PROSES PENCEMARAN

Interaksi toksikan/pencemar dengan organisme dapat dinyatakan sebagai proses toksikokinetik, yaitu proses uptake toksikan/pencemar, dilanjutkan proses distribusi, metabolisme, dan penyimpanan dalam tubuh organisme serta ekskresi dari tubuh organisme tersebut. Proses tersebut menarik untuk dipelajari karena menentukan tingkat safety dan risk suatu toksikan/pencemar. Sedangkan interaksi polutan dengan sel, jaringan atau organ, dalam bentuk respon toksik dinyatakan sebagai toksikodinamik.

Secara umum, proses pencemaran dapat terjadi secara langsung maupun tidak langsung. Secara langsung yaitu bahan pencemar tersebut langsung berdampak meracuni sehingga mengganggu kesehatan manusia, hewan dan tumbuhan atau mengganggu keseimbangan ekologis baik air, udara maupun tanah. Proses tidak langsung, yaitu beberapa zat kimia bereaksi di udara, air maupun tanah, sehingga menyebabkan pencemaran.

TEKNIK PENGOLAHAN LIMBAH DENGAN WET SCRUBBING

Wet scrubber adalah peralatan pengendali pencemar udara yang berfungsi untuk mengumpulkan partikel-partikel halus yang terbawa dalam gas buang suatu proses dengan menggunakan titik-titik air.

Pada pengolahan ini cairan umumnya air digunakan untuk menangkap partikel debu atau untuk meningkatkan ukuran aerosol. Partikel halus berukuran 0,1 sampai 20 mikron dapat disisihkan secara efektif dari gas pembawa menggunakan wet collector. Nama lain dari filter basah adalah Scrubbers atau Wet Collectors. Prinsip kerja filter basah adalah membersihkan udara yang kotor dengan cara menyemprotkan air dari bagian atas alt, sedangkan udara yang kotor dari bagian bawah alat. Pada saat udara yang berdebu kontak dengan air, maka debu akan ikut disemprotkan air turun ke bawah. Venturi Scrubber menghilangkan partikel debu dan kontaminan gas tertentu dari gas aliran dengan memaksanya melewati aliran cair, menghasilkan cairan yang teratomisasi. Tinggi kecepatan diferensial di antara gas kotor dan cairan droplets menyebabkan partikel bertumbukan, kemudian akan berkelompok untuk membentuk tetesan yang lebih besar. Terakhir, tetesan cair tersebut dilemparkan pada dinding alat pemisah dan gas bersih pun dikeluarkan melalui puncak scrubber.

TEKNIK PENGOLAHAN LIMBAH B3 DENGAN FLOTASI

Flotation (flotasi) berasal dari kata float yang berarti mengapung atau mengambang. Flotasi dapat diartikan sebagai suatu pemisahan suatu zat dari zat lainnya pada suatu cairan/larutan berdasarkan perbedaan sifat permukaan dari zat yang akan dipisahkan, dimana zat yang bersifat hidrofilik tetap berada fasa air sedangkan zat yang bersifat hidrofobik akan terikat pada gelembung udara dan akan terbawa ke permukaan larutan dan membentuk buih yang kemudian dapat dipisahkan dari cairan tersebut. Secara umum flotation melibatkan 3 fase yaitu cair (sebagai media), padat (partikel yang terkandung dalam cairan) dan gas (gelembung udara).

ZAT-ZAT YANG DAPAT TERBAKAR DAN MELEDAK

Dalam pengertian luas zat yang dapat terbakar adalah sesuatu yang siap terbakar, sedangkan zat yang dapat meledak relative memerlukan rangsangan untuk terbakar. Sebelum mencoba mecermati definisi-definisi ini perlulah kiranya menetapkan beberapa terminology lain. Kebanyakan zat kimia yang cenderung terbakar tak sengaja adalah berupa cairan. Cairan menimbulkan uap, yang biasanya lebih pekat dari pada udara, dan karenanya bertendensi untuk terbakar. Tendensi dari pada suatu cairan untuk terbakar dapat diukur dengan sebuah pengujian dengan cairan dipanaskan dan secara priodik diekspose terhadap nyala api hingga campuran uap dan udara menyala pada permukaan cairan. Temperatur yang terjadi ini dinamakan titik nyala/flash point.

