Polychlorinated biphenyls (PCBs) are a family of chemical
compounds which do not exist in nature but which are manmade.
Commercial mixtures are clear, pale yellow liquids
manufactured by the replacement of hydrogen atoms on the
biphenyl molecule by chlorine. The reaction is controlled
according to the percentage replacement of hydrogen and
results in a product which contain chlorobiphenyls with one
or, more usually, several chlorine atoms attached to each
In the editors’ preface to the fourth edition it was noted that there was good news and there was bad news. It is the
same for this, the fifth edition. One suspects that this will always be the case.
The 2004 Nobel Prize for Peace has been awarded to Professor Dr. Wangari Maathai. Dr. Maathai’s award was
based on her efforts on behalf of conservation and women’s rights. These efforts were made at great personal risk.
In addition, the Kyoto Protocol has been ratified by the requisite number of countries.
THỦY SẢN CHÍNH SẢN XUẤT
Suất cơ bản trong các hệ thống thuỷ sản, giống như quá trình tương tự trong các môi trường trên cạn, cung cấp các cơ sở của mạng lưới thức ăn mà tất cả các cấp cao hơn của một hệ sinh thái phụ thuộc. Năng suất sinh học là sự gia tăng trong vật liệu hữu cơ trên một đơn vị diện tích, khối lượng với thời gian. Bổ sung các chất hữu cơ này là vật chất mà từ đó các cộng đồng thực vật và động vật khác nhau của một hệ sinh...
In the late 1980’s, a considerable amount of research addressing the
effects of acidic deposition was begun, much of it related to the Congressionally
mandated National Atmospheric Precipitation Assessment Program
(NAPAP). As a result of the 10-year NAPAP program, effects on human
health, materials, structures, visibility and terrestrial and aquatic ecosystems
were evaluated. As a result of NAPAP funded research, negative effects of
acidic deposition were documented on freshwater lakes in the Adirondacks
and on the red spruce of the Adirondacks and northern Appalachians....
The culture of striped catfish, Pangasianodon hypophthalmus (Sauvage), or “ca tra” in Vietnamese in
the Mekong Delta of Vietnam, can be considered as a unique aquatic farming system in many ways.
Production is the fastest growth recorded in any aquaculture sector, ever, based on a single species,
superseding the production per unit for any form of primary production. Stripped catfish aquaculture
now need to be improved in many aspects and environmental issues need to be paid more attention to
ensure the sustainable development.
Mining wastes can cause significant ecological destruction.
Often, solid mine wastes are dumped into streams,
destroying habitat and causing siltation and heavy metal
and other contamination. Even when such wastes are
stored out of water channels, trace materials can leach into
surface waters and infiltrate into local groundwater. Fine-
grained tailings can wash into local waterways and degrade
streams by covering and filling coarser-grained substrates.
Chapter 55 - Ecosystems, this chapter explain how the first and second laws of thermodynamics apply to ecosystems; define and compare gross primary production, net primary production, and standing crop; explain why energy flows but nutrients cycle within an ecosystem; explain what factors may limit primary production in aquatic ecosystems;...
Picocyanobacteria are a diverse and widespread
group of photosynthetic prokaryotes and belong to the main group of primary producers
(Castenholz & Waterbury. 1989; Rippka, 1988). Picoeukaryotes, meanwhile, are a diverse
group that is widely distributed in the marine environment, and they have a fundamental
role in aquatic ecosystems because of their high productivity. Like bacteria, marine viruses
are thought to play important roles in global and small-scale biogeochemical cycling.