المعرفة

بقعة قمامة

بقعة القمامة هي دوامة من حبيبات نفايات بحرية تسببت فيها آثار تيارات محيطية وتلوث متزايد بالبلاستيك من البشر. إن هذه التجمعات من البلاستيك والنفايات الأخرى التي يتسبب فيها البشر مسؤولة عن مشاكل بيئية وإيكولوجية تؤثر على الحياة البحرية، وتلوث المحيطات بالمواد الكيميائية السامة، وتساهم في انبعاثات غازات الدفيئة. وبمجرد أن تنتقل النفايات البحرية إلى المياه، فإنها تصبح متحركة. ويمكن أن تتطاير النفايات بفعل الرياح، أو تتبع تدفق التيارات المحيطية، وغالبًا ما ينتهي بها الأمر في منتصف الدوامات المحيطية حيث تكون التيارات أضعف.

قمامة جرفتها المياه إلى الشاطئ في هاواي من بقعة قمامة الهادي الكبرى.

داخل بقع القمامة، لا تكون النفايات متماسكة، ورغم أن معظمها يقع بالقرب من سطح المحيط، إلا أنه يمكن العثور عليها على عمق يصل إلى أكثر من 30 مترًا تحت سطح الماء.[1] تحتوي البقع على بلاستيك ونفايات بأحجام مختلفة تتراوح من الميكروبلاستيك وحبيبات البلاستيك على نطاق صغير، إلى نفايات كبيرة مثل شبكات الصيد والسلع الاستهلاكية والأجهزة المفقودة بسبب الفيضانات وخسائر الشحن.

تزداد بقع القمامة بسبب فقدان البلاستيك واسع النطاق أنظمة جمع القمامة البشرية. وقد قدر برنامج الأمم المتحدة للبيئة أن "لكل ميل مربع من المحيط" يوجد حوالي "46.000 قطعة من البلاستيك".[2] أكبر 10 دول مصدر لتلوث البلاستيك في المحيطات على مستوى العالم هي، من الأكثر إلى الأقل، الصين، وإندونيسيا، والفلپين، وڤيتنام، وسريلانكا، وتايلند، ومصر، وماليزيا، ونيجيريا، وبنگلادش،[3] ومعظمها عن طريق أنهار يانگ‌تسى، السند، الأصفر، هاي، النيل، الگانج، اللؤلؤ، آمور، النيجر، ومكونگ، والتي تمثل "90 في المائة من إجمالي البلاستيك الذي يصل إلى محيطات العالم".[4][5] كانت آسيا المصدر الرئيسي للنفايات البلاستيكية التي أديرت بشكل سيئ، حيث بلغت حصة الصين وحدها 2.4 مليون طن متري.[6]

أشهر هذه البقع هي بقعة قمامة الهادي الكبرى، والتي تحتوي على أعلى كثافة من النفايات البحرية والبلاستيك. تحتوي بقعة قمامة الهادي على تراكمين كبيرين: بقعة القمامة الغربية وبقعة القمامة الشرقية، الأولى قبالة ساحل اليابان والثانية بين هاواي وكاليفورنيا. تحتوي بقع القمامة هذه على 90 مليون طن من النفايات.[1] تشمل البقع الأخرى المعروفة بقعة قمامة شمال الأطلسي بين أمريكا الشمالية وأفريقيا، وبقعة قمامة جنوب الأطلسي الواقعة بين شرق أمريكا الجنوبية وطرف أفريقيا، وبقعة قمامة جنوب الهادي الواقعة غرب أمريكا الجنوبية، وبقعة قمامة المحيط الهندي الواقعة شرق جنوب أفريقيا مدرجة حسب تناقص حجمها.[7]

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البقع المعروفة

 
Of the five gyres on this map, all have significant garbage patches.

