Experts Warn of 'Dead Zone' in Chesapeake Bay
The Chesapeake Bay is the largest estuary in the United States.
To nature lovers, the bay is a national treasure. Its waters are perhaps best known for blue crabs and oysters.
For many years, the Chesapeake Bay area benefited from the Conowingo Dam on the Susquehanna River. When the dam opened nearly 100 years ago, it began controlling the power of water to create electricity for northern Maryland. It also trapped sediments before they reached the bay's waters.
While the old dam is still making electricity, it no longer helps the Chesapeake. It cannot. Behind its heavy walls lie 181 million metric tons of black muck – pollutants it has collected since the day the dam opened.
Now some people fear that the black muck may be a threat to the bay. Recent heavy rains have shown that muck runoff can move along the sides of the dam and pollute the water. The lack of agreement on the best way to stop the muck from polluting the Chesapeake, shows how fragile the area really is.
In 1983, the U.S. government launched a clean-up program that ended years of uncontrolled pollution. The cleanup has been considered a great success, with blue crabs and oyster populations expanding.
But experts say heavy rainfall is causing runoff pollutants from all over the area to reach the bay. They say this could lead to large dead zones in the waterway.
Operators of the Conowingo Dam want to extend its operating permit and keep the dam working for another 46 years. Many Maryland environmentalists say the black muck behind the dam is just one example of severe threats to the Bay. If a major storm enabled the black muck to flow freely into the bay, it would destroy the water's ecosystem.
"The situation behind the dam is a...time bomb," said Genevieve Croker. She is with the Clean Chesapeake Coalition, a group fighting to keep the bay clean.
Qian Zhang is a research scientist at the University of Maryland Center for Environmental Science. He agrees that the runoff is a problem, but says the muck is not the greatest threat to the bay.
Nutrient pollution, the chemical runoff from farms, is a much bigger worry, he believes. Most of the nutrient pollution comes from farms in the state of Pennsylvania, just north of Maryland. It flows down the Susquehanna River to the bay.
William Ball is a scientist with the Chesapeake Research Consortium. He said the best way to stop pollutants from entering the bay is to "better manage upstream sources."
Deborah Klenotic is a spokeswoman for Pennsylvania's Department of Environmental Protection. She says her state is working hard to meet its target for pollution reduction. The efforts, she said, "have never been stronger."
But this work may not be enough. Scientists are warning that there will be a 3 kilometer area of no oxygen in the Chesapeake Bay this year. That would make it one of the largest ‘dead zones' in nearly 20 years.
I'm Susan Shand.
1.heavy rainfall 暴雨
Failing a heavy rainfall soon, the drought will become serious.
2.dead zones 死亡地带
This vicious cycle gets worse as the spreading dead zones engulf the cod’s deep-water breeding grounds, he added.
3.time bomb 定时炸弹
A time bomb explode twenty minute after the plane take off.
4.no longer 不再
She no longer feared that they should misunderstand her.
5.Its waters are perhaps best known for blue crabs and oysters.
best known for 因...出名
Her later career was best known for her partnership with Rudolf Nureyev.
Italian cooking is best known for savoury dishes.
6.The cleanup has been considered a great success, with blue crabs and oyster populations expanding.
a great success 巨大的成功
This plan was a great success.
It was her first try at authorship and proved a great success.
对于热爱大自然的人来说，该海湾是他们的国家级宝藏 。这片水域可能最出名的是蓝蟹和牡蛎 。
多年来，切萨皮克湾地区受益于萨斯奎哈纳河上的科诺文戈大坝 。当大坝在大约100年前建成时，它开始控制水力，为马里兰州北部提供电力 。大坝还在沉积物到达这片水域前就将其拦截 。
虽然这堤水坝仍在发电，但已不再助力切萨皮克湾 。它已经“力不从心” 。在厚重的堤坝后，堆积了1.81亿吨的黑色淤泥——自大坝开放之日起，它就开始拦截这些污染物 。
现在有些人担心黑色淤泥可能对切萨皮克湾构成威胁 。最近的暴雨表明，淤泥径流会沿着大坝的两侧移动，污染水源 。无法就阻止淤泥污染切萨皮克的最佳途径达成一致，可以看出该地区有多脆弱 。
1983年，美国政府启动了一项清理计划，结束了多年来无法控制的污染问题 。随着蓝蟹和牡蛎数量的增加，清理工作被认为取得了巨大的成功 。
但专家表示，暴雨导致该地区的径流污染物从四面八方涌入海湾 。他们指出，这可能导致航道出现大面积的死亡地带 。
科诺文戈大坝的运营者希望延长其运营许可证，并让大坝再运行46年 。马里兰州许多环保人士表示，大坝背后的黑色淤泥只是海湾面临严重威胁的因素之一 。如果一场大风暴使黑淤泥肆意涌入海湾，将会破坏该水域的生态系统 。
“大坝背后的情况就像一颗……定时炸弹，”吉纳维芙·克罗克说道 。她是清理切萨皮克联盟的成员，该组织致力于维护海湾的清洁 。
张倩是马里兰大学环境科学中心研究员 。他对径流问题表示赞成，但指出淤泥并不是海湾最大的威胁 。
他认为，更令人担忧的是来自农场的化学物质污染 。大部分的营养污染来自宾夕法尼亚州位于马里兰州北部的农场 。营养污染沿着萨斯奎哈纳河流向切萨皮克海湾 。
威廉·鲍尔是切萨皮克研究协会的科学家 。他说，阻止污染物进入切萨皮克海湾的最好办法是“更严格地疏浚上游污染源” 。
Deborah Klenotic是宾夕法尼亚州环境保护部门的发言人 。她说，她所在的州正在努力实现减少污染的目标 。她说，这些努力“从未如此强大” 。
但这项工作可能还不够 。科学家警告说，切萨皮克湾今年将有3公里的区域缺氧 。这将使其成为近20年来最大的“死亡地带”之一 。