A NEW NATURE-HUMAN RELATIONSHIP

A critical environmental education consists of developing, not only among youth, but the population in general, the capacities to analyze educational propositions regarding the environment and dominant environmental discourses to decode hidden ideological orientations, the beliefs and interests that direct them, and which implicitly tend to reproduce the practices that are nevertheless the ones that would be necessary to shift to a different kind of relationship between nature and human beings. The reference to science and technological transfers as the main answer to defining and correcting the problem is insufficient to correct a situation that requires that humans also question the philosophic foundations, sociological, political, and economic dimensions of the regulation of climate. To reproduce the same economic logic is denounced by many as incapable of correcting the shameless exploitation of nature and human beings that are at the heart of the environmental crisis.

ENVIRONMENTAL EDUCATION AND SUSTAINABILITY

The fourth report of the Intergovernmental Panel on Climate Change (IPCC), published in February 2007, confirms the reality of global climate change. Some scientists have pointed to the uncertainties and the inevitable limits of the climatic modeling, and other researchers question the ascendancy of scientist’s analyses of the question in the public sphere. They assert that sociopolitical analyses should lead scholars to question the neo-liberal model of society, with its faith in technical progress, as well as the inequitable sharing of the wealth which ensues from it, according to Scott Lash, et al. The consensus of the IPCC experts has strengthened over the years, and concludes that the production of greenhouse gas of human origin is an important cause of global warming.

WHAT ARE SOME STRATEGIES TO REDUCE THE AMOUNT AND/OR TOXICITY OF CHEMICAL WASTE GENERATED IN THE LABORATORY?

All laboratories that use chemicals inevitably produce chemical waste that must be properly disposed of. It is crucial to minimize both the toxicity and the amount of chemical waste that is generated. A waste management and reduction policy that conforms to State and local regulations should be established by the school or school district. Several things that can be done to minimize hazards, waste generation, and control costs follow:

ENVIRONMENTAL CHEMMISTRY

Environmental chemistry is the study of the sources, reactions, transport, effects, and fates of chemical species in the water, air, terrestrial, and living environments and the effects of human activities thereon. Some idea of the complexity of environmental chemistry as a discipline may be realized by examining, which indicates the interchange of chemical species among various environmental spheres. Throughout an environmental system there are variations in temperature, mixing, intensity of solar radiation, input of materials, and various other factors that strongly influence chemical conditions and behavior. Because of its complexity, environmental chemistry must be approached with simplified models. This chapter presents an overview of environmental chemistry

TOXICOLOGICAL
CHEMISTRYAND  
BIOCHEMISTRY
THIRD EDITION

In order to understand toxicological chemistry, it is necessary to have some understanding of the environmental context in which toxicological chemical phenomena occur. This in turn requiresan understanding of the broader picture of environmental science and environmental chemistry,which are addressed in this chapter. Also needed is an understanding of how environmentalchemicals interact with organisms and their ecosystems, as addressed by the topic of ecotoxicology.

Environmental science can be defined as the study of the earth, air, water, and living environments, and the effects of technology thereon.1 To a significant degree, environmental science hasevolved from investigations of the ways by which, and places in which, living organisms carry outtheir life cycles. This is the discipline of natural history, which in recent times has evolved intoecology, the study of environmental factors that affect organisms and how organisms interact withthese factors and with each other.

TAR SANDS

Alberta’s tar sands (also known as oil sands) are the world’s third-largest reserves of recoverable crude oil.60 Though it is expensive to extract, this oil fetches a much lower price than other heavy oils due to the difculty in getting the landlocked tar sands to the United States and other potential markets. Thus, tar sands companies are desperate to promote new and expanded pipelines. The need for new pipeline capacity is particularly acute as companies ramp up production at projects that were started several years ago, while still planning new projects, such as Teck Resources’ massive Frontier Mine.