In 2014, there were five areas across all the oceans where the majority of plastic concentrated.[8] Researchers collected a total of 3070 samples across the world to identify hot spots of surface level plastic pollution. The pattern of distribution closely mirrored models of oceanic currents with the North Pacific Gyre, or Great Pacific Garbage Patch, being the highest density of plastic accumulation. The other four garbage patches include the North Atlantic garbage patch between the North America and Africa, the South Atlantic garbage patch located between eastern South America and the tip of Africa, the South Pacific garbage patch located west of South America, and the Indian Ocean garbage patch found east of South Africa.[8]


الكبرى بالهادي

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جنوب الهادي

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المحيط الهندي

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شمال الأطلسي

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القضايا البيئية

المقالة الرئيسية: Marine debris and Marine plastic pollution

التحلل الضوئي للبلاستيك

انظر أيضاً: Photodegradation and Microplastics
 
Washed-up plastic waste on a beach in Singapore

The North Atlantic patch is one of several oceanic regions where researchers have studied the effects and impact of plastic photodegradation in the neustonic layer of water.[9] Unlike organic debris, which biodegrades, plastic disintegrates into ever smaller pieces while remaining a polymer (without changing chemically). This process continues down to the molecular level.[10] Some plastics decompose within a year of entering the water, releasing potentially toxic chemicals such as bisphenol A, PCBs and derivatives of polystyrene.[11]

As the plastic flotsam photodegrades into smaller and smaller pieces, it concentrates in the upper water column. As it disintegrates, the pieces become small enough to be ingested by aquatic organisms that reside near the ocean's surface. Plastic may become concentrated in neuston, thereby entering the food chain. Disintegration means that much of the plastic is too small to be seen. Moreover, plastic exposed to sunlight and in watering environments produce greenhouse gases, leading to further environmental impact.[12]

Effects on marine life

The 2017 United Nations Ocean Conference estimated that the oceans might contain more weight in plastics than fish by the year 2050.[13] Some long-lasting plastics end up in the stomachs of marine animals.[14][15][16] Plastic attracts seabirds and fish. When marine life consumes plastic allowing it to enter the food chain, this can lead to greater problems when species that have consumed plastic are then eaten by other predators.

Animals can also become trapped in plastic nets and rings, which can cause death. Plastic pollution affects at least 700 marine species, including sea turtles, seals, seabirds, fish, whales, and dolphins.[17] Cetaceans have been sighted within the patch, which poses entanglement and ingestion risks to animals using the Great Pacific garbage patch as a migration corridor or core habitat.[18]

Plastic consumption

 
An exhibit at the Mote Marine Laboratory that displays plastic bags in the ocean that look similar to jellyfish.

With the increased amount of plastic in the ocean, living organisms are now at a greater risk of harm from plastic consumption and entanglement. Approximately 23% of aquatic mammals, and 36% of seabirds have experienced the detriments of plastic presence in the ocean.[19] Since as much as 70% of the trash is estimated to be on the ocean floor, and microplastics are only millimeters wide, sealife at nearly every level of the food chain is affected.[20][21][22] Animals who feed off of the bottom of the ocean risk sweeping microplastics into their systems while gathering food.[23] Smaller marine life such as mussels and worms sometimes mistake plastic for their prey.[19][24]

Larger animals are also affected by plastic consumption because they feed on fish, and are indirectly consuming microplastics already trapped inside their prey.[23] Likewise, humans are also susceptible to microplastic consumption. People who eat seafood also eat some of the microplastics that were ingested by marine life. Oysters and clams are popular vehicles for human microplastic consumption.[23] Animals who are within the general vicinity of the water are also affected by the plastic in the ocean. Studies have shown 36% species of seabirds are consuming plastic because they mistake larger pieces of plastic for food.[19] Plastic can cause blockage of intestines as well as tearing of interior stomach and intestinal lining of marine life, ultimately leading to starvation and death.[19]

Entanglement

Not all marine life is affected by the consumption of plastic. Some instead find themselves tangled in larger pieces of garbage that cause just as much harm as the barely visible microplastics.[19] Trash that has the possibility of wrapping itself around a living organism may cause strangulation or drowning.[19] If the trash gets stuck around a ligament that is not vital for airflow, the ligament may grow with a malformation.[19] Plastic's existence in the ocean becomes cyclical because marine life that is killed by it ultimately decompose in the ocean, re-releasing the plastics into the ecosystem.[25][26]

Deposits on landmasses

Research in 2017[27] reported "the highest density of plastic rubbish anywhere in the world" on remote and uninhabited Henderson Island in South Pacific as a result of the South Pacific Gyre. The beaches contained an estimated 37.7 million items of debris together weighing 17.6 tonnes. In a study transect on North Beach, each day 17 to 268 new items washed up on a 10-metre section.[28][29][30]

المراجع

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