating a stage specific toxicity to oil for sea urchin larvae. The combination of global drivers and oil pollution acted additively on growth for both sea urchin and shrimp larvae. The impact of combined drivers on the size of shrimp larvae was equal the sum of the negative impacts observed for each driver: a 5 % reduction when exposed to OA and OW, a 9 % reduction when exposed to oil, and a cumulative 15 % reduction when exposed to all stressors. Similarly, the impact of combined drivers on the size of sea urchin larvae was equal to the sum of the negative impacts observed for each driver: a 14 % reduction when exposed to OA, a 9 % reduction when exposed to oil, and a 21 % reduction when exposed to all drivers. Therefore, the study demonstrated the additive physiological effects of OA, OW and a contaminant, and indicated that larval (sea urchin and shrimp) resilience to future changes (i.e. pollution) could be greatly reduced if larvae were already energy limited and severely stressed (reduced development) as a result of exposure to the global drivers. This study therefore shows the importance that the effective management of local drivers such as oil pollution could have against the backdrop of OA and OW, and emphasises that it is important to study impacts of toxicants, such as an oil pollution, in the context of predicted changes in the environment, as OW and OA are becoming major concerns. Finally, the fact that some local and global drivers seem to act additively should encourage local managers to act on local driver regulations, to obtain positive effects on local populations and environment and thereby rendering them more resilient to the negative impacts of future global drivers.

The trace metals and pesticides are commonly found in surface water receiving industrial and agricultural effluents. However, the potential negative effects of these compounds on aquatic ecosystems have not been deeply studied. Hence, the aim of this study is to assess the single and combined effects of aluminum (Al) and atrazine on the development and growth rate of duckweed, Lemna minor L. The single exposures were implemented with either Al or atrazine at the concentration of 5, 50 and 500 μg L-1 and a binary exposure was conducted with 50 μg L-1 of Al and 5 μg L-1 of atrazine for two weeks. The results revealed that both Al and atrazine at the concentration of 500 μg L-1 strongly inhibited the development and growth rate of the duckweed. On the contrary, the mixture of Al and atrazine showed antagonistic effects on the plant. To our knowledge, this is the first report on the combined effects of these two contaminants on the duckweed. Therefore, our results could be useful for environmental managers in setting up and adjusting the safe guideline values in Vietnam for Al and atrazine in natural waters in term of ecological health protection. / Kim loại nặng và thuốc trừ sâu thường được tìm thấy trong các nguồn nước mặt, nơi tiếp nhận nước thải công nghiệp và nông nghiệp. Tuy nhiên, những ảnh hưởng tiềm tàng mang tính tiêu cực của những hợp chất này đối với hệ sinh thái thủy vực chưa được nghiên cứu đầy đủ. Do đó, mục tiêu của nghiên cứu này nhằm đánh giá những ảnh hưởng riêng lẻ và kết hợp của nhôm (Al) và atrazine lên sự phát triển và tốc độ sinh trưởng của bèo tấm, Lemma minor L. Sự phơi nhiễm riêng lẻ với Al hoặc atrazine được thực hiện ở các nồng độ 5, 50 và 500 μg L-1, trong khi đó, quá trình phơi nhiễm kết hợp được tiến hành với Al tại nồng độ 50 μg L-1 và atrazine tại nồng độ 5 μg L-1 trong hai tuần. Kết quả cho thấy cả Al và atrazine ở nồng độ phơi nhiễm 500 μg L-1 kìm hãm mạnh mẽ sự phát triển và tốc độ sinh trưởng của bèo tấm. Ngược lại, sự kết hợp Al và atrazine dẫn kết tác động triệt tiêu trên bèo tấm. Theo sự hiểu biết của chúng tôi, đây là ghi nhận đầu tiên về những ảnh hưởng kết hợp của hai chất gây ô nhiễm này lên bèo tấm. Vì vậy, những kết quả này có thể hữu ích cho các nhà quản lý môi trường tại Việt Nam trong việc thiết lập và điều chỉnh các giá trị an toàn đối với Al và Atrazie trong môi trường nước tự nhiên về khía cạnh bảo vệ sức khỏe sinh thái.

Recently, the agricultural, industrial and mining activities have led to increase in contaminant emission. Trace metals or herbicides are among the pollutants to be concerned in the world. In this study we evaluated the effects of the herbicide atrazine (at the concentrations of 5, 50 and500 µg L-1) and its combination with copper (Cu, 50 µg L-1) and chromium (Cr, 50 µg L-1) on duckweed over the period of 10 days in the laboratory conditions. We found that 50 and 500 µg atrazine L-1 severely impacted on the growth or even caused the death of the plants, whereas there was no statistically significant difference in the duckweed growth rate between the 5 µg atrazine L-1 exposure and control. In the combined treatments (50 µg atrazine L-1 with Cu; with Cr or with both Cu and Cr), the plant growth rate of atrazine with either Cu or Cr was strongly reduced. However, the mixture of atrazine with Cu and Cr did not significantly decrease the development and growth rate of duckweed. Besides, atrazine and investigated heavy metals resulted in turning whiteof duckweek leaves that evidence ofthe chlorophyll degradation. Our results showed the negative influences of the herbicide atrazine and metals on development and morphology of duckweed. / Gần đây, những hoạt động nông nghiệp, công nghiệp và khai khoáng đã và đang dẫn đến sự gia tăng phát thải các chất gây ô nhiễm. Kim loại nặng hoặc thuốc diệt cỏ là những chất gây ô nhiễm đang được quan tâm trên thế giới. Trong nghiên cứu này, chúng tôi đánh giá ảnh hưởng của thuốc diệt cỏ atrazine (nồng độ 5, 50 và 500 µg/L) và sự kết hợp của chất này với đồng (Cu, 50 µg/L) và crom (Cr, 50 µg/L) lên bèo tấm trong thời gian 10 ngày trongđiều kiện phòng thí nghiệm. Chúng tôi nhận thấy atrazine tại nồng độ 50 và 500 µg/L đã gây nên những ảnh hưởng nghiêm trọng lên sự phát triển hay thậm chí làm cho bèo tấm bị chết, trong khi đó, không ghi nhận được bất kì sự khác biệt có ý nghĩa thống kê về tốc độ tăng trưởng của bèo tấm giữa lô thí nghiệm phơi nhiễm 5 µg atrazine / L và lô đối chứng. Trong những lô phơi nhiễm kết hợp (50 µg atrazine / L với Cu, với Cr hoặc với đồng thời Cu và Cr), tốc độ tăng trưởng của bèo tấm khi phơi nhiễm với atrazine và Cu hoặc Cr bị giảm mạnh, tuy nhiên, việc phơi nhiễm đồng thời atrazine với Cu và Cr đã không làm giảm đáng kể sự phát triển và tốc độ tăng trưởng của bèo tấm. Bên cạnh đó, atrazine và kim loại nặng đã làm cho màu của lá bèo tấm chuyển sang màu trắng, điều này chứng tỏ có sự suy giảm chlorophyll. Kết quả nghiên cứu này đã cho thấy những ảnh hưởng tiêu cựccủa thuốc diệt cỏ atrazine và kim loại lên sự phát triển và hình thái của bèo tấm.