An overview on the organic pollution around the Qinghai-Tibet plateau: The thought-provoking situation.

The Qinghai-Tibet Plateau plays an important role in the ecological safety and human health of the surroundings due to its unique geographical position and function. Therefore, it is necessary to study the pollution status and potential risk in this area. This study summarizes the distribution of different organic pollutants in biota and environmental media of the Qinghai-Tibet Plateau. Moreover, it also pays attention to the potential health risks of these organic pollutants. Organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) were the most frequently detected in different matrices. In general, the carcinogenic risks of organic pollutants were ranked in the very-low to moderate range for both children and adults. The carcinogenic risks of organic pollutants in fish, food, and water for children were 1-2 times higher than those for adults, while risks of organic pollutants in soil/sediment and in air for children were generally 10.6-16.5 and 2.6-2.8 times higher than those for adults, respectively. The maximal hazard quotient for non-carcinogenic risk was 0.95 (potential risk for children posed by organic pollutants in yak milk of Ruoergai), almost reaching an unacceptable level. Therefore, the potential health risks could not be neglected, especially for children who were more likely to be affected by the pollutants.

Inorganic pollution around the Qinghai-Tibet Plateau: An overview of the current observations.

The Qinghai-Tibet Plateau is the highest geographical unit in the world. Thus, it serves an important role in evaluating long-term ecologic conditions and environmental status and changes over time. This study summarizes major and trace element concentrations in biota and in water and soil. It also pays attention to gaseous pollutant and particle concentrations in air around the Qinghai-Tibet Plateau. The degree of soil heavy metal contamination and the water heavy metal hazard index were respectively evaluated. The contamination degrees of two sampling areas around the Qinghai-Tibet Plateau reached extremely high levels with soil mCd (modified degree of contamination) values exceeding 20. Surprisingly, over 54% of sampling areas showed moderate or more serious soil contamination degree (mCd>1.5). Moreover, the hazard indexes of two important rivers were 1.56 and 7.59, reaching unacceptable level. The potential risk might be beyond our expectation. Therefore, it should be an urgent and top priority to identify and confirm possible pollution sources around the Qinghai-Tibet Plateau. Then, it is imperative to implement feasible and effective environmental quality control strategies.

Copper losses in surface runoff from flatwoods citrus production areas.

Crop production in areas with a high water table and poorly drained soils requires special drainage infrastructure to allow adequate rooting depth. In addition to facilitating drainage, this infrastructure also facilitates discharge of agrichemicals dissolved in drainage and runoff water. Copper export from bedded citrus production areas was evaluated using simulated rainfall events following application of copper. Copper concentrations in runoff water from individual water furrows ranged from 13 to 223 µg/L during the staged events, while copper loadings ranged from 32 to 302 g/water furrow.

Characterization of selected organo-nitrogen herbicides in South Florida canals: exposure and risk assessments.

Much uncertainty exists regarding the discharge characteristics of terrestrial-use herbicides into aquatic systems. This study evaluated the temporal distribution and concentrations of five commonly used herbicides (atrazine, bromacil, metolachlor, norflurazon, and simazine) in a typical South Florida watershed. Surface water samples were collected weekly over a 3-yr period from four canals and Ten Mile Creek. These systems received drainage water from a variety of land-uses, including residential, pastures, and citrus production. Herbicides were extracted and analyzed by GC-MS/SIM. Atrazine was most frequently detected (87% of samples) in the canal serving the residentially developed sub-basin, with median and maximum concentrations of 0.43 and 6.67 µg L(-1), respectively. Norflurazon was most frequently detected (90-95% of samples) in the systems serving agricultural production areas, with median and maximum concentrations ranging from 0.37-0.63 µg L(-1) and 1.98-6.97 µg L(-1), respectively. Bromacil was detected in 14-36% of samples with median and maximum concentrations ranging from 0.50-0.67 µg L(-1) and 2.31-4.96 µg L(-1), respectively. Metolachlor was detected in 1.8-10% of the samples, with median and maximum concentrations ranging from 0.16-0.2 µgL(-1) and 0.17-1.55 µg L(-1), respectively. Simazine was detected in 10-35% of the samples, with median and maximum concentrations ranging from 0.18-0.28 µg L(-1) and 0.37-1.35 µg L(-1), respectively. Bromacil+norflurazon was the most commonly detected (240 samples of 1060 total) binary combination of herbicides; whereas bromacil+norflurazon+simazine was the most frequently detected tertiary combination (58 samples). While detectable concentrations were present for significant periods of time, risks of acute toxicity were relatively low; affecting <1% of the potentially affected fraction (PAF) of plant species based on 90th centile exposure concentrations and 10th centile effects concentrations from species sensitivity distributions.

Nontarget deposition and losses of oxamyl in surface runoff from flatwoods citrus production areas.

Pesticide export from citrus production areas is a concern in the Indian River Lagoon drainage basin (Florida, USA). These studies evaluated nontarget deposition and losses of the insecticide oxamyl from typical flatwoods citrus production areas in South Florida. Deposition was estimated with the use of Teflon spray targets placed across nontarget water furrows during spray applications. After oxamyl applications, surface water runoff events were generated with an overhead irrigation system to simulate relatively low intensity rainfall. Results indicated that 0.3 to 20.0% of the applied active ingredient landed on nontarget water furrow surfaces and that the majority of oxamyl loss occurs in runoff events shortly following application. Mean concentrations were greater during the first runoff events, ranging from 34.7 to 47.0 microg/L. Total losses during the first several hours of each set of runoff events ranged from 0.1 to 3.8% of the total active ingredient applied. Similar losses can be expected when rainfall occurs shortly after application for other pesticides with similar chemical properties and application methods.