1. precipitation that has become acidic through the absorption of pollutants in the atmosphere, such as sulfur and nitrogen oxides - acid rain
The acid rains have become a big problem in the last couple of centuries. These rains can occur because of natural causes, but the real problem occurred after the Industrial Revolution started. Through the industry, the people started to propel enormous amounts of pollutants into the atmosphere, and that trend has been continuing and the amount of pollutants constantly increasing. These pollutants manage to merge with the clouds, and once the conditions are right for rain to occur, they mix with the drops, and fall together with it back on the ground. These rains are very dangerous for the health, especially for the respiratory system of the animals, destroys the plants, and causes increased erosion.
2. referring to a product or process that does not add more carbon dioxide to the atmosphere - carbon neutral
Carbon neutral is a term that is used for the products or process that do not contribute to releasing carbon dioxide into the atmosphere, but instead use other methods for their work. This is a relatively new thing in the global industry. It is a process that has been encouraged by most of the major economies and the most influential organizations in the world, with the main reason being the reduction of carbon dioxide emission into the atmosphere. The reason why the carbon dioxide emissions should be lowered and there's an ever growing concern about it is that this gas is the one most responsible for the Greenhouse effect, resulting in an increase of the global temperatures, climate changes, melting of the ice sheets, rise of the sea levels etc.
3. government-controlled farm - collective
The collective can simply be described as a farm that is controlled by the government. This type of farms were and still are typical for the socialist and communist countries, thus the countries that have command based economy. Basically, in this type of economies, the governments control everything in the production and selling of goods and services, including the production and selling of agricultural goods. The government owns the farmland, plans what should be produced, in what amount, and in what way. Unfortunately for the people, this type of managing the agriculture often created huge problems, with the lack of food occurring very often, and lot of people ending up suffering from malnutrition, or even starving to death as was the case in the Soviet Union and Maoist China.
4. a change causing an area to become more arid - desertification
The desertification is a process through which an area becomes more and more arid, gradually transforming the landscape into a desert. This process can happen naturally, because of the human activity, or a combination of both. The human activity though has increasing this process, mostly because lot of areas have been cleared from their vegetation, destroying the soil, and the changes in the climate because of the industry. Lot of effort have been put lately to stop this process and reverse, with the success being greater at some places, and lesser at other places. China managed to convert big portion of its northern deserts into green land, and it continues to do so, while in Africa there's collaboration between several nations that together make a continuous line of trees to stop the spreading of Sahara.
5. a process by which nutrients are dissolved in a body of water, increasing plant growth and resulting in reduced oxygen levels and fish populations - eutrophication
The eutrophication is a process through which a significantly larger amount of nutrients than what there is naturally come into the waters, resulting in much increased nutrients in it. While at start there is a boom in the growth of the plants, the situation quickly becomes very bad. As more and more plants and algae grow they cover the surface of the water body. By doing so they stop the sunlight, as well as depleting the oxygen in the water in meantime. The lack of sunlight and oxygen results in mass dying out of the aquatic life, soon turning the body of water very poor in marine life and a natural graveyard for the marine animals.